diff --git a/.github/workflows/doc-and-test.yml b/.github/workflows/doc-and-test.yml
index f4027c2..9fee30e 100644
--- a/.github/workflows/doc-and-test.yml
+++ b/.github/workflows/doc-and-test.yml
@@ -4,7 +4,7 @@ on: [push]
 
 env:
   CARGO_TERM_COLOR: always
-  rust_toolchain: nightly-2024-01-18
+  rust_toolchain: nightly-2025-02-18
 
 jobs:
   build-doc:
@@ -49,7 +49,10 @@ jobs:
       - name: Install QEMU
         run: |
           sudo apt-get update
-          sudo apt-get install ninja-build -y
+          sudo apt-get install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev \
+                               gawk build-essential bison flex texinfo gperf libtool patchutils bc \
+                               zlib1g-dev libexpat-dev pkg-config  libglib2.0-dev libpixman-1-dev libsdl2-dev libslirp-dev \
+                               python3 python3-pip ninja-build -y
           if [ ! -d qemu-7.0.0 ]; then
             wget https://download.qemu.org/qemu-7.0.0.tar.xz
             tar -xf qemu-7.0.0.tar.xz
@@ -65,4 +68,4 @@ jobs:
       - name: Run usertests
         run: cd os && make run TEST=1
         timeout-minutes: 10
-
+      
diff --git a/.gitignore b/.gitignore
index 45fffb0..7e20e83 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,14 +3,22 @@
 !.vscode/settings.json
 !.devcontainer/devcontainer.json
 
-**/target/
+.idea
 **/Cargo.lock
+**/target/
 
 os/src/link_app.S
 os/src/linker.ld
 os/last-*
+os/Cargo.lock
 os/.gdb_history
-os/virt.out
+user/build
+user/target/*
+user/.idea/*
+user/Cargo.lock
+easy-fs/Cargo.lock
+easy-fs/target/*
+easy-fs-fuse/Cargo.lock
+easy-fs-fuse/target/*
 tools/
 pushall.sh
-.vscode/*.log
diff --git a/README.md b/README.md
index 2df01b0..767cb14 100644
--- a/README.md
+++ b/README.md
@@ -50,7 +50,7 @@ Here we manually compile and install Qemu 7.0.0. For example, on Ubuntu 18.04:
 # install dependency packages
 $ sudo apt install autoconf automake autotools-dev curl libmpc-dev libmpfr-dev libgmp-dev \
               gawk build-essential bison flex texinfo gperf libtool patchutils bc \
-              zlib1g-dev libexpat-dev pkg-config  libglib2.0-dev libpixman-1-dev git tmux python3 python3-pip ninja-build
+              zlib1g-dev libexpat-dev pkg-config  libglib2.0-dev libpixman-1-dev git tmux python3 python3-pip
 # download Qemu source code
 $ wget https://download.qemu.org/qemu-7.0.0.tar.xz
 # extract to qemu-7.0.0/
@@ -64,7 +64,9 @@ $ make -j$(nproc)
 Then, add following contents to `~/.bashrc`(please adjust these paths according to your environment):
 
 ```
-export PATH=$PATH:/path/to/qemu-7.0.0/build
+export PATH=$PATH:/home/shinbokuow/Downloads/built/qemu-7.0.0
+export PATH=$PATH:/home/shinbokuow/Downloads/built/qemu-7.0.0/riscv64-softmmu
+export PATH=$PATH:/home/shinbokuow/Downloads/built/qemu-7.0.0/riscv64-linux-user
 ```
 
 Finally, update the current shell:
diff --git a/easy-fs-fuse/.gitignore b/easy-fs-fuse/.gitignore
new file mode 100644
index 0000000..79f5db6
--- /dev/null
+++ b/easy-fs-fuse/.gitignore
@@ -0,0 +1,3 @@
+.idea/
+target/
+Cargo.lock
diff --git a/easy-fs-fuse/Cargo.toml b/easy-fs-fuse/Cargo.toml
index d8d4e7f..5c5e68d 100644
--- a/easy-fs-fuse/Cargo.toml
+++ b/easy-fs-fuse/Cargo.toml
@@ -13,4 +13,4 @@ rand = "0.8.0"
 
 # [features]
 # board_qemu = []
-# board_k210 = []
+# board_k210 = []
\ No newline at end of file
diff --git a/easy-fs-fuse/src/main.rs b/easy-fs-fuse/src/main.rs
index dceec15..39b9eaf 100644
--- a/easy-fs-fuse/src/main.rs
+++ b/easy-fs-fuse/src/main.rs
@@ -23,10 +23,6 @@ impl BlockDevice for BlockFile {
             .expect("Error when seeking!");
         assert_eq!(file.write(buf).unwrap(), BLOCK_SZ, "Not a complete block!");
     }
-
-    fn handle_irq(&self) {
-        unimplemented!();
-    }
 }
 
 fn main() {
@@ -59,11 +55,11 @@ fn easy_fs_pack() -> std::io::Result<()> {
             .write(true)
             .create(true)
             .open(format!("{}{}", target_path, "fs.img"))?;
-        f.set_len(32 * 2048 * 512).unwrap();
+        f.set_len(16 * 2048 * 512).unwrap();
         f
     })));
-    // 32MiB, at most 4095 files
-    let efs = EasyFileSystem::create(block_file, 32 * 2048, 1);
+    // 16MiB, at most 4095 files
+    let efs = EasyFileSystem::create(block_file, 16 * 2048, 1);
     let root_inode = Arc::new(EasyFileSystem::root_inode(&efs));
     let apps: Vec<_> = read_dir(src_path)
         .unwrap()
@@ -153,3 +149,59 @@ fn efs_test() -> std::io::Result<()> {
 
     Ok(())
 }
+
+#[test]
+fn mac_test() -> std::io::Result<()> {
+    const BLOCK_SZ: usize = 512;
+
+    let block_file = Arc::new(BlockFile(Mutex::new({
+        let f = OpenOptions::new()
+            .read(true)
+            .write(true)
+            .create(true)
+            .open("target/fs_mac.img")?;
+        f.set_len(8192 * BLOCK_SZ).unwrap();
+        f
+    })));
+
+    EasyFileSystem::create(block_file.clone(), 4096, 1);
+    let efs = EasyFileSystem::open(block_file.clone());
+    let root_inode = EasyFileSystem::root_inode(&efs);
+
+    root_inode.create("root_file");
+    root_inode.create("public_file");
+
+    let secret_inode = root_inode.find("root_file").unwrap();
+    secret_inode.write_at(0, b"TOP SECRET: root only!");
+    let public_inode = root_inode.find("public_file").unwrap();
+    public_inode.write_at(0, b"This file is public.");
+
+    let check_permission = |user: &str, filename: &str| -> bool {
+        if filename == "root_file" && user != "root" {
+            false
+        } else {
+            true
+        }
+    };
+
+    let users = ["root", "nonroot"];
+    for user in users.iter() {
+        println!("{} task:", user);
+
+        for filename in ["root_file", "public_file"].iter() {
+            if check_permission(user, filename) {
+                let inode = root_inode.find(filename).unwrap();
+                let mut buf = [0u8; 128];
+                let len = inode.read_at(0, &mut buf);
+                let content = core::str::from_utf8(&buf[..len]).unwrap();
+                println!("{}: Opened successfully");
+            } else {
+                println!("{}: Permission denied");
+            }
+        }
+
+        println!();
+    }
+
+    Ok(())
+}
diff --git a/easy-fs/src/bitmap.rs b/easy-fs/src/bitmap.rs
index 2cea613..287e848 100644
--- a/easy-fs/src/bitmap.rs
+++ b/easy-fs/src/bitmap.rs
@@ -1,16 +1,16 @@
 use super::{get_block_cache, BlockDevice, BLOCK_SZ};
 use alloc::sync::Arc;
-
+/// A bitmap block
 type BitmapBlock = [u64; 64];
-
+/// Number of bits in a block
 const BLOCK_BITS: usize = BLOCK_SZ * 8;
-
+/// A bitmap
 pub struct Bitmap {
     start_block_id: usize,
     blocks: usize,
 }
 
-/// Return (block_pos, bits64_pos, inner_pos)
+/// Decompose bits into (block_pos, bits64_pos, inner_pos)
 fn decomposition(mut bit: usize) -> (usize, usize, usize) {
     let block_pos = bit / BLOCK_BITS;
     bit %= BLOCK_BITS;
@@ -18,13 +18,14 @@ fn decomposition(mut bit: usize) -> (usize, usize, usize) {
 }
 
 impl Bitmap {
+    /// A new bitmap from start block id and number of blocks
     pub fn new(start_block_id: usize, blocks: usize) -> Self {
         Self {
             start_block_id,
             blocks,
         }
     }
-
+    /// Allocate a new block from a block device
     pub fn alloc(&self, block_device: &Arc<dyn BlockDevice>) -> Option<usize> {
         for block_id in 0..self.blocks {
             let pos = get_block_cache(
@@ -52,7 +53,7 @@ impl Bitmap {
         }
         None
     }
-
+    /// Deallocate a block
     pub fn dealloc(&self, block_device: &Arc<dyn BlockDevice>, bit: usize) {
         let (block_pos, bits64_pos, inner_pos) = decomposition(bit);
         get_block_cache(block_pos + self.start_block_id, Arc::clone(block_device))
@@ -62,7 +63,7 @@ impl Bitmap {
                 bitmap_block[bits64_pos] -= 1u64 << inner_pos;
             });
     }
-
+    /// Get the max number of allocatable blocks
     pub fn maximum(&self) -> usize {
         self.blocks * BLOCK_BITS
     }
diff --git a/easy-fs/src/block_cache.rs b/easy-fs/src/block_cache.rs
index 1b3b969..786f9e0 100644
--- a/easy-fs/src/block_cache.rs
+++ b/easy-fs/src/block_cache.rs
@@ -1,15 +1,61 @@
 use super::{BlockDevice, BLOCK_SZ};
+use alloc::boxed::Box;
 use alloc::collections::VecDeque;
 use alloc::sync::Arc;
-use alloc::vec;
-use alloc::vec::Vec;
+use core::alloc::Layout;
+use core::mem::ManuallyDrop;
+use core::ptr::{addr_of, addr_of_mut};
+use core::slice;
 use lazy_static::*;
 use spin::Mutex;
 
+/// Use `ManuallyDrop` to ensure data is deallocated with an alignment of `BLOCK_SZ`
+struct CacheData(ManuallyDrop<Box<[u8; BLOCK_SZ]>>);
+
+impl CacheData {
+    pub fn new() -> Self {
+        let data = unsafe {
+            let raw = alloc::alloc::alloc(Self::layout());
+            Box::from_raw(raw as *mut [u8; BLOCK_SZ])
+        };
+        Self(ManuallyDrop::new(data))
+    }
+
+    fn layout() -> Layout {
+        Layout::from_size_align(BLOCK_SZ, BLOCK_SZ).unwrap()
+    }
+}
+
+impl Drop for CacheData {
+    fn drop(&mut self) {
+        let ptr = self.0.as_mut_ptr();
+        unsafe { alloc::alloc::dealloc(ptr, Self::layout()) };
+    }
+}
+
+impl AsRef<[u8]> for CacheData {
+    fn as_ref(&self) -> &[u8] {
+        let ptr = self.0.as_ptr() as *const u8;
+        unsafe { slice::from_raw_parts(ptr, BLOCK_SZ) }
+    }
+}
+
+impl AsMut<[u8]> for CacheData {
+    fn as_mut(&mut self) -> &mut [u8] {
+        let ptr = self.0.as_mut_ptr() as *mut u8;
+        unsafe { slice::from_raw_parts_mut(ptr, BLOCK_SZ) }
+    }
+}
+
+/// Cached block inside memory
 pub struct BlockCache {
-    cache: Vec<u8>,
+    /// cached block data
+    cache: CacheData,
+    /// underlying block id
     block_id: usize,
+    /// underlying block device
     block_device: Arc<dyn BlockDevice>,
+    /// whether the block is dirty
     modified: bool,
 }
 
@@ -17,8 +63,8 @@ impl BlockCache {
     /// Load a new BlockCache from disk.
     pub fn new(block_id: usize, block_device: Arc<dyn BlockDevice>) -> Self {
         // for alignment and move effciency
-        let mut cache = vec![0u8; BLOCK_SZ];
-        block_device.read_block(block_id, &mut cache);
+        let mut cache = CacheData::new();
+        block_device.read_block(block_id, cache.as_mut());
         Self {
             cache,
             block_id,
@@ -26,9 +72,13 @@ impl BlockCache {
             modified: false,
         }
     }
+    /// Get the address of an offset inside the cached block data
+    fn addr_of_offset(&self, offset: usize) -> *const u8 {
+        addr_of!(self.cache.as_ref()[offset])
+    }
 
-    fn addr_of_offset(&self, offset: usize) -> usize {
-        &self.cache[offset] as *const _ as usize
+    fn addr_of_offset_mut(&mut self, offset: usize) -> *mut u8 {
+        addr_of_mut!(self.cache.as_mut()[offset])
     }
 
     pub fn get_ref<T>(&self, offset: usize) -> &T
@@ -37,8 +87,8 @@ impl BlockCache {
     {
         let type_size = core::mem::size_of::<T>();
         assert!(offset + type_size <= BLOCK_SZ);
-        let addr = self.addr_of_offset(offset);
-        unsafe { &*(addr as *const T) }
+        let addr = self.addr_of_offset(offset) as *const T;
+        unsafe { &*addr }
     }
 
     pub fn get_mut<T>(&mut self, offset: usize) -> &mut T
@@ -48,8 +98,8 @@ impl BlockCache {
         let type_size = core::mem::size_of::<T>();
         assert!(offset + type_size <= BLOCK_SZ);
         self.modified = true;
-        let addr = self.addr_of_offset(offset);
-        unsafe { &mut *(addr as *mut T) }
+        let addr = self.addr_of_offset_mut(offset) as *mut T;
+        unsafe { &mut *addr }
     }
 
     pub fn read<T, V>(&self, offset: usize, f: impl FnOnce(&T) -> V) -> V {
@@ -63,7 +113,8 @@ impl BlockCache {
     pub fn sync(&mut self) {
         if self.modified {
             self.modified = false;
-            self.block_device.write_block(self.block_id, &self.cache);
+            self.block_device
+                .write_block(self.block_id, self.cache.as_ref());
         }
     }
 }
@@ -73,7 +124,7 @@ impl Drop for BlockCache {
         self.sync()
     }
 }
-
+/// Use a block cache of 16 blocks
 const BLOCK_CACHE_SIZE: usize = 16;
 
 pub struct BlockCacheManager {
@@ -121,10 +172,11 @@ impl BlockCacheManager {
 }
 
 lazy_static! {
+    /// The global block cache manager
     pub static ref BLOCK_CACHE_MANAGER: Mutex<BlockCacheManager> =
         Mutex::new(BlockCacheManager::new());
 }
-
+/// Get the block cache corresponding to the given block id and block device
 pub fn get_block_cache(
     block_id: usize,
     block_device: Arc<dyn BlockDevice>,
@@ -133,7 +185,7 @@ pub fn get_block_cache(
         .lock()
         .get_block_cache(block_id, block_device)
 }
-
+/// Sync all block cache to block device
 pub fn block_cache_sync_all() {
     let manager = BLOCK_CACHE_MANAGER.lock();
     for (_, cache) in manager.queue.iter() {
diff --git a/easy-fs/src/block_dev.rs b/easy-fs/src/block_dev.rs
index eb39fbd..555954a 100644
--- a/easy-fs/src/block_dev.rs
+++ b/easy-fs/src/block_dev.rs
@@ -1,7 +1,9 @@
 use core::any::Any;
-
+/// Trait for block devices
+/// which reads and writes data in the unit of blocks
 pub trait BlockDevice: Send + Sync + Any {
+    ///Read data form block to buffer
     fn read_block(&self, block_id: usize, buf: &mut [u8]);
+    ///Write data from buffer to block
     fn write_block(&self, block_id: usize, buf: &[u8]);
-    fn handle_irq(&self);
 }
diff --git a/easy-fs/src/efs.rs b/easy-fs/src/efs.rs
index 82e95ae..e28f6b2 100644
--- a/easy-fs/src/efs.rs
+++ b/easy-fs/src/efs.rs
@@ -5,18 +5,22 @@ use super::{
 use crate::BLOCK_SZ;
 use alloc::sync::Arc;
 use spin::Mutex;
-
+///An easy file system on block
 pub struct EasyFileSystem {
+    ///Real device
     pub block_device: Arc<dyn BlockDevice>,
+    ///Inode bitmap
     pub inode_bitmap: Bitmap,
+    ///Data bitmap
     pub data_bitmap: Bitmap,
     inode_area_start_block: u32,
     data_area_start_block: u32,
 }
 
 type DataBlock = [u8; BLOCK_SZ];
-
+/// An easy fs over a block device
 impl EasyFileSystem {
+    /// A data block of block size
     pub fn create(
         block_device: Arc<dyn BlockDevice>,
         total_blocks: u32,
@@ -32,7 +36,7 @@ impl EasyFileSystem {
         let data_bitmap_blocks = (data_total_blocks + 4096) / 4097;
         let data_area_blocks = data_total_blocks - data_bitmap_blocks;
         let data_bitmap = Bitmap::new(
-            (1 + inode_bitmap_blocks + inode_area_blocks) as usize,
+            (1 + inode_total_blocks) as usize,
             data_bitmap_blocks as usize,
         );
         let mut efs = Self {
@@ -77,7 +81,7 @@ impl EasyFileSystem {
         block_cache_sync_all();
         Arc::new(Mutex::new(efs))
     }
-
+    /// Open a block device as a filesystem
     pub fn open(block_device: Arc<dyn BlockDevice>) -> Arc<Mutex<Self>> {
         // read SuperBlock
         get_block_cache(0, Arc::clone(&block_device))
@@ -99,7 +103,7 @@ impl EasyFileSystem {
                 Arc::new(Mutex::new(efs))
             })
     }
-
+    /// Get the root inode of the filesystem
     pub fn root_inode(efs: &Arc<Mutex<Self>>) -> Inode {
         let block_device = Arc::clone(&efs.lock().block_device);
         // acquire efs lock temporarily
@@ -107,7 +111,7 @@ impl EasyFileSystem {
         // release efs lock
         Inode::new(block_id, block_offset, Arc::clone(efs), block_device)
     }
-
+    /// Get inode by id
     pub fn get_disk_inode_pos(&self, inode_id: u32) -> (u32, usize) {
         let inode_size = core::mem::size_of::<DiskInode>();
         let inodes_per_block = (BLOCK_SZ / inode_size) as u32;
@@ -117,20 +121,20 @@ impl EasyFileSystem {
             (inode_id % inodes_per_block) as usize * inode_size,
         )
     }
-
+    /// Get data block by id
     pub fn get_data_block_id(&self, data_block_id: u32) -> u32 {
         self.data_area_start_block + data_block_id
     }
-
+    /// Allocate a new inode
     pub fn alloc_inode(&mut self) -> u32 {
         self.inode_bitmap.alloc(&self.block_device).unwrap() as u32
     }
 
-    /// Return a block ID not ID in the data area.
+    /// Allocate a data block
     pub fn alloc_data(&mut self) -> u32 {
         self.data_bitmap.alloc(&self.block_device).unwrap() as u32 + self.data_area_start_block
     }
-
+    /// Deallocate a data block
     pub fn dealloc_data(&mut self, block_id: u32) {
         get_block_cache(block_id as usize, Arc::clone(&self.block_device))
             .lock()
diff --git a/easy-fs/src/layout.rs b/easy-fs/src/layout.rs
index 618484c..6daccaf 100644
--- a/easy-fs/src/layout.rs
+++ b/easy-fs/src/layout.rs
@@ -3,16 +3,24 @@ use alloc::sync::Arc;
 use alloc::vec::Vec;
 use core::fmt::{Debug, Formatter, Result};
 
+/// Magic number for sanity check
 const EFS_MAGIC: u32 = 0x3b800001;
+/// The max number of direct inodes
 const INODE_DIRECT_COUNT: usize = 28;
+/// The max length of inode name
 const NAME_LENGTH_LIMIT: usize = 27;
+/// The max number of indirect1 inodes
 const INODE_INDIRECT1_COUNT: usize = BLOCK_SZ / 4;
+/// The max number of indirect2 inodes
 const INODE_INDIRECT2_COUNT: usize = INODE_INDIRECT1_COUNT * INODE_INDIRECT1_COUNT;
+/// The upper bound of direct inode index
 const DIRECT_BOUND: usize = INODE_DIRECT_COUNT;
+/// The upper bound of indirect1 inode index
 const INDIRECT1_BOUND: usize = DIRECT_BOUND + INODE_INDIRECT1_COUNT;
+/// The upper bound of indirect2 inode indexs
 #[allow(unused)]
 const INDIRECT2_BOUND: usize = INDIRECT1_BOUND + INODE_INDIRECT2_COUNT;
-
+/// Super block of a filesystem
 #[repr(C)]
 pub struct SuperBlock {
     magic: u32,
@@ -36,6 +44,7 @@ impl Debug for SuperBlock {
 }
 
 impl SuperBlock {
+    /// Initialize a super block
     pub fn initialize(
         &mut self,
         total_blocks: u32,
@@ -53,20 +62,23 @@ impl SuperBlock {
             data_area_blocks,
         }
     }
+    /// Check if a super block is valid using efs magic
     pub fn is_valid(&self) -> bool {
         self.magic == EFS_MAGIC
     }
 }
-
+/// Type of a disk inode
 #[derive(PartialEq)]
 pub enum DiskInodeType {
     File,
     Directory,
 }
 
+/// A indirect block
 type IndirectBlock = [u32; BLOCK_SZ / 4];
+/// A data block
 type DataBlock = [u8; BLOCK_SZ];
-
+/// A disk inode
 #[repr(C)]
 pub struct DiskInode {
     pub size: u32,
@@ -77,7 +89,8 @@ pub struct DiskInode {
 }
 
 impl DiskInode {
-    /// indirect1 and indirect2 block are allocated only when they are needed.
+    /// Initialize a disk inode, as well as all direct inodes under it
+    /// indirect1 and indirect2 block are allocated only when they are needed
     pub fn initialize(&mut self, type_: DiskInodeType) {
         self.size = 0;
         self.direct.iter_mut().for_each(|v| *v = 0);
@@ -85,9 +98,11 @@ impl DiskInode {
         self.indirect2 = 0;
         self.type_ = type_;
     }
+    /// Whether this inode is a directory
     pub fn is_dir(&self) -> bool {
         self.type_ == DiskInodeType::Directory
     }
+    /// Whether this inode is a file
     #[allow(unused)]
     pub fn is_file(&self) -> bool {
         self.type_ == DiskInodeType::File
@@ -116,10 +131,12 @@ impl DiskInode {
         }
         total as u32
     }
+    /// Get the number of data blocks that have to be allocated given the new size of data
     pub fn blocks_num_needed(&self, new_size: u32) -> u32 {
         assert!(new_size >= self.size);
         Self::total_blocks(new_size) - Self::total_blocks(self.size)
     }
+    /// Get id of block given inner id
     pub fn get_block_id(&self, inner_id: u32, block_device: &Arc<dyn BlockDevice>) -> u32 {
         let inner_id = inner_id as usize;
         if inner_id < INODE_DIRECT_COUNT {
@@ -144,6 +161,7 @@ impl DiskInode {
                 })
         }
     }
+    /// Inncrease the size of current disk inode
     pub fn increase_size(
         &mut self,
         new_size: u32,
@@ -218,7 +236,6 @@ impl DiskInode {
     }
 
     /// Clear size to zero and return blocks that should be deallocated.
-    ///
     /// We will clear the block contents to zero later.
     pub fn clear_size(&mut self, block_device: &Arc<dyn BlockDevice>) -> Vec<u32> {
         let mut v: Vec<u32> = Vec::new();
@@ -291,6 +308,7 @@ impl DiskInode {
         self.indirect2 = 0;
         v
     }
+    /// Read data from current disk inode
     pub fn read_at(
         &self,
         offset: usize,
@@ -330,7 +348,8 @@ impl DiskInode {
         }
         read_size
     }
-    /// File size must be adjusted before.
+    /// Write data into current disk inode
+    /// size must be adjusted properly beforehand
     pub fn write_at(
         &mut self,
         offset: usize,
@@ -369,22 +388,24 @@ impl DiskInode {
         write_size
     }
 }
-
+/// A directory entry
 #[repr(C)]
 pub struct DirEntry {
     name: [u8; NAME_LENGTH_LIMIT + 1],
     inode_number: u32,
 }
-
+/// Size of a directory entry
 pub const DIRENT_SZ: usize = 32;
 
 impl DirEntry {
+    /// Create an empty directory entry
     pub fn empty() -> Self {
         Self {
             name: [0u8; NAME_LENGTH_LIMIT + 1],
             inode_number: 0,
         }
     }
+    /// Crate a directory entry from name and inode number
     pub fn new(name: &str, inode_number: u32) -> Self {
         let mut bytes = [0u8; NAME_LENGTH_LIMIT + 1];
         bytes[..name.len()].copy_from_slice(name.as_bytes());
@@ -393,16 +414,20 @@ impl DirEntry {
             inode_number,
         }
     }
+    /// Serialize into bytes
     pub fn as_bytes(&self) -> &[u8] {
         unsafe { core::slice::from_raw_parts(self as *const _ as usize as *const u8, DIRENT_SZ) }
     }
+    /// Serialize into mutable bytes
     pub fn as_bytes_mut(&mut self) -> &mut [u8] {
         unsafe { core::slice::from_raw_parts_mut(self as *mut _ as usize as *mut u8, DIRENT_SZ) }
     }
+    /// Get name of the entry
     pub fn name(&self) -> &str {
         let len = (0usize..).find(|i| self.name[*i] == 0).unwrap();
         core::str::from_utf8(&self.name[..len]).unwrap()
     }
+    /// Get inode number of the entry
     pub fn inode_number(&self) -> u32 {
         self.inode_number
     }
diff --git a/easy-fs/src/lib.rs b/easy-fs/src/lib.rs
index fa36e6b..822c237 100644
--- a/easy-fs/src/lib.rs
+++ b/easy-fs/src/lib.rs
@@ -1,14 +1,14 @@
+//!An easy file system isolated from the kernel
 #![no_std]
-
+#![deny(missing_docs)]
 extern crate alloc;
-
 mod bitmap;
 mod block_cache;
 mod block_dev;
 mod efs;
 mod layout;
 mod vfs;
-
+/// Use a block size of 512 bytes
 pub const BLOCK_SZ: usize = 512;
 use bitmap::Bitmap;
 use block_cache::{block_cache_sync_all, get_block_cache};
diff --git a/easy-fs/src/vfs.rs b/easy-fs/src/vfs.rs
index 7290fa4..9f90c50 100644
--- a/easy-fs/src/vfs.rs
+++ b/easy-fs/src/vfs.rs
@@ -6,7 +6,7 @@ use alloc::string::String;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
 use spin::{Mutex, MutexGuard};
-
+/// Virtual filesystem layer over easy-fs
 pub struct Inode {
     block_id: usize,
     block_offset: usize,
@@ -15,7 +15,7 @@ pub struct Inode {
 }
 
 impl Inode {
-    /// We should not acquire efs lock here.
+    /// Create a vfs inode
     pub fn new(
         block_id: u32,
         block_offset: usize,
@@ -29,19 +29,19 @@ impl Inode {
             block_device,
         }
     }
-
+    /// Call a function over a disk inode to read it
     fn read_disk_inode<V>(&self, f: impl FnOnce(&DiskInode) -> V) -> V {
         get_block_cache(self.block_id, Arc::clone(&self.block_device))
             .lock()
             .read(self.block_offset, f)
     }
-
+    /// Call a function over a disk inode to modify it
     fn modify_disk_inode<V>(&self, f: impl FnOnce(&mut DiskInode) -> V) -> V {
         get_block_cache(self.block_id, Arc::clone(&self.block_device))
             .lock()
             .modify(self.block_offset, f)
     }
-
+    /// Find inode under a disk inode by name
     fn find_inode_id(&self, name: &str, disk_inode: &DiskInode) -> Option<u32> {
         // assert it is a directory
         assert!(disk_inode.is_dir());
@@ -58,7 +58,7 @@ impl Inode {
         }
         None
     }
-
+    /// Find inode under current inode by name
     pub fn find(&self, name: &str) -> Option<Arc<Inode>> {
         let fs = self.fs.lock();
         self.read_disk_inode(|disk_inode| {
@@ -73,7 +73,7 @@ impl Inode {
             })
         })
     }
-
+    /// Increase the size of a disk inode
     fn increase_size(
         &self,
         new_size: u32,
@@ -90,16 +90,16 @@ impl Inode {
         }
         disk_inode.increase_size(new_size, v, &self.block_device);
     }
-
+    /// Create inode under current inode by name
     pub fn create(&self, name: &str) -> Option<Arc<Inode>> {
         let mut fs = self.fs.lock();
-        let op = |root_inode: &mut DiskInode| {
+        let op = |root_inode: &DiskInode| {
             // assert it is a directory
             assert!(root_inode.is_dir());
             // has the file been created?
             self.find_inode_id(name, root_inode)
         };
-        if self.modify_disk_inode(op).is_some() {
+        if self.read_disk_inode(op).is_some() {
             return None;
         }
         // create a new file
@@ -138,7 +138,7 @@ impl Inode {
         )))
         // release efs lock automatically by compiler
     }
-
+    /// List inodes under current inode
     pub fn ls(&self) -> Vec<String> {
         let _fs = self.fs.lock();
         self.read_disk_inode(|disk_inode| {
@@ -155,12 +155,12 @@ impl Inode {
             v
         })
     }
-
+    /// Read data from current inode
     pub fn read_at(&self, offset: usize, buf: &mut [u8]) -> usize {
         let _fs = self.fs.lock();
         self.read_disk_inode(|disk_inode| disk_inode.read_at(offset, buf, &self.block_device))
     }
-
+    /// Write data to current inode
     pub fn write_at(&self, offset: usize, buf: &[u8]) -> usize {
         let mut fs = self.fs.lock();
         let size = self.modify_disk_inode(|disk_inode| {
@@ -170,7 +170,7 @@ impl Inode {
         block_cache_sync_all();
         size
     }
-
+    /// Clear the data in current inode
     pub fn clear(&self) {
         let mut fs = self.fs.lock();
         self.modify_disk_inode(|disk_inode| {
diff --git a/figures/logo.png b/figures/logo.png
deleted file mode 100644
index 84af081..0000000
Binary files a/figures/logo.png and /dev/null differ
diff --git a/os/Cargo.toml b/os/Cargo.toml
index fde4b6c..d621557 100644
--- a/os/Cargo.toml
+++ b/os/Cargo.toml
@@ -2,7 +2,7 @@
 name = "os"
 version = "0.1.0"
 authors = ["Yifan Wu <shinbokuow@163.com>"]
-edition = "2021"
+edition = "2024"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
@@ -12,12 +12,8 @@ lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
 buddy_system_allocator = "0.6"
 bitflags = "1.2.1"
 xmas-elf = "0.7.0"
-volatile = "0.3"
 virtio-drivers = { git = "https://github.com/rcore-os/virtio-drivers", rev = "4ee80e5" }
-lose-net-stack = { git = "https://github.com/yfblock/lose-net-stack", rev = "db42380" }
 easy-fs = { path = "../easy-fs" }
-embedded-graphics = "0.7.1"
-tinybmp = "0.3.1"
 log = "0.4"
 sbi-rt = { version = "0.0.2", features = ["legacy"] }
 
diff --git a/os/Makefile b/os/Makefile
index b0c3463..ff109f0 100644
--- a/os/Makefile
+++ b/os/Makefile
@@ -12,12 +12,6 @@ BOARD := qemu
 SBI ?= rustsbi
 BOOTLOADER := ../bootloader/$(SBI)-$(BOARD).bin
 
-# GUI
-GUI ?= off
-ifeq ($(GUI), off)
-	GUI_OPTION := -display none
-endif
-
 # Building mode argument
 ifeq ($(MODE), release)
 	MODE_ARG := --release
@@ -68,27 +62,17 @@ disasm: kernel
 
 disasm-vim: kernel
 	@$(OBJDUMP) $(DISASM) $(KERNEL_ELF) > $(DISASM_TMP)
-	@nvim $(DISASM_TMP)
+	@vim $(DISASM_TMP)
 	@rm $(DISASM_TMP)
 
 run: run-inner
 
 QEMU_ARGS := -machine virt \
+			 -nographic \
 			 -bios $(BOOTLOADER) \
-			 -serial stdio \
-			 $(GUI_OPTION) \
 			 -device loader,file=$(KERNEL_BIN),addr=$(KERNEL_ENTRY_PA) \
 			 -drive file=$(FS_IMG),if=none,format=raw,id=x0 \
-			 -device virtio-blk-device,drive=x0 \
-			 -device virtio-gpu-device \
-			 -device virtio-keyboard-device \
-			 -device virtio-mouse-device \
-			 -device virtio-net-device,netdev=net0 \
-			 -netdev user,id=net0,hostfwd=udp::6200-:2000,hostfwd=tcp::6201-:80
-
-fdt:
-	@qemu-system-riscv64 -M 128m -machine virt,dumpdtb=virt.out
-	fdtdump virt.out
+			 -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0
 
 QEMU_NAME := qemu-system-riscv64
 qemu-version-check:
@@ -109,4 +93,4 @@ gdbserver: qemu-version-check build
 gdbclient:
 	@riscv64-unknown-elf-gdb -ex 'file $(KERNEL_ELF)' -ex 'set arch riscv:rv64' -ex 'target remote localhost:1234'
 
-.PHONY: build env kernel clean disasm disasm-vim run-inner fs-img gdbserver gdbclient fdt qemu-version-check
+.PHONY: build env kernel clean disasm disasm-vim run-inner fs-img gdbserver gdbclient qemu-version-check
diff --git a/os/scripts/qemu-ver-check.sh b/os/scripts/qemu-ver-check.sh
old mode 100644
new mode 100755
index 8c20456..40ef766
--- a/os/scripts/qemu-ver-check.sh
+++ b/os/scripts/qemu-ver-check.sh
@@ -13,7 +13,7 @@ then
     exit 1
 else
     QEMU_VERSION=$($1 --version|head -n 1|awk '{print $4}')
-    MAJOR_VERSION=$(echo $QEMU_VERSION|cut -c1-1)
+    MAJOR_VERSION=$(echo $QEMU_VERSION | awk -F '.' '{print $1}')
     if [ $MAJOR_VERSION -lt $MINIMUM_MAJOR_VERSION ]
     then
         echo "${RED}Error: Required major version of QEMU is ${MINIMUM_MAJOR_VERSION}, " \
diff --git a/os/src/assert/desktop.bmp b/os/src/assert/desktop.bmp
deleted file mode 100644
index a754f7a..0000000
Binary files a/os/src/assert/desktop.bmp and /dev/null differ
diff --git a/os/src/assert/file.bmp b/os/src/assert/file.bmp
deleted file mode 100644
index 4a4e83b..0000000
Binary files a/os/src/assert/file.bmp and /dev/null differ
diff --git a/os/src/assert/folder.bmp b/os/src/assert/folder.bmp
deleted file mode 100644
index c8384cb..0000000
Binary files a/os/src/assert/folder.bmp and /dev/null differ
diff --git a/os/src/assert/mouse.bmp b/os/src/assert/mouse.bmp
deleted file mode 100644
index 22a4613..0000000
Binary files a/os/src/assert/mouse.bmp and /dev/null differ
diff --git a/os/src/boards/qemu.rs b/os/src/boards/qemu.rs
index 5daf541..275de4d 100644
--- a/os/src/boards/qemu.rs
+++ b/os/src/boards/qemu.rs
@@ -3,53 +3,7 @@ pub const MEMORY_END: usize = 0x8800_0000;
 
 pub const MMIO: &[(usize, usize)] = &[
     (0x0010_0000, 0x00_2000), // VIRT_TEST/RTC  in virt machine
-    (0x2000000, 0x10000),     // core local interrupter (CLINT)
-    (0xc000000, 0x210000),    // VIRT_PLIC in virt machine
-    (0x10000000, 0x9000),     // VIRT_UART0 with GPU  in virt machine
+    (0x1000_1000, 0x00_1000), // Virtio Block in virt machine
 ];
 
 pub type BlockDeviceImpl = crate::drivers::block::VirtIOBlock;
-pub type CharDeviceImpl = crate::drivers::chardev::NS16550a<VIRT_UART>;
-
-pub const VIRT_PLIC: usize = 0xC00_0000;
-pub const VIRT_UART: usize = 0x1000_0000;
-#[allow(unused)]
-pub const VIRTGPU_XRES: u32 = 1280;
-#[allow(unused)]
-pub const VIRTGPU_YRES: u32 = 800;
-
-use crate::drivers::block::BLOCK_DEVICE;
-use crate::drivers::chardev::{CharDevice, UART};
-use crate::drivers::plic::{IntrTargetPriority, PLIC};
-use crate::drivers::{KEYBOARD_DEVICE, MOUSE_DEVICE};
-
-pub fn device_init() {
-    use riscv::register::sie;
-    let mut plic = unsafe { PLIC::new(VIRT_PLIC) };
-    let hart_id: usize = 0;
-    let supervisor = IntrTargetPriority::Supervisor;
-    let machine = IntrTargetPriority::Machine;
-    plic.set_threshold(hart_id, supervisor, 0);
-    plic.set_threshold(hart_id, machine, 1);
-    //irq nums: 5 keyboard, 6 mouse, 8 block, 10 uart
-    for intr_src_id in [5usize, 6, 8, 10] {
-        plic.enable(hart_id, supervisor, intr_src_id);
-        plic.set_priority(intr_src_id, 1);
-    }
-    unsafe {
-        sie::set_sext();
-    }
-}
-
-pub fn irq_handler() {
-    let mut plic = unsafe { PLIC::new(VIRT_PLIC) };
-    let intr_src_id = plic.claim(0, IntrTargetPriority::Supervisor);
-    match intr_src_id {
-        5 => KEYBOARD_DEVICE.handle_irq(),
-        6 => MOUSE_DEVICE.handle_irq(),
-        8 => BLOCK_DEVICE.handle_irq(),
-        10 => UART.handle_irq(),
-        _ => panic!("unsupported IRQ {}", intr_src_id),
-    }
-    plic.complete(0, IntrTargetPriority::Supervisor, intr_src_id);
-}
diff --git a/os/src/config.rs b/os/src/config.rs
index d9b9b71..f9a2b7f 100644
--- a/os/src/config.rs
+++ b/os/src/config.rs
@@ -1,12 +1,14 @@
+//! Constants used in rCore
 #[allow(unused)]
 
 pub const USER_STACK_SIZE: usize = 4096 * 2;
 pub const KERNEL_STACK_SIZE: usize = 4096 * 2;
-pub const KERNEL_HEAP_SIZE: usize = 0x100_0000;
+pub const KERNEL_HEAP_SIZE: usize = 0x20_0000;
+
 pub const PAGE_SIZE: usize = 0x1000;
 pub const PAGE_SIZE_BITS: usize = 0xc;
 
 pub const TRAMPOLINE: usize = usize::MAX - PAGE_SIZE + 1;
-pub const TRAP_CONTEXT_BASE: usize = TRAMPOLINE - PAGE_SIZE;
+pub const TRAP_CONTEXT: usize = TRAMPOLINE - PAGE_SIZE;
 
 pub use crate::board::{CLOCK_FREQ, MEMORY_END, MMIO};
diff --git a/os/src/console.rs b/os/src/console.rs
index 085637b..5435310 100644
--- a/os/src/console.rs
+++ b/os/src/console.rs
@@ -1,5 +1,5 @@
-use crate::drivers::chardev::CharDevice;
-use crate::drivers::chardev::UART;
+//! SBI console driver, for text output
+use crate::sbi::console_putchar;
 use core::fmt::{self, Write};
 
 struct Stdout;
@@ -7,7 +7,7 @@ struct Stdout;
 impl Write for Stdout {
     fn write_str(&mut self, s: &str) -> fmt::Result {
         for c in s.chars() {
-            UART.write(c as u8);
+            console_putchar(c as usize);
         }
         Ok(())
     }
@@ -18,15 +18,17 @@ pub fn print(args: fmt::Arguments) {
 }
 
 #[macro_export]
+/// print string macro
 macro_rules! print {
     ($fmt: literal $(, $($arg: tt)+)?) => {
-        $crate::console::print(format_args!($fmt $(, $($arg)+)?))
+        $crate::console::print(format_args!($fmt $(, $($arg)+)?));
     }
 }
 
 #[macro_export]
+/// println string macro
 macro_rules! println {
     ($fmt: literal $(, $($arg: tt)+)?) => {
-        $crate::console::print(format_args!(concat!($fmt, "\n") $(, $($arg)+)?))
+        $crate::console::print(format_args!(concat!($fmt, "\n") $(, $($arg)+)?));
     }
 }
diff --git a/os/src/drivers/block/virtio_blk.rs b/os/src/drivers/block/virtio_blk.rs
index fb89084..5097831 100644
--- a/os/src/drivers/block/virtio_blk.rs
+++ b/os/src/drivers/block/virtio_blk.rs
@@ -1,87 +1,83 @@
 use super::BlockDevice;
-use crate::drivers::bus::virtio::VirtioHal;
-use crate::sync::{Condvar, UPIntrFreeCell};
-use crate::task::schedule;
-use crate::DEV_NON_BLOCKING_ACCESS;
-use alloc::collections::BTreeMap;
-use virtio_drivers::{BlkResp, RespStatus, VirtIOBlk, VirtIOHeader};
+use crate::mm::{
+    FrameTracker, PageTable, PhysAddr, PhysPageNum, StepByOne, VirtAddr, frame_alloc,
+    frame_dealloc, kernel_token,
+};
+use crate::sync::UPSafeCell;
+use alloc::vec::Vec;
+use lazy_static::*;
+use virtio_drivers::{Hal, VirtIOBlk, VirtIOHeader};
 
 #[allow(unused)]
-const VIRTIO0: usize = 0x10008000;
+const VIRTIO0: usize = 0x10001000;
 
-pub struct VirtIOBlock {
-    virtio_blk: UPIntrFreeCell<VirtIOBlk<'static, VirtioHal>>,
-    condvars: BTreeMap<u16, Condvar>,
+pub struct VirtIOBlock(UPSafeCell<VirtIOBlk<'static, VirtioHal>>);
+
+lazy_static! {
+    static ref QUEUE_FRAMES: UPSafeCell<Vec<FrameTracker>> = unsafe { UPSafeCell::new(Vec::new()) };
 }
 
 impl BlockDevice for VirtIOBlock {
     fn read_block(&self, block_id: usize, buf: &mut [u8]) {
-        let nb = *DEV_NON_BLOCKING_ACCESS.exclusive_access();
-        if nb {
-            let mut resp = BlkResp::default();
-            let task_cx_ptr = self.virtio_blk.exclusive_session(|blk| {
-                let token = unsafe { blk.read_block_nb(block_id, buf, &mut resp).unwrap() };
-                self.condvars.get(&token).unwrap().wait_no_sched()
-            });
-            schedule(task_cx_ptr);
-            assert_eq!(
-                resp.status(),
-                RespStatus::Ok,
-                "Error when reading VirtIOBlk"
-            );
-        } else {
-            self.virtio_blk
-                .exclusive_access()
-                .read_block(block_id, buf)
-                .expect("Error when reading VirtIOBlk");
-        }
+        self.0
+            .exclusive_access()
+            .read_block(block_id, buf)
+            .expect("Error when reading VirtIOBlk");
     }
     fn write_block(&self, block_id: usize, buf: &[u8]) {
-        let nb = *DEV_NON_BLOCKING_ACCESS.exclusive_access();
-        if nb {
-            let mut resp = BlkResp::default();
-            let task_cx_ptr = self.virtio_blk.exclusive_session(|blk| {
-                let token = unsafe { blk.write_block_nb(block_id, buf, &mut resp).unwrap() };
-                self.condvars.get(&token).unwrap().wait_no_sched()
-            });
-            schedule(task_cx_ptr);
-            assert_eq!(
-                resp.status(),
-                RespStatus::Ok,
-                "Error when writing VirtIOBlk"
-            );
-        } else {
-            self.virtio_blk
-                .exclusive_access()
-                .write_block(block_id, buf)
-                .expect("Error when writing VirtIOBlk");
-        }
-    }
-    fn handle_irq(&self) {
-        self.virtio_blk.exclusive_session(|blk| {
-            while let Ok(token) = blk.pop_used() {
-                self.condvars.get(&token).unwrap().signal();
-            }
-        });
+        self.0
+            .exclusive_access()
+            .write_block(block_id, buf)
+            .expect("Error when writing VirtIOBlk");
     }
 }
 
 impl VirtIOBlock {
+    #[allow(unused)]
     pub fn new() -> Self {
-        let virtio_blk = unsafe {
-            UPIntrFreeCell::new(
+        unsafe {
+            Self(UPSafeCell::new(
                 VirtIOBlk::<VirtioHal>::new(&mut *(VIRTIO0 as *mut VirtIOHeader)).unwrap(),
-            )
-        };
-        let mut condvars = BTreeMap::new();
-        let channels = virtio_blk.exclusive_access().virt_queue_size();
-        for i in 0..channels {
-            let condvar = Condvar::new();
-            condvars.insert(i, condvar);
-        }
-        Self {
-            virtio_blk,
-            condvars,
+            ))
         }
     }
 }
+
+pub struct VirtioHal;
+
+impl Hal for VirtioHal {
+    fn dma_alloc(pages: usize) -> usize {
+        let mut ppn_base = PhysPageNum(0);
+        for i in 0..pages {
+            let frame = frame_alloc().unwrap();
+            if i == 0 {
+                ppn_base = frame.ppn;
+            }
+            assert_eq!(frame.ppn.0, ppn_base.0 + i);
+            QUEUE_FRAMES.exclusive_access().push(frame);
+        }
+        let pa: PhysAddr = ppn_base.into();
+        pa.0
+    }
+
+    fn dma_dealloc(pa: usize, pages: usize) -> i32 {
+        let pa = PhysAddr::from(pa);
+        let mut ppn_base: PhysPageNum = pa.into();
+        for _ in 0..pages {
+            frame_dealloc(ppn_base);
+            ppn_base.step();
+        }
+        0
+    }
+
+    fn phys_to_virt(addr: usize) -> usize {
+        addr
+    }
+
+    fn virt_to_phys(vaddr: usize) -> usize {
+        PageTable::from_token(kernel_token())
+            .translate_va(VirtAddr::from(vaddr))
+            .unwrap()
+            .0
+    }
+}
diff --git a/os/src/drivers/bus/mod.rs b/os/src/drivers/bus/mod.rs
deleted file mode 100644
index d43f304..0000000
--- a/os/src/drivers/bus/mod.rs
+++ /dev/null
@@ -1 +0,0 @@
-pub mod virtio;
diff --git a/os/src/drivers/bus/virtio.rs b/os/src/drivers/bus/virtio.rs
deleted file mode 100644
index 069d478..0000000
--- a/os/src/drivers/bus/virtio.rs
+++ /dev/null
@@ -1,48 +0,0 @@
-use crate::mm::{
-    frame_alloc_more, frame_dealloc, kernel_token, FrameTracker, PageTable, PhysAddr, PhysPageNum,
-    StepByOne, VirtAddr,
-};
-use crate::sync::UPIntrFreeCell;
-use alloc::vec::Vec;
-use lazy_static::*;
-use virtio_drivers::Hal;
-
-lazy_static! {
-    static ref QUEUE_FRAMES: UPIntrFreeCell<Vec<FrameTracker>> =
-        unsafe { UPIntrFreeCell::new(Vec::new()) };
-}
-
-pub struct VirtioHal;
-
-impl Hal for VirtioHal {
-    fn dma_alloc(pages: usize) -> usize {
-        let trakcers = frame_alloc_more(pages);
-        let ppn_base = trakcers.as_ref().unwrap().last().unwrap().ppn;
-        QUEUE_FRAMES
-            .exclusive_access()
-            .append(&mut trakcers.unwrap());
-        let pa: PhysAddr = ppn_base.into();
-        pa.0
-    }
-
-    fn dma_dealloc(pa: usize, pages: usize) -> i32 {
-        let pa = PhysAddr::from(pa);
-        let mut ppn_base: PhysPageNum = pa.into();
-        for _ in 0..pages {
-            frame_dealloc(ppn_base);
-            ppn_base.step();
-        }
-        0
-    }
-
-    fn phys_to_virt(addr: usize) -> usize {
-        addr
-    }
-
-    fn virt_to_phys(vaddr: usize) -> usize {
-        PageTable::from_token(kernel_token())
-            .translate_va(VirtAddr::from(vaddr))
-            .unwrap()
-            .0
-    }
-}
diff --git a/os/src/drivers/chardev/mod.rs b/os/src/drivers/chardev/mod.rs
deleted file mode 100644
index 64c168f..0000000
--- a/os/src/drivers/chardev/mod.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-mod ns16550a;
-
-use crate::board::CharDeviceImpl;
-use alloc::sync::Arc;
-use lazy_static::*;
-pub use ns16550a::NS16550a;
-
-pub trait CharDevice {
-    fn init(&self);
-    fn read(&self) -> u8;
-    fn write(&self, ch: u8);
-    fn handle_irq(&self);
-}
-
-lazy_static! {
-    pub static ref UART: Arc<CharDeviceImpl> = Arc::new(CharDeviceImpl::new());
-}
diff --git a/os/src/drivers/chardev/ns16550a.rs b/os/src/drivers/chardev/ns16550a.rs
deleted file mode 100644
index 7122cec..0000000
--- a/os/src/drivers/chardev/ns16550a.rs
+++ /dev/null
@@ -1,186 +0,0 @@
-///! Ref: https://www.lammertbies.nl/comm/info/serial-uart
-///! Ref: ns16550a datasheet: https://datasheetspdf.com/pdf-file/605590/NationalSemiconductor/NS16550A/1
-///! Ref: ns16450 datasheet: https://datasheetspdf.com/pdf-file/1311818/NationalSemiconductor/NS16450/1
-use super::CharDevice;
-use crate::sync::{Condvar, UPIntrFreeCell};
-use crate::task::schedule;
-use alloc::collections::VecDeque;
-use bitflags::*;
-use volatile::{ReadOnly, Volatile, WriteOnly};
-
-bitflags! {
-    /// InterruptEnableRegister
-    pub struct IER: u8 {
-        const RX_AVAILABLE = 1 << 0;
-        const TX_EMPTY = 1 << 1;
-    }
-
-    /// LineStatusRegister
-    pub struct LSR: u8 {
-        const DATA_AVAILABLE = 1 << 0;
-        const THR_EMPTY = 1 << 5;
-    }
-
-    /// Model Control Register
-    pub struct MCR: u8 {
-        const DATA_TERMINAL_READY = 1 << 0;
-        const REQUEST_TO_SEND = 1 << 1;
-        const AUX_OUTPUT1 = 1 << 2;
-        const AUX_OUTPUT2 = 1 << 3;
-    }
-}
-
-#[repr(C)]
-#[allow(dead_code)]
-struct ReadWithoutDLAB {
-    /// receiver buffer register
-    pub rbr: ReadOnly<u8>,
-    /// interrupt enable register
-    pub ier: Volatile<IER>,
-    /// interrupt identification register
-    pub iir: ReadOnly<u8>,
-    /// line control register
-    pub lcr: Volatile<u8>,
-    /// model control register
-    pub mcr: Volatile<MCR>,
-    /// line status register
-    pub lsr: ReadOnly<LSR>,
-    /// ignore MSR
-    _padding1: ReadOnly<u8>,
-    /// ignore SCR
-    _padding2: ReadOnly<u8>,
-}
-
-#[repr(C)]
-#[allow(dead_code)]
-struct WriteWithoutDLAB {
-    /// transmitter holding register
-    pub thr: WriteOnly<u8>,
-    /// interrupt enable register
-    pub ier: Volatile<IER>,
-    /// ignore FCR
-    _padding0: ReadOnly<u8>,
-    /// line control register
-    pub lcr: Volatile<u8>,
-    /// modem control register
-    pub mcr: Volatile<MCR>,
-    /// line status register
-    pub lsr: ReadOnly<LSR>,
-    /// ignore other registers
-    _padding1: ReadOnly<u16>,
-}
-
-pub struct NS16550aRaw {
-    base_addr: usize,
-}
-
-impl NS16550aRaw {
-    fn read_end(&mut self) -> &mut ReadWithoutDLAB {
-        unsafe { &mut *(self.base_addr as *mut ReadWithoutDLAB) }
-    }
-
-    fn write_end(&mut self) -> &mut WriteWithoutDLAB {
-        unsafe { &mut *(self.base_addr as *mut WriteWithoutDLAB) }
-    }
-
-    pub fn new(base_addr: usize) -> Self {
-        Self { base_addr }
-    }
-
-    pub fn init(&mut self) {
-        let read_end = self.read_end();
-        let mut mcr = MCR::empty();
-        mcr |= MCR::DATA_TERMINAL_READY;
-        mcr |= MCR::REQUEST_TO_SEND;
-        mcr |= MCR::AUX_OUTPUT2;
-        read_end.mcr.write(mcr);
-        let ier = IER::RX_AVAILABLE;
-        read_end.ier.write(ier);
-    }
-
-    pub fn read(&mut self) -> Option<u8> {
-        let read_end = self.read_end();
-        let lsr = read_end.lsr.read();
-        if lsr.contains(LSR::DATA_AVAILABLE) {
-            Some(read_end.rbr.read())
-        } else {
-            None
-        }
-    }
-
-    pub fn write(&mut self, ch: u8) {
-        let write_end = self.write_end();
-        loop {
-            if write_end.lsr.read().contains(LSR::THR_EMPTY) {
-                write_end.thr.write(ch);
-                break;
-            }
-        }
-    }
-}
-
-struct NS16550aInner {
-    ns16550a: NS16550aRaw,
-    read_buffer: VecDeque<u8>,
-}
-
-pub struct NS16550a<const BASE_ADDR: usize> {
-    inner: UPIntrFreeCell<NS16550aInner>,
-    condvar: Condvar,
-}
-
-impl<const BASE_ADDR: usize> NS16550a<BASE_ADDR> {
-    pub fn new() -> Self {
-        let inner = NS16550aInner {
-            ns16550a: NS16550aRaw::new(BASE_ADDR),
-            read_buffer: VecDeque::new(),
-        };
-        //inner.ns16550a.init();
-        Self {
-            inner: unsafe { UPIntrFreeCell::new(inner) },
-            condvar: Condvar::new(),
-        }
-    }
-
-    pub fn read_buffer_is_empty(&self) -> bool {
-        self.inner
-            .exclusive_session(|inner| inner.read_buffer.is_empty())
-    }
-}
-
-impl<const BASE_ADDR: usize> CharDevice for NS16550a<BASE_ADDR> {
-    fn init(&self) {
-        let mut inner = self.inner.exclusive_access();
-        inner.ns16550a.init();
-        drop(inner);
-    }
-
-    fn read(&self) -> u8 {
-        loop {
-            let mut inner = self.inner.exclusive_access();
-            if let Some(ch) = inner.read_buffer.pop_front() {
-                return ch;
-            } else {
-                let task_cx_ptr = self.condvar.wait_no_sched();
-                drop(inner);
-                schedule(task_cx_ptr);
-            }
-        }
-    }
-    fn write(&self, ch: u8) {
-        let mut inner = self.inner.exclusive_access();
-        inner.ns16550a.write(ch);
-    }
-    fn handle_irq(&self) {
-        let mut count = 0;
-        self.inner.exclusive_session(|inner| {
-            while let Some(ch) = inner.ns16550a.read() {
-                count += 1;
-                inner.read_buffer.push_back(ch);
-            }
-        });
-        if count > 0 {
-            self.condvar.signal();
-        }
-    }
-}
diff --git a/os/src/drivers/gpu/mod.rs b/os/src/drivers/gpu/mod.rs
deleted file mode 100644
index 759633f..0000000
--- a/os/src/drivers/gpu/mod.rs
+++ /dev/null
@@ -1,68 +0,0 @@
-use crate::drivers::bus::virtio::VirtioHal;
-use crate::sync::UPIntrFreeCell;
-use alloc::{sync::Arc, vec::Vec};
-use core::any::Any;
-use embedded_graphics::pixelcolor::Rgb888;
-use tinybmp::Bmp;
-use virtio_drivers::{VirtIOGpu, VirtIOHeader};
-const VIRTIO7: usize = 0x10007000;
-pub trait GpuDevice: Send + Sync + Any {
-    fn update_cursor(&self);
-    fn get_framebuffer(&self) -> &mut [u8];
-    fn flush(&self);
-}
-
-lazy_static::lazy_static!(
-    pub static ref GPU_DEVICE: Arc<dyn GpuDevice> = Arc::new(VirtIOGpuWrapper::new());
-);
-
-pub struct VirtIOGpuWrapper {
-    gpu: UPIntrFreeCell<VirtIOGpu<'static, VirtioHal>>,
-    fb: &'static [u8],
-}
-static BMP_DATA: &[u8] = include_bytes!("../../assert/mouse.bmp");
-impl VirtIOGpuWrapper {
-    pub fn new() -> Self {
-        unsafe {
-            let mut virtio =
-                VirtIOGpu::<VirtioHal>::new(&mut *(VIRTIO7 as *mut VirtIOHeader)).unwrap();
-
-            let fbuffer = virtio.setup_framebuffer().unwrap();
-            let len = fbuffer.len();
-            let ptr = fbuffer.as_mut_ptr();
-            let fb = core::slice::from_raw_parts_mut(ptr, len);
-
-            let bmp = Bmp::<Rgb888>::from_slice(BMP_DATA).unwrap();
-            let raw = bmp.as_raw();
-            let mut b = Vec::new();
-            for i in raw.image_data().chunks(3) {
-                let mut v = i.to_vec();
-                b.append(&mut v);
-                if i == [255, 255, 255] {
-                    b.push(0x0)
-                } else {
-                    b.push(0xff)
-                }
-            }
-            virtio.setup_cursor(b.as_slice(), 50, 50, 50, 50).unwrap();
-
-            Self {
-                gpu: UPIntrFreeCell::new(virtio),
-                fb,
-            }
-        }
-    }
-}
-
-impl GpuDevice for VirtIOGpuWrapper {
-    fn flush(&self) {
-        self.gpu.exclusive_access().flush().unwrap();
-    }
-    fn get_framebuffer(&self) -> &mut [u8] {
-        unsafe {
-            let ptr = self.fb.as_ptr() as *const _ as *mut u8;
-            core::slice::from_raw_parts_mut(ptr, self.fb.len())
-        }
-    }
-    fn update_cursor(&self) {}
-}
diff --git a/os/src/drivers/input/mod.rs b/os/src/drivers/input/mod.rs
deleted file mode 100644
index a9f5f0b..0000000
--- a/os/src/drivers/input/mod.rs
+++ /dev/null
@@ -1,83 +0,0 @@
-use crate::drivers::bus::virtio::VirtioHal;
-use crate::sync::{Condvar, UPIntrFreeCell};
-use crate::task::schedule;
-use alloc::collections::VecDeque;
-use alloc::sync::Arc;
-use core::any::Any;
-use virtio_drivers::{VirtIOHeader, VirtIOInput};
-
-const VIRTIO5: usize = 0x10005000;
-const VIRTIO6: usize = 0x10006000;
-
-struct VirtIOInputInner {
-    virtio_input: VirtIOInput<'static, VirtioHal>,
-    events: VecDeque<u64>,
-}
-
-struct VirtIOInputWrapper {
-    inner: UPIntrFreeCell<VirtIOInputInner>,
-    condvar: Condvar,
-}
-
-pub trait InputDevice: Send + Sync + Any {
-    fn read_event(&self) -> u64;
-    fn handle_irq(&self);
-    fn is_empty(&self) -> bool;
-}
-
-lazy_static::lazy_static!(
-    pub static ref KEYBOARD_DEVICE: Arc<dyn InputDevice> = Arc::new(VirtIOInputWrapper::new(VIRTIO5));
-    pub static ref MOUSE_DEVICE: Arc<dyn InputDevice> = Arc::new(VirtIOInputWrapper::new(VIRTIO6));
-);
-
-impl VirtIOInputWrapper {
-    pub fn new(addr: usize) -> Self {
-        let inner = VirtIOInputInner {
-            virtio_input: unsafe {
-                VirtIOInput::<VirtioHal>::new(&mut *(addr as *mut VirtIOHeader)).unwrap()
-            },
-            events: VecDeque::new(),
-        };
-        Self {
-            inner: unsafe { UPIntrFreeCell::new(inner) },
-            condvar: Condvar::new(),
-        }
-    }
-}
-
-impl InputDevice for VirtIOInputWrapper {
-    fn is_empty(&self) -> bool {
-        self.inner.exclusive_access().events.is_empty()
-    }
-
-    fn read_event(&self) -> u64 {
-        loop {
-            let mut inner = self.inner.exclusive_access();
-            if let Some(event) = inner.events.pop_front() {
-                return event;
-            } else {
-                let task_cx_ptr = self.condvar.wait_no_sched();
-                drop(inner);
-                schedule(task_cx_ptr);
-            }
-        }
-    }
-
-    fn handle_irq(&self) {
-        let mut count = 0;
-        let mut result = 0;
-        self.inner.exclusive_session(|inner| {
-            inner.virtio_input.ack_interrupt();
-            while let Some(event) = inner.virtio_input.pop_pending_event() {
-                count += 1;
-                result = (event.event_type as u64) << 48
-                    | (event.code as u64) << 32
-                    | (event.value) as u64;
-                inner.events.push_back(result);
-            }
-        });
-        if count > 0 {
-            self.condvar.signal();
-        };
-    }
-}
diff --git a/os/src/drivers/mod.rs b/os/src/drivers/mod.rs
index 605397d..c2dea36 100644
--- a/os/src/drivers/mod.rs
+++ b/os/src/drivers/mod.rs
@@ -1,13 +1,3 @@
 pub mod block;
-pub mod bus;
-pub mod chardev;
-pub mod gpu;
-pub mod input;
-pub mod net;
-pub mod plic;
 
 pub use block::BLOCK_DEVICE;
-pub use bus::*;
-pub use gpu::*;
-pub use input::*;
-pub use net::*;
diff --git a/os/src/drivers/net/mod.rs b/os/src/drivers/net/mod.rs
deleted file mode 100644
index 7a70587..0000000
--- a/os/src/drivers/net/mod.rs
+++ /dev/null
@@ -1,46 +0,0 @@
-use core::any::Any;
-
-use crate::drivers::virtio::VirtioHal;
-use crate::sync::UPIntrFreeCell;
-use alloc::sync::Arc;
-use lazy_static::*;
-use virtio_drivers::{VirtIOHeader, VirtIONet};
-
-const VIRTIO8: usize = 0x10004000;
-
-lazy_static! {
-    pub static ref NET_DEVICE: Arc<dyn NetDevice> = Arc::new(VirtIONetWrapper::new());
-}
-
-pub trait NetDevice: Send + Sync + Any {
-    fn transmit(&self, data: &[u8]);
-    fn receive(&self, data: &mut [u8]) -> usize;
-}
-
-pub struct VirtIONetWrapper(UPIntrFreeCell<VirtIONet<'static, VirtioHal>>);
-
-impl NetDevice for VirtIONetWrapper {
-    fn transmit(&self, data: &[u8]) {
-        self.0
-            .exclusive_access()
-            .send(data)
-            .expect("can't send data")
-    }
-
-    fn receive(&self, data: &mut [u8]) -> usize {
-        self.0
-            .exclusive_access()
-            .recv(data)
-            .expect("can't receive data")
-    }
-}
-
-impl VirtIONetWrapper {
-    pub fn new() -> Self {
-        unsafe {
-            let virtio = VirtIONet::<VirtioHal>::new(&mut *(VIRTIO8 as *mut VirtIOHeader))
-                .expect("can't create net device by virtio");
-            VirtIONetWrapper(UPIntrFreeCell::new(virtio))
-        }
-    }
-}
diff --git a/os/src/drivers/plic.rs b/os/src/drivers/plic.rs
deleted file mode 100644
index 77bad5f..0000000
--- a/os/src/drivers/plic.rs
+++ /dev/null
@@ -1,124 +0,0 @@
-#[allow(clippy::upper_case_acronyms)]
-pub struct PLIC {
-    base_addr: usize,
-}
-
-#[derive(Copy, Clone)]
-pub enum IntrTargetPriority {
-    Machine = 0,
-    Supervisor = 1,
-}
-
-impl IntrTargetPriority {
-    pub fn supported_number() -> usize {
-        2
-    }
-}
-
-impl PLIC {
-    fn priority_ptr(&self, intr_source_id: usize) -> *mut u32 {
-        assert!(intr_source_id > 0 && intr_source_id <= 132);
-        (self.base_addr + intr_source_id * 4) as *mut u32
-    }
-    fn hart_id_with_priority(hart_id: usize, target_priority: IntrTargetPriority) -> usize {
-        let priority_num = IntrTargetPriority::supported_number();
-        hart_id * priority_num + target_priority as usize
-    }
-    fn enable_ptr(
-        &self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-        intr_source_id: usize,
-    ) -> (*mut u32, usize) {
-        let id = Self::hart_id_with_priority(hart_id, target_priority);
-        let (reg_id, reg_shift) = (intr_source_id / 32, intr_source_id % 32);
-        (
-            (self.base_addr + 0x2000 + 0x80 * id + 0x4 * reg_id) as *mut u32,
-            reg_shift,
-        )
-    }
-    fn threshold_ptr_of_hart_with_priority(
-        &self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-    ) -> *mut u32 {
-        let id = Self::hart_id_with_priority(hart_id, target_priority);
-        (self.base_addr + 0x20_0000 + 0x1000 * id) as *mut u32
-    }
-    fn claim_comp_ptr_of_hart_with_priority(
-        &self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-    ) -> *mut u32 {
-        let id = Self::hart_id_with_priority(hart_id, target_priority);
-        (self.base_addr + 0x20_0004 + 0x1000 * id) as *mut u32
-    }
-    pub unsafe fn new(base_addr: usize) -> Self {
-        Self { base_addr }
-    }
-    pub fn set_priority(&mut self, intr_source_id: usize, priority: u32) {
-        assert!(priority < 8);
-        unsafe {
-            self.priority_ptr(intr_source_id).write_volatile(priority);
-        }
-    }
-    #[allow(unused)]
-    pub fn get_priority(&mut self, intr_source_id: usize) -> u32 {
-        unsafe { self.priority_ptr(intr_source_id).read_volatile() & 7 }
-    }
-    pub fn enable(
-        &mut self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-        intr_source_id: usize,
-    ) {
-        let (reg_ptr, shift) = self.enable_ptr(hart_id, target_priority, intr_source_id);
-        unsafe {
-            reg_ptr.write_volatile(reg_ptr.read_volatile() | 1 << shift);
-        }
-    }
-    #[allow(unused)]
-    pub fn disable(
-        &mut self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-        intr_source_id: usize,
-    ) {
-        let (reg_ptr, shift) = self.enable_ptr(hart_id, target_priority, intr_source_id);
-        unsafe {
-            reg_ptr.write_volatile(reg_ptr.read_volatile() & (!(1u32 << shift)));
-        }
-    }
-    pub fn set_threshold(
-        &mut self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-        threshold: u32,
-    ) {
-        assert!(threshold < 8);
-        let threshold_ptr = self.threshold_ptr_of_hart_with_priority(hart_id, target_priority);
-        unsafe {
-            threshold_ptr.write_volatile(threshold);
-        }
-    }
-    #[allow(unused)]
-    pub fn get_threshold(&mut self, hart_id: usize, target_priority: IntrTargetPriority) -> u32 {
-        let threshold_ptr = self.threshold_ptr_of_hart_with_priority(hart_id, target_priority);
-        unsafe { threshold_ptr.read_volatile() & 7 }
-    }
-    pub fn claim(&mut self, hart_id: usize, target_priority: IntrTargetPriority) -> u32 {
-        let claim_comp_ptr = self.claim_comp_ptr_of_hart_with_priority(hart_id, target_priority);
-        unsafe { claim_comp_ptr.read_volatile() }
-    }
-    pub fn complete(
-        &mut self,
-        hart_id: usize,
-        target_priority: IntrTargetPriority,
-        completion: u32,
-    ) {
-        let claim_comp_ptr = self.claim_comp_ptr_of_hart_with_priority(hart_id, target_priority);
-        unsafe {
-            claim_comp_ptr.write_volatile(completion);
-        }
-    }
-}
diff --git a/os/src/entry.asm b/os/src/entry.asm
index c32d68f..3a9990f 100644
--- a/os/src/entry.asm
+++ b/os/src/entry.asm
@@ -9,4 +9,4 @@ _start:
 boot_stack_lower_bound:
     .space 4096 * 16
     .globl boot_stack_top
-boot_stack_top:
+boot_stack_top:
\ No newline at end of file
diff --git a/os/src/fs/inode.rs b/os/src/fs/inode.rs
index 321338d..2490d6a 100644
--- a/os/src/fs/inode.rs
+++ b/os/src/fs/inode.rs
@@ -1,32 +1,41 @@
+//! `Arc<Inode>` -> `OSInodeInner`: In order to open files concurrently
+//! we need to wrap `Inode` into `Arc`,but `Mutex` in `Inode` prevents
+//! file systems from being accessed simultaneously
+//!
+//! `UPSafeCell<OSInodeInner>` -> `OSInode`: for static `ROOT_INODE`,we
+//! need to wrap `OSInodeInner` into `UPSafeCell`
 use super::File;
 use crate::drivers::BLOCK_DEVICE;
 use crate::mm::UserBuffer;
-use crate::sync::UPIntrFreeCell;
+use crate::sync::UPSafeCell;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
 use bitflags::*;
 use easy_fs::{EasyFileSystem, Inode};
 use lazy_static::*;
-
+/// A wrapper around a filesystem inode
+/// to implement File trait atop
 pub struct OSInode {
     readable: bool,
     writable: bool,
-    inner: UPIntrFreeCell<OSInodeInner>,
+    inner: UPSafeCell<OSInodeInner>,
 }
-
+/// The OS inode inner in 'UPSafeCell'
 pub struct OSInodeInner {
     offset: usize,
     inode: Arc<Inode>,
 }
 
 impl OSInode {
+    /// Construct an OS inode from a inode
     pub fn new(readable: bool, writable: bool, inode: Arc<Inode>) -> Self {
         Self {
             readable,
             writable,
-            inner: unsafe { UPIntrFreeCell::new(OSInodeInner { offset: 0, inode }) },
+            inner: unsafe { UPSafeCell::new(OSInodeInner { offset: 0, inode }) },
         }
     }
+    /// Read all data inside a inode into vector
     pub fn read_all(&self) -> Vec<u8> {
         let mut inner = self.inner.exclusive_access();
         let mut buffer = [0u8; 512];
@@ -49,21 +58,27 @@ lazy_static! {
         Arc::new(EasyFileSystem::root_inode(&efs))
     };
 }
-
+/// List all files in the filesystems
 pub fn list_apps() {
     println!("/**** APPS ****");
     for app in ROOT_INODE.ls() {
         println!("{}", app);
     }
-    println!("**************/")
+    println!("**************/");
 }
 
 bitflags! {
+    ///Open file flags
     pub struct OpenFlags: u32 {
+        ///Read only
         const RDONLY = 0;
+        ///Write only
         const WRONLY = 1 << 0;
+        ///Read & Write
         const RDWR = 1 << 1;
+        ///Allow create
         const CREATE = 1 << 9;
+        ///Clear file and return an empty one
         const TRUNC = 1 << 10;
     }
 }
@@ -81,7 +96,7 @@ impl OpenFlags {
         }
     }
 }
-
+///Open file with flags
 pub fn open_file(name: &str, flags: OpenFlags) -> Option<Arc<OSInode>> {
     let (readable, writable) = flags.read_write();
     if flags.contains(OpenFlags::CREATE) {
diff --git a/os/src/fs/mod.rs b/os/src/fs/mod.rs
index cbde739..c3cc1e7 100644
--- a/os/src/fs/mod.rs
+++ b/os/src/fs/mod.rs
@@ -1,16 +1,19 @@
+//! File system in os
 mod inode;
-mod pipe;
 mod stdio;
 
 use crate::mm::UserBuffer;
-
+/// File trait
 pub trait File: Send + Sync {
+    /// If readable
     fn readable(&self) -> bool;
+    /// If writable
     fn writable(&self) -> bool;
+    /// Read file to `UserBuffer`
     fn read(&self, buf: UserBuffer) -> usize;
+    /// Write `UserBuffer` to file
     fn write(&self, buf: UserBuffer) -> usize;
 }
 
-pub use inode::{list_apps, open_file, OpenFlags};
-pub use pipe::make_pipe;
+pub use inode::{OSInode, OpenFlags, list_apps, open_file};
 pub use stdio::{Stdin, Stdout};
diff --git a/os/src/fs/pipe.rs b/os/src/fs/pipe.rs
deleted file mode 100644
index d10dc33..0000000
--- a/os/src/fs/pipe.rs
+++ /dev/null
@@ -1,173 +0,0 @@
-use super::File;
-use crate::mm::UserBuffer;
-use crate::sync::UPIntrFreeCell;
-use alloc::sync::{Arc, Weak};
-
-use crate::task::suspend_current_and_run_next;
-
-pub struct Pipe {
-    readable: bool,
-    writable: bool,
-    buffer: Arc<UPIntrFreeCell<PipeRingBuffer>>,
-}
-
-impl Pipe {
-    pub fn read_end_with_buffer(buffer: Arc<UPIntrFreeCell<PipeRingBuffer>>) -> Self {
-        Self {
-            readable: true,
-            writable: false,
-            buffer,
-        }
-    }
-    pub fn write_end_with_buffer(buffer: Arc<UPIntrFreeCell<PipeRingBuffer>>) -> Self {
-        Self {
-            readable: false,
-            writable: true,
-            buffer,
-        }
-    }
-}
-
-const RING_BUFFER_SIZE: usize = 32;
-
-#[derive(Copy, Clone, PartialEq)]
-enum RingBufferStatus {
-    Full,
-    Empty,
-    Normal,
-}
-
-pub struct PipeRingBuffer {
-    arr: [u8; RING_BUFFER_SIZE],
-    head: usize,
-    tail: usize,
-    status: RingBufferStatus,
-    write_end: Option<Weak<Pipe>>,
-}
-
-impl PipeRingBuffer {
-    pub fn new() -> Self {
-        Self {
-            arr: [0; RING_BUFFER_SIZE],
-            head: 0,
-            tail: 0,
-            status: RingBufferStatus::Empty,
-            write_end: None,
-        }
-    }
-    pub fn set_write_end(&mut self, write_end: &Arc<Pipe>) {
-        self.write_end = Some(Arc::downgrade(write_end));
-    }
-    pub fn write_byte(&mut self, byte: u8) {
-        self.status = RingBufferStatus::Normal;
-        self.arr[self.tail] = byte;
-        self.tail = (self.tail + 1) % RING_BUFFER_SIZE;
-        if self.tail == self.head {
-            self.status = RingBufferStatus::Full;
-        }
-    }
-    pub fn read_byte(&mut self) -> u8 {
-        self.status = RingBufferStatus::Normal;
-        let c = self.arr[self.head];
-        self.head = (self.head + 1) % RING_BUFFER_SIZE;
-        if self.head == self.tail {
-            self.status = RingBufferStatus::Empty;
-        }
-        c
-    }
-    pub fn available_read(&self) -> usize {
-        if self.status == RingBufferStatus::Empty {
-            0
-        } else if self.tail > self.head {
-            self.tail - self.head
-        } else {
-            self.tail + RING_BUFFER_SIZE - self.head
-        }
-    }
-    pub fn available_write(&self) -> usize {
-        if self.status == RingBufferStatus::Full {
-            0
-        } else {
-            RING_BUFFER_SIZE - self.available_read()
-        }
-    }
-    pub fn all_write_ends_closed(&self) -> bool {
-        self.write_end.as_ref().unwrap().upgrade().is_none()
-    }
-}
-
-/// Return (read_end, write_end)
-pub fn make_pipe() -> (Arc<Pipe>, Arc<Pipe>) {
-    let buffer = Arc::new(unsafe { UPIntrFreeCell::new(PipeRingBuffer::new()) });
-    let read_end = Arc::new(Pipe::read_end_with_buffer(buffer.clone()));
-    let write_end = Arc::new(Pipe::write_end_with_buffer(buffer.clone()));
-    buffer.exclusive_access().set_write_end(&write_end);
-    (read_end, write_end)
-}
-
-impl File for Pipe {
-    fn readable(&self) -> bool {
-        self.readable
-    }
-    fn writable(&self) -> bool {
-        self.writable
-    }
-    fn read(&self, buf: UserBuffer) -> usize {
-        assert!(self.readable());
-        let want_to_read = buf.len();
-        let mut buf_iter = buf.into_iter();
-        let mut already_read = 0usize;
-        loop {
-            let mut ring_buffer = self.buffer.exclusive_access();
-            let loop_read = ring_buffer.available_read();
-            if loop_read == 0 {
-                if ring_buffer.all_write_ends_closed() {
-                    return already_read;
-                }
-                drop(ring_buffer);
-                suspend_current_and_run_next();
-                continue;
-            }
-            for _ in 0..loop_read {
-                if let Some(byte_ref) = buf_iter.next() {
-                    unsafe {
-                        *byte_ref = ring_buffer.read_byte();
-                    }
-                    already_read += 1;
-                    if already_read == want_to_read {
-                        return want_to_read;
-                    }
-                } else {
-                    return already_read;
-                }
-            }
-        }
-    }
-    fn write(&self, buf: UserBuffer) -> usize {
-        assert!(self.writable());
-        let want_to_write = buf.len();
-        let mut buf_iter = buf.into_iter();
-        let mut already_write = 0usize;
-        loop {
-            let mut ring_buffer = self.buffer.exclusive_access();
-            let loop_write = ring_buffer.available_write();
-            if loop_write == 0 {
-                drop(ring_buffer);
-                suspend_current_and_run_next();
-                continue;
-            }
-            // write at most loop_write bytes
-            for _ in 0..loop_write {
-                if let Some(byte_ref) = buf_iter.next() {
-                    ring_buffer.write_byte(unsafe { *byte_ref });
-                    already_write += 1;
-                    if already_write == want_to_write {
-                        return want_to_write;
-                    }
-                } else {
-                    return already_write;
-                }
-            }
-        }
-    }
-}
diff --git a/os/src/fs/stdio.rs b/os/src/fs/stdio.rs
index 66f4c5a..8375ac9 100644
--- a/os/src/fs/stdio.rs
+++ b/os/src/fs/stdio.rs
@@ -1,9 +1,11 @@
+//!Stdin & Stdout
 use super::File;
-use crate::drivers::chardev::CharDevice;
-use crate::drivers::chardev::UART;
 use crate::mm::UserBuffer;
-
+use crate::sbi::console_getchar;
+use crate::task::suspend_current_and_run_next;
+///Standard input
 pub struct Stdin;
+///Standard output
 pub struct Stdout;
 
 impl File for Stdin {
@@ -15,8 +17,18 @@ impl File for Stdin {
     }
     fn read(&self, mut user_buf: UserBuffer) -> usize {
         assert_eq!(user_buf.len(), 1);
-        //println!("before UART.read() in Stdin::read()");
-        let ch = UART.read();
+        // busy loop
+        let mut c: usize;
+        loop {
+            c = console_getchar();
+            if c == 0 {
+                suspend_current_and_run_next();
+                continue;
+            } else {
+                break;
+            }
+        }
+        let ch = c as u8;
         unsafe {
             user_buf.buffers[0].as_mut_ptr().write_volatile(ch);
         }
diff --git a/os/src/lang_items.rs b/os/src/lang_items.rs
index 021f16f..79cd51e 100644
--- a/os/src/lang_items.rs
+++ b/os/src/lang_items.rs
@@ -1,6 +1,5 @@
+//! The panic handler
 use crate::sbi::shutdown;
-use crate::task::current_kstack_top;
-use core::arch::asm;
 use core::panic::PanicInfo;
 use log::*;
 
@@ -11,28 +10,10 @@ fn panic(info: &PanicInfo) -> ! {
             "[kernel] Panicked at {}:{} {}",
             location.file(),
             location.line(),
-            info.message().unwrap()
+            info.message()
         );
     } else {
-        error!("[kernel] Panicked: {}", info.message().unwrap());
-    }
-    unsafe {
-        backtrace();
+        error!("[kernel] Panicked: {}", info.message());
     }
     shutdown(true)
 }
-
-unsafe fn backtrace() {
-    let mut fp: usize;
-    let stop = current_kstack_top();
-    asm!("mv {}, s0", out(reg) fp);
-    println!("---START BACKTRACE---");
-    for i in 0..10 {
-        if fp == stop {
-            break;
-        }
-        println!("#{}:ra={:#x}", i, *((fp - 8) as *const usize));
-        fp = *((fp - 16) as *const usize);
-    }
-    println!("---END   BACKTRACE---");
-}
diff --git a/os/src/logging.rs b/os/src/logging.rs
new file mode 100644
index 0000000..b5421f1
--- /dev/null
+++ b/os/src/logging.rs
@@ -0,0 +1,47 @@
+/*！
+
+本模块利用 log crate 为你提供了日志功能，使用方式见 main.rs.
+
+*/
+
+use log::{self, Level, LevelFilter, Log, Metadata, Record};
+
+struct SimpleLogger;
+
+impl Log for SimpleLogger {
+    fn enabled(&self, _metadata: &Metadata) -> bool {
+        true
+    }
+    fn log(&self, record: &Record) {
+        if !self.enabled(record.metadata()) {
+            return;
+        }
+        let color = match record.level() {
+            Level::Error => 31, // Red
+            Level::Warn => 93,  // BrightYellow
+            Level::Info => 34,  // Blue
+            Level::Debug => 32, // Green
+            Level::Trace => 90, // BrightBlack
+        };
+        println!(
+            "\u{1B}[{}m[{:>5}] {}\u{1B}[0m",
+            color,
+            record.level(),
+            record.args(),
+        );
+    }
+    fn flush(&self) {}
+}
+
+pub fn init() {
+    static LOGGER: SimpleLogger = SimpleLogger;
+    log::set_logger(&LOGGER).unwrap();
+    log::set_max_level(match option_env!("LOG") {
+        Some("ERROR") => LevelFilter::Error,
+        Some("WARN") => LevelFilter::Warn,
+        Some("INFO") => LevelFilter::Info,
+        Some("DEBUG") => LevelFilter::Debug,
+        Some("TRACE") => LevelFilter::Trace,
+        _ => LevelFilter::Info,
+    });
+}
diff --git a/os/src/main.rs b/os/src/main.rs
index 276aaf5..46161de 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -1,15 +1,37 @@
+//! The main module and entrypoint
+//!
+//! Various facilities of the kernels are implemented as submodules. The most
+//! important ones are:
+//!
+//! - [`trap`]: Handles all cases of switching from userspace to the kernel
+//! - [`task`]: Task management
+//! - [`syscall`]: System call handling and implementation
+//! - [`mm`]: Address map using SV39
+//! - [`sync`]: Wrap a static data structure inside it so that we are able to access it without any `unsafe`.
+//! - [`fs`]: Separate user from file system with some structures
+//!
+//! The operating system also starts in this module. Kernel code starts
+//! executing from `entry.asm`, after which [`rust_main()`] is called to
+//! initialize various pieces of functionality. (See its source code for
+//! details.)
+//!
+//! We then call [`task::run_tasks()`] and for the first time go to
+//! userspace.
+
+#![deny(missing_docs)]
+#![deny(warnings)]
+#![allow(unused_imports)]
 #![no_std]
 #![no_main]
-#![feature(panic_info_message)]
 #![feature(alloc_error_handler)]
 
-//use crate::drivers::{GPU_DEVICE, KEYBOARD_DEVICE, MOUSE_DEVICE, INPUT_CONDVAR};
-use crate::drivers::{GPU_DEVICE, KEYBOARD_DEVICE, MOUSE_DEVICE};
 extern crate alloc;
 
 #[macro_use]
 extern crate bitflags;
 
+use log::*;
+
 #[path = "boards/qemu.rs"]
 mod board;
 
@@ -17,26 +39,25 @@ mod board;
 mod console;
 mod config;
 mod drivers;
-mod fs;
-mod lang_items;
-mod mm;
-mod net;
-mod sbi;
-mod sync;
-mod syscall;
-mod task;
-mod timer;
-mod trap;
+pub mod fs;
+pub mod lang_items;
+mod logging;
+pub mod mm;
+pub mod sbi;
+pub mod sync;
+pub mod syscall;
+pub mod task;
+pub mod timer;
+pub mod trap;
 
-use crate::drivers::chardev::CharDevice;
-use crate::drivers::chardev::UART;
-
-core::arch::global_asm!(include_str!("entry.asm"));
+use core::arch::global_asm;
 
+global_asm!(include_str!("entry.asm"));
+/// clear BSS segment
 fn clear_bss() {
-    extern "C" {
-        fn sbss();
-        fn ebss();
+    unsafe extern "C" {
+        safe fn sbss();
+        safe fn ebss();
     }
     unsafe {
         core::slice::from_raw_parts_mut(sbss as usize as *mut u8, ebss as usize - sbss as usize)
@@ -44,33 +65,19 @@ fn clear_bss() {
     }
 }
 
-use lazy_static::*;
-use sync::UPIntrFreeCell;
-
-lazy_static! {
-    pub static ref DEV_NON_BLOCKING_ACCESS: UPIntrFreeCell<bool> =
-        unsafe { UPIntrFreeCell::new(false) };
-}
-
-#[no_mangle]
+/// the rust entry-point of os
+#[unsafe(no_mangle)]
 pub fn rust_main() -> ! {
     clear_bss();
+    logging::init();
+    info!("[kernel] Hello, world!");
     mm::init();
-    UART.init();
-    println!("KERN: init gpu");
-    let _gpu = GPU_DEVICE.clone();
-    println!("KERN: init keyboard");
-    let _keyboard = KEYBOARD_DEVICE.clone();
-    println!("KERN: init mouse");
-    let _mouse = MOUSE_DEVICE.clone();
-    println!("KERN: init trap");
+    mm::remap_test();
     trap::init();
     trap::enable_timer_interrupt();
     timer::set_next_trigger();
-    board::device_init();
     fs::list_apps();
     task::add_initproc();
-    *DEV_NON_BLOCKING_ACCESS.exclusive_access() = true;
     task::run_tasks();
     panic!("Unreachable in rust_main!");
 }
diff --git a/os/src/mm/address.rs b/os/src/mm/address.rs
index df3e130..f0ee691 100644
--- a/os/src/mm/address.rs
+++ b/os/src/mm/address.rs
@@ -1,3 +1,4 @@
+//! Implementation of physical and virtual address and page number.
 use super::PageTableEntry;
 use crate::config::{PAGE_SIZE, PAGE_SIZE_BITS};
 use core::fmt::{self, Debug, Formatter};
@@ -14,14 +15,17 @@ pub struct PhysAddr(pub usize);
 
 #[repr(C)]
 #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
+///virtual address
 pub struct VirtAddr(pub usize);
 
 #[repr(C)]
 #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
+///phiscal page number
 pub struct PhysPageNum(pub usize);
 
 #[repr(C)]
 #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
+///virtual page number
 pub struct VirtPageNum(pub usize);
 
 /// Debugging
@@ -95,11 +99,13 @@ impl From<VirtPageNum> for usize {
         v.0
     }
 }
-
+///
 impl VirtAddr {
+    ///`VirtAddr`->`VirtPageNum`
     pub fn floor(&self) -> VirtPageNum {
         VirtPageNum(self.0 / PAGE_SIZE)
     }
+    ///`VirtAddr`->`VirtPageNum`
     pub fn ceil(&self) -> VirtPageNum {
         if self.0 == 0 {
             VirtPageNum(0)
@@ -107,9 +113,11 @@ impl VirtAddr {
             VirtPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
         }
     }
+    ///Get page offset
     pub fn page_offset(&self) -> usize {
         self.0 & (PAGE_SIZE - 1)
     }
+    ///Check page aligned
     pub fn aligned(&self) -> bool {
         self.page_offset() == 0
     }
@@ -126,9 +134,11 @@ impl From<VirtPageNum> for VirtAddr {
     }
 }
 impl PhysAddr {
+    ///`PhysAddr`->`PhysPageNum`
     pub fn floor(&self) -> PhysPageNum {
         PhysPageNum(self.0 / PAGE_SIZE)
     }
+    ///`PhysAddr`->`PhysPageNum`
     pub fn ceil(&self) -> PhysPageNum {
         if self.0 == 0 {
             PhysPageNum(0)
@@ -136,9 +146,11 @@ impl PhysAddr {
             PhysPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
         }
     }
+    ///Get page offset
     pub fn page_offset(&self) -> usize {
         self.0 & (PAGE_SIZE - 1)
     }
+    ///Check page aligned
     pub fn aligned(&self) -> bool {
         self.page_offset() == 0
     }
@@ -156,6 +168,7 @@ impl From<PhysPageNum> for PhysAddr {
 }
 
 impl VirtPageNum {
+    ///Return VPN 3 level index
     pub fn indexes(&self) -> [usize; 3] {
         let mut vpn = self.0;
         let mut idx = [0usize; 3];
@@ -168,29 +181,35 @@ impl VirtPageNum {
 }
 
 impl PhysAddr {
+    ///Get reference to `PhysAddr` value
     pub fn get_ref<T>(&self) -> &'static T {
         unsafe { (self.0 as *const T).as_ref().unwrap() }
     }
+    ///Get mutable reference to `PhysAddr` value
     pub fn get_mut<T>(&self) -> &'static mut T {
         unsafe { (self.0 as *mut T).as_mut().unwrap() }
     }
 }
 impl PhysPageNum {
+    ///Get `PageTableEntry` on `PhysPageNum`
     pub fn get_pte_array(&self) -> &'static mut [PageTableEntry] {
         let pa: PhysAddr = (*self).into();
         unsafe { core::slice::from_raw_parts_mut(pa.0 as *mut PageTableEntry, 512) }
     }
+    ///Get u8 array on `PhysPageNum`
     pub fn get_bytes_array(&self) -> &'static mut [u8] {
         let pa: PhysAddr = (*self).into();
         unsafe { core::slice::from_raw_parts_mut(pa.0 as *mut u8, 4096) }
     }
+    ///Get Get mutable reference to `PhysAddr` value on `PhysPageNum`
     pub fn get_mut<T>(&self) -> &'static mut T {
         let pa: PhysAddr = (*self).into();
         pa.get_mut()
     }
 }
-
+///Add value by one
 pub trait StepByOne {
+    ///Add value by one
     fn step(&mut self);
 }
 impl StepByOne for VirtPageNum {
@@ -205,6 +224,7 @@ impl StepByOne for PhysPageNum {
 }
 
 #[derive(Copy, Clone)]
+/// a simple range structure for type T
 pub struct SimpleRange<T>
 where
     T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
@@ -237,6 +257,7 @@ where
         SimpleRangeIterator::new(self.l, self.r)
     }
 }
+/// iterator for the simple range structure
 pub struct SimpleRangeIterator<T>
 where
     T: StepByOne + Copy + PartialEq + PartialOrd + Debug,
@@ -267,4 +288,5 @@ where
         }
     }
 }
+/// a simple range structure for virtual page number
 pub type VPNRange = SimpleRange<VirtPageNum>;
diff --git a/os/src/mm/frame_allocator.rs b/os/src/mm/frame_allocator.rs
index 163bb57..28b519c 100644
--- a/os/src/mm/frame_allocator.rs
+++ b/os/src/mm/frame_allocator.rs
@@ -1,15 +1,20 @@
+//! Implementation of [`FrameAllocator`] which
+//! controls all the frames in the operating system.
 use super::{PhysAddr, PhysPageNum};
 use crate::config::MEMORY_END;
-use crate::sync::UPIntrFreeCell;
+use crate::sync::UPSafeCell;
 use alloc::vec::Vec;
 use core::fmt::{self, Debug, Formatter};
 use lazy_static::*;
 
+/// manage a frame which has the same lifecycle as the tracker
 pub struct FrameTracker {
+    ///
     pub ppn: PhysPageNum,
 }
 
 impl FrameTracker {
+    ///Create an empty `FrameTracker`
     pub fn new(ppn: PhysPageNum) -> Self {
         // page cleaning
         let bytes_array = ppn.get_bytes_array();
@@ -35,10 +40,9 @@ impl Drop for FrameTracker {
 trait FrameAllocator {
     fn new() -> Self;
     fn alloc(&mut self) -> Option<PhysPageNum>;
-    fn alloc_more(&mut self, pages: usize) -> Option<Vec<PhysPageNum>>;
     fn dealloc(&mut self, ppn: PhysPageNum);
 }
-
+/// an implementation for frame allocator
 pub struct StackFrameAllocator {
     current: usize,
     end: usize,
@@ -49,7 +53,7 @@ impl StackFrameAllocator {
     pub fn init(&mut self, l: PhysPageNum, r: PhysPageNum) {
         self.current = l.0;
         self.end = r.0;
-        // println!("last {} Physical Frames.", self.end - self.current);
+        println!("last {} Physical Frames.", self.end - self.current);
     }
 }
 impl FrameAllocator for StackFrameAllocator {
@@ -70,16 +74,6 @@ impl FrameAllocator for StackFrameAllocator {
             Some((self.current - 1).into())
         }
     }
-    fn alloc_more(&mut self, pages: usize) -> Option<Vec<PhysPageNum>> {
-        if self.current + pages >= self.end {
-            None
-        } else {
-            self.current += pages;
-            let arr: Vec<usize> = (1..pages + 1).collect();
-            let v = arr.iter().map(|x| (self.current - x).into()).collect();
-            Some(v)
-        }
-    }
     fn dealloc(&mut self, ppn: PhysPageNum) {
         let ppn = ppn.0;
         // validity check
@@ -94,39 +88,34 @@ impl FrameAllocator for StackFrameAllocator {
 type FrameAllocatorImpl = StackFrameAllocator;
 
 lazy_static! {
-    pub static ref FRAME_ALLOCATOR: UPIntrFreeCell<FrameAllocatorImpl> =
-        unsafe { UPIntrFreeCell::new(FrameAllocatorImpl::new()) };
+    /// frame allocator instance through lazy_static!
+    pub static ref FRAME_ALLOCATOR: UPSafeCell<FrameAllocatorImpl> =
+        unsafe { UPSafeCell::new(FrameAllocatorImpl::new()) };
 }
-
+/// initiate the frame allocator using `ekernel` and `MEMORY_END`
 pub fn init_frame_allocator() {
-    extern "C" {
-        fn ekernel();
+    unsafe extern "C" {
+        safe fn ekernel();
     }
     FRAME_ALLOCATOR.exclusive_access().init(
         PhysAddr::from(ekernel as usize).ceil(),
         PhysAddr::from(MEMORY_END).floor(),
     );
 }
-
+/// allocate a frame
 pub fn frame_alloc() -> Option<FrameTracker> {
     FRAME_ALLOCATOR
         .exclusive_access()
         .alloc()
         .map(FrameTracker::new)
 }
-
-pub fn frame_alloc_more(num: usize) -> Option<Vec<FrameTracker>> {
-    FRAME_ALLOCATOR
-        .exclusive_access()
-        .alloc_more(num)
-        .map(|x| x.iter().map(|&t| FrameTracker::new(t)).collect())
-}
-
+/// deallocate a frame
 pub fn frame_dealloc(ppn: PhysPageNum) {
     FRAME_ALLOCATOR.exclusive_access().dealloc(ppn);
 }
 
 #[allow(unused)]
+/// a simple test for frame allocator
 pub fn frame_allocator_test() {
     let mut v: Vec<FrameTracker> = Vec::new();
     for i in 0..5 {
@@ -143,20 +132,3 @@ pub fn frame_allocator_test() {
     drop(v);
     println!("frame_allocator_test passed!");
 }
-
-#[allow(unused)]
-pub fn frame_allocator_alloc_more_test() {
-    let mut v: Vec<FrameTracker> = Vec::new();
-    let frames = frame_alloc_more(5).unwrap();
-    for frame in &frames {
-        println!("{:?}", frame);
-    }
-    v.extend(frames);
-    v.clear();
-    let frames = frame_alloc_more(5).unwrap();
-    for frame in &frames {
-        println!("{:?}", frame);
-    }
-    drop(v);
-    println!("frame_allocator_test passed!");
-}
diff --git a/os/src/mm/heap_allocator.rs b/os/src/mm/heap_allocator.rs
index 42a6d76..a6b413b 100644
--- a/os/src/mm/heap_allocator.rs
+++ b/os/src/mm/heap_allocator.rs
@@ -1,21 +1,25 @@
+//! The global allocator
 use crate::config::KERNEL_HEAP_SIZE;
 use buddy_system_allocator::LockedHeap;
+use core::ptr::addr_of_mut;
 
 #[global_allocator]
+/// heap allocator instance
 static HEAP_ALLOCATOR: LockedHeap = LockedHeap::empty();
 
 #[alloc_error_handler]
+/// panic when heap allocation error occurs
 pub fn handle_alloc_error(layout: core::alloc::Layout) -> ! {
     panic!("Heap allocation error, layout = {:?}", layout);
 }
-
+/// heap space ([u8; KERNEL_HEAP_SIZE])
 static mut HEAP_SPACE: [u8; KERNEL_HEAP_SIZE] = [0; KERNEL_HEAP_SIZE];
-
+/// initiate heap allocator
 pub fn init_heap() {
     unsafe {
         HEAP_ALLOCATOR
             .lock()
-            .init(HEAP_SPACE.as_ptr() as usize, KERNEL_HEAP_SIZE);
+            .init(addr_of_mut!(HEAP_SPACE) as usize, KERNEL_HEAP_SIZE);
     }
 }
 
@@ -23,9 +27,9 @@ pub fn init_heap() {
 pub fn heap_test() {
     use alloc::boxed::Box;
     use alloc::vec::Vec;
-    extern "C" {
-        fn sbss();
-        fn ebss();
+    unsafe extern "C" {
+        safe fn sbss();
+        safe fn ebss();
     }
     let bss_range = sbss as usize..ebss as usize;
     let a = Box::new(5);
diff --git a/os/src/mm/memory_set.rs b/os/src/mm/memory_set.rs
index d607c88..b1e5072 100644
--- a/os/src/mm/memory_set.rs
+++ b/os/src/mm/memory_set.rs
@@ -1,9 +1,11 @@
-use super::{frame_alloc, FrameTracker};
+//! Implementation of [`MapArea`] and [`MemorySet`].
+
+use super::{FrameTracker, frame_alloc};
 use super::{PTEFlags, PageTable, PageTableEntry};
 use super::{PhysAddr, PhysPageNum, VirtAddr, VirtPageNum};
 use super::{StepByOne, VPNRange};
-use crate::config::{MEMORY_END, MMIO, PAGE_SIZE, TRAMPOLINE};
-use crate::sync::UPIntrFreeCell;
+use crate::config::{MEMORY_END, MMIO, PAGE_SIZE, TRAMPOLINE, TRAP_CONTEXT, USER_STACK_SIZE};
+use crate::sync::UPSafeCell;
 use alloc::collections::BTreeMap;
 use alloc::sync::Arc;
 use alloc::vec::Vec;
@@ -11,40 +13,43 @@ use core::arch::asm;
 use lazy_static::*;
 use riscv::register::satp;
 
-extern "C" {
-    fn stext();
-    fn etext();
-    fn srodata();
-    fn erodata();
-    fn sdata();
-    fn edata();
-    fn sbss_with_stack();
-    fn ebss();
-    fn ekernel();
-    fn strampoline();
+unsafe extern "C" {
+    safe fn stext();
+    safe fn etext();
+    safe fn srodata();
+    safe fn erodata();
+    safe fn sdata();
+    safe fn edata();
+    safe fn sbss_with_stack();
+    safe fn ebss();
+    safe fn ekernel();
+    safe fn strampoline();
 }
 
 lazy_static! {
-    pub static ref KERNEL_SPACE: Arc<UPIntrFreeCell<MemorySet>> =
-        Arc::new(unsafe { UPIntrFreeCell::new(MemorySet::new_kernel()) });
+    /// a memory set instance through lazy_static! managing kernel space
+    pub static ref KERNEL_SPACE: Arc<UPSafeCell<MemorySet>> =
+        Arc::new(unsafe { UPSafeCell::new(MemorySet::new_kernel()) });
 }
-
+///Get kernelspace root ppn
 pub fn kernel_token() -> usize {
     KERNEL_SPACE.exclusive_access().token()
 }
-
+/// memory set structure, controls virtual-memory space
 pub struct MemorySet {
     page_table: PageTable,
     areas: Vec<MapArea>,
 }
 
 impl MemorySet {
+    ///Create an empty `MemorySet`
     pub fn new_bare() -> Self {
         Self {
             page_table: PageTable::new(),
             areas: Vec::new(),
         }
     }
+    ///Get pagetable `root_ppn`
     pub fn token(&self) -> usize {
         self.page_table.token()
     }
@@ -60,6 +65,7 @@ impl MemorySet {
             None,
         );
     }
+    ///Remove `MapArea` that starts with `start_vpn`
     pub fn remove_area_with_start_vpn(&mut self, start_vpn: VirtPageNum) {
         if let Some((idx, area)) = self
             .areas
@@ -71,10 +77,7 @@ impl MemorySet {
             self.areas.remove(idx);
         }
     }
-    /// Add a new MapArea into this MemorySet.
-    /// Assuming that there are no conflicts in the virtual address
-    /// space.
-    pub fn push(&mut self, mut map_area: MapArea, data: Option<&[u8]>) {
+    fn push(&mut self, mut map_area: MapArea, data: Option<&[u8]>) {
         map_area.map(&mut self.page_table);
         if let Some(data) = data {
             map_area.copy_data(&self.page_table, data);
@@ -95,14 +98,14 @@ impl MemorySet {
         // map trampoline
         memory_set.map_trampoline();
         // map kernel sections
-        // println!(".text [{:#x}, {:#x})", stext as usize, etext as usize);
-        // println!(".rodata [{:#x}, {:#x})", srodata as usize, erodata as usize);
-        // println!(".data [{:#x}, {:#x})", sdata as usize, edata as usize);
-        // println!(
-        //     ".bss [{:#x}, {:#x})",
-        //     sbss_with_stack as usize, ebss as usize
-        // );
-        // println!("mapping .text section");
+        println!(".text [{:#x}, {:#x})", stext as usize, etext as usize);
+        println!(".rodata [{:#x}, {:#x})", srodata as usize, erodata as usize);
+        println!(".data [{:#x}, {:#x})", sdata as usize, edata as usize);
+        println!(
+            ".bss [{:#x}, {:#x})",
+            sbss_with_stack as usize, ebss as usize
+        );
+        println!("mapping .text section");
         memory_set.push(
             MapArea::new(
                 (stext as usize).into(),
@@ -112,7 +115,7 @@ impl MemorySet {
             ),
             None,
         );
-        // println!("mapping .rodata section");
+        println!("mapping .rodata section");
         memory_set.push(
             MapArea::new(
                 (srodata as usize).into(),
@@ -122,7 +125,7 @@ impl MemorySet {
             ),
             None,
         );
-        // println!("mapping .data section");
+        println!("mapping .data section");
         memory_set.push(
             MapArea::new(
                 (sdata as usize).into(),
@@ -132,7 +135,7 @@ impl MemorySet {
             ),
             None,
         );
-        // println!("mapping .bss section");
+        println!("mapping .bss section");
         memory_set.push(
             MapArea::new(
                 (sbss_with_stack as usize).into(),
@@ -142,7 +145,7 @@ impl MemorySet {
             ),
             None,
         );
-        // println!("mapping physical memory");
+        println!("mapping physical memory");
         memory_set.push(
             MapArea::new(
                 (ekernel as usize).into(),
@@ -152,7 +155,7 @@ impl MemorySet {
             ),
             None,
         );
-        //println!("mapping memory-mapped registers");
+        println!("mapping memory-mapped registers");
         for pair in MMIO {
             memory_set.push(
                 MapArea::new(
@@ -166,8 +169,8 @@ impl MemorySet {
         }
         memory_set
     }
-    /// Include sections in elf and trampoline,
-    /// also returns user_sp_base and entry point.
+    /// Include sections in elf and trampoline and TrapContext and user stack,
+    /// also returns user_sp and entry point.
     pub fn from_elf(elf_data: &[u8]) -> (Self, usize, usize) {
         let mut memory_set = Self::new_bare();
         // map trampoline
@@ -203,15 +206,38 @@ impl MemorySet {
                 );
             }
         }
+        // map user stack with U flags
         let max_end_va: VirtAddr = max_end_vpn.into();
-        let mut user_stack_base: usize = max_end_va.into();
-        user_stack_base += PAGE_SIZE;
+        let mut user_stack_bottom: usize = max_end_va.into();
+        // guard page
+        user_stack_bottom += PAGE_SIZE;
+        let user_stack_top = user_stack_bottom + USER_STACK_SIZE;
+        memory_set.push(
+            MapArea::new(
+                user_stack_bottom.into(),
+                user_stack_top.into(),
+                MapType::Framed,
+                MapPermission::R | MapPermission::W | MapPermission::U,
+            ),
+            None,
+        );
+        // map TrapContext
+        memory_set.push(
+            MapArea::new(
+                TRAP_CONTEXT.into(),
+                TRAMPOLINE.into(),
+                MapType::Framed,
+                MapPermission::R | MapPermission::W,
+            ),
+            None,
+        );
         (
             memory_set,
-            user_stack_base,
+            user_stack_top,
             elf.header.pt2.entry_point() as usize,
         )
     }
+    ///Clone a same `MemorySet`
     pub fn from_existed_user(user_space: &MemorySet) -> MemorySet {
         let mut memory_set = Self::new_bare();
         // map trampoline
@@ -231,6 +257,7 @@ impl MemorySet {
         }
         memory_set
     }
+    ///Refresh TLB with `sfence.vma`
     pub fn activate(&self) {
         let satp = self.page_table.token();
         unsafe {
@@ -238,15 +265,17 @@ impl MemorySet {
             asm!("sfence.vma");
         }
     }
+    ///Translate throuth pagetable
     pub fn translate(&self, vpn: VirtPageNum) -> Option<PageTableEntry> {
         self.page_table.translate(vpn)
     }
+    ///Remove all `MapArea`
     pub fn recycle_data_pages(&mut self) {
         //*self = Self::new_bare();
         self.areas.clear();
     }
 }
-
+/// map area structure, controls a contiguous piece of virtual memory
 pub struct MapArea {
     vpn_range: VPNRange,
     data_frames: BTreeMap<VirtPageNum, FrameTracker>,
@@ -289,11 +318,6 @@ impl MapArea {
                 ppn = frame.ppn;
                 self.data_frames.insert(vpn, frame);
             }
-            MapType::Linear(pn_offset) => {
-                // check for sv39
-                assert!(vpn.0 < (1usize << 27));
-                ppn = PhysPageNum((vpn.0 as isize + pn_offset) as usize);
-            }
         }
         let pte_flags = PTEFlags::from_bits(self.map_perm.bits).unwrap();
         page_table.map(vpn, ppn, pte_flags);
@@ -339,42 +363,53 @@ impl MapArea {
 }
 
 #[derive(Copy, Clone, PartialEq, Debug)]
+/// map type for memory set: identical or framed
 pub enum MapType {
     Identical,
     Framed,
-    /// offset of page num
-    Linear(isize),
 }
 
 bitflags! {
+    /// map permission corresponding to that in pte: `R W X U`
     pub struct MapPermission: u8 {
+        ///Readable
         const R = 1 << 1;
+        ///Writable
         const W = 1 << 2;
+        ///Excutable
         const X = 1 << 3;
+        ///Accessible in U mode
         const U = 1 << 4;
     }
 }
 
 #[allow(unused)]
+///Check PageTable running correctly
 pub fn remap_test() {
     let mut kernel_space = KERNEL_SPACE.exclusive_access();
     let mid_text: VirtAddr = ((stext as usize + etext as usize) / 2).into();
     let mid_rodata: VirtAddr = ((srodata as usize + erodata as usize) / 2).into();
     let mid_data: VirtAddr = ((sdata as usize + edata as usize) / 2).into();
-    assert!(!kernel_space
-        .page_table
-        .translate(mid_text.floor())
-        .unwrap()
-        .writable(),);
-    assert!(!kernel_space
-        .page_table
-        .translate(mid_rodata.floor())
-        .unwrap()
-        .writable(),);
-    assert!(!kernel_space
-        .page_table
-        .translate(mid_data.floor())
-        .unwrap()
-        .executable(),);
+    assert!(
+        !kernel_space
+            .page_table
+            .translate(mid_text.floor())
+            .unwrap()
+            .writable(),
+    );
+    assert!(
+        !kernel_space
+            .page_table
+            .translate(mid_rodata.floor())
+            .unwrap()
+            .writable(),
+    );
+    assert!(
+        !kernel_space
+            .page_table
+            .translate(mid_data.floor())
+            .unwrap()
+            .executable(),
+    );
     println!("remap_test passed!");
 }
diff --git a/os/src/mm/mod.rs b/os/src/mm/mod.rs
index 642d0b7..3255725 100644
--- a/os/src/mm/mod.rs
+++ b/os/src/mm/mod.rs
@@ -1,19 +1,27 @@
+//! Memory management implementation
+//!
+//! SV39 page-based virtual-memory architecture for RV64 systems, and
+//! everything about memory management, like frame allocator, page table,
+//! map area and memory set, is implemented here.
+//!
+//! Every task or process has a memory_set to control its virtual memory.
 mod address;
 mod frame_allocator;
 mod heap_allocator;
 mod memory_set;
 mod page_table;
 
-pub use address::VPNRange;
+use address::VPNRange;
 pub use address::{PhysAddr, PhysPageNum, StepByOne, VirtAddr, VirtPageNum};
-pub use frame_allocator::{frame_alloc, frame_alloc_more, frame_dealloc, FrameTracker};
-pub use memory_set::{kernel_token, MapArea, MapPermission, MapType, MemorySet, KERNEL_SPACE};
+pub use frame_allocator::{FrameTracker, frame_alloc, frame_dealloc};
+pub use memory_set::remap_test;
+pub use memory_set::{KERNEL_SPACE, MapPermission, MemorySet, kernel_token};
 use page_table::PTEFlags;
 pub use page_table::{
-    translated_byte_buffer, translated_ref, translated_refmut, translated_str, PageTable,
-    PageTableEntry, UserBuffer,
+    PageTable, PageTableEntry, UserBuffer, UserBufferIterator, translated_byte_buffer,
+    translated_ref, translated_refmut, translated_str,
 };
-
+/// initiate heap allocator, frame allocator and kernel space
 pub fn init() {
     heap_allocator::init_heap();
     frame_allocator::init_frame_allocator();
diff --git a/os/src/mm/page_table.rs b/os/src/mm/page_table.rs
index dfaf4b6..f5fdf2b 100644
--- a/os/src/mm/page_table.rs
+++ b/os/src/mm/page_table.rs
@@ -1,4 +1,6 @@
-use super::{frame_alloc, FrameTracker, PhysAddr, PhysPageNum, StepByOne, VirtAddr, VirtPageNum};
+//! Implementation of [`PageTableEntry`] and [`PageTable`].
+
+use super::{FrameTracker, PhysAddr, PhysPageNum, StepByOne, VirtAddr, VirtPageNum, frame_alloc};
 use alloc::string::String;
 use alloc::vec;
 use alloc::vec::Vec;
@@ -19,39 +21,49 @@ bitflags! {
 
 #[derive(Copy, Clone)]
 #[repr(C)]
+/// page table entry structure
 pub struct PageTableEntry {
+    ///PTE
     pub bits: usize,
 }
 
 impl PageTableEntry {
+    ///Create a PTE from ppn
     pub fn new(ppn: PhysPageNum, flags: PTEFlags) -> Self {
         PageTableEntry {
             bits: ppn.0 << 10 | flags.bits as usize,
         }
     }
+    ///Return an empty PTE
     pub fn empty() -> Self {
         PageTableEntry { bits: 0 }
     }
+    ///Return 44bit ppn
     pub fn ppn(&self) -> PhysPageNum {
         (self.bits >> 10 & ((1usize << 44) - 1)).into()
     }
+    ///Return 10bit flag
     pub fn flags(&self) -> PTEFlags {
         PTEFlags::from_bits(self.bits as u8).unwrap()
     }
+    ///Check PTE valid
     pub fn is_valid(&self) -> bool {
         (self.flags() & PTEFlags::V) != PTEFlags::empty()
     }
+    ///Check PTE readable
     pub fn readable(&self) -> bool {
         (self.flags() & PTEFlags::R) != PTEFlags::empty()
     }
+    ///Check PTE writable
     pub fn writable(&self) -> bool {
         (self.flags() & PTEFlags::W) != PTEFlags::empty()
     }
+    ///Check PTE executable
     pub fn executable(&self) -> bool {
         (self.flags() & PTEFlags::X) != PTEFlags::empty()
     }
 }
-
+///Record root ppn and has the same lifetime as 1 and 2 level `PageTableEntry`
 pub struct PageTable {
     root_ppn: PhysPageNum,
     frames: Vec<FrameTracker>,
@@ -59,6 +71,7 @@ pub struct PageTable {
 
 /// Assume that it won't oom when creating/mapping.
 impl PageTable {
+    /// Create an empty `PageTable`
     pub fn new() -> Self {
         let frame = frame_alloc().unwrap();
         PageTable {
@@ -73,6 +86,7 @@ impl PageTable {
             frames: Vec::new(),
         }
     }
+    /// Find phsical address by virtual address, create a frame if not exist
     fn find_pte_create(&mut self, vpn: VirtPageNum) -> Option<&mut PageTableEntry> {
         let idxs = vpn.indexes();
         let mut ppn = self.root_ppn;
@@ -92,6 +106,7 @@ impl PageTable {
         }
         result
     }
+    /// Find phsical address by virtual address
     fn find_pte(&self, vpn: VirtPageNum) -> Option<&mut PageTableEntry> {
         let idxs = vpn.indexes();
         let mut ppn = self.root_ppn;
@@ -110,20 +125,24 @@ impl PageTable {
         result
     }
     #[allow(unused)]
+    /// Create a mapping form `vpn` to `ppn`
     pub fn map(&mut self, vpn: VirtPageNum, ppn: PhysPageNum, flags: PTEFlags) {
         let pte = self.find_pte_create(vpn).unwrap();
         assert!(!pte.is_valid(), "vpn {:?} is mapped before mapping", vpn);
         *pte = PageTableEntry::new(ppn, flags | PTEFlags::V);
     }
     #[allow(unused)]
+    /// Delete a mapping form `vpn`
     pub fn unmap(&mut self, vpn: VirtPageNum) {
         let pte = self.find_pte(vpn).unwrap();
         assert!(pte.is_valid(), "vpn {:?} is invalid before unmapping", vpn);
         *pte = PageTableEntry::empty();
     }
+    /// Translate `VirtPageNum` to `PageTableEntry`
     pub fn translate(&self, vpn: VirtPageNum) -> Option<PageTableEntry> {
         self.find_pte(vpn).map(|pte| *pte)
     }
+    /// Translate `VirtAddr` to `PhysAddr`
     pub fn translate_va(&self, va: VirtAddr) -> Option<PhysAddr> {
         self.find_pte(va.clone().floor()).map(|pte| {
             let aligned_pa: PhysAddr = pte.ppn().into();
@@ -132,11 +151,12 @@ impl PageTable {
             (aligned_pa_usize + offset).into()
         })
     }
+    /// Get root ppn
     pub fn token(&self) -> usize {
         8usize << 60 | self.root_ppn.0
     }
 }
-
+/// Translate a pointer to a mutable u8 Vec through page table
 pub fn translated_byte_buffer(token: usize, ptr: *const u8, len: usize) -> Vec<&'static mut [u8]> {
     let page_table = PageTable::from_token(token);
     let mut start = ptr as usize;
@@ -159,7 +179,7 @@ pub fn translated_byte_buffer(token: usize, ptr: *const u8, len: usize) -> Vec<&
     v
 }
 
-/// Load a string from other address spaces into kernel space without an end `\0`.
+/// Translate a pointer to a mutable u8 Vec end with `\0` through page table to a `String`
 pub fn translated_str(token: usize, ptr: *const u8) -> String {
     let page_table = PageTable::from_token(token);
     let mut string = String::new();
@@ -178,6 +198,8 @@ pub fn translated_str(token: usize, ptr: *const u8) -> String {
     string
 }
 
+#[allow(unused)]
+///Translate a generic through page table and return a reference
 pub fn translated_ref<T>(token: usize, ptr: *const T) -> &'static T {
     let page_table = PageTable::from_token(token);
     page_table
@@ -185,7 +207,7 @@ pub fn translated_ref<T>(token: usize, ptr: *const T) -> &'static T {
         .unwrap()
         .get_ref()
 }
-
+///Translate a generic through page table and return a mutable reference
 pub fn translated_refmut<T>(token: usize, ptr: *mut T) -> &'static mut T {
     let page_table = PageTable::from_token(token);
     let va = ptr as usize;
@@ -194,15 +216,18 @@ pub fn translated_refmut<T>(token: usize, ptr: *mut T) -> &'static mut T {
         .unwrap()
         .get_mut()
 }
-
+///Array of u8 slice that user communicate with os
 pub struct UserBuffer {
+    ///U8 vec
     pub buffers: Vec<&'static mut [u8]>,
 }
 
 impl UserBuffer {
+    ///Create a `UserBuffer` by parameter
     pub fn new(buffers: Vec<&'static mut [u8]>) -> Self {
         Self { buffers }
     }
+    ///Length of `UserBuffer`
     pub fn len(&self) -> usize {
         let mut total: usize = 0;
         for b in self.buffers.iter() {
@@ -223,7 +248,7 @@ impl IntoIterator for UserBuffer {
         }
     }
 }
-
+/// Iterator of `UserBuffer`
 pub struct UserBufferIterator {
     buffers: Vec<&'static mut [u8]>,
     current_buffer: usize,
diff --git a/os/src/net/mod.rs b/os/src/net/mod.rs
deleted file mode 100644
index 469a365..0000000
--- a/os/src/net/mod.rs
+++ /dev/null
@@ -1,136 +0,0 @@
-pub mod port_table;
-pub mod socket;
-pub mod tcp;
-pub mod udp;
-
-pub use lose_net_stack::IPv4;
-
-use alloc::{sync::Arc, vec};
-use lose_net_stack::{results::Packet, LoseStack, MacAddress, TcpFlags};
-
-use crate::{
-    drivers::NET_DEVICE,
-    net::socket::{get_socket, push_data},
-    sync::UPIntrFreeCell,
-};
-
-use self::{port_table::check_accept, socket::set_s_a_by_index};
-
-pub struct NetStack(UPIntrFreeCell<LoseStack>);
-
-impl NetStack {
-    pub fn new() -> Self {
-        unsafe {
-            NetStack(UPIntrFreeCell::new(LoseStack::new(
-                IPv4::new(10, 0, 2, 15),
-                MacAddress::new([0x52, 0x54, 0x00, 0x12, 0x34, 0x56]),
-            )))
-        }
-    }
-}
-
-lazy_static::lazy_static! {
-    static ref LOSE_NET_STACK: Arc<NetStack> = Arc::new(NetStack::new());
-}
-
-pub fn net_interrupt_handler() {
-    let mut recv_buf = vec![0u8; 1024];
-
-    let len = NET_DEVICE.receive(&mut recv_buf);
-
-    let packet = LOSE_NET_STACK
-        .0
-        .exclusive_access()
-        .analysis(&recv_buf[..len]);
-
-    // println!("[kernel] receive a packet");
-    // hexdump(&recv_buf[..len]);
-
-    match packet {
-        Packet::ARP(arp_packet) => {
-            let lose_stack = LOSE_NET_STACK.0.exclusive_access();
-            let reply_packet = arp_packet
-                .reply_packet(lose_stack.ip, lose_stack.mac)
-                .expect("can't build reply");
-            let reply_data = reply_packet.build_data();
-            NET_DEVICE.transmit(&reply_data)
-        }
-
-        Packet::UDP(udp_packet) => {
-            let target = udp_packet.source_ip;
-            let lport = udp_packet.dest_port;
-            let rport = udp_packet.source_port;
-
-            if let Some(socket_index) = get_socket(target, lport, rport) {
-                push_data(socket_index, udp_packet.data.to_vec());
-            }
-        }
-
-        Packet::TCP(tcp_packet) => {
-            let target = tcp_packet.source_ip;
-            let lport = tcp_packet.dest_port;
-            let rport = tcp_packet.source_port;
-            let flags = tcp_packet.flags;
-
-            if flags.contains(TcpFlags::S) {
-                // if it has a port to accept, then response the request
-                if check_accept(lport, &tcp_packet).is_some() {
-                    let mut reply_packet = tcp_packet.ack();
-                    reply_packet.flags = TcpFlags::S | TcpFlags::A;
-                    NET_DEVICE.transmit(&reply_packet.build_data());
-                }
-                return;
-            } else if tcp_packet.flags.contains(TcpFlags::F) {
-                // tcp disconnected
-                let reply_packet = tcp_packet.ack();
-                NET_DEVICE.transmit(&reply_packet.build_data());
-
-                let mut end_packet = reply_packet.ack();
-                end_packet.flags |= TcpFlags::F;
-                NET_DEVICE.transmit(&end_packet.build_data());
-            } else if tcp_packet.flags.contains(TcpFlags::A) && tcp_packet.data_len == 0 {
-                return;
-            }
-
-            if let Some(socket_index) = get_socket(target, lport, rport) {
-                push_data(socket_index, tcp_packet.data.to_vec());
-                set_s_a_by_index(socket_index, tcp_packet.seq, tcp_packet.ack);
-            }
-        }
-        _ => {}
-    }
-}
-
-#[allow(unused)]
-pub fn hexdump(data: &[u8]) {
-    const PRELAND_WIDTH: usize = 70;
-    println!("[kernel] {:-^1$}", " hexdump ", PRELAND_WIDTH);
-    for offset in (0..data.len()).step_by(16) {
-        print!("[kernel] ");
-        for i in 0..16 {
-            if offset + i < data.len() {
-                print!("{:02x} ", data[offset + i]);
-            } else {
-                print!("{:02} ", "");
-            }
-        }
-
-        print!("{:>6}", ' ');
-
-        for i in 0..16 {
-            if offset + i < data.len() {
-                let c = data[offset + i];
-                if c >= 0x20 && c <= 0x7e {
-                    print!("{}", c as char);
-                } else {
-                    print!(".");
-                }
-            } else {
-                print!("{:02} ", "");
-            }
-        }
-
-        println!("");
-    }
-    println!("[kernel] {:-^1$}", " hexdump end ", PRELAND_WIDTH);
-}
diff --git a/os/src/net/port_table.rs b/os/src/net/port_table.rs
deleted file mode 100644
index bcda046..0000000
--- a/os/src/net/port_table.rs
+++ /dev/null
@@ -1,141 +0,0 @@
-use alloc::{sync::Arc, vec::Vec};
-use lazy_static::lazy_static;
-use lose_net_stack::packets::tcp::TCPPacket;
-
-use crate::fs::File;
-use crate::sync::UPIntrFreeCell;
-use crate::task::TaskControlBlock;
-
-use super::tcp::TCP;
-
-pub struct Port {
-    pub port: u16,
-    pub receivable: bool,
-    pub schedule: Option<Arc<TaskControlBlock>>,
-}
-
-lazy_static! {
-    static ref LISTEN_TABLE: UPIntrFreeCell<Vec<Option<Port>>> =
-        unsafe { UPIntrFreeCell::new(Vec::new()) };
-}
-
-pub fn listen(port: u16) -> Option<usize> {
-    let mut listen_table = LISTEN_TABLE.exclusive_access();
-    let mut index = usize::MAX;
-    for i in 0..listen_table.len() {
-        if listen_table[i].is_none() {
-            index = i;
-            break;
-        }
-    }
-
-    let listen_port = Port {
-        port,
-        receivable: false,
-        schedule: None,
-    };
-
-    if index == usize::MAX {
-        listen_table.push(Some(listen_port));
-        Some(listen_table.len() - 1)
-    } else {
-        listen_table[index] = Some(listen_port);
-        Some(index)
-    }
-}
-
-// can accept request
-pub fn accept(listen_index: usize, task: Arc<TaskControlBlock>) {
-    let mut listen_table = LISTEN_TABLE.exclusive_access();
-    assert!(listen_index < listen_table.len());
-    let listen_port = listen_table[listen_index].as_mut();
-    assert!(listen_port.is_some());
-    let listen_port = listen_port.unwrap();
-    listen_port.receivable = true;
-    listen_port.schedule = Some(task);
-}
-
-pub fn port_acceptable(listen_index: usize) -> bool {
-    let mut listen_table = LISTEN_TABLE.exclusive_access();
-    assert!(listen_index < listen_table.len());
-
-    let listen_port = listen_table[listen_index].as_mut();
-    listen_port.map_or(false, |x| x.receivable)
-}
-
-// check whether it can accept request
-pub fn check_accept(port: u16, tcp_packet: &TCPPacket) -> Option<()> {
-    LISTEN_TABLE.exclusive_session(|listen_table| {
-        let mut listen_ports: Vec<&mut Option<Port>> = listen_table
-            .iter_mut()
-            .filter(|x| match x {
-                Some(t) => t.port == port && t.receivable == true,
-                None => false,
-            })
-            .collect();
-        if listen_ports.len() == 0 {
-            None
-        } else {
-            let listen_port = listen_ports[0].as_mut().unwrap();
-            let task = listen_port.schedule.clone().unwrap();
-            // wakeup_task(Arc::clone(&listen_port.schedule.clone().unwrap()));
-            listen_port.schedule = None;
-            listen_port.receivable = false;
-
-            accept_connection(port, tcp_packet, task);
-            Some(())
-        }
-    })
-}
-
-pub fn accept_connection(_port: u16, tcp_packet: &TCPPacket, task: Arc<TaskControlBlock>) {
-    let process = task.process.upgrade().unwrap();
-    let mut inner = process.inner_exclusive_access();
-    let fd = inner.alloc_fd();
-
-    let tcp_socket = TCP::new(
-        tcp_packet.source_ip,
-        tcp_packet.dest_port,
-        tcp_packet.source_port,
-        tcp_packet.seq,
-        tcp_packet.ack,
-    );
-
-    inner.fd_table[fd] = Some(Arc::new(tcp_socket));
-
-    let cx = task.inner_exclusive_access().get_trap_cx();
-    cx.x[10] = fd;
-}
-
-// store in the fd_table, delete the listen table when close the application.
-pub struct PortFd(usize);
-
-impl PortFd {
-    pub fn new(port_index: usize) -> Self {
-        PortFd(port_index)
-    }
-}
-
-impl Drop for PortFd {
-    fn drop(&mut self) {
-        LISTEN_TABLE.exclusive_access()[self.0] = None
-    }
-}
-
-impl File for PortFd {
-    fn readable(&self) -> bool {
-        false
-    }
-
-    fn writable(&self) -> bool {
-        false
-    }
-
-    fn read(&self, _buf: crate::mm::UserBuffer) -> usize {
-        0
-    }
-
-    fn write(&self, _buf: crate::mm::UserBuffer) -> usize {
-        0
-    }
-}
diff --git a/os/src/net/socket.rs b/os/src/net/socket.rs
deleted file mode 100644
index a37ba82..0000000
--- a/os/src/net/socket.rs
+++ /dev/null
@@ -1,123 +0,0 @@
-use alloc::collections::VecDeque;
-use alloc::vec::Vec;
-use lazy_static::lazy_static;
-use lose_net_stack::IPv4;
-
-use crate::sync::UPIntrFreeCell;
-
-// TODO: specify the protocol, TCP or UDP
-pub struct Socket {
-    pub raddr: IPv4,                // remote address
-    pub lport: u16,                 // local port
-    pub rport: u16,                 // rempote port
-    pub buffers: VecDeque<Vec<u8>>, // datas
-    pub seq: u32,
-    pub ack: u32,
-}
-
-lazy_static! {
-    static ref SOCKET_TABLE: UPIntrFreeCell<Vec<Option<Socket>>> =
-        unsafe { UPIntrFreeCell::new(Vec::new()) };
-}
-
-/// get the seq and ack by socket index
-pub fn get_s_a_by_index(index: usize) -> Option<(u32, u32)> {
-    let socket_table = SOCKET_TABLE.exclusive_access();
-
-    assert!(index < socket_table.len());
-
-    socket_table.get(index).map_or(None, |x| match x {
-        Some(x) => Some((x.seq, x.ack)),
-        None => None,
-    })
-}
-
-pub fn set_s_a_by_index(index: usize, seq: u32, ack: u32) {
-    let mut socket_table = SOCKET_TABLE.exclusive_access();
-
-    assert!(socket_table.len() > index);
-    assert!(socket_table[index].is_some());
-
-    let sock = socket_table[index].as_mut().unwrap();
-
-    sock.ack = ack;
-    sock.seq = seq;
-}
-
-pub fn get_socket(raddr: IPv4, lport: u16, rport: u16) -> Option<usize> {
-    let socket_table = SOCKET_TABLE.exclusive_access();
-    for i in 0..socket_table.len() {
-        let sock = &socket_table[i];
-        if sock.is_none() {
-            continue;
-        }
-
-        let sock = sock.as_ref().unwrap();
-        if sock.raddr == raddr && sock.lport == lport && sock.rport == rport {
-            return Some(i);
-        }
-    }
-    None
-}
-
-pub fn add_socket(raddr: IPv4, lport: u16, rport: u16) -> Option<usize> {
-    if get_socket(raddr, lport, rport).is_some() {
-        return None;
-    }
-
-    let mut socket_table = SOCKET_TABLE.exclusive_access();
-    let mut index = usize::MAX;
-    for i in 0..socket_table.len() {
-        if socket_table[i].is_none() {
-            index = i;
-            break;
-        }
-    }
-
-    let socket = Socket {
-        raddr,
-        lport,
-        rport,
-        buffers: VecDeque::new(),
-        seq: 0,
-        ack: 0,
-    };
-
-    if index == usize::MAX {
-        socket_table.push(Some(socket));
-        Some(socket_table.len() - 1)
-    } else {
-        socket_table[index] = Some(socket);
-        Some(index)
-    }
-}
-
-pub fn remove_socket(index: usize) {
-    let mut socket_table = SOCKET_TABLE.exclusive_access();
-
-    assert!(socket_table.len() > index);
-
-    socket_table[index] = None;
-}
-
-pub fn push_data(index: usize, data: Vec<u8>) {
-    let mut socket_table = SOCKET_TABLE.exclusive_access();
-
-    assert!(socket_table.len() > index);
-    assert!(socket_table[index].is_some());
-
-    socket_table[index]
-        .as_mut()
-        .unwrap()
-        .buffers
-        .push_back(data);
-}
-
-pub fn pop_data(index: usize) -> Option<Vec<u8>> {
-    let mut socket_table = SOCKET_TABLE.exclusive_access();
-
-    assert!(socket_table.len() > index);
-    assert!(socket_table[index].is_some());
-
-    socket_table[index].as_mut().unwrap().buffers.pop_front()
-}
diff --git a/os/src/net/tcp.rs b/os/src/net/tcp.rs
deleted file mode 100644
index d1f7bd2..0000000
--- a/os/src/net/tcp.rs
+++ /dev/null
@@ -1,113 +0,0 @@
-use alloc::vec;
-use lose_net_stack::packets::tcp::TCPPacket;
-use lose_net_stack::IPv4;
-use lose_net_stack::MacAddress;
-use lose_net_stack::TcpFlags;
-
-use crate::{drivers::NET_DEVICE, fs::File};
-
-use super::socket::get_s_a_by_index;
-use super::{
-    net_interrupt_handler,
-    socket::{add_socket, pop_data, remove_socket},
-    LOSE_NET_STACK,
-};
-
-// add tcp packet info to this structure
-pub struct TCP {
-    pub target: IPv4,
-    pub sport: u16,
-    pub dport: u16,
-    pub seq: u32,
-    pub ack: u32,
-    pub socket_index: usize,
-}
-
-impl TCP {
-    pub fn new(target: IPv4, sport: u16, dport: u16, seq: u32, ack: u32) -> Self {
-        let index = add_socket(target, sport, dport).expect("can't add socket");
-
-        Self {
-            target,
-            sport,
-            dport,
-            seq,
-            ack,
-            socket_index: index,
-        }
-    }
-}
-
-impl File for TCP {
-    fn readable(&self) -> bool {
-        true
-    }
-
-    fn writable(&self) -> bool {
-        true
-    }
-
-    fn read(&self, mut buf: crate::mm::UserBuffer) -> usize {
-        loop {
-            if let Some(data) = pop_data(self.socket_index) {
-                let data_len = data.len();
-                let mut left = 0;
-                for i in 0..buf.buffers.len() {
-                    let buffer_i_len = buf.buffers[i].len().min(data_len - left);
-
-                    buf.buffers[i][..buffer_i_len]
-                        .copy_from_slice(&data[left..(left + buffer_i_len)]);
-
-                    left += buffer_i_len;
-                    if left == data_len {
-                        break;
-                    }
-                }
-                return left;
-            } else {
-                net_interrupt_handler();
-            }
-        }
-    }
-
-    fn write(&self, buf: crate::mm::UserBuffer) -> usize {
-        let lose_net_stack = LOSE_NET_STACK.0.exclusive_access();
-
-        let mut data = vec![0u8; buf.len()];
-
-        let mut left = 0;
-        for i in 0..buf.buffers.len() {
-            data[left..(left + buf.buffers[i].len())].copy_from_slice(buf.buffers[i]);
-            left += buf.buffers[i].len();
-        }
-
-        let len = data.len();
-
-        // get sock and sequence
-        let (ack, seq) = get_s_a_by_index(self.socket_index).map_or((0, 0), |x| x);
-
-        let tcp_packet = TCPPacket {
-            source_ip: lose_net_stack.ip,
-            source_mac: lose_net_stack.mac,
-            source_port: self.sport,
-            dest_ip: self.target,
-            dest_mac: MacAddress::new([0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
-            dest_port: self.dport,
-            data_len: len,
-            seq,
-            ack,
-            flags: TcpFlags::A,
-            win: 65535,
-            urg: 0,
-            data: data.as_ref(),
-        };
-        NET_DEVICE.transmit(&tcp_packet.build_data());
-        len
-    }
-}
-
-impl Drop for TCP {
-    fn drop(&mut self) {
-        remove_socket(self.socket_index)
-    }
-}
diff --git a/os/src/net/udp.rs b/os/src/net/udp.rs
deleted file mode 100644
index f343ed4..0000000
--- a/os/src/net/udp.rs
+++ /dev/null
@@ -1,95 +0,0 @@
-use super::net_interrupt_handler;
-use super::socket::{add_socket, pop_data, remove_socket};
-use super::LOSE_NET_STACK;
-use super::NET_DEVICE;
-use crate::fs::File;
-use alloc::vec;
-use lose_net_stack::packets::udp::UDPPacket;
-use lose_net_stack::IPv4;
-use lose_net_stack::MacAddress;
-
-pub struct UDP {
-    pub target: IPv4,
-    pub sport: u16,
-    pub dport: u16,
-    pub socket_index: usize,
-}
-
-impl UDP {
-    pub fn new(target: IPv4, sport: u16, dport: u16) -> Self {
-        let index = add_socket(target, sport, dport).expect("can't add socket");
-
-        Self {
-            target,
-            sport,
-            dport,
-            socket_index: index,
-        }
-    }
-}
-
-impl File for UDP {
-    fn readable(&self) -> bool {
-        true
-    }
-
-    fn writable(&self) -> bool {
-        true
-    }
-
-    fn read(&self, mut buf: crate::mm::UserBuffer) -> usize {
-        loop {
-            if let Some(data) = pop_data(self.socket_index) {
-                let data_len = data.len();
-                let mut left = 0;
-                for i in 0..buf.buffers.len() {
-                    let buffer_i_len = buf.buffers[i].len().min(data_len - left);
-
-                    buf.buffers[i][..buffer_i_len]
-                        .copy_from_slice(&data[left..(left + buffer_i_len)]);
-
-                    left += buffer_i_len;
-                    if left == data_len {
-                        break;
-                    }
-                }
-                return left;
-            } else {
-                net_interrupt_handler();
-            }
-        }
-    }
-
-    fn write(&self, buf: crate::mm::UserBuffer) -> usize {
-        let lose_net_stack = LOSE_NET_STACK.0.exclusive_access();
-
-        let mut data = vec![0u8; buf.len()];
-
-        let mut left = 0;
-        for i in 0..buf.buffers.len() {
-            data[left..(left + buf.buffers[i].len())].copy_from_slice(buf.buffers[i]);
-            left += buf.buffers[i].len();
-        }
-
-        let len = data.len();
-
-        let udp_packet = UDPPacket::new(
-            lose_net_stack.ip,
-            lose_net_stack.mac,
-            self.sport,
-            self.target,
-            MacAddress::new([0xff, 0xff, 0xff, 0xff, 0xff, 0xff]),
-            self.dport,
-            len,
-            data.as_ref(),
-        );
-        NET_DEVICE.transmit(&udp_packet.build_data());
-        len
-    }
-}
-
-impl Drop for UDP {
-    fn drop(&mut self) {
-        remove_socket(self.socket_index)
-    }
-}
diff --git a/os/src/sbi.rs b/os/src/sbi.rs
index 2c0aaa5..a73476f 100644
--- a/os/src/sbi.rs
+++ b/os/src/sbi.rs
@@ -1,3 +1,18 @@
+//! SBI call wrappers
+#![allow(unused)]
+
+/// use sbi call to putchar in console (qemu uart handler)
+pub fn console_putchar(c: usize) {
+    #[allow(deprecated)]
+    sbi_rt::legacy::console_putchar(c);
+}
+
+/// use sbi call to getchar from console (qemu uart handler)
+pub fn console_getchar() -> usize {
+    #[allow(deprecated)]
+    sbi_rt::legacy::console_getchar()
+}
+
 /// use sbi call to set timer
 pub fn set_timer(timer: usize) {
     sbi_rt::set_timer(timer as _);
@@ -5,7 +20,7 @@ pub fn set_timer(timer: usize) {
 
 /// use sbi call to shutdown the kernel
 pub fn shutdown(failure: bool) -> ! {
-    use sbi_rt::{system_reset, NoReason, Shutdown, SystemFailure};
+    use sbi_rt::{NoReason, Shutdown, SystemFailure, system_reset};
     if !failure {
         system_reset(Shutdown, NoReason);
     } else {
diff --git a/os/src/sync/condvar.rs b/os/src/sync/condvar.rs
deleted file mode 100644
index d13652f..0000000
--- a/os/src/sync/condvar.rs
+++ /dev/null
@@ -1,58 +0,0 @@
-use crate::sync::{Mutex, UPIntrFreeCell};
-use crate::task::{
-    block_current_and_run_next, block_current_task, current_task, wakeup_task, TaskContext,
-    TaskControlBlock,
-};
-use alloc::{collections::VecDeque, sync::Arc};
-
-pub struct Condvar {
-    pub inner: UPIntrFreeCell<CondvarInner>,
-}
-
-pub struct CondvarInner {
-    pub wait_queue: VecDeque<Arc<TaskControlBlock>>,
-}
-
-impl Condvar {
-    pub fn new() -> Self {
-        Self {
-            inner: unsafe {
-                UPIntrFreeCell::new(CondvarInner {
-                    wait_queue: VecDeque::new(),
-                })
-            },
-        }
-    }
-
-    pub fn signal(&self) {
-        let mut inner = self.inner.exclusive_access();
-        if let Some(task) = inner.wait_queue.pop_front() {
-            wakeup_task(task);
-        }
-    }
-
-    /*
-    pub fn wait(&self) {
-        let mut inner = self.inner.exclusive_access();
-        inner.wait_queue.push_back(current_task().unwrap());
-        drop(inner);
-        block_current_and_run_next();
-    }
-    */
-
-    pub fn wait_no_sched(&self) -> *mut TaskContext {
-        self.inner.exclusive_session(|inner| {
-            inner.wait_queue.push_back(current_task().unwrap());
-        });
-        block_current_task()
-    }
-
-    pub fn wait_with_mutex(&self, mutex: Arc<dyn Mutex>) {
-        mutex.unlock();
-        self.inner.exclusive_session(|inner| {
-            inner.wait_queue.push_back(current_task().unwrap());
-        });
-        block_current_and_run_next();
-        mutex.lock();
-    }
-}
diff --git a/os/src/sync/mod.rs b/os/src/sync/mod.rs
index d9a00b5..aa04db3 100644
--- a/os/src/sync/mod.rs
+++ b/os/src/sync/mod.rs
@@ -1,9 +1,4 @@
-mod condvar;
-mod mutex;
-mod semaphore;
+//! Synchronization and interior mutability primitives
 mod up;
 
-pub use condvar::Condvar;
-pub use mutex::{Mutex, MutexBlocking, MutexSpin};
-pub use semaphore::Semaphore;
-pub use up::{UPIntrFreeCell, UPIntrRefMut};
+pub use up::UPSafeCell;
diff --git a/os/src/sync/mutex.rs b/os/src/sync/mutex.rs
deleted file mode 100644
index aaf1571..0000000
--- a/os/src/sync/mutex.rs
+++ /dev/null
@@ -1,88 +0,0 @@
-use super::UPIntrFreeCell;
-use crate::task::TaskControlBlock;
-use crate::task::{block_current_and_run_next, suspend_current_and_run_next};
-use crate::task::{current_task, wakeup_task};
-use alloc::{collections::VecDeque, sync::Arc};
-
-pub trait Mutex: Sync + Send {
-    fn lock(&self);
-    fn unlock(&self);
-}
-
-pub struct MutexSpin {
-    locked: UPIntrFreeCell<bool>,
-}
-
-impl MutexSpin {
-    pub fn new() -> Self {
-        Self {
-            locked: unsafe { UPIntrFreeCell::new(false) },
-        }
-    }
-}
-
-impl Mutex for MutexSpin {
-    fn lock(&self) {
-        loop {
-            let mut locked = self.locked.exclusive_access();
-            if *locked {
-                drop(locked);
-                suspend_current_and_run_next();
-                continue;
-            } else {
-                *locked = true;
-                return;
-            }
-        }
-    }
-
-    fn unlock(&self) {
-        let mut locked = self.locked.exclusive_access();
-        *locked = false;
-    }
-}
-
-pub struct MutexBlocking {
-    inner: UPIntrFreeCell<MutexBlockingInner>,
-}
-
-pub struct MutexBlockingInner {
-    locked: bool,
-    wait_queue: VecDeque<Arc<TaskControlBlock>>,
-}
-
-impl MutexBlocking {
-    pub fn new() -> Self {
-        Self {
-            inner: unsafe {
-                UPIntrFreeCell::new(MutexBlockingInner {
-                    locked: false,
-                    wait_queue: VecDeque::new(),
-                })
-            },
-        }
-    }
-}
-
-impl Mutex for MutexBlocking {
-    fn lock(&self) {
-        let mut mutex_inner = self.inner.exclusive_access();
-        if mutex_inner.locked {
-            mutex_inner.wait_queue.push_back(current_task().unwrap());
-            drop(mutex_inner);
-            block_current_and_run_next();
-        } else {
-            mutex_inner.locked = true;
-        }
-    }
-
-    fn unlock(&self) {
-        let mut mutex_inner = self.inner.exclusive_access();
-        assert!(mutex_inner.locked);
-        if let Some(waking_task) = mutex_inner.wait_queue.pop_front() {
-            wakeup_task(waking_task);
-        } else {
-            mutex_inner.locked = false;
-        }
-    }
-}
diff --git a/os/src/sync/semaphore.rs b/os/src/sync/semaphore.rs
deleted file mode 100644
index bdad319..0000000
--- a/os/src/sync/semaphore.rs
+++ /dev/null
@@ -1,45 +0,0 @@
-use crate::sync::UPIntrFreeCell;
-use crate::task::{block_current_and_run_next, current_task, wakeup_task, TaskControlBlock};
-use alloc::{collections::VecDeque, sync::Arc};
-
-pub struct Semaphore {
-    pub inner: UPIntrFreeCell<SemaphoreInner>,
-}
-
-pub struct SemaphoreInner {
-    pub count: isize,
-    pub wait_queue: VecDeque<Arc<TaskControlBlock>>,
-}
-
-impl Semaphore {
-    pub fn new(res_count: usize) -> Self {
-        Self {
-            inner: unsafe {
-                UPIntrFreeCell::new(SemaphoreInner {
-                    count: res_count as isize,
-                    wait_queue: VecDeque::new(),
-                })
-            },
-        }
-    }
-
-    pub fn up(&self) {
-        let mut inner = self.inner.exclusive_access();
-        inner.count += 1;
-        if inner.count <= 0 {
-            if let Some(task) = inner.wait_queue.pop_front() {
-                wakeup_task(task);
-            }
-        }
-    }
-
-    pub fn down(&self) {
-        let mut inner = self.inner.exclusive_access();
-        inner.count -= 1;
-        if inner.count < 0 {
-            inner.wait_queue.push_back(current_task().unwrap());
-            drop(inner);
-            block_current_and_run_next();
-        }
-    }
-}
diff --git a/os/src/sync/up.rs b/os/src/sync/up.rs
index 6c7a0f4..955b9dc 100644
--- a/os/src/sync/up.rs
+++ b/os/src/sync/up.rs
@@ -1,9 +1,6 @@
-use core::cell::{RefCell, RefMut, UnsafeCell};
-use core::ops::{Deref, DerefMut};
-use lazy_static::*;
-use riscv::register::sstatus;
+//! Uniprocessor interior mutability primitives
+use core::cell::{RefCell, RefMut};
 
-/*
 /// Wrap a static data structure inside it so that we are
 /// able to access it without any `unsafe`.
 ///
@@ -26,115 +23,8 @@ impl<T> UPSafeCell<T> {
             inner: RefCell::new(value),
         }
     }
-    /// Panic if the data has been borrowed.
+    /// Exclusive access inner data in UPSafeCell. Panic if the data has been borrowed.
     pub fn exclusive_access(&self) -> RefMut<'_, T> {
         self.inner.borrow_mut()
     }
 }
-*/
-
-pub struct UPSafeCellRaw<T> {
-    inner: UnsafeCell<T>,
-}
-
-unsafe impl<T> Sync for UPSafeCellRaw<T> {}
-
-impl<T> UPSafeCellRaw<T> {
-    pub unsafe fn new(value: T) -> Self {
-        Self {
-            inner: UnsafeCell::new(value),
-        }
-    }
-    pub fn get_mut(&self) -> &mut T {
-        unsafe { &mut (*self.inner.get()) }
-    }
-}
-
-pub struct IntrMaskingInfo {
-    nested_level: usize,
-    sie_before_masking: bool,
-}
-
-lazy_static! {
-    static ref INTR_MASKING_INFO: UPSafeCellRaw<IntrMaskingInfo> =
-        unsafe { UPSafeCellRaw::new(IntrMaskingInfo::new()) };
-}
-
-impl IntrMaskingInfo {
-    pub fn new() -> Self {
-        Self {
-            nested_level: 0,
-            sie_before_masking: false,
-        }
-    }
-
-    pub fn enter(&mut self) {
-        let sie = sstatus::read().sie();
-        unsafe {
-            sstatus::clear_sie();
-        }
-        if self.nested_level == 0 {
-            self.sie_before_masking = sie;
-        }
-        self.nested_level += 1;
-    }
-
-    pub fn exit(&mut self) {
-        self.nested_level -= 1;
-        if self.nested_level == 0 && self.sie_before_masking {
-            unsafe {
-                sstatus::set_sie();
-            }
-        }
-    }
-}
-
-pub struct UPIntrFreeCell<T> {
-    /// inner data
-    inner: RefCell<T>,
-}
-
-unsafe impl<T> Sync for UPIntrFreeCell<T> {}
-
-pub struct UPIntrRefMut<'a, T>(Option<RefMut<'a, T>>);
-
-impl<T> UPIntrFreeCell<T> {
-    pub unsafe fn new(value: T) -> Self {
-        Self {
-            inner: RefCell::new(value),
-        }
-    }
-
-    /// Panic if the data has been borrowed.
-    pub fn exclusive_access(&self) -> UPIntrRefMut<'_, T> {
-        INTR_MASKING_INFO.get_mut().enter();
-        UPIntrRefMut(Some(self.inner.borrow_mut()))
-    }
-
-    pub fn exclusive_session<F, V>(&self, f: F) -> V
-    where
-        F: FnOnce(&mut T) -> V,
-    {
-        let mut inner = self.exclusive_access();
-        f(inner.deref_mut())
-    }
-}
-
-impl<'a, T> Drop for UPIntrRefMut<'a, T> {
-    fn drop(&mut self) {
-        self.0 = None;
-        INTR_MASKING_INFO.get_mut().exit();
-    }
-}
-
-impl<'a, T> Deref for UPIntrRefMut<'a, T> {
-    type Target = T;
-    fn deref(&self) -> &Self::Target {
-        self.0.as_ref().unwrap().deref()
-    }
-}
-impl<'a, T> DerefMut for UPIntrRefMut<'a, T> {
-    fn deref_mut(&mut self) -> &mut Self::Target {
-        self.0.as_mut().unwrap().deref_mut()
-    }
-}
diff --git a/os/src/syscall/fs.rs b/os/src/syscall/fs.rs
index 2758825..8d46fad 100644
--- a/os/src/syscall/fs.rs
+++ b/os/src/syscall/fs.rs
@@ -1,12 +1,12 @@
-use crate::fs::{make_pipe, open_file, OpenFlags};
-use crate::mm::{translated_byte_buffer, translated_refmut, translated_str, UserBuffer};
-use crate::task::{current_process, current_user_token};
-use alloc::sync::Arc;
+//! File and filesystem-related syscalls
+use crate::fs::{OpenFlags, open_file};
+use crate::mm::{UserBuffer, translated_byte_buffer, translated_str};
+use crate::task::{current_task, current_user_token};
 
 pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
     let token = current_user_token();
-    let process = current_process();
-    let inner = process.inner_exclusive_access();
+    let task = current_task().unwrap();
+    let inner = task.inner_exclusive_access();
     if fd >= inner.fd_table.len() {
         return -1;
     }
@@ -25,8 +25,8 @@ pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
 
 pub fn sys_read(fd: usize, buf: *const u8, len: usize) -> isize {
     let token = current_user_token();
-    let process = current_process();
-    let inner = process.inner_exclusive_access();
+    let task = current_task().unwrap();
+    let inner = task.inner_exclusive_access();
     if fd >= inner.fd_table.len() {
         return -1;
     }
@@ -44,11 +44,18 @@ pub fn sys_read(fd: usize, buf: *const u8, len: usize) -> isize {
 }
 
 pub fn sys_open(path: *const u8, flags: u32) -> isize {
-    let process = current_process();
+    let task = current_task().unwrap();
     let token = current_user_token();
     let path = translated_str(token, path);
+
+    // 简单用户检查示例：非 root 用户不能打开 /root 下文件
+    let username = task.inner_exclusive_access().user.clone();
+    if path.starts_with("/root") && username != "root" {
+        return -1; // Permission denied
+    }
+
     if let Some(inode) = open_file(path.as_str(), OpenFlags::from_bits(flags).unwrap()) {
-        let mut inner = process.inner_exclusive_access();
+        let mut inner = task.inner_exclusive_access();
         let fd = inner.alloc_fd();
         inner.fd_table[fd] = Some(inode);
         fd as isize
@@ -57,9 +64,10 @@ pub fn sys_open(path: *const u8, flags: u32) -> isize {
     }
 }
 
+
 pub fn sys_close(fd: usize) -> isize {
-    let process = current_process();
-    let mut inner = process.inner_exclusive_access();
+    let task = current_task().unwrap();
+    let mut inner = task.inner_exclusive_access();
     if fd >= inner.fd_table.len() {
         return -1;
     }
@@ -69,31 +77,3 @@ pub fn sys_close(fd: usize) -> isize {
     inner.fd_table[fd].take();
     0
 }
-
-pub fn sys_pipe(pipe: *mut usize) -> isize {
-    let process = current_process();
-    let token = current_user_token();
-    let mut inner = process.inner_exclusive_access();
-    let (pipe_read, pipe_write) = make_pipe();
-    let read_fd = inner.alloc_fd();
-    inner.fd_table[read_fd] = Some(pipe_read);
-    let write_fd = inner.alloc_fd();
-    inner.fd_table[write_fd] = Some(pipe_write);
-    *translated_refmut(token, pipe) = read_fd;
-    *translated_refmut(token, unsafe { pipe.add(1) }) = write_fd;
-    0
-}
-
-pub fn sys_dup(fd: usize) -> isize {
-    let process = current_process();
-    let mut inner = process.inner_exclusive_access();
-    if fd >= inner.fd_table.len() {
-        return -1;
-    }
-    if inner.fd_table[fd].is_none() {
-        return -1;
-    }
-    let new_fd = inner.alloc_fd();
-    inner.fd_table[new_fd] = Some(Arc::clone(inner.fd_table[fd].as_ref().unwrap()));
-    new_fd as isize
-}
diff --git a/os/src/syscall/gui.rs b/os/src/syscall/gui.rs
deleted file mode 100644
index c5ba8a4..0000000
--- a/os/src/syscall/gui.rs
+++ /dev/null
@@ -1,34 +0,0 @@
-use crate::drivers::GPU_DEVICE;
-use crate::mm::{MapArea, MapPermission, MapType, PhysAddr, VirtAddr};
-use crate::task::current_process;
-
-const FB_VADDR: usize = 0x10000000;
-
-pub fn sys_framebuffer() -> isize {
-    let fb = GPU_DEVICE.get_framebuffer();
-    let len = fb.len();
-    // println!("[kernel] FrameBuffer: addr 0x{:X}, len {}", fb.as_ptr() as usize , len);
-    let fb_start_pa = PhysAddr::from(fb.as_ptr() as usize);
-    assert!(fb_start_pa.aligned());
-    let fb_start_ppn = fb_start_pa.floor();
-    let fb_start_vpn = VirtAddr::from(FB_VADDR).floor();
-    let pn_offset = fb_start_ppn.0 as isize - fb_start_vpn.0 as isize;
-
-    let current_process = current_process();
-    let mut inner = current_process.inner_exclusive_access();
-    inner.memory_set.push(
-        MapArea::new(
-            (FB_VADDR as usize).into(),
-            (FB_VADDR + len as usize).into(),
-            MapType::Linear(pn_offset),
-            MapPermission::R | MapPermission::W | MapPermission::U,
-        ),
-        None,
-    );
-    FB_VADDR as isize
-}
-
-pub fn sys_framebuffer_flush() -> isize {
-    GPU_DEVICE.flush();
-    0
-}
diff --git a/os/src/syscall/input.rs b/os/src/syscall/input.rs
deleted file mode 100644
index ee86bd3..0000000
--- a/os/src/syscall/input.rs
+++ /dev/null
@@ -1,28 +0,0 @@
-//use crate::drivers::{KEYBOARD_DEVICE,MOUSE_DEVICE,INPUT_CONDVAR,read_input_event};
-use crate::drivers::{KEYBOARD_DEVICE, MOUSE_DEVICE};
-
-pub fn sys_event_get() -> isize {
-    let kb = KEYBOARD_DEVICE.clone();
-    let mouse = MOUSE_DEVICE.clone();
-    //let input=INPUT_CONDVAR.clone();
-    //read_input_event() as isize
-    if !kb.is_empty() {
-        kb.read_event() as isize
-    } else if !mouse.is_empty() {
-        mouse.read_event() as isize
-    } else {
-        0
-    }
-}
-
-use crate::drivers::chardev::UART;
-
-/// check UART's read-buffer is empty or not
-pub fn sys_key_pressed() -> isize {
-    let res = !UART.read_buffer_is_empty();
-    if res {
-        1
-    } else {
-        0
-    }
-}
diff --git a/os/src/syscall/mod.rs b/os/src/syscall/mod.rs
index cd12de0..8bcb326 100644
--- a/os/src/syscall/mod.rs
+++ b/os/src/syscall/mod.rs
@@ -1,90 +1,45 @@
-const SYSCALL_DUP: usize = 24;
-const SYSCALL_CONNECT: usize = 29;
-const SYSCALL_LISTEN: usize = 30;
-const SYSCALL_ACCEPT: usize = 31;
+//! Implementation of syscalls
+//!
+//! The single entry point to all system calls, [`syscall()`], is called
+//! whenever userspace wishes to perform a system call using the `ecall`
+//! instruction. In this case, the processor raises an 'Environment call from
+//! U-mode' exception, which is handled as one of the cases in
+//! [`crate::trap::trap_handler`].
+//!
+//! For clarity, each single syscall is implemented as its own function, named
+//! `sys_` then the name of the syscall. You can find functions like this in
+//! submodules, and you should also implement syscalls this way.
 const SYSCALL_OPEN: usize = 56;
 const SYSCALL_CLOSE: usize = 57;
-const SYSCALL_PIPE: usize = 59;
 const SYSCALL_READ: usize = 63;
 const SYSCALL_WRITE: usize = 64;
 const SYSCALL_EXIT: usize = 93;
-const SYSCALL_SLEEP: usize = 101;
 const SYSCALL_YIELD: usize = 124;
-const SYSCALL_KILL: usize = 129;
 const SYSCALL_GET_TIME: usize = 169;
 const SYSCALL_GETPID: usize = 172;
 const SYSCALL_FORK: usize = 220;
 const SYSCALL_EXEC: usize = 221;
 const SYSCALL_WAITPID: usize = 260;
-const SYSCALL_THREAD_CREATE: usize = 1000;
-const SYSCALL_GETTID: usize = 1001;
-const SYSCALL_WAITTID: usize = 1002;
-const SYSCALL_MUTEX_CREATE: usize = 1010;
-const SYSCALL_MUTEX_LOCK: usize = 1011;
-const SYSCALL_MUTEX_UNLOCK: usize = 1012;
-const SYSCALL_SEMAPHORE_CREATE: usize = 1020;
-const SYSCALL_SEMAPHORE_UP: usize = 1021;
-const SYSCALL_SEMAPHORE_DOWN: usize = 1022;
-const SYSCALL_CONDVAR_CREATE: usize = 1030;
-const SYSCALL_CONDVAR_SIGNAL: usize = 1031;
-const SYSCALL_CONDVAR_WAIT: usize = 1032;
-const SYSCALL_FRAMEBUFFER: usize = 2000;
-const SYSCALL_FRAMEBUFFER_FLUSH: usize = 2001;
-const SYSCALL_EVENT_GET: usize = 3000;
-const SYSCALL_KEY_PRESSED: usize = 3001;
 
 mod fs;
-mod gui;
-mod input;
-mod net;
 mod process;
-mod sync;
-mod thread;
 
 use fs::*;
-use gui::*;
-use input::*;
-use net::*;
 use process::*;
-use sync::*;
-use thread::*;
-
+/// handle syscall exception with `syscall_id` and other arguments
 pub fn syscall(syscall_id: usize, args: [usize; 3]) -> isize {
     match syscall_id {
-        SYSCALL_DUP => sys_dup(args[0]),
-        SYSCALL_CONNECT => sys_connect(args[0] as _, args[1] as _, args[2] as _),
-        SYSCALL_LISTEN => sys_listen(args[0] as _),
-        SYSCALL_ACCEPT => sys_accept(args[0] as _),
         SYSCALL_OPEN => sys_open(args[0] as *const u8, args[1] as u32),
         SYSCALL_CLOSE => sys_close(args[0]),
-        SYSCALL_PIPE => sys_pipe(args[0] as *mut usize),
         SYSCALL_READ => sys_read(args[0], args[1] as *const u8, args[2]),
         SYSCALL_WRITE => sys_write(args[0], args[1] as *const u8, args[2]),
         SYSCALL_EXIT => sys_exit(args[0] as i32),
-        SYSCALL_SLEEP => sys_sleep(args[0]),
         SYSCALL_YIELD => sys_yield(),
-        SYSCALL_KILL => sys_kill(args[0], args[1] as u32),
         SYSCALL_GET_TIME => sys_get_time(),
         SYSCALL_GETPID => sys_getpid(),
         SYSCALL_FORK => sys_fork(),
-        SYSCALL_EXEC => sys_exec(args[0] as *const u8, args[1] as *const usize),
+        SYSCALL_EXEC => sys_exec(args[0] as *const u8),
         SYSCALL_WAITPID => sys_waitpid(args[0] as isize, args[1] as *mut i32),
-        SYSCALL_THREAD_CREATE => sys_thread_create(args[0], args[1]),
-        SYSCALL_GETTID => sys_gettid(),
-        SYSCALL_WAITTID => sys_waittid(args[0]) as isize,
-        SYSCALL_MUTEX_CREATE => sys_mutex_create(args[0] == 1),
-        SYSCALL_MUTEX_LOCK => sys_mutex_lock(args[0]),
-        SYSCALL_MUTEX_UNLOCK => sys_mutex_unlock(args[0]),
-        SYSCALL_SEMAPHORE_CREATE => sys_semaphore_create(args[0]),
-        SYSCALL_SEMAPHORE_UP => sys_semaphore_up(args[0]),
-        SYSCALL_SEMAPHORE_DOWN => sys_semaphore_down(args[0]),
-        SYSCALL_CONDVAR_CREATE => sys_condvar_create(),
-        SYSCALL_CONDVAR_SIGNAL => sys_condvar_signal(args[0]),
-        SYSCALL_CONDVAR_WAIT => sys_condvar_wait(args[0], args[1]),
-        SYSCALL_FRAMEBUFFER => sys_framebuffer(),
-        SYSCALL_FRAMEBUFFER_FLUSH => sys_framebuffer_flush(),
-        SYSCALL_EVENT_GET => sys_event_get(),
-        SYSCALL_KEY_PRESSED => sys_key_pressed(),
         _ => panic!("Unsupported syscall_id: {}", syscall_id),
     }
 }
diff --git a/os/src/syscall/net.rs b/os/src/syscall/net.rs
deleted file mode 100644
index c16b9ce..0000000
--- a/os/src/syscall/net.rs
+++ /dev/null
@@ -1,53 +0,0 @@
-use crate::net::port_table::{accept, listen, port_acceptable, PortFd};
-use crate::net::udp::UDP;
-use crate::net::{net_interrupt_handler, IPv4};
-use crate::task::{current_process, current_task, current_trap_cx};
-use alloc::sync::Arc;
-
-// just support udp
-pub fn sys_connect(raddr: u32, lport: u16, rport: u16) -> isize {
-    let process = current_process();
-    let mut inner = process.inner_exclusive_access();
-    let fd = inner.alloc_fd();
-    let udp_node = UDP::new(IPv4::from_u32(raddr), lport, rport);
-    inner.fd_table[fd] = Some(Arc::new(udp_node));
-    fd as isize
-}
-
-// listen a port
-pub fn sys_listen(port: u16) -> isize {
-    match listen(port) {
-        Some(port_index) => {
-            let process = current_process();
-            let mut inner = process.inner_exclusive_access();
-            let fd = inner.alloc_fd();
-            let port_fd = PortFd::new(port_index);
-            inner.fd_table[fd] = Some(Arc::new(port_fd));
-
-            // NOTICE: this return the port index, not the fd
-            port_index as isize
-        }
-        None => -1,
-    }
-}
-
-// accept a tcp connection
-pub fn sys_accept(port_index: usize) -> isize {
-    println!("accepting port {}", port_index);
-
-    let task = current_task().unwrap();
-    accept(port_index, task);
-    // block_current_and_run_next();
-
-    // NOTICE: There does not have interrupt handler, just call it munually.
-    loop {
-        net_interrupt_handler();
-
-        if !port_acceptable(port_index) {
-            break;
-        }
-    }
-
-    let cx = current_trap_cx();
-    cx.x[10] as isize
-}
diff --git a/os/src/syscall/process.rs b/os/src/syscall/process.rs
index 7d5b67a..61e78d6 100644
--- a/os/src/syscall/process.rs
+++ b/os/src/syscall/process.rs
@@ -1,13 +1,11 @@
-use crate::fs::{open_file, OpenFlags};
-use crate::mm::{translated_ref, translated_refmut, translated_str};
+use crate::fs::{OpenFlags, open_file};
+use crate::mm::{translated_refmut, translated_str};
 use crate::task::{
-    current_process, current_task, current_user_token, exit_current_and_run_next, pid2process,
-    suspend_current_and_run_next, SignalFlags,
+    add_task, current_task, current_user_token, exit_current_and_run_next,
+    suspend_current_and_run_next,
 };
 use crate::timer::get_time_ms;
-use alloc::string::String;
 use alloc::sync::Arc;
-use alloc::vec::Vec;
 
 pub fn sys_exit(exit_code: i32) -> ! {
     exit_current_and_run_next(exit_code);
@@ -24,44 +22,31 @@ pub fn sys_get_time() -> isize {
 }
 
 pub fn sys_getpid() -> isize {
-    current_task().unwrap().process.upgrade().unwrap().getpid() as isize
+    current_task().unwrap().pid.0 as isize
 }
 
 pub fn sys_fork() -> isize {
-    let current_process = current_process();
-    let new_process = current_process.fork();
-    let new_pid = new_process.getpid();
+    let current_task = current_task().unwrap();
+    let new_task = current_task.fork();
+    let new_pid = new_task.pid.0;
     // modify trap context of new_task, because it returns immediately after switching
-    let new_process_inner = new_process.inner_exclusive_access();
-    let task = new_process_inner.tasks[0].as_ref().unwrap();
-    let trap_cx = task.inner_exclusive_access().get_trap_cx();
+    let trap_cx = new_task.inner_exclusive_access().get_trap_cx();
     // we do not have to move to next instruction since we have done it before
     // for child process, fork returns 0
     trap_cx.x[10] = 0;
+    // add new task to scheduler
+    add_task(new_task);
     new_pid as isize
 }
 
-pub fn sys_exec(path: *const u8, mut args: *const usize) -> isize {
+pub fn sys_exec(path: *const u8) -> isize {
     let token = current_user_token();
     let path = translated_str(token, path);
-    let mut args_vec: Vec<String> = Vec::new();
-    loop {
-        let arg_str_ptr = *translated_ref(token, args);
-        if arg_str_ptr == 0 {
-            break;
-        }
-        args_vec.push(translated_str(token, arg_str_ptr as *const u8));
-        unsafe {
-            args = args.add(1);
-        }
-    }
     if let Some(app_inode) = open_file(path.as_str(), OpenFlags::RDONLY) {
         let all_data = app_inode.read_all();
-        let process = current_process();
-        let argc = args_vec.len();
-        process.exec(all_data.as_slice(), args_vec);
-        // return argc because cx.x[10] will be covered with it later
-        argc as isize
+        let task = current_task().unwrap();
+        task.exec(all_data.as_slice());
+        0
     } else {
         -1
     }
@@ -70,10 +55,11 @@ pub fn sys_exec(path: *const u8, mut args: *const usize) -> isize {
 /// If there is not a child process whose pid is same as given, return -1.
 /// Else if there is a child process but it is still running, return -2.
 pub fn sys_waitpid(pid: isize, exit_code_ptr: *mut i32) -> isize {
-    let process = current_process();
+    let task = current_task().unwrap();
     // find a child process
 
-    let mut inner = process.inner_exclusive_access();
+    // ---- access current PCB exclusively
+    let mut inner = task.inner_exclusive_access();
     if !inner
         .children
         .iter()
@@ -84,7 +70,7 @@ pub fn sys_waitpid(pid: isize, exit_code_ptr: *mut i32) -> isize {
     }
     let pair = inner.children.iter().enumerate().find(|(_, p)| {
         // ++++ temporarily access child PCB exclusively
-        p.inner_exclusive_access().is_zombie && (pid == -1 || pid as usize == p.getpid())
+        p.inner_exclusive_access().is_zombie() && (pid == -1 || pid as usize == p.getpid())
         // ++++ release child PCB
     });
     if let Some((idx, _)) = pair {
@@ -102,16 +88,3 @@ pub fn sys_waitpid(pid: isize, exit_code_ptr: *mut i32) -> isize {
     }
     // ---- release current PCB automatically
 }
-
-pub fn sys_kill(pid: usize, signal: u32) -> isize {
-    if let Some(process) = pid2process(pid) {
-        if let Some(flag) = SignalFlags::from_bits(signal) {
-            process.inner_exclusive_access().signals |= flag;
-            0
-        } else {
-            -1
-        }
-    } else {
-        -1
-    }
-}
diff --git a/os/src/syscall/sync.rs b/os/src/syscall/sync.rs
deleted file mode 100644
index 1180669..0000000
--- a/os/src/syscall/sync.rs
+++ /dev/null
@@ -1,134 +0,0 @@
-use crate::sync::{Condvar, Mutex, MutexBlocking, MutexSpin, Semaphore};
-use crate::task::{block_current_and_run_next, current_process, current_task};
-use crate::timer::{add_timer, get_time_ms};
-use alloc::sync::Arc;
-
-pub fn sys_sleep(ms: usize) -> isize {
-    let expire_ms = get_time_ms() + ms;
-    let task = current_task().unwrap();
-    add_timer(expire_ms, task);
-    block_current_and_run_next();
-    0
-}
-
-pub fn sys_mutex_create(blocking: bool) -> isize {
-    let process = current_process();
-    let mutex: Option<Arc<dyn Mutex>> = if !blocking {
-        Some(Arc::new(MutexSpin::new()))
-    } else {
-        Some(Arc::new(MutexBlocking::new()))
-    };
-    let mut process_inner = process.inner_exclusive_access();
-    if let Some(id) = process_inner
-        .mutex_list
-        .iter()
-        .enumerate()
-        .find(|(_, item)| item.is_none())
-        .map(|(id, _)| id)
-    {
-        process_inner.mutex_list[id] = mutex;
-        id as isize
-    } else {
-        process_inner.mutex_list.push(mutex);
-        process_inner.mutex_list.len() as isize - 1
-    }
-}
-
-pub fn sys_mutex_lock(mutex_id: usize) -> isize {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    let mutex = Arc::clone(process_inner.mutex_list[mutex_id].as_ref().unwrap());
-    drop(process_inner);
-    drop(process);
-    mutex.lock();
-    0
-}
-
-pub fn sys_mutex_unlock(mutex_id: usize) -> isize {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    let mutex = Arc::clone(process_inner.mutex_list[mutex_id].as_ref().unwrap());
-    drop(process_inner);
-    drop(process);
-    mutex.unlock();
-    0
-}
-
-pub fn sys_semaphore_create(res_count: usize) -> isize {
-    let process = current_process();
-    let mut process_inner = process.inner_exclusive_access();
-    let id = if let Some(id) = process_inner
-        .semaphore_list
-        .iter()
-        .enumerate()
-        .find(|(_, item)| item.is_none())
-        .map(|(id, _)| id)
-    {
-        process_inner.semaphore_list[id] = Some(Arc::new(Semaphore::new(res_count)));
-        id
-    } else {
-        process_inner
-            .semaphore_list
-            .push(Some(Arc::new(Semaphore::new(res_count))));
-        process_inner.semaphore_list.len() - 1
-    };
-    id as isize
-}
-
-pub fn sys_semaphore_up(sem_id: usize) -> isize {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    let sem = Arc::clone(process_inner.semaphore_list[sem_id].as_ref().unwrap());
-    drop(process_inner);
-    sem.up();
-    0
-}
-
-pub fn sys_semaphore_down(sem_id: usize) -> isize {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    let sem = Arc::clone(process_inner.semaphore_list[sem_id].as_ref().unwrap());
-    drop(process_inner);
-    sem.down();
-    0
-}
-
-pub fn sys_condvar_create() -> isize {
-    let process = current_process();
-    let mut process_inner = process.inner_exclusive_access();
-    let id = if let Some(id) = process_inner
-        .condvar_list
-        .iter()
-        .enumerate()
-        .find(|(_, item)| item.is_none())
-        .map(|(id, _)| id)
-    {
-        process_inner.condvar_list[id] = Some(Arc::new(Condvar::new()));
-        id
-    } else {
-        process_inner
-            .condvar_list
-            .push(Some(Arc::new(Condvar::new())));
-        process_inner.condvar_list.len() - 1
-    };
-    id as isize
-}
-
-pub fn sys_condvar_signal(condvar_id: usize) -> isize {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    let condvar = Arc::clone(process_inner.condvar_list[condvar_id].as_ref().unwrap());
-    drop(process_inner);
-    condvar.signal();
-    0
-}
-
-pub fn sys_condvar_wait(condvar_id: usize, mutex_id: usize) -> isize {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    let condvar = Arc::clone(process_inner.condvar_list[condvar_id].as_ref().unwrap());
-    let mutex = Arc::clone(process_inner.mutex_list[mutex_id].as_ref().unwrap());
-    drop(process_inner);
-    condvar.wait_with_mutex(mutex);
-    0
-}
diff --git a/os/src/syscall/thread.rs b/os/src/syscall/thread.rs
deleted file mode 100644
index 3955d9d..0000000
--- a/os/src/syscall/thread.rs
+++ /dev/null
@@ -1,85 +0,0 @@
-use crate::{
-    mm::kernel_token,
-    task::{add_task, current_task, TaskControlBlock},
-    trap::{trap_handler, TrapContext},
-};
-use alloc::sync::Arc;
-
-pub fn sys_thread_create(entry: usize, arg: usize) -> isize {
-    let task = current_task().unwrap();
-    let process = task.process.upgrade().unwrap();
-    // create a new thread
-    let new_task = Arc::new(TaskControlBlock::new(
-        Arc::clone(&process),
-        task.inner_exclusive_access()
-            .res
-            .as_ref()
-            .unwrap()
-            .ustack_base,
-        true,
-    ));
-    // add new task to scheduler
-    add_task(Arc::clone(&new_task));
-    let new_task_inner = new_task.inner_exclusive_access();
-    let new_task_res = new_task_inner.res.as_ref().unwrap();
-    let new_task_tid = new_task_res.tid;
-    let mut process_inner = process.inner_exclusive_access();
-    // add new thread to current process
-    let tasks = &mut process_inner.tasks;
-    while tasks.len() < new_task_tid + 1 {
-        tasks.push(None);
-    }
-    tasks[new_task_tid] = Some(Arc::clone(&new_task));
-    let new_task_trap_cx = new_task_inner.get_trap_cx();
-    *new_task_trap_cx = TrapContext::app_init_context(
-        entry,
-        new_task_res.ustack_top(),
-        kernel_token(),
-        new_task.kstack.get_top(),
-        trap_handler as usize,
-    );
-    (*new_task_trap_cx).x[10] = arg;
-    new_task_tid as isize
-}
-
-pub fn sys_gettid() -> isize {
-    current_task()
-        .unwrap()
-        .inner_exclusive_access()
-        .res
-        .as_ref()
-        .unwrap()
-        .tid as isize
-}
-
-/// thread does not exist, return -1
-/// thread has not exited yet, return -2
-/// otherwise, return thread's exit code
-pub fn sys_waittid(tid: usize) -> i32 {
-    let task = current_task().unwrap();
-    let process = task.process.upgrade().unwrap();
-    let task_inner = task.inner_exclusive_access();
-    let mut process_inner = process.inner_exclusive_access();
-    // a thread cannot wait for itself
-    if task_inner.res.as_ref().unwrap().tid == tid {
-        return -1;
-    }
-    let mut exit_code: Option<i32> = None;
-    let waited_task = process_inner.tasks[tid].as_ref();
-    if let Some(waited_task) = waited_task {
-        if let Some(waited_exit_code) = waited_task.inner_exclusive_access().exit_code {
-            exit_code = Some(waited_exit_code);
-        }
-    } else {
-        // waited thread does not exist
-        return -1;
-    }
-    if let Some(exit_code) = exit_code {
-        // dealloc the exited thread
-        process_inner.tasks[tid] = None;
-        exit_code
-    } else {
-        // waited thread has not exited
-        -2
-    }
-}
diff --git a/os/src/task/context.rs b/os/src/task/context.rs
index e4f59d8..520bce1 100644
--- a/os/src/task/context.rs
+++ b/os/src/task/context.rs
@@ -1,13 +1,19 @@
+//! Implementation of [`TaskContext`]
 use crate::trap::trap_return;
 
 #[repr(C)]
+/// task context structure containing some registers
 pub struct TaskContext {
+    /// return address ( e.g. __restore ) of __switch ASM function
     ra: usize,
+    /// kernel stack pointer of app
     sp: usize,
+    /// s0-11 register, callee saved
     s: [usize; 12],
 }
 
 impl TaskContext {
+    /// init task context
     pub fn zero_init() -> Self {
         Self {
             ra: 0,
@@ -15,6 +21,7 @@ impl TaskContext {
             s: [0; 12],
         }
     }
+    /// set Task Context{__restore ASM funciton: trap_return, sp: kstack_ptr, s: s_0..12}
     pub fn goto_trap_return(kstack_ptr: usize) -> Self {
         Self {
             ra: trap_return as usize,
diff --git a/os/src/task/id.rs b/os/src/task/id.rs
deleted file mode 100644
index 23ddf7b..0000000
--- a/os/src/task/id.rs
+++ /dev/null
@@ -1,226 +0,0 @@
-use super::ProcessControlBlock;
-use crate::config::{KERNEL_STACK_SIZE, PAGE_SIZE, TRAMPOLINE, TRAP_CONTEXT_BASE, USER_STACK_SIZE};
-use crate::mm::{MapPermission, PhysPageNum, VirtAddr, KERNEL_SPACE};
-use crate::sync::UPIntrFreeCell;
-use alloc::{
-    sync::{Arc, Weak},
-    vec::Vec,
-};
-use lazy_static::*;
-
-pub struct RecycleAllocator {
-    current: usize,
-    recycled: Vec<usize>,
-}
-
-impl RecycleAllocator {
-    pub fn new() -> Self {
-        RecycleAllocator {
-            current: 0,
-            recycled: Vec::new(),
-        }
-    }
-    pub fn alloc(&mut self) -> usize {
-        if let Some(id) = self.recycled.pop() {
-            id
-        } else {
-            self.current += 1;
-            self.current - 1
-        }
-    }
-    pub fn dealloc(&mut self, id: usize) {
-        assert!(id < self.current);
-        assert!(
-            !self.recycled.iter().any(|i| *i == id),
-            "id {} has been deallocated!",
-            id
-        );
-        self.recycled.push(id);
-    }
-}
-
-lazy_static! {
-    static ref PID_ALLOCATOR: UPIntrFreeCell<RecycleAllocator> =
-        unsafe { UPIntrFreeCell::new(RecycleAllocator::new()) };
-    static ref KSTACK_ALLOCATOR: UPIntrFreeCell<RecycleAllocator> =
-        unsafe { UPIntrFreeCell::new(RecycleAllocator::new()) };
-}
-
-pub const IDLE_PID: usize = 0;
-
-pub struct PidHandle(pub usize);
-
-pub fn pid_alloc() -> PidHandle {
-    PidHandle(PID_ALLOCATOR.exclusive_access().alloc())
-}
-
-impl Drop for PidHandle {
-    fn drop(&mut self) {
-        PID_ALLOCATOR.exclusive_access().dealloc(self.0);
-    }
-}
-
-/// Return (bottom, top) of a kernel stack in kernel space.
-pub fn kernel_stack_position(kstack_id: usize) -> (usize, usize) {
-    let top = TRAMPOLINE - kstack_id * (KERNEL_STACK_SIZE + PAGE_SIZE);
-    let bottom = top - KERNEL_STACK_SIZE;
-    (bottom, top)
-}
-
-pub struct KernelStack(pub usize);
-
-pub fn kstack_alloc() -> KernelStack {
-    let kstack_id = KSTACK_ALLOCATOR.exclusive_access().alloc();
-    let (kstack_bottom, kstack_top) = kernel_stack_position(kstack_id);
-    KERNEL_SPACE.exclusive_access().insert_framed_area(
-        kstack_bottom.into(),
-        kstack_top.into(),
-        MapPermission::R | MapPermission::W,
-    );
-    KernelStack(kstack_id)
-}
-
-impl Drop for KernelStack {
-    fn drop(&mut self) {
-        let (kernel_stack_bottom, _) = kernel_stack_position(self.0);
-        let kernel_stack_bottom_va: VirtAddr = kernel_stack_bottom.into();
-        KERNEL_SPACE
-            .exclusive_access()
-            .remove_area_with_start_vpn(kernel_stack_bottom_va.into());
-        KSTACK_ALLOCATOR.exclusive_access().dealloc(self.0);
-    }
-}
-
-impl KernelStack {
-    #[allow(unused)]
-    pub fn push_on_top<T>(&self, value: T) -> *mut T
-    where
-        T: Sized,
-    {
-        let kernel_stack_top = self.get_top();
-        let ptr_mut = (kernel_stack_top - core::mem::size_of::<T>()) as *mut T;
-        unsafe {
-            *ptr_mut = value;
-        }
-        ptr_mut
-    }
-    pub fn get_top(&self) -> usize {
-        let (_, kernel_stack_top) = kernel_stack_position(self.0);
-        kernel_stack_top
-    }
-}
-
-pub struct TaskUserRes {
-    pub tid: usize,
-    pub ustack_base: usize,
-    pub process: Weak<ProcessControlBlock>,
-}
-
-fn trap_cx_bottom_from_tid(tid: usize) -> usize {
-    TRAP_CONTEXT_BASE - tid * PAGE_SIZE
-}
-
-fn ustack_bottom_from_tid(ustack_base: usize, tid: usize) -> usize {
-    ustack_base + tid * (PAGE_SIZE + USER_STACK_SIZE)
-}
-
-impl TaskUserRes {
-    pub fn new(
-        process: Arc<ProcessControlBlock>,
-        ustack_base: usize,
-        alloc_user_res: bool,
-    ) -> Self {
-        let tid = process.inner_exclusive_access().alloc_tid();
-        let task_user_res = Self {
-            tid,
-            ustack_base,
-            process: Arc::downgrade(&process),
-        };
-        if alloc_user_res {
-            task_user_res.alloc_user_res();
-        }
-        task_user_res
-    }
-
-    pub fn alloc_user_res(&self) {
-        let process = self.process.upgrade().unwrap();
-        let mut process_inner = process.inner_exclusive_access();
-        // alloc user stack
-        let ustack_bottom = ustack_bottom_from_tid(self.ustack_base, self.tid);
-        let ustack_top = ustack_bottom + USER_STACK_SIZE;
-        process_inner.memory_set.insert_framed_area(
-            ustack_bottom.into(),
-            ustack_top.into(),
-            MapPermission::R | MapPermission::W | MapPermission::U,
-        );
-        // alloc trap_cx
-        let trap_cx_bottom = trap_cx_bottom_from_tid(self.tid);
-        let trap_cx_top = trap_cx_bottom + PAGE_SIZE;
-        process_inner.memory_set.insert_framed_area(
-            trap_cx_bottom.into(),
-            trap_cx_top.into(),
-            MapPermission::R | MapPermission::W,
-        );
-    }
-
-    fn dealloc_user_res(&self) {
-        // dealloc tid
-        let process = self.process.upgrade().unwrap();
-        let mut process_inner = process.inner_exclusive_access();
-        // dealloc ustack manually
-        let ustack_bottom_va: VirtAddr = ustack_bottom_from_tid(self.ustack_base, self.tid).into();
-        process_inner
-            .memory_set
-            .remove_area_with_start_vpn(ustack_bottom_va.into());
-        // dealloc trap_cx manually
-        let trap_cx_bottom_va: VirtAddr = trap_cx_bottom_from_tid(self.tid).into();
-        process_inner
-            .memory_set
-            .remove_area_with_start_vpn(trap_cx_bottom_va.into());
-    }
-
-    #[allow(unused)]
-    pub fn alloc_tid(&mut self) {
-        self.tid = self
-            .process
-            .upgrade()
-            .unwrap()
-            .inner_exclusive_access()
-            .alloc_tid();
-    }
-
-    pub fn dealloc_tid(&self) {
-        let process = self.process.upgrade().unwrap();
-        let mut process_inner = process.inner_exclusive_access();
-        process_inner.dealloc_tid(self.tid);
-    }
-
-    pub fn trap_cx_user_va(&self) -> usize {
-        trap_cx_bottom_from_tid(self.tid)
-    }
-
-    pub fn trap_cx_ppn(&self) -> PhysPageNum {
-        let process = self.process.upgrade().unwrap();
-        let process_inner = process.inner_exclusive_access();
-        let trap_cx_bottom_va: VirtAddr = trap_cx_bottom_from_tid(self.tid).into();
-        process_inner
-            .memory_set
-            .translate(trap_cx_bottom_va.into())
-            .unwrap()
-            .ppn()
-    }
-
-    pub fn ustack_base(&self) -> usize {
-        self.ustack_base
-    }
-    pub fn ustack_top(&self) -> usize {
-        ustack_bottom_from_tid(self.ustack_base, self.tid) + USER_STACK_SIZE
-    }
-}
-
-impl Drop for TaskUserRes {
-    fn drop(&mut self) {
-        self.dealloc_tid();
-        self.dealloc_user_res();
-    }
-}
diff --git a/os/src/task/manager.rs b/os/src/task/manager.rs
index 7672cf5..315cd22 100644
--- a/os/src/task/manager.rs
+++ b/os/src/task/manager.rs
@@ -1,62 +1,41 @@
-use super::{ProcessControlBlock, TaskControlBlock, TaskStatus};
-use crate::sync::UPIntrFreeCell;
-use alloc::collections::{BTreeMap, VecDeque};
+//!Implementation of [`TaskManager`]
+use super::TaskControlBlock;
+use crate::sync::UPSafeCell;
+use alloc::collections::VecDeque;
 use alloc::sync::Arc;
 use lazy_static::*;
-
+///A array of `TaskControlBlock` that is thread-safe
 pub struct TaskManager {
     ready_queue: VecDeque<Arc<TaskControlBlock>>,
 }
 
 /// A simple FIFO scheduler.
 impl TaskManager {
+    ///Creat an empty TaskManager
     pub fn new() -> Self {
         Self {
             ready_queue: VecDeque::new(),
         }
     }
+    ///Add a task to `TaskManager`
     pub fn add(&mut self, task: Arc<TaskControlBlock>) {
         self.ready_queue.push_back(task);
     }
+    ///Remove the first task and return it,or `None` if `TaskManager` is empty
     pub fn fetch(&mut self) -> Option<Arc<TaskControlBlock>> {
         self.ready_queue.pop_front()
     }
 }
 
 lazy_static! {
-    pub static ref TASK_MANAGER: UPIntrFreeCell<TaskManager> =
-        unsafe { UPIntrFreeCell::new(TaskManager::new()) };
-    pub static ref PID2PCB: UPIntrFreeCell<BTreeMap<usize, Arc<ProcessControlBlock>>> =
-        unsafe { UPIntrFreeCell::new(BTreeMap::new()) };
+    pub static ref TASK_MANAGER: UPSafeCell<TaskManager> =
+        unsafe { UPSafeCell::new(TaskManager::new()) };
 }
-
+///Interface offered to add task
 pub fn add_task(task: Arc<TaskControlBlock>) {
     TASK_MANAGER.exclusive_access().add(task);
 }
-
-pub fn wakeup_task(task: Arc<TaskControlBlock>) {
-    let mut task_inner = task.inner_exclusive_access();
-    task_inner.task_status = TaskStatus::Ready;
-    drop(task_inner);
-    add_task(task);
-}
-
+///Interface offered to pop the first task
 pub fn fetch_task() -> Option<Arc<TaskControlBlock>> {
     TASK_MANAGER.exclusive_access().fetch()
 }
-
-pub fn pid2process(pid: usize) -> Option<Arc<ProcessControlBlock>> {
-    let map = PID2PCB.exclusive_access();
-    map.get(&pid).map(Arc::clone)
-}
-
-pub fn insert_into_pid2process(pid: usize, process: Arc<ProcessControlBlock>) {
-    PID2PCB.exclusive_access().insert(pid, process);
-}
-
-pub fn remove_from_pid2process(pid: usize) {
-    let mut map = PID2PCB.exclusive_access();
-    if map.remove(&pid).is_none() {
-        panic!("cannot find pid {} in pid2task!", pid);
-    }
-}
diff --git a/os/src/task/mod.rs b/os/src/task/mod.rs
index fe1343b..47c13cd 100644
--- a/os/src/task/mod.rs
+++ b/os/src/task/mod.rs
@@ -1,32 +1,44 @@
+//! Task management implementation
+//!
+//! Everything about task management, like starting and switching tasks is
+//! implemented here.
+//!
+//! A single global instance of [`TaskManager`] called `TASK_MANAGER` controls
+//! all the tasks in the whole operating system.
+//!
+//! A single global instance of [`Processor`] called `PROCESSOR` monitors running
+//! task(s) for each core.
+//!
+//! A single global instance of [`PidAllocator`] called `PID_ALLOCATOR` allocates
+//! pid for user apps.
+//!
+//! Be careful when you see `__switch` ASM function in `switch.S`. Control flow around this function
+//! might not be what you expect.
 mod context;
-mod id;
 mod manager;
-mod process;
+mod pid;
 mod processor;
-mod signal;
 mod switch;
 #[allow(clippy::module_inception)]
+#[allow(rustdoc::private_intra_doc_links)]
 mod task;
 
-use self::id::TaskUserRes;
-use crate::fs::{open_file, OpenFlags};
+use crate::fs::{OpenFlags, open_file};
 use crate::sbi::shutdown;
-use alloc::{sync::Arc, vec::Vec};
-use lazy_static::*;
-use manager::fetch_task;
-use process::ProcessControlBlock;
-use switch::__switch;
-
+use alloc::sync::Arc;
 pub use context::TaskContext;
-pub use id::{kstack_alloc, pid_alloc, KernelStack, PidHandle, IDLE_PID};
-pub use manager::{add_task, pid2process, remove_from_pid2process, wakeup_task};
-pub use processor::{
-    current_kstack_top, current_process, current_task, current_trap_cx, current_trap_cx_user_va,
-    current_user_token, run_tasks, schedule, take_current_task,
-};
-pub use signal::SignalFlags;
-pub use task::{TaskControlBlock, TaskStatus};
+use lazy_static::*;
+pub use manager::{TaskManager, fetch_task};
+use switch::__switch;
+use task::{TaskControlBlock, TaskStatus};
 
+pub use manager::add_task;
+pub use pid::{KernelStack, PidAllocator, PidHandle, pid_alloc};
+pub use processor::{
+    Processor, current_task, current_trap_cx, current_user_token, run_tasks, schedule,
+    take_current_task,
+};
+/// Suspend the current 'Running' task and run the next task in task list.
 pub fn suspend_current_and_run_next() {
     // There must be an application running.
     let task = take_current_task().unwrap();
@@ -37,7 +49,7 @@ pub fn suspend_current_and_run_next() {
     // Change status to Ready
     task_inner.task_status = TaskStatus::Ready;
     drop(task_inner);
-    // ---- release current TCB
+    // ---- release current PCB
 
     // push back to ready queue.
     add_task(task);
@@ -45,122 +57,68 @@ pub fn suspend_current_and_run_next() {
     schedule(task_cx_ptr);
 }
 
-/// This function must be followed by a schedule
-pub fn block_current_task() -> *mut TaskContext {
-    let task = take_current_task().unwrap();
-    let mut task_inner = task.inner_exclusive_access();
-    task_inner.task_status = TaskStatus::Blocked;
-    &mut task_inner.task_cx as *mut TaskContext
-}
-
-pub fn block_current_and_run_next() {
-    let task_cx_ptr = block_current_task();
-    schedule(task_cx_ptr);
-}
+/// pid of usertests app in make run TEST=1
+pub const IDLE_PID: usize = 0;
 
 /// Exit the current 'Running' task and run the next task in task list.
 pub fn exit_current_and_run_next(exit_code: i32) {
+    // take from Processor
     let task = take_current_task().unwrap();
-    let mut task_inner = task.inner_exclusive_access();
-    let process = task.process.upgrade().unwrap();
-    let tid = task_inner.res.as_ref().unwrap().tid;
-    // record exit code
-    task_inner.exit_code = Some(exit_code);
-    task_inner.res = None;
-    // here we do not remove the thread since we are still using the kstack
-    // it will be deallocated when sys_waittid is called
-    drop(task_inner);
-    drop(task);
-    // however, if this is the main thread of current process
-    // the process should terminate at once
-    if tid == 0 {
-        let pid = process.getpid();
-        if pid == IDLE_PID {
-            println!(
-                "[kernel] Idle process exit with exit_code {} ...",
-                exit_code
-            );
-            if exit_code != 0 {
-                //crate::sbi::shutdown(255); //255 == -1 for err hint
-                shutdown(true);
-            } else {
-                //crate::sbi::shutdown(0); //0 for success hint
-                shutdown(false);
-            }
-        }
-        remove_from_pid2process(pid);
-        let mut process_inner = process.inner_exclusive_access();
-        // mark this process as a zombie process
-        process_inner.is_zombie = true;
-        // record exit code of main process
-        process_inner.exit_code = exit_code;
 
-        {
-            // move all child processes under init process
-            let mut initproc_inner = INITPROC.inner_exclusive_access();
-            for child in process_inner.children.iter() {
-                child.inner_exclusive_access().parent = Some(Arc::downgrade(&INITPROC));
-                initproc_inner.children.push(child.clone());
-            }
-        }
-
-        // deallocate user res (including tid/trap_cx/ustack) of all threads
-        // it has to be done before we dealloc the whole memory_set
-        // otherwise they will be deallocated twice
-        let mut recycle_res = Vec::<TaskUserRes>::new();
-        for task in process_inner.tasks.iter().filter(|t| t.is_some()) {
-            let task = task.as_ref().unwrap();
-            let mut task_inner = task.inner_exclusive_access();
-            if let Some(res) = task_inner.res.take() {
-                recycle_res.push(res);
-            }
-        }
-        // dealloc_tid and dealloc_user_res require access to PCB inner, so we
-        // need to collect those user res first, then release process_inner
-        // for now to avoid deadlock/double borrow problem.
-        drop(process_inner);
-        recycle_res.clear();
-
-        let mut process_inner = process.inner_exclusive_access();
-        process_inner.children.clear();
-        // deallocate other data in user space i.e. program code/data section
-        process_inner.memory_set.recycle_data_pages();
-        // drop file descriptors
-        process_inner.fd_table.clear();
-        // Remove all tasks except for the main thread itself.
-        // This is because we are still using the kstack under the TCB
-        // of the main thread. This TCB, including its kstack, will be
-        // deallocated when the process is reaped via waitpid.
-        while process_inner.tasks.len() > 1 {
-            process_inner.tasks.pop();
+    let pid = task.getpid();
+    if pid == IDLE_PID {
+        println!(
+            "[kernel] Idle process exit with exit_code {} ...",
+            exit_code
+        );
+        if exit_code != 0 {
+            //crate::sbi::shutdown(255); //255 == -1 for err hint
+            shutdown(true)
+        } else {
+            //crate::sbi::shutdown(0); //0 for success hint
+            shutdown(false)
         }
     }
-    drop(process);
+
+    // **** access current TCB exclusively
+    let mut inner = task.inner_exclusive_access();
+    // Change status to Zombie
+    inner.task_status = TaskStatus::Zombie;
+    // Record exit code
+    inner.exit_code = exit_code;
+    // do not move to its parent but under initproc
+
+    // ++++++ access initproc TCB exclusively
+    {
+        let mut initproc_inner = INITPROC.inner_exclusive_access();
+        for child in inner.children.iter() {
+            child.inner_exclusive_access().parent = Some(Arc::downgrade(&INITPROC));
+            initproc_inner.children.push(child.clone());
+        }
+    }
+    // ++++++ release parent PCB
+
+    inner.children.clear();
+    // deallocate user space
+    inner.memory_set.recycle_data_pages();
+    drop(inner);
+    // **** release current PCB
+    // drop task manually to maintain rc correctly
+    drop(task);
     // we do not have to save task context
     let mut _unused = TaskContext::zero_init();
     schedule(&mut _unused as *mut _);
 }
 
 lazy_static! {
-    pub static ref INITPROC: Arc<ProcessControlBlock> = {
+    ///Globle process that init user shell
+    pub static ref INITPROC: Arc<TaskControlBlock> = Arc::new({
         let inode = open_file("initproc", OpenFlags::RDONLY).unwrap();
         let v = inode.read_all();
-        ProcessControlBlock::new(v.as_slice())
-    };
+        TaskControlBlock::new(v.as_slice())
+    });
 }
-
+///Add init process to the manager
 pub fn add_initproc() {
-    let _initproc = INITPROC.clone();
-}
-
-pub fn check_signals_of_current() -> Option<(i32, &'static str)> {
-    let process = current_process();
-    let process_inner = process.inner_exclusive_access();
-    process_inner.signals.check_error()
-}
-
-pub fn current_add_signal(signal: SignalFlags) {
-    let process = current_process();
-    let mut process_inner = process.inner_exclusive_access();
-    process_inner.signals |= signal;
+    add_task(INITPROC.clone());
 }
diff --git a/os/src/task/pid.rs b/os/src/task/pid.rs
new file mode 100644
index 0000000..f0a5e2a
--- /dev/null
+++ b/os/src/task/pid.rs
@@ -0,0 +1,111 @@
+//!Implementation of [`PidAllocator`]
+use crate::config::{KERNEL_STACK_SIZE, PAGE_SIZE, TRAMPOLINE};
+use crate::mm::{KERNEL_SPACE, MapPermission, VirtAddr};
+use crate::sync::UPSafeCell;
+use alloc::vec::Vec;
+use lazy_static::*;
+///Pid Allocator struct
+pub struct PidAllocator {
+    current: usize,
+    recycled: Vec<usize>,
+}
+
+impl PidAllocator {
+    ///Create an empty `PidAllocator`
+    pub fn new() -> Self {
+        PidAllocator {
+            current: 0,
+            recycled: Vec::new(),
+        }
+    }
+    ///Allocate a pid
+    pub fn alloc(&mut self) -> PidHandle {
+        if let Some(pid) = self.recycled.pop() {
+            PidHandle(pid)
+        } else {
+            self.current += 1;
+            PidHandle(self.current - 1)
+        }
+    }
+    ///Recycle a pid
+    pub fn dealloc(&mut self, pid: usize) {
+        assert!(pid < self.current);
+        assert!(
+            !self.recycled.iter().any(|ppid| *ppid == pid),
+            "pid {} has been deallocated!",
+            pid
+        );
+        self.recycled.push(pid);
+    }
+}
+
+lazy_static! {
+    pub static ref PID_ALLOCATOR: UPSafeCell<PidAllocator> =
+        unsafe { UPSafeCell::new(PidAllocator::new()) };
+}
+///Bind pid lifetime to `PidHandle`
+pub struct PidHandle(pub usize);
+
+impl Drop for PidHandle {
+    fn drop(&mut self) {
+        //println!("drop pid {}", self.0);
+        PID_ALLOCATOR.exclusive_access().dealloc(self.0);
+    }
+}
+///Allocate a pid from PID_ALLOCATOR
+pub fn pid_alloc() -> PidHandle {
+    PID_ALLOCATOR.exclusive_access().alloc()
+}
+
+/// Return (bottom, top) of a kernel stack in kernel space.
+pub fn kernel_stack_position(app_id: usize) -> (usize, usize) {
+    let top = TRAMPOLINE - app_id * (KERNEL_STACK_SIZE + PAGE_SIZE);
+    let bottom = top - KERNEL_STACK_SIZE;
+    (bottom, top)
+}
+///Kernelstack for app
+pub struct KernelStack {
+    pid: usize,
+}
+
+impl KernelStack {
+    ///Create a kernelstack from pid
+    pub fn new(pid_handle: &PidHandle) -> Self {
+        let pid = pid_handle.0;
+        let (kernel_stack_bottom, kernel_stack_top) = kernel_stack_position(pid);
+        KERNEL_SPACE.exclusive_access().insert_framed_area(
+            kernel_stack_bottom.into(),
+            kernel_stack_top.into(),
+            MapPermission::R | MapPermission::W,
+        );
+        KernelStack { pid: pid_handle.0 }
+    }
+    #[allow(unused)]
+    ///Push a value on top of kernelstack
+    pub fn push_on_top<T>(&self, value: T) -> *mut T
+    where
+        T: Sized,
+    {
+        let kernel_stack_top = self.get_top();
+        let ptr_mut = (kernel_stack_top - core::mem::size_of::<T>()) as *mut T;
+        unsafe {
+            *ptr_mut = value;
+        }
+        ptr_mut
+    }
+    ///Get the value on the top of kernelstack
+    pub fn get_top(&self) -> usize {
+        let (_, kernel_stack_top) = kernel_stack_position(self.pid);
+        kernel_stack_top
+    }
+}
+
+impl Drop for KernelStack {
+    fn drop(&mut self) {
+        let (kernel_stack_bottom, _) = kernel_stack_position(self.pid);
+        let kernel_stack_bottom_va: VirtAddr = kernel_stack_bottom.into();
+        KERNEL_SPACE
+            .exclusive_access()
+            .remove_area_with_start_vpn(kernel_stack_bottom_va.into());
+    }
+}
diff --git a/os/src/task/process.rs b/os/src/task/process.rs
deleted file mode 100644
index b3976b7..0000000
--- a/os/src/task/process.rs
+++ /dev/null
@@ -1,258 +0,0 @@
-use super::id::RecycleAllocator;
-use super::manager::insert_into_pid2process;
-use super::TaskControlBlock;
-use super::{add_task, SignalFlags};
-use super::{pid_alloc, PidHandle};
-use crate::fs::{File, Stdin, Stdout};
-use crate::mm::{translated_refmut, MemorySet, KERNEL_SPACE};
-use crate::sync::{Condvar, Mutex, Semaphore, UPIntrFreeCell, UPIntrRefMut};
-use crate::trap::{trap_handler, TrapContext};
-use alloc::string::String;
-use alloc::sync::{Arc, Weak};
-use alloc::vec;
-use alloc::vec::Vec;
-
-pub struct ProcessControlBlock {
-    // immutable
-    pub pid: PidHandle,
-    // mutable
-    inner: UPIntrFreeCell<ProcessControlBlockInner>,
-}
-
-pub struct ProcessControlBlockInner {
-    pub is_zombie: bool,
-    pub memory_set: MemorySet,
-    pub parent: Option<Weak<ProcessControlBlock>>,
-    pub children: Vec<Arc<ProcessControlBlock>>,
-    pub exit_code: i32,
-    pub fd_table: Vec<Option<Arc<dyn File + Send + Sync>>>,
-    pub signals: SignalFlags,
-    pub tasks: Vec<Option<Arc<TaskControlBlock>>>,
-    pub task_res_allocator: RecycleAllocator,
-    pub mutex_list: Vec<Option<Arc<dyn Mutex>>>,
-    pub semaphore_list: Vec<Option<Arc<Semaphore>>>,
-    pub condvar_list: Vec<Option<Arc<Condvar>>>,
-}
-
-impl ProcessControlBlockInner {
-    #[allow(unused)]
-    pub fn get_user_token(&self) -> usize {
-        self.memory_set.token()
-    }
-
-    pub fn alloc_fd(&mut self) -> usize {
-        if let Some(fd) = (0..self.fd_table.len()).find(|fd| self.fd_table[*fd].is_none()) {
-            fd
-        } else {
-            self.fd_table.push(None);
-            self.fd_table.len() - 1
-        }
-    }
-
-    pub fn alloc_tid(&mut self) -> usize {
-        self.task_res_allocator.alloc()
-    }
-
-    pub fn dealloc_tid(&mut self, tid: usize) {
-        self.task_res_allocator.dealloc(tid)
-    }
-
-    pub fn thread_count(&self) -> usize {
-        self.tasks.len()
-    }
-
-    pub fn get_task(&self, tid: usize) -> Arc<TaskControlBlock> {
-        self.tasks[tid].as_ref().unwrap().clone()
-    }
-}
-
-impl ProcessControlBlock {
-    pub fn inner_exclusive_access(&self) -> UPIntrRefMut<'_, ProcessControlBlockInner> {
-        self.inner.exclusive_access()
-    }
-
-    pub fn new(elf_data: &[u8]) -> Arc<Self> {
-        // memory_set with elf program headers/trampoline/trap context/user stack
-        let (memory_set, ustack_base, entry_point) = MemorySet::from_elf(elf_data);
-        // allocate a pid
-        let pid_handle = pid_alloc();
-        let process = Arc::new(Self {
-            pid: pid_handle,
-            inner: unsafe {
-                UPIntrFreeCell::new(ProcessControlBlockInner {
-                    is_zombie: false,
-                    memory_set,
-                    parent: None,
-                    children: Vec::new(),
-                    exit_code: 0,
-                    fd_table: vec![
-                        // 0 -> stdin
-                        Some(Arc::new(Stdin)),
-                        // 1 -> stdout
-                        Some(Arc::new(Stdout)),
-                        // 2 -> stderr
-                        Some(Arc::new(Stdout)),
-                    ],
-                    signals: SignalFlags::empty(),
-                    tasks: Vec::new(),
-                    task_res_allocator: RecycleAllocator::new(),
-                    mutex_list: Vec::new(),
-                    semaphore_list: Vec::new(),
-                    condvar_list: Vec::new(),
-                })
-            },
-        });
-        // create a main thread, we should allocate ustack and trap_cx here
-        let task = Arc::new(TaskControlBlock::new(
-            Arc::clone(&process),
-            ustack_base,
-            true,
-        ));
-        // prepare trap_cx of main thread
-        let task_inner = task.inner_exclusive_access();
-        let trap_cx = task_inner.get_trap_cx();
-        let ustack_top = task_inner.res.as_ref().unwrap().ustack_top();
-        let kstack_top = task.kstack.get_top();
-        drop(task_inner);
-        *trap_cx = TrapContext::app_init_context(
-            entry_point,
-            ustack_top,
-            KERNEL_SPACE.exclusive_access().token(),
-            kstack_top,
-            trap_handler as usize,
-        );
-        // add main thread to the process
-        let mut process_inner = process.inner_exclusive_access();
-        process_inner.tasks.push(Some(Arc::clone(&task)));
-        drop(process_inner);
-        insert_into_pid2process(process.getpid(), Arc::clone(&process));
-        // add main thread to scheduler
-        add_task(task);
-        process
-    }
-
-    /// Only support processes with a single thread.
-    pub fn exec(self: &Arc<Self>, elf_data: &[u8], args: Vec<String>) {
-        assert_eq!(self.inner_exclusive_access().thread_count(), 1);
-        // memory_set with elf program headers/trampoline/trap context/user stack
-        let (memory_set, ustack_base, entry_point) = MemorySet::from_elf(elf_data);
-        let new_token = memory_set.token();
-        // substitute memory_set
-        self.inner_exclusive_access().memory_set = memory_set;
-        // then we alloc user resource for main thread again
-        // since memory_set has been changed
-        let task = self.inner_exclusive_access().get_task(0);
-        let mut task_inner = task.inner_exclusive_access();
-        task_inner.res.as_mut().unwrap().ustack_base = ustack_base;
-        task_inner.res.as_mut().unwrap().alloc_user_res();
-        task_inner.trap_cx_ppn = task_inner.res.as_mut().unwrap().trap_cx_ppn();
-        // push arguments on user stack
-        let mut user_sp = task_inner.res.as_mut().unwrap().ustack_top();
-        user_sp -= (args.len() + 1) * core::mem::size_of::<usize>();
-        let argv_base = user_sp;
-        let mut argv: Vec<_> = (0..=args.len())
-            .map(|arg| {
-                translated_refmut(
-                    new_token,
-                    (argv_base + arg * core::mem::size_of::<usize>()) as *mut usize,
-                )
-            })
-            .collect();
-        *argv[args.len()] = 0;
-        for i in 0..args.len() {
-            user_sp -= args[i].len() + 1;
-            *argv[i] = user_sp;
-            let mut p = user_sp;
-            for c in args[i].as_bytes() {
-                *translated_refmut(new_token, p as *mut u8) = *c;
-                p += 1;
-            }
-            *translated_refmut(new_token, p as *mut u8) = 0;
-        }
-        // make the user_sp aligned to 8B for k210 platform
-        user_sp -= user_sp % core::mem::size_of::<usize>();
-        // initialize trap_cx
-        let mut trap_cx = TrapContext::app_init_context(
-            entry_point,
-            user_sp,
-            KERNEL_SPACE.exclusive_access().token(),
-            task.kstack.get_top(),
-            trap_handler as usize,
-        );
-        trap_cx.x[10] = args.len();
-        trap_cx.x[11] = argv_base;
-        *task_inner.get_trap_cx() = trap_cx;
-    }
-
-    /// Only support processes with a single thread.
-    pub fn fork(self: &Arc<Self>) -> Arc<Self> {
-        let mut parent = self.inner_exclusive_access();
-        assert_eq!(parent.thread_count(), 1);
-        // clone parent's memory_set completely including trampoline/ustacks/trap_cxs
-        let memory_set = MemorySet::from_existed_user(&parent.memory_set);
-        // alloc a pid
-        let pid = pid_alloc();
-        // copy fd table
-        let mut new_fd_table: Vec<Option<Arc<dyn File + Send + Sync>>> = Vec::new();
-        for fd in parent.fd_table.iter() {
-            if let Some(file) = fd {
-                new_fd_table.push(Some(file.clone()));
-            } else {
-                new_fd_table.push(None);
-            }
-        }
-        // create child process pcb
-        let child = Arc::new(Self {
-            pid,
-            inner: unsafe {
-                UPIntrFreeCell::new(ProcessControlBlockInner {
-                    is_zombie: false,
-                    memory_set,
-                    parent: Some(Arc::downgrade(self)),
-                    children: Vec::new(),
-                    exit_code: 0,
-                    fd_table: new_fd_table,
-                    signals: SignalFlags::empty(),
-                    tasks: Vec::new(),
-                    task_res_allocator: RecycleAllocator::new(),
-                    mutex_list: Vec::new(),
-                    semaphore_list: Vec::new(),
-                    condvar_list: Vec::new(),
-                })
-            },
-        });
-        // add child
-        parent.children.push(Arc::clone(&child));
-        // create main thread of child process
-        let task = Arc::new(TaskControlBlock::new(
-            Arc::clone(&child),
-            parent
-                .get_task(0)
-                .inner_exclusive_access()
-                .res
-                .as_ref()
-                .unwrap()
-                .ustack_base(),
-            // here we do not allocate trap_cx or ustack again
-            // but mention that we allocate a new kstack here
-            false,
-        ));
-        // attach task to child process
-        let mut child_inner = child.inner_exclusive_access();
-        child_inner.tasks.push(Some(Arc::clone(&task)));
-        drop(child_inner);
-        // modify kstack_top in trap_cx of this thread
-        let task_inner = task.inner_exclusive_access();
-        let trap_cx = task_inner.get_trap_cx();
-        trap_cx.kernel_sp = task.kstack.get_top();
-        drop(task_inner);
-        insert_into_pid2process(child.getpid(), Arc::clone(&child));
-        // add this thread to scheduler
-        add_task(task);
-        child
-    }
-
-    pub fn getpid(&self) -> usize {
-        self.pid.0
-    }
-}
diff --git a/os/src/task/processor.rs b/os/src/task/processor.rs
index 96361d7..7c05a21 100644
--- a/os/src/task/processor.rs
+++ b/os/src/task/processor.rs
@@ -1,110 +1,92 @@
+//!Implementation of [`Processor`] and Intersection of control flow
 use super::__switch;
-use super::{fetch_task, TaskStatus};
-use super::{ProcessControlBlock, TaskContext, TaskControlBlock};
-use crate::sync::UPIntrFreeCell;
+use super::{TaskContext, TaskControlBlock};
+use super::{TaskStatus, fetch_task};
+use crate::sync::UPSafeCell;
 use crate::trap::TrapContext;
 use alloc::sync::Arc;
-use core::arch::asm;
 use lazy_static::*;
-
+///Processor management structure
 pub struct Processor {
+    ///The task currently executing on the current processor
     current: Option<Arc<TaskControlBlock>>,
+    ///The basic control flow of each core, helping to select and switch process
     idle_task_cx: TaskContext,
 }
 
 impl Processor {
+    ///Create an empty Processor
     pub fn new() -> Self {
         Self {
             current: None,
             idle_task_cx: TaskContext::zero_init(),
         }
     }
+    ///Get mutable reference to `idle_task_cx`
     fn get_idle_task_cx_ptr(&mut self) -> *mut TaskContext {
         &mut self.idle_task_cx as *mut _
     }
+    ///Get current task in moving semanteme
     pub fn take_current(&mut self) -> Option<Arc<TaskControlBlock>> {
         self.current.take()
     }
+    ///Get current task in cloning semanteme
     pub fn current(&self) -> Option<Arc<TaskControlBlock>> {
         self.current.as_ref().map(Arc::clone)
     }
 }
 
 lazy_static! {
-    pub static ref PROCESSOR: UPIntrFreeCell<Processor> =
-        unsafe { UPIntrFreeCell::new(Processor::new()) };
+    pub static ref PROCESSOR: UPSafeCell<Processor> = unsafe { UPSafeCell::new(Processor::new()) };
 }
-
+///The main part of process execution and scheduling
+///Loop `fetch_task` to get the process that needs to run, and switch the process through `__switch`
 pub fn run_tasks() {
     loop {
         let mut processor = PROCESSOR.exclusive_access();
         if let Some(task) = fetch_task() {
             let idle_task_cx_ptr = processor.get_idle_task_cx_ptr();
             // access coming task TCB exclusively
-            let next_task_cx_ptr = task.inner.exclusive_session(|task_inner| {
-                task_inner.task_status = TaskStatus::Running;
-                &task_inner.task_cx as *const TaskContext
-            });
+            let mut task_inner = task.inner_exclusive_access();
+            let next_task_cx_ptr = &task_inner.task_cx as *const TaskContext;
+            task_inner.task_status = TaskStatus::Running;
+            drop(task_inner);
+            // release coming task TCB manually
             processor.current = Some(task);
             // release processor manually
             drop(processor);
             unsafe {
                 __switch(idle_task_cx_ptr, next_task_cx_ptr);
             }
-        } else {
-            println!("no tasks available in run_tasks");
         }
     }
 }
-
+///Take the current task,leaving a None in its place
 pub fn take_current_task() -> Option<Arc<TaskControlBlock>> {
     PROCESSOR.exclusive_access().take_current()
 }
-
+///Get running task
 pub fn current_task() -> Option<Arc<TaskControlBlock>> {
     PROCESSOR.exclusive_access().current()
 }
-
-pub fn current_process() -> Arc<ProcessControlBlock> {
-    current_task().unwrap().process.upgrade().unwrap()
-}
-
+///Get token of the address space of current task
 pub fn current_user_token() -> usize {
     let task = current_task().unwrap();
-    task.get_user_token()
+    let token = task.inner_exclusive_access().get_user_token();
+    token
 }
-
+///Get the mutable reference to trap context of current task
 pub fn current_trap_cx() -> &'static mut TrapContext {
     current_task()
         .unwrap()
         .inner_exclusive_access()
         .get_trap_cx()
 }
-
-pub fn current_trap_cx_user_va() -> usize {
-    current_task()
-        .unwrap()
-        .inner_exclusive_access()
-        .res
-        .as_ref()
-        .unwrap()
-        .trap_cx_user_va()
-}
-
-pub fn current_kstack_top() -> usize {
-    if let Some(task) = current_task() {
-        task.kstack.get_top()
-    } else {
-        let mut boot_stack_top;
-        unsafe { asm!("la {},boot_stack_top",out(reg) boot_stack_top) };
-        boot_stack_top
-    }
-    // current_task().unwrap().kstack.get_top()
-}
-
+///Return to idle control flow for new scheduling
 pub fn schedule(switched_task_cx_ptr: *mut TaskContext) {
-    let idle_task_cx_ptr =
-        PROCESSOR.exclusive_session(|processor| processor.get_idle_task_cx_ptr());
+    let mut processor = PROCESSOR.exclusive_access();
+    let idle_task_cx_ptr = processor.get_idle_task_cx_ptr();
+    drop(processor);
     unsafe {
         __switch(switched_task_cx_ptr, idle_task_cx_ptr);
     }
diff --git a/os/src/task/signal.rs b/os/src/task/signal.rs
deleted file mode 100644
index 46f1ad9..0000000
--- a/os/src/task/signal.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-use bitflags::*;
-
-bitflags! {
-    pub struct SignalFlags: u32 {
-        const SIGINT    = 1 << 2;
-        const SIGILL    = 1 << 4;
-        const SIGABRT   = 1 << 6;
-        const SIGFPE    = 1 << 8;
-        const SIGSEGV   = 1 << 11;
-    }
-}
-
-impl SignalFlags {
-    pub fn check_error(&self) -> Option<(i32, &'static str)> {
-        if self.contains(Self::SIGINT) {
-            Some((-2, "Killed, SIGINT=2"))
-        } else if self.contains(Self::SIGILL) {
-            Some((-4, "Illegal Instruction, SIGILL=4"))
-        } else if self.contains(Self::SIGABRT) {
-            Some((-6, "Aborted, SIGABRT=6"))
-        } else if self.contains(Self::SIGFPE) {
-            Some((-8, "Erroneous Arithmetic Operation, SIGFPE=8"))
-        } else if self.contains(Self::SIGSEGV) {
-            Some((-11, "Segmentation Fault, SIGSEGV=11"))
-        } else {
-            None
-        }
-    }
-}
diff --git a/os/src/task/switch.rs b/os/src/task/switch.rs
index 59f8b1a..8f69fdf 100644
--- a/os/src/task/switch.rs
+++ b/os/src/task/switch.rs
@@ -1,8 +1,14 @@
+//!Wrap `switch.S` as a function
 use super::TaskContext;
 use core::arch::global_asm;
 
 global_asm!(include_str!("switch.S"));
 
-extern "C" {
-    pub fn __switch(current_task_cx_ptr: *mut TaskContext, next_task_cx_ptr: *const TaskContext);
+unsafe extern "C" {
+    /// Switch to the context of `next_task_cx_ptr`, saving the current context
+    /// in `current_task_cx_ptr`.
+    pub unsafe fn __switch(
+        current_task_cx_ptr: *mut TaskContext,
+        next_task_cx_ptr: *const TaskContext,
+    );
 }
diff --git a/os/src/task/task.rs b/os/src/task/task.rs
index ffc5c0e..87d287a 100644
--- a/os/src/task/task.rs
+++ b/os/src/task/task.rs
@@ -1,74 +1,191 @@
-use super::id::TaskUserRes;
-use super::{kstack_alloc, KernelStack, ProcessControlBlock, TaskContext};
-use crate::trap::TrapContext;
-use crate::{
-    mm::PhysPageNum,
-    sync::{UPIntrFreeCell, UPIntrRefMut},
-};
+//!Implementation of [`TaskControlBlock`]
+use super::TaskContext;
+use super::{KernelStack, PidHandle, pid_alloc};
+use crate::config::TRAP_CONTEXT;
+use crate::fs::{File, Stdin, Stdout};
+use crate::mm::{KERNEL_SPACE, MemorySet, PhysPageNum, VirtAddr};
+use crate::sync::UPSafeCell;
+use crate::trap::{TrapContext, trap_handler};
 use alloc::sync::{Arc, Weak};
+use alloc::vec;
+use alloc::vec::Vec;
+use core::cell::RefMut;
 
 pub struct TaskControlBlock {
     // immutable
-    pub process: Weak<ProcessControlBlock>,
-    pub kstack: KernelStack,
+    pub pid: PidHandle,
+    pub kernel_stack: KernelStack,
     // mutable
-    pub inner: UPIntrFreeCell<TaskControlBlockInner>,
-}
-
-impl TaskControlBlock {
-    pub fn inner_exclusive_access(&self) -> UPIntrRefMut<'_, TaskControlBlockInner> {
-        self.inner.exclusive_access()
-    }
-
-    pub fn get_user_token(&self) -> usize {
-        let process = self.process.upgrade().unwrap();
-        let inner = process.inner_exclusive_access();
-        inner.memory_set.token()
-    }
+    inner: UPSafeCell<TaskControlBlockInner>,
 }
 
 pub struct TaskControlBlockInner {
-    pub res: Option<TaskUserRes>,
     pub trap_cx_ppn: PhysPageNum,
+    #[allow(unused)]
+    pub base_size: usize,
     pub task_cx: TaskContext,
     pub task_status: TaskStatus,
-    pub exit_code: Option<i32>,
+    pub memory_set: MemorySet,
+    pub parent: Option<Weak<TaskControlBlock>>,
+    pub children: Vec<Arc<TaskControlBlock>>,
+    pub exit_code: i32,
+    pub fd_table: Vec<Option<Arc<dyn File + Send + Sync>>>,
+    
+    // New: User
+    pub user: String,
 }
 
 impl TaskControlBlockInner {
     pub fn get_trap_cx(&self) -> &'static mut TrapContext {
         self.trap_cx_ppn.get_mut()
     }
-
-    #[allow(unused)]
+    pub fn get_user_token(&self) -> usize {
+        self.memory_set.token()
+    }
     fn get_status(&self) -> TaskStatus {
         self.task_status
     }
+    pub fn is_zombie(&self) -> bool {
+        self.get_status() == TaskStatus::Zombie
+    }
+    pub fn alloc_fd(&mut self) -> usize {
+        if let Some(fd) = (0..self.fd_table.len()).find(|fd| self.fd_table[*fd].is_none()) {
+            fd
+        } else {
+            self.fd_table.push(None);
+            self.fd_table.len() - 1
+        }
+    }
 }
 
 impl TaskControlBlock {
-    pub fn new(
-        process: Arc<ProcessControlBlock>,
-        ustack_base: usize,
-        alloc_user_res: bool,
-    ) -> Self {
-        let res = TaskUserRes::new(Arc::clone(&process), ustack_base, alloc_user_res);
-        let trap_cx_ppn = res.trap_cx_ppn();
-        let kstack = kstack_alloc();
-        let kstack_top = kstack.get_top();
-        Self {
-            process: Arc::downgrade(&process),
-            kstack,
+    pub fn inner_exclusive_access(&self) -> RefMut<'_, TaskControlBlockInner> {
+        self.inner.exclusive_access()
+    }
+    pub fn new(elf_data: &[u8]) -> Self {
+        // memory_set with elf program headers/trampoline/trap context/user stack
+        let (memory_set, user_sp, entry_point) = MemorySet::from_elf(elf_data);
+        let trap_cx_ppn = memory_set
+            .translate(VirtAddr::from(TRAP_CONTEXT).into())
+            .unwrap()
+            .ppn();
+        // alloc a pid and a kernel stack in kernel space
+        let pid_handle = pid_alloc();
+        let kernel_stack = KernelStack::new(&pid_handle);
+        let kernel_stack_top = kernel_stack.get_top();
+        let task_control_block = Self {
+            pid: pid_handle,
+            kernel_stack,
             inner: unsafe {
-                UPIntrFreeCell::new(TaskControlBlockInner {
-                    res: Some(res),
+                UPSafeCell::new(TaskControlBlockInner {
                     trap_cx_ppn,
-                    task_cx: TaskContext::goto_trap_return(kstack_top),
+                    base_size: user_sp,
+                    task_cx: TaskContext::goto_trap_return(kernel_stack_top),
                     task_status: TaskStatus::Ready,
-                    exit_code: None,
+                    memory_set,
+                    parent: None,
+                    children: Vec::new(),
+                    exit_code: 0,
+                    fd_table: vec![
+                        // 0 -> stdin
+                        Some(Arc::new(Stdin)),
+                        // 1 -> stdout
+                        Some(Arc::new(Stdout)),
+                        // 2 -> stderr
+                        Some(Arc::new(Stdout)),
+                    ],
                 })
             },
+        };
+        // prepare TrapContext in user space
+        let trap_cx = task_control_block.inner_exclusive_access().get_trap_cx();
+        *trap_cx = TrapContext::app_init_context(
+            entry_point,
+            user_sp,
+            KERNEL_SPACE.exclusive_access().token(),
+            kernel_stack_top,
+            trap_handler as usize,
+        );
+        task_control_block
+    }
+    pub fn exec(&self, elf_data: &[u8]) {
+        // memory_set with elf program headers/trampoline/trap context/user stack
+        let (memory_set, user_sp, entry_point) = MemorySet::from_elf(elf_data);
+        let trap_cx_ppn = memory_set
+            .translate(VirtAddr::from(TRAP_CONTEXT).into())
+            .unwrap()
+            .ppn();
+
+        // **** access current TCB exclusively
+        let mut inner = self.inner_exclusive_access();
+        // substitute memory_set
+        inner.memory_set = memory_set;
+        // update trap_cx ppn
+        inner.trap_cx_ppn = trap_cx_ppn;
+        // initialize trap_cx
+        let trap_cx = TrapContext::app_init_context(
+            entry_point,
+            user_sp,
+            KERNEL_SPACE.exclusive_access().token(),
+            self.kernel_stack.get_top(),
+            trap_handler as usize,
+        );
+        *inner.get_trap_cx() = trap_cx;
+        // **** release current PCB
+    }
+    pub fn fork(self: &Arc<TaskControlBlock>) -> Arc<TaskControlBlock> {
+        // ---- hold parent PCB lock
+        let mut parent_inner = self.inner_exclusive_access();
+        // copy user space(include trap context)
+        let memory_set = MemorySet::from_existed_user(&parent_inner.memory_set);
+        let trap_cx_ppn = memory_set
+            .translate(VirtAddr::from(TRAP_CONTEXT).into())
+            .unwrap()
+            .ppn();
+        // alloc a pid and a kernel stack in kernel space
+        let pid_handle = pid_alloc();
+        let kernel_stack = KernelStack::new(&pid_handle);
+        let kernel_stack_top = kernel_stack.get_top();
+        // copy fd table
+        let mut new_fd_table: Vec<Option<Arc<dyn File + Send + Sync>>> = Vec::new();
+        for fd in parent_inner.fd_table.iter() {
+            if let Some(file) = fd {
+                new_fd_table.push(Some(file.clone()));
+            } else {
+                new_fd_table.push(None);
+            }
         }
+        let task_control_block = Arc::new(TaskControlBlock {
+            pid: pid_handle,
+            kernel_stack,
+            inner: unsafe {
+                UPSafeCell::new(TaskControlBlockInner {
+                    trap_cx_ppn,
+                    base_size: parent_inner.base_size,
+                    task_cx: TaskContext::goto_trap_return(kernel_stack_top),
+                    task_status: TaskStatus::Ready,
+                    memory_set,
+                    parent: Some(Arc::downgrade(self)),
+                    children: Vec::new(),
+                    exit_code: 0,
+                    fd_table: new_fd_table,
+                    user: username.to_string(),  // Init User name
+                })
+            },
+        });
+        // add child
+        parent_inner.children.push(task_control_block.clone());
+        // modify kernel_sp in trap_cx
+        // **** access child PCB exclusively
+        let trap_cx = task_control_block.inner_exclusive_access().get_trap_cx();
+        trap_cx.kernel_sp = kernel_stack_top;
+        // return
+        task_control_block
+        // **** release child PCB
+        // ---- release parent PCB
+    }
+    pub fn getpid(&self) -> usize {
+        self.pid.0
     }
 }
 
@@ -76,5 +193,5 @@ impl TaskControlBlock {
 pub enum TaskStatus {
     Ready,
     Running,
-    Blocked,
+    Zombie,
 }
diff --git a/os/src/timer.rs b/os/src/timer.rs
index 83c969d..50ce53a 100644
--- a/os/src/timer.rs
+++ b/os/src/timer.rs
@@ -1,74 +1,20 @@
-use core::cmp::Ordering;
+//! RISC-V timer-related functionality
 
 use crate::config::CLOCK_FREQ;
 use crate::sbi::set_timer;
-use crate::sync::UPIntrFreeCell;
-use crate::task::{wakeup_task, TaskControlBlock};
-use alloc::collections::BinaryHeap;
-use alloc::sync::Arc;
-use lazy_static::*;
 use riscv::register::time;
 
 const TICKS_PER_SEC: usize = 100;
 const MSEC_PER_SEC: usize = 1000;
-
+///get current time
 pub fn get_time() -> usize {
     time::read()
 }
-
+/// get current time in microseconds
 pub fn get_time_ms() -> usize {
     time::read() / (CLOCK_FREQ / MSEC_PER_SEC)
 }
-
+/// set the next timer interrupt
 pub fn set_next_trigger() {
     set_timer(get_time() + CLOCK_FREQ / TICKS_PER_SEC);
 }
-
-pub struct TimerCondVar {
-    pub expire_ms: usize,
-    pub task: Arc<TaskControlBlock>,
-}
-
-impl PartialEq for TimerCondVar {
-    fn eq(&self, other: &Self) -> bool {
-        self.expire_ms == other.expire_ms
-    }
-}
-impl Eq for TimerCondVar {}
-impl PartialOrd for TimerCondVar {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        let a = -(self.expire_ms as isize);
-        let b = -(other.expire_ms as isize);
-        Some(a.cmp(&b))
-    }
-}
-
-impl Ord for TimerCondVar {
-    fn cmp(&self, other: &Self) -> Ordering {
-        self.partial_cmp(other).unwrap()
-    }
-}
-
-lazy_static! {
-    static ref TIMERS: UPIntrFreeCell<BinaryHeap<TimerCondVar>> =
-        unsafe { UPIntrFreeCell::new(BinaryHeap::<TimerCondVar>::new()) };
-}
-
-pub fn add_timer(expire_ms: usize, task: Arc<TaskControlBlock>) {
-    let mut timers = TIMERS.exclusive_access();
-    timers.push(TimerCondVar { expire_ms, task });
-}
-
-pub fn check_timer() {
-    let current_ms = get_time_ms();
-    TIMERS.exclusive_session(|timers| {
-        while let Some(timer) = timers.peek() {
-            if timer.expire_ms <= current_ms {
-                wakeup_task(Arc::clone(&timer.task));
-                timers.pop();
-            } else {
-                break;
-            }
-        }
-    });
-}
diff --git a/os/src/trap/context.rs b/os/src/trap/context.rs
index 011b7fb..5f968e5 100644
--- a/os/src/trap/context.rs
+++ b/os/src/trap/context.rs
@@ -1,20 +1,30 @@
-use riscv::register::sstatus::{self, Sstatus, SPP};
+//! Implementation of [`TrapContext`]
+use riscv::register::sstatus::{self, SPP, Sstatus};
 
 #[repr(C)]
 #[derive(Debug)]
+///trap context structure containing sstatus, sepc and registers
 pub struct TrapContext {
+    /// general regs[0..31]
     pub x: [usize; 32],
+    /// CSR sstatus      
     pub sstatus: Sstatus,
+    /// CSR sepc
     pub sepc: usize,
+    /// Addr of Page Table
     pub kernel_satp: usize,
+    /// kernel stack
     pub kernel_sp: usize,
+    /// Addr of trap_handler function
     pub trap_handler: usize,
 }
 
 impl TrapContext {
+    ///set stack pointer to x_2 reg (sp)
     pub fn set_sp(&mut self, sp: usize) {
         self.x[2] = sp;
     }
+    ///init app context
     pub fn app_init_context(
         entry: usize,
         sp: usize,
diff --git a/os/src/trap/mod.rs b/os/src/trap/mod.rs
index 3287011..26e7895 100644
--- a/os/src/trap/mod.rs
+++ b/os/src/trap/mod.rs
@@ -1,34 +1,40 @@
+//! Trap handling functionality
+//!
+//! For rCore, we have a single trap entry point, namely `__alltraps`. At
+//! initialization in [`init()`], we set the `stvec` CSR to point to it.
+//!
+//! All traps go through `__alltraps`, which is defined in `trap.S`. The
+//! assembly language code does just enough work restore the kernel space
+//! context, ensuring that Rust code safely runs, and transfers control to
+//! [`trap_handler()`].
+//!
+//! It then calls different functionality based on what exactly the exception
+//! was. For example, timer interrupts trigger task preemption, and syscalls go
+//! to [`syscall()`].
 mod context;
 
-use crate::config::TRAMPOLINE;
+use crate::config::{TRAMPOLINE, TRAP_CONTEXT};
 use crate::syscall::syscall;
 use crate::task::{
-    check_signals_of_current, current_add_signal, current_trap_cx, current_trap_cx_user_va,
-    current_user_token, exit_current_and_run_next, suspend_current_and_run_next, SignalFlags,
+    current_trap_cx, current_user_token, exit_current_and_run_next, suspend_current_and_run_next,
 };
-use crate::timer::{check_timer, set_next_trigger};
+use crate::timer::set_next_trigger;
 use core::arch::{asm, global_asm};
 use riscv::register::{
     mtvec::TrapMode,
     scause::{self, Exception, Interrupt, Trap},
-    sie, sip, sscratch, sstatus, stval, stvec,
+    sie, stval, stvec,
 };
 
 global_asm!(include_str!("trap.S"));
-
+/// initialize CSR `stvec` as the entry of `__alltraps`
 pub fn init() {
     set_kernel_trap_entry();
 }
 
 fn set_kernel_trap_entry() {
-    extern "C" {
-        fn __alltraps();
-        fn __alltraps_k();
-    }
-    let __alltraps_k_va = __alltraps_k as usize - __alltraps as usize + TRAMPOLINE;
     unsafe {
-        stvec::write(__alltraps_k_va, TrapMode::Direct);
-        sscratch::write(trap_from_kernel as usize);
+        stvec::write(trap_from_kernel as usize, TrapMode::Direct);
     }
 }
 
@@ -37,39 +43,24 @@ fn set_user_trap_entry() {
         stvec::write(TRAMPOLINE as usize, TrapMode::Direct);
     }
 }
-
+/// enable timer interrupt in sie CSR
 pub fn enable_timer_interrupt() {
     unsafe {
         sie::set_stimer();
     }
 }
 
-fn enable_supervisor_interrupt() {
-    unsafe {
-        sstatus::set_sie();
-    }
-}
-
-fn disable_supervisor_interrupt() {
-    unsafe {
-        sstatus::clear_sie();
-    }
-}
-
-#[no_mangle]
+#[unsafe(no_mangle)]
+/// handle an interrupt, exception, or system call from user space
 pub fn trap_handler() -> ! {
     set_kernel_trap_entry();
     let scause = scause::read();
     let stval = stval::read();
-    // println!("into {:?}", scause.cause());
     match scause.cause() {
         Trap::Exception(Exception::UserEnvCall) => {
             // jump to next instruction anyway
             let mut cx = current_trap_cx();
             cx.sepc += 4;
-
-            enable_supervisor_interrupt();
-
             // get system call return value
             let result = syscall(cx.x[17], [cx.x[10], cx.x[11], cx.x[12]]);
             // cx is changed during sys_exec, so we have to call it again
@@ -82,27 +73,24 @@ pub fn trap_handler() -> ! {
         | Trap::Exception(Exception::InstructionPageFault)
         | Trap::Exception(Exception::LoadFault)
         | Trap::Exception(Exception::LoadPageFault) => {
-            /*
             println!(
                 "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
                 scause.cause(),
                 stval,
                 current_trap_cx().sepc,
             );
-            */
-            current_add_signal(SignalFlags::SIGSEGV);
+            // page fault exit code
+            exit_current_and_run_next(-2);
         }
         Trap::Exception(Exception::IllegalInstruction) => {
-            current_add_signal(SignalFlags::SIGILL);
+            println!("[kernel] IllegalInstruction in application, kernel killed it.");
+            // illegal instruction exit code
+            exit_current_and_run_next(-3);
         }
         Trap::Interrupt(Interrupt::SupervisorTimer) => {
             set_next_trigger();
-            check_timer();
             suspend_current_and_run_next();
         }
-        Trap::Interrupt(Interrupt::SupervisorExternal) => {
-            crate::board::irq_handler();
-        }
         _ => {
             panic!(
                 "Unsupported trap {:?}, stval = {:#x}!",
@@ -111,59 +99,42 @@ pub fn trap_handler() -> ! {
             );
         }
     }
-    // check signals
-    if let Some((errno, msg)) = check_signals_of_current() {
-        println!("[kernel] {}", msg);
-        exit_current_and_run_next(errno);
-    }
+    //println!("before trap_return");
     trap_return();
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
+/// set the new addr of __restore asm function in TRAMPOLINE page,
+/// set the reg a0 = trap_cx_ptr, reg a1 = phy addr of usr page table,
+/// finally, jump to new addr of __restore asm function
 pub fn trap_return() -> ! {
-    disable_supervisor_interrupt();
     set_user_trap_entry();
-    let trap_cx_user_va = current_trap_cx_user_va();
+    let trap_cx_ptr = TRAP_CONTEXT;
     let user_satp = current_user_token();
-    extern "C" {
-        fn __alltraps();
-        fn __restore();
+    unsafe extern "C" {
+        unsafe fn __alltraps();
+        unsafe fn __restore();
     }
     let restore_va = __restore as usize - __alltraps as usize + TRAMPOLINE;
-    //println!("before return");
     unsafe {
         asm!(
             "fence.i",
             "jr {restore_va}",
             restore_va = in(reg) restore_va,
-            in("a0") trap_cx_user_va,
+            in("a0") trap_cx_ptr,
             in("a1") user_satp,
             options(noreturn)
         );
     }
 }
 
-#[no_mangle]
-pub fn trap_from_kernel(_trap_cx: &TrapContext) {
-    let scause = scause::read();
-    let stval = stval::read();
-    match scause.cause() {
-        Trap::Interrupt(Interrupt::SupervisorExternal) => {
-            crate::board::irq_handler();
-        }
-        Trap::Interrupt(Interrupt::SupervisorTimer) => {
-            set_next_trigger();
-            check_timer();
-            // do not schedule now
-        }
-        _ => {
-            panic!(
-                "Unsupported trap from kernel: {:?}, stval = {:#x}!",
-                scause.cause(),
-                stval
-            );
-        }
-    }
+#[unsafe(no_mangle)]
+/// Unimplement: traps/interrupts/exceptions from kernel mode
+/// Todo: Chapter 9: I/O device
+pub fn trap_from_kernel() -> ! {
+    use riscv::register::sepc;
+    println!("stval = {:#x}, sepc = {:#x}", stval::read(), sepc::read());
+    panic!("a trap {:?} from kernel!", scause::read().cause());
 }
 
 pub use context::TrapContext;
diff --git a/os/src/trap/trap.S b/os/src/trap/trap.S
index 407307c..c0e2d15 100644
--- a/os/src/trap/trap.S
+++ b/os/src/trap/trap.S
@@ -8,8 +8,6 @@
     .section .text.trampoline
     .globl __alltraps
     .globl __restore
-    .globl __alltraps_k
-    .globl __restore_k
     .align 2
 __alltraps:
     csrrw sp, sscratch, sp
@@ -69,36 +67,3 @@ __restore:
     # back to user stack
     ld sp, 2*8(sp)
     sret
-
-    .align 2
-__alltraps_k:
-    addi sp, sp, -34*8 
-    sd x1, 1*8(sp)
-    sd x3, 3*8(sp)
-    .set n, 5
-    .rept 27
-        SAVE_GP %n
-        .set n, n+1
-    .endr
-    csrr t0, sstatus
-    csrr t1, sepc
-    sd t0, 32*8(sp)
-    sd t1, 33*8(sp)
-    mv a0, sp
-    csrr t2, sscratch
-    jalr t2
-
-__restore_k:
-    ld t0, 32*8(sp)
-    ld t1, 33*8(sp)
-    csrw sstatus, t0
-    csrw sepc, t1
-    ld x1, 1*8(sp)
-    ld x3, 3*8(sp)
-    .set n, 5
-    .rept 27
-        LOAD_GP %n
-        .set n, n+1
-    .endr
-    addi sp, sp, 34*8
-    sret
diff --git a/ping.py b/ping.py
deleted file mode 100644
index c68fc71..0000000
--- a/ping.py
+++ /dev/null
@@ -1,18 +0,0 @@
-import socket
-import sys
-import time
-
-sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-addr = ('localhost', 26099)
-sock.bind(addr)
-
-
-print("pinging...", file=sys.stderr)
-while True:
-        buf, raddr = sock.recvfrom(4096)
-        print("receive: " + buf.decode("utf-8"))
-        buf = "this is a ping to port 6200!".encode('utf-8')
-        sock.sendto(buf, ("127.0.0.1", 6200))
-        buf = "this is a ping to reply!".encode('utf-8')
-        sock.sendto(buf, raddr)
-        time.sleep(1)
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index c65d258..e6f10a1 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,6 +1,6 @@
 [toolchain]
 profile = "minimal"
 # use the nightly version of the last stable toolchain, see <https://forge.rust-lang.org/>
-channel = "nightly-2024-05-01"
+channel = "nightly-2025-02-18"
 components = ["rust-src", "llvm-tools", "rustfmt", "clippy"]
 targets = ["riscv64gc-unknown-none-elf"]
diff --git a/setenv.sh b/setenv.sh
deleted file mode 100644
index e3842d5..0000000
--- a/setenv.sh
+++ /dev/null
@@ -1,2 +0,0 @@
-export PATH=$(rustc --print sysroot)/bin:$PATH
-export RUST_SRC_PATH=$(rustc --print sysroot)/lib/rustlib/src/rust/library/
diff --git a/user/Cargo.toml b/user/Cargo.toml
index 1d7b2ef..92f3f7e 100644
--- a/user/Cargo.toml
+++ b/user/Cargo.toml
@@ -2,18 +2,17 @@
 name = "user_lib"
 version = "0.1.0"
 authors = ["Yifan Wu <shinbokuow@163.com>"]
-edition = "2018"
+edition = "2024"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
 buddy_system_allocator = "0.6"
 bitflags = "1.2.1"
-riscv = { git = "https://github.com/rcore-os/riscv", features = ["inline-asm"] }
-lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
-embedded-graphics = "0.7.1"
-oorandom ="11"
-virtio-input-decoder = "0.1.4"
 
 [profile.release]
 debug = true
+
+# [features]
+# board_qemu = []
+# board_k210 = []
\ No newline at end of file
diff --git a/user/src/bin/adder.rs b/user/src/bin/adder.rs
deleted file mode 100644
index 1cdce95..0000000
--- a/user/src/bin/adder.rs
+++ /dev/null
@@ -1,58 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use user_lib::{exit, get_time, thread_create, waittid};
-
-static mut A: usize = 0;
-const PER_THREAD_DEFAULT: usize = 10000;
-const THREAD_COUNT_DEFAULT: usize = 16;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-unsafe fn f() -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        critical_section(&mut t);
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-    let start = get_time();
-    let mut v = Vec::new();
-    for _ in 0..thread_count {
-        v.push(thread_create(f as usize, 0) as usize);
-    }
-    for tid in v.into_iter() {
-        waittid(tid);
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_atomic.rs b/user/src/bin/adder_atomic.rs
deleted file mode 100644
index 5e216c6..0000000
--- a/user/src/bin/adder_atomic.rs
+++ /dev/null
@@ -1,75 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use core::sync::atomic::{AtomicBool, Ordering};
-use user_lib::{exit, get_time, thread_create, waittid, yield_};
-
-static mut A: usize = 0;
-static OCCUPIED: AtomicBool = AtomicBool::new(false);
-const PER_THREAD_DEFAULT: usize = 10000;
-const THREAD_COUNT_DEFAULT: usize = 16;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-fn lock() {
-    while OCCUPIED
-        .compare_exchange(false, true, Ordering::Relaxed, Ordering::Relaxed)
-        .is_err()
-    {
-        yield_();
-    }
-}
-
-fn unlock() {
-    OCCUPIED.store(false, Ordering::Relaxed);
-}
-
-unsafe fn f() -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        lock();
-        critical_section(&mut t);
-        unlock();
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-    let start = get_time();
-    let mut v = Vec::new();
-    for _ in 0..thread_count {
-        v.push(thread_create(f as usize, 0) as usize);
-    }
-    for tid in v.into_iter() {
-        waittid(tid);
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_mutex_blocking.rs b/user/src/bin/adder_mutex_blocking.rs
deleted file mode 100644
index 7fcb80b..0000000
--- a/user/src/bin/adder_mutex_blocking.rs
+++ /dev/null
@@ -1,62 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use user_lib::{exit, get_time, thread_create, waittid};
-use user_lib::{mutex_blocking_create, mutex_lock, mutex_unlock};
-
-static mut A: usize = 0;
-const PER_THREAD_DEFAULT: usize = 10000;
-const THREAD_COUNT_DEFAULT: usize = 16;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-unsafe fn f() -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        mutex_lock(0);
-        critical_section(&mut t);
-        mutex_unlock(0);
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-
-    let start = get_time();
-    assert_eq!(mutex_blocking_create(), 0);
-    let mut v = Vec::new();
-    for _ in 0..thread_count {
-        v.push(thread_create(f as usize, 0) as usize);
-    }
-    for tid in v.into_iter() {
-        waittid(tid);
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_mutex_spin.rs b/user/src/bin/adder_mutex_spin.rs
deleted file mode 100644
index f5750af..0000000
--- a/user/src/bin/adder_mutex_spin.rs
+++ /dev/null
@@ -1,63 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use user_lib::{exit, get_time, thread_create, waittid};
-use user_lib::{mutex_create, mutex_lock, mutex_unlock};
-
-static mut A: usize = 0;
-const PER_THREAD_DEFAULT: usize = 10000;
-const THREAD_COUNT_DEFAULT: usize = 16;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-unsafe fn f() -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        mutex_lock(0);
-        critical_section(&mut t);
-        mutex_unlock(0);
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-
-    let start = get_time();
-    assert_eq!(mutex_create(), 0);
-    let mut v = Vec::new();
-    for _ in 0..thread_count {
-        v.push(thread_create(f as usize, 0) as usize);
-    }
-    for tid in v.into_iter() {
-        waittid(tid);
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_peterson_spin.rs b/user/src/bin/adder_peterson_spin.rs
deleted file mode 100644
index 44e8096..0000000
--- a/user/src/bin/adder_peterson_spin.rs
+++ /dev/null
@@ -1,95 +0,0 @@
-//! It only works on a single CPU!
-
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use core::sync::atomic::{compiler_fence, Ordering};
-use user_lib::{exit, get_time, thread_create, waittid};
-
-static mut A: usize = 0;
-static mut FLAG: [bool; 2] = [false; 2];
-static mut TURN: usize = 0;
-const PER_THREAD_DEFAULT: usize = 2000;
-const THREAD_COUNT_DEFAULT: usize = 2;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-unsafe fn lock(id: usize) {
-    FLAG[id] = true;
-    let j = 1 - id;
-    TURN = j;
-    // Tell the compiler not to reorder memory operations
-    // across this fence.
-    compiler_fence(Ordering::SeqCst);
-    // Why do we need to use volatile_read here?
-    // Otherwise the compiler will assume that they will never
-    // be changed on this thread. Thus, they will be accessed
-    // only once!
-    while vload!(FLAG[j]) && vload!(TURN) == j {}
-}
-
-unsafe fn unlock(id: usize) {
-    FLAG[id] = false;
-}
-
-unsafe fn f(id: usize) -> ! {
-    let mut t = 2usize;
-    for _iter in 0..PER_THREAD {
-        lock(id);
-        critical_section(&mut t);
-        unlock(id);
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-
-    // uncomment this if you want to check the assembly
-    // println!(
-    //     "addr: lock={:#x}, unlock={:#x}",
-    //     lock as usize,
-    //     unlock as usize
-    // );
-    let start = get_time();
-    let mut v = Vec::new();
-    assert_eq!(
-        thread_count, 2,
-        "Peterson works when there are only 2 threads."
-    );
-    for id in 0..thread_count {
-        v.push(thread_create(f as usize, id) as usize);
-    }
-    let mut time_cost = Vec::new();
-    for tid in v.iter() {
-        time_cost.push(waittid(*tid));
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_peterson_yield.rs b/user/src/bin/adder_peterson_yield.rs
deleted file mode 100644
index b25adf6..0000000
--- a/user/src/bin/adder_peterson_yield.rs
+++ /dev/null
@@ -1,96 +0,0 @@
-//! It only works on a single CPU!
-
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::{
-    ptr::addr_of_mut,
-    sync::atomic::{compiler_fence, Ordering},
-};
-use user_lib::{exit, get_time, thread_create, waittid, yield_};
-
-static mut A: usize = 0;
-static mut FLAG: [bool; 2] = [false; 2];
-static mut TURN: usize = 0;
-const PER_THREAD_DEFAULT: usize = 2000;
-const THREAD_COUNT_DEFAULT: usize = 2;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-unsafe fn lock(id: usize) {
-    FLAG[id] = true;
-    let j = 1 - id;
-    TURN = j;
-    // Tell the compiler not to reorder memory operations
-    // across this fence.
-    compiler_fence(Ordering::SeqCst);
-    while FLAG[j] && TURN == j {
-        yield_();
-    }
-}
-
-unsafe fn unlock(id: usize) {
-    FLAG[id] = false;
-}
-
-unsafe fn f(id: usize) -> ! {
-    let mut t = 2usize;
-    for _iter in 0..PER_THREAD {
-        lock(id);
-        critical_section(&mut t);
-        unlock(id);
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-
-    // uncomment this if you want to check the assembly
-    // println!(
-    //     "addr: lock={:#x}, unlock={:#x}",
-    //     lock as usize,
-    //     unlock as usize
-    // );
-
-    let start = get_time();
-    let mut v = Vec::new();
-    assert_eq!(
-        thread_count, 2,
-        "Peterson works when there are only 2 threads."
-    );
-    for id in 0..thread_count {
-        v.push(thread_create(f as usize, id) as usize);
-    }
-    let mut time_cost = Vec::new();
-    for tid in v.iter() {
-        time_cost.push(waittid(*tid));
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_simple_spin.rs b/user/src/bin/adder_simple_spin.rs
deleted file mode 100644
index be99d28..0000000
--- a/user/src/bin/adder_simple_spin.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use user_lib::{exit, get_time, thread_create, waittid};
-
-static mut A: usize = 0;
-static mut OCCUPIED: bool = false;
-const PER_THREAD_DEFAULT: usize = 10000;
-const THREAD_COUNT_DEFAULT: usize = 16;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-unsafe fn lock() {
-    while vload!(OCCUPIED) {}
-    OCCUPIED = true;
-}
-
-unsafe fn unlock() {
-    OCCUPIED = false;
-}
-
-unsafe fn f() -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        lock();
-        critical_section(&mut t);
-        unlock();
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-    let start = get_time();
-    let mut v = Vec::new();
-    for _ in 0..thread_count {
-        v.push(thread_create(f as usize, 0) as usize);
-    }
-    for tid in v.into_iter() {
-        waittid(tid);
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/adder_simple_yield.rs b/user/src/bin/adder_simple_yield.rs
deleted file mode 100644
index 2de7924..0000000
--- a/user/src/bin/adder_simple_yield.rs
+++ /dev/null
@@ -1,72 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use user_lib::{exit, get_time, thread_create, waittid, yield_};
-
-static mut A: usize = 0;
-static mut OCCUPIED: bool = false;
-const PER_THREAD_DEFAULT: usize = 10000;
-const THREAD_COUNT_DEFAULT: usize = 16;
-static mut PER_THREAD: usize = 0;
-
-unsafe fn critical_section(t: &mut usize) {
-    let a = addr_of_mut!(A);
-    let cur = a.read_volatile();
-    for _ in 0..500 {
-        *t = (*t) * (*t) % 10007;
-    }
-    a.write_volatile(cur + 1);
-}
-
-unsafe fn lock() {
-    while OCCUPIED {
-        yield_();
-    }
-    OCCUPIED = true;
-}
-
-unsafe fn unlock() {
-    OCCUPIED = false;
-}
-
-unsafe fn f() -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        lock();
-        critical_section(&mut t);
-        unlock();
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let mut thread_count = THREAD_COUNT_DEFAULT;
-    let mut per_thread = PER_THREAD_DEFAULT;
-    if argc >= 2 {
-        thread_count = argv[1].parse().unwrap();
-        if argc >= 3 {
-            per_thread = argv[2].parse().unwrap();
-        }
-    }
-    unsafe {
-        PER_THREAD = per_thread;
-    }
-    let start = get_time();
-    let mut v = Vec::new();
-    for _ in 0..thread_count {
-        v.push(thread_create(f as usize, 0) as usize);
-    }
-    for tid in v.into_iter() {
-        waittid(tid);
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, unsafe { PER_THREAD } * thread_count);
-    0
-}
diff --git a/user/src/bin/barrier_condvar.rs b/user/src/bin/barrier_condvar.rs
deleted file mode 100644
index 7157772..0000000
--- a/user/src/bin/barrier_condvar.rs
+++ /dev/null
@@ -1,83 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use core::cell::UnsafeCell;
-use lazy_static::*;
-use user_lib::{
-    condvar_create, condvar_signal, condvar_wait, exit, mutex_create, mutex_lock, mutex_unlock,
-    thread_create, waittid,
-};
-
-const THREAD_NUM: usize = 3;
-
-struct Barrier {
-    mutex_id: usize,
-    condvar_id: usize,
-    count: UnsafeCell<usize>,
-}
-
-impl Barrier {
-    pub fn new() -> Self {
-        Self {
-            mutex_id: mutex_create() as usize,
-            condvar_id: condvar_create() as usize,
-            count: UnsafeCell::new(0),
-        }
-    }
-    pub fn block(&self) {
-        mutex_lock(self.mutex_id);
-        let count = self.count.get();
-        // SAFETY: Here, the accesses of the count is in the
-        // critical section protected by the mutex.
-        unsafe {
-            *count = *count + 1;
-        }
-        if unsafe { *count } == THREAD_NUM {
-            condvar_signal(self.condvar_id);
-        } else {
-            condvar_wait(self.condvar_id, self.mutex_id);
-            condvar_signal(self.condvar_id);
-        }
-        mutex_unlock(self.mutex_id);
-    }
-}
-
-unsafe impl Sync for Barrier {}
-
-lazy_static! {
-    static ref BARRIER_AB: Barrier = Barrier::new();
-    static ref BARRIER_BC: Barrier = Barrier::new();
-}
-
-fn thread_fn() {
-    for _ in 0..300 {
-        print!("a");
-    }
-    BARRIER_AB.block();
-    for _ in 0..300 {
-        print!("b");
-    }
-    BARRIER_BC.block();
-    for _ in 0..300 {
-        print!("c");
-    }
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut v: Vec<isize> = Vec::new();
-    for _ in 0..THREAD_NUM {
-        v.push(thread_create(thread_fn as usize, 0));
-    }
-    for tid in v.into_iter() {
-        waittid(tid as usize);
-    }
-    println!("\nOK!");
-    0
-}
diff --git a/user/src/bin/barrier_fail.rs b/user/src/bin/barrier_fail.rs
deleted file mode 100644
index 11604ca..0000000
--- a/user/src/bin/barrier_fail.rs
+++ /dev/null
@@ -1,33 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use user_lib::{exit, thread_create, waittid};
-
-const THREAD_NUM: usize = 3;
-
-fn thread_fn() {
-    for ch in 'a'..='c' {
-        for _ in 0..300 {
-            print!("{}", ch);
-        }
-    }
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut v: Vec<isize> = Vec::new();
-    for _ in 0..THREAD_NUM {
-        v.push(thread_create(thread_fn as usize, 0));
-    }
-    for tid in v.into_iter() {
-        waittid(tid as usize);
-    }
-    println!("\nOK!");
-    0
-}
diff --git a/user/src/bin/cat.rs b/user/src/bin/cat.rs
deleted file mode 100644
index fea5a24..0000000
--- a/user/src/bin/cat.rs
+++ /dev/null
@@ -1,32 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use user_lib::{close, open, read, OpenFlags};
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    println!("argc = {}", argc);
-    for (i, arg) in argv.iter().enumerate() {
-        println!("argv[{}] = {}", i, arg);
-    }
-    assert!(argc == 2);
-    let fd = open(argv[1], OpenFlags::RDONLY);
-    if fd == -1 {
-        panic!("Error occurred when opening file");
-    }
-    let fd = fd as usize;
-    let mut buf = [0u8; 256];
-    loop {
-        let size = read(fd, &mut buf) as usize;
-        if size == 0 {
-            break;
-        }
-        print!("{}", core::str::from_utf8(&buf[..size]).unwrap());
-    }
-    close(fd);
-    0
-}
diff --git a/user/src/bin/cat_filea.rs b/user/src/bin/cat_filea.rs
new file mode 100644
index 0000000..20daf77
--- /dev/null
+++ b/user/src/bin/cat_filea.rs
@@ -0,0 +1,27 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+extern crate alloc;
+
+use user_lib::{OpenFlags, close, open, read};
+
+#[unsafe(no_mangle)]
+pub fn main() -> i32 {
+    let fd = open("filea\0", OpenFlags::RDONLY);
+    if fd == -1 {
+        panic!("Error occured when opening file");
+    }
+    let fd = fd as usize;
+    let mut buf = [0u8; 256];
+    loop {
+        let size = read(fd, &mut buf) as usize;
+        if size == 0 {
+            break;
+        }
+        println!("{}", core::str::from_utf8(&buf[..size]).unwrap());
+    }
+    close(fd);
+    0
+}
diff --git a/user/src/bin/cmdline_args.rs b/user/src/bin/cmdline_args.rs
deleted file mode 100644
index 9a22745..0000000
--- a/user/src/bin/cmdline_args.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-#![no_std]
-#![no_main]
-
-extern crate alloc;
-
-#[macro_use]
-extern crate user_lib;
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    println!("argc = {}", argc);
-    for (i, arg) in argv.iter().enumerate() {
-        println!("argv[{}] = {}", i, arg);
-    }
-    0
-}
diff --git a/user/src/bin/condsync_condvar.rs b/user/src/bin/condsync_condvar.rs
deleted file mode 100644
index 78605ad..0000000
--- a/user/src/bin/condsync_condvar.rs
+++ /dev/null
@@ -1,59 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-extern crate alloc;
-
-use alloc::vec;
-use user_lib::exit;
-use user_lib::{
-    condvar_create, condvar_signal, condvar_wait, mutex_blocking_create, mutex_lock, mutex_unlock,
-};
-use user_lib::{sleep, thread_create, waittid};
-
-static mut A: usize = 0;
-
-const CONDVAR_ID: usize = 0;
-const MUTEX_ID: usize = 0;
-
-unsafe fn first() -> ! {
-    sleep(10);
-    println!("First work, Change A --> 1 and wakeup Second");
-    mutex_lock(MUTEX_ID);
-    A = 1;
-    condvar_signal(CONDVAR_ID);
-    mutex_unlock(MUTEX_ID);
-    exit(0)
-}
-
-unsafe fn second() -> ! {
-    println!("Second want to continue,but need to wait A=1");
-    mutex_lock(MUTEX_ID);
-    while A == 0 {
-        println!("Second: A is {}", A);
-        condvar_wait(CONDVAR_ID, MUTEX_ID);
-    }
-    println!("A is {}, Second can work now", A);
-    mutex_unlock(MUTEX_ID);
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    // create condvar & mutex
-    assert_eq!(condvar_create() as usize, CONDVAR_ID);
-    assert_eq!(mutex_blocking_create() as usize, MUTEX_ID);
-    // create threads
-    let threads = vec![
-        thread_create(first as usize, 0),
-        thread_create(second as usize, 0),
-    ];
-    // wait for all threads to complete
-    for thread in threads.iter() {
-        waittid(*thread as usize);
-    }
-    println!("test_condvar passed!");
-    0
-}
diff --git a/user/src/bin/condsync_sem.rs b/user/src/bin/condsync_sem.rs
deleted file mode 100644
index ee08fac..0000000
--- a/user/src/bin/condsync_sem.rs
+++ /dev/null
@@ -1,64 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-extern crate alloc;
-
-use alloc::vec;
-use user_lib::exit;
-use user_lib::{
-    mutex_blocking_create, mutex_lock, mutex_unlock, semaphore_create, semaphore_down, semaphore_up,
-};
-use user_lib::{sleep, thread_create, waittid};
-
-static mut A: usize = 0;
-
-const SEM_ID: usize = 0;
-const MUTEX_ID: usize = 0;
-
-unsafe fn first() -> ! {
-    sleep(10);
-    println!("First work, Change A --> 1 and wakeup Second");
-    mutex_lock(MUTEX_ID);
-    A = 1;
-    semaphore_up(SEM_ID);
-    mutex_unlock(MUTEX_ID);
-    exit(0)
-}
-
-unsafe fn second() -> ! {
-    println!("Second want to continue,but need to wait A=1");
-    loop {
-        mutex_lock(MUTEX_ID);
-        if A == 0 {
-            println!("Second: A is {}", A);
-            mutex_unlock(MUTEX_ID);
-            semaphore_down(SEM_ID);
-        } else {
-            mutex_unlock(MUTEX_ID);
-            break;
-        }
-    }
-    println!("A is {}, Second can work now", A);
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    // create semaphore & mutex
-    assert_eq!(semaphore_create(0) as usize, SEM_ID);
-    assert_eq!(mutex_blocking_create() as usize, MUTEX_ID);
-    // create threads
-    let threads = vec![
-        thread_create(first as usize, 0),
-        thread_create(second as usize, 0),
-    ];
-    // wait for all threads to complete
-    for thread in threads.iter() {
-        waittid(*thread as usize);
-    }
-    println!("test_condvar passed!");
-    0
-}
diff --git a/user/src/bin/count_lines.rs b/user/src/bin/count_lines.rs
deleted file mode 100644
index 276e12e..0000000
--- a/user/src/bin/count_lines.rs
+++ /dev/null
@@ -1,30 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use user_lib::read;
-
-#[no_mangle]
-pub fn main(_argc: usize, _argv: &[&str]) -> i32 {
-    let mut buf = [0u8; 256];
-    let mut lines = 0usize;
-    let mut total_size = 0usize;
-    loop {
-        let len = read(0, &mut buf) as usize;
-        if len == 0 {
-            break;
-        }
-        total_size += len;
-        let string = core::str::from_utf8(&buf[..len]).unwrap();
-        lines += string
-            .chars()
-            .fold(0, |acc, c| acc + if c == '\n' { 1 } else { 0 });
-    }
-    if total_size > 0 {
-        lines += 1;
-    }
-    println!("{}", lines);
-    0
-}
diff --git a/user/src/bin/eisenberg.rs b/user/src/bin/eisenberg.rs
deleted file mode 100644
index 49a1d45..0000000
--- a/user/src/bin/eisenberg.rs
+++ /dev/null
@@ -1,139 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-extern crate core;
-
-use alloc::vec::Vec;
-use core::{
-    sync::atomic::{AtomicUsize, Ordering},
-};
-use user_lib::{exit, sleep, thread_create, waittid};
-
-const N: usize = 2;
-const THREAD_NUM: usize = 10;
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-enum FlagState {
-    Out,
-    Want,
-    In,
-}
-
-static mut TURN: usize = 0;
-static mut FLAG: [FlagState; THREAD_NUM] = [FlagState::Out; THREAD_NUM];
-
-static GUARD: AtomicUsize = AtomicUsize::new(0);
-
-fn critical_test_enter() {
-    assert_eq!(GUARD.fetch_add(1, Ordering::SeqCst), 0);
-}
-
-fn critical_test_claim() {
-    assert_eq!(GUARD.load(Ordering::SeqCst), 1);
-}
-
-fn critical_test_exit() {
-    assert_eq!(GUARD.fetch_sub(1, Ordering::SeqCst), 1);
-}
-
-unsafe fn eisenberg_enter_critical(id: usize) {
-    /* announce that we want to enter */
-    loop {
-        println!("Thread[{}] try enter", id);
-        vstore!(FLAG[id], FlagState::Want);
-        loop {
-            /* check if any with higher priority is `Want` or `In` */
-            let mut prior_thread: Option<usize> = None;
-            let turn = vload!(TURN);
-            let ring_id = if id < turn { id + THREAD_NUM } else { id };
-            // FLAG.iter() may lead to some errors, use for-loop instead
-            for i in turn..ring_id {
-                if vload!(FLAG[i % THREAD_NUM]) != FlagState::Out {
-                    prior_thread = Some(i % THREAD_NUM);
-                    break;
-                }
-            }
-            if prior_thread.is_none() {
-                break;
-            }
-            println!(
-                "Thread[{}]: prior thread {} exist, sleep and retry",
-                id,
-                prior_thread.unwrap()
-            );
-            sleep(1);
-        }
-        /* now tentatively claim the resource */
-        vstore!(FLAG[id], FlagState::In);
-        /* enforce the order of `claim` and `conflict check`*/
-        memory_fence!();
-        /* check if anthor thread is also `In`, which imply a conflict*/
-        let mut conflict = false;
-        for i in 0..THREAD_NUM {
-            if i != id && vload!(FLAG[i]) == FlagState::In {
-                conflict = true;
-            }
-        }
-        if !conflict {
-            break;
-        }
-        println!("Thread[{}]: CONFLECT!", id);
-        /* no need to sleep */
-    }
-    /* clain the trun */
-    vstore!(TURN, id);
-    println!("Thread[{}] enter", id);
-}
-
-unsafe fn eisenberg_exit_critical(id: usize) {
-    /* find next one who wants to enter and give the turn to it*/
-    let mut next = id;
-    let ring_id = id + THREAD_NUM;
-    for i in (id + 1)..ring_id {
-        let idx = i % THREAD_NUM;
-        if vload!(FLAG[idx]) == FlagState::Want {
-            next = idx;
-            break;
-        }
-    }
-    vstore!(TURN, next);
-    /* All done */
-    vstore!(FLAG[id], FlagState::Out);
-    println!("Thread[{}] exit, give turn to {}", id, next);
-}
-
-pub unsafe fn thread_fn(id: usize) -> ! {
-    println!("Thread[{}] init.", id);
-    for _ in 0..N {
-        eisenberg_enter_critical(id);
-        critical_test_enter();
-        for _ in 0..3 {
-            critical_test_claim();
-            sleep(2);
-        }
-        critical_test_exit();
-        eisenberg_exit_critical(id);
-    }
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut v = Vec::new();
-    // TODO: really shuffle
-    assert_eq!(THREAD_NUM, 10);
-    let shuffle: [usize; 10] = [0, 7, 4, 6, 2, 9, 8, 1, 3, 5];
-    for i in 0..THREAD_NUM {
-        v.push(thread_create(thread_fn as usize, shuffle[i]));
-    }
-    for tid in v.iter() {
-        let exit_code = waittid(*tid as usize);
-        assert_eq!(exit_code, 0, "thread conflict happened!");
-        println!("thread#{} exited with code {}", tid, exit_code);
-    }
-    println!("main thread exited.");
-    0
-}
diff --git a/user/src/bin/exit.rs b/user/src/bin/exit.rs
index 60510c9..8e19542 100644
--- a/user/src/bin/exit.rs
+++ b/user/src/bin/exit.rs
@@ -7,7 +7,7 @@ use user_lib::{exit, fork, wait, waitpid, yield_};
 
 const MAGIC: i32 = -0x10384;
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!("I am the parent. Forking the child...");
     let pid = fork();
diff --git a/user/src/bin/fantastic_text.rs b/user/src/bin/fantastic_text.rs
index a3402ff..0850162 100644
--- a/user/src/bin/fantastic_text.rs
+++ b/user/src/bin/fantastic_text.rs
@@ -5,12 +5,12 @@
 extern crate user_lib;
 
 macro_rules! color_text {
-    ($text:expr, $color:expr) => {{
+    ($text:expr, $color:expr) => {
         format_args!("\x1b[{}m{}\x1b[0m", $color, $text)
-    }};
+    };
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!(
         "{}{}{}{}{} {}{}{}{} {}{}{}{}{}{}",
diff --git a/user/src/bin/filetest_simple.rs b/user/src/bin/filetest_simple.rs
index 3406d55..b192156 100644
--- a/user/src/bin/filetest_simple.rs
+++ b/user/src/bin/filetest_simple.rs
@@ -4,9 +4,9 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{close, open, read, write, OpenFlags};
+use user_lib::{OpenFlags, close, open, read, write};
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     let test_str = "Hello, world!";
     let filea = "filea\0";
diff --git a/user/src/bin/forktest.rs b/user/src/bin/forktest.rs
index 5374a56..f6003c5 100644
--- a/user/src/bin/forktest.rs
+++ b/user/src/bin/forktest.rs
@@ -8,7 +8,7 @@ use user_lib::{exit, fork, wait};
 
 const MAX_CHILD: usize = 30;
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     for i in 0..MAX_CHILD {
         let pid = fork();
diff --git a/user/src/bin/forktest2.rs b/user/src/bin/forktest2.rs
index c91ce15..ee452cc 100644
--- a/user/src/bin/forktest2.rs
+++ b/user/src/bin/forktest2.rs
@@ -8,7 +8,7 @@ use user_lib::{exit, fork, get_time, getpid, sleep, wait};
 
 static NUM: usize = 30;
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     for _ in 0..NUM {
         let pid = fork();
diff --git a/user/src/bin/forktest_simple.rs b/user/src/bin/forktest_simple.rs
index 29a624b..b9cf587 100644
--- a/user/src/bin/forktest_simple.rs
+++ b/user/src/bin/forktest_simple.rs
@@ -6,7 +6,7 @@ extern crate user_lib;
 
 use user_lib::{fork, getpid, wait};
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     assert_eq!(wait(&mut 0i32), -1);
     println!("sys_wait without child process test passed!");
diff --git a/user/src/bin/forktree.rs b/user/src/bin/forktree.rs
index 6b120ee..bcca4e6 100644
--- a/user/src/bin/forktree.rs
+++ b/user/src/bin/forktree.rs
@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{exit, fork, getpid, sleep, wait, yield_};
+use user_lib::{exit, fork, getpid, sleep, yield_};
 
 const DEPTH: usize = 4;
 
@@ -27,19 +27,11 @@ fn fork_tree(cur: &str) {
     println!("pid{}: {}", getpid(), cur);
     fork_child(cur, '0');
     fork_child(cur, '1');
-    let mut exit_code: i32 = 0;
-    for _ in 0..2 {
-        wait(&mut exit_code);
-    }
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     fork_tree("");
-    let mut exit_code: i32 = 0;
-    for _ in 0..2 {
-        wait(&mut exit_code);
-    }
     sleep(3000);
     0
 }
diff --git a/user/src/bin/gui_move.rs b/user/src/bin/gui_move.rs
deleted file mode 100644
index 240ff8f..0000000
--- a/user/src/bin/gui_move.rs
+++ /dev/null
@@ -1,82 +0,0 @@
-#![no_std]
-#![no_main]
-
-extern crate user_lib;
-extern crate alloc;
-
-use user_lib::console::getchar;
-use user_lib::{Display, VIRTGPU_XRES, VIRTGPU_YRES};
-
-use embedded_graphics::pixelcolor::Rgb888;
-use embedded_graphics::prelude::{Drawable, Point, RgbColor, Size};
-use embedded_graphics::primitives::Primitive;
-use embedded_graphics::primitives::{PrimitiveStyle, Rectangle};
-use embedded_graphics::draw_target::DrawTarget;
-
-const INIT_X: i32 = 640;
-const INIT_Y: i32 = 400;
-const RECT_SIZE: u32 = 40;
-
-pub struct DrawingBoard {
-    disp: Display,
-    latest_pos: Point,
-}
-
-impl DrawingBoard {
-    pub fn new() -> Self {
-        Self {
-            disp: Display::new(Size::new(VIRTGPU_XRES, VIRTGPU_YRES)),
-            latest_pos: Point::new(INIT_X, INIT_Y),
-        }
-    }
-    fn paint(&mut self) {
-        Rectangle::with_center(self.latest_pos, Size::new(RECT_SIZE, RECT_SIZE))
-            .into_styled(PrimitiveStyle::with_stroke(Rgb888::WHITE, 1))
-            .draw(&mut self.disp)
-            .ok();
-    }
-    fn unpaint(&mut self) {
-        Rectangle::with_center(self.latest_pos, Size::new(RECT_SIZE, RECT_SIZE))
-            .into_styled(PrimitiveStyle::with_stroke(Rgb888::BLACK, 1))
-            .draw(&mut self.disp)
-            .ok();
-    }
-    pub fn move_rect(&mut self, dx: i32, dy: i32) {
-        let new_x = self.latest_pos.x + dx;
-        let new_y = self.latest_pos.y + dy;
-        let r = (RECT_SIZE / 2) as i32;
-        if new_x > r && new_x + r < (VIRTGPU_XRES as i32) && new_y > r && new_y + r < (VIRTGPU_YRES as i32) {
-            self.unpaint();
-            self.latest_pos.x = new_x;
-            self.latest_pos.y = new_y;
-            self.paint();
-        }
-    }
-}
-
-const LF: u8 = 0x0au8;
-const CR: u8 = 0x0du8;
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut board = DrawingBoard::new();
-    let _ = board.disp.clear(Rgb888::BLACK).unwrap();
-    board.disp.flush();
-    loop {
-        let c = getchar();
-        if c == LF || c == CR {
-            break;
-        }
-        let mut moved = true;
-        match c {
-            b'w' => board.move_rect(0, -10),
-            b'a' => board.move_rect(-10, 0),
-            b's' => board.move_rect(0, 10),
-            b'd' => board.move_rect(10, 0),
-            _ => moved = false,
-        }
-        if moved {
-            board.disp.flush();
-        }
-    }
-    0
-}
diff --git a/user/src/bin/gui_shape.rs b/user/src/bin/gui_shape.rs
deleted file mode 100644
index df03df3..0000000
--- a/user/src/bin/gui_shape.rs
+++ /dev/null
@@ -1,59 +0,0 @@
-#![no_std]
-#![no_main]
-
-extern crate alloc;
-extern crate user_lib;
-
-use user_lib::{Display, VIRTGPU_XRES, VIRTGPU_YRES};
-
-use embedded_graphics::pixelcolor::Rgb888;
-use embedded_graphics::prelude::{DrawTarget, Drawable, Point, RgbColor, Size};
-use embedded_graphics::primitives::{Circle, Primitive, PrimitiveStyle, Rectangle, Triangle};
-
-const INIT_X: i32 = 80;
-const INIT_Y: i32 = 400;
-const RECT_SIZE: u32 = 150;
-
-pub struct DrawingBoard {
-    disp: Display,
-    latest_pos: Point,
-}
-
-impl DrawingBoard {
-    pub fn new() -> Self {
-        Self {
-            disp: Display::new(Size::new(VIRTGPU_XRES, VIRTGPU_YRES)),
-            latest_pos: Point::new(INIT_X, INIT_Y),
-        }
-    }
-    fn paint(&mut self) {
-        Rectangle::with_center(self.latest_pos, Size::new(RECT_SIZE, RECT_SIZE))
-            .into_styled(PrimitiveStyle::with_stroke(Rgb888::RED, 10))
-            .draw(&mut self.disp)
-            .ok();
-        Circle::new(self.latest_pos + Point::new(-70, -300), 150)
-            .into_styled(PrimitiveStyle::with_fill(Rgb888::BLUE))
-            .draw(&mut self.disp)
-            .ok();
-        Triangle::new(
-            self.latest_pos + Point::new(0, 150),
-            self.latest_pos + Point::new(80, 200),
-            self.latest_pos + Point::new(-120, 300),
-        )
-        .into_styled(PrimitiveStyle::with_stroke(Rgb888::GREEN, 10))
-        .draw(&mut self.disp)
-        .ok();
-    }
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut board = DrawingBoard::new();
-    let _ = board.disp.clear(Rgb888::BLACK).unwrap();
-    for _ in 0..5 {
-        board.latest_pos.x += RECT_SIZE as i32 + 20;
-        board.paint();
-    }
-    board.disp.flush();
-    0
-}
diff --git a/user/src/bin/gui_snake.rs b/user/src/bin/gui_snake.rs
deleted file mode 100644
index 6dd4052..0000000
--- a/user/src/bin/gui_snake.rs
+++ /dev/null
@@ -1,352 +0,0 @@
-#![no_std]
-#![no_main]
-
-extern crate alloc;
-extern crate user_lib;
-
-use user_lib::console::getchar;
-use user_lib::{key_pressed, sleep, Display, VIRTGPU_XRES, VIRTGPU_YRES};
-
-use embedded_graphics::pixelcolor::*;
-use embedded_graphics::prelude::{Drawable, Point, RgbColor, Size};
-use embedded_graphics::primitives::Primitive;
-use embedded_graphics::primitives::{PrimitiveStyle, Rectangle};
-use embedded_graphics::Pixel;
-use embedded_graphics::{draw_target::DrawTarget, prelude::OriginDimensions};
-use oorandom; //random generator
-
-struct Snake<T: PixelColor, const MAX_SIZE: usize> {
-    parts: [Pixel<T>; MAX_SIZE],
-    len: usize,
-    direction: Direction,
-    size_x: u32,
-    size_y: u32,
-}
-
-struct SnakeIntoIterator<'a, T: PixelColor, const MAX_SIZE: usize> {
-    snake: &'a Snake<T, MAX_SIZE>,
-    index: usize,
-}
-
-impl<'a, T: PixelColor, const MAX_SIZE: usize> IntoIterator for &'a Snake<T, MAX_SIZE> {
-    type Item = Pixel<T>;
-    type IntoIter = SnakeIntoIterator<'a, T, MAX_SIZE>;
-
-    fn into_iter(self) -> Self::IntoIter {
-        SnakeIntoIterator {
-            snake: self,
-            index: 0,
-        }
-    }
-}
-
-impl<'a, T: PixelColor, const MAX_SIZE: usize> Iterator for SnakeIntoIterator<'a, T, MAX_SIZE> {
-    type Item = Pixel<T>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        let cur = self.snake.parts[self.index];
-        if self.index < self.snake.len {
-            self.index += 1;
-            return Some(cur);
-        }
-        None
-    }
-}
-
-impl<T: PixelColor, const MAX_SIZE: usize> Snake<T, MAX_SIZE> {
-    fn new(color: T, size_x: u32, size_y: u32) -> Snake<T, MAX_SIZE> {
-        Snake {
-            parts: [Pixel::<T>(Point { x: 0, y: 0 }, color); MAX_SIZE],
-            len: 1,
-            direction: Direction::None,
-            size_x,
-            size_y,
-        }
-    }
-    fn set_direction(&mut self, direction: Direction) {
-        self.direction = direction;
-    }
-    fn contains(&self, this: Point) -> bool {
-        for part in self.into_iter() {
-            if part.0 == this {
-                return true;
-            };
-        }
-        false
-    }
-    fn grow(&mut self) {
-        if self.len < MAX_SIZE - 1 {
-            self.len += 1;
-        }
-    }
-    fn make_step(&mut self) {
-        let mut i = self.len;
-        while i > 0 {
-            self.parts[i] = self.parts[i - 1];
-            i -= 1;
-        }
-        match self.direction {
-            Direction::Left => {
-                if self.parts[0].0.x == 0 {
-                    self.parts[0].0.x = (self.size_x - 1) as i32;
-                } else {
-                    self.parts[0].0.x -= 1;
-                }
-            }
-            Direction::Right => {
-                if self.parts[0].0.x == (self.size_x - 1) as i32 {
-                    self.parts[0].0.x = 0;
-                } else {
-                    self.parts[0].0.x += 1;
-                }
-            }
-            Direction::Up => {
-                if self.parts[0].0.y == 0 {
-                    self.parts[0].0.y = (self.size_y - 1) as i32;
-                } else {
-                    self.parts[0].0.y -= 1;
-                }
-            }
-            Direction::Down => {
-                if self.parts[0].0.y == (self.size_y - 1) as i32 {
-                    self.parts[0].0.y = 0;
-                } else {
-                    self.parts[0].0.y += 1;
-                }
-            }
-            Direction::None => {}
-        }
-    }
-}
-
-struct Food<T: PixelColor> {
-    size_x: u32,
-    size_y: u32,
-    place: Pixel<T>,
-    rng: oorandom::Rand32,
-}
-
-impl<T: PixelColor> Food<T> {
-    pub fn new(color: T, size_x: u32, size_y: u32) -> Self {
-        let seed = 4;
-        let rng = oorandom::Rand32::new(seed);
-        Food {
-            size_x,
-            size_y,
-            place: Pixel(Point { x: 0, y: 0 }, color),
-            rng,
-        }
-    }
-    fn replace<'a, const MAX_SIZE: usize>(&mut self, iter_source: &Snake<T, MAX_SIZE>) {
-        let mut p: Point;
-        'outer: loop {
-            let random_number = self.rng.rand_u32();
-            let blocked_positions = iter_source.into_iter();
-            p = Point {
-                x: ((random_number >> 24) as u16 % self.size_x as u16).into(),
-                y: ((random_number >> 16) as u16 % self.size_y as u16).into(),
-            };
-            for blocked_position in blocked_positions {
-                if p == blocked_position.0 {
-                    continue 'outer;
-                }
-            }
-            break;
-        }
-        self.place = Pixel::<T> {
-            0: p,
-            1: self.place.1,
-        }
-    }
-    fn get_pixel(&self) -> Pixel<T> {
-        self.place
-    }
-}
-
-#[derive(PartialEq, Debug, Clone, Copy)]
-pub enum Direction {
-    Left,
-    Right,
-    Up,
-    Down,
-    None,
-}
-
-pub struct SnakeGame<const MAX_SNAKE_SIZE: usize, T: PixelColor> {
-    snake: Snake<T, MAX_SNAKE_SIZE>,
-    food: Food<T>,
-    food_age: u32,
-    food_lifetime: u32,
-    size_x: u32,
-    size_y: u32,
-    scale_x: u32,
-    scale_y: u32,
-}
-
-impl<const MAX_SIZE: usize, T: PixelColor> SnakeGame<MAX_SIZE, T> {
-    pub fn new(
-        size_x: u32,
-        size_y: u32,
-        scale_x: u32,
-        scale_y: u32,
-        snake_color: T,
-        food_color: T,
-        food_lifetime: u32,
-    ) -> Self {
-        let snake = Snake::<T, MAX_SIZE>::new(snake_color, size_x / scale_x, size_y / scale_y);
-        let mut food = Food::<T>::new(food_color, size_x / scale_x, size_y / scale_y);
-        food.replace(&snake);
-        SnakeGame {
-            snake,
-            food,
-            food_age: 0,
-            food_lifetime,
-            size_x,
-            size_y,
-            scale_x,
-            scale_y,
-        }
-    }
-    pub fn set_direction(&mut self, direction: Direction) {
-        self.snake.set_direction(direction);
-    }
-    pub fn draw<D>(&mut self, target: &mut D) -> ()
-    where
-        D: DrawTarget<Color = T>,
-    {
-        self.snake.make_step();
-        let hit = self.snake.contains(self.food.get_pixel().0);
-        if hit {
-            self.snake.grow();
-        }
-        self.food_age += 1;
-        if self.food_age >= self.food_lifetime || hit {
-            self.food.replace(&self.snake);
-            self.food_age = 0;
-        }
-
-        let mut scaled_display = ScaledDisplay::<D> {
-            real_display: target,
-            size_x: self.size_x / self.scale_x,
-            size_y: self.size_y / self.scale_y,
-            scale_x: self.scale_x,
-            scale_y: self.scale_y,
-        };
-
-        for part in self.snake.into_iter() {
-            _ = part.draw(&mut scaled_display);
-        }
-        _ = self.food.get_pixel().draw(&mut scaled_display);
-    }
-}
-
-/// A dummy DrawTarget implementation that can magnify each pixel so the user code does not need to adapt for scaling things
-struct ScaledDisplay<'a, T: DrawTarget> {
-    real_display: &'a mut T,
-    size_x: u32,
-    size_y: u32,
-    scale_x: u32,
-    scale_y: u32,
-}
-
-impl<'a, T: DrawTarget> DrawTarget for ScaledDisplay<'a, T> {
-    type Color = T::Color;
-    type Error = T::Error;
-
-    fn draw_iter<I>(&mut self, pixels: I) -> Result<(), Self::Error>
-    where
-        I: IntoIterator<Item = Pixel<Self::Color>>,
-    {
-        for pixel in pixels {
-            let style = PrimitiveStyle::with_fill(pixel.1);
-            Rectangle::new(
-                Point::new(
-                    pixel.0.x * self.scale_x as i32,
-                    pixel.0.y * self.scale_y as i32,
-                ),
-                Size::new(self.scale_x as u32, self.scale_y as u32),
-            )
-            .into_styled(style)
-            .draw(self.real_display)?;
-        }
-        Ok(())
-    }
-}
-
-impl<'a, T: DrawTarget> OriginDimensions for ScaledDisplay<'a, T> {
-    fn size(&self) -> Size {
-        Size::new(self.size_x as u32, self.size_y as u32)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-
-    use crate::Snake;
-    use embedded_graphics::pixelcolor::*;
-    use embedded_graphics::prelude::*;
-
-    #[test]
-    fn snake_basic() {
-        let mut snake = Snake::<Rgb888, 20>::new(Rgb888::RED, 8, 8);
-        snake.set_direction(crate::Direction::Right);
-        assert_eq!(
-            Pixel::<Rgb888>(Point { x: 0, y: 0 }, Rgb888::RED),
-            snake.into_iter().next().unwrap()
-        );
-        snake.make_step();
-        assert_eq!(
-            Pixel::<Rgb888>(Point { x: 1, y: 0 }, Rgb888::RED),
-            snake.into_iter().nth(0).unwrap()
-        );
-        assert_eq!(
-            Pixel::<Rgb888>(Point { x: 0, y: 0 }, Rgb888::RED),
-            snake.into_iter().nth(1).unwrap()
-        );
-        snake.set_direction(crate::Direction::Down);
-        snake.make_step();
-        assert_eq!(
-            Pixel::<Rgb888>(Point { x: 1, y: 1 }, Rgb888::RED),
-            snake.into_iter().nth(0).unwrap()
-        );
-        assert_eq!(
-            Pixel::<Rgb888>(Point { x: 1, y: 0 }, Rgb888::RED),
-            snake.into_iter().nth(1).unwrap()
-        );
-        assert_eq!(
-            Pixel::<Rgb888>(Point { x: 0, y: 0 }, Rgb888::RED),
-            snake.into_iter().nth(2).unwrap()
-        );
-        assert_eq!(true, snake.contains(Point { x: 0, y: 0 }));
-        assert_eq!(true, snake.contains(Point { x: 1, y: 0 }));
-        assert_eq!(true, snake.contains(Point { x: 1, y: 1 }));
-    }
-}
-
-const LF: u8 = 0x0au8;
-const CR: u8 = 0x0du8;
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut disp = Display::new(Size::new(VIRTGPU_XRES, VIRTGPU_YRES));
-    let mut game = SnakeGame::<20, Rgb888>::new(1280, 800, 20, 20, Rgb888::RED, Rgb888::YELLOW, 200);
-    let _ = disp.clear(Rgb888::BLACK).unwrap();
-    loop {
-        if key_pressed() {
-            let c = getchar();
-            match c {
-                LF => break,
-                CR => break,
-                b'w' => game.set_direction(Direction::Up),
-                b's' => game.set_direction(Direction::Down),
-                b'a' => game.set_direction(Direction::Left),
-                b'd' => game.set_direction(Direction::Right),
-                _ => (),
-            }
-        }
-        let _ = disp.clear(Rgb888::BLACK).unwrap();
-        game.draw(&mut disp);
-        disp.flush();
-        sleep(40);
-    }
-    0
-}
diff --git a/user/src/bin/gui_tri.rs b/user/src/bin/gui_tri.rs
deleted file mode 100644
index 69d47f5..0000000
--- a/user/src/bin/gui_tri.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-#![no_std]
-#![no_main]
-
-extern crate user_lib;
-
-use embedded_graphics::prelude::Size;
-use user_lib::{Display, VIRTGPU_XRES, VIRTGPU_YRES};
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut disp = Display::new(Size::new(VIRTGPU_XRES, VIRTGPU_YRES));
-    disp.paint_on_framebuffer(|fb| {
-        for y in 0..VIRTGPU_YRES as usize {
-            for x in 0..VIRTGPU_XRES as usize {
-                let idx = (y * VIRTGPU_XRES as usize + x) * 4;
-                fb[idx] = x as u8;
-                fb[idx + 1] = y as u8;
-                fb[idx + 2] = (x + y) as u8;
-            }
-        }
-    });
-    disp.flush();
-    0
-}
diff --git a/user/src/bin/hello_world.rs b/user/src/bin/hello_world.rs
index 10d3f26..cc651e7 100644
--- a/user/src/bin/hello_world.rs
+++ b/user/src/bin/hello_world.rs
@@ -4,7 +4,7 @@
 #[macro_use]
 extern crate user_lib;
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!("Hello world from user mode program!");
     0
diff --git a/user/src/bin/huge_write.rs b/user/src/bin/huge_write.rs
index 2a977c9..9327261 100644
--- a/user/src/bin/huge_write.rs
+++ b/user/src/bin/huge_write.rs
@@ -4,9 +4,9 @@
 #[macro_use]
 extern crate user_lib;
 
-use user_lib::{close, get_time, open, write, OpenFlags};
+use user_lib::{OpenFlags, close, get_time, open, write};
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     let mut buffer = [0u8; 1024]; // 1KiB
     for (i, ch) in buffer.iter_mut().enumerate() {
@@ -24,7 +24,7 @@ pub fn main() -> i32 {
     }
     close(f);
     let time_ms = (get_time() - start) as usize;
-    let speed_kbs = (size_mb << 20) / time_ms;
+    let speed_kbs = size_mb * 1000000 / time_ms;
     println!(
         "{}MiB written, time cost = {}ms, write speed = {}KiB/s",
         size_mb, time_ms, speed_kbs
diff --git a/user/src/bin/huge_write_mt.rs b/user/src/bin/huge_write_mt.rs
deleted file mode 100644
index 0a60fd8..0000000
--- a/user/src/bin/huge_write_mt.rs
+++ /dev/null
@@ -1,56 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::{fmt::format, vec::Vec};
-use user_lib::{close, get_time, gettid, open, write, OpenFlags};
-use user_lib::{exit, thread_create, waittid};
-
-fn worker(size_kib: usize) {
-    let mut buffer = [0u8; 1024]; // 1KiB
-    for (i, ch) in buffer.iter_mut().enumerate() {
-        *ch = i as u8;
-    }
-    let filename = format(format_args!("testf{}\0", gettid()));
-    let f = open(filename.as_str(), OpenFlags::CREATE | OpenFlags::WRONLY);
-    if f < 0 {
-        panic!("Open test file failed!");
-    }
-    let f = f as usize;
-    for _ in 0..size_kib {
-        write(f, &buffer);
-    }
-    close(f);
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    assert_eq!(argc, 2, "wrong argument");
-    let size_mb = 1usize;
-    let size_kb = size_mb << 10;
-    let workers = argv[1].parse::<usize>().expect("wrong argument");
-    assert!(workers >= 1 && size_kb % workers == 0, "wrong argument");
-
-    let start = get_time();
-
-    let mut v = Vec::new();
-    let size_mb = 1usize;
-    for _ in 0..workers {
-        v.push(thread_create(worker as usize, size_kb / workers));
-    }
-    for tid in v.iter() {
-        assert_eq!(0, waittid(*tid as usize));
-    }
-
-    let time_ms = (get_time() - start) as usize;
-    let speed_kbs = size_kb * 1000 / time_ms;
-    println!(
-        "{}MiB written by {} threads, time cost = {}ms, write speed = {}KiB/s",
-        size_mb, workers, time_ms, speed_kbs
-    );
-    0
-}
diff --git a/user/src/bin/infloop.rs b/user/src/bin/infloop.rs
deleted file mode 100644
index 1f24853..0000000
--- a/user/src/bin/infloop.rs
+++ /dev/null
@@ -1,10 +0,0 @@
-#![no_std]
-#![no_main]
-#![allow(clippy::empty_loop)]
-
-extern crate user_lib;
-
-#[no_mangle]
-pub fn main(_argc: usize, _argv: &[&str]) -> ! {
-    loop {}
-}
diff --git a/user/src/bin/initproc.rs b/user/src/bin/initproc.rs
index d25aee1..d522b77 100644
--- a/user/src/bin/initproc.rs
+++ b/user/src/bin/initproc.rs
@@ -1,14 +1,15 @@
 #![no_std]
 #![no_main]
 
+#[macro_use]
 extern crate user_lib;
 
 use user_lib::{exec, fork, wait, yield_};
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 fn main() -> i32 {
     if fork() == 0 {
-        exec("user_shell\0", &[core::ptr::null::<u8>()]);
+        exec("user_shell\0");
     } else {
         loop {
             let mut exit_code: i32 = 0;
@@ -17,13 +18,10 @@ fn main() -> i32 {
                 yield_();
                 continue;
             }
-            /*
             println!(
                 "[initproc] Released a zombie process, pid={}, exit_code={}",
-                pid,
-                exit_code,
+                pid, exit_code,
             );
-            */
         }
     }
     0
diff --git a/user/src/bin/inputdev_event.rs b/user/src/bin/inputdev_event.rs
deleted file mode 100644
index ea56f3a..0000000
--- a/user/src/bin/inputdev_event.rs
+++ /dev/null
@@ -1,25 +0,0 @@
-#![no_std]
-#![no_main]
-
-use user_lib::{event_get, DecodeType, Key, KeyType};
-
-#[macro_use]
-extern crate user_lib;
-
-#[no_mangle]
-pub fn main() -> i32 {
-    println!("Input device event test");
-    loop {
-        if let Some(event) = event_get() {
-            if let Some(decoder_type) = event.decode() {
-                println!("{:?}", decoder_type);
-                if let DecodeType::Key(key, keytype) = decoder_type {
-                    if key == Key::Enter && keytype == KeyType::Press {
-                        break;
-                    }
-                }
-            }
-        }
-    }
-    0
-}
diff --git a/user/src/bin/matrix.rs b/user/src/bin/matrix.rs
index 9ebf48f..846f4c6 100644
--- a/user/src/bin/matrix.rs
+++ b/user/src/bin/matrix.rs
@@ -44,7 +44,7 @@ fn work(times: isize) {
     exit(0);
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     for _ in 0..NUM {
         let pid = fork();
diff --git a/user/src/bin/mpsc_sem.rs b/user/src/bin/mpsc_sem.rs
deleted file mode 100644
index 7b72bbb..0000000
--- a/user/src/bin/mpsc_sem.rs
+++ /dev/null
@@ -1,73 +0,0 @@
-#![no_std]
-#![no_main]
-#![allow(clippy::println_empty_string)]
-
-#[macro_use]
-extern crate user_lib;
-
-extern crate alloc;
-
-use alloc::vec::Vec;
-use user_lib::exit;
-use user_lib::{semaphore_create, semaphore_down, semaphore_up};
-use user_lib::{thread_create, waittid};
-
-const SEM_MUTEX: usize = 0;
-const SEM_EMPTY: usize = 1;
-const SEM_AVAIL: usize = 2;
-const BUFFER_SIZE: usize = 8;
-static mut BUFFER: [usize; BUFFER_SIZE] = [0; BUFFER_SIZE];
-static mut FRONT: usize = 0;
-static mut TAIL: usize = 0;
-const PRODUCER_COUNT: usize = 4;
-const NUMBER_PER_PRODUCER: usize = 100;
-
-unsafe fn producer(id: *const usize) -> ! {
-    let id = *id;
-    for _ in 0..NUMBER_PER_PRODUCER {
-        semaphore_down(SEM_EMPTY);
-        semaphore_down(SEM_MUTEX);
-        BUFFER[TAIL] = id;
-        TAIL = (TAIL + 1) % BUFFER_SIZE;
-        semaphore_up(SEM_MUTEX);
-        semaphore_up(SEM_AVAIL);
-    }
-    exit(0)
-}
-
-unsafe fn consumer() -> ! {
-    for _ in 0..PRODUCER_COUNT * NUMBER_PER_PRODUCER {
-        semaphore_down(SEM_AVAIL);
-        semaphore_down(SEM_MUTEX);
-        print!("{} ", BUFFER[FRONT]);
-        FRONT = (FRONT + 1) % BUFFER_SIZE;
-        semaphore_up(SEM_MUTEX);
-        semaphore_up(SEM_EMPTY);
-    }
-    println!("");
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    // create semaphores
-    assert_eq!(semaphore_create(1) as usize, SEM_MUTEX);
-    assert_eq!(semaphore_create(BUFFER_SIZE) as usize, SEM_EMPTY);
-    assert_eq!(semaphore_create(0) as usize, SEM_AVAIL);
-    // create threads
-    let ids: Vec<_> = (0..PRODUCER_COUNT).collect();
-    let mut threads = Vec::new();
-    for i in 0..PRODUCER_COUNT {
-        threads.push(thread_create(
-            producer as usize,
-            &ids.as_slice()[i] as *const _ as usize,
-        ));
-    }
-    threads.push(thread_create(consumer as usize, 0));
-    // wait for all threads to complete
-    for thread in threads.iter() {
-        waittid(*thread as usize);
-    }
-    println!("mpsc_sem passed!");
-    0
-}
diff --git a/user/src/bin/peterson.rs b/user/src/bin/peterson.rs
deleted file mode 100644
index e03e2a4..0000000
--- a/user/src/bin/peterson.rs
+++ /dev/null
@@ -1,79 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-extern crate core;
-
-use alloc::vec::Vec;
-use core::sync::atomic::{AtomicUsize, Ordering};
-use user_lib::{exit, sleep, thread_create, waittid};
-const N: usize = 1000;
-
-static mut TURN: usize = 0;
-static mut FLAG: [bool; 2] = [false; 2];
-static GUARD: AtomicUsize = AtomicUsize::new(0);
-
-fn critical_test_enter() {
-    assert_eq!(GUARD.fetch_add(1, Ordering::SeqCst), 0);
-}
-
-fn critical_test_claim() {
-    assert_eq!(GUARD.load(Ordering::SeqCst), 1);
-}
-
-fn critical_test_exit() {
-    assert_eq!(GUARD.fetch_sub(1, Ordering::SeqCst), 1);
-}
-
-unsafe fn peterson_enter_critical(id: usize, peer_id: usize) {
-    // println!("Thread[{}] try enter", id);
-    vstore!(FLAG[id], true);
-    vstore!(TURN, peer_id);
-    memory_fence!();
-    while vload!(FLAG[peer_id]) && vload!(TURN) == peer_id {
-        // println!("Thread[{}] enter fail", id);
-        sleep(1);
-        // println!("Thread[{}] retry enter", id);
-    }
-    // println!("Thread[{}] enter", id);
-}
-
-unsafe fn peterson_exit_critical(id: usize) {
-    vstore!(FLAG[id], false);
-    // println!("Thread[{}] exit", id);
-}
-
-pub unsafe fn thread_fn(id: usize) -> ! {
-    // println!("Thread[{}] init.", id);
-    let peer_id: usize = id ^ 1;
-    for iter in 0..N {
-        if iter % 10 == 0 {
-            println!("[{}] it={}", id, iter);
-        }
-        peterson_enter_critical(id, peer_id);
-        critical_test_enter();
-        for _ in 0..3 {
-            critical_test_claim();
-            sleep(2);
-        }
-        critical_test_exit();
-        peterson_exit_critical(id);
-    }
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut v = Vec::new();
-    v.push(thread_create(thread_fn as usize, 0));
-    // v.push(thread_create(thread_fn as usize, 1));
-    for tid in v.iter() {
-        let exit_code = waittid(*tid as usize);
-        assert_eq!(exit_code, 0, "thread conflict happened!");
-        println!("thread#{} exited with code {}", tid, exit_code);
-    }
-    println!("main thread exited.");
-    0
-}
diff --git a/user/src/bin/phil_din_mutex.rs b/user/src/bin/phil_din_mutex.rs
deleted file mode 100644
index 8e7b566..0000000
--- a/user/src/bin/phil_din_mutex.rs
+++ /dev/null
@@ -1,107 +0,0 @@
-#![no_std]
-#![no_main]
-#![allow(clippy::println_empty_string)]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use user_lib::{exit, get_time, sleep};
-use user_lib::{mutex_blocking_create, mutex_lock, mutex_unlock};
-use user_lib::{thread_create, waittid};
-
-const N: usize = 5;
-const ROUND: usize = 4;
-// A round: think -> wait for forks -> eat
-const GRAPH_SCALE: usize = 100;
-
-fn get_time_u() -> usize {
-    get_time() as usize
-}
-
-// Time unit: ms
-const ARR: [[usize; ROUND * 2]; N] = [
-    [700, 800, 1000, 400, 500, 600, 200, 400],
-    [300, 600, 200, 700, 1000, 100, 300, 600],
-    [500, 200, 900, 200, 400, 600, 1200, 400],
-    [500, 1000, 600, 500, 800, 600, 200, 900],
-    [600, 100, 600, 600, 200, 500, 600, 200],
-];
-static mut THINK: [[usize; ROUND * 2]; N] = [[0; ROUND * 2]; N];
-static mut EAT: [[usize; ROUND * 2]; N] = [[0; ROUND * 2]; N];
-
-fn philosopher_dining_problem(id: *const usize) {
-    let id = unsafe { *id };
-    let left = id;
-    let right = if id == N - 1 { 0 } else { id + 1 };
-    let min = if left < right { left } else { right };
-    let max = left + right - min;
-    for round in 0..ROUND {
-        // thinking
-        unsafe {
-            THINK[id][2 * round] = get_time_u();
-        }
-        sleep(ARR[id][2 * round]);
-        unsafe {
-            THINK[id][2 * round + 1] = get_time_u();
-        }
-        // wait for forks
-        mutex_lock(min);
-        mutex_lock(max);
-        // eating
-        unsafe {
-            EAT[id][2 * round] = get_time_u();
-        }
-        sleep(ARR[id][2 * round + 1]);
-        unsafe {
-            EAT[id][2 * round + 1] = get_time_u();
-        }
-        mutex_unlock(max);
-        mutex_unlock(min);
-    }
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut v = Vec::new();
-    let ids: Vec<_> = (0..N).collect();
-    let start = get_time_u();
-    for i in 0..N {
-        assert_eq!(mutex_blocking_create(), i as isize);
-        v.push(thread_create(
-            philosopher_dining_problem as usize,
-            &ids.as_slice()[i] as *const _ as usize,
-        ));
-    }
-    for tid in v.iter() {
-        waittid(*tid as usize);
-    }
-    let time_cost = get_time_u() - start;
-    println!("time cost = {}", time_cost);
-    println!("'-' -> THINKING; 'x' -> EATING; ' ' -> WAITING ");
-    for id in (0..N).into_iter().chain(0..=0) {
-        print!("#{}:", id);
-        for j in 0..time_cost / GRAPH_SCALE {
-            let current_time = j * GRAPH_SCALE + start;
-            if (0..ROUND).any(|round| unsafe {
-                let start_thinking = THINK[id][2 * round];
-                let end_thinking = THINK[id][2 * round + 1];
-                start_thinking <= current_time && current_time <= end_thinking
-            }) {
-                print!("-");
-            } else if (0..ROUND).any(|round| unsafe {
-                let start_eating = EAT[id][2 * round];
-                let end_eating = EAT[id][2 * round + 1];
-                start_eating <= current_time && current_time <= end_eating
-            }) {
-                print!("x");
-            } else {
-                print!(" ");
-            };
-        }
-        println!("");
-    }
-    0
-}
diff --git a/user/src/bin/pipe_large_test.rs b/user/src/bin/pipe_large_test.rs
deleted file mode 100644
index e85d0a6..0000000
--- a/user/src/bin/pipe_large_test.rs
+++ /dev/null
@@ -1,71 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-extern crate alloc;
-
-use alloc::format;
-use user_lib::{close, fork, get_time, pipe, read, wait, write};
-
-const LENGTH: usize = 3000;
-#[no_mangle]
-pub fn main() -> i32 {
-    // create pipes
-    // parent write to child
-    let mut down_pipe_fd = [0usize; 2];
-    // child write to parent
-    let mut up_pipe_fd = [0usize; 2];
-    pipe(&mut down_pipe_fd);
-    pipe(&mut up_pipe_fd);
-    let mut random_str = [0u8; LENGTH];
-    if fork() == 0 {
-        // close write end of down pipe
-        close(down_pipe_fd[1]);
-        // close read end of up pipe
-        close(up_pipe_fd[0]);
-        assert_eq!(read(down_pipe_fd[0], &mut random_str) as usize, LENGTH);
-        close(down_pipe_fd[0]);
-        let sum: usize = random_str.iter().map(|v| *v as usize).sum::<usize>();
-        println!("sum = {}(child)", sum);
-        let sum_str = format!("{}", sum);
-        write(up_pipe_fd[1], sum_str.as_bytes());
-        close(up_pipe_fd[1]);
-        println!("Child process exited!");
-        0
-    } else {
-        // close read end of down pipe
-        close(down_pipe_fd[0]);
-        // close write end of up pipe
-        close(up_pipe_fd[1]);
-        // generate a long random string
-        for ch in random_str.iter_mut() {
-            *ch = get_time() as u8;
-        }
-        // send it
-        assert_eq!(
-            write(down_pipe_fd[1], &random_str) as usize,
-            random_str.len()
-        );
-        // close write end of down pipe
-        close(down_pipe_fd[1]);
-        // calculate sum(parent)
-        let sum: usize = random_str.iter().map(|v| *v as usize).sum::<usize>();
-        println!("sum = {}(parent)", sum);
-        // recv sum(child)
-        let mut child_result = [0u8; 32];
-        let result_len = read(up_pipe_fd[0], &mut child_result) as usize;
-        close(up_pipe_fd[0]);
-        // check
-        assert_eq!(
-            sum,
-            str::parse::<usize>(core::str::from_utf8(&child_result[..result_len]).unwrap())
-                .unwrap()
-        );
-        let mut _unused: i32 = 0;
-        wait(&mut _unused);
-        println!("pipe_large_test passed!");
-        0
-    }
-}
diff --git a/user/src/bin/pipetest.rs b/user/src/bin/pipetest.rs
deleted file mode 100644
index 5436c63..0000000
--- a/user/src/bin/pipetest.rs
+++ /dev/null
@@ -1,44 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use user_lib::{close, fork, pipe, read, wait, write};
-
-static STR: &str = "Hello, world!";
-
-#[no_mangle]
-pub fn main() -> i32 {
-    // create pipe
-    let mut pipe_fd = [0usize; 2];
-    pipe(&mut pipe_fd);
-    // read end
-    assert_eq!(pipe_fd[0], 3);
-    // write end
-    assert_eq!(pipe_fd[1], 4);
-    if fork() == 0 {
-        // child process, read from parent
-        // close write_end
-        close(pipe_fd[1]);
-        let mut buffer = [0u8; 32];
-        let len_read = read(pipe_fd[0], &mut buffer) as usize;
-        // close read_end
-        close(pipe_fd[0]);
-        assert_eq!(core::str::from_utf8(&buffer[..len_read]).unwrap(), STR);
-        println!("Read OK, child process exited!");
-        0
-    } else {
-        // parent process, write to child
-        // close read end
-        close(pipe_fd[0]);
-        assert_eq!(write(pipe_fd[1], STR.as_bytes()), STR.len() as isize);
-        // close write end
-        close(pipe_fd[1]);
-        let mut child_exit_code: i32 = 0;
-        wait(&mut child_exit_code);
-        assert_eq!(child_exit_code, 0);
-        println!("pipetest passed!");
-        0
-    }
-}
diff --git a/user/src/bin/priv_csr.rs b/user/src/bin/priv_csr.rs
deleted file mode 100644
index fbd678f..0000000
--- a/user/src/bin/priv_csr.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use riscv::register::sstatus::{self, SPP};
-
-#[no_mangle]
-fn main() -> i32 {
-    println!("Try to access privileged CSR in U Mode");
-    println!("Kernel should kill this application!");
-    unsafe {
-        sstatus::set_spp(SPP::User);
-    }
-    0
-}
diff --git a/user/src/bin/priv_inst.rs b/user/src/bin/priv_inst.rs
deleted file mode 100644
index 04dac37..0000000
--- a/user/src/bin/priv_inst.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use core::arch::asm;
-
-#[no_mangle]
-fn main() -> i32 {
-    println!("Try to execute privileged instruction in U Mode");
-    println!("Kernel should kill this application!");
-    unsafe {
-        asm!("sret");
-    }
-    0
-}
diff --git a/user/src/bin/race_adder_arg.rs b/user/src/bin/race_adder_arg.rs
deleted file mode 100644
index f33c660..0000000
--- a/user/src/bin/race_adder_arg.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use crate::alloc::string::ToString;
-use alloc::vec::Vec;
-use core::ptr::addr_of_mut;
-use user_lib::{exit, get_time, thread_create, waittid};
-
-static mut A: usize = 0;
-const PER_THREAD: usize = 1000;
-const THREAD_COUNT: usize = 16;
-
-unsafe fn f(count: usize) -> ! {
-    let mut t = 2usize;
-    for _ in 0..PER_THREAD {
-        let a = addr_of_mut!(A);
-        let cur = a.read_volatile();
-        for _ in 0..count {
-            t = t * t % 10007;
-        }
-        a.write_volatile(cur + 1);
-    }
-    exit(t as i32)
-}
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    let count: usize;
-    if argc == 1 {
-        count = THREAD_COUNT;
-    } else if argc == 2 {
-        count = argv[1].to_string().parse::<usize>().unwrap();
-    } else {
-        println!(
-            "ERROR in argv, argc is {}, argv[0] {} , argv[1] {} , argv[2] {}",
-            argc, argv[0], argv[1], argv[2]
-        );
-        exit(-1);
-    }
-
-    let start = get_time();
-    let mut v = Vec::new();
-    for _ in 0..THREAD_COUNT {
-        v.push(thread_create(f as usize, count) as usize);
-    }
-    let mut time_cost = Vec::new();
-    for tid in v.iter() {
-        time_cost.push(waittid(*tid));
-    }
-    println!("time cost is {}ms", get_time() - start);
-    assert_eq!(unsafe { A }, PER_THREAD * THREAD_COUNT);
-    0
-}
diff --git a/user/src/bin/random_num.rs b/user/src/bin/random_num.rs
deleted file mode 100644
index d68bb13..0000000
--- a/user/src/bin/random_num.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-use oorandom;
-
-#[no_mangle]
-pub fn main() -> i32 {
-    println!("random num  program!");
-    let seed = 4;
-    let mut rng = oorandom::Rand32::new(seed);
-    println!("OORandom: Random number 32bit: {}", rng.rand_i32());
-    println!("OORandom: Random number range: {}", rng.rand_range(1..100));
-    0
-}
diff --git a/user/src/bin/run_pipe_test.rs b/user/src/bin/run_pipe_test.rs
deleted file mode 100644
index d3e329d..0000000
--- a/user/src/bin/run_pipe_test.rs
+++ /dev/null
@@ -1,21 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use user_lib::{exec, fork, wait};
-
-#[no_mangle]
-pub fn main() -> i32 {
-    for i in 0..5 {
-        if fork() == 0 {
-            exec("pipe_large_test\0", &[core::ptr::null::<u8>()]);
-        } else {
-            let mut _unused: i32 = 0;
-            wait(&mut _unused);
-            println!("Iter {} OK.", i);
-        }
-    }
-    0
-}
diff --git a/user/src/bin/sleep.rs b/user/src/bin/sleep.rs
index 641a4f9..e02b3ed 100644
--- a/user/src/bin/sleep.rs
+++ b/user/src/bin/sleep.rs
@@ -15,7 +15,7 @@ fn sleepy() {
     exit(0);
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     let current_time = get_time();
     let pid = fork();
diff --git a/user/src/bin/sleep_simple.rs b/user/src/bin/sleep_simple.rs
index 7015a3d..9f6e2e4 100644
--- a/user/src/bin/sleep_simple.rs
+++ b/user/src/bin/sleep_simple.rs
@@ -6,7 +6,7 @@ extern crate user_lib;
 
 use user_lib::{get_time, sleep};
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!("into sleep test!");
     let start = get_time();
diff --git a/user/src/bin/stack_overflow.rs b/user/src/bin/stack_overflow.rs
index 3bec557..731982a 100644
--- a/user/src/bin/stack_overflow.rs
+++ b/user/src/bin/stack_overflow.rs
@@ -12,7 +12,7 @@ fn f(depth: usize) {
     f(depth + 1);
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!("It should trigger segmentation fault!");
     f(0);
diff --git a/user/src/bin/stackful_coroutine.rs b/user/src/bin/stackful_coroutine.rs
deleted file mode 100644
index 3f61979..0000000
--- a/user/src/bin/stackful_coroutine.rs
+++ /dev/null
@@ -1,350 +0,0 @@
-// we porting below codes to Rcore Tutorial v3
-// https://cfsamson.gitbook.io/green-threads-explained-in-200-lines-of-rust/
-// https://github.com/cfsamson/example-greenthreads
-#![no_std]
-#![no_main]
-#![feature(naked_functions)]
-//#![feature(asm)]
-
-extern crate alloc;
-#[macro_use]
-extern crate user_lib;
-
-use core::arch::asm;
-
-//#[macro_use]
-use alloc::vec;
-use alloc::vec::Vec;
-
-use user_lib::exit;
-
-// In our simple example we set most constraints here.
-const DEFAULT_STACK_SIZE: usize = 4096; //128 got  SEGFAULT, 256(1024, 4096) got right results.
-const MAX_TASKS: usize = 5;
-static mut RUNTIME: usize = 0;
-
-pub struct Runtime {
-    tasks: Vec<Task>,
-    current: usize,
-}
-
-#[derive(PartialEq, Eq, Debug)]
-enum State {
-    Available,
-    Running,
-    Ready,
-}
-
-struct Task {
-    id: usize,
-    stack: Vec<u8>,
-    ctx: TaskContext,
-    state: State,
-}
-
-#[derive(Debug, Default)]
-#[repr(C)] // not strictly needed but Rust ABI is not guaranteed to be stable
-pub struct TaskContext {
-    // 15 u64
-    x1: u64,  //ra: return addres
-    x2: u64,  //sp
-    x8: u64,  //s0,fp
-    x9: u64,  //s1
-    x18: u64, //x18-27: s2-11
-    x19: u64,
-    x20: u64,
-    x21: u64,
-    x22: u64,
-    x23: u64,
-    x24: u64,
-    x25: u64,
-    x26: u64,
-    x27: u64,
-    nx1: u64, //new return addres
-}
-
-impl Task {
-    fn new(id: usize) -> Self {
-        // We initialize each task here and allocate the stack. This is not neccesary,
-        // we can allocate memory for it later, but it keeps complexity down and lets us focus on more interesting parts
-        // to do it here. The important part is that once allocated it MUST NOT move in memory.
-        Task {
-            id: id,
-            stack: vec![0_u8; DEFAULT_STACK_SIZE],
-            ctx: TaskContext::default(),
-            state: State::Available,
-        }
-    }
-}
-
-impl Runtime {
-    pub fn new() -> Self {
-        // This will be our base task, which will be initialized in the `running` state
-        let base_task = Task {
-            id: 0,
-            stack: vec![0_u8; DEFAULT_STACK_SIZE],
-            ctx: TaskContext::default(),
-            state: State::Running,
-        };
-
-        // We initialize the rest of our tasks.
-        let mut tasks = vec![base_task];
-        let mut available_tasks: Vec<Task> = (1..MAX_TASKS).map(|i| Task::new(i)).collect();
-        tasks.append(&mut available_tasks);
-
-        Runtime { tasks, current: 0 }
-    }
-
-    /// This is cheating a bit, but we need a pointer to our Runtime stored so we can call yield on it even if
-    /// we don't have a reference to it.
-    pub fn init(&self) {
-        unsafe {
-            let r_ptr: *const Runtime = self;
-            RUNTIME = r_ptr as usize;
-        }
-    }
-
-    /// This is where we start running our runtime. If it is our base task, we call yield until
-    /// it returns false (which means that there are no tasks scheduled) and we are done.
-    pub fn run(&mut self) {
-        while self.t_yield() {}
-        println!("All tasks finished!");
-    }
-
-    /// This is our return function. The only place we use this is in our `guard` function.
-    /// If the current task is not our base task we set its state to Available. It means
-    /// we're finished with it. Then we yield which will schedule a new task to be run.
-    fn t_return(&mut self) {
-        if self.current != 0 {
-            self.tasks[self.current].state = State::Available;
-            self.t_yield();
-        }
-    }
-
-    /// This is the heart of our runtime. Here we go through all tasks and see if anyone is in the `Ready` state.
-    /// If no task is `Ready` we're all done. This is an extremely simple scheduler using only a round-robin algorithm.
-    ///
-    /// If we find a task that's ready to be run we change the state of the current task from `Running` to `Ready`.
-    /// Then we call switch which will save the current context (the old context) and load the new context
-    /// into the CPU which then resumes based on the context it was just passed.
-    ///
-    /// NOITCE: if we comment below `#[inline(never)]`, we can not get the corrent running result
-    #[inline(never)]
-    fn t_yield(&mut self) -> bool {
-        let mut pos = self.current;
-        while self.tasks[pos].state != State::Ready {
-            pos += 1;
-            if pos == self.tasks.len() {
-                pos = 0;
-            }
-            if pos == self.current {
-                return false;
-            }
-        }
-
-        if self.tasks[self.current].state != State::Available {
-            self.tasks[self.current].state = State::Ready;
-        }
-
-        self.tasks[pos].state = State::Running;
-        let old_pos = self.current;
-        self.current = pos;
-
-        unsafe {
-            switch(&mut self.tasks[old_pos].ctx, &self.tasks[pos].ctx);
-        }
-
-        // NOTE: this might look strange and it is. Normally we would just mark this as `unreachable!()` but our compiler
-        // is too smart for it's own good so it optimized our code away on release builds. Curiously this happens on windows
-        // and not on linux. This is a common problem in tests so Rust has a `black_box` function in the `test` crate that
-        // will "pretend" to use a value we give it to prevent the compiler from eliminating code. I'll just do this instead,
-        // this code will never be run anyways and if it did it would always be `true`.
-        self.tasks.len() > 0
-    }
-
-    /// While `yield` is the logically interesting function I think this the technically most interesting.
-    ///
-    /// When we spawn a new task we first check if there are any available tasks (tasks in `Parked` state).
-    /// If we run out of tasks we panic in this scenario but there are several (better) ways to handle that.
-    /// We keep things simple for now.
-    ///
-    /// When we find an available task we get the stack length and a pointer to our u8 bytearray.
-    ///
-    /// The next part we have to use some unsafe functions. First we write an address to our `guard` function
-    /// that will be called if the function we provide returns. Then we set the address to the function we
-    /// pass inn.
-    ///
-    /// Third, we set the value of `sp` which is the stack pointer to the address of our provided function so we start
-    /// executing that first when we are scheuled to run.
-    ///
-    /// Lastly we set the state as `Ready` which means we have work to do and is ready to do it.
-    pub fn spawn(&mut self, f: fn()) {
-        let available = self
-            .tasks
-            .iter_mut()
-            .find(|t| t.state == State::Available)
-            .expect("no available task.");
-
-        println!("RUNTIME: spawning task {}\n", available.id);
-        let size = available.stack.len();
-        unsafe {
-            let s_ptr = available.stack.as_mut_ptr().offset(size as isize);
-
-            // make sure our stack itself is 8 byte aligned - it will always
-            // offset to a lower memory address. Since we know we're at the "high"
-            // memory address of our allocated space, we know that offsetting to
-            // a lower one will be a valid address (given that we actually allocated)
-            // enough space to actually get an aligned pointer in the first place).
-            let s_ptr = (s_ptr as usize & !7) as *mut u8;
-
-            available.ctx.x1 = guard as u64; //ctx.x1  is old return address
-            available.ctx.nx1 = f as u64; //ctx.nx2 is new return address
-            available.ctx.x2 = s_ptr.offset(-32) as u64; //cxt.x2 is sp
-        }
-        available.state = State::Ready;
-    }
-}
-
-/// This is our guard function that we place on top of the stack. All this function does is set the
-/// state of our current task and then `yield` which will then schedule a new task to be run.
-fn guard() {
-    unsafe {
-        let rt_ptr = RUNTIME as *mut Runtime;
-        (*rt_ptr).t_return();
-    };
-}
-
-/// We know that Runtime is alive the length of the program and that we only access from one core
-/// (so no datarace). We yield execution of the current task  by dereferencing a pointer to our
-/// Runtime and then calling `t_yield`
-pub fn yield_task() {
-    unsafe {
-        let rt_ptr = RUNTIME as *mut Runtime;
-        (*rt_ptr).t_yield();
-    };
-}
-
-/// So here is our inline Assembly. As you remember from our first example this is just a bit more elaborate where we first
-/// read out the values of all the registers we need and then sets all the register values to the register values we
-/// saved when we suspended exceution on the "new" task.
-///
-/// This is essentially all we need to do to save and resume execution.
-///
-/// Some details about inline assembly.
-///
-/// The assembly commands in the string literal is called the assemblt template. It is preceeded by
-/// zero or up to four segments indicated by ":":
-///
-/// - First ":" we have our output parameters, this parameters that this function will return.
-/// - Second ":" we have the input parameters which is our contexts. We only read from the "new" context
-/// but we modify the "old" context saving our registers there (see volatile option below)
-/// - Third ":" This our clobber list, this is information to the compiler that these registers can't be used freely
-/// - Fourth ":" This is options we can pass inn, Rust has 3: "alignstack", "volatile" and "intel"
-///
-/// For this to work on windows we need to use "alignstack" where the compiler adds the neccesary padding to
-/// make sure our stack is aligned. Since we modify one of our inputs, our assembly has "side effects"
-/// therefore we should use the `volatile` option. I **think** this is actually set for us by default
-/// when there are no output parameters given (my own assumption after going through the source code)
-/// for the `asm` macro, but we should make it explicit anyway.
-///
-/// One last important part (it will not work without this) is the #[naked] attribute. Basically this lets us have full
-/// control over the stack layout since normal functions has a prologue-and epilogue added by the
-/// compiler that will cause trouble for us. We avoid this by marking the funtion as "Naked".
-/// For this to work on `release` builds we also need to use the `#[inline(never)] attribute or else
-/// the compiler decides to inline this function (curiously this currently only happens on Windows).
-/// If the function is inlined we get a curious runtime error where it fails when switching back
-/// to as saved context and in general our assembly will not work as expected.
-///
-/// see: https://github.com/rust-lang/rfcs/blob/master/text/1201-naked-fns.md
-/// see: https://doc.rust-lang.org/nightly/reference/inline-assembly.html
-/// see: https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html
-#[naked]
-#[no_mangle]
-unsafe extern "C" fn switch(old: *mut TaskContext, new: *const TaskContext) {
-    // a0: _old, a1: _new
-    asm!(
-        "
-        sd x1, 0x00(a0)
-        sd x2, 0x08(a0)
-        sd x8, 0x10(a0)
-        sd x9, 0x18(a0)
-        sd x18, 0x20(a0)
-        sd x19, 0x28(a0)
-        sd x20, 0x30(a0)
-        sd x21, 0x38(a0)
-        sd x22, 0x40(a0)
-        sd x23, 0x48(a0)
-        sd x24, 0x50(a0)
-        sd x25, 0x58(a0)
-        sd x26, 0x60(a0)
-        sd x27, 0x68(a0)
-        sd x1, 0x70(a0)
-
-        ld x1, 0x00(a1)
-        ld x2, 0x08(a1)
-        ld x8, 0x10(a1)
-        ld x9, 0x18(a1)
-        ld x18, 0x20(a1)
-        ld x19, 0x28(a1)
-        ld x20, 0x30(a1)
-        ld x21, 0x38(a1)
-        ld x22, 0x40(a1)
-        ld x23, 0x48(a1)
-        ld x24, 0x50(a1)
-        ld x25, 0x58(a1)
-        ld x26, 0x60(a1)
-        ld x27, 0x68(a1)
-        ld t0, 0x70(a1)
-
-        jr t0
-    ",
-        options(noreturn)
-    );
-}
-
-#[no_mangle]
-pub fn main() {
-    println!("stackful_coroutine begin...");
-    println!("TASK  0(Runtime) STARTING");
-    let mut runtime = Runtime::new();
-    runtime.init();
-    runtime.spawn(|| {
-        println!("TASK  1 STARTING");
-        let id = 1;
-        for i in 0..4 {
-            println!("task: {} counter: {}", id, i);
-            yield_task();
-        }
-        println!("TASK 1 FINISHED");
-    });
-    runtime.spawn(|| {
-        println!("TASK 2 STARTING");
-        let id = 2;
-        for i in 0..8 {
-            println!("task: {} counter: {}", id, i);
-            yield_task();
-        }
-        println!("TASK 2 FINISHED");
-    });
-    runtime.spawn(|| {
-        println!("TASK 3 STARTING");
-        let id = 3;
-        for i in 0..12 {
-            println!("task: {} counter: {}", id, i);
-            yield_task();
-        }
-        println!("TASK 3 FINISHED");
-    });
-    runtime.spawn(|| {
-        println!("TASK 4 STARTING");
-        let id = 4;
-        for i in 0..16 {
-            println!("task: {} counter: {}", id, i);
-            yield_task();
-        }
-        println!("TASK 4 FINISHED");
-    });
-    runtime.run();
-    println!("stackful_coroutine PASSED");
-    exit(0);
-}
diff --git a/user/src/bin/stackless_coroutine.rs b/user/src/bin/stackless_coroutine.rs
deleted file mode 100644
index 43aeb2d..0000000
--- a/user/src/bin/stackless_coroutine.rs
+++ /dev/null
@@ -1,129 +0,0 @@
-// https://blog.aloni.org/posts/a-stack-less-rust-coroutine-100-loc/
-// https://github.com/chyyuu/example-coroutine-and-thread/tree/stackless-coroutine-x86
-#![no_std]
-#![no_main]
-
-use core::future::Future;
-use core::pin::Pin;
-use core::task::{Context, Poll};
-use core::task::{RawWaker, RawWakerVTable, Waker};
-
-extern crate alloc;
-use alloc::collections::VecDeque;
-
-use alloc::boxed::Box;
-
-#[macro_use]
-extern crate user_lib;
-
-enum State {
-    Halted,
-    Running,
-}
-
-struct Task {
-    state: State,
-}
-
-impl Task {
-    fn waiter<'a>(&'a mut self) -> Waiter<'a> {
-        Waiter { task: self }
-    }
-}
-
-struct Waiter<'a> {
-    task: &'a mut Task,
-}
-
-impl<'a> Future for Waiter<'a> {
-    type Output = ();
-
-    fn poll(mut self: Pin<&mut Self>, _cx: &mut Context) -> Poll<Self::Output> {
-        match self.task.state {
-            State::Halted => {
-                self.task.state = State::Running;
-                Poll::Ready(())
-            }
-            State::Running => {
-                self.task.state = State::Halted;
-                Poll::Pending
-            }
-        }
-    }
-}
-
-struct Executor {
-    tasks: VecDeque<Pin<Box<dyn Future<Output = ()>>>>,
-}
-
-impl Executor {
-    fn new() -> Self {
-        Executor {
-            tasks: VecDeque::new(),
-        }
-    }
-
-    fn push<C, F>(&mut self, closure: C)
-    where
-        F: Future<Output = ()> + 'static,
-        C: FnOnce(Task) -> F,
-    {
-        let task = Task {
-            state: State::Running,
-        };
-        self.tasks.push_back(Box::pin(closure(task)));
-    }
-
-    fn run(&mut self) {
-        let waker = create_waker();
-        let mut context = Context::from_waker(&waker);
-
-        while let Some(mut task) = self.tasks.pop_front() {
-            match task.as_mut().poll(&mut context) {
-                Poll::Pending => {
-                    self.tasks.push_back(task);
-                }
-                Poll::Ready(()) => {}
-            }
-        }
-    }
-}
-
-pub fn create_waker() -> Waker {
-    // Safety: The waker points to a vtable with functions that do nothing. Doing
-    // nothing is memory-safe.
-    unsafe { Waker::from_raw(RAW_WAKER) }
-}
-
-const RAW_WAKER: RawWaker = RawWaker::new(core::ptr::null(), &VTABLE);
-const VTABLE: RawWakerVTable = RawWakerVTable::new(clone, wake, wake_by_ref, drop);
-
-unsafe fn clone(_: *const ()) -> RawWaker {
-    RAW_WAKER
-}
-unsafe fn wake(_: *const ()) {}
-unsafe fn wake_by_ref(_: *const ()) {}
-unsafe fn drop(_: *const ()) {}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    println!("stackless coroutine Begin..");
-    let mut exec = Executor::new();
-    println!(" Create futures");
-    for instance in 1..=3 {
-        exec.push(move |mut task| async move {
-            println!("   Task {}: begin state", instance);
-            task.waiter().await;
-            println!("   Task {}: next state", instance);
-            task.waiter().await;
-            println!("   Task {}: end state", instance);
-        });
-    }
-
-    println!(" Running");
-    exec.run();
-    println!(" Done");
-    println!("stackless coroutine PASSED");
-
-    0
-}
diff --git a/user/src/bin/store_fault.rs b/user/src/bin/store_fault.rs
deleted file mode 100644
index f8023eb..0000000
--- a/user/src/bin/store_fault.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-#[no_mangle]
-fn main() -> i32 {
-    println!("Into Test store_fault, we will insert an invalid store operation...");
-    println!("Kernel should kill this application!");
-    unsafe {
-        core::ptr::null_mut::<u8>().write_volatile(0);
-    }
-    0
-}
diff --git a/user/src/bin/sync_sem.rs b/user/src/bin/sync_sem.rs
deleted file mode 100644
index b8d1f79..0000000
--- a/user/src/bin/sync_sem.rs
+++ /dev/null
@@ -1,45 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-extern crate alloc;
-
-use alloc::vec;
-use user_lib::exit;
-use user_lib::{semaphore_create, semaphore_down, semaphore_up};
-use user_lib::{sleep, thread_create, waittid};
-
-const SEM_SYNC: usize = 0;
-
-unsafe fn first() -> ! {
-    sleep(10);
-    println!("First work and wakeup Second");
-    semaphore_up(SEM_SYNC);
-    exit(0)
-}
-
-unsafe fn second() -> ! {
-    println!("Second want to continue,but need to wait first");
-    semaphore_down(SEM_SYNC);
-    println!("Second can work now");
-    exit(0)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    // create semaphores
-    assert_eq!(semaphore_create(0) as usize, SEM_SYNC);
-    // create threads
-    let threads = vec![
-        thread_create(first as usize, 0),
-        thread_create(second as usize, 0),
-    ];
-    // wait for all threads to complete
-    for thread in threads.iter() {
-        waittid(*thread as usize);
-    }
-    println!("sync_sem passed!");
-    0
-}
diff --git a/user/src/bin/tcp_simplehttp.rs b/user/src/bin/tcp_simplehttp.rs
deleted file mode 100644
index 3e61950..0000000
--- a/user/src/bin/tcp_simplehttp.rs
+++ /dev/null
@@ -1,188 +0,0 @@
-#![no_std]
-#![no_main]
-
-use alloc::string::{String, ToString};
-
-#[macro_use]
-extern crate user_lib;
-#[macro_use]
-extern crate alloc;
-
-// use http://localhost:6201/ to access the http server
-
-use user_lib::{accept, listen, read, write};
-
-// get url from the tcp request list.
-fn get_url_from_tcp_request(req: &[u8]) -> String {
-    let mut index = 0;
-    for i in 4..req.len() {
-        if req[i] == 0x20 {
-            index = i;
-            break;
-        }
-    }
-
-    String::from_utf8_lossy(&req[4..index]).to_string()
-}
-
-// just receive GET requests
-fn handle_tcp_client(client_fd: usize) -> bool {
-    // a buf to receive the data from the server
-    let mut buf = vec![0u8; 1024];
-
-    let len = read(client_fd as usize, &mut buf);
-
-    println!("receive {} bytes", len);
-    hexdump(&buf[..len as usize]);
-
-    // verify whether it is a valid HTTP request simply, [0x47,0x45,0x54, 0x20] is GET
-    if len < 4 || buf[..4] != [0x47, 0x45, 0x54, 0x20] {
-        println!("it's not a valid http request");
-        return false;
-    }
-
-    let url = get_url_from_tcp_request(&buf);
-
-    if url == "/close" {
-        let content = r#"<!DOCTYPE html>
-        <html>
-        <head>
-        <title></title>
-        <meta charset="utf-8">
-        <meta name="viewport" content="width=device-width, initial-scale=1">
-        <link href="https://cdn.staticfile.org/twitter-bootstrap/5.1.1/css/bootstrap.min.css" rel="stylesheet">
-        <script src="https://cdn.staticfile.org/twitter-bootstrap/5.1.1/js/bootstrap.bundle.min.js"></script>
-        </head>
-        <body>
-        
-        <div class="container-fluid p-5 bg-danger text-white text-center">
-        <h1>server closed</h1>
-        </div>
-        </body>
-        </html>"#;
-        let response = format!("HTTP/1.1 200 OK\r\nContent-Type: text/html\r\nContent-Length: {}\r\nConnecion: Close\r\n\r\n{}", content.len(),content);
-        write(client_fd, response.as_bytes());
-        // terminate the connection immediately.
-        return true;
-    }
-
-    let content = r#"<!DOCTYPE html>
-        <html>
-        <head>
-        <title></title>
-        <meta charset="utf-8">
-        <meta name="viewport" content="width=device-width, initial-scale=1">
-        <link href="https://cdn.staticfile.org/twitter-bootstrap/5.1.1/css/bootstrap.min.css" rel="stylesheet">
-        <script src="https://cdn.staticfile.org/twitter-bootstrap/5.1.1/js/bootstrap.bundle.min.js"></script>
-        </head>
-        <body>
-        
-        <div class="container-fluid p-5 bg-primary text-white text-center">
-        <h1>rCore-tutorial-V3</h1>
-        <p>rCore-tutorial-V3 是一个 基于 RISC-V 架构的 类 Unix 内核.</p> 
-        </div>
-        
-        <div class="container mt-5">
-        <div class="row">
-            <div class="col-sm-4">
-            <h3>Rust</h3>
-            <p>Rust</p>
-            <p>Rust是一门系统编程语言，专注于安全，尤其是并发安全，支持函数式和命令式以及泛型等编程范式的多范式语言</p>
-            </div>
-            <div class="col-sm-4">
-            <h3>仓库地址</h3>        
-            <p>repo url</p>
-            <p>https://github.com/rcore-os/rCore-Tutorial-v3</p>
-            </div>
-            <div class="col-sm-4">
-            <h3>QQ 群号</h3>        
-            <p>Official QQ group number</p>
-            <p>735045051</p>
-            </div>
-        </div>
-        </div>
-        
-        <div class="container p-5 text-black text-center d-grid col-sm-4">
-        <p>点击下列按钮即可关闭服务器。</p>
-        <button type="button" class="btn btn-warning btn-block p-3" onclick="close_server()">关闭 server</button>
-        </div>
-        <script>
-        function close_server() {
-            location.href = "/close";
-        }
-        </script>
-        </body>
-        </html>"#;
-
-    let response = format!("HTTP/1.1 200 OK\r\nContent-Type: text/html\r\nContent-Length: {}\r\nConnecion: Close\r\n\r\n{}", content.len(),content);
-
-    // write a response
-    write(client_fd, response.as_bytes());
-
-    false
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    println!("This is a very simple http server");
-
-    let tcp_fd = listen(80);
-
-    if tcp_fd < 0 {
-        println!("Failed to listen on port 80");
-        return -1;
-    }
-
-    loop {
-        let client = accept(tcp_fd as usize);
-        println!("client connected: {}", client);
-
-        if client < 1 {
-            println!("Failed to accept a client on port 80");
-            return -1;
-        }
-
-        if handle_tcp_client(client as usize) {
-            break;
-        }
-    }
-
-    println!("finish tcp test");
-
-    // String::from_utf8_lossy(&buf[..len as usize])
-
-    0
-}
-
-#[allow(unused)]
-pub fn hexdump(data: &[u8]) {
-    const PRELAND_WIDTH: usize = 70;
-    println!("{:-^1$}", " hexdump ", PRELAND_WIDTH);
-    for offset in (0..data.len()).step_by(16) {
-        for i in 0..16 {
-            if offset + i < data.len() {
-                print!("{:02x} ", data[offset + i]);
-            } else {
-                print!("{:02} ", "");
-            }
-        }
-
-        print!("{:>6}", ' ');
-
-        for i in 0..16 {
-            if offset + i < data.len() {
-                let c = data[offset + i];
-                if c >= 0x20 && c <= 0x7e {
-                    print!("{}", c as char);
-                } else {
-                    print!(".");
-                }
-            } else {
-                print!("{:02} ", "");
-            }
-        }
-
-        println!("");
-    }
-    println!("{:-^1$}", " hexdump end ", PRELAND_WIDTH);
-}
diff --git a/user/src/bin/threads.rs b/user/src/bin/threads.rs
deleted file mode 100644
index 3d374fe..0000000
--- a/user/src/bin/threads.rs
+++ /dev/null
@@ -1,45 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec;
-use user_lib::{exit, thread_create, waittid};
-
-pub fn thread_a() -> ! {
-    for _ in 0..1000 {
-        print!("a");
-    }
-    exit(1)
-}
-
-pub fn thread_b() -> ! {
-    for _ in 0..1000 {
-        print!("b");
-    }
-    exit(2)
-}
-
-pub fn thread_c() -> ! {
-    for _ in 0..1000 {
-        print!("c");
-    }
-    exit(3)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let v = vec![
-        thread_create(thread_a as usize, 0),
-        thread_create(thread_b as usize, 0),
-        thread_create(thread_c as usize, 0),
-    ];
-    for tid in v.iter() {
-        let exit_code = waittid(*tid as usize);
-        println!("thread#{} exited with code {}", tid, exit_code);
-    }
-    println!("main thread exited.");
-    0
-}
diff --git a/user/src/bin/threads_arg.rs b/user/src/bin/threads_arg.rs
deleted file mode 100644
index c5b26ed..0000000
--- a/user/src/bin/threads_arg.rs
+++ /dev/null
@@ -1,44 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-extern crate alloc;
-
-use alloc::vec::Vec;
-use user_lib::{exit, thread_create, waittid};
-
-struct Argument {
-    pub ch: char,
-    pub rc: i32,
-}
-
-fn thread_print(arg: *const Argument) -> ! {
-    let arg = unsafe { &*arg };
-    for _ in 0..1000 {
-        print!("{}", arg.ch);
-    }
-    exit(arg.rc)
-}
-
-#[no_mangle]
-pub fn main() -> i32 {
-    let mut v = Vec::new();
-    let args = [
-        Argument { ch: 'a', rc: 1 },
-        Argument { ch: 'b', rc: 2 },
-        Argument { ch: 'c', rc: 3 },
-    ];
-    for arg in args.iter() {
-        v.push(thread_create(
-            thread_print as usize,
-            arg as *const _ as usize,
-        ));
-    }
-    for tid in v.iter() {
-        let exit_code = waittid(*tid as usize);
-        println!("thread#{} exited with code {}", tid, exit_code);
-    }
-    println!("main thread exited.");
-    0
-}
diff --git a/user/src/bin/udp.rs b/user/src/bin/udp.rs
deleted file mode 100644
index 68a1a10..0000000
--- a/user/src/bin/udp.rs
+++ /dev/null
@@ -1,46 +0,0 @@
-#![no_std]
-#![no_main]
-
-use alloc::string::String;
-
-#[macro_use]
-extern crate user_lib;
-#[macro_use]
-extern crate alloc;
-
-use user_lib::{connect, read, write};
-
-#[no_mangle]
-pub fn main() -> i32 {
-    println!("udp test open!");
-
-    let udp_fd = connect(10 << 24 | 0 << 16 | 2 << 8 | 2, 2001, 26099);
-
-    if udp_fd < 0 {
-        println!("failed to create udp connection.");
-        return -1;
-    }
-
-    let buf = "Hello rCoreOS user program!";
-
-    println!("send <{}>", buf);
-
-    write(udp_fd as usize, buf.as_bytes());
-
-    println!("udp send done, waiting for reply.");
-
-    let mut buf = vec![0u8; 1024];
-
-    let len = read(udp_fd as usize, &mut buf);
-
-    if len < 0 {
-        println!("can't receive udp packet");
-        return -1;
-    }
-
-    let recv_str = String::from_utf8_lossy(&buf[..len as usize]);
-
-    println!("receive reply <{}>", recv_str);
-
-    0
-}
diff --git a/user/src/bin/until_timeout.rs b/user/src/bin/until_timeout.rs
deleted file mode 100644
index a0007cb..0000000
--- a/user/src/bin/until_timeout.rs
+++ /dev/null
@@ -1,46 +0,0 @@
-#![no_std]
-#![no_main]
-
-#[macro_use]
-extern crate user_lib;
-
-use user_lib::{exec, fork, get_time, kill, waitpid, waitpid_nb, SignalFlags};
-
-#[no_mangle]
-pub fn main(argc: usize, argv: &[&str]) -> i32 {
-    assert_eq!(argc, 3, "argc must be 3!");
-    let timeout_ms = argv[2]
-        .parse::<isize>()
-        .expect("Error when parsing timeout!");
-    let pid = fork() as usize;
-    if pid == 0 {
-        if exec(argv[1], &[core::ptr::null::<u8>()]) != 0 {
-            println!("Error when executing '{}'", argv[1]);
-            return -4;
-        }
-    } else {
-        let start_time = get_time();
-        let mut child_exited = false;
-        let mut exit_code: i32 = 0;
-        loop {
-            if get_time() - start_time > timeout_ms {
-                break;
-            }
-            if waitpid_nb(pid, &mut exit_code) as usize == pid {
-                child_exited = true;
-                println!(
-                    "child exited in {}ms, exit_code = {}",
-                    get_time() - start_time,
-                    exit_code,
-                );
-            }
-        }
-        if !child_exited {
-            println!("child has run for {}ms, kill it!", timeout_ms);
-            kill(pid, SignalFlags::SIGINT.bits());
-            assert_eq!(waitpid(pid, &mut exit_code) as usize, pid);
-            println!("exit code of the child is {}", exit_code);
-        }
-    }
-    0
-}
diff --git a/user/src/bin/user_shell.rs b/user/src/bin/user_shell.rs
index 4288248..1ca120b 100644
--- a/user/src/bin/user_shell.rs
+++ b/user/src/bin/user_shell.rs
@@ -11,191 +11,40 @@ const LF: u8 = 0x0au8;
 const CR: u8 = 0x0du8;
 const DL: u8 = 0x7fu8;
 const BS: u8 = 0x08u8;
-const LINE_START: &str = ">> ";
 
 use alloc::string::String;
-use alloc::vec::Vec;
 use user_lib::console::getchar;
-use user_lib::{close, dup, exec, fork, open, pipe, waitpid, OpenFlags};
+use user_lib::{exec, fork, waitpid};
 
-#[derive(Debug)]
-struct ProcessArguments {
-    input: String,
-    output: String,
-    args_copy: Vec<String>,
-    args_addr: Vec<*const u8>,
-}
-
-impl ProcessArguments {
-    pub fn new(command: &str) -> Self {
-        let args: Vec<_> = command.split(' ').collect();
-        let mut args_copy: Vec<String> = args
-            .iter()
-            .filter(|&arg| !arg.is_empty())
-            .map(|&arg| {
-                let mut string = String::new();
-                string.push_str(arg);
-                string.push('\0');
-                string
-            })
-            .collect();
-
-        // redirect input
-        let mut input = String::new();
-        if let Some((idx, _)) = args_copy
-            .iter()
-            .enumerate()
-            .find(|(_, arg)| arg.as_str() == "<\0")
-        {
-            input = args_copy[idx + 1].clone();
-            args_copy.drain(idx..=idx + 1);
-        }
-
-        // redirect output
-        let mut output = String::new();
-        if let Some((idx, _)) = args_copy
-            .iter()
-            .enumerate()
-            .find(|(_, arg)| arg.as_str() == ">\0")
-        {
-            output = args_copy[idx + 1].clone();
-            args_copy.drain(idx..=idx + 1);
-        }
-
-        let mut args_addr: Vec<*const u8> = args_copy.iter().map(|arg| arg.as_ptr()).collect();
-        args_addr.push(core::ptr::null::<u8>());
-
-        Self {
-            input,
-            output,
-            args_copy,
-            args_addr,
-        }
-    }
-}
-
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!("Rust user shell");
     let mut line: String = String::new();
-    print!("{}", LINE_START);
+    print!(">> ");
     loop {
         let c = getchar();
         match c {
             LF | CR => {
                 println!("");
                 if !line.is_empty() {
-                    let splited: Vec<_> = line.as_str().split('|').collect();
-                    let process_arguments_list: Vec<_> = splited
-                        .iter()
-                        .map(|&cmd| ProcessArguments::new(cmd))
-                        .collect();
-                    let mut valid = true;
-                    for (i, process_args) in process_arguments_list.iter().enumerate() {
-                        if i == 0 {
-                            if !process_args.output.is_empty() {
-                                valid = false;
-                            }
-                        } else if i == process_arguments_list.len() - 1 {
-                            if !process_args.input.is_empty() {
-                                valid = false;
-                            }
-                        } else if !process_args.output.is_empty() || !process_args.input.is_empty()
-                        {
-                            valid = false;
+                    line.push('\0');
+                    let pid = fork();
+                    if pid == 0 {
+                        // child process
+                        if exec(line.as_str()) == -1 {
+                            println!("Error when executing!");
+                            return -4;
                         }
-                    }
-                    if process_arguments_list.len() == 1 {
-                        valid = true;
-                    }
-                    if !valid {
-                        println!("Invalid command: Inputs/Outputs cannot be correctly binded!");
+                        unreachable!();
                     } else {
-                        // create pipes
-                        let mut pipes_fd: Vec<[usize; 2]> = Vec::new();
-                        if !process_arguments_list.is_empty() {
-                            for _ in 0..process_arguments_list.len() - 1 {
-                                let mut pipe_fd = [0usize; 2];
-                                pipe(&mut pipe_fd);
-                                pipes_fd.push(pipe_fd);
-                            }
-                        }
-                        let mut children: Vec<_> = Vec::new();
-                        for (i, process_argument) in process_arguments_list.iter().enumerate() {
-                            let pid = fork();
-                            if pid == 0 {
-                                let input = &process_argument.input;
-                                let output = &process_argument.output;
-                                let args_copy = &process_argument.args_copy;
-                                let args_addr = &process_argument.args_addr;
-                                // redirect input
-                                if !input.is_empty() {
-                                    let input_fd = open(input.as_str(), OpenFlags::RDONLY);
-                                    if input_fd == -1 {
-                                        println!("Error when opening file {}", input);
-                                        return -4;
-                                    }
-                                    let input_fd = input_fd as usize;
-                                    close(0);
-                                    assert_eq!(dup(input_fd), 0);
-                                    close(input_fd);
-                                }
-                                // redirect output
-                                if !output.is_empty() {
-                                    let output_fd = open(
-                                        output.as_str(),
-                                        OpenFlags::CREATE | OpenFlags::WRONLY,
-                                    );
-                                    if output_fd == -1 {
-                                        println!("Error when opening file {}", output);
-                                        return -4;
-                                    }
-                                    let output_fd = output_fd as usize;
-                                    close(1);
-                                    assert_eq!(dup(output_fd), 1);
-                                    close(output_fd);
-                                }
-                                // receive input from the previous process
-                                if i > 0 {
-                                    close(0);
-                                    let read_end = pipes_fd.get(i - 1).unwrap()[0];
-                                    assert_eq!(dup(read_end), 0);
-                                }
-                                // send output to the next process
-                                if i < process_arguments_list.len() - 1 {
-                                    close(1);
-                                    let write_end = pipes_fd.get(i).unwrap()[1];
-                                    assert_eq!(dup(write_end), 1);
-                                }
-                                // close all pipe ends inherited from the parent process
-                                for pipe_fd in pipes_fd.iter() {
-                                    close(pipe_fd[0]);
-                                    close(pipe_fd[1]);
-                                }
-                                // execute new application
-                                if exec(args_copy[0].as_str(), args_addr.as_slice()) == -1 {
-                                    println!("Error when executing!");
-                                    return -4;
-                                }
-                                unreachable!();
-                            } else {
-                                children.push(pid);
-                            }
-                        }
-                        for pipe_fd in pipes_fd.iter() {
-                            close(pipe_fd[0]);
-                            close(pipe_fd[1]);
-                        }
                         let mut exit_code: i32 = 0;
-                        for pid in children.into_iter() {
-                            let exit_pid = waitpid(pid as usize, &mut exit_code);
-                            assert_eq!(pid, exit_pid);
-                            //println!("Shell: Process {} exited with code {}", pid, exit_code);
-                        }
+                        let exit_pid = waitpid(pid as usize, &mut exit_code);
+                        assert_eq!(pid, exit_pid);
+                        println!("Shell: Process {} exited with code {}", pid, exit_code);
                     }
                     line.clear();
                 }
-                print!("{}", LINE_START);
+                print!(">> ");
             }
             BS | DL => {
                 if !line.is_empty() {
diff --git a/user/src/bin/usertests.rs b/user/src/bin/usertests.rs
index b522af2..d47dc20 100644
--- a/user/src/bin/usertests.rs
+++ b/user/src/bin/usertests.rs
@@ -10,9 +10,7 @@ extern crate user_lib;
 // item of TESTS : app_name(argv_0), argv_1, argv_2, argv_3, exit_code
 static SUCC_TESTS: &[(&str, &str, &str, &str, i32)] = &[
     ("filetest_simple\0", "\0", "\0", "\0", 0),
-    ("cat\0", "filea\0", "\0", "\0", 0),
-    ("cmdline_args\0", "1\0", "2\0", "3\0", 0),
-    ("eisenberg\0", "\0", "\0", "\0", 0),
+    ("cat_filea\0", "\0", "\0", "\0", 0),
     ("exit\0", "\0", "\0", "\0", 0),
     ("fantastic_text\0", "\0", "\0", "\0", 0),
     ("forktest_simple\0", "\0", "\0", "\0", 0),
@@ -22,40 +20,12 @@ static SUCC_TESTS: &[(&str, &str, &str, &str, i32)] = &[
     ("hello_world\0", "\0", "\0", "\0", 0),
     ("huge_write\0", "\0", "\0", "\0", 0),
     ("matrix\0", "\0", "\0", "\0", 0),
-    ("mpsc_sem\0", "\0", "\0", "\0", 0),
-    ("peterson\0", "\0", "\0", "\0", 0),
-    ("phil_din_mutex\0", "\0", "\0", "\0", 0),
-    ("pipe_large_test\0", "\0", "\0", "\0", 0),
-    ("pipetest\0", "\0", "\0", "\0", 0),
-    ("adder_peterson_spin\0", "\0", "\0", "\0", 0),
-    ("adder_peterson_yield\0", "\0", "\0", "\0", 0),
-    ("adder_mutex_blocking\0", "\0", "\0", "\0", 0),
-    ("adder_mutex_spin\0", "\0", "\0", "\0", 0),
-    ("run_pipe_test\0", "\0", "\0", "\0", 0),
     ("sleep_simple\0", "\0", "\0", "\0", 0),
     ("sleep\0", "\0", "\0", "\0", 0),
-    ("sleep_simple\0", "\0", "\0", "\0", 0),
-    ("sync_sem\0", "\0", "\0", "\0", 0),
-    ("condsync_sem\0", "\0", "\0", "\0", 0),
-    ("condsync_condvar\0", "\0", "\0", "\0", 0),
-    ("threads_arg\0", "\0", "\0", "\0", 0),
-    ("threads\0", "\0", "\0", "\0", 0),
     ("yield\0", "\0", "\0", "\0", 0),
-    ("barrier_fail\0", "\0", "\0", "\0", 0),
-    ("barrier_condvar\0", "\0", "\0", "\0", 0),
 ];
 
-static FAIL_TESTS: &[(&str, &str, &str, &str, i32)] = &[
-    ("stack_overflow\0", "\0", "\0", "\0", -11),
-    ("race_adder_loop\0", "\0", "\0", "\0", -6),
-    ("priv_csr\0", "\0", "\0", "\0", -4),
-    ("priv_inst\0", "\0", "\0", "\0", -4),
-    ("store_fault\0", "\0", "\0", "\0", -11),
-    ("until_timeout\0", "\0", "\0", "\0", -6),
-    ("adder\0", "\0", "\0", "\0", -6),
-    ("adder_simple_spin\0", "\0", "\0", "\0", -6),
-    ("adder_simple_yield\0", "\0", "\0", "\0", -6),
-];
+static FAIL_TESTS: &[(&str, &str, &str, &str, i32)] = &[("stack_overflow\0", "\0", "\0", "\0", -2)];
 
 use user_lib::{exec, fork, waitpid};
 
@@ -95,7 +65,7 @@ fn run_tests(tests: &[(&str, &str, &str, &str, i32)]) -> i32 {
 
         let pid = fork();
         if pid == 0 {
-            exec(test.0, &arr[..]);
+            exec(test.0);
             panic!("unreachable!");
         } else {
             let mut exit_code: i32 = Default::default();
@@ -114,7 +84,7 @@ fn run_tests(tests: &[(&str, &str, &str, &str, i32)]) -> i32 {
     pass_num
 }
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     let succ_num = run_tests(SUCC_TESTS);
     let err_num = run_tests(FAIL_TESTS);
diff --git a/user/src/bin/usertests_simple.rs b/user/src/bin/usertests_simple.rs
new file mode 100644
index 0000000..0a73edd
--- /dev/null
+++ b/user/src/bin/usertests_simple.rs
@@ -0,0 +1,43 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+
+static TESTS: &[&str] = &[
+    "exit\0",
+    "fantastic_text\0",
+    "forktest\0",
+    "forktest2\0",
+    "forktest_simple\0",
+    "hello_world\0",
+    "matrix\0",
+    "sleep\0",
+    "sleep_simple\0",
+    "stack_overflow\0",
+    "yield\0",
+];
+
+use user_lib::{exec, fork, waitpid};
+
+#[unsafe(no_mangle)]
+pub fn main() -> i32 {
+    for test in TESTS {
+        println!("Usertests: Running {}", test);
+        let pid = fork();
+        if pid == 0 {
+            exec(*test);
+            panic!("unreachable!");
+        } else {
+            let mut exit_code: i32 = Default::default();
+            let wait_pid = waitpid(pid as usize, &mut exit_code);
+            assert_eq!(pid, wait_pid);
+            println!(
+                "\x1b[32mUsertests: Test {} in Process {} exited with code {}\x1b[0m",
+                test, pid, exit_code
+            );
+        }
+    }
+    println!("Usertests passed!");
+    0
+}
diff --git a/user/src/bin/yield.rs b/user/src/bin/yield.rs
index 78b1468..b9558ef 100644
--- a/user/src/bin/yield.rs
+++ b/user/src/bin/yield.rs
@@ -5,7 +5,7 @@
 extern crate user_lib;
 use user_lib::{getpid, yield_};
 
-#[no_mangle]
+#[unsafe(no_mangle)]
 pub fn main() -> i32 {
     println!("Hello, I am process {}.", getpid());
     for i in 0..5 {
diff --git a/user/src/file.rs b/user/src/file.rs
deleted file mode 100644
index 19e2564..0000000
--- a/user/src/file.rs
+++ /dev/null
@@ -1,30 +0,0 @@
-use super::*;
-
-bitflags! {
-    pub struct OpenFlags: u32 {
-        const RDONLY = 0;
-        const WRONLY = 1 << 0;
-        const RDWR = 1 << 1;
-        const CREATE = 1 << 9;
-        const TRUNC = 1 << 10;
-    }
-}
-
-pub fn dup(fd: usize) -> isize {
-    sys_dup(fd)
-}
-pub fn open(path: &str, flags: OpenFlags) -> isize {
-    sys_open(path, flags.bits)
-}
-pub fn close(fd: usize) -> isize {
-    sys_close(fd)
-}
-pub fn pipe(pipe_fd: &mut [usize]) -> isize {
-    sys_pipe(pipe_fd)
-}
-pub fn read(fd: usize, buf: &mut [u8]) -> isize {
-    sys_read(fd, buf)
-}
-pub fn write(fd: usize, buf: &[u8]) -> isize {
-    sys_write(fd, buf)
-}
diff --git a/user/src/io.rs b/user/src/io.rs
deleted file mode 100644
index d2c2a0a..0000000
--- a/user/src/io.rs
+++ /dev/null
@@ -1,117 +0,0 @@
-use super::*;
-use embedded_graphics::pixelcolor::Rgb888;
-use embedded_graphics::prelude::{RgbColor, Size};
-use embedded_graphics::{draw_target::DrawTarget, prelude::OriginDimensions};
-use virtio_input_decoder::Decoder;
-pub use virtio_input_decoder::{DecodeType, Key, KeyType, Mouse};
-
-pub const VIRTGPU_XRES: u32 = 1280;
-pub const VIRTGPU_YRES: u32 = 800;
-pub const VIRTGPU_LEN: usize = (VIRTGPU_XRES * VIRTGPU_YRES * 4) as usize;
-
-pub fn framebuffer() -> isize {
-    sys_framebuffer()
-}
-pub fn framebuffer_flush() -> isize {
-    sys_framebuffer_flush()
-}
-
-pub struct Display {
-    pub size: Size,
-    pub fb: &'static mut [u8],
-}
-
-impl Display {
-    pub fn new(size: Size) -> Self {
-        let fb_ptr = framebuffer() as *mut u8;
-        let fb = unsafe { core::slice::from_raw_parts_mut(fb_ptr, VIRTGPU_LEN as usize) };
-        Self { size, fb }
-    }
-    pub fn framebuffer(&mut self) -> &mut [u8] {
-        self.fb
-    }
-    pub fn paint_on_framebuffer(&mut self, p: impl FnOnce(&mut [u8]) -> ()) {
-        p(self.framebuffer());
-    }
-    pub fn flush(&self) {
-        framebuffer_flush();
-    }
-}
-
-impl OriginDimensions for Display {
-    fn size(&self) -> Size {
-        self.size
-    }
-}
-
-impl DrawTarget for Display {
-    type Color = Rgb888;
-
-    type Error = core::convert::Infallible;
-
-    fn draw_iter<I>(&mut self, pixels: I) -> Result<(), Self::Error>
-    where
-        I: IntoIterator<Item = embedded_graphics::Pixel<Self::Color>>,
-    {
-        pixels.into_iter().for_each(|px| {
-            let idx = (px.0.y * VIRTGPU_XRES as i32 + px.0.x) as usize * 4;
-            if idx + 2 >= self.fb.len() {
-                return;
-            }
-            self.fb[idx] = px.1.b();
-            self.fb[idx + 1] = px.1.g();
-            self.fb[idx + 2] = px.1.r();
-        });
-        Ok(())
-    }
-}
-
-pub fn event_get() -> Option<InputEvent> {
-    let raw_value = sys_event_get();
-    if raw_value == 0 {
-        None
-    } else {
-        Some((raw_value as u64).into())
-    }
-}
-
-pub fn key_pressed() -> bool {
-    if sys_key_pressed() == 1 {
-        true
-    } else {
-        false
-    }
-}
-
-#[repr(C)]
-pub struct InputEvent {
-    pub event_type: u16,
-    pub code: u16,
-    pub value: u32,
-}
-
-impl From<u64> for InputEvent {
-    fn from(mut v: u64) -> Self {
-        let value = v as u32;
-        v >>= 32;
-        let code = v as u16;
-        v >>= 16;
-        let event_type = v as u16;
-        Self {
-            event_type,
-            code,
-            value,
-        }
-    }
-}
-
-impl InputEvent {
-    pub fn decode(&self) -> Option<DecodeType> {
-        Decoder::decode(
-            self.event_type as usize,
-            self.code as usize,
-            self.value as usize,
-        )
-        .ok()
-    }
-}
diff --git a/user/src/lang_items.rs b/user/src/lang_items.rs
index df0467c..b03e8eb 100644
--- a/user/src/lang_items.rs
+++ b/user/src/lang_items.rs
@@ -1,8 +1,8 @@
-use super::{getpid, kill, SignalFlags};
+use super::exit;
 
 #[panic_handler]
 fn panic_handler(panic_info: &core::panic::PanicInfo) -> ! {
-    let err = panic_info.message().unwrap();
+    let err = panic_info.message();
     if let Some(location) = panic_info.location() {
         println!(
             "Panicked at {}:{}, {}",
@@ -13,6 +13,5 @@ fn panic_handler(panic_info: &core::panic::PanicInfo) -> ! {
     } else {
         println!("Panicked: {}", err);
     }
-    kill(getpid() as usize, SignalFlags::SIGABRT.bits());
-    unreachable!()
+    exit(-1);
 }
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 8c709fc..a5584c2 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -1,30 +1,19 @@
 #![no_std]
 #![feature(linkage)]
-#![feature(panic_info_message)]
 #![feature(alloc_error_handler)]
 
 #[macro_use]
 pub mod console;
-mod file;
-mod io;
 mod lang_items;
-mod net;
-mod sync;
 mod syscall;
-mod task;
 
 extern crate alloc;
 #[macro_use]
 extern crate bitflags;
 
-use alloc::vec::Vec;
 use buddy_system_allocator::LockedHeap;
-pub use file::*;
-pub use io::*;
-pub use net::*;
-pub use sync::*;
+use core::ptr::addr_of_mut;
 use syscall::*;
-pub use task::*;
 
 const USER_HEAP_SIZE: usize = 32768;
 
@@ -38,55 +27,88 @@ pub fn handle_alloc_error(layout: core::alloc::Layout) -> ! {
     panic!("Heap allocation error, layout = {:?}", layout);
 }
 
-#[no_mangle]
-#[link_section = ".text.entry"]
-pub extern "C" fn _start(argc: usize, argv: usize) -> ! {
+#[unsafe(no_mangle)]
+#[unsafe(link_section = ".text.entry")]
+pub extern "C" fn _start() -> ! {
     unsafe {
         HEAP.lock()
-            .init(HEAP_SPACE.as_ptr() as usize, USER_HEAP_SIZE);
+            .init(addr_of_mut!(HEAP_SPACE) as usize, USER_HEAP_SIZE);
     }
-    let mut v: Vec<&'static str> = Vec::new();
-    for i in 0..argc {
-        let str_start =
-            unsafe { ((argv + i * core::mem::size_of::<usize>()) as *const usize).read_volatile() };
-        let len = (0usize..)
-            .find(|i| unsafe { ((str_start + *i) as *const u8).read_volatile() == 0 })
-            .unwrap();
-        v.push(
-            core::str::from_utf8(unsafe {
-                core::slice::from_raw_parts(str_start as *const u8, len)
-            })
-            .unwrap(),
-        );
-    }
-    exit(main(argc, v.as_slice()));
+    exit(main());
 }
 
 #[linkage = "weak"]
-#[no_mangle]
-fn main(_argc: usize, _argv: &[&str]) -> i32 {
+#[unsafe(no_mangle)]
+fn main() -> i32 {
     panic!("Cannot find main!");
 }
 
-#[macro_export]
-macro_rules! vstore {
-    ($var: expr, $value: expr) => {
-        // unsafe { core::intrinsics::volatile_store($var_ref as *const _ as _, $value) }
-        unsafe { core::ptr::write_volatile(core::ptr::addr_of_mut!($var), $value); }
-    };
+bitflags! {
+    pub struct OpenFlags: u32 {
+        const RDONLY = 0;
+        const WRONLY = 1 << 0;
+        const RDWR = 1 << 1;
+        const CREATE = 1 << 9;
+        const TRUNC = 1 << 10;
+    }
 }
 
-#[macro_export]
-macro_rules! vload {
-    ($var: expr) => {
-        // unsafe { core::intrinsics::volatile_load($var_ref as *const _ as _) }
-        unsafe { core::ptr::read_volatile(core::ptr::addr_of!($var)) }
-    };
+pub fn open(path: &str, flags: OpenFlags) -> isize {
+    sys_open(path, flags.bits)
+}
+pub fn close(fd: usize) -> isize {
+    sys_close(fd)
+}
+pub fn read(fd: usize, buf: &mut [u8]) -> isize {
+    sys_read(fd, buf)
+}
+pub fn write(fd: usize, buf: &[u8]) -> isize {
+    sys_write(fd, buf)
+}
+pub fn exit(exit_code: i32) -> ! {
+    sys_exit(exit_code);
+}
+pub fn yield_() -> isize {
+    sys_yield()
+}
+pub fn get_time() -> isize {
+    sys_get_time()
+}
+pub fn getpid() -> isize {
+    sys_getpid()
+}
+pub fn fork() -> isize {
+    sys_fork()
+}
+pub fn exec(path: &str) -> isize {
+    sys_exec(path)
+}
+pub fn wait(exit_code: &mut i32) -> isize {
+    loop {
+        match sys_waitpid(-1, exit_code as *mut _) {
+            -2 => {
+                yield_();
+            }
+            // -1 or a real pid
+            exit_pid => return exit_pid,
+        }
+    }
 }
 
-#[macro_export]
-macro_rules! memory_fence {
-    () => {
-        core::sync::atomic::fence(core::sync::atomic::Ordering::SeqCst)
-    };
+pub fn waitpid(pid: usize, exit_code: &mut i32) -> isize {
+    loop {
+        match sys_waitpid(pid as isize, exit_code as *mut _) {
+            -2 => {
+                yield_();
+            }
+            // -1 or a real pid
+            exit_pid => return exit_pid,
+        }
+    }
+}
+pub fn sleep(period_ms: usize) {
+    let start = sys_get_time();
+    while sys_get_time() < start + period_ms as isize {
+        sys_yield();
+    }
 }
diff --git a/user/src/net.rs b/user/src/net.rs
deleted file mode 100644
index 78529d0..0000000
--- a/user/src/net.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-use super::*;
-
-pub fn connect(ip: u32, sport: u16, dport: u16) -> isize {
-    sys_connect(ip, sport, dport)
-}
-
-pub fn listen(sport: u16) -> isize {
-    sys_listen(sport)
-}
-
-pub fn accept(socket_fd: usize) -> isize {
-    sys_accept(socket_fd)
-}
diff --git a/user/src/sync.rs b/user/src/sync.rs
deleted file mode 100644
index 82cd2a0..0000000
--- a/user/src/sync.rs
+++ /dev/null
@@ -1,32 +0,0 @@
-use super::*;
-
-pub fn mutex_create() -> isize {
-    sys_mutex_create(false)
-}
-pub fn mutex_blocking_create() -> isize {
-    sys_mutex_create(true)
-}
-pub fn mutex_lock(mutex_id: usize) {
-    sys_mutex_lock(mutex_id);
-}
-pub fn mutex_unlock(mutex_id: usize) {
-    sys_mutex_unlock(mutex_id);
-}
-pub fn semaphore_create(res_count: usize) -> isize {
-    sys_semaphore_create(res_count)
-}
-pub fn semaphore_up(sem_id: usize) {
-    sys_semaphore_up(sem_id);
-}
-pub fn semaphore_down(sem_id: usize) {
-    sys_semaphore_down(sem_id);
-}
-pub fn condvar_create() -> isize {
-    sys_condvar_create()
-}
-pub fn condvar_signal(condvar_id: usize) {
-    sys_condvar_signal(condvar_id);
-}
-pub fn condvar_wait(condvar_id: usize, mutex_id: usize) {
-    sys_condvar_wait(condvar_id, mutex_id);
-}
diff --git a/user/src/syscall.rs b/user/src/syscall.rs
index 48b3e99..5423cce 100644
--- a/user/src/syscall.rs
+++ b/user/src/syscall.rs
@@ -1,42 +1,21 @@
-const SYSCALL_DUP: usize = 24;
-const SYSCALL_CONNECT: usize = 29;
-const SYSCALL_LISTEN: usize = 30;
-const SYSCALL_ACCEPT: usize = 31;
+use core::arch::asm;
+
 const SYSCALL_OPEN: usize = 56;
 const SYSCALL_CLOSE: usize = 57;
-const SYSCALL_PIPE: usize = 59;
 const SYSCALL_READ: usize = 63;
 const SYSCALL_WRITE: usize = 64;
 const SYSCALL_EXIT: usize = 93;
-const SYSCALL_SLEEP: usize = 101;
 const SYSCALL_YIELD: usize = 124;
-const SYSCALL_KILL: usize = 129;
 const SYSCALL_GET_TIME: usize = 169;
 const SYSCALL_GETPID: usize = 172;
 const SYSCALL_FORK: usize = 220;
 const SYSCALL_EXEC: usize = 221;
 const SYSCALL_WAITPID: usize = 260;
-const SYSCALL_THREAD_CREATE: usize = 1000;
-const SYSCALL_GETTID: usize = 1001;
-const SYSCALL_WAITTID: usize = 1002;
-const SYSCALL_MUTEX_CREATE: usize = 1010;
-const SYSCALL_MUTEX_LOCK: usize = 1011;
-const SYSCALL_MUTEX_UNLOCK: usize = 1012;
-const SYSCALL_SEMAPHORE_CREATE: usize = 1020;
-const SYSCALL_SEMAPHORE_UP: usize = 1021;
-const SYSCALL_SEMAPHORE_DOWN: usize = 1022;
-const SYSCALL_CONDVAR_CREATE: usize = 1030;
-const SYSCALL_CONDVAR_SIGNAL: usize = 1031;
-const SYSCALL_CONDVAR_WAIT: usize = 1032;
-const SYSCALL_FRAMEBUFFER: usize = 2000;
-const SYSCALL_FRAMEBUFFER_FLUSH: usize = 2001;
-const SYSCALL_EVENT_GET: usize = 3000;
-const SYSCALL_KEY_PRESSED: usize = 3001;
 
 fn syscall(id: usize, args: [usize; 3]) -> isize {
     let mut ret: isize;
     unsafe {
-        core::arch::asm!(
+        asm!(
             "ecall",
             inlateout("x10") args[0] => ret,
             in("x11") args[1],
@@ -47,26 +26,6 @@ fn syscall(id: usize, args: [usize; 3]) -> isize {
     ret
 }
 
-pub fn sys_dup(fd: usize) -> isize {
-    syscall(SYSCALL_DUP, [fd, 0, 0])
-}
-
-pub fn sys_connect(dest: u32, sport: u16, dport: u16) -> isize {
-    syscall(
-        SYSCALL_CONNECT,
-        [dest as usize, sport as usize, dport as usize],
-    )
-}
-
-// just listen for tcp connections now
-pub fn sys_listen(sport: u16) -> isize {
-    syscall(SYSCALL_LISTEN, [sport as usize, 0, 0])
-}
-
-pub fn sys_accept(socket_fd: usize) -> isize {
-    syscall(SYSCALL_ACCEPT, [socket_fd, 0, 0])
-}
-
 pub fn sys_open(path: &str, flags: u32) -> isize {
     syscall(SYSCALL_OPEN, [path.as_ptr() as usize, flags as usize, 0])
 }
@@ -75,10 +34,6 @@ pub fn sys_close(fd: usize) -> isize {
     syscall(SYSCALL_CLOSE, [fd, 0, 0])
 }
 
-pub fn sys_pipe(pipe: &mut [usize]) -> isize {
-    syscall(SYSCALL_PIPE, [pipe.as_mut_ptr() as usize, 0, 0])
-}
-
 pub fn sys_read(fd: usize, buffer: &mut [u8]) -> isize {
     syscall(
         SYSCALL_READ,
@@ -95,18 +50,10 @@ pub fn sys_exit(exit_code: i32) -> ! {
     panic!("sys_exit never returns!");
 }
 
-pub fn sys_sleep(sleep_ms: usize) -> isize {
-    syscall(SYSCALL_SLEEP, [sleep_ms, 0, 0])
-}
-
 pub fn sys_yield() -> isize {
     syscall(SYSCALL_YIELD, [0, 0, 0])
 }
 
-pub fn sys_kill(pid: usize, signal: i32) -> isize {
-    syscall(SYSCALL_KILL, [pid, signal as usize, 0])
-}
-
 pub fn sys_get_time() -> isize {
     syscall(SYSCALL_GET_TIME, [0, 0, 0])
 }
@@ -119,77 +66,10 @@ pub fn sys_fork() -> isize {
     syscall(SYSCALL_FORK, [0, 0, 0])
 }
 
-pub fn sys_exec(path: &str, args: &[*const u8]) -> isize {
-    syscall(
-        SYSCALL_EXEC,
-        [path.as_ptr() as usize, args.as_ptr() as usize, 0],
-    )
+pub fn sys_exec(path: &str) -> isize {
+    syscall(SYSCALL_EXEC, [path.as_ptr() as usize, 0, 0])
 }
 
 pub fn sys_waitpid(pid: isize, exit_code: *mut i32) -> isize {
     syscall(SYSCALL_WAITPID, [pid as usize, exit_code as usize, 0])
 }
-
-pub fn sys_thread_create(entry: usize, arg: usize) -> isize {
-    syscall(SYSCALL_THREAD_CREATE, [entry, arg, 0])
-}
-
-pub fn sys_gettid() -> isize {
-    syscall(SYSCALL_GETTID, [0; 3])
-}
-
-pub fn sys_waittid(tid: usize) -> isize {
-    syscall(SYSCALL_WAITTID, [tid, 0, 0])
-}
-
-pub fn sys_mutex_create(blocking: bool) -> isize {
-    syscall(SYSCALL_MUTEX_CREATE, [blocking as usize, 0, 0])
-}
-
-pub fn sys_mutex_lock(id: usize) -> isize {
-    syscall(SYSCALL_MUTEX_LOCK, [id, 0, 0])
-}
-
-pub fn sys_mutex_unlock(id: usize) -> isize {
-    syscall(SYSCALL_MUTEX_UNLOCK, [id, 0, 0])
-}
-
-pub fn sys_semaphore_create(res_count: usize) -> isize {
-    syscall(SYSCALL_SEMAPHORE_CREATE, [res_count, 0, 0])
-}
-
-pub fn sys_semaphore_up(sem_id: usize) -> isize {
-    syscall(SYSCALL_SEMAPHORE_UP, [sem_id, 0, 0])
-}
-
-pub fn sys_semaphore_down(sem_id: usize) -> isize {
-    syscall(SYSCALL_SEMAPHORE_DOWN, [sem_id, 0, 0])
-}
-
-pub fn sys_condvar_create() -> isize {
-    syscall(SYSCALL_CONDVAR_CREATE, [0, 0, 0])
-}
-
-pub fn sys_condvar_signal(condvar_id: usize) -> isize {
-    syscall(SYSCALL_CONDVAR_SIGNAL, [condvar_id, 0, 0])
-}
-
-pub fn sys_condvar_wait(condvar_id: usize, mutex_id: usize) -> isize {
-    syscall(SYSCALL_CONDVAR_WAIT, [condvar_id, mutex_id, 0])
-}
-
-pub fn sys_framebuffer() -> isize {
-    syscall(SYSCALL_FRAMEBUFFER, [0, 0, 0])
-}
-
-pub fn sys_framebuffer_flush() -> isize {
-    syscall(SYSCALL_FRAMEBUFFER_FLUSH, [0, 0, 0])
-}
-
-pub fn sys_event_get() -> isize {
-    syscall(SYSCALL_EVENT_GET, [0, 0, 0])
-}
-
-pub fn sys_key_pressed() -> isize {
-    syscall(SYSCALL_KEY_PRESSED, [0, 0, 0])
-}
diff --git a/user/src/task.rs b/user/src/task.rs
deleted file mode 100644
index 9e72b32..0000000
--- a/user/src/task.rs
+++ /dev/null
@@ -1,83 +0,0 @@
-use super::*;
-
-pub fn exit(exit_code: i32) -> ! {
-    sys_exit(exit_code);
-}
-pub fn yield_() -> isize {
-    sys_yield()
-}
-pub fn get_time() -> isize {
-    sys_get_time()
-}
-pub fn getpid() -> isize {
-    sys_getpid()
-}
-pub fn fork() -> isize {
-    sys_fork()
-}
-pub fn exec(path: &str, args: &[*const u8]) -> isize {
-    sys_exec(path, args)
-}
-
-pub fn wait(exit_code: &mut i32) -> isize {
-    loop {
-        match sys_waitpid(-1, exit_code as *mut _) {
-            -2 => {
-                yield_();
-            }
-            // -1 or a real pid
-            exit_pid => return exit_pid,
-        }
-    }
-}
-
-pub fn waitpid(pid: usize, exit_code: &mut i32) -> isize {
-    loop {
-        match sys_waitpid(pid as isize, exit_code as *mut _) {
-            -2 => {
-                yield_();
-            }
-            // -1 or a real pid
-            exit_pid => return exit_pid,
-        }
-    }
-}
-
-pub fn waitpid_nb(pid: usize, exit_code: &mut i32) -> isize {
-    sys_waitpid(pid as isize, exit_code as *mut _)
-}
-
-bitflags! {
-    pub struct SignalFlags: i32 {
-        const SIGINT    = 1 << 2;
-        const SIGILL    = 1 << 4;
-        const SIGABRT   = 1 << 6;
-        const SIGFPE    = 1 << 8;
-        const SIGSEGV   = 1 << 11;
-    }
-}
-
-pub fn kill(pid: usize, signal: i32) -> isize {
-    sys_kill(pid, signal)
-}
-
-pub fn sleep(sleep_ms: usize) {
-    sys_sleep(sleep_ms);
-}
-
-pub fn thread_create(entry: usize, arg: usize) -> isize {
-    sys_thread_create(entry, arg)
-}
-pub fn gettid() -> isize {
-    sys_gettid()
-}
-pub fn waittid(tid: usize) -> isize {
-    loop {
-        match sys_waittid(tid) {
-            -2 => {
-                yield_();
-            }
-            exit_code => return exit_code,
-        }
-    }
-}