From 73fcb72cbbd17f342bd52f413dc803061aa3535d Mon Sep 17 00:00:00 2001
From: Yu Chen <yuchen@mail.tsinghua.edu.cn>
Date: Tue, 10 Jan 2023 16:29:36 +0800
Subject: [PATCH] fix bug in impl Drop for FrameTracker, for the correctly
 mapping/unmapping display buffer in app

---
 os/src/mm/frame_allocator.rs | 10 +++++++---
 os/src/mm/memory_set.rs      |  6 +++++-
 os/src/syscall/gui.rs        |  2 +-
 user/src/bin/gui_rect.rs     |  1 +
 user/src/bin/gui_snake.rs    |  1 +
 user/src/bin/gui_uart.rs     |  1 +
 6 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/os/src/mm/frame_allocator.rs b/os/src/mm/frame_allocator.rs
index a280379..275fb17 100644
--- a/os/src/mm/frame_allocator.rs
+++ b/os/src/mm/frame_allocator.rs
@@ -7,6 +7,7 @@ use lazy_static::*;
 
 pub struct FrameTracker {
     pub ppn: PhysPageNum,
+    pub nodrop: bool,
 }
 
 impl FrameTracker {
@@ -16,10 +17,10 @@ impl FrameTracker {
         for i in bytes_array {
             *i = 0;
         }
-        Self { ppn }
+        Self { ppn, nodrop: false }
     }
-    pub fn new_nowrite(ppn: PhysPageNum) -> Self {
-        Self { ppn }
+    pub fn new_noalloc(ppn: PhysPageNum) -> Self {
+        Self { ppn, nodrop: true }
     }
 }
 
@@ -31,6 +32,9 @@ impl Debug for FrameTracker {
 
 impl Drop for FrameTracker {
     fn drop(&mut self) {
+        if self.nodrop {
+            return;
+        }
         frame_dealloc(self.ppn);
     }
 }
diff --git a/os/src/mm/memory_set.rs b/os/src/mm/memory_set.rs
index 8875617..bec0b93 100644
--- a/os/src/mm/memory_set.rs
+++ b/os/src/mm/memory_set.rs
@@ -290,6 +290,9 @@ impl MapArea {
                 ppn = frame.ppn;
                 self.data_frames.insert(vpn, frame);
             }
+            MapType::Noalloc => {
+                panic!("Noalloc should not be mapped");
+            }
         }
         let pte_flags = PTEFlags::from_bits(self.map_perm.bits).unwrap();
         page_table.map(vpn, ppn, pte_flags);
@@ -307,7 +310,7 @@ impl MapArea {
     }
     pub fn map_noalloc(&mut self, page_table: &mut PageTable,ppn_range:PPNRange) {
         for (vpn,ppn) in core::iter::zip(self.vpn_range,ppn_range) {
-            self.data_frames.insert(vpn, FrameTracker::new_nowrite(ppn));
+            self.data_frames.insert(vpn, FrameTracker::new_noalloc(ppn));
             let pte_flags = PTEFlags::from_bits(self.map_perm.bits).unwrap();
             page_table.map(vpn, ppn, pte_flags);
         }
@@ -346,6 +349,7 @@ impl MapArea {
 pub enum MapType {
     Identical,
     Framed,
+    Noalloc,
 }
 
 bitflags! {
diff --git a/os/src/syscall/gui.rs b/os/src/syscall/gui.rs
index 0018604..5d41c0c 100644
--- a/os/src/syscall/gui.rs
+++ b/os/src/syscall/gui.rs
@@ -22,7 +22,7 @@ pub fn sys_framebuffer() -> isize {
         MapArea::new(
             (FB_VADDR as usize).into(),
             (FB_VADDR + len as usize).into(),
-            MapType::Framed,
+            MapType::Noalloc,
             MapPermission::R | MapPermission::W | MapPermission::U,
         ),
         PPNRange::new(fb_ppn, fb_end_ppn),
diff --git a/user/src/bin/gui_rect.rs b/user/src/bin/gui_rect.rs
index e1b3ea8..e9007f6 100644
--- a/user/src/bin/gui_rect.rs
+++ b/user/src/bin/gui_rect.rs
@@ -108,6 +108,7 @@ impl DrawingBoard {
 pub fn main() -> i32 {
     // let fb_ptr = framebuffer() as *mut u8;
     let mut board = DrawingBoard::new();
+    let _ = board.disp.clear(Rgb888::BLACK).unwrap();
     for i in 0..20 {
         board.latest_pos.x += i;
         board.latest_pos.y += i;
diff --git a/user/src/bin/gui_snake.rs b/user/src/bin/gui_snake.rs
index c014872..ce36b2e 100644
--- a/user/src/bin/gui_snake.rs
+++ b/user/src/bin/gui_snake.rs
@@ -382,6 +382,7 @@ const CR: u8 = 0x0du8;
 pub fn main() -> i32 {
     let mut disp = Display::new(Size::new(1280, 800), Point::new(0, 0));
     let mut game = SnakeGame::<20, Rgb888>::new(1280, 800, 20, 20, Rgb888::RED, Rgb888::YELLOW, 50);
+    let _ = disp.clear(Rgb888::BLACK).unwrap();
     loop {
         if key_pressed() {
             let c = getchar();
diff --git a/user/src/bin/gui_uart.rs b/user/src/bin/gui_uart.rs
index 9e0933b..c9577a4 100644
--- a/user/src/bin/gui_uart.rs
+++ b/user/src/bin/gui_uart.rs
@@ -111,6 +111,7 @@ const CR: u8 = 0x0du8;
 pub fn main() -> i32 {
     // let fb_ptr = framebuffer() as *mut u8;
     let mut board = DrawingBoard::new();
+    let _ = board.disp.clear(Rgb888::BLACK).unwrap();
     for i in 0..20 {
         let c=getchar();
         if c == LF || c == CR {