Merge updates from ch7

os/src/mm/address.rs

@@ -115,6 +115,11 @@ impl VirtPageNum {
 }
 
 impl PhysAddr {
+    pub fn get_ref<T>(&self) -> &'static T {
+        unsafe {
+            (self.0 as *const T).as_ref().unwrap()
+        }
+    }
     pub fn get_mut<T>(&self) -> &'static mut T {
         unsafe {
             (self.0 as *mut T).as_mut().unwrap()

os/src/mm/mod.rs

@@ -13,6 +13,7 @@ pub use page_table::{
     PageTableEntry,
     translated_byte_buffer,
     translated_str,
+    translated_ref,
     translated_refmut,
     UserBuffer,
     UserBufferIterator,

os/src/mm/page_table.rs

@@ -174,6 +174,7 @@ 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`.
 pub fn translated_str(token: usize, ptr: *const u8) -> String {
     let page_table = PageTable::from_token(token);
     let mut string = String::new();
@@ -182,14 +183,18 @@ pub fn translated_str(token: usize, ptr: *const u8) -> String {
         let ch: u8 = *(page_table.translate_va(VirtAddr::from(va)).unwrap().get_mut());
         if ch == 0 {
             break;
-        } else {
-            string.push(ch as char);
-            va += 1;
         }
+        string.push(ch as char);
+        va += 1;
     }
     string
 }
 
+pub fn translated_ref<T>(token: usize, ptr: *const T) -> &'static T {
+    let page_table = PageTable::from_token(token);
+    page_table.translate_va(VirtAddr::from(ptr as usize)).unwrap().get_ref()
+}
+
 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;