noted

Author: fnnx1

os/src/main.rs

@@ -99,7 +99,7 @@ fn kernel_log_info() {
 pub fn rust_main() -> ! {
     clear_bss();
     kernel_log_info();
-    mm::init();
+    mm::init();//初始化内存，放在较前的位置
     println!("[kernel] back to world!");
     mm::remap_test();
     trap::init();

os/src/mm/address.rs

@@ -114,13 +114,14 @@ impl VirtAddr {
         self.page_offset() == 0
     }
 }
-/// 虚拟内存和虚拟页号转换
+//向下取整
 impl From<VirtAddr> for VirtPageNum {
     fn from(v: VirtAddr) -> Self {
         assert_eq!(v.page_offset(), 0);
         v.floor()
     }
 }
+//得到的是页起始地址
 impl From<VirtPageNum> for VirtAddr {
     fn from(v: VirtPageNum) -> Self {
         Self(v.0 << PAGE_SIZE_BITS)

os/src/mm/frame_allocator.rs

@@ -108,7 +108,7 @@ pub fn init_frame_allocator() {
         fn ekernel();//end of kernel, 内核结束地址
     }
     FRAME_ALLOCATOR.exclusive_access().init(
-        PhysAddr::from(ekernel as usize).ceil(),
+        PhysAddr::from(ekernel as usize).ceil(),//向上取整，返回下一页页号
         PhysAddr::from(MEMORY_END).floor(),
     );//从内核结束开始，内存末尾结束
 }
@@ -120,6 +120,7 @@ pub fn frame_alloc() -> Option<FrameTracker> {
         .alloc()
         .map(FrameTracker::new)
         //最后这行等价于.map(|x| FrameTracker::new(x))
+        //返回一个map里面new的Option<FrameTracker>
 }
 
 /// Deallocate a physical page frame with a given ppn

os/src/mm/heap_allocator.rs

@@ -4,6 +4,7 @@ use buddy_system_allocator::LockedHeap;
 
 #[global_allocator]
 /// heap allocator instance
+/// ！关键：提供给rust语言Vec等使用的动态内存分配器，可避免与frame allocator冲突
 static HEAP_ALLOCATOR: LockedHeap = LockedHeap::empty();
 
 #[alloc_error_handler]
@@ -12,13 +13,14 @@ pub fn handle_alloc_error(layout: core::alloc::Layout) -> ! {
     panic!("Heap allocation error, layout = {:?}", layout);
 }
 /// heap space ([u8; KERNEL_HEAP_SIZE])
+/// 堆空间，内核中的动态内存分配时用到
 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(HEAP_SPACE.as_ptr() as usize, KERNEL_HEAP_SIZE);//0-0x2000_0000
     }
 }
 

os/src/mm/memory_set.rs

@@ -44,7 +44,7 @@ impl MemorySet {
     pub fn new_bare() -> Self {
         Self {
             page_table: PageTable::new(),
-            areas: Vec::new(),
+            areas: Vec::new(),//理论上数据会被放在堆区，.ekernel之后
         }
     }
     /// Get the page table token
@@ -145,6 +145,7 @@ impl MemorySet {
     }
     /// Include sections in elf and trampoline and TrapContext and user stack,
     /// also returns user_sp_base and entry point.
+    /// 没有引用self，关联函数，创建一个新的MemorySet，起点和终点由程序自己决定
     pub fn from_elf(elf_data: &[u8]) -> (Self, usize, usize) {
         let mut memory_set = Self::new_bare();
         // map trampoline
@@ -156,6 +157,7 @@ impl MemorySet {
         assert_eq!(magic, [0x7f, 0x45, 0x4c, 0x46], "invalid elf!");
         let ph_count = elf_header.pt2.ph_count();
         let mut max_end_vpn = VirtPageNum(0);
+        //映射每个段
         for i in 0..ph_count {
             let ph = elf.program_header(i).unwrap();
             if ph.get_type().unwrap() == xmas_elf::program::Type::Load {
@@ -181,9 +183,11 @@ impl MemorySet {
             }
         }
         // map user stack with U flags
+        // 取的是页起始地址
         let max_end_va: VirtAddr = max_end_vpn.into();
+        // 用户栈底
         let mut user_stack_bottom: usize = max_end_va.into();
-        // guard page
+        // guard page 保证按页对齐且不出现交错（不过似乎可能留下最高4095B空隙）
         user_stack_bottom += PAGE_SIZE;
         let user_stack_top = user_stack_bottom + USER_STACK_SIZE;
         memory_set.push(
@@ -230,10 +234,12 @@ impl MemorySet {
         }
     }
     /// Translate a virtual page number to a page table entry
+    /// 虚拟页号到页表项，实际上也就是物理页号+权限信息
     pub fn translate(&self, vpn: VirtPageNum) -> Option<PageTableEntry> {
         self.page_table.translate(vpn)
     }
     /// shrink the area to new_end
+    /// 缩小某个指定起点的映射段，返回是否成功
     #[allow(unused)]
     pub fn shrink_to(&mut self, start: VirtAddr, new_end: VirtAddr) -> bool {
         if let Some(area) = self
@@ -249,6 +255,7 @@ impl MemorySet {
     }
 
     /// append the area to new_end
+    /// 扩大段，同上
     #[allow(unused)]
     pub fn append_to(&mut self, start: VirtAddr, new_end: VirtAddr) -> bool {
         if let Some(area) = self

os/src/mm/mod.rs

@@ -22,7 +22,7 @@ pub use page_table::{PTEFlags, PageTable};
 
 /// initiate heap allocator, frame allocator and kernel space
 pub fn init() {
-    heap_allocator::init_heap();
+    heap_allocator::init_heap();//先初始化堆分配器，用于进行动态内存分配
     frame_allocator::init_frame_allocator();
     KERNEL_SPACE.exclusive_access().activate();
 }