feat: impl sys_munmap

Author: flappyBug

os/src/mm/memory_set.rs

@@ -262,6 +262,25 @@ impl MemorySet {
             false
         }
     }
+
+    /// Remove a MapArea that exactly matches [start_va, end_va)
+    /// Returns true if successfully removed, false if not found or range doesn't match exactly
+    pub fn remove_area_with_range(&mut self, start_va: VirtAddr, end_va: VirtAddr) -> bool {
+        let start_vpn = start_va.floor();
+        let end_vpn = end_va.ceil();
+
+        // Find the area that exactly matches this range
+        if let Some(idx) = self.areas.iter().position(|area| {
+            area.vpn_range.get_start() == start_vpn && area.vpn_range.get_end() == end_vpn
+        }) {
+            // Remove the area and unmap it
+            let mut area = self.areas.remove(idx);
+            area.unmap(&mut self.page_table);
+            true
+        } else {
+            false
+        }
+    }
 }
 /// map area structure, controls a contiguous piece of virtual memory
 pub struct MapArea {

os/src/syscall/process.rs

@@ -160,10 +160,37 @@ pub fn sys_mmap(start: usize, len: usize, prot: usize) -> isize {
     }
 }
 
-// YOUR JOB: Implement munmap.
-pub fn sys_munmap(_start: usize, _len: usize) -> isize {
-    trace!("kernel: sys_munmap NOT IMPLEMENTED YET!");
-    -1
+/// 取消到 [start, start + len) 虚存的映射
+/// 参数和返回值请参考 mmap
+/// 为了简单，参数错误时不考虑内存的恢复和回收。
+/// 可能的错误：
+/// - [start, start + len) 中存在未被映射的虚存。
+/// - [start, start + len) 和调用mmap时提供的不一致
+/// - [start, start + len) 中存在未被映射的虚存。
+pub fn sys_munmap(start: usize, len: usize) -> isize {
+    trace!("kernel: sys_munmap start={:#x}, len={:#x}", start, len);
+
+    // 检查 len 为 0 的情况
+    if len == 0 {
+        return 0;
+    }
+
+    let start_va = crate::mm::VirtAddr::from(start);
+
+    let end_va = crate::mm::VirtAddr::from(start + len);
+
+    // 调用新的接口来取消映射
+    if crate::task::munmap_for_current_task(start_va, end_va) {
+        trace!(
+            "sys_munmap: successfully unmapped [{:#x}, {:#x})",
+            start,
+            start + len
+        );
+        0
+    } else {
+        trace!("sys_munmap: failed to unmap, address range not fully mapped");
+        -1
+    }
 }
 
 /// change data segment size

os/src/task/mod.rs

@@ -190,6 +190,29 @@ impl TaskManager {
         memory_set.insert_framed_area(start_va, end_va, map_perm);
         true
     }
+
+    /// Unmap memory area for the current task
+    fn munmap_for_current_task(
+        &self,
+        start_va: crate::mm::VirtAddr,
+        end_va: crate::mm::VirtAddr,
+    ) -> bool {
+        let mut inner = self.inner.exclusive_access();
+        let current = inner.current_task;
+        let memory_set = &mut inner.tasks[current].memory_set;
+
+        // 检查地址范围是否完全被映射
+        let start_vpn = start_va.floor();
+        let end_vpn = end_va.ceil();
+        for vpn in crate::mm::VPNRange::new(start_vpn, end_vpn) {
+            if memory_set.translate(vpn).is_none() {
+                return false; // 有未映射的页
+            }
+        }
+
+        // 移除对应的 MapArea
+        memory_set.remove_area_with_range(start_va, end_va)
+    }
 }
 
 /// Run the first task in task list.
@@ -258,3 +281,13 @@ pub fn mmap_for_current_task(
 ) -> bool {
     TASK_MANAGER.mmap_for_current_task(start_va, end_va, map_perm)
 }
+
+/// Unmap memory area for the current task
+pub fn munmap_for_current_task(
+    start_va: crate::mm::VirtAddr,
+    end_va: crate::mm::VirtAddr,
+) -> bool {
+    TASK_MANAGER.munmap_for_current_task(start_va, end_va)
+}
+
+