完善用户栈的字节对齐机制

MemoryShore · Aug 30, 2024 · 6c4958b · 6c4958b
1 parent 2207c1c
commit 6c4958b
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Showing 2 changed files with 12 additions and 15 deletions.
diff --git a/kernel/src/arch/x86_64/process/syscall.rs b/kernel/src/arch/x86_64/process/syscall.rs
@@ -74,7 +74,7 @@ impl Syscall {
 
         // 生成16字节随机数
         // TODO 暂时设为0
-        param.init_info_mut().rand_num = 0;
+        param.init_info_mut().rand_num = [0u8; 16];
 
         // 把proc_init_info写到用户栈上
         let mut ustack_message = unsafe {
@@ -87,13 +87,7 @@ impl Syscall {
         let (user_sp, argv_ptr) = unsafe {
             param
                 .init_info_mut()
-                .push_at(
-                    // address_space
-                    //     .write()
-                    //     .user_stack_mut()
-                    //     .expect("No user stack found"),
-                    &mut ustack_message,
-                )
+                .push_at(&mut ustack_message)
                 .expect("Failed to push proc_init_info to user stack")
         };
         address_space.write().user_stack = Some(ustack_message);

diff --git a/kernel/src/process/exec.rs b/kernel/src/process/exec.rs
@@ -206,7 +206,7 @@ pub struct ProcInitInfo {
     pub args: Vec<CString>,
     pub envs: Vec<CString>,
     pub auxv: BTreeMap<u8, usize>,
-    pub rand_num: u128,
+    pub rand_num: [u8; 16],
 }
 
 impl ProcInitInfo {
@@ -216,7 +216,7 @@ impl ProcInitInfo {
             args: Vec::new(),
             envs: Vec::new(),
             auxv: BTreeMap::new(),
-            rand_num: 0,
+            rand_num: [0u8; 16],
         }
     }
 
@@ -258,11 +258,14 @@ impl ProcInitInfo {
         self.auxv
             .insert(super::abi::AtType::Random as u8, ustack.sp().data());
 
-        // 实现栈的16字节对齐，如果argv、envp、argc在栈中的长度加起来不能对齐16字节，则手动填充一个空字节
-        // TODO 感觉这样对齐有点简陋，后续可能要完善一下
-        if (envps.len() + argps.len() + 1) * core::mem::align_of::<usize>() % 0x10 != 0 {
-            self.push_slice(ustack, &[0u8; 1])?;
-        }
+        // 实现栈的16字节对齐
+        // 用当前栈顶地址减去后续要压栈的长度，得到的压栈后的栈顶地址与0xF按位与操作得到对齐要填充的字节数
+        let length_to_push = (self.auxv.len() + envps.len() + 1 + argps.len() + 1 + 1)
+            * core::mem::align_of::<usize>();
+        self.push_slice(
+            ustack,
+            &vec![0u8; (ustack.sp().data() - length_to_push) & 0xF],
+        )?;
 
         // 压入auxv
         self.push_slice(ustack, &[null::<u8>(), null::<u8>()])?;