fix(process): align wait and ptrace child semantics

kernel/src/ipc/sighand.rs

@@ -291,6 +291,17 @@ impl SigHand {
         g.flags.remove(flag);
     }
 
+    pub fn flags_test_and_clear(&self, flag: SignalFlags, clear: bool) -> bool {
+        let mut g = self.inner_mut();
+        if !g.flags.contains(flag) {
+            return false;
+        }
+        if clear {
+            g.flags.remove(flag);
+        }
+        true
+    }
+
     pub fn stop_signal(&self) -> Signal {
         self.inner().stop_signal
     }
@@ -450,11 +461,11 @@ fn default_sighandlers() -> Vec<Sigaction> {
     let mut r = vec![Sigaction::default(); MAX_SIG_NUM];
     let mut sig_ign = Sigaction::default();
     // 收到忽略的信号，重启系统调用
-    // Linux 对 SIGCHLD/SIGURG/SIGWINCH 默认忽略；这里显式设置 Ignore
+    // Linux ignores SIGURG/SIGWINCH by default; SIGCHLD is also ignored by default,
+    // but the handler must remain SIG_DFL to distinguish default ignore from explicit SIG_IGN.
     sig_ign.set_action(SigactionType::SaHandler(SaHandlerType::Ignore));
     sig_ign.flags_mut().insert(SigFlags::SA_RESTART);
 
-    r[Signal::SIGCHLD as usize - 1] = sig_ign;
     r[Signal::SIGURG as usize - 1] = sig_ign;
     r[Signal::SIGWINCH as usize - 1] = sig_ign;
 

kernel/src/ipc/syscall/sys_kill.rs

@@ -31,7 +31,7 @@ pub enum PidConverter {
 }
 
 impl PidConverter {
-    /// ### 为 `wait` 和 `kill` 调用使用
+    /// ### For `kill` syscall use
     pub fn from_id(id: i32) -> Option<Self> {
         if id < -1 {
             let pgid = ProcessManager::find_vpid(RawPid::from(-id as usize));
@@ -46,33 +46,6 @@ impl PidConverter {
             Some(PidConverter::Pid(pid))
         }
     }
-
-    /// ### 为 `waitid` 使用：which/upid 已在封装层基本校验
-    /// 约定：which: 0=P_ALL, 1=P_PID(id>0), 2=P_PGID(id>=0; 0=当前组)
-    pub fn from_waitid(which: u32, upid: i32) -> Option<Self> {
-        match which {
-            0 => Some(PidConverter::All),
-            1 => {
-                if upid <= 0 {
-                    return None;
-                }
-                Self::from_id(upid)
-            }
-            2 => {
-                if upid < 0 {
-                    return None;
-                }
-                // P_PGID: upid==0 -> 当前进程组；>0 -> 指定pgid
-                // from_id: id< -1 为 pgid，因此这里将正 pgid 映射为负数传入
-                if upid == 0 {
-                    Self::from_id(0)
-                } else {
-                    Self::from_id(-upid)
-                }
-            }
-            _ => None,
-        }
-    }
 }
 
 /// Check if the current process has permission to send a signal to the target process.