refactor(tty): enhance TTY session management and stdio initialization (DragonOS-Community#1786)

- Update TTY session checks to ensure proper session leader and controlling TTY conditions during open.
- Modify stdio initialization to prevent init process from acquiring a controlling TTY, aligning with Linux semantics.
- Add a new test case to validate behavior of tcgetpgrp without a controlling TTY.

Signed-off-by: longjin <longjin@DragonOS.org>

Author: fslongjin

kernel/src/driver/tty/tty_device.rs

@@ -280,12 +280,15 @@ impl IndexNode for TtyDevice {
         {
             let pcb = ProcessManager::current_pcb();
             let pcb_tty = pcb.sig_info_irqsave().tty();
-
-            let cond1 = pcb_tty.is_none();
-            let _cond2 = tty.core().contorl_info_irqsave().session.is_none();
-
-            // 注意！！这里为了debug,临时把cond2的判断去掉了，其实要cond1 && cond2才对
-            if cond1 {
+            let is_session_leader = pcb.sig_info_irqsave().is_session_leader;
+            let tty_session_is_none = tty.core().contorl_info_irqsave().session.is_none();
+            // Linux tty_open_proc_set_tty 语义：必须是会话首进程、尚无 controlling tty、
+            // tty 当前未被会话占用，且本次 open 具备读权限（不是 O_WRONLY）。
+            if is_session_leader
+                && pcb_tty.is_none()
+                && tty_session_is_none
+                && !mode.is_write_only()
+            {
                 TtyJobCtrlManager::proc_set_tty(tty);
             }
         }

kernel/src/driver/tty/tty_job_control.rs

@@ -47,6 +47,7 @@ impl TtyJobCtrlManager {
     pub fn remove_session_tty(tty: &Arc<TtyCore>) {
         let mut ctrl = tty.core().contorl_info_irqsave();
         ctrl.session = None;
+        ctrl.pgid = None;
     }
 
     /// ### 检查tty
@@ -176,9 +177,8 @@ impl TtyJobCtrlManager {
     fn tiocgpgrp(real_tty: Arc<TtyCore>, arg: usize) -> Result<usize, SystemError> {
         // log::debug!("job_ctrl_ioctl: TIOCGPGRP");
         let current = ProcessManager::current_pcb();
-        if current.sig_info_irqsave().tty().is_some()
-            && !Arc::ptr_eq(&current.sig_info_irqsave().tty().unwrap(), &real_tty)
-        {
+        let current_tty = current.sig_info_irqsave().tty();
+        if current_tty.is_none() || !Arc::ptr_eq(&current_tty.unwrap(), &real_tty) {
             return Err(SystemError::ENOTTY);
         }
 
@@ -200,9 +200,8 @@ impl TtyJobCtrlManager {
     fn tiocgsid(real_tty: Arc<TtyCore>, arg: usize) -> Result<usize, SystemError> {
         // log::debug!("job_ctrl_ioctl: TIOCGSID");
         let current = ProcessManager::current_pcb();
-        if current.sig_info_irqsave().tty().is_some()
-            && !Arc::ptr_eq(&current.sig_info_irqsave().tty().unwrap(), &real_tty)
-        {
+        let current_tty = current.sig_info_irqsave().tty();
+        if current_tty.is_none() || !Arc::ptr_eq(&current_tty.unwrap(), &real_tty) {
             return Err(SystemError::ENOTTY);
         }
 

kernel/src/process/stdio.rs

@@ -22,12 +22,17 @@ pub fn stdio_init() -> Result<(), SystemError> {
         .lookup(&tty_path)
         .unwrap_or_else(|_| panic!("Init stdio: can't find {}", tty_path));
 
-    let stdin =
-        File::new(tty_inode.clone(), FileFlags::O_RDONLY).expect("Init stdio: can't create stdin");
-    let stdout =
-        File::new(tty_inode.clone(), FileFlags::O_WRONLY).expect("Init stdio: can't create stdout");
-    let stderr = File::new(tty_inode.clone(), FileFlags::O_WRONLY | FileFlags::O_SYNC)
-        .expect("Init stdio: can't create stderr");
+    // Linux 语义对齐：init(pid=1) 的早期 stdio 绑定不应自动获得 controlling tty。
+    // 否则会占住 tty session，影响后续用户态会话通过 TIOCSCTTY 建立控制终端。
+    let stdin = File::new(tty_inode.clone(), FileFlags::O_RDONLY | FileFlags::O_NOCTTY)
+        .expect("Init stdio: can't create stdin");
+    let stdout = File::new(tty_inode.clone(), FileFlags::O_WRONLY | FileFlags::O_NOCTTY)
+        .expect("Init stdio: can't create stdout");
+    let stderr = File::new(
+        tty_inode.clone(),
+        FileFlags::O_WRONLY | FileFlags::O_SYNC | FileFlags::O_NOCTTY,
+    )
+    .expect("Init stdio: can't create stderr");
 
     /*
        按照规定，进程的文件描述符数组的前三个位置，分别是stdin, stdout, stderr

user/apps/c_unitest/test_tcgetpgrp_no_ctty.c

@@ -0,0 +1,50 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+int main(void) {
+  if (!isatty(STDIN_FILENO)) {
+    printf("[SKIP] stdin is not a tty, skip tcgetpgrp no-ctty test\n");
+    return 0;
+  }
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    perror("fork");
+    return 1;
+  }
+
+  if (pid == 0) {
+    if (setsid() < 0) {
+      perror("setsid");
+      _exit(2);
+    }
+
+    errno = 0;
+    pid_t pgrp = tcgetpgrp(STDIN_FILENO);
+    if (pgrp == -1 && errno == ENOTTY) {
+      printf("[PASS] tcgetpgrp without controlling tty returns ENOTTY\n");
+      _exit(0);
+    }
+
+    fprintf(stderr,
+            "[FAIL] tcgetpgrp without controlling tty: ret=%d errno=%d\n",
+            (int)pgrp, errno);
+    _exit(3);
+  }
+
+  int status = 0;
+  if (waitpid(pid, &status, 0) < 0) {
+    perror("waitpid");
+    return 1;
+  }
+
+  if (WIFEXITED(status)) {
+    return WEXITSTATUS(status);
+  }
+
+  fprintf(stderr, "[FAIL] child did not exit normally\n");
+  return 1;
+}

user/sysconfig/etc/inittab

@@ -1,7 +1,7 @@
 # /etc/inittab
 ::sysinit:busybox sh /etc/init.d/rcS  # 系统初始化脚本
 
-::askfirst:/bin/busybox login -f root
+::askfirst:-/bin/busybox login -f root
 
 # /etc/inittab - 根据源码弄出来的默认inittab
 # https://code.dragonos.org.cn/xref/busybox-1.35.0/init/init.c#679