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The following commit(s) were added to refs/heads/master by this push:
new 95063bde157 drivers/serial: add job-control TTY ioctls and libc
wrappers
95063bde157 is described below
commit 95063bde1571673eafeb7fecef132474d24ce68a
Author: Xiang Xiao <[email protected]>
AuthorDate: Sun Jun 21 10:38:30 2026 +0800
drivers/serial: add job-control TTY ioctls and libc wrappers
NuttX has no real session/process-group abstraction, so the TTY layer
collapses the foreground process group onto the single dev->pid field
(pgrp == pid, one member per group). Extend the controlling-terminal
support so portable software (e.g. dropbear, socat) that relies on
job-control primitives works without losing the existing NuttX-specific
behaviour.
Driver (serial.c, pty.c):
- TIOCSCTTY now accepts a flag: arg > 0 keeps the historical "target
PID in arg" semantics (NSH registers the foreground command it just
spawned), while arg == 0 selects the calling task via
nxsched_getpid(), matching the POSIX flag convention used by
dropbear/socat/apue. This preserves all existing callers and makes
the previously-dead arg==0 path deliver SIGINT correctly.
- Add TIOCGPGRP/TIOCGSID (return dev->pid) and TIOCSPGRP (set it).
- pty.c gains the same handlers against pd_pid and includes
nuttx/sched.h for nxsched_getpid().
ioctl numbers (tioctl.h): TIOCGPGRP/TIOCSPGRP/TIOCGSID at 0x37-0x39.
libc wrappers:
- termios: tcgetpgrp(), tcsetpgrp(), tcgetsid() over the new ioctls.
- unistd: setsid()/getsid()/setpgid() stubs consistent with the
existing getpgrp()/getpgid() single-session model (sid == pgid ==
pid; setpgid only succeeds for pgid == pid).
Declare the new prototypes in unistd.h (tcgetsid was already in
termios.h) and register all sources in the Make.defs/CMakeLists.
Group-broadcast signalling (kill(-pgrp)) remains unsupported, so
tty signals still target the single dev->pid; a real session/process
group model is left as a follow-up.
Signed-off-by: Xiang Xiao <[email protected]>
---
.../components/drivers/character/serial.rst | 28 +++++++
drivers/serial/pty.c | 29 +++++++-
drivers/serial/serial.c | 35 ++++++++-
include/nuttx/serial/serial.h | 5 +-
include/nuttx/serial/tioctl.h | 8 +-
include/unistd.h | 5 ++
libs/libc/termios/CMakeLists.txt | 5 +-
libs/libc/termios/Make.defs | 1 +
libs/libc/termios/lib_tcgetpgrp.c | 67 +++++++++++++++++
libs/libc/termios/lib_tcgetsid.c | 67 +++++++++++++++++
libs/libc/termios/lib_tcsetpgrp.c | 59 +++++++++++++++
libs/libc/unistd/CMakeLists.txt | 3 +
libs/libc/unistd/Make.defs | 1 +
libs/libc/unistd/lib_getsid.c | 75 +++++++++++++++++++
libs/libc/unistd/lib_setpgid.c | 87 ++++++++++++++++++++++
libs/libc/unistd/lib_setsid.c | 57 ++++++++++++++
16 files changed, 523 insertions(+), 9 deletions(-)
diff --git a/Documentation/components/drivers/character/serial.rst
b/Documentation/components/drivers/character/serial.rst
index 7af619f1270..3b80938ba7c 100644
--- a/Documentation/components/drivers/character/serial.rst
+++ b/Documentation/components/drivers/character/serial.rst
@@ -35,6 +35,34 @@ Serial Device Drivers
Also, you can customize:
``TTY_LAUNCH_ARGS`` ``TTY_LAUNCH_PRIORITY`` ``TTY_LAUNCH_STACKSIZE``
+- **Job control / controlling terminal**. When ``CONFIG_TTY_SIGINT``
+ or ``CONFIG_TTY_SIGTSTP`` is enabled, the TTY layer can generate
+ ``SIGINT`` (Ctrl-C) and ``SIGTSTP`` (Ctrl-Z) for a foreground task.
+ NuttX does not implement POSIX sessions or process groups, so the
+ foreground process group is collapsed onto a single PID stored in
+ the driver (``pgrp == pid``, one member per group); the signal is
+ delivered with ``nxsig_kill(pid, signo)``.
+
+ The following terminal ``ioctl`` commands manage this PID:
+
+ - ``TIOCSCTTY`` makes the terminal the controlling terminal. The
+ ``arg`` is treated as a flag: a value of ``0`` selects the
+ calling task (the POSIX convention used by, e.g., dropbear and
+ socat), while a positive value is honored as the target PID (the
+ NuttX convention used by NSH to register a foreground command it
+ has just spawned).
+ - ``TIOCNOTTY`` gives up the controlling terminal.
+ - ``TIOCGPGRP`` / ``TIOCGSID`` return the foreground process group /
+ session leader PID.
+ - ``TIOCSPGRP`` sets the foreground process group PID (a value of
+ ``0`` selects the calling task).
+
+ The C library exposes these through ``tcgetpgrp()``, ``tcsetpgrp()``,
+ ``tcgetsid()``, ``setsid()``, ``getsid()`` and ``setpgid()``. Because
+ sending a signal to a process group (``kill(-pgrp, signo)``) is not
+ supported, TTY signals always target the single foreground PID rather
+ than an entire group.
+
- **User Access**. Serial drivers are, ultimately, normal
`character drivers <#chardrivers>`__ and are accessed as other
character drivers.
diff --git a/drivers/serial/pty.c b/drivers/serial/pty.c
index bcefb1672fe..070e82980fb 100644
--- a/drivers/serial/pty.c
+++ b/drivers/serial/pty.c
@@ -43,6 +43,7 @@
#include <nuttx/ascii.h>
#include <nuttx/kmalloc.h>
#include <nuttx/mutex.h>
+#include <nuttx/sched.h>
#include <nuttx/semaphore.h>
#include <nuttx/fs/fs.h>
#include <nuttx/serial/pty.h>
@@ -838,16 +839,21 @@ static int pty_ioctl(FAR struct file *filep, int cmd,
unsigned long arg)
/* Make the controlling terminal of the calling process */
case TIOCSCTTY:
+ case TIOCSPGRP:
{
- /* Save the PID of the recipient of the SIGINT signal. */
+ /* Save the PID of the foreground process group that is to receive
+ * tty-generated signals. A zero 'arg' selects the calling task
+ * (POSIX flag semantics); a positive 'arg' is honored as the
+ * target PID (NuttX historical semantics).
+ */
- if ((int)arg < 0 || dev->pd_pid >= 0)
+ if ((int)arg < 0)
{
ret = -EINVAL;
}
else
{
- dev->pd_pid = (pid_t)arg;
+ dev->pd_pid = arg > 0 ? (pid_t)arg : nxsched_getpid();
ret = 0;
}
}
@@ -859,6 +865,23 @@ static int pty_ioctl(FAR struct file *filep, int cmd,
unsigned long arg)
ret = 0;
}
break;
+
+ /* Get the foreground process group / session leader. pgrp == pid. */
+
+ case TIOCGPGRP:
+ case TIOCGSID:
+ {
+ if (dev->pd_pid < 0)
+ {
+ ret = -ENOTTY;
+ }
+ else
+ {
+ *(FAR pid_t *)((uintptr_t)arg) = dev->pd_pid;
+ ret = 0;
+ }
+ }
+ break;
#endif
/* Any unrecognized IOCTL commands will be passed to the contained
diff --git a/drivers/serial/serial.c b/drivers/serial/serial.c
index a30fdcaa2fe..5f54d972a98 100644
--- a/drivers/serial/serial.c
+++ b/drivers/serial/serial.c
@@ -1749,16 +1749,25 @@ static int uart_ioctl(FAR struct file *filep, int cmd,
unsigned long arg)
/* Make the controlling terminal of the calling process */
case TIOCSCTTY:
+ case TIOCSPGRP:
{
- /* Save the PID of the recipient of the SIGINT signal. */
+ /* Save the PID of the foreground process group that is to
+ * receive tty-generated signals (SIGINT/SIGTSTP).
+ *
+ * POSIX passes a flag in 'arg' and uses the caller's PID, so
+ * a zero 'arg' selects the calling task. NuttX historically
+ * passes the target PID directly in 'arg' (e.g. NSH registers
+ * the foreground command it just spawned), so a positive
+ * 'arg' is honored as the target PID.
+ */
- if ((int)arg < 0 || dev->pid >= 0)
+ if ((int)arg < 0)
{
ret = -EINVAL;
}
else
{
- dev->pid = (pid_t)arg;
+ dev->pid = arg > 0 ? (pid_t)arg : nxsched_getpid();
ret = 0;
}
}
@@ -1770,6 +1779,26 @@ static int uart_ioctl(FAR struct file *filep, int cmd,
unsigned long arg)
ret = 0;
}
break;
+
+ /* Get the foreground process group. Since NuttX has no real
+ * process-group abstraction, the controlling task's PID doubles
+ * as the (single-member) foreground process group.
+ */
+
+ case TIOCGPGRP:
+ case TIOCGSID:
+ {
+ if (dev->pid < 0)
+ {
+ ret = -ENOTTY;
+ }
+ else
+ {
+ *(FAR pid_t *)((uintptr_t)arg) = dev->pid;
+ ret = 0;
+ }
+ }
+ break;
#endif
}
}
diff --git a/include/nuttx/serial/serial.h b/include/nuttx/serial/serial.h
index 57eb81492f2..ee82a927e17 100644
--- a/include/nuttx/serial/serial.h
+++ b/include/nuttx/serial/serial.h
@@ -335,7 +335,10 @@ struct uart_dev_s
#if defined(CONFIG_TTY_SIGINT) || defined(CONFIG_TTY_SIGTSTP) || \
defined(CONFIG_TTY_FORCE_PANIC) || defined(CONFIG_TTY_LAUNCH)
- pid_t pid; /* Thread PID to receive signals (-1 if
none) */
+ pid_t pid; /* Foreground process group /
controlling-tty
+ * owner that receives tty signals. With
no
+ * process-group support, pgrp == pid.
+ * (-1 if none) */
#endif
#ifdef CONFIG_TTY_FORCE_PANIC
diff --git a/include/nuttx/serial/tioctl.h b/include/nuttx/serial/tioctl.h
index 5ab751ffa32..b93c28c11ee 100644
--- a/include/nuttx/serial/tioctl.h
+++ b/include/nuttx/serial/tioctl.h
@@ -87,7 +87,7 @@
/* Controlling TTY */
-#define TIOCSCTTY _TIOC(0x0018) /* Make controlling TTY: int */
+#define TIOCSCTTY _TIOC(0x0018) /* Make controlling TTY: int (0 ==
caller) */
#define TIOCNOTTY _TIOC(0x0019) /* Give up controllinog TTY: void */
/* Exclusive mode */
@@ -200,6 +200,12 @@
#define SER_SWAP_ENABLED (1 << 0) /* Enable/disable RX/TX swap */
+/* Process group / session (job control) */
+
+#define TIOCGPGRP _TIOC(0x0037) /* Get foreground process group: FAR
pid_t* */
+#define TIOCSPGRP _TIOC(0x0038) /* Set foreground process group: FAR
const pid_t* */
+#define TIOCGSID _TIOC(0x0039) /* Get session leader: FAR pid_t* */
+
/****************************************************************************
* Public Type Definitions
****************************************************************************/
diff --git a/include/unistd.h b/include/unistd.h
index acfc0e0bb48..6c7f7d1bcf3 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -354,6 +354,11 @@ pid_t getpgid(pid_t pid);
pid_t getpgrp(void);
pid_t gettid(void);
pid_t getppid(void);
+pid_t getsid(pid_t pid);
+int setpgid(pid_t pid, pid_t pgid);
+pid_t setsid(void);
+pid_t tcgetpgrp(int fd);
+int tcsetpgrp(int fd, pid_t pgrp);
void _exit(int status) noreturn_function;
unsigned int sleep(unsigned int seconds);
int usleep(useconds_t usec);
diff --git a/libs/libc/termios/CMakeLists.txt b/libs/libc/termios/CMakeLists.txt
index 71b73819174..2f5a0e11c45 100644
--- a/libs/libc/termios/CMakeLists.txt
+++ b/libs/libc/termios/CMakeLists.txt
@@ -32,4 +32,7 @@ target_sources(
lib_tcsetattr.c
lib_tcsendbreak.c
lib_ttyname.c
- lib_ttynamer.c)
+ lib_ttynamer.c
+ lib_tcgetpgrp.c
+ lib_tcsetpgrp.c
+ lib_tcgetsid.c)
diff --git a/libs/libc/termios/Make.defs b/libs/libc/termios/Make.defs
index 3cf99568ac8..68546b82af3 100644
--- a/libs/libc/termios/Make.defs
+++ b/libs/libc/termios/Make.defs
@@ -25,6 +25,7 @@
CSRCS += lib_cfspeed.c lib_cfmakeraw.c lib_isatty.c lib_tcflush.c
CSRCS += lib_tcdrain.c lib_tcflow.c lib_tcgetattr.c lib_tcsetattr.c
CSRCS += lib_tcsendbreak.c lib_ttyname.c lib_ttynamer.c
+CSRCS += lib_tcgetpgrp.c lib_tcsetpgrp.c lib_tcgetsid.c
# Add the termios directory to the build
diff --git a/libs/libc/termios/lib_tcgetpgrp.c
b/libs/libc/termios/lib_tcgetpgrp.c
new file mode 100644
index 00000000000..f85ec57e0bb
--- /dev/null
+++ b/libs/libc/termios/lib_tcgetpgrp.c
@@ -0,0 +1,67 @@
+/****************************************************************************
+ * libs/libc/termios/lib_tcgetpgrp.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/ioctl.h>
+
+#include <unistd.h>
+
+#include <nuttx/serial/tioctl.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: tcgetpgrp
+ *
+ * Description:
+ * Return the value of the process group ID of the foreground process
+ * group associated with the terminal.
+ *
+ * Input Parameters:
+ * fd - The 'fd' argument is an open file descriptor associated with a
+ * terminal.
+ *
+ * Returned Value:
+ * Upon successful completion, the process group ID of the foreground
+ * process group is returned. Otherwise, (pid_t)-1 is returned and errno
+ * is set to indicate the error.
+ *
+ ****************************************************************************/
+
+pid_t tcgetpgrp(int fd)
+{
+ pid_t pgrp;
+
+ if (ioctl(fd, TIOCGPGRP, &pgrp) < 0)
+ {
+ return (pid_t)-1;
+ }
+
+ return pgrp;
+}
diff --git a/libs/libc/termios/lib_tcgetsid.c b/libs/libc/termios/lib_tcgetsid.c
new file mode 100644
index 00000000000..78162f0c14a
--- /dev/null
+++ b/libs/libc/termios/lib_tcgetsid.c
@@ -0,0 +1,67 @@
+/****************************************************************************
+ * libs/libc/termios/lib_tcgetsid.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/ioctl.h>
+
+#include <termios.h>
+
+#include <nuttx/serial/tioctl.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: tcgetsid
+ *
+ * Description:
+ * Obtain the process group ID of the session for which the terminal is
+ * the controlling terminal.
+ *
+ * Input Parameters:
+ * fd - The 'fd' argument is an open file descriptor associated with a
+ * terminal.
+ *
+ * Returned Value:
+ * Upon successful completion, the session leader's process group ID is
+ * returned. Otherwise, (pid_t)-1 is returned and errno is set to
+ * indicate the error.
+ *
+ ****************************************************************************/
+
+pid_t tcgetsid(int fd)
+{
+ pid_t sid;
+
+ if (ioctl(fd, TIOCGSID, &sid) < 0)
+ {
+ return (pid_t)-1;
+ }
+
+ return sid;
+}
diff --git a/libs/libc/termios/lib_tcsetpgrp.c
b/libs/libc/termios/lib_tcsetpgrp.c
new file mode 100644
index 00000000000..8e1042cb09f
--- /dev/null
+++ b/libs/libc/termios/lib_tcsetpgrp.c
@@ -0,0 +1,59 @@
+/****************************************************************************
+ * libs/libc/termios/lib_tcsetpgrp.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/ioctl.h>
+
+#include <unistd.h>
+
+#include <nuttx/serial/tioctl.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: tcsetpgrp
+ *
+ * Description:
+ * Set the foreground process group ID associated with the terminal.
+ *
+ * Input Parameters:
+ * fd - The 'fd' argument is an open file descriptor associated with a
+ * terminal.
+ * pgrp - The process group ID to be made the foreground process group.
+ *
+ * Returned Value:
+ * Upon successful completion, 0 is returned. Otherwise, -1 is returned
+ * and errno is set to indicate the error.
+ *
+ ****************************************************************************/
+
+int tcsetpgrp(int fd, pid_t pgrp)
+{
+ return ioctl(fd, TIOCSPGRP, &pgrp);
+}
diff --git a/libs/libc/unistd/CMakeLists.txt b/libs/libc/unistd/CMakeLists.txt
index 0cef734cc7a..797ff8aba9e 100644
--- a/libs/libc/unistd/CMakeLists.txt
+++ b/libs/libc/unistd/CMakeLists.txt
@@ -64,6 +64,9 @@ set(SRCS
lib_usleep.c
lib_getpgrp.c
lib_getpgid.c
+ lib_getsid.c
+ lib_setpgid.c
+ lib_setsid.c
lib_lockf.c
lib_flock.c
lib_getpass.c
diff --git a/libs/libc/unistd/Make.defs b/libs/libc/unistd/Make.defs
index e5d8d248f60..e7852230ad7 100644
--- a/libs/libc/unistd/Make.defs
+++ b/libs/libc/unistd/Make.defs
@@ -32,6 +32,7 @@ CSRCS += lib_setrlimit.c lib_getrlimit.c lib_setpriority.c
lib_getpriority.c
CSRCS += lib_futimes.c lib_lutimes.c lib_gethostname.c lib_sethostname.c
CSRCS += lib_fchownat.c lib_linkat.c lib_readlinkat.c lib_symlinkat.c
CSRCS += lib_unlinkat.c lib_usleep.c lib_getpgrp.c lib_getpgid.c
+CSRCS += lib_getsid.c lib_setpgid.c lib_setsid.c
CSRCS += lib_lockf.c lib_flock.c lib_getpass.c
CSRCS += lib_chdir.c lib_fchdir.c lib_confstr.c lib_ulimit.c
diff --git a/libs/libc/unistd/lib_getsid.c b/libs/libc/unistd/lib_getsid.c
new file mode 100644
index 00000000000..1a06613e8d8
--- /dev/null
+++ b/libs/libc/unistd/lib_getsid.c
@@ -0,0 +1,75 @@
+/****************************************************************************
+ * libs/libc/unistd/lib_getsid.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <unistd.h>
+#include <errno.h>
+
+#include <nuttx/sched.h>
+#include <nuttx/signal.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: getsid
+ *
+ * Description:
+ * Get the session ID of the process whose process ID is pid. NuttX does
+ * not implement sessions, so the session ID is the same as the process
+ * ID, mirroring getpgid().
+ *
+ * Input Parameters:
+ * pid - The process ID whose session ID is requested. A value of zero
+ * refers to the calling process.
+ *
+ * Returned Value:
+ * The session ID is returned on success. Otherwise, (pid_t)-1 is
+ * returned and errno is set: EINVAL if pid is negative, ESRCH if pid
+ * does not refer to an existing process.
+ *
+ ****************************************************************************/
+
+pid_t getsid(pid_t pid)
+{
+ if (pid < 0)
+ {
+ set_errno(EINVAL);
+ return (pid_t)-1;
+ }
+
+ if (pid == 0)
+ {
+ return _SCHED_GETPID();
+ }
+
+ if (_SIG_KILL(pid, 0) < 0)
+ {
+ return (pid_t)-1;
+ }
+
+ return pid;
+}
diff --git a/libs/libc/unistd/lib_setpgid.c b/libs/libc/unistd/lib_setpgid.c
new file mode 100644
index 00000000000..55d72659a68
--- /dev/null
+++ b/libs/libc/unistd/lib_setpgid.c
@@ -0,0 +1,87 @@
+/****************************************************************************
+ * libs/libc/unistd/lib_setpgid.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <unistd.h>
+#include <errno.h>
+
+#include <nuttx/sched.h>
+#include <nuttx/signal.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: setpgid
+ *
+ * Description:
+ * Set the process group ID of the process whose process ID is pid to
+ * pgid. NuttX does not implement process groups, so a process group
+ * always contains a single member and its ID equals the process ID.
+ * Consequently this stub only succeeds when the requested pgid matches
+ * the target pid (or is zero, which selects the target pid itself).
+ *
+ * Input Parameters:
+ * pid - The process whose process group ID is to be changed. A value of
+ * zero refers to the calling process.
+ * pgid - The new process group ID. A value of zero uses the target pid.
+ *
+ * Returned Value:
+ * Zero is returned on success. Otherwise, -1 is returned and errno is
+ * set: EINVAL if pgid is negative, ESRCH if pid does not exist, EPERM if
+ * the requested pgid cannot be honored by this single-member-group model.
+ *
+ ****************************************************************************/
+
+int setpgid(pid_t pid, pid_t pgid)
+{
+ if (pgid < 0)
+ {
+ set_errno(EINVAL);
+ return -1;
+ }
+
+ if (pid == 0)
+ {
+ pid = _SCHED_GETPID();
+ }
+ else if (_SIG_KILL(pid, 0) < 0)
+ {
+ return -1;
+ }
+
+ /* A process group can only contain the single member 'pid', so the only
+ * legal group ID is 'pid' itself (a zero pgid selects it implicitly).
+ */
+
+ if (pgid != 0 && pgid != pid)
+ {
+ set_errno(EPERM);
+ return -1;
+ }
+
+ return 0;
+}
diff --git a/libs/libc/unistd/lib_setsid.c b/libs/libc/unistd/lib_setsid.c
new file mode 100644
index 00000000000..86fc66ba2f4
--- /dev/null
+++ b/libs/libc/unistd/lib_setsid.c
@@ -0,0 +1,57 @@
+/****************************************************************************
+ * libs/libc/unistd/lib_setsid.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership. The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <unistd.h>
+
+#include <nuttx/sched.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: setsid
+ *
+ * Description:
+ * Create a new session, if the calling process is not already a process
+ * group leader. NuttX does not implement sessions or process groups, so
+ * each task is treated as its own session and process group. This stub
+ * therefore returns the caller's PID, which acts as the session ID.
+ *
+ * Input Parameters:
+ * None
+ *
+ * Returned Value:
+ * The session ID (the caller's PID) is returned. A failure return of
+ * (pid_t)-1 with errno set to EPERM is not possible here because there is
+ * no process-group leadership to conflict with.
+ *
+ ****************************************************************************/
+
+pid_t setsid(void)
+{
+ return _SCHED_GETPID();
+}
