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* [PATCH v4 0/3] Add pidfd_spawn, pidfd_spawnp, pidfd_fork, and pidfd_getpid
@ 2023-05-17 17:35 Adhemerval Zanella
  2023-05-17 17:35 ` [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349) Adhemerval Zanella
                   ` (2 more replies)
  0 siblings, 3 replies; 13+ messages in thread
From: Adhemerval Zanella @ 2023-05-17 17:35 UTC (permalink / raw)
  To: libc-alpha, Luca Boccassi, Florian Weimer, Philip Withnall

The glibc 2.36 added wrappers for Linux syscall pidfd_open,
pidfd_getfd, and pidfd_send_signal, and exported the P_PIDFD to use
along with waitid.  However, although the pidfd is a race free
interface, the pidfd_open is subject to TOCTOU if the file descriptor
is not obtained directly from the clone or clone3 syscall (there is
still a small window between the clone return and the pidfd_getfd
where the process can be reaped and the process ID reused).

A fully race free interface with posix_spawn interface is being
discussed by GNOME [1] [2], and Qt already uses on its QtProcess
implementation [3].  The Qt implementation has some pitfalls:

  - It calls clone through the syscall symbol, which does not run the
    pthread_atfork handlers even though it really intends to use the
    clone semantic for fork (by only using CLONE_PIDFD | SIGCHLD).

  - It also does not reset any internal state, such as internal IO,
    malloc, loader, etc. locks.

  - It does not set the TCB tid field nor the robust list, used by
    pthread code.

  - It does not optimize process creation by using CLONE_VM and
    CLONE_VFORK.

This patchset adds new interfaces that take care of this potential
issues.  The pidfd_spawn and pidfd_spawnp handles all these cases by
using the same internal implementation used by posix_spawn:

  int pidfd_spawn (int *restrict pidfd,
 		   const char *restrict file,
  		   const posix_spawn_file_actions_t *restrict facts,
  		   const posix_spawnattr_t *restrict attrp,
  		   char *const argv[restrict],
  		   char *const envp[restrict])

  int pidfd_spawnp (int *restrict pidfd,
 		    const char *restrict path,
  		    const posix_spawn_file_actions_t *restrict facts,
  		    const posix_spawnattr_t *restrict attrp,
  		    char *const argv[restrict_arr],
  		    char *const envp[restrict_arr]);

The implementation makes sure that kernel must support the complete
pidfd interface, meaning that waitid (P_PIDFD) should be supported.  It
ensure that non racy workaround is required (such as reading procfs
fdinfo pid to use along with old wait interfaces).  If kernel does not
have the required support the interface returns ENOSYS.

A new symbol is used instead of a posix_spawn extension to avoid
possible issue with language bindings that might track the argument
lifetime.

Both symbols reuse the posix_spawn posix_spawn_file_actions_t and
posix_spawnattr_t, to either avoid rehash posix_spawn API or add a new
one.  It also mean that both interfaces support the same attribute and
file actions, and a new flag or file actions on posix_spawn is also
added automatically for pidfd_spawn.

Along with the spawn interface, a fork like one is also provided:

  int pidfd_fork (unsigned int flags)

The kernel already sets O_CLOEXEC as default and it follow fork/_Fork
convention on returning a positive or negative value to the parent
(with negative indicating an error) and zero to the child.

Similar to fork, pidfd_fork also run the handler setup by pthread_atfork
and reset some internal libc state.  It can be changed by using the
PIDFDFORK_ASYNCSAFE, where pidfd_fork acts as _Fork.

To have a way to interop between process IDs and process file
descriptors, the pidfd_getpid is also provided.  It just read the procps
fdinfo entry from the file descriptor to get the process ID.

---

Changes from v3:
- Remove strtoul usage.
- Fixed patchwork tst-pidfd_getpid.c regression.
- Fixed manual and NEWS typos.

Changes from v2:
- Added pidfd_fork and pidfd_getpid manual entries
- Change pidfd_fork to act as fork as default, instead as _Fork.
- Changed PIDFD_FORK_RUNATFORK flag to PIDFDFORK_ASYNCSAFE.
- Added pidfd_getpid test for EREMOTE.

Changes from v1:
- Extended pidfd_getpid error codes to return EBADF if fdinfo does not
  have Pid entry or if the value is invalid, EREMOTE is pid is in a 
  separate namespace, and ESRCH if is already terminated.
- Extended tst-pidfd_getpid.
- Rename PIDFD_FORK_RUNATFORK to PIDFDFORK_RUNATFORK to avoid clash
  with possible kernel extensions.


Adhemerval Zanella (3):
  posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349)
  posix: Add pidfd_fork
  linux: Add pidfd_getpid

 NEWS                                          |  16 ++
 bits/spawn_ext.h                              |  21 ++
 include/clone_internal.h                      |   4 +
 manual/process.texi                           |  82 ++++++--
 posix/Makefile                                |   5 +-
 posix/fork-internal.c                         | 125 ++++++++++++
 posix/fork-internal.h                         |  29 +++
 posix/fork.c                                  |  98 +---------
 posix/spawn.h                                 |   2 +
 posix/spawn_int.h                             |   3 +-
 posix/tst-posix_spawn-setsid.c                | 168 +++++++++++-----
 posix/tst-spawn-chdir.c                       |  15 +-
 posix/tst-spawn.c                             |  24 +--
 posix/tst-spawn.h                             |  36 ++++
 posix/tst-spawn2.c                            |  17 +-
 posix/tst-spawn3.c                            | 100 +++++-----
 posix/tst-spawn4.c                            |   7 +-
 posix/tst-spawn5.c                            |  14 +-
 posix/tst-spawn6.c                            |  15 +-
 posix/tst-spawn7.c                            |  13 +-
 sysdeps/nptl/_Fork.c                          |   2 +-
 sysdeps/unix/sysv/linux/Makefile              |  26 +++
 sysdeps/unix/sysv/linux/Versions              |   6 +
 sysdeps/unix/sysv/linux/aarch64/libc.abilist  |   4 +
 sysdeps/unix/sysv/linux/alpha/libc.abilist    |   4 +
 sysdeps/unix/sysv/linux/arc/libc.abilist      |   4 +
 sysdeps/unix/sysv/linux/arch-fork.h           |  16 +-
 sysdeps/unix/sysv/linux/arm/be/libc.abilist   |   4 +
 sysdeps/unix/sysv/linux/arm/le/libc.abilist   |   4 +
 sysdeps/unix/sysv/linux/bits/spawn_ext.h      |  45 +++++
 sysdeps/unix/sysv/linux/clone-pidfd-support.c |  58 ++++++
 sysdeps/unix/sysv/linux/csky/libc.abilist     |   4 +
 sysdeps/unix/sysv/linux/hppa/libc.abilist     |   4 +
 sysdeps/unix/sysv/linux/i386/libc.abilist     |   4 +
 sysdeps/unix/sysv/linux/ia64/libc.abilist     |   4 +
 .../sysv/linux/loongarch/lp64/libc.abilist    |   4 +
 .../sysv/linux/m68k/coldfire/libc.abilist     |   4 +
 .../unix/sysv/linux/m68k/m680x0/libc.abilist  |   4 +
 .../sysv/linux/microblaze/be/libc.abilist     |   4 +
 .../sysv/linux/microblaze/le/libc.abilist     |   4 +
 .../sysv/linux/mips/mips32/fpu/libc.abilist   |   4 +
 .../sysv/linux/mips/mips32/nofpu/libc.abilist |   4 +
 .../sysv/linux/mips/mips64/n32/libc.abilist   |   4 +
 .../sysv/linux/mips/mips64/n64/libc.abilist   |   4 +
 sysdeps/unix/sysv/linux/nios2/libc.abilist    |   4 +
 sysdeps/unix/sysv/linux/or1k/libc.abilist     |   4 +
 sysdeps/unix/sysv/linux/pidfd_fork.c          |  76 ++++++++
 sysdeps/unix/sysv/linux/pidfd_getpid.c        | 122 ++++++++++++
 sysdeps/unix/sysv/linux/pidfd_spawn.c         |  30 +++
 sysdeps/unix/sysv/linux/pidfd_spawnp.c        |  30 +++
 .../linux/powerpc/powerpc32/fpu/libc.abilist  |   4 +
 .../powerpc/powerpc32/nofpu/libc.abilist      |   4 +
 .../linux/powerpc/powerpc64/be/libc.abilist   |   4 +
 .../linux/powerpc/powerpc64/le/libc.abilist   |   4 +
 sysdeps/unix/sysv/linux/procutils.c           | 104 ++++++++++
 sysdeps/unix/sysv/linux/procutils.h           |  35 ++++
 .../unix/sysv/linux/riscv/rv32/libc.abilist   |   4 +
 .../unix/sysv/linux/riscv/rv64/libc.abilist   |   4 +
 .../unix/sysv/linux/s390/s390-32/libc.abilist |   4 +
 .../unix/sysv/linux/s390/s390-64/libc.abilist |   4 +
 sysdeps/unix/sysv/linux/sh/be/libc.abilist    |   4 +
 sysdeps/unix/sysv/linux/sh/le/libc.abilist    |   4 +
 .../sysv/linux/sparc/sparc32/libc.abilist     |   4 +
 .../sysv/linux/sparc/sparc64/libc.abilist     |   4 +
 sysdeps/unix/sysv/linux/spawni.c              |  20 +-
 sysdeps/unix/sysv/linux/sys/pidfd.h           |  17 ++
 sysdeps/unix/sysv/linux/tst-pidfd.c           |  45 +++++
 sysdeps/unix/sysv/linux/tst-pidfd_fork.c      | 150 +++++++++++++++
 sysdeps/unix/sysv/linux/tst-pidfd_getpid.c    | 181 ++++++++++++++++++
 .../sysv/linux/tst-posix_spawn-setsid-pidfd.c |  20 ++
 .../unix/sysv/linux/tst-spawn-chdir-pidfd.c   |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn-pidfd.c     |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn-pidfd.h     |  63 ++++++
 sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c    |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c    |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c    |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c    |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c    |  20 ++
 sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c    |  20 ++
 .../unix/sysv/linux/x86_64/64/libc.abilist    |   4 +
 .../unix/sysv/linux/x86_64/x32/libc.abilist   |   4 +
 81 files changed, 1877 insertions(+), 259 deletions(-)
 create mode 100644 bits/spawn_ext.h
 create mode 100644 posix/fork-internal.c
 create mode 100644 posix/fork-internal.h
 create mode 100644 posix/tst-spawn.h
 create mode 100644 sysdeps/unix/sysv/linux/bits/spawn_ext.h
 create mode 100644 sysdeps/unix/sysv/linux/clone-pidfd-support.c
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_fork.c
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_getpid.c
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_spawn.c
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_spawnp.c
 create mode 100644 sysdeps/unix/sysv/linux/procutils.c
 create mode 100644 sysdeps/unix/sysv/linux/procutils.h
 create mode 100644 sysdeps/unix/sysv/linux/tst-pidfd_fork.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-pidfd_getpid.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-posix_spawn-setsid-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn-chdir-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn-pidfd.h
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c

-- 
2.34.1


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349)
  2023-05-17 17:35 [PATCH v4 0/3] Add pidfd_spawn, pidfd_spawnp, pidfd_fork, and pidfd_getpid Adhemerval Zanella
@ 2023-05-17 17:35 ` Adhemerval Zanella
  2023-05-22 10:41   ` Florian Weimer
  2023-05-17 17:35 ` [PATCH v4 2/3] posix: Add pidfd_fork Adhemerval Zanella
  2023-05-17 17:35 ` [PATCH v4 3/3] linux: Add pidfd_getpid Adhemerval Zanella
  2 siblings, 1 reply; 13+ messages in thread
From: Adhemerval Zanella @ 2023-05-17 17:35 UTC (permalink / raw)
  To: libc-alpha, Luca Boccassi, Florian Weimer, Philip Withnall

Returning a pidfd allows a process to keep a race-free handle to a child
process, otherwise the caller will need to either use pidfd_open (which
still might be subject to TOCTOU) or keep using the old racy interface.

The implementation makes sure that kernel must support the complete
pidfd interface, meaning that waitid (P_PIDFD) should be supported
(added on Linux 5.4).  It ensure that non racy workaround is required
(such as reading procfs fdinfo pid to use along with old wait interfaces).
 If kernel does not have the required support the interface returns ENOSYS.

These interfaces are similar to the posix_spawn and posix_spawnp, with
the only different diferent being it returns a process file descriptor
(int) instead of process ID (pid_t).  Their prototypes are:

  int pidfd_spawn (int *restrict pidfd,
 		   const char *restrict file,
  		   const posix_spawn_file_actions_t *restrict facts,
  		   const posix_spawnattr_t *restrict attrp,
  		   char *const argv[restrict],
  		   char *const envp[restrict])

  int pidfd_spawnp (int *restrict pidfd,
 		    const char *restrict path,
  		    const posix_spawn_file_actions_t *restrict facts,
  		    const posix_spawnattr_t *restrict attrp,
  		    char *const argv[restrict_arr],
  		    char *const envp[restrict_arr]);

A new symbol is used instead of a posix_spawn extension to avoid possible
issue with language bindings that might track the return argument
lifetime.  Although, on Linux pid_t and int are interchangeable, POSIX
only state that pid_t should be a signed interger.

Both symbols reuse the posix_spawn posix_spawn_file_actions_t and
posix_spawnattr_t, to void rehash posix_spawn API or add a new one.
 It also mean that both interfaces support the same attribute and
file actions, and a new flag or file actions on posix_spawn is also
added automatically for pidfd_spawn.

Also, using posix_spawn plumbering allows to reuse most of the current
testing with some changes:

  - waitid is used instead of waitpid, since it is a more generic
    interface.

  - tst-posix_spawn-setsid.c is adapted to take in consideration that
    caller can check for session id directly.  The test now spawn itself
    and write the session id a file instead.

  - tst-spawn3.c need to know where pidfd_spawn is used so it keep
    an extra file description ununsed.

Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PID or waitid
support), Linux 5.15 (only clone support), and Linux 5.19 (full
support including clone3).
---
 NEWS                                          |   7 +
 bits/spawn_ext.h                              |  21 +++
 include/clone_internal.h                      |   4 +
 manual/process.texi                           |  14 +-
 posix/Makefile                                |   2 +
 posix/spawn.h                                 |   2 +
 posix/spawn_int.h                             |   3 +-
 posix/tst-posix_spawn-setsid.c                | 168 +++++++++++++-----
 posix/tst-spawn-chdir.c                       |  15 +-
 posix/tst-spawn.c                             |  24 +--
 posix/tst-spawn.h                             |  36 ++++
 posix/tst-spawn2.c                            |  17 +-
 posix/tst-spawn3.c                            | 100 ++++++-----
 posix/tst-spawn4.c                            |   7 +-
 posix/tst-spawn5.c                            |  14 +-
 posix/tst-spawn6.c                            |  15 +-
 posix/tst-spawn7.c                            |  13 +-
 sysdeps/unix/sysv/linux/Makefile              |  20 +++
 sysdeps/unix/sysv/linux/Versions              |   4 +
 sysdeps/unix/sysv/linux/aarch64/libc.abilist  |   2 +
 sysdeps/unix/sysv/linux/alpha/libc.abilist    |   2 +
 sysdeps/unix/sysv/linux/arc/libc.abilist      |   2 +
 sysdeps/unix/sysv/linux/arm/be/libc.abilist   |   2 +
 sysdeps/unix/sysv/linux/arm/le/libc.abilist   |   2 +
 sysdeps/unix/sysv/linux/bits/spawn_ext.h      |  45 +++++
 sysdeps/unix/sysv/linux/clone-pidfd-support.c |  58 ++++++
 sysdeps/unix/sysv/linux/csky/libc.abilist     |   2 +
 sysdeps/unix/sysv/linux/hppa/libc.abilist     |   2 +
 sysdeps/unix/sysv/linux/i386/libc.abilist     |   2 +
 sysdeps/unix/sysv/linux/ia64/libc.abilist     |   2 +
 .../sysv/linux/loongarch/lp64/libc.abilist    |   2 +
 .../sysv/linux/m68k/coldfire/libc.abilist     |   2 +
 .../unix/sysv/linux/m68k/m680x0/libc.abilist  |   2 +
 .../sysv/linux/microblaze/be/libc.abilist     |   2 +
 .../sysv/linux/microblaze/le/libc.abilist     |   2 +
 .../sysv/linux/mips/mips32/fpu/libc.abilist   |   2 +
 .../sysv/linux/mips/mips32/nofpu/libc.abilist |   2 +
 .../sysv/linux/mips/mips64/n32/libc.abilist   |   2 +
 .../sysv/linux/mips/mips64/n64/libc.abilist   |   2 +
 sysdeps/unix/sysv/linux/nios2/libc.abilist    |   2 +
 sysdeps/unix/sysv/linux/or1k/libc.abilist     |   2 +
 sysdeps/unix/sysv/linux/pidfd_spawn.c         |  30 ++++
 sysdeps/unix/sysv/linux/pidfd_spawnp.c        |  30 ++++
 .../linux/powerpc/powerpc32/fpu/libc.abilist  |   2 +
 .../powerpc/powerpc32/nofpu/libc.abilist      |   2 +
 .../linux/powerpc/powerpc64/be/libc.abilist   |   2 +
 .../linux/powerpc/powerpc64/le/libc.abilist   |   2 +
 .../unix/sysv/linux/riscv/rv32/libc.abilist   |   2 +
 .../unix/sysv/linux/riscv/rv64/libc.abilist   |   2 +
 .../unix/sysv/linux/s390/s390-32/libc.abilist |   2 +
 .../unix/sysv/linux/s390/s390-64/libc.abilist |   2 +
 sysdeps/unix/sysv/linux/sh/be/libc.abilist    |   2 +
 sysdeps/unix/sysv/linux/sh/le/libc.abilist    |   2 +
 .../sysv/linux/sparc/sparc32/libc.abilist     |   2 +
 .../sysv/linux/sparc/sparc64/libc.abilist     |   2 +
 sysdeps/unix/sysv/linux/spawni.c              |  20 ++-
 .../sysv/linux/tst-posix_spawn-setsid-pidfd.c |  20 +++
 .../unix/sysv/linux/tst-spawn-chdir-pidfd.c   |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn-pidfd.c     |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn-pidfd.h     |  63 +++++++
 sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c    |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c    |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c    |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c    |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c    |  20 +++
 sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c    |  20 +++
 .../unix/sysv/linux/x86_64/64/libc.abilist    |   2 +
 .../unix/sysv/linux/x86_64/x32/libc.abilist   |   2 +
 68 files changed, 829 insertions(+), 151 deletions(-)
 create mode 100644 bits/spawn_ext.h
 create mode 100644 posix/tst-spawn.h
 create mode 100644 sysdeps/unix/sysv/linux/bits/spawn_ext.h
 create mode 100644 sysdeps/unix/sysv/linux/clone-pidfd-support.c
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_spawn.c
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_spawnp.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-posix_spawn-setsid-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn-chdir-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn-pidfd.h
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c

diff --git a/NEWS b/NEWS
index a52c17c677..2c49eaf373 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,13 @@ Major new features:
   The symbol names follow the AArch64 vector ABI, they are declared
   in math.h and have to be called manually at this point.
 
+* On Linux, the pidfd_spawn and pidfd_spawp functions have been added.
+  They have similar prototype and semantic as posix_spawn, but instead of
+  returning a process ID, they return a file descriptor that can be used
+  along other pidfd function (like pidfd_send_signal, poll, or waitid).
+  The pidfd functionality avoid the issue of PID reuse with traditional
+  posix_spawn interface.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * In the Linux kernel for the hppa/parisc architecture some of the
diff --git a/bits/spawn_ext.h b/bits/spawn_ext.h
new file mode 100644
index 0000000000..75b504a768
--- /dev/null
+++ b/bits/spawn_ext.h
@@ -0,0 +1,21 @@
+/* POSIX spawn extensions.   Generic version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SPAWN_H
+# error "Never include <bits/spawn-ext.h> directly; use <spawn.h> instead."
+#endif
diff --git a/include/clone_internal.h b/include/clone_internal.h
index dd380f119e..54df6c8917 100644
--- a/include/clone_internal.h
+++ b/include/clone_internal.h
@@ -35,6 +35,10 @@ extern int __clone_internal_fallback (struct clone_args *__cl_args,
 				      void *__arg)
      attribute_hidden;
 
+/* Return whether the kernel supports pid file descriptor, including clone
+   with CLONE_PIDFD and waitid with P_PIDFD.  */
+extern bool __clone_pidfd_supported (void) attribute_hidden;
+
 #ifndef _ISOMAC
 libc_hidden_proto (__clone3)
 libc_hidden_proto (__clone_internal)
diff --git a/manual/process.texi b/manual/process.texi
index 9307379194..927aebbe3d 100644
--- a/manual/process.texi
+++ b/manual/process.texi
@@ -136,13 +136,13 @@ creating a process and making it run another program.
 @cindex parent process
 @cindex subprocess
 A new processes is created when one of the functions
-@code{posix_spawn}, @code{fork}, @code{_Fork} or @code{vfork} is called.
-(The @code{system} and @code{popen} also create new processes internally.)
-Due to the name of the @code{fork} function, the act of creating a new
-process is sometimes called @dfn{forking} a process.  Each new process
-(the @dfn{child process} or @dfn{subprocess}) is allocated a process
-ID, distinct from the process ID of the parent process.  @xref{Process
-Identification}.
+@code{posix_spawn}, @code{fork}, @code{_Fork}, @code{vfork}, or
+@code{pidfd_spawn} is called.  (The @code{system} and @code{popen} also
+create new processes internally.)  Due to the name of the @code{fork}
+function, the act of creating a new process is sometimes called
+@dfn{forking} a process.  Each new process (the @dfn{child process} or
+@dfn{subprocess}) is allocated a process ID, distinct from the process
+ID of the parent process.  @xref{Process Identification}.
 
 After forking a child process, both the parent and child processes
 continue to execute normally.  If you want your program to wait for a
diff --git a/posix/Makefile b/posix/Makefile
index cc77e939ad..4016a7758a 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -37,6 +37,7 @@ headers := \
   bits/pthreadtypes-arch.h \
   bits/pthreadtypes.h \
   bits/sched.h \
+  bits/spawn_ext.h \
   bits/thread-shared-types.h \
   bits/types.h \
   bits/types/idtype_t.h \
@@ -591,6 +592,7 @@ tst-spawn-static-ARGS = $(tst-spawn-ARGS)
 tst-spawn5-ARGS = -- $(host-test-program-cmd)
 tst-spawn6-ARGS = -- $(host-test-program-cmd)
 tst-spawn7-ARGS = -- $(host-test-program-cmd)
+tst-posix_spawn-setsid-ARGS = -- $(host-test-program-cmd)
 tst-dir-ARGS = `pwd` `cd $(common-objdir)/$(subdir); pwd` `cd $(common-objdir); pwd` $(objpfx)tst-dir
 tst-chmod-ARGS = $(objdir)
 tst-vfork3-ARGS = --test-dir=$(objpfx)
diff --git a/posix/spawn.h b/posix/spawn.h
index 0a6a070523..2e20991627 100644
--- a/posix/spawn.h
+++ b/posix/spawn.h
@@ -229,6 +229,8 @@ posix_spawn_file_actions_addtcsetpgrp_np (posix_spawn_file_actions_t *,
 
 #endif /* __USE_MISC */
 
+#include <bits/spawn_ext.h>
+
 __END_DECLS
 
 #endif /* spawn.h */
diff --git a/posix/spawn_int.h b/posix/spawn_int.h
index aeb066c44f..64ee03e62d 100644
--- a/posix/spawn_int.h
+++ b/posix/spawn_int.h
@@ -76,12 +76,13 @@ struct __spawn_action
 
 #define SPAWN_XFLAGS_USE_PATH	0x1
 #define SPAWN_XFLAGS_TRY_SHELL	0x2
+#define SPAWN_XFLAGS_RET_PIDFD  0x4
 
 extern int __posix_spawn_file_actions_realloc (posix_spawn_file_actions_t *
 					       file_actions)
      attribute_hidden;
 
-extern int __spawni (pid_t *pid, const char *path,
+extern int __spawni (int *pid, const char *path,
 		     const posix_spawn_file_actions_t *file_actions,
 		     const posix_spawnattr_t *attrp, char *const argv[],
 		     char *const envp[], int xflags) attribute_hidden;
diff --git a/posix/tst-posix_spawn-setsid.c b/posix/tst-posix_spawn-setsid.c
index 124d878ce2..751674165c 100644
--- a/posix/tst-posix_spawn-setsid.c
+++ b/posix/tst-posix_spawn-setsid.c
@@ -18,78 +18,158 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <getopt.h>
+#include <intprops.h>
+#include <paths.h>
 #include <spawn.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/resource.h>
+#include <sys/wait.h>
 #include <unistd.h>
 
 #include <support/check.h>
+#include <support/xunistd.h>
+#include <support/temp_file.h>
+#include <tst-spawn.h>
+
+/* Nonzero if the program gets called via `exec'.  */
+static int restart;
+
+/* Hold the four initial argument used to respawn the process, plus
+   the extra '--direct' and '--restart', and a final NULL.  */
+static char *initial_argv[7];
+static int initial_argv_count;
+
+#define CMDLINE_OPTIONS \
+  { "restart", no_argument, &restart, 1 },
+
+static char *pidfile;
+
+static pid_t
+read_child_sid (void)
+{
+  int pidfd = xopen (pidfile, O_RDONLY, 0);
+
+  char buf[INT_STRLEN_BOUND (pid_t)];
+  ssize_t n = read (pidfd, buf, sizeof (buf));
+  TEST_VERIFY (n < sizeof buf && n >= 0);
+  buf[n] = '\0';
+
+  /* We only expect to read the PID.  */
+  char *endp;
+  long int rpid = strtol (buf, &endp, 10);
+  TEST_VERIFY (endp != buf);
+
+  xclose (pidfd);
+
+  return rpid;
+}
+
+/* Called on process re-execution, write down the session id on PIDFILE.  */
+_Noreturn static void
+handle_restart (const char *pidfile)
+{
+  int pidfd = xopen (pidfile, O_WRONLY, 0);
+
+  char buf[INT_STRLEN_BOUND (pid_t)];
+  int s = snprintf (buf, sizeof buf, "%d", getsid (0));
+  size_t n = write (pidfd, buf, s);
+  TEST_VERIFY (n == s);
+
+  xclose (pidfd);
+
+  exit (EXIT_SUCCESS);
+}
 
 static void
 do_test_setsid (bool test_setsid)
 {
-  pid_t sid, child_sid;
-  int res;
-
   /* Current session ID.  */
-  sid = getsid(0);
-  if (sid == (pid_t) -1)
-    FAIL_EXIT1 ("getsid (0): %m");
+  pid_t sid = getsid (0);
+  TEST_VERIFY (sid != (pid_t) -1);
 
   posix_spawnattr_t attrp;
-  /* posix_spawnattr_init should not fail (it basically memset the
-     attribute).  */
-  posix_spawnattr_init (&attrp);
+  TEST_COMPARE (posix_spawnattr_init (&attrp), 0);
   if (test_setsid)
-    {
-      res = posix_spawnattr_setflags (&attrp, POSIX_SPAWN_SETSID);
-      if (res != 0)
-	{
-	  errno = res;
-	  FAIL_EXIT1 ("posix_spawnattr_setflags: %m");
-	}
-    }
-
-  /* Program to run.  */
-  char *args[2] = { (char *) "true", NULL };
-  pid_t child;
-
-  res = posix_spawnp (&child, "true", NULL, &attrp, args, environ);
-  /* posix_spawnattr_destroy is noop.  */
-  posix_spawnattr_destroy (&attrp);
-
-  if (res != 0)
-    {
-      errno = res;
-      FAIL_EXIT1 ("posix_spawnp: %m");
-    }
+    TEST_COMPARE (posix_spawnattr_setflags (&attrp, POSIX_SPAWN_SETSID), 0);
+
+  /* 1 or 4 elements from initial_argv:
+       + path to ld.so          optional
+       + --library-path         optional
+       + the library path       optional
+       + application name
+       + --direct
+       + --restart
+       + pidfile  */
+  int argv_size = initial_argv_count + 2;
+  char *args[argv_size];
+  int argc = 0;
+
+  for (char **arg = initial_argv; *arg != NULL; arg++)
+    args[argc++] = *arg;
+  args[argc++] = pidfile;
+  args[argc] = NULL;
+  TEST_VERIFY (argc < argv_size);
+
+  PID_T_TYPE pid;
+  TEST_COMPARE (POSIX_SPAWN (&pid, args[0], NULL, &attrp, args, environ), 0);
+  TEST_COMPARE (posix_spawnattr_destroy (&attrp), 0);
+
+  siginfo_t sinfo;
+  TEST_COMPARE (WAITID (P_PID, pid, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
+
+  pid_t child_sid = read_child_sid ();
 
   /* Child should have a different session ID than parent.  */
-  child_sid = getsid (child);
-
-  if (child_sid == (pid_t) -1)
-    FAIL_EXIT1 ("getsid (%i): %m", child);
+  TEST_VERIFY (child_sid != (pid_t) -1);
 
   if (test_setsid)
-    {
-      if (child_sid == sid)
-	FAIL_EXIT1 ("child session ID matched parent one");
-    }
+    TEST_VERIFY (child_sid != sid);
   else
-    {
-      if (child_sid != sid)
-	FAIL_EXIT1 ("child session ID did not match parent one");
-    }
+    TEST_VERIFY (child_sid == sid);
 }
 
 static int
-do_test (void)
+do_test (int argc, char *argv[])
 {
+  /* We must have either:
+
+     - one or four parameters if called initially:
+       + argv[1]: path for ld.so        optional
+       + argv[2]: "--library-path"      optional
+       + argv[3]: the library path      optional
+       + argv[4]: the application name
+
+     - six parameters left if called through re-execution:
+       + argv[5/1]: the application name
+       + argv[6/2]: the pidfile
+
+     * When built with --enable-hardcoded-path-in-tests or issued without
+       using the loader directly.  */
+
+  if (restart)
+    handle_restart (argv[1]);
+
+  TEST_VERIFY_EXIT (argc == 2 || argc == 5);
+
+  int i;
+  for (i = 0; i < argc - 1; i++)
+    initial_argv[i] = argv[i + 1];
+  initial_argv[i++] = (char *) "--direct";
+  initial_argv[i++] = (char *) "--restart";
+  initial_argv_count = i;
+
+  create_temp_file ("tst-posix_spawn-setsid-", &pidfile);
+
   do_test_setsid (false);
   do_test_setsid (true);
 
   return 0;
 }
 
+#define TEST_FUNCTION_ARGV do_test
 #include <support/test-driver.c>
diff --git a/posix/tst-spawn-chdir.c b/posix/tst-spawn-chdir.c
index b335092d7f..c01ca6692d 100644
--- a/posix/tst-spawn-chdir.c
+++ b/posix/tst-spawn-chdir.c
@@ -29,7 +29,9 @@
 #include <support/test-driver.h>
 #include <support/xstdio.h>
 #include <support/xunistd.h>
+#include <sys/wait.h>
 #include <unistd.h>
+#include <tst-spawn.h>
 
 /* Reads the file at PATH, which must consist of exactly one line.
    Removes the line terminator at the end of the file.  */
@@ -169,17 +171,18 @@ do_test (void)
 
           char *const argv[] = { (char *) "pwd", NULL };
           char *const envp[] = { NULL } ;
-          pid_t pid;
+          PID_T_TYPE pid;
           if (do_spawnp)
-            TEST_COMPARE (posix_spawnp (&pid, "pwd", &actions,
+            TEST_COMPARE (POSIX_SPAWNP (&pid, "pwd", &actions,
                                         NULL, argv, envp), 0);
           else
-            TEST_COMPARE (posix_spawn (&pid, "subdir/pwd-symlink", &actions,
+            TEST_COMPARE (POSIX_SPAWN (&pid, "subdir/pwd-symlink", &actions,
                                        NULL, argv, envp), 0);
           TEST_VERIFY (pid > 0);
-          int status;
-          xwaitpid (pid, &status, 0);
-          TEST_COMPARE (status, 0);
+          siginfo_t sinfo;
+          TEST_COMPARE (WAITID (P_ALL, 0, &sinfo, WEXITED), 0);
+          TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+          TEST_COMPARE (sinfo.si_status, 0);
 
           /* Check that the current directory did not change.  */
           {
diff --git a/posix/tst-spawn.c b/posix/tst-spawn.c
index 6782a322fc..c44d90756a 100644
--- a/posix/tst-spawn.c
+++ b/posix/tst-spawn.c
@@ -25,11 +25,13 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/param.h>
+#include <sys/wait.h>
 
 #include <support/check.h>
 #include <support/xunistd.h>
 #include <support/temp_file.h>
 #include <support/support.h>
+#include <tst-spawn.h>
 
 
 /* Nonzero if the program gets called via `exec'.  */
@@ -143,9 +145,9 @@ handle_restart (const char *fd1s, const char *fd2s, const char *fd3s,
 static int
 do_test (int argc, char *argv[])
 {
-  pid_t pid;
+  PID_T_TYPE pid;
   int fd4;
-  int status;
+  siginfo_t sinfo;
   posix_spawn_file_actions_t actions;
   char fd1name[18];
   char fd2name[18];
@@ -233,17 +235,16 @@ do_test (int argc, char *argv[])
   spargv[i++] = fd5name;
   spargv[i] = NULL;
 
-  TEST_COMPARE (posix_spawn (&pid, argv[1], &actions, NULL, spargv, environ),
+  TEST_COMPARE (POSIX_SPAWN (&pid, argv[1], &actions, NULL, spargv, environ),
 		0);
 
   /* Wait for the children.  */
-  TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
-  TEST_VERIFY (WIFEXITED (status));
-  TEST_VERIFY (!WIFSIGNALED (status));
-  TEST_COMPARE (WEXITSTATUS (status), 0);
+  TEST_COMPARE (WAITID (P_PID, pid, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
 
   /* Same test but with a NULL pid argument.  */
-  TEST_COMPARE (posix_spawn (NULL, argv[1], &actions, NULL, spargv, environ),
+  TEST_COMPARE (POSIX_SPAWN (NULL, argv[1], &actions, NULL, spargv, environ),
 		0);
 
   /* Cleanup.  */
@@ -251,10 +252,9 @@ do_test (int argc, char *argv[])
   free (name3_copy);
 
   /* Wait for the children.  */
-  xwaitpid (-1, &status, 0);
-  TEST_VERIFY (WIFEXITED (status));
-  TEST_VERIFY (!WIFSIGNALED (status));
-  TEST_COMPARE (WEXITSTATUS (status), 0);
+  TEST_COMPARE (WAITID (P_ALL, 0, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
 
   return 0;
 }
diff --git a/posix/tst-spawn.h b/posix/tst-spawn.h
new file mode 100644
index 0000000000..a6f2dc8680
--- /dev/null
+++ b/posix/tst-spawn.h
@@ -0,0 +1,36 @@
+/* Generic definitions for posix_spawn tests.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef PID_T_TYPE
+# define PID_T_TYPE pid_t
+#endif
+
+#ifndef POSIX_SPAWN
+# define POSIX_SPAWN(__child, __path, __actions, __attr, __argv, __envp) \
+  posix_spawn (__child, __path, __actions, __attr, __argv, __envp)
+#endif
+
+#ifndef POSIX_SPAWNP
+# define POSIX_SPAWNP(__child, __path, __actions, __attr, __argv, __envp) \
+  posix_spawnp (__child, __path, __actions, __attr, __argv, __envp)
+#endif
+
+#ifndef WAITID
+# define WAITID(__idtype, __id, __info, __opts) \
+  waitid (__idtype, __id, __info, __opts)
+#endif
diff --git a/posix/tst-spawn2.c b/posix/tst-spawn2.c
index 40dc692488..f5c1f13039 100644
--- a/posix/tst-spawn2.c
+++ b/posix/tst-spawn2.c
@@ -26,6 +26,7 @@
 #include <stdio.h>
 
 #include <support/check.h>
+#include <tst-spawn.h>
 
 int
 do_test (void)
@@ -35,9 +36,9 @@ do_test (void)
 
   const char *program = "/path/to/invalid/binary";
   char * const args[] = { 0 };
-  pid_t pid = -1;
+  PID_T_TYPE pid = -1;
 
-  int ret = posix_spawn (&pid, program, 0, 0, args, environ);
+  int ret = POSIX_SPAWN (&pid, program, 0, 0, args, environ);
   if (ret != ENOENT)
     {
       errno = ret;
@@ -51,14 +52,13 @@ do_test (void)
     FAIL_EXIT1 ("posix_spawn returned pid != -1 (%i)", (int) pid);
 
   /* Check if no child is actually created.  */
-  ret = waitpid (-1, NULL, 0);
-  if (ret != -1 || errno != ECHILD)
-    FAIL_EXIT1 ("waitpid: %m)");
+  TEST_COMPARE (WAITID (P_ALL, 0, NULL, WEXITED), -1);
+  TEST_COMPARE (errno, ECHILD);
 
   /* Same as before, but with posix_spawnp.  */
   char *args2[] = { (char*) program, 0 };
 
-  ret = posix_spawnp (&pid, args2[0], 0, 0, args2, environ);
+  ret = POSIX_SPAWNP (&pid, args2[0], 0, 0, args2, environ);
   if (ret != ENOENT)
     {
       errno = ret;
@@ -68,9 +68,8 @@ do_test (void)
   if (pid != -1)
     FAIL_EXIT1 ("posix_spawnp returned pid != -1 (%i)", (int) pid);
 
-  ret = waitpid (-1, NULL, 0);
-  if (ret != -1 || errno != ECHILD)
-    FAIL_EXIT1 ("waitpid: %m)");
+  TEST_COMPARE (WAITID (P_ALL, 0, NULL, WEXITED), -1);
+  TEST_COMPARE (errno, ECHILD);
 
   return 0;
 }
diff --git a/posix/tst-spawn3.c b/posix/tst-spawn3.c
index e7ce0fb386..bd21ac6c4b 100644
--- a/posix/tst-spawn3.c
+++ b/posix/tst-spawn3.c
@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#include <assert.h>
 #include <stdio.h>
 #include <spawn.h>
 #include <error.h>
@@ -27,9 +28,12 @@
 #include <sys/resource.h>
 #include <fcntl.h>
 #include <paths.h>
+#include <intprops.h>
 
 #include <support/check.h>
 #include <support/temp_file.h>
+#include <support/xunistd.h>
+#include <tst-spawn.h>
 
 static int
 do_test (void)
@@ -48,7 +52,6 @@ do_test (void)
 
   struct rlimit rl;
   int max_fd = 24;
-  int ret;
 
   /* Set maximum number of file descriptor to a low value to avoid open
      too many files in environments where RLIMIT_NOFILE is large and to
@@ -66,7 +69,7 @@ do_test (void)
   /* Exhauste the file descriptor limit with temporary files.  */
   int files[max_fd];
   int nfiles = 0;
-  for (;;)
+  for (; nfiles < max_fd; nfiles++)
     {
       int fd = create_temp_file ("tst-spawn3.", NULL);
       if (fd == -1)
@@ -75,75 +78,82 @@ do_test (void)
 	    FAIL_EXIT1 ("create_temp_file: %m");
 	  break;
 	}
-      files[nfiles++] = fd;
+      files[nfiles] = fd;
     }
+  assert (nfiles != 0);
 
   posix_spawn_file_actions_t a;
-  if (posix_spawn_file_actions_init (&a) != 0)
-    FAIL_EXIT1 ("posix_spawn_file_actions_init");
+  TEST_COMPARE (posix_spawn_file_actions_init (&a), 0);
 
   /* Executes a /bin/sh echo $$ 2>&1 > ${objpfx}tst-spawn3.pid .  */
   const char pidfile[] = OBJPFX "tst-spawn3.pid";
-  if (posix_spawn_file_actions_addopen (&a, STDOUT_FILENO, pidfile, O_WRONLY
-					| O_CREAT | O_TRUNC, 0644) != 0)
-    FAIL_EXIT1 ("posix_spawn_file_actions_addopen");
+  TEST_COMPARE (posix_spawn_file_actions_addopen (&a, STDOUT_FILENO, pidfile,
+						  O_WRONLY| O_CREAT | O_TRUNC,
+						  0644),
+		0);
 
-  if (posix_spawn_file_actions_adddup2 (&a, STDOUT_FILENO, STDERR_FILENO) != 0)
-    FAIL_EXIT1 ("posix_spawn_file_actions_adddup2");
+  TEST_COMPARE (posix_spawn_file_actions_adddup2 (&a, STDOUT_FILENO,
+						  STDERR_FILENO),
+		0);
 
   /* Since execve (called by posix_spawn) might require to open files to
      actually execute the shell script, setup to close the temporary file
      descriptors.  */
-  for (int i=0; i<nfiles; i++)
-    {
-      if (posix_spawn_file_actions_addclose (&a, files[i]))
-	FAIL_EXIT1 ("posix_spawn_file_actions_addclose");
-    }
+  int maxnfiles =
+#ifdef TST_SPAWN_PIDFD
+    /* The sparing file descriptor will be returned as the pid descriptor,
+       otherwise clone fail with EMFILE.  */
+    nfiles - 1;
+#else
+    nfiles;
+#endif
+
+  for (int i=0; i<maxnfiles; i++)
+    TEST_COMPARE (posix_spawn_file_actions_addclose (&a, files[i]), 0);
 
   char *spawn_argv[] = { (char *) _PATH_BSHELL, (char *) "-c",
 			 (char *) "echo $$", NULL };
-  pid_t pid;
-  if ((ret = posix_spawn (&pid, _PATH_BSHELL, &a, NULL, spawn_argv, NULL))
-       != 0)
-    {
-      errno = ret;
-      FAIL_EXIT1 ("posix_spawn: %m");
-    }
-
-  int status;
-  int err = waitpid (pid, &status, 0);
-  if (err != pid)
-    FAIL_EXIT1 ("waitpid: %m");
+  PID_T_TYPE pid;
+
+  {
+    int r = POSIX_SPAWN (&pid, _PATH_BSHELL, &a, NULL, spawn_argv, NULL);
+    if (r == ENOSYS)
+      FAIL_UNSUPPORTED ("kernel does not support CLONE_PIDFD clone flag");
+#ifdef TST_SPAWN_PIDFD
+    TEST_COMPARE (r, EMFILE);
+
+    /* Free up one file descriptor, so posix_spawn_pidfd_ex can return it.  */
+    xclose (files[nfiles-1]);
+    nfiles--;
+    r = POSIX_SPAWN (&pid, _PATH_BSHELL, &a, NULL, spawn_argv, NULL);
+#endif
+    TEST_COMPARE (r, 0);
+  }
+
+  siginfo_t sinfo;
+  TEST_COMPARE (WAITID (P_PID, pid, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
 
   /* Close the temporary files descriptor so it can check posix_spawn
      output.  */
   for (int i=0; i<nfiles; i++)
-    {
-      if (close (files[i]))
-	FAIL_EXIT1 ("close: %m");
-    }
+    xclose (files[i]);
 
-  int pidfd = open (pidfile, O_RDONLY);
-  if (pidfd == -1)
-    FAIL_EXIT1 ("open: %m");
+  int pidfd = xopen (pidfile, O_RDONLY, 0);
 
-  char buf[64];
-  ssize_t n;
-  if ((n = read (pidfd, buf, sizeof (buf))) < 0)
-    FAIL_EXIT1 ("read: %m");
+  char buf[INT_STRLEN_BOUND (pid_t)];
+  ssize_t n = read (pidfd, buf, sizeof (buf));
+  TEST_VERIFY (n < sizeof buf && n >= 0);
 
-  unlink (pidfile);
+  xunlink (pidfile);
 
   /* We only expect to read the PID.  */
   char *endp;
   long int rpid = strtol (buf, &endp, 10);
-  if (*endp != '\n')
-    FAIL_EXIT1 ("*endp != \'n\'");
-  if (endp == buf)
-    FAIL_EXIT1 ("read empty line");
+  TEST_VERIFY (*endp == '\n' && endp != buf);
 
-  if (rpid != pid)
-    FAIL_EXIT1 ("found \"%s\", expected pid %ld\n", buf, (long int) pid);
+  TEST_COMPARE (rpid, sinfo.si_pid);
 
   return 0;
 }
diff --git a/posix/tst-spawn4.c b/posix/tst-spawn4.c
index 327f04ea6c..8bf8bd52df 100644
--- a/posix/tst-spawn4.c
+++ b/posix/tst-spawn4.c
@@ -24,6 +24,7 @@
 #include <support/xunistd.h>
 #include <support/check.h>
 #include <support/temp_file.h>
+#include <tst-spawn.h>
 
 static int
 do_test (void)
@@ -38,15 +39,15 @@ do_test (void)
 
   TEST_VERIFY_EXIT (chmod (scriptname, 0x775) == 0);
 
-  pid_t pid;
+  PID_T_TYPE pid;
   int status;
 
   /* Check if scripts without shebang are correctly not executed.  */
-  status = posix_spawn (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
+  status = POSIX_SPAWN (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
                         (char *[]) { 0 });
   TEST_VERIFY_EXIT (status == ENOEXEC);
 
-  status = posix_spawnp (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
+  status = POSIX_SPAWNP (&pid, scriptname, NULL, NULL, (char *[]) { 0 },
                          (char *[]) { 0 });
   TEST_VERIFY_EXIT (status == ENOEXEC);
 
diff --git a/posix/tst-spawn5.c b/posix/tst-spawn5.c
index 1bd1afabcc..e42f0eb25c 100644
--- a/posix/tst-spawn5.c
+++ b/posix/tst-spawn5.c
@@ -33,6 +33,7 @@
 
 #include <arch-fd_to_filename.h>
 #include <array_length.h>
+#include <tst-spawn.h>
 
 /* Nonzero if the program gets called via `exec'.  */
 static int restart;
@@ -161,14 +162,13 @@ spawn_closefrom_test (posix_spawn_file_actions_t *fa, int lowfd, int highfd,
   args[argc] = NULL;
   TEST_VERIFY (argc < argv_size);
 
-  pid_t pid;
-  int status;
+  PID_T_TYPE pid;
+  siginfo_t sinfo;
 
-  TEST_COMPARE (posix_spawn (&pid, args[0], fa, NULL, args, environ), 0);
-  TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
-  TEST_VERIFY (WIFEXITED (status));
-  TEST_VERIFY (!WIFSIGNALED (status));
-  TEST_COMPARE (WEXITSTATUS (status), 0);
+  TEST_COMPARE (POSIX_SPAWN (&pid, args[0], fa, NULL, args, environ), 0);
+  TEST_COMPARE (WAITID (P_PID, pid, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
 }
 
 static void
diff --git a/posix/tst-spawn6.c b/posix/tst-spawn6.c
index 4e29d78168..ff36351cd6 100644
--- a/posix/tst-spawn6.c
+++ b/posix/tst-spawn6.c
@@ -32,6 +32,7 @@
 #include <sys/ioctl.h>
 #include <stdlib.h>
 #include <termios.h>
+#include <tst-spawn.h>
 
 #ifndef PATH_MAX
 # define PATH_MAX 1024
@@ -108,17 +109,15 @@ run_subprogram (int argc, char *argv[], const posix_spawnattr_t *attr,
   spargv[i] = NULL;
 
   pid_t pid;
-  TEST_COMPARE (posix_spawn (&pid, argv[1], actions, attr, spargv, environ),
+  TEST_COMPARE (POSIX_SPAWN (&pid, argv[1], actions, attr, spargv, environ),
 		exp_err);
   if (exp_err != 0)
     return;
 
-  int status;
-  TEST_COMPARE (xwaitpid (pid, &status, WUNTRACED), pid);
-  TEST_VERIFY (WIFEXITED (status));
-  TEST_VERIFY (!WIFSTOPPED (status));
-  TEST_VERIFY (!WIFSIGNALED (status));
-  TEST_COMPARE (WEXITSTATUS (status), 0);
+  siginfo_t sinfo;
+  TEST_COMPARE (WAITID (P_ALL, 0, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
 }
 
 static int
@@ -202,7 +201,7 @@ do_test (int argc, char *argv[])
   if (restart)
     return handle_restart (argv[1], argv[2]);
 
-  pid_t pid = xfork ();
+  PID_T_TYPE pid = xfork ();
   if (pid == 0)
     {
       /* Create a pseudo-terminal to avoid interfering with the one using by
diff --git a/posix/tst-spawn7.c b/posix/tst-spawn7.c
index fb06915cb7..cc4498830b 100644
--- a/posix/tst-spawn7.c
+++ b/posix/tst-spawn7.c
@@ -24,7 +24,9 @@
 #include <support/check.h>
 #include <support/xsignal.h>
 #include <support/xunistd.h>
+#include <sys/wait.h>
 #include <unistd.h>
+#include <tst-spawn.h>
 
 /* Nonzero if the program gets called via `exec'.  */
 #define CMDLINE_OPTIONS \
@@ -81,14 +83,13 @@ spawn_signal_test (const char *type, const posix_spawnattr_t *attr)
 {
   spargs[check_type_argc] = (char*) type;
 
-  pid_t pid;
-  int status;
+  PID_T_TYPE pid;
+  siginfo_t sinfo;
 
   TEST_COMPARE (posix_spawn (&pid, spargs[0], NULL, attr, spargs, environ), 0);
-  TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
-  TEST_VERIFY (WIFEXITED (status));
-  TEST_VERIFY (!WIFSIGNALED (status));
-  TEST_COMPARE (WEXITSTATUS (status), 0);
+  TEST_COMPARE (WAITID (P_ALL, 0, &sinfo, WEXITED), 0);
+  TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+  TEST_COMPARE (sinfo.si_status, 0);
 }
 
 static void
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 594a5dc53e..6809b1eb1c 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -62,6 +62,7 @@ sysdep_routines += \
   clock_adjtime \
   clone \
   clone-internal \
+  clone-pidfd-support \
   clone3 \
   closefrom_fallback \
   convert_scm_timestamps \
@@ -488,12 +489,23 @@ sysdep_headers += \
 sysdep_routines += \
   getcpu \
   oldglob \
+  pidfd_spawn \
+  pidfd_spawnp \
   sched_getcpu \
   # sysdep_routines
 
 tests += \
   tst-affinity \
   tst-affinity-pid \
+  tst-posix_spawn-setsid-pidfd \
+  tst-spawn-chdir-pidfd \
+  tst-spawn-pidfd \
+  tst-spawn2-pidfd \
+  tst-spawn3-pidfd \
+  tst-spawn4-pidfd \
+  tst-spawn5-pidfd \
+  tst-spawn6-pidfd \
+  tst-spawn7-pidfd \
   # tests
 
 tests-static += \
@@ -507,6 +519,14 @@ tests += \
 CFLAGS-fork.c = $(libio-mtsafe)
 CFLAGS-getpid.o = -fomit-frame-pointer
 CFLAGS-getpid.os = -fomit-frame-pointer
+
+CFLAGS-tst-spawn3-pidfd.c += -DOBJPFX=\"$(objpfx)\"
+
+tst-spawn-pidfd-ARGS = -- $(host-test-program-cmd)
+tst-spawn5-pidfd-ARGS = -- $(host-test-program-cmd)
+tst-spawn6-pidfd-ARGS = -- $(host-test-program-cmd)
+tst-spawn7-pidfd-ARGS = -- $(host-test-program-cmd)
+tst-posix_spawn-setsid-pidfd-ARGS = -- $(host-test-program-cmd)
 endif
 
 ifeq ($(subdir),inet)
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index bc59bce42f..28825473ae 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -321,6 +321,10 @@ libc {
     __ppoll64_chk;
 %endif
   }
+  GLIBC_2.38 {
+    pidfd_spawn;
+    pidfd_spawnp;
+  }
   GLIBC_PRIVATE {
     # functions used in other libraries
     __syscall_rt_sigqueueinfo;
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index 0e2d9c3045..bac74ae474 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2665,3 +2665,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index f1bec1978d..dadd302f8d 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2774,6 +2774,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/arc/libc.abilist b/sysdeps/unix/sysv/linux/arc/libc.abilist
index aa874b88d0..0f4f07b6bb 100644
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@@ -2426,3 +2426,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
index afbd57da6f..38e5dcb81a 100644
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -546,6 +546,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
 GLIBC_2.4 _IO_2_1_stdin_ D 0xa0
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index e7364cd3fe..423d20cbb5 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -543,6 +543,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
 GLIBC_2.4 _IO_2_1_stdin_ D 0xa0
diff --git a/sysdeps/unix/sysv/linux/bits/spawn_ext.h b/sysdeps/unix/sysv/linux/bits/spawn_ext.h
new file mode 100644
index 0000000000..ec56923d88
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/spawn_ext.h
@@ -0,0 +1,45 @@
+/* POSIX spawn extensions.   Linux version.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SPAWN_H
+# error "Never include <bits/spawn-ext.h> directly; use <spawn.h> instead."
+#endif
+
+__BEGIN_DECLS
+
+#ifdef __USE_GNU
+
+extern int pidfd_spawn (int *__restrict __pidfd,
+			const char *__restrict __file,
+			const posix_spawn_file_actions_t *__restrict __facts,
+			const posix_spawnattr_t *__restrict __attrp,
+			char *const __argv[__restrict_arr],
+			char *const __envp[__restrict_arr])
+    __nonnull ((2, 5));
+
+extern int pidfd_spawnp (int *__restrict __pidfd,
+			 const char *__restrict __path,
+			 const posix_spawn_file_actions_t *__restrict __facts,
+			 const posix_spawnattr_t *__restrict __attrp,
+			 char *const __argv[__restrict_arr],
+			 char *const __envp[__restrict_arr])
+    __nonnull ((2, 5));
+
+#endif /* __USE_GNU */
+
+__END_DECLS
diff --git a/sysdeps/unix/sysv/linux/clone-pidfd-support.c b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
new file mode 100644
index 0000000000..4bf2317c17
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
@@ -0,0 +1,58 @@
+/* Check if kernel supports PID file descriptors.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <atomic.h>
+#include <sys/wait.h>
+#include <sysdep.h>
+
+/* The PID file descriptors was added during multiple releases:
+   - Linux 5.2 added CLONE_PIDFD support for clone and __clone_pidfd_supported
+     syscall.
+   - Linux 5.3 added support for poll and CLONE_PIDFD for clone3.
+   - Linux 5.4 added P_PIDFD support on waitid.
+
+   For internal usage on spawn and fork, it only make sense to return a file
+   descriptor if caller can actually waitid on it.  */
+bool
+__clone_pidfd_supported (void)
+{
+  static int supported = 0;
+  int state = atomic_load_relaxed (&supported);
+  if (state == 0)
+    {
+      /* Linux define the maximum allocated file descriptor value as
+	 0x7fffffc0 (from fs/file.c):
+
+         #define __const_min(x, y) ((x) < (y) ? (x) : (y))
+         unsigned int sysctl_nr_open_max =
+	   __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
+
+	 So it can detect whther kernel support all pidd support by using
+	 using a valid but never allocated file descriptor: if is not
+	 supported waitid will return EINVAL, otherwise EBADF.
+
+         Also tThe waitid is a cancellation entrypoint, so issue the syscall
+	 directly.  */
+      int r = INTERNAL_SYSCALL_CALL (waitid, P_PIDFD, INT_MAX, NULL,
+				     WEXITED | WNOHANG, NULL);
+      state = r == -EBADF ? 1 : -1;
+      atomic_store_relaxed (&supported, state);
+    }
+
+  return state == 1;
+}
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index 913fa59215..488418d14e 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2702,3 +2702,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index 43af3a9811..75d495e1c7 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2651,6 +2651,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index af72f8fab0..e53877c52a 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2835,6 +2835,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index 48cbb0fa50..5ed2b1ebf4 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -2600,6 +2600,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
index c15884bb0b..d050fbf6d0 100644
--- a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
@@ -2186,3 +2186,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 3738db81df..6465af266c 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -547,6 +547,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0x98
 GLIBC_2.4 _IO_2_1_stdin_ D 0x98
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index ed13627752..00013cc564 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2778,6 +2778,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index 8357738621..34085d81ab 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2751,3 +2751,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
index 58c5da583d..b26b116f1f 100644
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2748,3 +2748,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index d3741945cd..c86418d156 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2743,6 +2743,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 5319fdc204..3c6f8f4d60 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -2741,6 +2741,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index 1743ea6eb9..8dfa065638 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2749,6 +2749,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index 9b1f53c6ac..0ca815f2cd 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2651,6 +2651,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index ae1c6ca1b5..a1e0f772c6 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2790,3 +2790,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/or1k/libc.abilist b/sysdeps/unix/sysv/linux/or1k/libc.abilist
index a7c572c947..91cd6075b9 100644
--- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
+++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
@@ -2172,3 +2172,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/pidfd_spawn.c b/sysdeps/unix/sysv/linux/pidfd_spawn.c
new file mode 100644
index 0000000000..9f4a5780e6
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/pidfd_spawn.c
@@ -0,0 +1,30 @@
+/* pidfd_spawn - Spawn a process and return a pid file descriptor.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <spawn.h>
+#include "spawn_int.h"
+
+int
+pidfd_spawn (int *pidfd, const char *path,
+	     const posix_spawn_file_actions_t *file_actions,
+	     const posix_spawnattr_t *attrp, char *const argv[],
+	     char *const envp[])
+{
+  return __spawni (pidfd, path, file_actions, attrp, argv, envp,
+		   SPAWN_XFLAGS_RET_PIDFD);
+}
diff --git a/sysdeps/unix/sysv/linux/pidfd_spawnp.c b/sysdeps/unix/sysv/linux/pidfd_spawnp.c
new file mode 100644
index 0000000000..c8260fcd01
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/pidfd_spawnp.c
@@ -0,0 +1,30 @@
+/* pidfd_spawnp - Spawn a process and return a pid file descriptor.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <spawn.h>
+#include "spawn_int.h"
+
+int
+pidfd_spawnp (int *pidfd, const char *path,
+	      const posix_spawn_file_actions_t *file_actions,
+	      const posix_spawnattr_t *attrp, char *const argv[],
+	      char *const envp[])
+{
+  return __spawni (pidfd, path, file_actions, attrp, argv, envp,
+		   SPAWN_XFLAGS_USE_PATH | SPAWN_XFLAGS_RET_PIDFD);
+}
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 074fa031a7..21244ece27 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -2817,6 +2817,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index dfcb4bd2d5..238d00998b 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -2850,6 +2850,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index 63bbccf3f9..36fb9b57ac 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2571,6 +2571,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index ab85fd61ef..0c25995661 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2885,3 +2885,5 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
index b716f5c763..cda030f623 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@@ -2428,3 +2428,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index 774e777b65..bd20c202fb 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2628,3 +2628,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index 8625135c48..a1e9247f72 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -2815,6 +2815,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index d00c7eb262..b80a131bde 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2608,6 +2608,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
index b63037241d..496a0185b6 100644
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2658,6 +2658,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index d80055617d..3e0d858d08 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2655,6 +2655,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index 5be55c11d2..84dcda8db2 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -2810,6 +2810,8 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index 475fdaae15..1688a0a7e9 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2623,6 +2623,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
index bc321d4c58..2d2aed7e94 100644
--- a/sysdeps/unix/sysv/linux/spawni.c
+++ b/sysdeps/unix/sysv/linux/spawni.c
@@ -68,6 +68,7 @@ struct posix_spawn_args
   int xflags;
   bool use_clone3;
   int err;
+  int pidfd;
 };
 
 /* Older version requires that shell script without shebang definition
@@ -309,7 +310,7 @@ fail:
 /* Spawn a new process executing PATH with the attributes describes in *ATTRP.
    Before running the process perform the actions described in FILE-ACTIONS. */
 static int
-__spawnix (pid_t * pid, const char *file,
+__spawnix (int *pid, const char *file,
 	   const posix_spawn_file_actions_t * file_actions,
 	   const posix_spawnattr_t * attrp, char *const argv[],
 	   char *const envp[], int xflags,
@@ -319,6 +320,15 @@ __spawnix (pid_t * pid, const char *file,
   struct posix_spawn_args args;
   int ec;
 
+  bool use_pidfd = xflags & SPAWN_XFLAGS_RET_PIDFD;
+
+  /* For CLONE_PIDFD, older kernel might not fail with unsupported flags or
+     some version might not support waitid (P_PIDFD).  So to avoid the need
+     to handle the error on the helper process, check for full pidfd
+     support.  */
+  if (use_pidfd && !__clone_pidfd_supported ())
+    return ENOSYS;
+
   /* To avoid imposing hard limits on posix_spawn{p} the total number of
      arguments is first calculated to allocate a mmap to hold all possible
      values.  */
@@ -368,6 +378,7 @@ __spawnix (pid_t * pid, const char *file,
   args.argv = argv;
   args.argc = argc;
   args.envp = envp;
+  args.pidfd = 0;
   args.xflags = xflags;
 
   internal_signal_block_all (&args.oldmask);
@@ -384,10 +395,13 @@ __spawnix (pid_t * pid, const char *file,
     {
       /* Unsupported flags like CLONE_CLEAR_SIGHAND will be cleared up by
 	 __clone_internal_fallback.  */
-      .flags = CLONE_CLEAR_SIGHAND | CLONE_VM | CLONE_VFORK,
+      .flags = CLONE_CLEAR_SIGHAND | CLONE_VM | CLONE_VFORK
+	       | (use_pidfd ? CLONE_PIDFD : 0),
       .exit_signal = SIGCHLD,
       .stack = (uintptr_t) stack,
       .stack_size = stack_size,
+      .pidfd = use_pidfd ? (uintptr_t) &args.pidfd : 0,
+      .parent_tid = use_pidfd ? (uintptr_t) &args.pidfd : 0,
     };
 #ifdef HAVE_CLONE3_WRAPPER
   args.use_clone3 = true;
@@ -429,7 +443,7 @@ __spawnix (pid_t * pid, const char *file,
   __munmap (stack, stack_size);
 
   if ((ec == 0) && (pid != NULL))
-    *pid = new_pid;
+    *pid = use_pidfd ? args.pidfd : new_pid;
 
   internal_signal_restore_set (&args.oldmask);
 
diff --git a/sysdeps/unix/sysv/linux/tst-posix_spawn-setsid-pidfd.c b/sysdeps/unix/sysv/linux/tst-posix_spawn-setsid-pidfd.c
new file mode 100644
index 0000000000..4372833f07
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-posix_spawn-setsid-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-posix_spawn-setsid.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn-chdir-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn-chdir-pidfd.c
new file mode 100644
index 0000000000..019527b31b
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn-chdir-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn-chdir.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn-pidfd.c
new file mode 100644
index 0000000000..c430995af8
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn-pidfd.h b/sysdeps/unix/sysv/linux/tst-spawn-pidfd.h
new file mode 100644
index 0000000000..ea51c22447
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn-pidfd.h
@@ -0,0 +1,63 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <spawn.h>
+#include <support/check.h>
+
+#define PID_T_TYPE int
+
+/* Call posix_spawn with POSIX_SPAWN_PIDFD set.  */
+static inline int
+pidfd_spawn_check (int *pidfd, const char *path,
+		   const posix_spawn_file_actions_t *fa,
+		   const posix_spawnattr_t *attr, char *const argv[],
+		   char *const envp[])
+{
+  int r = pidfd_spawn (pidfd, path, fa, attr, argv, envp);
+  if (r == ENOSYS)
+    FAIL_UNSUPPORTED ("kernel does not support CLONE_PIDFD clone flag");
+  return r;
+}
+
+#define POSIX_SPAWN(__pidfd, __path, __actions, __attr, __argv, __envp)	     \
+  pidfd_spawn_check (__pidfd, __path, __actions, __attr, __argv, __envp)
+
+static inline int
+pidfd_spawnp_check (int *pidfd, const char *file,
+		    const posix_spawn_file_actions_t *fa,
+		    const posix_spawnattr_t *attr,
+		    char *const argv[], char *const envp[])
+{
+  int r = pidfd_spawnp (pidfd, file, fa, attr, argv, envp);
+  if (r == ENOSYS)
+    FAIL_UNSUPPORTED ("kernel does not support CLONE_PIDFD clone flag");
+  return r;
+}
+
+#define POSIX_SPAWNP(__child, __path, __actions, __attr, __argv, __envp) \
+  pidfd_spawnp_check (__child, __path, __actions, __attr, __argv, __envp)
+
+#define WAITID(__idtype, __id, __info, __opts)				     \
+  ({									     \
+     __typeof (__idtype) __new_idtype = __idtype == P_PID		     \
+					? P_PIDFD : __idtype;		     \
+     waitid (__new_idtype, __id, __info, __opts);			     \
+  })
+
+#define TST_SPAWN_PIDFD 1
diff --git a/sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c
new file mode 100644
index 0000000000..03ba7a3d15
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn2-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn2.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c
new file mode 100644
index 0000000000..8ad9a16854
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn3-pidfd.c
@@ -0,0 +1,20 @@
+/* Check posix_spawn add file actions.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn3.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c
new file mode 100644
index 0000000000..83922da7d1
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn4-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn4.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c
new file mode 100644
index 0000000000..149c352bf8
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn5-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn5.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c
new file mode 100644
index 0000000000..d3f5859457
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn6-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn6.c>
diff --git a/sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c b/sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c
new file mode 100644
index 0000000000..3aec86bec2
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-spawn7-pidfd.c
@@ -0,0 +1,20 @@
+/* Tests for spawn pidfd extension.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <tst-spawn-pidfd.h>
+#include <posix/tst-spawn7.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 6cfb928bc8..b7422d5747 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2574,6 +2574,8 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index c735097172..90680bc1d7 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2680,3 +2680,5 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_spawn F
+GLIBC_2.38 pidfd_spawnp F
-- 
2.34.1


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [PATCH v4 2/3] posix: Add pidfd_fork
  2023-05-17 17:35 [PATCH v4 0/3] Add pidfd_spawn, pidfd_spawnp, pidfd_fork, and pidfd_getpid Adhemerval Zanella
  2023-05-17 17:35 ` [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349) Adhemerval Zanella
@ 2023-05-17 17:35 ` Adhemerval Zanella
  2023-05-22 10:12   ` Florian Weimer
  2023-05-17 17:35 ` [PATCH v4 3/3] linux: Add pidfd_getpid Adhemerval Zanella
  2 siblings, 1 reply; 13+ messages in thread
From: Adhemerval Zanella @ 2023-05-17 17:35 UTC (permalink / raw)
  To: libc-alpha, Luca Boccassi, Florian Weimer, Philip Withnall

Returning a pidfd allows a process to keep a race-free handle to a
child process, otherwise the caller will need to either use pidfd_open
(which still might be subject to TOCTOU) or keep using the old racy
interface.

The implementation makes sure that kernel must support the complete
pidfd interface, meaning that waitid (P_PIDFD) should be supported.
It ensure that non racy workaround is required (such as reading procfs
fdinfo pid to use along with old wait interfaces).  If kernel does
not have the required support the interface returns -1 and set errno
to ENOSYS.

The interface is:

  int pidfd_fork (unsigned int flags)

The kernel already sets O_CLOEXEC as default and it follow fork/_Fork
convention on returning a positive or negative value to the parent
(with negative indicating an error) and zero to the child.

Similar to fork, pidfd_fork also runs the pthread_atfork handlers
It can be change by using PIDFDFORK_ASYNCSAFE flag, which make
pidfd_fork acts a _Fork.

Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PID or waitid
support), Linux 5.15 (only clone support), and Linux 5.19 (full
support including clone3).
---
 NEWS                                          |   5 +
 manual/process.texi                           |  47 ++++--
 posix/Makefile                                |   3 +-
 posix/fork-internal.c                         | 125 +++++++++++++++
 posix/fork-internal.h                         |  29 ++++
 posix/fork.c                                  |  98 +-----------
 sysdeps/nptl/_Fork.c                          |   2 +-
 sysdeps/unix/sysv/linux/Makefile              |   3 +
 sysdeps/unix/sysv/linux/Versions              |   1 +
 sysdeps/unix/sysv/linux/aarch64/libc.abilist  |   1 +
 sysdeps/unix/sysv/linux/alpha/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/arc/libc.abilist      |   1 +
 sysdeps/unix/sysv/linux/arch-fork.h           |  16 +-
 sysdeps/unix/sysv/linux/arm/be/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/arm/le/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/csky/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/hppa/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/i386/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/ia64/libc.abilist     |   1 +
 .../sysv/linux/loongarch/lp64/libc.abilist    |   1 +
 .../sysv/linux/m68k/coldfire/libc.abilist     |   1 +
 .../unix/sysv/linux/m68k/m680x0/libc.abilist  |   1 +
 .../sysv/linux/microblaze/be/libc.abilist     |   1 +
 .../sysv/linux/microblaze/le/libc.abilist     |   1 +
 .../sysv/linux/mips/mips32/fpu/libc.abilist   |   1 +
 .../sysv/linux/mips/mips32/nofpu/libc.abilist |   1 +
 .../sysv/linux/mips/mips64/n32/libc.abilist   |   1 +
 .../sysv/linux/mips/mips64/n64/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/nios2/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/or1k/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/pidfd_fork.c          |  76 +++++++++
 .../linux/powerpc/powerpc32/fpu/libc.abilist  |   1 +
 .../powerpc/powerpc32/nofpu/libc.abilist      |   1 +
 .../linux/powerpc/powerpc64/be/libc.abilist   |   1 +
 .../linux/powerpc/powerpc64/le/libc.abilist   |   1 +
 .../unix/sysv/linux/riscv/rv32/libc.abilist   |   1 +
 .../unix/sysv/linux/riscv/rv64/libc.abilist   |   1 +
 .../unix/sysv/linux/s390/s390-32/libc.abilist |   1 +
 .../unix/sysv/linux/s390/s390-64/libc.abilist |   1 +
 sysdeps/unix/sysv/linux/sh/be/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/sh/le/libc.abilist    |   1 +
 .../sysv/linux/sparc/sparc32/libc.abilist     |   1 +
 .../sysv/linux/sparc/sparc64/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/sys/pidfd.h           |  13 ++
 sysdeps/unix/sysv/linux/tst-pidfd_fork.c      | 150 ++++++++++++++++++
 .../unix/sysv/linux/x86_64/64/libc.abilist    |   1 +
 .../unix/sysv/linux/x86_64/x32/libc.abilist   |   1 +
 47 files changed, 488 insertions(+), 114 deletions(-)
 create mode 100644 posix/fork-internal.c
 create mode 100644 posix/fork-internal.h
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_fork.c
 create mode 100644 sysdeps/unix/sysv/linux/tst-pidfd_fork.c

diff --git a/NEWS b/NEWS
index 2c49eaf373..af647c7c46 100644
--- a/NEWS
+++ b/NEWS
@@ -42,6 +42,11 @@ Major new features:
   The pidfd functionality avoid the issue of PID reuse with traditional
   posix_spawn interface.
 
+* On Linux, the pidfd_fork has been added.  It has a similar semantic
+  as fork or _Fork, where it clone the calling process.  However instead of
+  return a process ID, it returns a file descriptor that can be used along
+  other pidfd functions.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * In the Linux kernel for the hppa/parisc architecture some of the
diff --git a/manual/process.texi b/manual/process.texi
index 927aebbe3d..93e0ab5fb7 100644
--- a/manual/process.texi
+++ b/manual/process.texi
@@ -137,12 +137,12 @@ creating a process and making it run another program.
 @cindex subprocess
 A new processes is created when one of the functions
 @code{posix_spawn}, @code{fork}, @code{_Fork}, @code{vfork}, or
-@code{pidfd_spawn} is called.  (The @code{system} and @code{popen} also
-create new processes internally.)  Due to the name of the @code{fork}
-function, the act of creating a new process is sometimes called
-@dfn{forking} a process.  Each new process (the @dfn{child process} or
-@dfn{subprocess}) is allocated a process ID, distinct from the process
-ID of the parent process.  @xref{Process Identification}.
+@code{pidfd_spawn}, or @code{pidfd_fork} is called.  (The @code{system}
+and @code{popen} also create new processes internally.)  Due to the name
+of the @code{fork} function, the act of creating a new process is
+sometimes called @dfn{forking} a process.  Each new process (the
+@dfn{child process} or @dfn{subprocess}) is allocated a process ID,
+distinct from the process ID of the parent process.  @xref{Process Identification}.
 
 After forking a child process, both the parent and child processes
 continue to execute normally.  If you want your program to wait for a
@@ -153,10 +153,10 @@ limited information about why the child terminated---for example, its
 exit status code.
 
 A newly forked child process continues to execute the same program as
-its parent process, at the point where the @code{fork} or @code{_Fork}
-call returns.  You can use the return value from @code{fork} or
-@code{_Fork} to tell whether the program is running in the parent process
-or the child.
+its parent process, at the point where the @code{fork}, @code{_Fork},
+or @code{pidfd_fork} call returns.  You can use the return value from
+@code{fork}, @code{_Fork}, or @code{pidfd_fork} to tell whether the
+program is running in the parent process or the child.
 
 @cindex process image
 Having several processes run the same program is only occasionally
@@ -362,6 +362,33 @@ the proper precautions for using @code{vfork}, your program will still
 work even if the system uses @code{fork} instead.
 @end deftypefun
 
+@deftypefun int pidfd_fork (unsigned int @var{flags})
+@standards{GNU, sys/pidfd.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+The @code{fork} function is similar to @code{fork} but return a file
+descriptor instead of process ID.
+
+If the operation is sucessful, there are both parent and child processes
+and both see @code{pidfd_fork} return, but with different values: it return
+a value of @code{0} in the child process and returns a file descriptor to
+child's process int the parent process.  Although the value of @code{0} clashes
+with @code{STDIN_FILENO}, it also assumed that stardand input is always
+available so a conformant application will never see a the @code{0} stream
+being returned to parent as a valid file descriptor.
+
+The @var{flags} argument should be either zero, or the bitwise OR of some of the
+following flags:
+
+@table @code
+@item PIDFDFORK_ASYNCSAFE
+Acts as @code{_Fork}, where it does not invoke any callbacks registered with
+@code{pthread_atfork}, nor does it reset internal state or locks (such as the
+@code{malloc} locks).
+@end table
+@end deftypefun
+
+This function is specific to Linux.
+
 @node Executing a File
 @section Executing a File
 @cindex executing a file
diff --git a/posix/Makefile b/posix/Makefile
index 4016a7758a..c4837589fd 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -84,6 +84,7 @@ routines := \
   fexecve \
   fnmatch \
   fork \
+  fork-internal \
   fpathconf \
   gai_strerror \
   get_child_max \
@@ -579,7 +580,7 @@ CFLAGS-execl.os = -fomit-frame-pointer
 CFLAGS-execvp.os = -fomit-frame-pointer
 CFLAGS-execlp.os = -fomit-frame-pointer
 CFLAGS-nanosleep.c += -fexceptions -fasynchronous-unwind-tables
-CFLAGS-fork.c = $(libio-mtsafe) $(config-cflags-wno-ignored-attributes)
+CFLAGS-fork-internal.c = $(libio-mtsafe) $(config-cflags-wno-ignored-attributes)
 
 tstgetopt-ARGS = -a -b -cfoobar --required foobar --optional=bazbug \
 		--none random --col --color --colour
diff --git a/posix/fork-internal.c b/posix/fork-internal.c
new file mode 100644
index 0000000000..be0d3219af
--- /dev/null
+++ b/posix/fork-internal.c
@@ -0,0 +1,125 @@
+/* Internal fork definitions.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <fork.h>
+#include <fork-internal.h>
+#include <ldsodefs.h>
+#include <libio/libioP.h>
+#include <malloc/malloc-internal.h>
+#include <register-atfork.h>
+#include <stdio-lock.h>
+#include <unwind-link.h>
+
+static void
+fresetlockfiles (void)
+{
+  _IO_ITER i;
+
+  for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))
+    if ((_IO_iter_file (i)->_flags & _IO_USER_LOCK) == 0)
+      _IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));
+}
+
+uint64_t
+__fork_pre (bool multiple_threads, struct nss_database_data *nss_database_data)
+{
+  uint64_t lastrun = __run_prefork_handlers (multiple_threads);
+
+  /* If we are not running multiple threads, we do not have to
+     preserve lock state.  If fork runs from a signal handler, only
+     async-signal-safe functions can be used in the child.  These data
+     structures are only used by unsafe functions, so their state does
+     not matter if fork was called from a signal handler.  */
+  if (multiple_threads)
+    {
+      call_function_static_weak (__nss_database_fork_prepare_parent,
+				 nss_database_data);
+
+      _IO_list_lock ();
+
+      /* Acquire malloc locks.  This needs to come last because fork
+	 handlers may use malloc, and the libio list lock has an
+	 indirect malloc dependency as well (via the getdelim
+	 function).  */
+      call_function_static_weak (__malloc_fork_lock_parent);
+    }
+
+  return lastrun;
+}
+
+void
+__fork_pos (int state, uint64_t lastrun, bool multiple_threads,
+	    struct nss_database_data *nss_database_data)
+{
+  if (state == 0)
+    {
+      fork_system_setup ();
+
+      /* Reset the lock state in the multi-threaded case.  */
+      if (multiple_threads)
+	{
+	  __libc_unwind_link_after_fork ();
+
+	  fork_system_setup_after_fork ();
+
+	  /* Release malloc locks.  */
+	  call_function_static_weak (__malloc_fork_unlock_child);
+
+	  /* Reset the file list.  These are recursive mutexes.  */
+	  fresetlockfiles ();
+
+	  /* Reset locks in the I/O code.  */
+	  _IO_list_resetlock ();
+
+	  call_function_static_weak (__nss_database_fork_subprocess,
+				     nss_database_data);
+	}
+
+      /* Reset the lock the dynamic loader uses to protect its data.  */
+      __rtld_lock_initialize (GL(dl_load_lock));
+
+      /* Reset the lock protecting dynamic TLS related data.  */
+      __rtld_lock_initialize (GL(dl_load_tls_lock));
+
+      reclaim_stacks ();
+
+      /* Run the handlers registered for the child.  */
+      __run_postfork_handlers (atfork_run_child, multiple_threads, lastrun);
+    }
+  else
+    {
+      /* If _Fork failed, preserve its errno value.  */
+      int save_errno = errno;
+
+      /* Release acquired locks in the multi-threaded case.  */
+      if (multiple_threads)
+	{
+	  /* Release malloc locks, parent process variant.  */
+	  call_function_static_weak (__malloc_fork_unlock_parent);
+
+	  /* We execute this even if the 'fork' call failed.  */
+	  _IO_list_unlock ();
+	}
+
+      /* Run the handlers registered for the parent.  */
+      __run_postfork_handlers (atfork_run_parent, multiple_threads, lastrun);
+
+      if (state < 0)
+	__set_errno (save_errno);
+    }
+}
diff --git a/posix/fork-internal.h b/posix/fork-internal.h
new file mode 100644
index 0000000000..3814d851c4
--- /dev/null
+++ b/posix/fork-internal.h
@@ -0,0 +1,29 @@
+/* Internal fork definitions.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _FORK_INTERNAL_H
+#define _FORK_INTERNAL_H
+
+#include <stdint.h>
+#include <nss/nss_database.h>
+
+uint64_t __fork_pre (bool, struct nss_database_data *) attribute_hidden;
+void __fork_pos (int, uint64_t, bool, struct nss_database_data *)
+  attribute_hidden;
+
+#endif
diff --git a/posix/fork.c b/posix/fork.c
index b4aaa9fa6d..4423cc5792 100644
--- a/posix/fork.c
+++ b/posix/fork.c
@@ -16,25 +16,10 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <fork.h>
-#include <libio/libioP.h>
-#include <ldsodefs.h>
-#include <malloc/malloc-internal.h>
-#include <nss/nss_database.h>
-#include <register-atfork.h>
-#include <stdio-lock.h>
+#include <fork-internal.h>
 #include <sys/single_threaded.h>
 #include <unwind-link.h>
-
-static void
-fresetlockfiles (void)
-{
-  _IO_ITER i;
-
-  for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))
-    if ((_IO_iter_file (i)->_flags & _IO_USER_LOCK) == 0)
-      _IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));
-}
+#include <unistd.h>
 
 pid_t
 __libc_fork (void)
@@ -46,89 +31,14 @@ __libc_fork (void)
      best effort to make is async-signal-safe at least for single-thread
      case.  */
   bool multiple_threads = !SINGLE_THREAD_P;
-  uint64_t lastrun;
-
-  lastrun = __run_prefork_handlers (multiple_threads);
 
   struct nss_database_data nss_database_data;
 
-  /* If we are not running multiple threads, we do not have to
-     preserve lock state.  If fork runs from a signal handler, only
-     async-signal-safe functions can be used in the child.  These data
-     structures are only used by unsafe functions, so their state does
-     not matter if fork was called from a signal handler.  */
-  if (multiple_threads)
-    {
-      call_function_static_weak (__nss_database_fork_prepare_parent,
-				 &nss_database_data);
-
-      _IO_list_lock ();
-
-      /* Acquire malloc locks.  This needs to come last because fork
-	 handlers may use malloc, and the libio list lock has an
-	 indirect malloc dependency as well (via the getdelim
-	 function).  */
-      call_function_static_weak (__malloc_fork_lock_parent);
-    }
+  uint64_t lastrun = __fork_pre (multiple_threads, &nss_database_data);
 
   pid_t pid = _Fork ();
 
-  if (pid == 0)
-    {
-      fork_system_setup ();
-
-      /* Reset the lock state in the multi-threaded case.  */
-      if (multiple_threads)
-	{
-	  __libc_unwind_link_after_fork ();
-
-	  fork_system_setup_after_fork ();
-
-	  /* Release malloc locks.  */
-	  call_function_static_weak (__malloc_fork_unlock_child);
-
-	  /* Reset the file list.  These are recursive mutexes.  */
-	  fresetlockfiles ();
-
-	  /* Reset locks in the I/O code.  */
-	  _IO_list_resetlock ();
-
-	  call_function_static_weak (__nss_database_fork_subprocess,
-				     &nss_database_data);
-	}
-
-      /* Reset the lock the dynamic loader uses to protect its data.  */
-      __rtld_lock_initialize (GL(dl_load_lock));
-
-      /* Reset the lock protecting dynamic TLS related data.  */
-      __rtld_lock_initialize (GL(dl_load_tls_lock));
-
-      reclaim_stacks ();
-
-      /* Run the handlers registered for the child.  */
-      __run_postfork_handlers (atfork_run_child, multiple_threads, lastrun);
-    }
-  else
-    {
-      /* If _Fork failed, preserve its errno value.  */
-      int save_errno = errno;
-
-      /* Release acquired locks in the multi-threaded case.  */
-      if (multiple_threads)
-	{
-	  /* Release malloc locks, parent process variant.  */
-	  call_function_static_weak (__malloc_fork_unlock_parent);
-
-	  /* We execute this even if the 'fork' call failed.  */
-	  _IO_list_unlock ();
-	}
-
-      /* Run the handlers registered for the parent.  */
-      __run_postfork_handlers (atfork_run_parent, multiple_threads, lastrun);
-
-      if (pid < 0)
-	__set_errno (save_errno);
-    }
+  __fork_pos (pid, lastrun, multiple_threads, &nss_database_data);
 
   return pid;
 }
diff --git a/sysdeps/nptl/_Fork.c b/sysdeps/nptl/_Fork.c
index f8322ae557..aa99e05b5b 100644
--- a/sysdeps/nptl/_Fork.c
+++ b/sysdeps/nptl/_Fork.c
@@ -22,7 +22,7 @@
 pid_t
 _Fork (void)
 {
-  pid_t pid = arch_fork (&THREAD_SELF->tid);
+  pid_t pid = arch_fork (0, NULL, &THREAD_SELF->tid);
   if (pid == 0)
     {
       struct pthread *self = THREAD_SELF;
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 6809b1eb1c..675c226a99 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -489,14 +489,17 @@ sysdep_headers += \
 sysdep_routines += \
   getcpu \
   oldglob \
+  pidfd_fork \
   pidfd_spawn \
   pidfd_spawnp \
   sched_getcpu \
+  sched_getcpu \
   # sysdep_routines
 
 tests += \
   tst-affinity \
   tst-affinity-pid \
+  tst-pidfd_fork \
   tst-posix_spawn-setsid-pidfd \
   tst-spawn-chdir-pidfd \
   tst-spawn-pidfd \
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 28825473ae..7e4109e9c5 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -322,6 +322,7 @@ libc {
 %endif
   }
   GLIBC_2.38 {
+    pidfd_fork;
     pidfd_spawn;
     pidfd_spawnp;
   }
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index bac74ae474..dbf7c44319 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2665,5 +2665,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index dadd302f8d..a9d6ffce14 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2774,6 +2774,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/arc/libc.abilist b/sysdeps/unix/sysv/linux/arc/libc.abilist
index 0f4f07b6bb..c08d548556 100644
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@@ -2426,5 +2426,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/arch-fork.h b/sysdeps/unix/sysv/linux/arch-fork.h
index 84e5ef5a7f..ce08fdb99e 100644
--- a/sysdeps/unix/sysv/linux/arch-fork.h
+++ b/sysdeps/unix/sysv/linux/arch-fork.h
@@ -32,24 +32,24 @@
    override it with one of the supported calling convention (check generic
    kernel-features.h for the clone abi variants).  */
 static inline pid_t
-arch_fork (void *ctid)
+arch_fork (int flags, void *ptid, void *ctid)
 {
-  const int flags = CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD;
   long int ret;
+  flags |= CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD;
 #ifdef __ASSUME_CLONE_BACKWARDS
 # ifdef INLINE_CLONE_SYSCALL
-  ret = INLINE_CLONE_SYSCALL (flags, 0, NULL, 0, ctid);
+  ret = INLINE_CLONE_SYSCALL (flags, 0, ptid, 0, ctid);
 # else
-  ret = INLINE_SYSCALL_CALL (clone, flags, 0, NULL, 0, ctid);
+  ret = INLINE_SYSCALL_CALL (clone, flags, 0, ptid, 0, ctid);
 # endif
 #elif defined(__ASSUME_CLONE_BACKWARDS2)
-  ret = INLINE_SYSCALL_CALL (clone, 0, flags, NULL, ctid, 0);
+  ret = INLINE_SYSCALL_CALL (clone, 0, flags, ptid, ctid, 0);
 #elif defined(__ASSUME_CLONE_BACKWARDS3)
-  ret = INLINE_SYSCALL_CALL (clone, flags, 0, 0, NULL, ctid, 0);
+  ret = INLINE_SYSCALL_CALL (clone, flags, 0, 0, ptid, ctid, 0);
 #elif defined(__ASSUME_CLONE2)
-  ret = INLINE_SYSCALL_CALL (clone2, flags, 0, 0, NULL, ctid, 0);
+  ret = INLINE_SYSCALL_CALL (clone2, flags, 0, 0, ptid, ctid, 0);
 #elif defined(__ASSUME_CLONE_DEFAULT)
-  ret = INLINE_SYSCALL_CALL (clone, flags, 0, NULL, ctid, 0);
+  ret = INLINE_SYSCALL_CALL (clone, flags, 0, ptid, ctid, 0);
 #else
 # error "Undefined clone variant"
 #endif
diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
index 38e5dcb81a..f348336ee7 100644
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -546,6 +546,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index 423d20cbb5..5aed593521 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -543,6 +543,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index 488418d14e..8a7022aaa8 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2702,5 +2702,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index 75d495e1c7..e2ac6949df 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2651,6 +2651,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index e53877c52a..5e8d49fc1f 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2835,6 +2835,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index 5ed2b1ebf4..3cd3c80334 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -2600,6 +2600,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
index d050fbf6d0..0965db2ff0 100644
--- a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
@@ -2186,5 +2186,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 6465af266c..1ec24886a3 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -547,6 +547,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 00013cc564..239b1d70be 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2778,6 +2778,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index 34085d81ab..dd41d63394 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2751,5 +2751,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
index b26b116f1f..55c3dcd471 100644
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2748,5 +2748,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index c86418d156..295e4d8608 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2743,6 +2743,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 3c6f8f4d60..19fb1aebe7 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -2741,6 +2741,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index 8dfa065638..2dd6ef5416 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2749,6 +2749,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index 0ca815f2cd..6445d27220 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2651,6 +2651,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index a1e0f772c6..c1cc5134c9 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2790,5 +2790,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/or1k/libc.abilist b/sysdeps/unix/sysv/linux/or1k/libc.abilist
index 91cd6075b9..293643346a 100644
--- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
+++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
@@ -2172,5 +2172,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/pidfd_fork.c b/sysdeps/unix/sysv/linux/pidfd_fork.c
new file mode 100644
index 0000000000..a3ef48ce77
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/pidfd_fork.c
@@ -0,0 +1,76 @@
+/* pidfd_fork - Duplicated calling process and return a process file
+   descriptor.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <arch-fork.h>
+#include <clone_internal.h>
+#include <fork-internal.h>
+#include <sys/pidfd.h>
+
+static int
+forkfd (void)
+{
+  /* The kernel should not change the pidfd for the child, and the returning
+     value on the parent is always larger than 0 (since a new file descriptor
+     is always opened with CLONE_PIDFD is the kernel supports it.  */
+  int pidfd = 0;
+  int ret = arch_fork (CLONE_PIDFD, &pidfd, &THREAD_SELF->tid);
+  if (ret < 0)
+    return -1;
+  else if (ret == 0)
+    {
+      struct pthread *self = THREAD_SELF;
+
+      /* Initialize the robust mutex, check _Fork implementation for a full
+	 description why this is required.  */
+#if __PTHREAD_MUTEX_HAVE_PREV
+      self->robust_prev = &self->robust_head;
+#endif
+      self->robust_head.list = &self->robust_head;
+      INTERNAL_SYSCALL_CALL (set_robust_list, &self->robust_head,
+			     sizeof (struct robust_list_head));
+    }
+  return pidfd;
+}
+
+int
+pidfd_fork (unsigned int flags)
+{
+  if (!__clone_pidfd_supported ())
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (ENOSYS);
+
+  if (flags & ~(PIDFDFORK_ASYNCSAFE))
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
+
+  int pidfd;
+  if (!(flags & PIDFDFORK_ASYNCSAFE))
+    {
+      bool multiple_threads = !SINGLE_THREAD_P;
+      struct nss_database_data nss_database_data;
+
+      uint64_t lastrun = __fork_pre (multiple_threads, &nss_database_data);
+      pidfd = forkfd ();
+      /* It follow the usual fork semantic, where a positive or negative
+	 value is returned to parent, and 0 for the child.  */
+      __fork_pos (pidfd, lastrun, multiple_threads, &nss_database_data);
+    }
+  else
+    pidfd = forkfd ();
+
+  return pidfd;
+}
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 21244ece27..03a35e860d 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -2817,6 +2817,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index 238d00998b..a91af4245b 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -2850,6 +2850,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index 36fb9b57ac..c15137b9ad 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2571,6 +2571,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index 0c25995661..12c0f4cfba 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2885,5 +2885,6 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
index cda030f623..9537dac42d 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@@ -2428,5 +2428,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index bd20c202fb..ea72e6b648 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2628,5 +2628,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index a1e9247f72..d6c895b487 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -2815,6 +2815,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index b80a131bde..b375f5a7ab 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2608,6 +2608,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
index 496a0185b6..7b2266ecb3 100644
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2658,6 +2658,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index 3e0d858d08..2f9f732044 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2655,6 +2655,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index 84dcda8db2..144d54ebf2 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -2810,6 +2810,7 @@ GLIBC_2.38 __nldbl___isoc23_vsscanf F
 GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index 1688a0a7e9..bc8bd8ff54 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2623,6 +2623,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/sys/pidfd.h b/sysdeps/unix/sysv/linux/sys/pidfd.h
index 342e593288..1942773957 100644
--- a/sysdeps/unix/sysv/linux/sys/pidfd.h
+++ b/sysdeps/unix/sysv/linux/sys/pidfd.h
@@ -46,4 +46,17 @@ extern int pidfd_getfd (int __pidfd, int __targetfd,
 extern int pidfd_send_signal (int __pidfd, int __sig, siginfo_t *__info,
 			      unsigned int __flags) __THROW;
 
+
+/* Do not issue the pthread_atfork on pidfd_fork.  */
+#define PIDFDFORK_ASYNCSAFE (1U << 1)
+
+/* Clone the calling process, creating an exact copy.
+
+   The __FLAGS can be used to specify whether to run pthread_atfork handlers
+   and reset internal states.  The default is to run it, similar to fork.
+
+   Return -1 for errors, 0 to the new process, and the process file descriptor
+   of the new process to the parent process.  */
+extern int pidfd_fork (unsigned int __flags) __THROW;
+
 #endif /* _PIDFD_H  */
diff --git a/sysdeps/unix/sysv/linux/tst-pidfd_fork.c b/sysdeps/unix/sysv/linux/tst-pidfd_fork.c
new file mode 100644
index 0000000000..32542b8331
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-pidfd_fork.c
@@ -0,0 +1,150 @@
+/* Basic tests for pidfd_fork.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <array_length.h>
+#include <errno.h>
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+#include <sys/pidfd.h>
+#include <sys/wait.h>
+
+#define SIG_PID_EXIT_CODE 20
+
+static bool atfork_prepare_var;
+static bool atfork_parent_var;
+static bool atfork_child_var;
+
+static void
+atfork_prepare (void)
+{
+  atfork_prepare_var = true;
+}
+
+static void
+atfork_parent (void)
+{
+  atfork_parent_var = true;
+}
+
+static void
+atfork_child (void)
+{
+  atfork_child_var = true;
+}
+
+static int
+singlethread_test (unsigned int flags)
+{
+  const char testdata1[] = "abcdefghijklmnopqrtuvwxz";
+  enum { testdatalen1 = array_length (testdata1) };
+  const char testdata2[] = "01234567890";
+  enum { testdatalen2 = array_length (testdata2) };
+
+  pid_t ppid = getpid ();
+
+  int tempfd = create_temp_file ("tst-pidfd_fork", NULL);
+
+  /* Check if the opened file is shared between process by read and write
+     some data on parent and child processes.  */
+  xwrite (tempfd, testdata1, testdatalen1);
+  off_t off = xlseek (tempfd, 0, SEEK_CUR);
+  TEST_COMPARE (off, testdatalen1);
+
+  int pidfd = pidfd_fork (flags);
+  if (pidfd == -1 && errno == ENOSYS)
+    FAIL_UNSUPPORTED ("kernel does not support CLONE_PIDFD clone flag");
+  TEST_VERIFY_EXIT (pidfd != -1);
+
+  if (pidfd == 0)
+    {
+      if (flags & PIDFDFORK_ASYNCSAFE)
+	TEST_VERIFY (!atfork_child_var);
+      else
+	TEST_VERIFY (atfork_child_var);
+
+      TEST_VERIFY_EXIT (getpid () != ppid);
+      TEST_COMPARE (getppid(), ppid);
+
+      TEST_COMPARE (xlseek (tempfd, 0, SEEK_CUR), testdatalen1);
+
+      xlseek (tempfd, 0, SEEK_SET);
+      char buf[testdatalen1];
+      TEST_COMPARE (read (tempfd, buf, sizeof (buf)), testdatalen1);
+      TEST_COMPARE_BLOB (buf, testdatalen1, testdata1, testdatalen1);
+
+      xlseek (tempfd, 0, SEEK_SET);
+      xwrite (tempfd, testdata2, testdatalen2);
+
+      xclose (tempfd);
+
+      _exit (EXIT_SUCCESS);
+    }
+  else
+    TEST_VERIFY_EXIT (pidfd != -1);
+
+  {
+    siginfo_t sinfo;
+    TEST_COMPARE (waitid (P_PIDFD, pidfd, &sinfo, WEXITED), 0);
+    TEST_COMPARE (sinfo.si_code, CLD_EXITED);
+    TEST_COMPARE (sinfo.si_status, 0);
+  }
+
+  TEST_COMPARE (xlseek (tempfd, 0, SEEK_CUR), testdatalen2);
+
+  xlseek (tempfd, 0, SEEK_SET);
+  char buf[testdatalen2];
+  TEST_COMPARE (read (tempfd, buf, sizeof (buf)), testdatalen2);
+
+  TEST_COMPARE_BLOB (buf, testdatalen2, testdata2, testdatalen2);
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  pthread_atfork (atfork_prepare, atfork_parent, atfork_child);
+
+  /* With default flags, pidfd_fork acts as fork and run the pthread_atfork
+     handlers.  */
+  {
+    atfork_prepare_var = atfork_parent_var = atfork_child_var = false;
+    singlethread_test (0);
+    TEST_VERIFY (atfork_prepare_var);
+    TEST_VERIFY (atfork_parent_var);
+    TEST_VERIFY (!atfork_child_var);
+  }
+
+  /* With PIDFDFORK_ASYNCSAFE, pidfd_fork acts as _Fork.  */
+  {
+    atfork_prepare_var = atfork_parent_var = atfork_child_var = false;
+    pthread_atfork (atfork_prepare, atfork_parent, atfork_child);
+    singlethread_test (PIDFDFORK_ASYNCSAFE);
+    TEST_VERIFY (!atfork_prepare_var);
+    TEST_VERIFY (!atfork_parent_var);
+    TEST_VERIFY (!atfork_child_var);
+  }
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index b7422d5747..045205de0c 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2574,6 +2574,7 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 90680bc1d7..5a67604948 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2680,5 +2680,6 @@ GLIBC_2.38 __isoc23_wcstoull F
 GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
+GLIBC_2.38 pidfd_fork F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
-- 
2.34.1


^ permalink raw reply	[flat|nested] 13+ messages in thread
* [PATCH v4 3/3] linux: Add pidfd_getpid
  2023-05-17 17:35 [PATCH v4 0/3] Add pidfd_spawn, pidfd_spawnp, pidfd_fork, and pidfd_getpid Adhemerval Zanella
  2023-05-17 17:35 ` [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349) Adhemerval Zanella
  2023-05-17 17:35 ` [PATCH v4 2/3] posix: Add pidfd_fork Adhemerval Zanella
@ 2023-05-17 17:35 ` Adhemerval Zanella
  2023-05-22 13:00   ` Florian Weimer
  2023-05-22 13:53   ` Joe Simmons-Talbott
  2 siblings, 2 replies; 13+ messages in thread
From: Adhemerval Zanella @ 2023-05-17 17:35 UTC (permalink / raw)
  To: libc-alpha, Luca Boccassi, Florian Weimer, Philip Withnall

This interface allows to obtain the associated pid ID from the
process file descriptor.  It is done by parsing the procps fdinfo
information.  Its prototype is:

   pid_t pidfd_getpid (int fd)

It returns the associated pid or -1 in case of an error and set the
errno accordingly.  The possible errno values are the smae from
open, read, and close (used on procps parsing), along with:

   - EINVAL if the FP is negative (similar to fexecve).

   - EBADF if the FD does not have a PID associated of if the fdinfo
     fields contains a value larger than pid_t.

   - EREMOTE if the PID is in a separate namespace.

   - ESRCH if the process is already terminated.

Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PID or waitid
support), Linux 5.15 (only clone support), and Linux 5.19 (full
support including clone3).
---
 NEWS                                          |   4 +
 manual/process.texi                           |  33 ++++
 sysdeps/unix/sysv/linux/Makefile              |   3 +
 sysdeps/unix/sysv/linux/Versions              |   1 +
 sysdeps/unix/sysv/linux/aarch64/libc.abilist  |   1 +
 sysdeps/unix/sysv/linux/alpha/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/arc/libc.abilist      |   1 +
 sysdeps/unix/sysv/linux/arm/be/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/arm/le/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/csky/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/hppa/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/i386/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/ia64/libc.abilist     |   1 +
 .../sysv/linux/loongarch/lp64/libc.abilist    |   1 +
 .../sysv/linux/m68k/coldfire/libc.abilist     |   1 +
 .../unix/sysv/linux/m68k/m680x0/libc.abilist  |   1 +
 .../sysv/linux/microblaze/be/libc.abilist     |   1 +
 .../sysv/linux/microblaze/le/libc.abilist     |   1 +
 .../sysv/linux/mips/mips32/fpu/libc.abilist   |   1 +
 .../sysv/linux/mips/mips32/nofpu/libc.abilist |   1 +
 .../sysv/linux/mips/mips64/n32/libc.abilist   |   1 +
 .../sysv/linux/mips/mips64/n64/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/nios2/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/or1k/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/pidfd_getpid.c        | 122 ++++++++++++
 .../linux/powerpc/powerpc32/fpu/libc.abilist  |   1 +
 .../powerpc/powerpc32/nofpu/libc.abilist      |   1 +
 .../linux/powerpc/powerpc64/be/libc.abilist   |   1 +
 .../linux/powerpc/powerpc64/le/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/procutils.c           | 104 ++++++++++
 sysdeps/unix/sysv/linux/procutils.h           |  35 ++++
 .../unix/sysv/linux/riscv/rv32/libc.abilist   |   1 +
 .../unix/sysv/linux/riscv/rv64/libc.abilist   |   1 +
 .../unix/sysv/linux/s390/s390-32/libc.abilist |   1 +
 .../unix/sysv/linux/s390/s390-64/libc.abilist |   1 +
 sysdeps/unix/sysv/linux/sh/be/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/sh/le/libc.abilist    |   1 +
 .../sysv/linux/sparc/sparc32/libc.abilist     |   1 +
 .../sysv/linux/sparc/sparc64/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/sys/pidfd.h           |   4 +
 sysdeps/unix/sysv/linux/tst-pidfd.c           |  45 +++++
 sysdeps/unix/sysv/linux/tst-pidfd_getpid.c    | 181 ++++++++++++++++++
 .../unix/sysv/linux/x86_64/64/libc.abilist    |   1 +
 .../unix/sysv/linux/x86_64/x32/libc.abilist   |   1 +
 44 files changed, 566 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/pidfd_getpid.c
 create mode 100644 sysdeps/unix/sysv/linux/procutils.c
 create mode 100644 sysdeps/unix/sysv/linux/procutils.h
 create mode 100644 sysdeps/unix/sysv/linux/tst-pidfd_getpid.c

diff --git a/NEWS b/NEWS
index af647c7c46..fe57e187f7 100644
--- a/NEWS
+++ b/NEWS
@@ -47,6 +47,10 @@ Major new features:
   return a process ID, it returns a file descriptor that can be used along
   other pidfd functions.
 
+* On Linux, the pidfd_getpid fcuntsion has been added.  It allows to retrieve
+  the process ID associated with process file descriptor created with
+  pid_spawn, pidfd_fork, or pidfd_open.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * In the Linux kernel for the hppa/parisc architecture some of the
diff --git a/manual/process.texi b/manual/process.texi
index 93e0ab5fb7..486855203e 100644
--- a/manual/process.texi
+++ b/manual/process.texi
@@ -33,6 +33,7 @@ primitive functions to do each step individually instead.
 * Process Creation Concepts::   An overview of the hard way to do it.
 * Process Identification::      How to get the process ID of a process.
 * Creating a Process::          How to fork a child process.
+* Querying a Process::          How to query a child process.
 * Executing a File::            How to make a process execute another program.
 * Process Completion::          How to tell when a child process has completed.
 * Process Completion Status::   How to interpret the status value
@@ -389,6 +390,38 @@ Acts as @code{_Fork}, where it does not invoke any callbacks registered with
 
 This function is specific to Linux.
 
+@node Querying a Process
+@section Querying a Process
+
+The file descriptor returned by the @code{pidfd_fork} function can be used to
+query process extra information.
+
+@deftypefun pid_t pidfd_getpid (int @var{fd})
+@standards{GNU, sys/pidfd.h}
+@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
+
+The @code{pidfd_getpid} function retrieves the process ID associated with process
+file descriptor created with @code{pid_spawn}, @code{pidfd_fork}, or
+@code{pidfd_open}.
+
+If the operation fails, @code{pidfd_getpid} return @code{-1} and the following
+@code{errno} error conditionas are defined:
+
+@table @code
+@item EINVAL
+The input file descriptor is negative.
+@item EBADF
+The input file descriptor does not have a pidfd associated or an error has occurred
+parsing the kernel data.
+@item EREMOTE
+There is no process ID to denote the process in the current namespace.
+@item ESRCH
+The process for which the file descriptor refers to is terminated.
+@end table
+
+This function is specific to Linux.
+@end deftypefun
+
 @node Executing a File
 @section Executing a File
 @cindex executing a file
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 675c226a99..680bb52e64 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -210,6 +210,7 @@ tests += \
   tst-ofdlocks \
   tst-personality \
   tst-pidfd \
+  tst-pidfd_getpid \
   tst-pkey \
   tst-ppoll \
   tst-prctl \
@@ -490,8 +491,10 @@ sysdep_routines += \
   getcpu \
   oldglob \
   pidfd_fork \
+  pidfd_getpid \
   pidfd_spawn \
   pidfd_spawnp \
+  procutils \
   sched_getcpu \
   sched_getcpu \
   # sysdep_routines
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 7e4109e9c5..047bc0c92a 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -323,6 +323,7 @@ libc {
   }
   GLIBC_2.38 {
     pidfd_fork;
+    pidfd_getpid;
     pidfd_spawn;
     pidfd_spawnp;
   }
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index dbf7c44319..febfc78f29 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2666,5 +2666,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index a9d6ffce14..87f93beeb8 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2775,6 +2775,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/arc/libc.abilist b/sysdeps/unix/sysv/linux/arc/libc.abilist
index c08d548556..dd33567a75 100644
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@@ -2427,5 +2427,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
index f348336ee7..2344b8ae48 100644
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -547,6 +547,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index 5aed593521..b34ec3e9cc 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -544,6 +544,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index 8a7022aaa8..f59d84fdb0 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2703,5 +2703,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index e2ac6949df..f6527bb9db 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2652,6 +2652,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 5e8d49fc1f..28ccb54206 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2836,6 +2836,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index 3cd3c80334..aabf217819 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -2601,6 +2601,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
index 0965db2ff0..8b53d82e8c 100644
--- a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
@@ -2187,5 +2187,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 1ec24886a3..66bf4532ab 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -548,6 +548,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _Exit F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 239b1d70be..0ee9fef825 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2779,6 +2779,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index dd41d63394..8861ebb4ca 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2752,5 +2752,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
index 55c3dcd471..008dda3746 100644
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2749,5 +2749,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 295e4d8608..2d0af493ed 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2744,6 +2744,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 19fb1aebe7..ae82d18edb 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -2742,6 +2742,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index 2dd6ef5416..87aee7f86d 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2750,6 +2750,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index 6445d27220..c0d1fd370a 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2652,6 +2652,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index c1cc5134c9..06092621b9 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2791,5 +2791,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/or1k/libc.abilist b/sysdeps/unix/sysv/linux/or1k/libc.abilist
index 293643346a..88dcdd8b98 100644
--- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
+++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
@@ -2173,5 +2173,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/pidfd_getpid.c b/sysdeps/unix/sysv/linux/pidfd_getpid.c
new file mode 100644
index 0000000000..ae5fa100eb
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/pidfd_getpid.c
@@ -0,0 +1,122 @@
+/* pidfd_getpid - Get the associated pid from the pid file descriptor.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <_itoa.h>
+#include <errno.h>
+#include <intprops.h>
+#include <procutils.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysdep.h>
+#include <unistd.h>
+
+#define FDINFO_TO_FILENAME_PREFIX "/proc/self/fdinfo/"
+
+#define FDINFO_FILENAME_LEN \
+  (sizeof (FDINFO_TO_FILENAME_PREFIX) + INT_STRLEN_BOUND (int))
+
+struct parse_fdinfo_t
+{
+  bool found;
+  pid_t pid;
+};
+
+/* Parse the PID field in the fdinfo entry, if existent.  Avoid strtol or
+   similar to not be locale dependent.  */
+static int
+parse_fdinfo (const char *l, void *arg)
+{
+  enum { fieldlen = sizeof ("Pid:") - 1 };
+  if (strncmp (l, "Pid:", fieldlen) != 0)
+    return 0;
+
+  l += fieldlen;
+
+  /* Skip leading spaces.  */
+  while (*l == ' ' || (unsigned int)(*l) -'\t' < 5)
+    l++;
+
+  bool neg = false;
+  switch (*l)
+    {
+    case '-': neg = true;
+    case '+': l++;
+    }
+
+  if (*l == '\0')
+    return 0;
+
+  int n = 0;
+  while (*l != '\0')
+    {
+      /* Check if '*l' is a digit.  */
+      if ((unsigned int)(*l) - '0' >= 10)
+        return 0;
+
+      /* Ignore invalid large values.  */
+      if (INT_MULTIPLY_WRAPV (10, n, &n)
+          || INT_ADD_WRAPV (n, *l++ - '0', &n))
+        return 0;
+    }
+
+  /* -1 indicates that the process is terminated.  */
+  if (neg && n != 1)
+    return 0;
+
+  struct parse_fdinfo_t *fdinfo = arg;
+  fdinfo->pid = neg ? -n : n;
+  fdinfo->found = true;
+
+  return 1;
+}
+
+pid_t
+pidfd_getpid (int fd)
+{
+  if (__glibc_unlikely (fd < 0))
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  char fdinfoname[FDINFO_FILENAME_LEN];
+
+  char *p = mempcpy (fdinfoname, FDINFO_TO_FILENAME_PREFIX,
+		     strlen (FDINFO_TO_FILENAME_PREFIX));
+  *_fitoa_word (fd, p, 10, 0) = '\0';
+
+  struct parse_fdinfo_t fdinfo = { .found = false, .pid = -1 };
+  if (procutils_read_file (fdinfoname, parse_fdinfo, &fdinfo) == -1)
+    /* The fdinfo contains an invalid 'Pid:' value.  */
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
+
+  /* The FD does not have a 'Pid:' entry associated.  */
+  if (!fdinfo.found)
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
+
+  /* The pidfd cannot be resolved because it is in a separate pid
+     namespace.  */
+  if (fdinfo.pid == 0)
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EREMOTE);
+
+  /* A negative value means the process is terminated.  */
+  if (fdinfo.pid < 0)
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (ESRCH);
+
+  return fdinfo.pid;
+}
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 03a35e860d..ce885f9136 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -2818,6 +2818,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index a91af4245b..8063a0606e 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -2851,6 +2851,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index c15137b9ad..21fb95a352 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2572,6 +2572,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index 12c0f4cfba..14bda5b5b8 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2886,5 +2886,6 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/procutils.c b/sysdeps/unix/sysv/linux/procutils.c
new file mode 100644
index 0000000000..83b327cb9a
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/procutils.c
@@ -0,0 +1,104 @@
+/* Utilities functions to read/parse Linux procfs and sysfs.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <assert.h>
+#include <not-cancel.h>
+#include <procutils.h>
+#include <string.h>
+
+static int
+next_line (char **r, int fd, char *const buffer, char **cp, char **re,
+           char *const buffer_end)
+{
+  char *res = *cp;
+  char *nl = memchr (*cp, '\n', *re - *cp);
+  if (nl == NULL)
+    {
+      if (*cp != buffer)
+        {
+          if (*re == buffer_end)
+            {
+              memmove (buffer, *cp, *re - *cp);
+              *re = buffer + (*re - *cp);
+              *cp = buffer;
+
+              ssize_t n = __read_nocancel (fd, *re, buffer_end - *re);
+              if (n < 0)
+                return -1;
+
+              *re += n;
+
+              nl = memchr (*cp, '\n', *re - *cp);
+              while (nl == NULL && *re == buffer_end)
+                {
+                  /* Truncate too long lines.  */
+                  *re = buffer + 3 * (buffer_end - buffer) / 4;
+                  n = __read_nocancel (fd, *re, buffer_end - *re);
+                  if (n < 0)
+                    return -1;
+
+                  nl = memchr (*re, '\n', n);
+                  **re = '\0';
+                  *re += n;
+                }
+            }
+          else
+            nl = memchr (*cp, '\n', *re - *cp);
+
+          res = *cp;
+        }
+
+      if (nl == NULL)
+        nl = *re - 1;
+    }
+
+  *nl = '\0';
+  *cp = nl + 1;
+  assert (*cp <= *re);
+
+  if (res == *re)
+    return 0;
+
+  *r = res;
+  return 1;
+}
+
+int
+procutils_read_file (const char *filename, procutils_closure_t closure,
+		     void *arg)
+{
+  enum { buffer_size = 1024 };
+  char buffer[buffer_size];
+  char *buffer_end = buffer + buffer_size;
+  char *cp = buffer_end;
+  char *re = buffer_end;
+
+  int fd = __open64_nocancel (filename, O_RDONLY | O_CLOEXEC);
+  if (fd == -1)
+    return -1;
+
+  char *l;
+  int r;
+  while ((r = next_line (&l, fd, buffer, &cp, &re, buffer_end)) > 0)
+    if (closure (l, arg) != 0)
+      break;
+
+  __close_nocancel_nostatus (fd);
+
+  return r;
+}
diff --git a/sysdeps/unix/sysv/linux/procutils.h b/sysdeps/unix/sysv/linux/procutils.h
new file mode 100644
index 0000000000..64e1080920
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/procutils.h
@@ -0,0 +1,35 @@
+/* Utilities functions to read/parse Linux procfs and sysfs.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _PROCUTILS_H
+#define _PROCUTILS_H
+
+typedef int (*procutils_closure_t)(const char *line, void *arg);
+
+/* Open and read the path FILENAME, line per line, and call CLOSURE with
+   argument ARG on each line.  The read is done with a static buffer,
+   with non-cancellable calls, and the line is null terminated.
+
+   The CLOSURE should return true if the read should continue, or false
+   if the function should stop.
+
+   It returns 0 in case of success, or -1 otherwise.  */
+int procutils_read_file (const char *filename, procutils_closure_t closure,
+			 void *arg) attribute_hidden;
+
+#endif
diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
index 9537dac42d..b294ec1021 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@@ -2429,5 +2429,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index ea72e6b648..61921a02d4 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2629,5 +2629,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index d6c895b487..fbc2d5826f 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -2816,6 +2816,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index b375f5a7ab..45ab26d7a7 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2609,6 +2609,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
index 7b2266ecb3..8de69e0057 100644
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2659,6 +2659,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index 2f9f732044..3821ce3676 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2656,6 +2656,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index 144d54ebf2..7be5b0c125 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -2811,6 +2811,7 @@ GLIBC_2.38 __nldbl___isoc23_vswscanf F
 GLIBC_2.38 __nldbl___isoc23_vwscanf F
 GLIBC_2.38 __nldbl___isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 _IO_fprintf F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index bc8bd8ff54..a09b2efc90 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2624,6 +2624,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/sys/pidfd.h b/sysdeps/unix/sysv/linux/sys/pidfd.h
index 1942773957..5be3eb1167 100644
--- a/sysdeps/unix/sysv/linux/sys/pidfd.h
+++ b/sysdeps/unix/sysv/linux/sys/pidfd.h
@@ -59,4 +59,8 @@ extern int pidfd_send_signal (int __pidfd, int __sig, siginfo_t *__info,
    of the new process to the parent process.  */
 extern int pidfd_fork (unsigned int __flags) __THROW;
 
+/* Query the process ID (PID) from process descriptor __FD.  Return the PID
+   or -1 in case of an error.  */
+extern pid_t pidfd_getpid (int __fd) __THROW;
+
 #endif /* _PIDFD_H  */
diff --git a/sysdeps/unix/sysv/linux/tst-pidfd.c b/sysdeps/unix/sysv/linux/tst-pidfd.c
index 64d8a2ef40..a03de4b290 100644
--- a/sysdeps/unix/sysv/linux/tst-pidfd.c
+++ b/sysdeps/unix/sysv/linux/tst-pidfd.c
@@ -18,6 +18,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <limits.h>
 #include <support/capture_subprocess.h>
 #include <support/check.h>
 #include <support/process_state.h>
@@ -27,6 +28,9 @@
 #include <support/xsocket.h>
 #include <sys/pidfd.h>
 #include <sys/wait.h>
+#include <stdlib.h>
+
+#include <string.h>
 
 #define REMOTE_PATH "/dev/null"
 
@@ -102,6 +106,41 @@ do_test (void)
   ppid = getpid ();
   puid = getuid ();
 
+  /* Sanity check for invalid inputs.  */
+  TEST_COMPARE (pidfd_getpid (-1), -1);
+  TEST_COMPARE (errno, EINVAL);
+
+  {
+    pid_t pid = pidfd_getpid (STDOUT_FILENO);
+    TEST_COMPARE (pid, -1);
+    TEST_COMPARE (errno, EBADF);
+  }
+
+  /* Check if pidfd_getpid returns ESRCH for exited subprocess.  */
+  {
+    int pidfd = pidfd_fork (0);
+    if (pidfd == 0)
+      exit (EXIT_SUCCESS);
+
+    /* The process might be still running or already in zombie state, in any
+       case the PID is still allocated to the process.  */
+    pid_t pid = pidfd_getpid (pidfd);
+    if (pid > 0)
+      support_process_state_wait (pid, support_process_state_zombie);
+
+    siginfo_t info;
+    TEST_COMPARE (waitid (P_PIDFD, pidfd, &info, WEXITED), 0);
+    TEST_COMPARE (info.si_status, 0);
+    TEST_COMPARE (info.si_code, CLD_EXITED);
+
+    /* Once the process is reaped the associated PID is not available.  */
+    pid = pidfd_getpid (pidfd);
+    TEST_COMPARE (pid, -1);
+    TEST_COMPARE (errno, ESRCH);
+
+    xclose (pidfd);
+  }
+
   TEST_COMPARE (socketpair (AF_UNIX, SOCK_STREAM, 0, sockets), 0);
 
   pid_t pid = xfork ();
@@ -118,6 +157,12 @@ do_test (void)
   int pidfd = pidfd_open (pid, 0);
   TEST_VERIFY (pidfd != -1);
 
+  TEST_COMPARE (pidfd_getpid (INT_MAX), -1);
+  {
+    pid_t querypid = pidfd_getpid (pidfd);
+    TEST_COMPARE (querypid, pid);
+  }
+
   /* Wait for first sigtimedwait.  */
   support_process_state_wait (pid, support_process_state_sleeping);
   TEST_COMPARE (pidfd_send_signal (pidfd, SIGUSR1, NULL, 0), 0);
diff --git a/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c b/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c
new file mode 100644
index 0000000000..b50dd0e8d4
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c
@@ -0,0 +1,181 @@
+/* Specific tests for Linux pidfd_getpid.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <sched.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xsocket.h>
+#include <support/xunistd.h>
+#include <support/test-driver.h>
+#include <sys/pidfd.h>
+#include <sys/wait.h>
+#include <sys/mount.h>
+#include <string.h>
+
+#include <stdio.h>
+
+static int sockfd[2];
+
+static void
+send_fd (const int sock, const int fd)
+{
+  union
+    {
+      struct cmsghdr hdr;
+      char buf[CMSG_SPACE (sizeof (int))];
+    } cmsgbuf = {0};
+  struct cmsghdr *cmsg;
+  char ch = 'A';
+  struct iovec vec =
+    {
+      .iov_base = &ch,
+      .iov_len = sizeof ch
+    };
+  struct msghdr msg =
+    {
+      .msg_control = &cmsgbuf.buf,
+      .msg_controllen = sizeof (cmsgbuf.buf),
+      .msg_iov = &vec,
+      .msg_iovlen = 1,
+    };
+
+  cmsg = CMSG_FIRSTHDR (&msg);
+  cmsg->cmsg_len = CMSG_LEN (sizeof (int));
+  cmsg->cmsg_level = SOL_SOCKET;
+  cmsg->cmsg_type = SCM_RIGHTS;
+  memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
+
+  ssize_t n;
+  while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+
+  TEST_VERIFY_EXIT (n == 1);
+}
+
+static int
+recv_fd (const int sock)
+{
+  union
+    {
+      struct cmsghdr hdr;
+      char buf[CMSG_SPACE(sizeof(int))];
+    } cmsgbuf = {0};
+  struct cmsghdr *cmsg;
+  char ch = '\0';
+  struct iovec vec =
+    {
+      .iov_base = &ch,
+      .iov_len = sizeof ch
+    };
+  struct msghdr msg =
+    {
+      .msg_control = &cmsgbuf.buf,
+      .msg_controllen = sizeof (cmsgbuf.buf),
+      .msg_iov = &vec,
+      .msg_iovlen = 1,
+    };
+
+  ssize_t n;
+  while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+  if (n != 1 || ch != 'A')
+    return -1;
+
+  cmsg = CMSG_FIRSTHDR (&msg);
+  if (cmsg == NULL)
+    return -1;
+  if (cmsg->cmsg_type != SCM_RIGHTS)
+    return -1;
+
+  int fd = -1;
+  memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
+  if (fd < 0)
+    return -1;
+  return fd;
+}
+
+static int
+do_test (void)
+{
+  {
+    /* The pidfd_getfd syscall was the last in the set of pidfd related
+       syscalls added to the kernel.  Use pidfd_getfd to decide if this
+       kernel has pidfd support that we can test.  */
+    int r = pidfd_getfd (0, 0, 1);
+    TEST_VERIFY_EXIT (r == -1);
+    if (errno == ENOSYS)
+      FAIL_UNSUPPORTED ("kernel does not support pidfd_getfd, skipping test");
+  }
+
+  TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
+
+  /* Check if pidfd_getpid returns EREMOTE for process not in current
+     namespace.  */
+  {
+    int pidfd = pidfd_fork (0);
+    TEST_VERIFY (pidfd >= 0);
+    if (pidfd == 0)
+      {
+        if (unshare (CLONE_NEWNS | CLONE_NEWUSER | CLONE_NEWPID) < 0)
+	  {
+	    /* Older kernels may not support all the options, or security
+	       policy may block this call.  */
+	    if (errno == EINVAL || errno == EPERM || errno == ENOSPC)
+	      exit (EXIT_UNSUPPORTED);
+	    FAIL_EXIT1 ("unshare user/fs/pid failed: %m");
+	  }
+
+	TEST_VERIFY_EXIT (mount (NULL, "/", NULL, MS_REC | MS_PRIVATE, 0)
+			  == 0);
+
+	pid_t child = xfork ();
+	if (child > 0)
+	  {
+	    int status;
+	    xwaitpid (child, &status, 0);
+	    TEST_VERIFY (WIFEXITED (status));
+	    exit (WEXITSTATUS (status));
+	  }
+
+	/* Now that we're pid 1 (effectively "root") we can mount /proc  */
+	if (mount ("proc", "/proc", "proc", 0, NULL) != 0)
+	  /* This happens if we're trying to create a nested container,
+	     like if the build is running under podman, and we lack
+	     priviledges.  */
+	  exit (EXIT_UNSUPPORTED);
+
+	int ppidfd = recv_fd (sockfd[0]);
+	TEST_COMPARE (pidfd_getpid (ppidfd), -1);
+	TEST_COMPARE (errno, EREMOTE);
+
+	exit (EXIT_SUCCESS);
+      }
+
+    send_fd (sockfd[1], pidfd);
+
+    siginfo_t info;
+    TEST_COMPARE (waitid (P_PIDFD, pidfd, &info, WEXITED), 0);
+    if (info.si_status == EXIT_UNSUPPORTED)
+      FAIL_UNSUPPORTED ("unable to unshare user/fs/pid");
+    TEST_COMPARE (info.si_status, 0);
+    TEST_COMPARE (info.si_code, CLD_EXITED);
+  }
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 045205de0c..0726b6e8d0 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2575,6 +2575,7 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 5a67604948..9c1f6830ba 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2681,5 +2681,6 @@ GLIBC_2.38 __isoc23_wcstoull_l F
 GLIBC_2.38 __isoc23_wcstoumax F
 GLIBC_2.38 __isoc23_wscanf F
 GLIBC_2.38 pidfd_fork F
+GLIBC_2.38 pidfd_getpid F
 GLIBC_2.38 pidfd_spawn F
 GLIBC_2.38 pidfd_spawnp F
-- 
2.34.1


^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 2/3] posix: Add pidfd_fork
  2023-05-17 17:35 ` [PATCH v4 2/3] posix: Add pidfd_fork Adhemerval Zanella
@ 2023-05-22 10:12   ` Florian Weimer
  2023-05-22 12:44     ` Christian Brauner
  2023-05-22 14:48     ` Adhemerval Zanella Netto
  0 siblings, 2 replies; 13+ messages in thread
From: Florian Weimer @ 2023-05-22 10:12 UTC (permalink / raw)
  To: Adhemerval Zanella; +Cc: libc-alpha, Luca Boccassi, Philip Withnall

* Adhemerval Zanella:

> +@deftypefun int pidfd_fork (unsigned int @var{flags})
> +@standards{GNU, sys/pidfd.h}
> +@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
> +The @code{fork} function is similar to @code{fork} but return a file
> +descriptor instead of process ID.
> +
> +If the operation is sucessful, there are both parent and child processes
> +and both see @code{pidfd_fork} return, but with different values: it return
> +a value of @code{0} in the child process and returns a file descriptor to
> +child's process int the parent process.  Although the value of @code{0} clashes
> +with @code{STDIN_FILENO}, it also assumed that stardand input is always
> +available so a conformant application will never see a the @code{0} stream
> +being returned to parent as a valid file descriptor.

I think this is a bit ugly.  Maybe pidfd_fork should return the PID/zero
as fork, and store the FD through an int * argument?

The documentaiton should discuss if SIGCHLD is sent for such processes,
and if the PID can be used in waitpid etc.  Ideally we'd have test cases
for this behavior, too. 8-)

I think it would be valuable to support creating subprocesses without
ever sending SIGCHLD on their termination.  Not sure if this should be
the default behavior, or something enabled with a flag.

> diff --git a/posix/fork-internal.c b/posix/fork-internal.c
> new file mode 100644
> index 0000000000..be0d3219af
> --- /dev/null
> +++ b/posix/fork-internal.c

> +void
> +__fork_pos (int state, uint64_t lastrun, bool multiple_threads,
> +	    struct nss_database_data *nss_database_data)

Maybe __fork_post, with a t?

> diff --git a/posix/fork-internal.h b/posix/fork-internal.h
> new file mode 100644
> index 0000000000..3814d851c4
> --- /dev/null
> +++ b/posix/fork-internal.h

> +uint64_t __fork_pre (bool, struct nss_database_data *) attribute_hidden;
> +void __fork_pos (int, uint64_t, bool, struct nss_database_data *)
> +  attribute_hidden;

I suggest to put the arguments into a struct, with struct
nss_database_data as a non-pointer member.  It makes it easier to
document the meaning of the arguments.  And we may have to add more
things in the future.

> diff --git a/sysdeps/unix/sysv/linux/pidfd_fork.c b/sysdeps/unix/sysv/linux/pidfd_fork.c
> new file mode 100644
> index 0000000000..a3ef48ce77
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/pidfd_fork.c

> +static int
> +forkfd (void)
> +{
> +  /* The kernel should not change the pidfd for the child, and the returning
> +     value on the parent is always larger than 0 (since a new file descriptor
> +     is always opened with CLONE_PIDFD is the kernel supports it.  */

Missing ).

Thanks,
Florian


^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349)
  2023-05-17 17:35 ` [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349) Adhemerval Zanella
@ 2023-05-22 10:41   ` Florian Weimer
  2023-05-22 10:46     ` Andreas Schwab
  2023-05-22 14:18     ` Adhemerval Zanella Netto
  0 siblings, 2 replies; 13+ messages in thread
From: Florian Weimer @ 2023-05-22 10:41 UTC (permalink / raw)
  To: Adhemerval Zanella; +Cc: libc-alpha, Luca Boccassi, Philip Withnall

* Adhemerval Zanella:

> Returning a pidfd allows a process to keep a race-free handle to a child
> process, otherwise the caller will need to either use pidfd_open (which
> still might be subject to TOCTOU) or keep using the old racy interface.
>
> The implementation makes sure that kernel must support the complete
> pidfd interface, meaning that waitid (P_PIDFD) should be supported
> (added on Linux 5.4).  It ensure that non racy workaround is required
> (such as reading procfs fdinfo pid to use along with old wait interfaces).
>  If kernel does not have the required support the interface returns ENOSYS.

“It avoids workarounds with race conditions”?

> These interfaces are similar to the posix_spawn and posix_spawnp, with
> the only different diferent being it returns a process file descriptor
> (int) instead of process ID (pid_t).  Their prototypes are:
>
>   int pidfd_spawn (int *restrict pidfd,
>  		   const char *restrict file,
>   		   const posix_spawn_file_actions_t *restrict facts,
>   		   const posix_spawnattr_t *restrict attrp,
>   		   char *const argv[restrict],
>   		   char *const envp[restrict])
>
>   int pidfd_spawnp (int *restrict pidfd,
>  		    const char *restrict path,
>   		    const posix_spawn_file_actions_t *restrict facts,
>   		    const posix_spawnattr_t *restrict attrp,
>   		    char *const argv[restrict_arr],
>   		    char *const envp[restrict_arr]);

Should we return the pid_t value as we..

> A new symbol is used instead of a posix_spawn extension to avoid possible
> issue with language bindings that might track the return argument
> lifetime.  Although, on Linux pid_t and int are interchangeable, POSIX
> only state that pid_t should be a signed interger.
>
> Both symbols reuse the posix_spawn posix_spawn_file_actions_t and
> posix_spawnattr_t, to void rehash posix_spawn API or add a new one.
>  It also mean that both interfaces support the same attribute and
> file actions, and a new flag or file actions on posix_spawn is also
> added automatically for pidfd_spawn.

Same question as with pidfd_fork: how does this interact with SIGCHLD,
and can the PID be used with waitpid?

> diff --git a/posix/spawn.h b/posix/spawn.h
> index 0a6a070523..2e20991627 100644
> --- a/posix/spawn.h
> +++ b/posix/spawn.h
> @@ -229,6 +229,8 @@ posix_spawn_file_actions_addtcsetpgrp_np (posix_spawn_file_actions_t *,
>  
>  #endif /* __USE_MISC */
>  
> +#include <bits/spawn_ext.h>
> +
>  __END_DECLS

Nested __BEGIN_DECLS.  You should probably move the #include after
__END_DECLS.

> diff --git a/sysdeps/unix/sysv/linux/clone-pidfd-support.c b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
> new file mode 100644
> index 0000000000..4bf2317c17
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/clone-pidfd-support.c

> +         Also tThe waitid is a cancellation entrypoint, so issue the syscall
> +	 directly.  */

Typo: “tThe”

Thanks,
Florian


^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349)
  2023-05-22 10:41   ` Florian Weimer
@ 2023-05-22 10:46     ` Andreas Schwab
  2023-05-22 14:18     ` Adhemerval Zanella Netto
  1 sibling, 0 replies; 13+ messages in thread
From: Andreas Schwab @ 2023-05-22 10:46 UTC (permalink / raw)
  To: Florian Weimer via Libc-alpha
  Cc: Adhemerval Zanella, Florian Weimer, Luca Boccassi, Philip Withnall

On Mai 22 2023, Florian Weimer via Libc-alpha wrote:

>> diff --git a/sysdeps/unix/sysv/linux/clone-pidfd-support.c b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
>> new file mode 100644
>> index 0000000000..4bf2317c17
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
>
>> +         Also tThe waitid is a cancellation entrypoint, so issue the syscall
>> +	 directly.  */
>
> Typo: “tThe”

It should be removed altogether, since waitid is a proper name.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 2/3] posix: Add pidfd_fork
  2023-05-22 10:12   ` Florian Weimer
@ 2023-05-22 12:44     ` Christian Brauner
  2023-05-22 14:48     ` Adhemerval Zanella Netto
  1 sibling, 0 replies; 13+ messages in thread
From: Christian Brauner @ 2023-05-22 12:44 UTC (permalink / raw)
  To: Florian Weimer
  Cc: Adhemerval Zanella, libc-alpha, Luca Boccassi, Philip Withnall

On Mon, May 22, 2023 at 12:12:16PM +0200, Florian Weimer via Libc-alpha wrote:
> * Adhemerval Zanella:
> 
> > +@deftypefun int pidfd_fork (unsigned int @var{flags})
> > +@standards{GNU, sys/pidfd.h}
> > +@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
> > +The @code{fork} function is similar to @code{fork} but return a file
> > +descriptor instead of process ID.
> > +
> > +If the operation is sucessful, there are both parent and child processes
> > +and both see @code{pidfd_fork} return, but with different values: it return
> > +a value of @code{0} in the child process and returns a file descriptor to
> > +child's process int the parent process.  Although the value of @code{0} clashes
> > +with @code{STDIN_FILENO}, it also assumed that stardand input is always
> > +available so a conformant application will never see a the @code{0} stream
> > +being returned to parent as a valid file descriptor.
> 
> I think this is a bit ugly.  Maybe pidfd_fork should return the PID/zero

I agree. We went through some pain to ensure that 0 can be used as a
valid fd value. Imho, it'd be better to use a return argument. It would
also align with how CLONE_PIDFD with legacy clone() works.

> as fork, and store the FD through an int * argument?
> 
> The documentaiton should discuss if SIGCHLD is sent for such processes,

Depends on whether you set exit_signal. I would expect pidfd_fork() to
very closely mirror the semantics of fork(). So I would expect SIGCHLD
to be delivered. But that's not how I understand this patchset just from
glancing at it.

> and if the PID can be used in waitpid etc.  Ideally we'd have test cases

The pid can be used with waitpid(). I don't understand why it wouldn't.

> for this behavior, too. 8-)

> 
> I think it would be valuable to support creating subprocesses without
> ever sending SIGCHLD on their termination.  Not sure if this should be
> the default behavior, or something enabled with a flag.

Best behind a flag. If you name it pidfd_fork() then it might be best if
you default to delivering SIGCHLD and provide an opt-out through a
flag.

^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 3/3] linux: Add pidfd_getpid
  2023-05-17 17:35 ` [PATCH v4 3/3] linux: Add pidfd_getpid Adhemerval Zanella
@ 2023-05-22 13:00   ` Florian Weimer
  2023-05-22 17:13     ` Adhemerval Zanella Netto
  2023-05-22 13:53   ` Joe Simmons-Talbott
  1 sibling, 1 reply; 13+ messages in thread
From: Florian Weimer @ 2023-05-22 13:00 UTC (permalink / raw)
  To: Adhemerval Zanella; +Cc: libc-alpha, Luca Boccassi, Philip Withnall

* Adhemerval Zanella:

> This interface allows to obtain the associated pid ID from the

“process ID”

> process file descriptor.  It is done by parsing the procps fdinfo
> information.  Its prototype is:
>
>    pid_t pidfd_getpid (int fd)
>
> It returns the associated pid or -1 in case of an error and set the
> errno accordingly.  The possible errno values are the smae from

Typos: “and set[s] [] errno accordingly.”

“are [those] from”

> open, read, and close (used on procps parsing), along with:
>
>    - EINVAL if the FP is negative (similar to fexecve).
>
>    - EBADF if the FD does not have a PID associated of if the fdinfo

“associated o[r] if”

>      fields contains a value larger than pid_t.
>
>    - EREMOTE if the PID is in a separate namespace.
>
>    - ESRCH if the process is already terminated.

> diff --git a/sysdeps/unix/sysv/linux/pidfd_getpid.c b/sysdeps/unix/sysv/linux/pidfd_getpid.c
> new file mode 100644
> index 0000000000..ae5fa100eb
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/pidfd_getpid.c
> @@ -0,0 +1,122 @@

> +pid_t
> +pidfd_getpid (int fd)
> +{
> +  if (__glibc_unlikely (fd < 0))
> +    {
> +      __set_errno (EINVAL);
> +      return -1;
> +    }
> +
> +  char fdinfoname[FDINFO_FILENAME_LEN];
> +
> +  char *p = mempcpy (fdinfoname, FDINFO_TO_FILENAME_PREFIX,
> +		     strlen (FDINFO_TO_FILENAME_PREFIX));
> +  *_fitoa_word (fd, p, 10, 0) = '\0';
> +
> +  struct parse_fdinfo_t fdinfo = { .found = false, .pid = -1 };
> +  if (procutils_read_file (fdinfoname, parse_fdinfo, &fdinfo) == -1)
> +    /* The fdinfo contains an invalid 'Pid:' value.  */
> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
> +
> +  /* The FD does not have a 'Pid:' entry associated.  */
> +  if (!fdinfo.found)
> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
> +
> +  /* The pidfd cannot be resolved because it is in a separate pid
> +     namespace.  */
> +  if (fdinfo.pid == 0)
> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EREMOTE);
> +
> +  /* A negative value means the process is terminated.  */
> +  if (fdinfo.pid < 0)
> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (ESRCH);
> +
> +  return fdinfo.pid;

We are making a ot of error codes here.  How likely is it that they
match what a future ioctl will do?

> diff --git a/sysdeps/unix/sysv/linux/tst-pidfd.c b/sysdeps/unix/sysv/linux/tst-pidfd.c
> index 64d8a2ef40..a03de4b290 100644
> --- a/sysdeps/unix/sysv/linux/tst-pidfd.c
> +++ b/sysdeps/unix/sysv/linux/tst-pidfd.c

> +  /* Check if pidfd_getpid returns ESRCH for exited subprocess.  */
> +  {
> +    int pidfd = pidfd_fork (0);
> +    if (pidfd == 0)
> +      exit (EXIT_SUCCESS);

Should be _exit, so that the atexit handlers do not run.

I think the main remaining question is errno alignment with a future
direct kernel interface for this.

Thanks,
Florian


^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 3/3] linux: Add pidfd_getpid
  2023-05-17 17:35 ` [PATCH v4 3/3] linux: Add pidfd_getpid Adhemerval Zanella
  2023-05-22 13:00   ` Florian Weimer
@ 2023-05-22 13:53   ` Joe Simmons-Talbott
  1 sibling, 0 replies; 13+ messages in thread
From: Joe Simmons-Talbott @ 2023-05-22 13:53 UTC (permalink / raw)
  To: Adhemerval Zanella
  Cc: libc-alpha, Luca Boccassi, Florian Weimer, Philip Withnall

On Wed, May 17, 2023 at 02:35:16PM -0300, Adhemerval Zanella via Libc-alpha wrote:
> This interface allows to obtain the associated pid ID from the
> process file descriptor.  It is done by parsing the procps fdinfo
> information.  Its prototype is:
> 
>    pid_t pidfd_getpid (int fd)
> 
> It returns the associated pid or -1 in case of an error and set the
> errno accordingly.  The possible errno values are the smae from

same

Thanks,
Joe


^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349)
  2023-05-22 10:41   ` Florian Weimer
  2023-05-22 10:46     ` Andreas Schwab
@ 2023-05-22 14:18     ` Adhemerval Zanella Netto
  1 sibling, 0 replies; 13+ messages in thread
From: Adhemerval Zanella Netto @ 2023-05-22 14:18 UTC (permalink / raw)
  To: Florian Weimer; +Cc: libc-alpha, Luca Boccassi, Philip Withnall



On 22/05/23 07:41, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> Returning a pidfd allows a process to keep a race-free handle to a child
>> process, otherwise the caller will need to either use pidfd_open (which
>> still might be subject to TOCTOU) or keep using the old racy interface.
>>
>> The implementation makes sure that kernel must support the complete
>> pidfd interface, meaning that waitid (P_PIDFD) should be supported
>> (added on Linux 5.4).  It ensure that non racy workaround is required
>> (such as reading procfs fdinfo pid to use along with old wait interfaces).
>>  If kernel does not have the required support the interface returns ENOSYS.
> 
> “It avoids workarounds with race conditions”?

Ack.

> 
>> These interfaces are similar to the posix_spawn and posix_spawnp, with
>> the only different diferent being it returns a process file descriptor
>> (int) instead of process ID (pid_t).  Their prototypes are:
>>
>>   int pidfd_spawn (int *restrict pidfd,
>>  		   const char *restrict file,
>>   		   const posix_spawn_file_actions_t *restrict facts,
>>   		   const posix_spawnattr_t *restrict attrp,
>>   		   char *const argv[restrict],
>>   		   char *const envp[restrict])
>>
>>   int pidfd_spawnp (int *restrict pidfd,
>>  		    const char *restrict path,
>>   		    const posix_spawn_file_actions_t *restrict facts,
>>   		    const posix_spawnattr_t *restrict attrp,
>>   		    char *const argv[restrict_arr],
>>   		    char *const envp[restrict_arr]);
> 
> Should we return the pid_t value as we..

That's a key point where I was not sure and ended up to omit since the
patchset also adds pidfd_getpid (so if call is successful pidfd_getpid
will get you the pid).

Returning the pid will also deviate the interface for posix_spawnp, which
means that either we will need to add the pid_t as an additional input/output
argument or change the interface to return errors through errno.

> 
>> A new symbol is used instead of a posix_spawn extension to avoid possible
>> issue with language bindings that might track the return argument
>> lifetime.  Although, on Linux pid_t and int are interchangeable, POSIX
>> only state that pid_t should be a signed interger.
>>
>> Both symbols reuse the posix_spawn posix_spawn_file_actions_t and
>> posix_spawnattr_t, to void rehash posix_spawn API or add a new one.
>>  It also mean that both interfaces support the same attribute and
>> file actions, and a new flag or file actions on posix_spawn is also
>> added automatically for pidfd_spawn.
> 
> Same question as with pidfd_fork: how does this interact with SIGCHLD,
> and can the PID be used with waitpid?

It follows posix_spawn semantic to setup SIGCHLD on lower bits of clone
flags.  I think it should be feasible to add an extra posix_spawn flag
to remove it.

> 
>> diff --git a/posix/spawn.h b/posix/spawn.h
>> index 0a6a070523..2e20991627 100644
>> --- a/posix/spawn.h
>> +++ b/posix/spawn.h
>> @@ -229,6 +229,8 @@ posix_spawn_file_actions_addtcsetpgrp_np (posix_spawn_file_actions_t *,
>>  
>>  #endif /* __USE_MISC */
>>  
>> +#include <bits/spawn_ext.h>
>> +
>>  __END_DECLS
> 
> Nested __BEGIN_DECLS.  You should probably move the #include after
> __END_DECLS.

Ack.

> 
>> diff --git a/sysdeps/unix/sysv/linux/clone-pidfd-support.c b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
>> new file mode 100644
>> index 0000000000..4bf2317c17
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/clone-pidfd-support.c
> 
>> +         Also tThe waitid is a cancellation entrypoint, so issue the syscall
>> +	 directly.  */
> 
> Typo: “tThe”
> 
> Thanks,
> Florian
> 

^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 2/3] posix: Add pidfd_fork
  2023-05-22 10:12   ` Florian Weimer
  2023-05-22 12:44     ` Christian Brauner
@ 2023-05-22 14:48     ` Adhemerval Zanella Netto
  1 sibling, 0 replies; 13+ messages in thread
From: Adhemerval Zanella Netto @ 2023-05-22 14:48 UTC (permalink / raw)
  To: Florian Weimer, Christian Brauner
  Cc: libc-alpha, Luca Boccassi, Philip Withnall



On 22/05/23 07:12, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> +@deftypefun int pidfd_fork (unsigned int @var{flags})
>> +@standards{GNU, sys/pidfd.h}
>> +@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}}
>> +The @code{fork} function is similar to @code{fork} but return a file
>> +descriptor instead of process ID.
>> +
>> +If the operation is sucessful, there are both parent and child processes
>> +and both see @code{pidfd_fork} return, but with different values: it return
>> +a value of @code{0} in the child process and returns a file descriptor to
>> +child's process int the parent process.  Although the value of @code{0} clashes
>> +with @code{STDIN_FILENO}, it also assumed that stardand input is always
>> +available so a conformant application will never see a the @code{0} stream
>> +being returned to parent as a valid file descriptor.
> 
> I think this is a bit ugly.  Maybe pidfd_fork should return the PID/zero
> as fork, and store the FD through an int * argument?

Alright, I was not really sure about whether to expose the PID but I tend
to agree that for error code handling is not straightforward. I will change
to return the pid_t as fork and the pidfd as first argument.

> 
> The documentaiton should discuss if SIGCHLD is sent for such processes,
> and if the PID can be used in waitpid etc.  Ideally we'd have test cases
> for this behavior, too. 8-)

The default pidfd_fork should be similar semantically to fork, the first
version I make it similar to _Fork but I think this was a mistake.  This
included SIGCHLD handling as well (the flag is passed on clone syscall
as fork).  I will update the documentation and add extra tests.

> 
> I think it would be valuable to support creating subprocesses without
> ever sending SIGCHLD on their termination.  Not sure if this should be
> the default behavior, or something enabled with a flag.

I tend to agree with Christian and this should be behind a flags.  I
will add a flag for this.

> 
>> diff --git a/posix/fork-internal.c b/posix/fork-internal.c
>> new file mode 100644
>> index 0000000000..be0d3219af
>> --- /dev/null
>> +++ b/posix/fork-internal.c
> 
>> +void
>> +__fork_pos (int state, uint64_t lastrun, bool multiple_threads,
>> +	    struct nss_database_data *nss_database_data)
> 
> Maybe __fork_post, with a t?

Ack.

> 
>> diff --git a/posix/fork-internal.h b/posix/fork-internal.h
>> new file mode 100644
>> index 0000000000..3814d851c4
>> --- /dev/null
>> +++ b/posix/fork-internal.h
> 
>> +uint64_t __fork_pre (bool, struct nss_database_data *) attribute_hidden;
>> +void __fork_pos (int, uint64_t, bool, struct nss_database_data *)
>> +  attribute_hidden;
> 
> I suggest to put the arguments into a struct, with struct
> nss_database_data as a non-pointer member.  It makes it easier to
> document the meaning of the arguments.  And we may have to add more
> things in the future.

Ack.

> 
>> diff --git a/sysdeps/unix/sysv/linux/pidfd_fork.c b/sysdeps/unix/sysv/linux/pidfd_fork.c
>> new file mode 100644
>> index 0000000000..a3ef48ce77
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/pidfd_fork.c
> 
>> +static int
>> +forkfd (void)
>> +{
>> +  /* The kernel should not change the pidfd for the child, and the returning
>> +     value on the parent is always larger than 0 (since a new file descriptor
>> +     is always opened with CLONE_PIDFD is the kernel supports it.  */
> 
> Missing ).

Ack.

^ permalink raw reply	[flat|nested] 13+ messages in thread
* Re: [PATCH v4 3/3] linux: Add pidfd_getpid
  2023-05-22 13:00   ` Florian Weimer
@ 2023-05-22 17:13     ` Adhemerval Zanella Netto
  0 siblings, 0 replies; 13+ messages in thread
From: Adhemerval Zanella Netto @ 2023-05-22 17:13 UTC (permalink / raw)
  To: Florian Weimer, Christian Brauner
  Cc: libc-alpha, Luca Boccassi, Philip Withnall



On 22/05/23 10:00, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> This interface allows to obtain the associated pid ID from the
> 
> “process ID”

Ack.

> 
>> process file descriptor.  It is done by parsing the procps fdinfo
>> information.  Its prototype is:
>>
>>    pid_t pidfd_getpid (int fd)
>>
>> It returns the associated pid or -1 in case of an error and set the
>> errno accordingly.  The possible errno values are the smae from
> 
> Typos: “and set[s] [] errno accordingly.”

Ack.

> 
> “are [those] from”

Ack.

> 
>> open, read, and close (used on procps parsing), along with:
>>
>>    - EINVAL if the FP is negative (similar to fexecve).
>>
>>    - EBADF if the FD does not have a PID associated of if the fdinfo
> 
> “associated o[r] if”

Ack.

> 
>>      fields contains a value larger than pid_t.
>>
>>    - EREMOTE if the PID is in a separate namespace.
>>
>>    - ESRCH if the process is already terminated.
> 
>> diff --git a/sysdeps/unix/sysv/linux/pidfd_getpid.c b/sysdeps/unix/sysv/linux/pidfd_getpid.c
>> new file mode 100644
>> index 0000000000..ae5fa100eb
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/pidfd_getpid.c
>> @@ -0,0 +1,122 @@
> 
>> +pid_t
>> +pidfd_getpid (int fd)
>> +{
>> +  if (__glibc_unlikely (fd < 0))
>> +    {
>> +      __set_errno (EINVAL);
>> +      return -1;
>> +    }
>> +
>> +  char fdinfoname[FDINFO_FILENAME_LEN];
>> +
>> +  char *p = mempcpy (fdinfoname, FDINFO_TO_FILENAME_PREFIX,
>> +		     strlen (FDINFO_TO_FILENAME_PREFIX));
>> +  *_fitoa_word (fd, p, 10, 0) = '\0';
>> +
>> +  struct parse_fdinfo_t fdinfo = { .found = false, .pid = -1 };
>> +  if (procutils_read_file (fdinfoname, parse_fdinfo, &fdinfo) == -1)
>> +    /* The fdinfo contains an invalid 'Pid:' value.  */
>> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
>> +
>> +  /* The FD does not have a 'Pid:' entry associated.  */
>> +  if (!fdinfo.found)
>> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF);
>> +
>> +  /* The pidfd cannot be resolved because it is in a separate pid
>> +     namespace.  */
>> +  if (fdinfo.pid == 0)
>> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (EREMOTE);
>> +
>> +  /* A negative value means the process is terminated.  */
>> +  if (fdinfo.pid < 0)
>> +    return INLINE_SYSCALL_ERROR_RETURN_VALUE (ESRCH);
>> +
>> +  return fdinfo.pid;
> 
> We are making a ot of error codes here.  How likely is it that they
> match what a future ioctl will do?

I think Christian can answer this question better than me (even if a
kernel like interface will be even accepted).  In any case, I think
we need at least a distinction between an invalid pidfd (EBADF), an already
terminated process (ESRCH), and a non accessible namespace (EREMOTE). 

I think it would be better to replace EINVAL for negative file descriptors
with EBADF, to follow what other interfaces already do (like fstat).

> 
>> diff --git a/sysdeps/unix/sysv/linux/tst-pidfd.c b/sysdeps/unix/sysv/linux/tst-pidfd.c
>> index 64d8a2ef40..a03de4b290 100644
>> --- a/sysdeps/unix/sysv/linux/tst-pidfd.c
>> +++ b/sysdeps/unix/sysv/linux/tst-pidfd.c
> 
>> +  /* Check if pidfd_getpid returns ESRCH for exited subprocess.  */
>> +  {
>> +    int pidfd = pidfd_fork (0);
>> +    if (pidfd == 0)
>> +      exit (EXIT_SUCCESS);
> 
> Should be _exit, so that the atexit handlers do not run.

Ack.

> 
> I think the main remaining question is errno alignment with a future
> direct kernel interface for this.
> 
> Thanks,
> Florian
> 

^ permalink raw reply	[flat|nested] 13+ messages in thread
end of thread, other threads:[~2023-05-22 17:13 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-05-17 17:35 [PATCH v4 0/3] Add pidfd_spawn, pidfd_spawnp, pidfd_fork, and pidfd_getpid Adhemerval Zanella
2023-05-17 17:35 ` [PATCH v4 1/3] posix: Add pidfd_spawn and pidfd_spawnp (BZ# 30349) Adhemerval Zanella
2023-05-22 10:41   ` Florian Weimer
2023-05-22 10:46     ` Andreas Schwab
2023-05-22 14:18     ` Adhemerval Zanella Netto
2023-05-17 17:35 ` [PATCH v4 2/3] posix: Add pidfd_fork Adhemerval Zanella
2023-05-22 10:12   ` Florian Weimer
2023-05-22 12:44     ` Christian Brauner
2023-05-22 14:48     ` Adhemerval Zanella Netto
2023-05-17 17:35 ` [PATCH v4 3/3] linux: Add pidfd_getpid Adhemerval Zanella
2023-05-22 13:00   ` Florian Weimer
2023-05-22 17:13     ` Adhemerval Zanella Netto
2023-05-22 13:53   ` Joe Simmons-Talbott

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