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gh-149464: Support os.pidfd_getfd(pidfd, targetfd, flags=0) syscall #149465

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Merged
vstinner merged 14 commits into from
May 18, 2026
Merged

gh-149464: Support os.pidfd_getfd(pidfd, targetfd, flags=0) syscall #149465

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54f3cda
actual syscall
maurycy May 6, 2026
767fce3
regen-global-objects, clinic
maurycy May 6, 2026
4cfc95f
just docs
maurycy May 6, 2026
c89561a
5.6
maurycy May 6, 2026
ff1fb21
test
maurycy May 6, 2026
32966f6
lint
maurycy May 6, 2026
1833ff7
make it explicit why i'm doing this
maurycy May 6, 2026
a2b6f61
blurb
maurycy May 6, 2026
719567a
gqgq, typo
maurycy May 6, 2026
453e3de
Update Doc/library/os.rst
maurycy May 6, 2026
46e604d
victor comments
maurycy May 14, 2026
23ea074
dzień dobry, os_helper.make_bad_fd
maurycy May 18, 2026
cad9541
Merge branch 'main' into pidfd_getfd
maurycy May 18, 2026
8d0b72b
whats new
maurycy May 18, 2026
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12 changes: 12 additions & 0 deletions Doc/library/os.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -5062,6 +5062,18 @@ written in Python, such as a mail server's external command delivery program.
.. availability:: Linux >= 5.10
.. versionadded:: 3.12

.. function:: pidfd_getfd(pidfd, targetfd, *, flags=0)

Duplicate *targetfd* from the process referred to by the process file
descriptor *pidfd*, into the calling process. The returned file descriptor
is :ref:`non-inheritable <fd_inheritance>`.

*flags* is reserved, and currently must be ``0``.

See the :manpage:`pidfd_getfd(2)` man page for more details.

.. availability:: Linux >= 5.6, Android >= :func:`build-time <sys.getandroidapilevel>` API level 31
.. versionadded:: next

.. function:: plock(op, /)

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8 changes: 5 additions & 3 deletions Doc/whatsnew/3.16.rst
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Expand Up @@ -86,10 +86,12 @@ New modules
Improved modules
================

module_name
-----------
os
--

* TODO
* Add :func:`os.pidfd_getfd` for duplicating a file descriptor from another
process via a pidfd. Available on Linux 5.6+.
(Contributed by Maurycy Pawłowski-Wieroński in :gh:`149464`.)

.. Add improved modules above alphabetically, not here at the end.

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2 changes: 2 additions & 0 deletions Include/internal/pycore_global_objects_fini_generated.h
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2 changes: 2 additions & 0 deletions Include/internal/pycore_global_strings.h
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Expand Up @@ -713,6 +713,7 @@ struct _Py_global_strings {
STRUCT_FOR_ID(person)
STRUCT_FOR_ID(pi_factory)
STRUCT_FOR_ID(pid)
STRUCT_FOR_ID(pidfd)
STRUCT_FOR_ID(pointer_bits)
STRUCT_FOR_ID(policy)
STRUCT_FOR_ID(pos)
Expand Down Expand Up @@ -831,6 +832,7 @@ struct _Py_global_strings {
STRUCT_FOR_ID(take_bytes)
STRUCT_FOR_ID(target)
STRUCT_FOR_ID(target_is_directory)
STRUCT_FOR_ID(targetfd)
STRUCT_FOR_ID(task)
STRUCT_FOR_ID(tb_frame)
STRUCT_FOR_ID(tb_lasti)
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2 changes: 2 additions & 0 deletions Include/internal/pycore_runtime_init_generated.h
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8 changes: 8 additions & 0 deletions Include/internal/pycore_unicodeobject_generated.h
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28 changes: 28 additions & 0 deletions Lib/test/test_os/test_posix.py
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Expand Up @@ -1604,6 +1604,34 @@ def test_pidfd_open(self):
self.assertEqual(cm.exception.errno, errno.EINVAL)
os.close(os.pidfd_open(os.getpid(), 0))

@unittest.skipUnless(hasattr(os, "pidfd_getfd"), "pidfd_getfd unavailable")
def test_pidfd_getfd(self):
fd = os.open(__file__, os.O_RDONLY)
self.addCleanup(os.close, fd)
pidfd = os.pidfd_open(os.getpid(), 0)
self.addCleanup(os.close, pidfd)
try:
dupfd = os.pidfd_getfd(pidfd, fd)
except OSError as exc:
if exc.errno == errno.ENOSYS:
self.skipTest("system does not support pidfd_getfd")
if isinstance(exc, PermissionError):
self.skipTest(f"pidfd_getfd syscall blocked: {exc!r}")
raise
self.addCleanup(os.close, dupfd)

self.assertFalse(os.get_inheritable(dupfd)) # PEP 446
self.assertEqual(os.fstat(fd), os.fstat(dupfd))

with self.assertRaises(OSError) as cm:
os.pidfd_getfd(-1, 0)
self.assertEqual(cm.exception.errno, errno.EBADF)

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maurycy marked this conversation as resolved.
with self.assertRaises(OSError) as cm:
bad_fd = os_helper.make_bad_fd()
os.pidfd_getfd(pidfd, bad_fd)
self.assertEqual(cm.exception.errno, errno.EBADF)

@os_helper.skip_unless_hardlink
@os_helper.skip_unless_symlink
def test_link_follow_symlinks(self):
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-05-06-20-10-44.gh-issue-149464.3mPhcr.rst
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@@ -0,0 +1,3 @@
Add :func:`os.pidfd_getfd` for duplicating a file descriptor from another
process via a pidfd. Available on Linux 5.6+. Patch by Maurycy
Pawłowski-Wieroński.
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maurycy marked this conversation as resolved.
93 changes: 92 additions & 1 deletion Modules/clinic/posixmodule.c.h
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30 changes: 30 additions & 0 deletions Modules/posixmodule.c
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Expand Up @@ -10777,6 +10777,35 @@ os_pidfd_open_impl(PyObject *module, pid_t pid, unsigned int flags)
#endif


#if defined(__linux__) && defined(__NR_pidfd_getfd) && \
!(defined(__ANDROID__) && __ANDROID_API__ < 31)
/*[clinic input]
os.pidfd_getfd
pidfd: int
Comment thread
maurycy marked this conversation as resolved.
A process file descriptor.
targetfd: int
The file descriptor to duplicate from the target process.
*
flags: unsigned_int = 0
Reserved, must be 0.
Comment thread
picnixz marked this conversation as resolved.

Duplicate a file descriptor from the process referred to by *pidfd*.
[clinic start generated code]*/

static PyObject *
os_pidfd_getfd_impl(PyObject *module, int pidfd, int targetfd,
unsigned int flags)
/*[clinic end generated code: output=e1a1415a13c7137f input=ef6417fb10deb1cc]*/
{
int fd = syscall(__NR_pidfd_getfd, pidfd, targetfd, flags);
if (fd < 0) {
return posix_error();
}
return PyLong_FromLong(fd);
}
#endif


#ifdef HAVE_SETNS
/*[clinic input]
os.setns
Expand Down Expand Up @@ -17606,6 +17635,7 @@ static PyMethodDef posix_methods[] = {
OS_WAITID_METHODDEF
OS_WAITPID_METHODDEF
OS_PIDFD_OPEN_METHODDEF
OS_PIDFD_GETFD_METHODDEF
OS_GETSID_METHODDEF
OS_SETSID_METHODDEF
OS_SETPGID_METHODDEF
Expand Down
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