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gh-153400: Use glibc functions instead of syscall() #155518

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c99f647
gh-153400: Use glibc functions instead of syscall()
vstinner Aug 10, 2026
b6bbfd9
Use unsigned int for os.getrandom() flags
vstinner Aug 10, 2026
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2026-08-10-22-11-15.gh-issue-153400.Ds3GI3.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,4 @@
:mod:`os` and :mod:`signal`: Use glibc functions instead of ``syscall()``:
``pidfd_open()``, ``pidfd_getfd()`` and ``pidfd_send_signal()`` (glibc 2.36),
``gettid()`` and ``getdents64()`` (glibc 2.30), and ``getrandom()`` (glibc
2.25). Patch by Victor Stinner.
32 changes: 23 additions & 9 deletions Modules/_posixsubprocess.c
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Original file line number Diff line number Diff line change
Expand Up @@ -388,20 +388,26 @@ _close_range_except(int start_fd,
return 0;
}

#if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
#if defined(HAVE_GETDENTS64) \
|| (defined(__linux__) && defined(HAVE_SYS_SYSCALL_H))

#ifdef HAVE_GETDENTS64
# define py_dirent64 dirent64
#else
/* It doesn't matter if d_name has room for NAME_MAX chars; we're using this
* only to read a directory of short file descriptor number names. The kernel
* will return an error if we didn't give it enough space. Highly Unlikely.
* This structure is very old and stable: It will not change unless the kernel
* chooses to break compatibility with all existing binaries. Highly Unlikely.
*/
struct linux_dirent64 {
struct py_dirent64 {
unsigned long long d_ino;
long long d_off;
unsigned short d_reclen; /* Length of this linux_dirent */
unsigned char d_type;
char d_name[256]; /* Filename (null-terminated) */
};
#endif // !HAVE_GETDENTS64

static int
_brute_force_closer(int first, int last)
Expand Down Expand Up @@ -441,19 +447,27 @@ _close_open_fds_safe(int start_fd, int *fds_to_keep, Py_ssize_t fds_to_keep_len)
_brute_force_closer);
return;
} else {
char buffer[sizeof(struct linux_dirent64)];
int bytes;
while ((bytes = syscall(SYS_getdents64, fd_dir_fd,
(struct linux_dirent64 *)buffer,
sizeof(buffer))) > 0) {
struct linux_dirent64 *entry;
char buffer[sizeof(struct py_dirent64)];
Py_ssize_t bytes;
while (1) {
#ifdef HAVE_GETDENTS64
bytes = getdents64(fd_dir_fd, buffer, sizeof(buffer));
#else
bytes = syscall(SYS_getdents64, fd_dir_fd,
(struct py_dirent64 *)buffer, sizeof(buffer));
#endif
if (bytes <= 0) {
break;
}

struct py_dirent64 *entry;
int offset;
#ifdef _Py_MEMORY_SANITIZER
__msan_unpoison(buffer, bytes);
#endif
for (offset = 0; offset < bytes; offset += entry->d_reclen) {
int fd;
entry = (struct linux_dirent64 *)(buffer + offset);
entry = (struct py_dirent64 *)(buffer + offset);
if ((fd = _pos_int_from_ascii(entry->d_name)) < 0)
continue; /* Not a number. */
if (fd != fd_dir_fd && fd >= start_fd &&
Expand Down
36 changes: 24 additions & 12 deletions Modules/clinic/posixmodule.c.h
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28 changes: 20 additions & 8 deletions Modules/clinic/signalmodule.c.h
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36 changes: 27 additions & 9 deletions Modules/posixmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,10 @@
# include "emscripten.h" // emscripten_debugger()
#endif

#ifdef HAVE_SYS_RANDOM_H
# include <sys/random.h> // getrandom()
#endif

#ifdef HAVE_SYS_UIO_H
# include <sys/uio.h>
#endif
Expand Down Expand Up @@ -10810,8 +10814,9 @@ os_wait_impl(PyObject *module)


// This system call always crashes on older Android versions.
#if defined(__linux__) && defined(__NR_pidfd_open) && \
!(defined(__ANDROID__) && __ANDROID_API__ < 31)
#if defined(HAVE_PIDFD_OPEN) \
|| (defined(__linux__) && defined(__NR_pidfd_open) \
&& !(defined(__ANDROID__) && __ANDROID_API__ < 31))
/*[clinic input]
os.pidfd_open
pid: pid_t
Expand All @@ -10827,7 +10832,11 @@ static PyObject *
os_pidfd_open_impl(PyObject *module, pid_t pid, unsigned int flags)
/*[clinic end generated code: output=5c7252698947dc41 input=03058b32c389f874]*/
{
#ifdef HAVE_PIDFD_OPEN
int fd = pidfd_open(pid, flags);
#else
int fd = syscall(__NR_pidfd_open, pid, flags);
#endif
if (fd < 0) {
return posix_error();
}
Expand All @@ -10836,8 +10845,9 @@ 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)
#if defined(HAVE_PIDFD_GETFD) \
|| (defined(__linux__) && defined(__NR_pidfd_getfd) \
&& !(defined(__ANDROID__) && __ANDROID_API__ < 31))
/*[clinic input]
os.pidfd_getfd
pidfd: int
Expand All @@ -10856,7 +10866,11 @@ os_pidfd_getfd_impl(PyObject *module, int pidfd, int targetfd,
unsigned int flags)
/*[clinic end generated code: output=e1a1415a13c7137f input=ef6417fb10deb1cc]*/
{
#ifdef HAVE_PIDFD_GETFD
int fd = pidfd_getfd(pidfd, targetfd, flags);
#else
int fd = syscall(__NR_pidfd_getfd, pidfd, targetfd, flags);
#endif
if (fd < 0) {
return posix_error();
}
Expand Down Expand Up @@ -17369,19 +17383,19 @@ os_fspath_impl(PyObject *module, PyObject *path)
return PyOS_FSPath(path);
}

#ifdef HAVE_GETRANDOM_SYSCALL
#if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
/*[clinic input]
os.getrandom

size: Py_ssize_t
flags: int=0
flags: unsigned_int(bitwise=True) = 0

Obtain a series of random bytes.
[clinic start generated code]*/

static PyObject *
os_getrandom_impl(PyObject *module, Py_ssize_t size, int flags)
/*[clinic end generated code: output=b3a618196a61409c input=59bafac39c594947]*/
os_getrandom_impl(PyObject *module, Py_ssize_t size, unsigned int flags)
/*[clinic end generated code: output=c2163c05f0e1d0a1 input=e0174983f5703f82]*/
{
if (size < 0) {
errno = EINVAL;
Expand All @@ -17396,7 +17410,11 @@ os_getrandom_impl(PyObject *module, Py_ssize_t size, int flags)

Py_ssize_t n;
while (1) {
#ifdef HAVE_GETRANDOM
n = getrandom(data, size, flags);
#else
n = syscall(SYS_getrandom, data, size, flags);
#endif
if (n < 0 && errno == EINTR) {
if (PyErr_CheckSignals() < 0) {
goto error;
Expand Down Expand Up @@ -18504,7 +18522,7 @@ all_ins(PyObject *m)
if (PyModule_AddIntMacro(m, RTLD_MEMBER)) return -1;
#endif

#ifdef HAVE_GETRANDOM_SYSCALL
#if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
if (PyModule_AddIntMacro(m, GRND_RANDOM)) return -1;
if (PyModule_AddIntMacro(m, GRND_NONBLOCK)) return -1;
#endif
Expand Down
22 changes: 16 additions & 6 deletions Modules/signalmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,10 @@
# include <pthread.h>
#endif

#ifdef HAVE_SYS_PIDFD_H
# include <sys/pidfd.h> // pidfd_send_signal()
#endif

#ifndef SIG_ERR
# define SIG_ERR ((PyOS_sighandler_t)(-1))
#endif
Expand Down Expand Up @@ -1300,31 +1304,37 @@ signal_pthread_kill_impl(PyObject *module, unsigned long thread_id,


// This system call always crashes on older Android versions.
#if defined(__linux__) && defined(__NR_pidfd_send_signal) && \
!(defined(__ANDROID__) && __ANDROID_API__ < 31)
#if defined(HAVE_PIDFD_SEND_SIGNAL) \
|| (defined(__linux__) && defined(__NR_pidfd_send_signal) \
&& !(defined(__ANDROID__) && __ANDROID_API__ < 31))
/*[clinic input]
signal.pidfd_send_signal

pidfd: int
signalnum: int
siginfo: object = None
flags: int = 0
flags: unsigned_int(bitwise=True) = 0
/

Send a signal to a process referred to by a pid file descriptor.
[clinic start generated code]*/

static PyObject *
signal_pidfd_send_signal_impl(PyObject *module, int pidfd, int signalnum,
PyObject *siginfo, int flags)
/*[clinic end generated code: output=2d59f04a75d9cbdf input=2a6543a1f4ac2000]*/
PyObject *siginfo, unsigned int flags)
/*[clinic end generated code: output=1804b5a19d269104 input=a6e82a3c264fa19d]*/

{
if (siginfo != Py_None) {
PyErr_SetString(PyExc_TypeError, "siginfo must be None");
return NULL;
}
if (syscall(__NR_pidfd_send_signal, pidfd, signalnum, NULL, flags) < 0) {
#ifdef HAVE_PIDFD_SEND_SIGNAL
int res = pidfd_send_signal(pidfd, signalnum, NULL, flags);
#else
int res = syscall(__NR_pidfd_send_signal, pidfd, signalnum, NULL, flags);
#endif
if (res < 0) {
PyErr_SetFromErrno(PyExc_OSError);
return NULL;
}
Expand Down
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