@@ -34,6 +34,10 @@ Major new features:
posix_spawnattr_getcgroup_np), setting a different signal on process
termination, and making the function act as _Fork.
+* On Linux, the pidfd_getpid function has been added. It allows retrieving
+ the process ID associated with the process file descriptor created by
+ pid_spawn, fork_np, or pidfd_open.
+
Deprecated and removed features, and other changes affecting compatibility:
[Add deprecations, removals and changes affecting compatibility here]
@@ -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
@@ -424,6 +425,43 @@ child with @code{wait} or @code{waitid}.
This function is a GNU extension and specific to Linux.
@end deftypefun
+@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 EBADF
+The input file descriptor is invalid, 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.
+@item ENOENT
+The procfs is not mounted.
+@item ENFILE.
+Too many open files in system (@code{pidfd_open} tries to open a procfs file and
+read its contents).
+@item ENOMEM
+Insufficient kernel memory was available.
+@end table
+
+This function is specific to Linux.
+@end deftypefun
+
@node Executing a File
@section Executing a File
@cindex executing a file
@@ -213,6 +213,7 @@ tests += \
tst-ofdlocks \
tst-personality \
tst-pidfd \
+ tst-pidfd_getpid \
tst-pkey \
tst-ppoll \
tst-prctl \
@@ -494,8 +495,10 @@ sysdep_routines += \
getcpu \
oldglob \
fork_np \
+ pidfd_getpid \
pidfd_spawn \
pidfd_spawnp \
+ procutils \
sched_getcpu \
spawnattr_getcgroup_np \
spawnattr_setcgroup_np \
@@ -323,6 +323,7 @@ libc {
}
GLIBC_2.39 {
fork_np;
+ pidfd_getpid;
pidfd_spawn;
pidfd_spawnp;
posix_spawnattr_getcgroup_np;
@@ -2674,6 +2674,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2783,6 +2783,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2435,6 +2435,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -555,6 +555,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -552,6 +552,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -56,5 +56,5 @@ __clone_pidfd_supported (void)
atomic_store_relaxed (&__waitid_pidfd_supported, state);
}
- return state > 1;
+ return state > 0;
}
@@ -2711,6 +2711,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2660,6 +2660,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2844,6 +2844,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2609,6 +2609,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2195,6 +2195,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -556,6 +556,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2787,6 +2787,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2760,6 +2760,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2757,6 +2757,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2752,6 +2752,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2750,6 +2750,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2758,6 +2758,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2660,6 +2660,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2799,6 +2799,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2181,6 +2181,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
new file mode 100644
@@ -0,0 +1,126 @@
+/* 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;
+ l++;
+ break;
+ case '+':
+ return -1;
+ }
+
+ if (*l == '\0')
+ return 0;
+
+ int n = 0;
+ while (*l != '\0')
+ {
+ /* Check if '*l' is a digit. */
+ if ('0' > *l || *l > '9')
+ return -1;
+
+ /* Ignore invalid large values. */
+ if (INT_MULTIPLY_WRAPV (10, n, &n)
+ || INT_ADD_WRAPV (n, *l++ - '0', &n))
+ return -1;
+ }
+
+ /* -1 indicates that the process is terminated. */
+ if (neg && n != 1)
+ return -1;
+
+ 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 (EBADF);
+ 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))
+ /* 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;
+}
@@ -2826,6 +2826,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2859,6 +2859,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2580,6 +2580,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2894,6 +2894,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
new file mode 100644
@@ -0,0 +1,97 @@
+/* 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 = TEMP_FAILURE_RETRY (
+ __read_nocancel (fd, *re, buffer_end - *re));
+ if (n < 0)
+ return -1;
+
+ *re += n;
+
+ nl = memchr (*cp, '\n', *re - *cp);
+ if (nl == NULL)
+ /* Line too long. */
+ return 0;
+ }
+ 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;
+}
+
+bool
+procutils_read_file (const char *filename, procutils_closure_t closure,
+ void *arg)
+{
+ enum { buffer_size = PROCUTILS_MAX_LINE_LEN };
+ char buffer[buffer_size];
+ char *buffer_end = buffer + buffer_size;
+ char *cp = buffer_end;
+ char *re = buffer_end;
+
+ int fd = TEMP_FAILURE_RETRY (
+ __open64_nocancel (filename, O_RDONLY | O_CLOEXEC));
+ if (fd == -1)
+ return false;
+
+ 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 == 1;
+}
new file mode 100644
@@ -0,0 +1,43 @@
+/* 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
+
+#include <stdbool.h>
+
+typedef int (*procutils_closure_t) (const char *line, void *arg);
+
+#define PROCUTILS_MAX_LINE_LEN 256
+
+/* 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 0 if the read should continue, otherwise the
+ the function should stop and return early.
+
+ The '\n' is not included in the CLOSURE input argument and lines longer
+ than PROCUTILS_MAX_LINE_LEN characteres are ignored.
+
+ It returns true in case the file is fully read or false if CLOSURE
+ returns a value diferent than 0. */
+bool procutils_read_file (const char *filename, procutils_closure_t closure,
+ void *arg) attribute_hidden;
+
+#endif
@@ -2437,6 +2437,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2637,6 +2637,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2824,6 +2824,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2617,6 +2617,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2667,6 +2667,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2664,6 +2664,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2819,6 +2819,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2632,6 +2632,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -46,4 +46,8 @@ extern int pidfd_getfd (int __pidfd, int __targetfd,
extern int pidfd_send_signal (int __pidfd, int __sig, siginfo_t *__info,
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 */
@@ -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 +28,8 @@
#include <support/xsocket.h>
#include <sys/pidfd.h>
#include <sys/wait.h>
+#include <stdlib.h>
+#include <unistd.h>
#define REMOTE_PATH "/dev/null"
@@ -102,6 +105,45 @@ do_test (void)
ppid = getpid ();
puid = getuid ();
+ /* Sanity check for invalid inputs. */
+ TEST_COMPARE (pidfd_getpid (-1), -1);
+ TEST_COMPARE (errno, EBADF);
+
+ {
+ pid_t pid = pidfd_getpid (STDOUT_FILENO);
+ TEST_COMPARE (pid, -1);
+ TEST_COMPARE (errno, EBADF);
+ }
+
+ /* Check if pidfd_getpid returns ESRCH for exited subprocess. */
+ {
+ fork_np_args_t args = {
+ .fork_np_flags = FORK_NP_PIDFD,
+ };
+ pid_t pidfork = fork_np (&args, sizeof args);
+ if (pidfork == 0)
+ _exit (EXIT_SUCCESS);
+
+ /* The process might be still running or already in zombie state, in
+ either case the PID is still allocated to the process. */
+ pid_t pid = pidfd_getpid (args.fork_np_pidfd);
+ if (pid > 0)
+ support_process_state_wait (pid, support_process_state_zombie);
+
+ siginfo_t info;
+ TEST_COMPARE (waitid (P_PIDFD, args.fork_np_pidfd, &info, WEXITED), 0);
+ TEST_COMPARE (info.si_pid, pidfork);
+ 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 (args.fork_np_pidfd);
+ TEST_COMPARE (pid, -1);
+ TEST_COMPARE (errno, ESRCH);
+
+ xclose (args.fork_np_pidfd);
+ }
+
TEST_COMPARE (socketpair (AF_UNIX, SOCK_STREAM, 0, sockets), 0);
pid_t pid = xfork ();
@@ -118,6 +160,12 @@ 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);
new file mode 100644
@@ -0,0 +1,126 @@
+/* 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/xunistd.h>
+#include <support/test-driver.h>
+#include <sys/pidfd.h>
+#include <sys/wait.h>
+#include <sys/mount.h>
+
+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");
+ if (errno == EPERM)
+ FAIL_UNSUPPORTED ("kernel does not allow pidfd_getfd, skipping test");
+ }
+
+ /* Check if pidfd_getpid returns EREMOTE for process not in current
+ namespace. */
+ {
+ fork_np_args_t child_args = {
+ .fork_np_flags = FORK_NP_PIDFD,
+ };
+ pid_t child0 = fork_np (&child_args, sizeof child_args);
+ TEST_VERIFY_EXIT (child0 >= 0);
+ if (child0 == 0)
+ {
+ /* Create another unrelated descriptor, so child2 will inherit the
+ file descriptor. */
+ fork_np_args_t subchild_args = {
+ .fork_np_flags = FORK_NP_PIDFD,
+ };
+ pid_t child1 = fork_np (&subchild_args, sizeof subchild_args);
+ TEST_VERIFY_EXIT (child1 >= 0);
+ if (child1 == 0)
+ _exit (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");
+ }
+
+ if (mount (NULL, "/", NULL, MS_REC | MS_PRIVATE, 0) != 0)
+ {
+ /* This happens if we're trying to create a nested container,
+ like if the build is running under podman, and we lack
+ priviledges. */
+ if (errno == EPERM)
+ _exit (EXIT_UNSUPPORTED);
+ else
+ _exit (EXIT_FAILURE);
+ }
+
+ pid_t child2 = xfork ();
+ if (child2 > 0)
+ {
+ int status;
+ xwaitpid (child2, &status, 0);
+ TEST_VERIFY (WIFEXITED (status));
+ xwaitpid (child1, &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)
+ {
+ if (errno == EPERM)
+ _exit (EXIT_UNSUPPORTED);
+ else
+ _exit (EXIT_FAILURE);
+ }
+
+ TEST_COMPARE (pidfd_getpid (subchild_args.fork_np_pidfd), -1);
+ TEST_COMPARE (errno, EREMOTE);
+
+ _exit (EXIT_SUCCESS);
+ }
+
+ pid_t child0pid = pidfd_getpid (child_args.fork_np_pidfd);
+
+ siginfo_t info;
+ TEST_COMPARE (waitid (P_PIDFD, child_args.fork_np_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);
+ TEST_COMPARE (info.si_pid, child0pid);
+ }
+
+ return 0;
+}
+
+#include <support/test-driver.c>
@@ -2583,6 +2583,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
@@ -2689,6 +2689,7 @@ GLIBC_2.38 strlcpy F
GLIBC_2.38 wcslcat F
GLIBC_2.38 wcslcpy F
GLIBC_2.39 fork_np F
+GLIBC_2.39 pidfd_getpid F
GLIBC_2.39 pidfd_spawn F
GLIBC_2.39 pidfd_spawnp F
GLIBC_2.39 posix_spawnattr_getcgroup_np F
This interface allows to obtain the associated process 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 sets the errno accordingly. The possible errno values are those from open, read, and close (used on procps parsing), along with: - EBADF if the FD is negative, does not have a PID associated, or if the fdinfo fields contain 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_PIDFD or waitid support), Linux 5.4 (full support), and Linux 6.2. --- NEWS | 4 + manual/process.texi | 38 ++++++ 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/clone-pidfd-support.c | 2 +- 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 | 126 ++++++++++++++++++ .../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 | 97 ++++++++++++++ sysdeps/unix/sysv/linux/procutils.h | 43 ++++++ .../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 | 48 +++++++ sysdeps/unix/sysv/linux/tst-pidfd_getpid.c | 126 ++++++++++++++++++ .../unix/sysv/linux/x86_64/64/libc.abilist | 1 + .../unix/sysv/linux/x86_64/x32/libc.abilist | 1 + 45 files changed, 525 insertions(+), 1 deletion(-) 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