@@ -47,6 +47,10 @@ Major new features:
of 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
@@ -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
@@ -397,6 +398,36 @@ Do not send a @code{SIGCHLD} termination signal when child terminates.
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 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.
+@end table
+
+This function is specific to Linux.
+@end deftypefun
+
@node Executing a File
@section Executing a File
@cindex executing a file
@@ -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
@@ -323,6 +323,7 @@ libc {
}
GLIBC_2.38 {
pidfd_fork;
+ pidfd_getpid;
pidfd_spawn;
pidfd_spawnp;
}
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
new file mode 100644
@@ -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 (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) == -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;
+}
@@ -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
@@ -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
@@ -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
@@ -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
new file mode 100644
@@ -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;
+}
new file mode 100644
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -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
@@ -62,4 +62,8 @@ extern int pidfd_send_signal (int __pidfd, int __sig, siginfo_t *__info,
process to the parent process. */
extern pid_t pidfd_fork (int *pidfd, 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 +28,9 @@
#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 +106,43 @@ 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. */
+ {
+ int pidfd;
+ pid_t pidfork = pidfd_fork (&pidfd, 0);
+ if (pidfork == 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_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 (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 +159,12 @@ 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 +1,182 @@
+/* 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;
+ pid_t pid = pidfd_fork (&pidfd, 0);
+ TEST_VERIFY_EXIT (pid >= 0);
+ if (pid == 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>
@@ -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
@@ -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
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 associatedi, or 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 | 31 +++ 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 | 47 +++++ sysdeps/unix/sysv/linux/tst-pidfd_getpid.c | 182 ++++++++++++++++++ .../unix/sysv/linux/x86_64/64/libc.abilist | 1 + .../unix/sysv/linux/x86_64/x32/libc.abilist | 1 + 44 files changed, 567 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