linux: Add pidfd_open

This was added on Linux 5.3 (32fcb426ec001cb6d5a4a195091a8486ea77e2df)
as a way to retrieve a pid file descriptors for process that has not
been created CLONE_PIDFD (by usual fork/clone).

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

NEWS

@@ -16,6 +16,10 @@ Major new features:
   -z pack-relative-relocs option, which is supported for some targets
   in recent binutils versions.  Lazy binding doesn't apply to DT_RELR.
 
+* On Linux, the pidfd_open function has been added.  The pidfd functionality
+  provides access to a process while avoiding the issue of PID reuse on
+  tranditional Unix systems.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * Support for prelink will be removed in the next release; this includes

sysdeps/unix/sysv/linux/Makefile

@@ -113,7 +113,8 @@ sysdep_headers += sys/mount.h sys/acct.h \
 		  bits/types/struct_shmid64_ds.h \
 		  bits/types/struct_shmid64_ds_helper.h \
 		  bits/pthread_stack_min.h bits/pthread_stack_min-dynamic.h \
-		  sys/rseq.h bits/rseq.h
+		  sys/rseq.h bits/rseq.h \
+		  sys/pidfd.h
 
 tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
 	 tst-quota tst-sync_file_range tst-sysconf-iov_max tst-ttyname \
@@ -240,6 +241,14 @@ $(objpfx)tst-mman-consts.out: ../sysdeps/unix/sysv/linux/tst-mman-consts.py
 	  < /dev/null > $@ 2>&1; $(evaluate-test)
 $(objpfx)tst-mman-consts.out: $(sysdeps-linux-python-deps)
 
+tests-special += $(objpfx)tst-pidfd-consts.out
+$(objpfx)tst-pidfd-consts.out: ../sysdeps/unix/sysv/linux/tst-pidfd-consts.py
+	$(sysdeps-linux-python) \
+	  ../sysdeps/unix/sysv/linux/tst-pidfd-consts.py \
+	    $(sysdeps-linux-python-cc) \
+	  < /dev/null > $@ 2>&1; $(evaluate-test)
+$(objpfx)tst-pidfd-consts.out: $(sysdeps-linux-python-deps)
+
 tst-rseq-disable-ENV = GLIBC_TUNABLES=glibc.pthread.rseq=0
 
 endif # $(subdir) == misc

sysdeps/unix/sysv/linux/Versions

@@ -299,6 +299,9 @@ libc {
 %endif
     epoll_pwait2;
   }
+  GLIBC_2.36 {
+    pidfd_open;
+  }
   GLIBC_PRIVATE {
     # functions used in other libraries
     __syscall_rt_sigqueueinfo;

sysdeps/unix/sysv/linux/aarch64/libc.abilist

@@ -2616,3 +2616,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/alpha/libc.abilist

@@ -2713,6 +2713,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/arc/libc.abilist

@@ -2377,3 +2377,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/arm/be/libc.abilist

@@ -496,6 +496,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
 GLIBC_2.4 _IO_2_1_stdin_ D 0xa0

sysdeps/unix/sysv/linux/arm/le/libc.abilist

@@ -493,6 +493,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
 GLIBC_2.4 _IO_2_1_stdin_ D 0xa0

sysdeps/unix/sysv/linux/csky/libc.abilist

@@ -2652,3 +2652,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/hppa/libc.abilist

@@ -2601,6 +2601,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/i386/libc.abilist

@@ -2785,6 +2785,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/ia64/libc.abilist

@@ -2551,6 +2551,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist

@@ -497,6 +497,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0x98
 GLIBC_2.4 _IO_2_1_stdin_ D 0x98

sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist

@@ -2728,6 +2728,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/microblaze/be/libc.abilist

@@ -2701,3 +2701,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/microblaze/le/libc.abilist

@@ -2698,3 +2698,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist

@@ -2693,6 +2693,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist

@@ -2691,6 +2691,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist

@@ -2699,6 +2699,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist

@@ -2602,6 +2602,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/nios2/libc.abilist

@@ -2740,3 +2740,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/or1k/libc.abilist

@@ -2123,3 +2123,4 @@ GLIBC_2.35 wprintf F
 GLIBC_2.35 write F
 GLIBC_2.35 writev F
 GLIBC_2.35 wscanf F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist

@@ -2755,6 +2755,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist

@@ -2788,6 +2788,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist

@@ -2510,6 +2510,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist

@@ -2812,3 +2812,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist

@@ -2379,3 +2379,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist

@@ -2579,3 +2579,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F

sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist

@@ -2753,6 +2753,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist

@@ -2547,6 +2547,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/sh/be/libc.abilist

@@ -2608,6 +2608,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/sh/le/libc.abilist

@@ -2605,6 +2605,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist

@@ -2748,6 +2748,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F

sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist

@@ -2574,6 +2574,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/sys/pidfd.h

@@ -0,0 +1,33 @@
+/* Wrapper for file descriptors that refers to a process functions.
+   Copyright (C) 2022 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 _PIDFD_H
+
+#include <fcntl.h>
+#include <bits/types/siginfo_t.h>
+
+#define PIDFD_NONBLOCK O_NONBLOCK
+
+/* Returns a file descriptor that refers to the process PID.  The
+   close-on-exec is set on the file descriptor.
+
+   The FLAGS argument is reserved for future use, it must be specified
+   as 0.  */
+extern int pidfd_open (__pid_t __pid, unsigned int __flags) __THROW;
+
+#endif /* _PIDFD_H  */

sysdeps/unix/sysv/linux/syscalls.list

@@ -39,6 +39,7 @@ munlock		-	munlock		i:aU	munlock
 munlockall	-	munlockall	i:	munlockall
 nfsservctl	EXTRA	nfsservctl	i:ipp	__compat_nfsservctl	nfsservctl@GLIBC_2.0:GLIBC_2.28
 pipe2		-	pipe2		i:fi	__pipe2		pipe2
+pidfd_open	EXTRA	pidfd_open	i:iU	pidfd_open
 pivot_root	EXTRA	pivot_root	i:ss	pivot_root
 query_module	EXTRA	query_module	i:sipip	__compat_query_module	query_module@GLIBC_2.0:GLIBC_2.23
 quotactl	EXTRA	quotactl	i:isip	quotactl

sysdeps/unix/sysv/linux/tst-pidfd-consts.py

@@ -0,0 +1,49 @@
+#!/usr/bin/python3
+# Test that glibc's sys/pidfd.h constants match the kernel's.
+# Copyright (C) 2022 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/>.
+
+import argparse
+import sys
+
+import glibcextract
+import glibcsyscalls
+
+
+def main():
+    """The main entry point."""
+    parser = argparse.ArgumentParser(
+        description="Test that glibc's sys/pidfd.h constants "
+        "match the kernel's.")
+    parser.add_argument('--cc', metavar='CC',
+                        help='C compiler (including options) to use')
+    args = parser.parse_args()
+
+    linux_version_headers = glibcsyscalls.linux_kernel_version(args.cc)
+    linux_version_glibc = (5, 16)
+    sys.exit(glibcextract.compare_macro_consts(
+                '#include <sys/pidfd.h>\n',
+                '#include <asm/fcntl.h>\n'
+                '#include <linux/pidfd.h>\n',
+                args.cc,
+                'PIDFD_.*',
+                None,
+                linux_version_glibc > linux_version_headers,
+                linux_version_headers > linux_version_glibc))
+
+if __name__ == '__main__':
+    main()

sysdeps/unix/sysv/linux/x86_64/64/libc.abilist

@@ -2525,6 +2525,7 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F

sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist

@@ -2631,3 +2631,4 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 pidfd_open F