linux: Add openat2 (BZ 31664) azanella/bz31664-openat2

It was added on Linux 5.6, as an extension of openat.  Different
than other open-like function, the kernel only provides the LFS
variant (so files larger than 4GB always succeed, as other functions
with offset larget than off_t).  Similar to other open function,
the new symbol is a cancellable entrypoint.

The testcase added only stress some of the syscall provided
functionalities and it is based on existent kernel selftest.  Since
the prototype does not use variadic arguments, there is no need to
add fortify wrapper to catch wrong usages.

Checked on x86_64-linux-gnu.

35 files changed, 482 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index cf6078cf20..eaaa02cb4e 100644
--- a/NEWS
+++ b/NEWS
@@ -26,6 +26,10 @@ Major new features:
   more extensive verification tests for AT_SECURE programs and not meant to
   be a security feature.
 
+* On Linux, the openat2 function has been added.  It is an extension of
+  openat and provides a superset of its functionality.  It is supported only
+  in LFS mode and as other open like it is a cancellable entrypoint.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * Architectures which use a 32-bit seconds-since-epoch field in struct
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 415aa1f14d..fcb9b810b5 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -133,6 +133,7 @@ sysdep_headers += \
   bits/mman-linux.h \
   bits/mman-map-flags-generic.h \
   bits/mman-shared.h \
+  bits/openat2.h \
   bits/procfs-extra.h \
   bits/procfs-id.h \
   bits/procfs-prregset.h \
@@ -593,6 +594,7 @@ sysdep_routines += \
   open_nocancel \
   openat64_nocancel \
   openat_nocancel \
+  openat2 \
   pread64_nocancel \
   read_nocancel \
   stat_t64_cp \
@@ -607,11 +609,23 @@ sysdep_headers += \
   # sysdep_headers
 
 tests += \
+  tst-openat2 \
   tst-fallocate \
   tst-fallocate64 \
   tst-getcwd-smallbuff \
   tst-o_path-locks \
   # tests
+
+tests-special += \
+  $(objpfx)tst-openat2-consts.out \
+  # tests-special
+$(objpfx)tst-openat2-consts.out: ../sysdeps/unix/sysv/linux/tst-openat2-consts.py
+	$(sysdeps-linux-python) \
+	  ../sysdeps/unix/sysv/linux/tst-openat2-consts.py \
+	    $(sysdeps-linux-python-cc) \
+	  < /dev/null > $@ 2>&1; $(evaluate-test)
+$(objpfx)tst-openat2-consts.out: $(sysdeps-linux-python-deps)
+
 endif
 
 ifeq ($(subdir),elf)
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 268ba1b6ac..65da2b617a 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -328,6 +328,9 @@ libc {
     posix_spawnattr_getcgroup_np;
     posix_spawnattr_setcgroup_np;
   }
+  GLIBC_2.40 {
+    openat2;
+  }
   GLIBC_PRIVATE {
     # functions used in other libraries
     __syscall_rt_sigqueueinfo;
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index 68eeca1c08..0b9bd8ae62 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2748,3 +2748,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index 34c187b721..c0bd27d617 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -3095,6 +3095,7 @@ GLIBC_2.4 wcstold F
 GLIBC_2.4 wcstold_l F
 GLIBC_2.4 wprintf F
 GLIBC_2.4 wscanf F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/arc/libc.abilist b/sysdeps/unix/sysv/linux/arc/libc.abilist
index 916c18ea94..965438e7a7 100644
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@@ -2509,3 +2509,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index 1cdbc983e1..70fd425869 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -2798,6 +2798,7 @@ GLIBC_2.4 xdrstdio_create F
 GLIBC_2.4 xencrypt F
 GLIBC_2.4 xprt_register F
 GLIBC_2.4 xprt_unregister F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
index 628612b885..279aa2b8eb 100644
--- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
+++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
@@ -451,6 +451,28 @@ extern int name_to_handle_at (int __dfd, const char *__name,
 extern int open_by_handle_at (int __mountdirfd, struct file_handle *__handle,
 			      int __flags);
 
+#ifdef __has_include
+# if __has_include ("linux/openat2.h")
+#  include "linux/openat2.h"
+#  define __glibc_has_open_how 1
+# endif
+#endif
+
+#include <bits/openat2.h>
+
+/* Similar to `openat' but the arguments are packed on HOW with the size
+   USIZE.  If flags and mode from HOW are non-zero, then openat2 operates
+   like openat.
+
+   Unlike openat2, unknown or invalid flags result in an error (EINVAL),
+   rather than being ignored.  The mode must be zero unless one O_CREAT
+   or O_TMPFILE are set.
+
+   The kernel does not support legacy non-LFS interface.  */
+extern int openat2 (int __dfd, const char *__filename, struct open_how *__how,
+		    size_t __usize)
+     __nonnull ((2, 3));
+
 #endif	/* use GNU */
 
 __END_DECLS
diff --git a/sysdeps/unix/sysv/linux/bits/openat2.h b/sysdeps/unix/sysv/linux/bits/openat2.h
new file mode 100644
index 0000000000..a07984dace
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/bits/openat2.h
@@ -0,0 +1,61 @@
+/* openat2 definition.  Linux specific.
+   Copyright (C) 2024 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	_FCNTL_H
+# error "Never use <bits/openat2.h> directly; include <fcntl.h> instead."
+#endif
+
+#ifndef __glibc_has_open_how
+/* Arguments for how openat2 should open the target path.  */
+struct open_how
+{
+  __uint64_t flags;
+  __uint64_t mode;
+  __uint64_t resolve;
+};
+#endif
+
+/* how->resolve flags for openat2. */
+#ifndef RESOLVE_NO_XDEV
+# define RESOLVE_NO_XDEV	0x01 /* Block mount-point crossings
+					(includes bind-mounts).  */
+#endif
+#ifndef RESOLVE_NO_MAGICLINKS
+# define RESOLVE_NO_MAGICLINKS	0x02 /* Block traversal through procfs-style
+					"magic-links".  */
+#endif
+#ifndef RESOLVE_NO_SYMLINKS
+# define RESOLVE_NO_SYMLINKS	0x04 /* Block traversal through all symlinks
+					(implies OEXT_NO_MAGICLINKS).  */
+#endif
+#ifndef RESOLVE_BENEATH
+# define RESOLVE_BENEATH	0x08 /* Block "lexical" trickery like
+					"..", symlinks, and absolute
+					paths which escape the dirfd.  */
+#endif
+#ifndef RESOLVE_IN_ROOT
+# define RESOLVE_IN_ROOT	0x10 /* Make all jumps to "/" and ".."
+					be scoped inside the dirfd
+					(similar to chroot).  */
+#endif
+#ifndef RESOLVE_CACHED
+# define RESOLVE_CACHED		0x20 /* Only complete if resolution can be
+					completed through cached lookup. May
+					return -EAGAIN if that's not
+					possible.  */
+#endif
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index 96d45961e2..c81ea43dc1 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2785,3 +2785,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index fbcd60c2b3..23eec25d8a 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2821,6 +2821,7 @@ GLIBC_2.4 sys_errlist D 0x400
 GLIBC_2.4 sys_nerr D 0x4
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index c989b433c0..4ce2afb147 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -3005,6 +3005,7 @@ GLIBC_2.4 sys_errlist D 0x210
 GLIBC_2.4 sys_nerr D 0x4
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
index 0023ec1fa1..be76251b28 100644
--- a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
@@ -2269,3 +2269,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 439796d693..39645248af 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2948,6 +2948,7 @@ GLIBC_2.4 sys_errlist D 0x210
 GLIBC_2.4 sys_nerr D 0x4
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index 1069d3252c..2f917724de 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2834,3 +2834,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 799e508950..ae5b95bc76 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2909,6 +2909,7 @@ GLIBC_2.4 renameat F
 GLIBC_2.4 symlinkat F
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index 03d9655f26..5dc2996fcc 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2915,6 +2915,7 @@ GLIBC_2.4 renameat F
 GLIBC_2.4 symlinkat F
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index 05e402ed30..865dc5e7f1 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2817,6 +2817,7 @@ GLIBC_2.4 renameat F
 GLIBC_2.4 symlinkat F
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index 3aa81766aa..12775fdad5 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2873,3 +2873,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/openat2.c b/sysdeps/unix/sysv/linux/openat2.c
new file mode 100644
index 0000000000..a2b134bab0
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/openat2.c
@@ -0,0 +1,29 @@
+/* Linux openat2 syscall implementation.
+   Copyright (C) 2024 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 <fcntl.h>
+#include <bits/openat2.h>
+#include <sysdep-cancel.h>
+
+int
+__openat2 (int dfd, const char *filename, struct open_how *how,
+	   size_t usize)
+{
+  return SYSCALL_CANCEL (openat2, dfd, filename, how, usize);
+}
+weak_alias (__openat2, openat2)
diff --git a/sysdeps/unix/sysv/linux/or1k/libc.abilist b/sysdeps/unix/sysv/linux/or1k/libc.abilist
index c40c843aaf..2835436011 100644
--- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
+++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
@@ -2255,3 +2255,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 9714305608..3b70a56944 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -3138,6 +3138,7 @@ GLIBC_2.4 wcstold F
 GLIBC_2.4 wcstold_l F
 GLIBC_2.4 wprintf F
 GLIBC_2.4 wscanf F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index cfc2ebd3ec..10fc3c89dc 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2892,6 +2892,7 @@ GLIBC_2.4 wcstold F
 GLIBC_2.4 wcstold_l F
 GLIBC_2.4 wprintf F
 GLIBC_2.4 wscanf F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index 8c9efc5a16..713fa1d1c8 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2968,3 +2968,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
index 6397a9cb91..550ba877ef 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@@ -2512,3 +2512,4 @@ GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
 GLIBC_2.40 __riscv_hwprobe F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index 71bbf94f66..8bf9f309b7 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2712,3 +2712,4 @@ GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
 GLIBC_2.40 __riscv_hwprobe F
+GLIBC_2.40 openat2 F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index a7467e2850..08bc3d6f8b 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -3136,6 +3136,7 @@ GLIBC_2.4 wcstold F
 GLIBC_2.4 wcstold_l F
 GLIBC_2.4 wprintf F
 GLIBC_2.4 wscanf F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index fd1cb2972d..e25afff581 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2929,6 +2929,7 @@ GLIBC_2.4 wcstold F
 GLIBC_2.4 wcstold_l F
 GLIBC_2.4 wprintf F
 GLIBC_2.4 wscanf F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index 449d92bbc5..bdd9c600f0 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2825,6 +2825,7 @@ GLIBC_2.4 sys_errlist D 0x210
 GLIBC_2.4 sys_nerr D 0x4
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index e615be759a..b20dd43d47 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -3157,6 +3157,7 @@ GLIBC_2.4 wcstold F
 GLIBC_2.4 wcstold_l F
 GLIBC_2.4 wprintf F
 GLIBC_2.4 wscanf F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index bd36431dd7..19981aa981 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2793,6 +2793,7 @@ GLIBC_2.4 sys_errlist D 0x430
 GLIBC_2.4 sys_nerr D 0x4
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/tst-openat2-consts.py b/sysdeps/unix/sysv/linux/tst-openat2-consts.py
new file mode 100755
index 0000000000..1623fafd94
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-openat2-consts.py
@@ -0,0 +1,63 @@
+#!/usr/bin/python3
+# Test that glibc's sys/openat2.h constants match the kernel's.
+# Copyright (C) 2024 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/openat2.h constants "
+        "match the kernel's.")
+    parser.add_argument('--cc', metavar='CC',
+                        help='C compiler (including options) to use')
+    args = parser.parse_args()
+
+    if glibcextract.compile_c_snippet(
+            '#include <linux/openat2.h>',
+            args.cc).returncode != 0:
+        sys.exit (77)
+
+    linux_version_headers = glibcsyscalls.linux_kernel_version(args.cc)
+    # Constants in glibc were updated to match Linux v6.8.  When glibc
+    # constants are updated this value should be updated to match the
+    # released kernel version from which the constants were taken.
+    linux_version_glibc = (6, 8)
+    def check(cte, exclude=None):
+        return glibcextract.compare_macro_consts(
+                '#define _FCNTL_H\n'
+                '#include <stdint.h>\n'
+                '#include <bits/openat2.h>\n',
+                '#include <asm/fcntl.h>\n'
+                '#include <linux/openat2.h>\n',
+                args.cc,
+                cte,
+                exclude,
+                linux_version_glibc > linux_version_headers,
+                linux_version_headers > linux_version_glibc)
+
+    status = check('RESOLVE.*')
+    sys.exit(status)
+
+if __name__ == '__main__':
+    main()
diff --git a/sysdeps/unix/sysv/linux/tst-openat2.c b/sysdeps/unix/sysv/linux/tst-openat2.c
new file mode 100644
index 0000000000..6936b9fcef
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-openat2.c
@@ -0,0 +1,259 @@
+/* Linux openat2 tests.
+   Copyright (C) 2024 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/>.  */
+
+/* openat2 is only support in LFS mode.  */
+#define _FILE_OFFSET_BITS 64
+
+#include <array_length.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+
+static int dir_fd;
+
+static void
+do_prepare (int argc, char *argv[])
+{
+  char *temp_dir = support_create_temp_directory ("tst-openat2");
+  dir_fd = xopen (temp_dir, O_RDONLY | O_DIRECTORY, 0);
+}
+#define PREPARE do_prepare
+
+static int
+do_test_struct (void)
+{
+  static struct struct_test
+  {
+    struct open_how_ext
+    {
+      struct open_how inner;
+      int extra1;
+      int extra2;
+      int extra3;
+    } arg;
+    size_t size;
+    int err;
+  } tests[] =
+  {
+    {
+      /* Zero size.  */
+      .arg.inner.flags = O_RDONLY,
+      .size = 0,
+      .err = EINVAL,
+    },
+    {
+      /* Normal struct.  */
+      .arg.inner.flags = O_RDONLY,
+      .size = sizeof (struct open_how),
+    },
+    {
+      /* Larger struct, zeroed out the unused values.  */
+      .arg.inner.flags = O_RDONLY,
+      .size = sizeof (struct open_how_ext),
+    },
+    {
+      /* Larger struct, non-zeroed out the unused values.  */
+      .arg.inner.flags = O_RDONLY,
+      .arg.extra1 = 0xdeadbeef,
+      .size = sizeof (struct open_how_ext),
+      .err = E2BIG,
+    },
+    {
+      /* Larger struct, non-zeroed out the unused values.  */
+      .arg.inner.flags = O_RDONLY,
+      .arg.extra2 = 0xdeadbeef,
+      .size = sizeof (struct open_how_ext),
+      .err = E2BIG,
+    },
+  };
+
+  for (struct struct_test *t = tests; t != array_end (tests); t++)
+    {
+      int fd = openat2 (AT_FDCWD, ".", (struct open_how *) &t->arg, t->size);
+      if (fd == -1 && errno == ENOSYS)
+	FAIL_UNSUPPORTED ("openat2 is not supported by the kernel");
+
+      if (t->err != 0)
+	{
+	  TEST_COMPARE (fd, -1);
+	  TEST_COMPARE (errno, t->err);
+	}
+      else
+	TEST_VERIFY (fd >= 0);
+    }
+
+  return 0;
+}
+
+static int
+do_test_flags (void)
+{
+  static struct flag_test
+  {
+    struct open_how how;
+    int err;
+  } tests[] =
+  {
+    /* O_TMPFILE is incompatible with O_PATH and O_CREAT.  */
+    { .how.flags = O_TMPFILE | O_PATH | O_RDWR, .err = EINVAL },
+    { .how.flags = O_TMPFILE | O_CREAT | O_RDWR, .err = EINVAL },
+
+    /* O_PATH only permits certain other flags to be set ...  */
+    { .how.flags = O_PATH | O_CLOEXEC },
+    { .how.flags = O_PATH | O_DIRECTORY },
+    { .how.flags = O_PATH | O_NOFOLLOW },
+    /* ... and others are absolutely not permitted. */
+    { .how.flags = O_PATH | O_RDWR, .err = EINVAL },
+    { .how.flags = O_PATH | O_CREAT, .err = EINVAL },
+    { .how.flags = O_PATH | O_EXCL, .err = EINVAL },
+    { .how.flags = O_PATH | O_NOCTTY, .err = EINVAL },
+    { .how.flags = O_PATH | O_DIRECT, .err = EINVAL },
+
+    /* ->mode must only be set with O_{CREAT,TMPFILE}. */
+    { .how.flags = O_RDONLY, .how.mode = 0600, .err = EINVAL },
+    { .how.flags = O_PATH,   .how.mode = 0600, .err = EINVAL },
+    { .how.flags = O_CREAT,  .how.mode = 0600 },
+    { .how.flags = O_TMPFILE | O_RDWR, .how.mode = 0600 },
+    /* ->mode must only contain 0777 bits. */
+    { .how.flags = O_CREAT, .how.mode = 0xFFFF, .err = EINVAL },
+    { .how.flags = O_CREAT, .how.mode = 0xC000000000000000ULL, .err = EINVAL },
+    { .how.flags = O_TMPFILE | O_RDWR, .how.mode = 0x1337, .err = EINVAL },
+    { .how.flags = O_TMPFILE | O_RDWR, .how.mode = 0x0000A00000000000ULL,
+      .err = EINVAL },
+
+    /* ->resolve flags must not conflict. */
+    { .how.flags = O_RDONLY,
+      .how.resolve = RESOLVE_BENEATH | RESOLVE_IN_ROOT,
+      .err = EINVAL },
+
+    /* ->resolve must only contain RESOLVE_* flags.  */
+    { .how.flags = O_RDONLY,
+      .how.resolve = 0x1337, .err = EINVAL },
+    { .how.flags = O_CREAT,
+      .how.resolve = 0x1337, .err = EINVAL },
+    { .how.flags = O_TMPFILE | O_RDWR,
+      .how.resolve = 0x1337, .err = EINVAL },
+    { .how.flags = O_PATH,
+      .how.resolve = 0x1337, .err = EINVAL },
+
+    /* currently unknown upper 32 bit rejected.  */
+    { .how.flags = O_RDONLY | (1ULL << 63),
+      .how.resolve = 0, .err = EINVAL },
+  };
+
+  for (struct flag_test *t = tests; t != array_end (tests); t++)
+    {
+      char *path;
+      if (t->how.flags & O_CREAT)
+	{
+	  int temp_fd = create_temp_file ("tst-openat2.", &path);
+	  TEST_VERIFY_EXIT (temp_fd != -1);
+	  xunlink (path);
+	}
+      else
+	path = (char *) ".";
+
+      int fd = openat2 (AT_FDCWD, path, &t->how, sizeof (struct open_how));
+      if (fd != 0 && errno == EOPNOTSUPP)
+	{
+	  /* Skip the testcase if FS does not support the operation (e.g.
+	     valid O_TMPFILE on NFS).  */
+	  continue;
+	}
+
+      if (t->err != 0)
+	{
+	  TEST_COMPARE (fd, -1);
+	  TEST_COMPARE (errno, t->err);
+	}
+      else
+	TEST_VERIFY (fd >= 0);
+    }
+
+  return 0;
+}
+
+static int
+do_test_basic (void)
+{
+  int fd;
+
+  fd = openat2 (dir_fd,
+		"some-file",
+		&(struct open_how)
+		{
+		  .flags = O_CREAT|O_RDWR|O_EXCL,
+		  .mode = 0666,
+		},
+		sizeof (struct open_how));
+  TEST_VERIFY (fd != -1);
+
+  xwrite (fd, "hello", 5);
+
+  /* Before closing the file, try using this file descriptor to open
+     another file.  This must fail.  */
+  {
+    int fd2 = openat2 (fd,
+		       "should-not-work",
+		       &(struct open_how)
+		       {
+			 .flags = O_CREAT|O_RDWR|O_EXCL,
+			 .mode = 0666,
+		       },
+		       sizeof (struct open_how));
+    TEST_COMPARE (fd2, -1);
+    TEST_COMPARE (errno, ENOTDIR);
+  }
+
+  /* Remove the created file.  */
+  int cwdfd = xopen (".", O_RDONLY | O_DIRECTORY, 0);
+  TEST_COMPARE (fchdir (dir_fd), 0);
+  xunlink ("some-file");
+  TEST_COMPARE (fchdir (cwdfd), 0);
+
+  xclose (dir_fd);
+  xclose (cwdfd);
+
+  fd = openat2 (dir_fd,
+		"some-file",
+		&(struct open_how)
+		{
+		  .flags = O_CREAT|O_RDWR|O_EXCL,
+		  .mode = 0666,
+		},
+		sizeof (struct open_how));
+  TEST_COMPARE (fd, -1);
+  TEST_COMPARE (errno, EBADF);
+
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  do_test_struct ();
+  do_test_flags ();
+  do_test_basic ();
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index aea7848ed6..a7f177c8a8 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2744,6 +2744,7 @@ GLIBC_2.4 sys_errlist D 0x420
 GLIBC_2.4 sys_nerr D 0x4
 GLIBC_2.4 unlinkat F
 GLIBC_2.4 unshare F
+GLIBC_2.40 openat2 F
 GLIBC_2.5 __readlinkat_chk F
 GLIBC_2.5 inet6_opt_append F
 GLIBC_2.5 inet6_opt_find F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 4ab3681914..00dfc8f1e7 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2763,3 +2763,4 @@ GLIBC_2.39 stdc_trailing_zeros_ui F
 GLIBC_2.39 stdc_trailing_zeros_ul F
 GLIBC_2.39 stdc_trailing_zeros_ull F
 GLIBC_2.39 stdc_trailing_zeros_us F
+GLIBC_2.40 openat2 F