[PATCH] linux: Add openat2 (BZ 31664)
Adhemerval Zanella Netto
adhemerval.zanella@linaro.org
Mon Nov 10 13:52:40 GMT 2025
On 06/11/25 14:43, Carlos O'Donell wrote:
> On 10/29/25 4:05 PM, Adhemerval Zanella wrote:
>> The openat2 syscall was added on Linux 5.6, as an extension of openat.
>> Unlike other open-like functions, the kernel only provides the LFS
>> variant (so files larger than 4GB always succeed, unlike other
>> functions with an offset larger than off_t). Also, similar to other
>> open functions, the new symbol is a cancellable entrypoint.
>>
>> The test case added only stress tests for some of the syscalls' provided
>> functionality, and it is based on an existing kernel self-test. Since
>> the prototype does not use variadic arguments, there is no need to add
>> a fortify wrapper to catch wrong usages.
>>
>> The documentation mostly defers to the Linux manual pages.
>>
>> Gnulib added an openat2 module, which uses read-only for the open_how
>> argument [1]. There is no clear indication whether the kernel will
>> indeed use the argument as in-out, how it would do so, or for which
>> kind of functionality [2]. Also, adding a potentially different prototype
>> than gnulib only would add extra unnecessary friction and extra
>> wrappers to handle it.
>>
>> Checked on x86_64-linux-gnu.
>
> I experimented with Claude Code to do an LLM-assisted review.
>
> Notes below. Nothing is copyrightable so we should be OK accepting these
> changes despite not yet having an LLM content policy.
>
> Please post a v2.
>
> Mostly comment and manual changes.
>
>> [1] https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=0b97ffdf32bdab909d02449043447237273df75e
>> [2] https://sourceware.org/pipermail/libc-alpha/2025-September/169740.html
>> ---
>> NEWS | 4 +
>> manual/llio.texi | 111 ++++
>> sysdeps/unix/sysv/linux/Makefile | 19 +
>> sysdeps/unix/sysv/linux/Versions | 3 +
>> 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/bits/fcntl-linux.h | 23 +
>> sysdeps/unix/sysv/linux/bits/openat2.h | 61 +++
>> sysdeps/unix/sysv/linux/csky/libc.abilist | 1 +
>> sysdeps/unix/sysv/linux/hppa/libc.abilist | 1 +
>> sysdeps/unix/sysv/linux/i386/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/openat2.c | 29 ++
>> sysdeps/unix/sysv/linux/or1k/libc.abilist | 1 +
>> .../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 +
>> .../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/tst-openat2-consts.py | 63 +++
>> sysdeps/unix/sysv/linux/tst-openat2-lfs.c | 1 +
>> sysdeps/unix/sysv/linux/tst-openat2.c | 482 ++++++++++++++++++
>> .../unix/sysv/linux/x86_64/64/libc.abilist | 1 +
>> .../unix/sysv/linux/x86_64/x32/libc.abilist | 1 +
>> 42 files changed, 828 insertions(+)
>> create mode 100644 sysdeps/unix/sysv/linux/bits/openat2.h
>> create mode 100644 sysdeps/unix/sysv/linux/openat2.c
>> create mode 100755 sysdeps/unix/sysv/linux/tst-openat2-consts.py
>> create mode 100644 sysdeps/unix/sysv/linux/tst-openat2-lfs.c
>> create mode 100644 sysdeps/unix/sysv/linux/tst-openat2.c
>>
>> diff --git a/NEWS b/NEWS
>> index 4b1f259fde6..841636ceae9 100644
>> --- a/NEWS
>> +++ b/NEWS
>> @@ -13,6 +13,10 @@ Major new features:
>> * The ISO C23 memalignment function has been added.
>> +* 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 it is a cancellable entrypoint.
>
> OK.
>
>> +
>> Deprecated and removed features, and other changes affecting compatibility:
>> * Support for dumped heaps has been removed - malloc_set_state() now always
>> diff --git a/manual/llio.texi b/manual/llio.texi
>> index 806ff0a27d5..0bd9e4e1239 100644
>> --- a/manual/llio.texi
>> +++ b/manual/llio.texi
>> @@ -218,6 +218,117 @@ new, extended API using 64 bit file sizes and offsets transparently
>> replaces the old API.
>> @end deftypefun
>> +@deftp {Data Type} {struct open_how}
>> +@standards{Linux, fcntl.h}
>> +The @code{open_how} structure describes how to open a file using @code{openat2}.
>> +
>> +@strong{Portability note:} In the future, additional fields can be added
>> +to @code{struct open_how} at the end, so that the size of this data
>> +type changes. Do not use it in places where this matters, such as
>> +structure fields in installed header files, where such a change could
>> +affect the application binary interface (ABI).
>> +
>> +The following generic fields are available.
>> +
>> +@table @code
>> +@item flags
>> +This field specifies the file creation and file status flags to use when
>> +opening the file.
>> +All of the @code{O_*} flags defined for @code{openat} are valid.
>> +Unlike than @code{openat}, @code{openat2} returns an error for unknown
>
> s/than//g
>
> Caught by Claude Code in LLM-assited review.
Ack.
>
>> +or conflicting values.
>> +
>> +@item mode
>> +This field specifies the mode for the new file, similar to @code{mode}
>> +argument of @code{openat}. Unlike @code{openat}, @code{openat2}
>> +returns an error for invalid values (i.e., values greater than @code{07777}).
>> +
>> +@item resolve
>> +This is a bitmask of flags that affect the resolution of file name components.
>> +Unlike @code{O_NOFOLLOW}, it affects all file name components, not just the
>> +last one. The following flags are available.
>> +
>> +@table @code
>> +@item RESOLVE_NO_XDEV
>> +Disallow traversal of mount points during path resolution (including all
>> +bind mounts).
>> +
>> +@item RESOLVE_NO_MAGICLINKS
>> +Disallow all @strong{magic-link} resolution during path resolution. Magic
>> +links are symbolic link-like objects that are found in @strong{procfs};
>> +for example the @code{/proc/pid/exe}.
>> +
>> +@item RESOLVE_NO_SYMLINKS
>> +Disallow resolution of symbolic links during path resolution.
>> +This option implies @code{RESOLVE_NO_MAGICLINKS}.
>> +
>> +@item RESOLVE_BENEATH
>> +Do not permit the path resolution to succeed if any component of the
>> +resolution is not a descendant of the directory indicated by @var{dirfd}.
>> +This cause absolute symbolic links and absolute values of @var{pathname}
>
> s/cause/causes/g
>
> Caught by Claude Code in LLM-assited review.
Ack.
>
>> +to be reject.
>> +
>> +@item RESOLVE_IN_ROOT
>> +Treat the directory referred by @var{dirfd} as the root directory
>
> s/referred by/referred to by/g
>
> Caught by Claude Code in LLM-assited review.
Ack.
>
>> +while resolving the @var{pathname}.
>> +Absolute symbolic links and absolute values of @var{pathnames} are
>> +interpreted relative to @var{dirfd}.
>> +The effect of this flag is as though the calling process has used
>> +@code{chroot} to modify its root direftory.
>
> s/direftory/directory/g
>
> Caught by Claude Code in LLM-assited review.
Ack.
>
>> +
>> +@item RESOLVE_CACHED
>> +Make the open operation fail unless all path components are already
>> +present in the kernel's lookup cache.
>> +@end table
>
> OK. Table is correct and contains the data I would expect.
>
> Asked Claude Code to cross-check and it confirmed what I already knew.
>
>> +
>> +@end table
>> +
>> +For additional information, consult the manual page @manpageurl{openat2,2}.
>> +@xref{Linux Kernel}.
>> +@end deftp
>> +
>> +
>> +@deftypefun int openat2 (int @var{dirfd}, const char *restrict @var{pathname}, const struct open_how *restrict @var{how}, size_t @var{size})
>> +@standards{Linux, fcntl.h}
>> +@safety{@mtsafe{}@assafe{}@acsafe{}}
>> +This function is an extension of the @code{openat} and provides a superset of its
>> +functionality. @xref{Descriptor-Relative Access}.
>> +
>> +The @var{size} argument must equal @code{sizeof *@var{how}}. For portability
>> +to future API versions that extend @code{struct open_how}, @code{*@var{how}}
>> +should be initialized either by a struct initializer or by @code{memset} to zero.
>> +
>> +On failure, @code{openat2} returns @math{-1} and sets @code{errno}. It can
>> +fail for any of the reasons @code{openat} fails, plus the following reasons:
>> +
>> +@table @code
>> +@item E2BIG
>> +An extension that the kernel does support was specified in @code{*@var{how}},
>
> s/does/does not/g
>
> Caught by Claude Code in LLM-assisted review.
Ack.
>
>> +or a larger struct was used with non-zero members.
>> +
>> +@item EAGAIN
>> +@code{@var{how}->resolve} contains either RESOLVE_IN_ROOT or RESOLVE_BENEATH, and
>> +the kernel could not ensure that @code{".."} component did not escape. Or
>> +@code{RESOLVE_CACHED} was set, and the open operation cannot be performed
>> +using only cached information.
>> +
>> +@item EINVAL
>> +And unknown flag or invalid value was used on @code{*@var{how}}; or
>
> s/And/An/g
>
> Caught by Claude Code in LLM-assited review.
Ack.
>
>> +@code{@var{how}->mode} is non-zero, but @code{@var{how}->flags} does not contain
>> +@code{O_CREAT} or@code{O_TMPFILE}, or @var{size} is smaller than the ones supported
>
> s/or@/or @/g
>
> Caught by Claude Code in LLM-assited review.
Ack.
>
>> +by the kernel.
>> +@end table
>> +
>> +It can also return all the errors @code{openat} returns, or other errors
>> +due to new members added by the kernel.
>> +
>> +Similar to @code{openat}, @code{openat2} is a cancellation point.
>> +
>> +Unlike other @code{open}-like functions, this function ignores
>> +@code{_FILE_OFFSET_BITS} and always operates in large file mode.
>> +@end deftypefun
>
> OK.
>
>> +
>> +
>> @deftypefn {Obsolete function} int creat (const char *@var{filename}, mode_t @var{mode})
>> @standards{POSIX.1, fcntl.h}
>> @safety{@prelim{}@mtsafe{}@assafe{}@acsafe{@acsfd{}}}
>> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
>> index d1ac6409b18..971c97889b2 100644
>> --- a/sysdeps/unix/sysv/linux/Makefile
>> +++ b/sysdeps/unix/sysv/linux/Makefile
>> @@ -135,6 +135,7 @@ sysdep_headers += \
>> bits/mman-linux.h \
>> bits/mman-map-flags-generic.h \
>> bits/mman-shared.h \
>> + bits/openat2.h \
>
> OK.
>
>> bits/procfs-extra.h \
>> bits/procfs-id.h \
>> bits/procfs-prregset.h \
>> @@ -620,6 +621,7 @@ sysdep_routines += \
>> internal_statvfs \
>> open64_nocancel \
>> open_nocancel \
>> + openat2 \
>
> OK.
>
>> openat64_nocancel \
>> openat_nocancel \
>> pread64_nocancel \
>> @@ -640,7 +642,24 @@ tests += \
>> tst-fallocate64 \
>> tst-getcwd-smallbuff \
>> tst-o_path-locks \
>> + tst-openat2 \
>> + tst-openat2-lfs \
>
> OK. Two new tests.
>
>> # 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: $(sysdeps-linux-python-deps)
>> +
>> +# openat2 only provides LFS support, the tests check if the interface is correctly
>> +# provided regardless of the flags.
>> +CFLAGS-tst-openat2-lfs.c += -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE
>
> OK.
>
>> +
>> endif
>> ifeq ($(subdir),elf)
>> diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
>> index 585dec7689e..7f67562eeaf 100644
>> --- a/sysdeps/unix/sysv/linux/Versions
>> +++ b/sysdeps/unix/sysv/linux/Versions
>> @@ -339,6 +339,9 @@ libc {
>> cfsetispeed;
>> cfsetspeed;
>> }
>> + GLIBC_2.43 {
>> + openat2;
>> + }
>
> OK.
>
>> 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 ecb1be5bb49..9055099e953 100644
>> --- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
>> @@ -2770,4 +2770,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
>> index 55c22da87f3..6ef24e0ab73 100644
>> --- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
>> @@ -3117,6 +3117,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/arc/libc.abilist b/sysdeps/unix/sysv/linux/arc/libc.abilist
>> index b1e5855b5dd..2f5e7db4b7c 100644
>> --- a/sysdeps/unix/sysv/linux/arc/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
>> @@ -2531,4 +2531,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
>> index 1ac00b8303f..f783d7fa7eb 100644
>> --- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
>> @@ -2823,6 +2823,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
>> index cf92ab4adae..239e8a41397 100644
>> --- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
>> @@ -2820,6 +2820,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
>> index f425a4bf22b..650c29d7df8 100644
>> --- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
>> +++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
>> @@ -455,6 +455,29 @@ 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),
>
> Typo. s/Unlike openat2/Unlike openat/g.
>
> Caught by me and Claude Code in an LLM-assisted review.
>
Ack.
>> + 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 *__restrict __filename,
>> + const struct open_how *__restrict __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 00000000000..6059095bc13
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/bits/openat2.h
>> @@ -0,0 +1,61 @@
>> +/* openat2 definition. Linux specific.
>> + Copyright (C) 2025 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). */
>
> There is no such thing as OEXT_NO_MAGICLINKS?
>
> This looks like a typo in the Linux kernel headers comment?
Indeed, I will remove the comment.
>
> Also caught by Claude Code in LLM-assisted review.
>
> Typo appears 3 times in upstream Linux kernel.
>
>> +#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. */
>
> OK. Constants match.
>
>> +#endif
>> diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
>> index 5d00604da52..5fc67a0ecc8 100644
>> --- a/sysdeps/unix/sysv/linux/csky/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
>> @@ -2807,4 +2807,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
>> index 4011dc5cc09..601f4cef1c5 100644
>> --- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
>> @@ -2844,6 +2844,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
>> index 3757e41e6f4..d87bac95f1e 100644
>> --- a/sysdeps/unix/sysv/linux/i386/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
>> @@ -3027,6 +3027,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
>> index 8bbb9503862..59ec6a2d920 100644
>> --- a/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/loongarch/lp64/libc.abilist
>> @@ -2291,4 +2291,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
>> index 74b36e84b6f..46f329c2c82 100644
>> --- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
>> @@ -2803,6 +2803,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
>> index b5cf2998c36..3df90353855 100644
>> --- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
>> @@ -2970,6 +2970,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
>> index 547e21eb66c..ab77cdd6bdf 100644
>> --- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
>> @@ -2856,4 +2856,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
>> index f98407da281..503606816af 100644
>> --- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
>> @@ -2853,4 +2853,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
>> index 1e207c97c33..231f56378c1 100644
>> --- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
>> @@ -2933,6 +2933,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
>> index f947cbb8f52..80e97539be3 100644
>> --- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
>> @@ -2907,6 +2907,7 @@ GLIBC_2.4 renameat F
>> GLIBC_2.4 symlinkat F
>> GLIBC_2.4 unlinkat F
>> GLIBC_2.4 unshare F
>> +GLIBC_2.41 openat2 F
>> GLIBC_2.41 sched_getattr F
>> GLIBC_2.41 sched_setattr F
>> GLIBC_2.42 __inet_ntop_chk F
>> diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
>> index d44b0c41c0d..7f499cd71af 100644
>> --- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
>> @@ -2939,6 +2939,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
>> index bdcde501656..8c64d378162 100644
>> --- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
>> @@ -2841,6 +2841,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/openat2.c b/sysdeps/unix/sysv/linux/openat2.c
>> new file mode 100644
>> index 00000000000..77d16915eeb
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/openat2.c
>> @@ -0,0 +1,29 @@
>> +/* Linux openat2 syscall implementation.
>> + Copyright (C) 2025 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 *__restrict filename,
>> + const struct open_how *__restrict 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 f2117e1dcc0..451b99196a3 100644
>> --- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
>> @@ -2281,4 +2281,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
>> index 6e887bcca48..8201d131032 100644
>> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
>> @@ -3160,6 +3160,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
>> index 247cbc2c8d8..07c9a211892 100644
>> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
>> @@ -3205,6 +3205,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
>> index 70fe1f2de82..fe6d427ec4f 100644
>> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
>> @@ -2914,6 +2914,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
>> index 8f82f6c6480..d17b57b51fd 100644
>> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
>> @@ -2990,4 +2990,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
>> index 57b5790914d..dad06299831 100644
>> --- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
>> @@ -2534,4 +2534,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
>> index faeaebc5003..ea721159fae 100644
>> --- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
>> @@ -2734,4 +2734,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
>> index 62a71df1013..34c8b2b85ef 100644
>> --- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
>> @@ -3158,6 +3158,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
>> index 01681666e85..bd1d36bc1f1 100644
>> --- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
>> @@ -2951,6 +2951,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
>> index b93a621870a..681efefe897 100644
>> --- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
>> @@ -2850,6 +2850,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
>> index fb41f72160b..8dc20a90be5 100644
>> --- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
>> @@ -2847,6 +2847,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
>> index cbe10bb14c7..830c81ef15f 100644
>> --- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
>> @@ -3181,6 +3181,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
>> index 480dc5e8cd8..bc0207cf009 100644
>> --- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
>> @@ -2817,6 +2817,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append 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 00000000000..9b65d184d73
>> --- /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) 2025 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-lfs.c b/sysdeps/unix/sysv/linux/tst-openat2-lfs.c
>> new file mode 100644
>> index 00000000000..85962d30c17
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/tst-openat2-lfs.c
>> @@ -0,0 +1 @@
>> +#include "tst-openat2.c"
>> diff --git a/sysdeps/unix/sysv/linux/tst-openat2.c b/sysdeps/unix/sysv/linux/tst-openat2.c
>> new file mode 100644
>> index 00000000000..e52e3870d04
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/tst-openat2.c
>> @@ -0,0 +1,482 @@
>> +/* Linux openat2 tests.
>> + Copyright (C) 2025 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 <array_length.h>
>> +#include <errno.h>
>> +#include <fcntl.h>
>> +#include <libgen.h>
>> +#include <stdint.h>
>> +
>> +#include <support/check.h>
>> +#include <support/support.h>
>> +#include <support/temp_file.h>
>> +#include <support/test-driver.h>
>> +#include <support/xunistd.h>
>> +
>> +static int dir_fd;
>> +static char *temp_dir;
>> +static char *temp_subdir;
>> +static char *temp_some_file;
>> +
>> +#define TEST_DIR_LINK "test_dir_link"
>> +#define TEST_DIR_LINK_2 "test_dir_link_2"
>> +#define TEMP_DIR_LINK "temp_dir_link"
>> +#define INVALID_LINK "invalid-link"
>> +#define VALID_LINK "valid-link"
>> +
>> +static void
>> +create_symlink (const char *target, const char *linkpath)
>> +{
>> + TEST_VERIFY_EXIT (symlinkat (target, dir_fd, linkpath) == 0);
>> + add_temp_file (xasprintf ("%s/%s", temp_dir, linkpath));
>> +}
>> +
>> +static void
>> +do_prepare (int argc, char *argv[])
>> +{
>> + /*
>> + Construct a test directory with the following structure:
>> +
>> + temp_dir/
>> + |- tst-openat2.xxxxxxx
>> + |- test_dir_link -> test_dir (/tmp)
>> + |- test_dir_link_2 -> test_dir_link
>> + |- temp_dir_link -> temp_dir/tst-openat2.xxxxxxx
>> + |- some-file.xxxxxxx
>> + |- invalid_link -> temp_dir/tst-openat2.xxxxxxx/some-file.xxxxxxx
>> + |- valid_link -> some-file.xxxxxxx
>> + |- subdir.xxxxxxx
>> + |- some-file.xxxxxxx
>> + */
>> +
>> + temp_dir = support_create_temp_directory ("tst-openat2.");
>> + dir_fd = xopen (temp_dir, O_RDONLY | O_DIRECTORY, 0);
>> +
>> + create_symlink (test_dir, TEST_DIR_LINK);
>> + create_symlink (TEST_DIR_LINK, TEST_DIR_LINK_2);
>> + create_symlink (temp_dir, TEMP_DIR_LINK);
>> +
>> + {
>> + char *filename;
>> + int fd = create_temp_file_in_dir ("some-file.", temp_dir, &filename);
>> + TEST_VERIFY_EXIT (fd != -1);
>> +
>> + create_symlink (filename, INVALID_LINK);
>> +
>> + create_symlink (basename (filename), VALID_LINK);
>> + }
>> +
>> + temp_subdir = support_create_temp_directory (xasprintf ("%s/subdir.",
>> + basename (temp_dir)));
>> + {
>> + int fd = create_temp_file_in_dir ("some-file.", temp_subdir,
>> + &temp_some_file);
>> + TEST_VERIFY_EXIT (fd != -1);
>> + }
>> +}
>> +#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 (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
>> + {
>> + const char *path;
>> + 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++)
>> + {
>> + const char *path;
>> + if (t->how.flags & O_CREAT)
>> + {
>> + char *newfile;
>> + int temp_fd = create_temp_file ("tst-openat2.", &newfile);
>> + TEST_VERIFY_EXIT (temp_fd != -1);
>> + xunlink (newfile);
>> + path = newfile;
>> + }
>> + else
>> + path = ".";
>> +
>> + 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 void
>> +do_test_resolve (void)
>> +{
>> + int fd;
>> +
>> + /* TEMP_DIR_LINK links to the absolute temp_dir, which escapes the temporary
>> + test directory. */
>> + fd = openat2 (dir_fd,
>> + TEST_DIR_LINK,
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_BENEATH,
>> + },
>> + sizeof (struct open_how));
>> + TEST_COMPARE (fd, -1);
>> + TEST_COMPARE (errno, EXDEV);
>
> OK.
>
>> +
>> + /* Same as before, TEMP_DIR_LINK_2 links to TEMP_DIR_LINK. */
>> + fd = openat2 (dir_fd,
>> + TEST_DIR_LINK_2,
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_BENEATH,
>> + },
>> + sizeof (struct open_how));
>> + TEST_COMPARE (fd, -1);
>> + TEST_COMPARE (errno, EXDEV);
>> +
>> + /* TEMP_DIR_LINK links to the temproary directory itself (dir_fd). */
>> + fd = openat2 (dir_fd,
>> + TEMP_DIR_LINK,
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_BENEATH,
>> + },
>> + sizeof (struct open_how));
>> + TEST_COMPARE (fd, -1);
>> + TEST_COMPARE (errno, EXDEV);
>> +
>> + /* Although it points to a valid file in same path, the link refers to
>> + an absolute path. */
>> + fd = openat2 (dir_fd,
>> + INVALID_LINK,
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_BENEATH,
>> + },
>> + sizeof (struct open_how));
>> + TEST_COMPARE (fd, -1);
>> + TEST_COMPARE (errno, EXDEV);
>> +
>> + fd = openat2 (dir_fd,
>> + VALID_LINK,
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_BENEATH,
>> + },
>> + sizeof (struct open_how));
>> + TEST_VERIFY (fd != -1);
>> + xclose (fd);
>> +
>> + /* There is no such file in temp_dir/tst-openat2.xxxxxxx. */
>> + fd = openat2 (dir_fd,
>> + "should-not-work",
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_IN_ROOT,
>> + },
>> + sizeof (struct open_how));
>> + TEST_COMPARE (fd, -1);
>> + TEST_COMPARE (errno, ENOENT);
>> +
>> + {
>> + int subdir_fd = openat2 (dir_fd,
>> + basename (temp_subdir),
>> + &(struct open_how)
>> + {
>> + .flags = O_RDONLY | O_DIRECTORY,
>> + .resolve = RESOLVE_IN_ROOT,
>> + },
>> + sizeof (struct open_how));
>> + TEST_VERIFY (subdir_fd != -1);
>> +
>> + /* Open the file within the subdir.xxxxxx with both tst-openat2.xxxxxxx
>> + and tst-openat2.xxxxxxx/subdir.xxxxxxx file descriptors. */
>> + fd = openat2 (subdir_fd,
>> + basename (temp_some_file),
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_IN_ROOT,
>> + },
>> + sizeof (struct open_how));
>> + TEST_VERIFY (fd != -1);
>> + xclose (fd);
>> +
>> + fd = openat2 (dir_fd,
>> + xasprintf ("%s/%s",
>> + basename (temp_subdir),
>> + basename (temp_some_file)),
>> + &(struct open_how)
>> + {
>> + .resolve = RESOLVE_IN_ROOT,
>> + },
>> + sizeof (struct open_how));
>> + TEST_VERIFY (fd != -1);
>> + xclose (fd);
>> + }
>> +}
>> +
>> +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)
>> +{
>> + if (openat2 (AT_FDCWD, ".", &(struct open_how) {}, sizeof (struct open_how))
>> + == -1 && errno == ENOSYS)
>> + FAIL_UNSUPPORTED ("openat2 is not supported by the kernel");
>
> OK. Unsupported.
>
>> +
>> + do_test_struct ();
>> + do_test_flags ();
>> + do_test_resolve ();
>> + 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 e46f66efdf7..a02b101d236 100644
>> --- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
>> @@ -2766,6 +2766,7 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>> GLIBC_2.5 __readlinkat_chk F
>> GLIBC_2.5 inet6_opt_append F
>> diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
>> index a6edf8778ab..a3f69cc005f 100644
>> --- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
>> +++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
>> @@ -2785,4 +2785,5 @@ GLIBC_2.42 ullabs F
>> GLIBC_2.43 __memset_explicit_chk F
>> GLIBC_2.43 memalignment F
>> GLIBC_2.43 memset_explicit F
>> +GLIBC_2.43 openat2 F
>> GLIBC_2.43 umaxabs F
>
>
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