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glibc/sysdeps/unix/sysv/linux/openat2.c
Adhemerval Zanella 0f0a5cd338 linux: Add openat2 (BZ 31664)
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.

A fortify wrapper is added to verify the argument size if not larger
than the current support open_how struct.

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 and aarch64-linux-gnu.

[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

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2025-12-09 11:14:16 -03:00

30 lines
1.1 KiB
C

/* 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 *filename,
const struct open_how *how, size_t usize)
{
return SYSCALL_CANCEL (openat2, dfd, filename, how, usize);
}
weak_alias (__openat2, openat2)