glibc/sysdeps/unix/sysv/linux/internal-stat.h
Adhemerval Zanella 551101e824 io: Do not implement fstat with fstatat
AT_EMPTY_PATH is a requirement to implement fstat over fstatat,
however it does not prevent the kernel to read the path argument.
It is not an issue, but on x86-64 with SMAP-capable CPUs the kernel is
forced to perform expensive user memory access.  After that regular
lookup is performed which adds even more overhead.

Instead, issue the fstat syscall directly on LFS fstat implementation
(32 bit architectures will still continue to use statx, which is
required to have 64 bit time_t support).  it should be even a
small performance gain on non x86_64, since there is no need
to handle the path argument.

Checked on x86_64-linux-gnu.
2023-09-27 09:30:24 -03:00

32 lines
1.1 KiB
C

/* Internal stat definitions.
Copyright (C) 2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <stat_t64_cp.h>
#include <kernel_stat.h>
#include <kstat_cp.h>
#if (__WORDSIZE == 32 \
&& (!defined __SYSCALL_WORDSIZE || __SYSCALL_WORDSIZE == 32)) \
|| defined STAT_HAS_TIME32 \
|| (!defined __NR_newfstatat && !defined __NR_fstatat64)
# define FSTATAT_USE_STATX 1
#else
# define FSTATAT_USE_STATX 0
#endif