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92b963699a
This patch avoid probing the __NR_clock_getttime64 syscall each time
__clock_gettime64 is issued on a kernel without 64 bit time support.
Once ENOSYS is obtained, only 32-bit clock_gettime are used.
The following snippet:
clock_getres (CLOCK_REALTIME, &(struct timespec) { 0 });
clock_getres (CLOCK_MONOTONIC, &(struct timespec) { 0 });
clock_getres (CLOCK_BOOTTIME, &(struct timespec) { 0 });
clock_getres (20, &(struct timespec) { 0 });
On a kernel without 64 bit time support issues the syscalls:
syscall_0x196(0, 0xffb83330, [...]) = -1 ENOSYS (Function not implemented)
clock_getres(CLOCK_REALTIME, {tv_sec=0, tv_nsec=1}) = 0
clock_getres(CLOCK_MONOTONIC, {tv_sec=0, tv_nsec=1}) = 0
clock_getres(CLOCK_BOOTTIME, {tv_sec=0, tv_nsec=1}) = 0
Checked on i686-linux-gnu on 4.15 kernel.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
96 lines
3.0 KiB
C
96 lines
3.0 KiB
C
/* clock_getres -- Get the resolution of a POSIX clockid_t. Linux version.
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Copyright (C) 2003-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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#include <errno.h>
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#include <time.h>
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#include <sysdep-vdso.h>
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#include <shlib-compat.h>
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#include <kernel-features.h>
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/* Get resolution of clock. */
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int
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__clock_getres64 (clockid_t clock_id, struct __timespec64 *res)
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{
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#ifdef __ASSUME_TIME64_SYSCALLS
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/* 64 bit ABIs or Newer 32-bit ABIs that only support 64-bit time_t. */
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# ifndef __NR_clock_getres_time64
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# define __NR_clock_getres_time64 __NR_clock_getres
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# endif
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# ifdef HAVE_CLOCK_GETRES64_VSYSCALL
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return INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
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# else
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return INLINE_SYSCALL_CALL (clock_getres_time64, clock_id, res);
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# endif
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#else
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int r;
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/* Old 32-bit ABI with possible 64-bit time_t support. */
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# ifdef __NR_clock_getres_time64
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/* Avoid issue a __NR_clock_getres_time64 syscall on kernels that do not
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support 64-bit time_t. */
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static int time64_support = 1;
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if (atomic_load_relaxed (&time64_support) != 0)
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{
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# ifdef HAVE_CLOCK_GETRES64_VSYSCALL
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r = INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
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# else
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r = INLINE_SYSCALL_CALL (clock_getres_time64, clock_id, res);
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# endif
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if (r == 0 || errno != ENOSYS)
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return r;
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atomic_store_relaxed (&time64_support, 0);
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}
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# endif
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/* Fallback code that uses 32-bit support. */
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struct timespec ts32;
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# ifdef HAVE_CLOCK_GETRES_VSYSCALL
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r = INLINE_VSYSCALL (clock_getres, 2, clock_id, &ts32);
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# else
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r = INLINE_SYSCALL_CALL (clock_getres, clock_id, &ts32);
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# endif
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if (r == 0)
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*res = valid_timespec_to_timespec64 (ts32);
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return r;
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#endif
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}
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#if __TIMESIZE != 64
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int
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__clock_getres (clockid_t clock_id, struct timespec *res)
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{
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struct __timespec64 ts64;
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int retval;
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retval = __clock_getres64 (clock_id, &ts64);
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if (retval == 0 && res != NULL)
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*res = valid_timespec64_to_timespec (ts64);
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return retval;
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}
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#endif
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versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
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/* clock_getres moved to libc in version 2.17;
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old binaries may expect the symbol version it had in librt. */
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#if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
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strong_alias (__clock_getres, __clock_getres_2);
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compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2);
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#endif
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