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a9091a1244
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_gettime (CLOCK_REALTIME, &(struct timespec) { 0 });
clock_gettime (CLOCK_MONOTONIC, &(struct timespec) { 0 });
clock_gettime (CLOCK_BOOTTIME, &(struct timespec) { 0 });
clock_gettime (20, &(struct timespec) { 0 });
On a kernel without 64 bit time support and with vDSO support results
on the following syscalls:
syscall_0x193(0, 0xff87ba30, [...]) = -1 ENOSYS (Function not implemented)
clock_gettime(CLOCK_BOOTTIME, {tv_sec=927082, tv_nsec=474382032}) = 0
clock_gettime(0x14 /* CLOCK_??? */, 0xff87b9f8) = -1 EINVAL (Invalid argument)
While on a kernel without vDSO support:
syscall_0x193(0, 0xbec95550, 0xb6ed2000, 0x1, 0xbec95550, 0) = -1 (errno 38)
clock_gettime(CLOCK_REALTIME, {tv_sec=1576615930, tv_nsec=638250162}) = 0
clock_gettime(CLOCK_MONOTONIC, {tv_sec=1665478, tv_nsec=638779620}) = 0
clock_gettime(CLOCK_BOOTTIME, {tv_sec=1675418, tv_nsec=292932704}) = 0
clock_gettime(0x14 /* CLOCK_??? */, 0xbec95530) = -1 EINVAL (Invalid argument)
Checked on i686-linux-gnu on 4.15 kernel and on a 5.3 kernel.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
107 lines
3.2 KiB
C
107 lines
3.2 KiB
C
/* clock_gettime -- Get current time from 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 <kernel-features.h>
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#include <errno.h>
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#include <time.h>
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#include "kernel-posix-cpu-timers.h"
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#include <sysdep-vdso.h>
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#include <shlib-compat.h>
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/* Get current value of CLOCK and store it in TP. */
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int
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__clock_gettime64 (clockid_t clock_id, struct __timespec64 *tp)
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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_gettime64
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# define __NR_clock_gettime64 __NR_clock_gettime
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# endif
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# ifdef HAVE_CLOCK_GETTIME64_VSYSCALL
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return INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp);
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# else
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return INLINE_SYSCALL_CALL (clock_gettime64, clock_id, tp);
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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_gettime64
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/* Avoid issue a __NR_clock_gettime64 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_GETTIME64_VSYSCALL
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r = INLINE_VSYSCALL (clock_gettime64, 2, clock_id, tp);
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# else
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r = INLINE_SYSCALL_CALL (clock_gettime64, clock_id, tp);
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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 tp32;
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# ifdef HAVE_CLOCK_GETTIME_VSYSCALL
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r = INLINE_VSYSCALL (clock_gettime, 2, clock_id, &tp32);
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# else
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r = INLINE_SYSCALL_CALL (clock_gettime, clock_id, &tp32);
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# endif
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if (r == 0)
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*tp = valid_timespec_to_timespec64 (tp32);
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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_gettime (clockid_t clock_id, struct timespec *tp)
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{
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int ret;
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struct __timespec64 tp64;
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ret = __clock_gettime64 (clock_id, &tp64);
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if (ret == 0)
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{
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if (! in_time_t_range (tp64.tv_sec))
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{
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__set_errno (EOVERFLOW);
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return -1;
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}
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*tp = valid_timespec64_to_timespec (tp64);
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}
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return ret;
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}
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#endif
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libc_hidden_def (__clock_gettime)
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versioned_symbol (libc, __clock_gettime, clock_gettime, GLIBC_2_17);
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/* clock_gettime 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_gettime, __clock_gettime_2);
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compat_symbol (libc, __clock_gettime_2, clock_gettime, GLIBC_2_2);
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#endif
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