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The previous approach defeats the vDSO optimization on older kernels because a failing clock_gettime64 system call is performed on every function call. It also results in a clobbered errno value, exposing an OpenJDK bug (JDK-8270244). This patch fixes by open-code INLINE_VSYSCALL macro and replace all INLINE_SYSCALL_CALL with INTERNAL_SYSCALL_CALLS. Now for __clock_gettime64x, the 64-bit vDSO is used and the 32-bit vDSO is tried before falling back to 64-bit syscalls. The previous code preferred 64-bit syscall for the case where the kernel provides 64-bit time_t syscalls *and* also a 32-bit vDSO (in this case the *64-bit* syscall should be preferable over the vDSO). All architectures that provides 32-bit vDSO (i386, mips, powerpc, s390) modulo sparc; but I am not sure if some kernels versions do provide only 32-bit vDSO while still providing 64-bit time_t syscall. Regardless, for such cases the 64-bit time_t syscall is used if the vDSO returns overflowed 32-bit time_t. Tested on i686-linux-gnu (with a time64 and non-time64 kernel), x86_64-linux-gnu. Built with build-many-glibcs.py. Co-authored-by: Florian Weimer <fweimer@redhat.com>
122 lines
3.3 KiB
C
122 lines
3.3 KiB
C
/* clock_gettime -- Get current time from a POSIX clockid_t. Linux version.
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Copyright (C) 2003-2021 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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int r;
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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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int (*vdso_time64) (clockid_t clock_id, struct __timespec64 *tp)
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= GLRO(dl_vdso_clock_gettime64);
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if (vdso_time64 != NULL)
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{
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r = INTERNAL_VSYSCALL_CALL (vdso_time64, 2, clock_id, tp);
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if (r == 0)
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return 0;
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r);
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}
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#endif
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#ifdef HAVE_CLOCK_GETTIME_VSYSCALL
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int (*vdso_time) (clockid_t clock_id, struct timespec *tp)
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= GLRO(dl_vdso_clock_gettime);
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if (vdso_time != NULL)
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{
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struct timespec tp32;
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r = INTERNAL_VSYSCALL_CALL (vdso_time, 2, clock_id, &tp32);
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if (r == 0 && tp32.tv_sec > 0)
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{
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*tp = valid_timespec_to_timespec64 (tp32);
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return 0;
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}
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else if (r != 0)
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r);
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/* Fallback to syscall if the 32-bit time_t vDSO returns overflows. */
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}
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#endif
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r = INTERNAL_SYSCALL_CALL (clock_gettime64, clock_id, tp);
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if (r == 0)
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return 0;
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if (r != -ENOSYS)
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r);
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#ifndef __ASSUME_TIME64_SYSCALLS
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/* Fallback code that uses 32-bit support. */
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struct timespec tp32;
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r = INTERNAL_SYSCALL_CALL (clock_gettime, clock_id, &tp32);
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if (r == 0)
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{
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*tp = valid_timespec_to_timespec64 (tp32);
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return 0;
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}
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#endif
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return INLINE_SYSCALL_ERROR_RETURN_VALUE (-r);
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}
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#if __TIMESIZE != 64
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libc_hidden_def (__clock_gettime64)
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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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