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177a3d48a1
This patch provides new __clock_getres64 explicit 64 bit function for
getting the resolution (precision) of specified clock ID. Moreover, a
32 bit version - __clock_getres has been refactored to internally use
__clock_getres64.
The __clock_getres is now supposed to be used on systems still supporting
32 bit time (__TIMESIZE != 64) - hence the necessary conversion from 64 bit
struct __timespec64 to struct timespec.
The new clock_getres_time64 syscall available from Linux 5.1+ has been used,
when applicable.
On systems which are not supporting clock_getres_time64 (as their
clock_getres supports 64 bit time ABI) the vDSO syscall is attempted.
On the contrary the non-vDSO syscall is used for clock_getres_time64 as
up till now the kernel is not providing such interface.
No additional checks (i.e. if tv_nsec value overflow) are performed on
values returned via clock_getres{_time64} syscall, as it is assumed that
the Linux kernel will either return 0 and provide correct value or error.
The check for tv_sec being out of range on systems still supporting 32 bit
time (__TIMESIZE != 64) without Y2038 time support is also omitted as it is
_very_ unlikely that we would have a timer with resolution which exceeds 32
bit time_t range.
Build tests:
- The code has been tested on x86_64/x86 (native compilation):
make PARALLELMFLAGS="-j8" && make xcheck PARALLELMFLAGS="-j8"
- The glibc has been build tested (make PARALLELMFLAGS="-j8") for
x86 (i386), x86_64-x32, and armv7
Run-time tests:
- Run specific tests on ARM/x86 32bit systems (qemu):
https://github.com/lmajewski/meta-y2038 and run tests:
https://github.com/lmajewski/y2038-tests/commits/master
- Use of cross-test-ssh.sh for ARM (armv7):
make PARALLELMFLAGS="-j8" test-wrapper='./cross-test-ssh.sh root@192.168.7.2' xcheck
Linux kernel, headers and minimal kernel version for glibc build test
matrix:
- Linux v5.1 (with clock_getres_time64) and glibc build with v5.1 as
minimal kernel version (--enable-kernel="5.1.0")
The __ASSUME_TIME64_SYSCALLS flag defined.
- Linux v5.1 and default minimal kernel version
The __ASSUME_TIME64_SYSCALLS not defined, but kernel supports
clock_getres_time64 syscall.
- Linux v4.19 (no clock_getres_time64 support) with default minimal kernel
version for contemporary glibc
This kernel doesn't support clock_getres_time64 syscall, so the fallback
to clock_getres is tested.
The above tests were performed with Y2038 redirection applied as well as
without (so the __TIMESIZE != 64 execution path is checked as well).
No regressions were observed.
77 lines
2.3 KiB
C
77 lines
2.3 KiB
C
/* clock_getres -- Get the resolution of a POSIX clockid_t. Linux version.
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Copyright (C) 2003-2019 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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#ifdef HAVE_CLOCK_GETRES_VSYSCALL
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# define HAVE_VSYSCALL
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#endif
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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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# ifndef __NR_clock_getres_time64
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return INLINE_VSYSCALL (clock_getres, 2, clock_id, res);
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# else
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return INLINE_SYSCALL (clock_getres_time64, 2, clock_id, res);
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# endif
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#else
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# ifdef __NR_clock_getres_time64
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int ret = INLINE_SYSCALL (clock_getres_time64, 2, clock_id, res);
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if (ret == 0 || errno != ENOSYS)
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return ret;
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# endif
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struct timespec ts32;
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int retval = INLINE_VSYSCALL (clock_getres, 2, clock_id, &ts32);
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if (! retval && res)
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*res = valid_timespec_to_timespec64 (ts32);
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return retval;
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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 && res)
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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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