1/* clock_getres -- Get the resolution of a POSIX clockid_t. Linux version.
2 Copyright (C) 2003-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20#include <errno.h>
21#include <time.h>
22
23#include <sysdep-vdso.h>
24#include <shlib-compat.h>
25#include <kernel-features.h>
26
27/* Get resolution of clock. */
28int
29__clock_getres64 (clockid_t clock_id, struct __timespec64 *res)
30{
31#ifdef __ASSUME_TIME64_SYSCALLS
32 /* 64 bit ABIs or Newer 32-bit ABIs that only support 64-bit time_t. */
33# ifndef __NR_clock_getres_time64
34# define __NR_clock_getres_time64 __NR_clock_getres
35# endif
36# ifdef HAVE_CLOCK_GETRES64_VSYSCALL
37 return INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
38# else
39 return INLINE_SYSCALL_CALL (clock_getres_time64, clock_id, res);
40# endif
41#else
42 int r;
43 /* Old 32-bit ABI with possible 64-bit time_t support. */
44# ifdef __NR_clock_getres_time64
45 /* Avoid issue a __NR_clock_getres_time64 syscall on kernels that do not
46 support 64-bit time_t. */
47 static int time64_support = 1;
48 if (atomic_load_relaxed (&time64_support) != 0)
49 {
50# ifdef HAVE_CLOCK_GETRES64_VSYSCALL
51 r = INLINE_VSYSCALL (clock_getres_time64, 2, clock_id, res);
52# else
53 r = INLINE_SYSCALL_CALL (clock_getres_time64, clock_id, res);
54# endif
55 if (r == 0 || errno != ENOSYS)
56 return r;
57
58 atomic_store_relaxed (&time64_support, 0);
59 }
60# endif
61 /* Fallback code that uses 32-bit support. */
62 struct timespec ts32;
63# ifdef HAVE_CLOCK_GETRES_VSYSCALL
64 r = INLINE_VSYSCALL (clock_getres, 2, clock_id, &ts32);
65# else
66 r = INLINE_SYSCALL_CALL (clock_getres, clock_id, &ts32);
67# endif
68 if (r == 0)
69 *res = valid_timespec_to_timespec64 (ts32);
70 return r;
71#endif
72}
73
74#if __TIMESIZE != 64
75libc_hidden_def (__clock_getres64)
76
77int
78__clock_getres (clockid_t clock_id, struct timespec *res)
79{
80 struct __timespec64 ts64;
81 int retval;
82
83 retval = __clock_getres64 (clock_id, &ts64);
84 if (retval == 0 && res != NULL)
85 *res = valid_timespec64_to_timespec (ts64);
86
87 return retval;
88}
89#endif
90
91versioned_symbol (libc, __clock_getres, clock_getres, GLIBC_2_17);
92/* clock_getres moved to libc in version 2.17;
93 old binaries may expect the symbol version it had in librt. */
94#if SHLIB_COMPAT (libc, GLIBC_2_2, GLIBC_2_17)
95strong_alias (__clock_getres, __clock_getres_2);
96compat_symbol (libc, __clock_getres_2, clock_getres, GLIBC_2_2);
97#endif
98