2 * SPDX-License-Identifier: BSD-2-Clause
4 * Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 #include <sys/cdefs.h>
36 #include <machine/atomic.h>
37 #include "libc_private.h"
40 tc_delta(const struct vdso_timehands *th, u_int *delta)
45 error = __vdso_gettc(th, &tc);
47 *delta = (tc - th->th_offset_count) & th->th_counter_mask;
52 * Calculate the absolute or boot-relative time from the
53 * machine-specific fast timecounter and the published timehands
54 * structure read from the shared page.
56 * The lockless reading scheme is similar to the one used to read the
57 * in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
58 * is based on the kernel implementation.
61 binuptime(struct bintime *bt, struct vdso_timekeep *tk, bool abs)
63 struct vdso_timehands *th;
66 u_int delta, scale_bits;
73 curr = atomic_load_acq_32(&tk->tk_current);
74 th = &tk->tk_th[curr];
75 gen = atomic_load_acq_32(&th->th_gen);
77 error = tc_delta(th, &delta);
84 scale_bits = flsl(scale);
86 scale_bits = flsll(scale);
88 if (__predict_false(scale_bits + fls(delta) > 63)) {
89 x = (scale >> 32) * delta;
92 bintime_addx(bt, x << 32);
94 bintime_addx(bt, scale * delta);
96 bintime_add(bt, &th->th_boottime);
99 * Ensure that the load of th_offset is completed
100 * before the load of th_gen.
102 atomic_thread_fence_acq();
103 } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
108 getnanouptime(struct bintime *bt, struct vdso_timekeep *tk)
110 struct vdso_timehands *th;
117 curr = atomic_load_acq_32(&tk->tk_current);
118 th = &tk->tk_th[curr];
119 gen = atomic_load_acq_32(&th->th_gen);
123 * Ensure that the load of th_offset is completed
124 * before the load of th_gen.
126 atomic_thread_fence_acq();
127 } while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
131 static struct vdso_timekeep *tk;
133 #pragma weak __vdso_gettimeofday
135 __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
143 error = __vdso_gettimekeep(&tk);
144 if (error != 0 || tk == NULL)
147 if (tk->tk_ver != VDSO_TK_VER_CURR)
149 error = binuptime(&bt, tk, true);
152 bintime2timeval(&bt, tv);
156 #pragma weak __vdso_clock_gettime
158 __vdso_clock_gettime(clockid_t clock_id, struct timespec *ts)
164 error = _elf_aux_info(AT_TIMEKEEP, &tk, sizeof(tk));
165 if (error != 0 || tk == NULL)
168 if (tk->tk_ver != VDSO_TK_VER_CURR)
172 case CLOCK_REALTIME_PRECISE:
173 case CLOCK_REALTIME_FAST:
175 error = binuptime(&bt, tk, true);
177 case CLOCK_MONOTONIC:
178 case CLOCK_MONOTONIC_PRECISE:
180 case CLOCK_UPTIME_PRECISE:
181 error = binuptime(&bt, tk, false);
183 case CLOCK_MONOTONIC_FAST:
184 case CLOCK_UPTIME_FAST:
185 error = getnanouptime(&bt, tk);
193 bintime2timespec(&bt, ts);
194 if (clock_id == CLOCK_SECOND)