/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/elf.h>
#include <sys/time.h>
#include <sys/vdso.h>
#include <errno.h>
#include <stdbool.h>
#include <strings.h>
#include <time.h>
#include <machine/atomic.h>
#include "libc_private.h"
static int
tc_delta(const struct vdso_timehands *th, u_int *delta)
{
int error;
u_int tc;
error = __vdso_gettc(th, &tc);
if (error == 0)
*delta = (tc - th->th_offset_count) & th->th_counter_mask;
return (error);
}
/*
* Calculate the absolute or boot-relative time from the
* machine-specific fast timecounter and the published timehands
* structure read from the shared page.
*
* The lockless reading scheme is similar to the one used to read the
* in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
* is based on the kernel implementation.
*/
static int
binuptime(struct bintime *bt, struct vdso_timekeep *tk, bool abs)
{
struct vdso_timehands *th;
uint32_t curr, gen;
uint64_t scale, x;
u_int delta, scale_bits;
int error;
do {
if (!tk->tk_enabled)
return (ENOSYS);
curr = atomic_load_acq_32(&tk->tk_current);
th = &tk->tk_th[curr];
gen = atomic_load_acq_32(&th->th_gen);
*bt = th->th_offset;
error = tc_delta(th, &delta);
if (error == EAGAIN)
continue;
if (error != 0)
return (error);
scale = th->th_scale;
#ifdef _LP64
scale_bits = flsl(scale);
#else
scale_bits = flsll(scale);
#endif
if (__predict_false(scale_bits + fls(delta) > 63)) {
x = (scale >> 32) * delta;
scale &= 0xffffffff;
bt->sec += x >> 32;
bintime_addx(bt, x << 32);
}
bintime_addx(bt, scale * delta);
if (abs)
bintime_add(bt, &th->th_boottime);
/*
* Ensure that the load of th_offset is completed
* before the load of th_gen.
*/
atomic_thread_fence_acq();
} while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
return (0);
}
static int
getnanouptime(struct bintime *bt, struct vdso_timekeep *tk)
{
struct vdso_timehands *th;
uint32_t curr, gen;
do {
if (!tk->tk_enabled)
return (ENOSYS);
curr = atomic_load_acq_32(&tk->tk_current);
th = &tk->tk_th[curr];
gen = atomic_load_acq_32(&th->th_gen);
*bt = th->th_offset;
/*
* Ensure that the load of th_offset is completed
* before the load of th_gen.
*/
atomic_thread_fence_acq();
} while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
return (0);
}
static struct vdso_timekeep *tk;
#pragma weak __vdso_gettimeofday
int
__vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
struct bintime bt;
int error;
if (tz != NULL)
return (ENOSYS);
if (tk == NULL) {
error = __vdso_gettimekeep(&tk);
if (error != 0 || tk == NULL)
return (ENOSYS);
}
if (tk->tk_ver != VDSO_TK_VER_CURR)
return (ENOSYS);
error = binuptime(&bt, tk, true);
if (error != 0)
return (error);
bintime2timeval(&bt, tv);
return (0);
}
#pragma weak __vdso_clock_gettime
int
__vdso_clock_gettime(clockid_t clock_id, struct timespec *ts)
{
struct bintime bt;
int error;
if (tk == NULL) {
error = _elf_aux_info(AT_TIMEKEEP, &tk, sizeof(tk));
if (error != 0 || tk == NULL)
return (ENOSYS);
}
if (tk->tk_ver != VDSO_TK_VER_CURR)
return (ENOSYS);
switch (clock_id) {
case CLOCK_REALTIME:
case CLOCK_REALTIME_PRECISE:
case CLOCK_REALTIME_FAST:
case CLOCK_SECOND:
error = binuptime(&bt, tk, true);
break;
case CLOCK_MONOTONIC:
case CLOCK_MONOTONIC_PRECISE:
case CLOCK_UPTIME:
case CLOCK_UPTIME_PRECISE:
error = binuptime(&bt, tk, false);
break;
case CLOCK_MONOTONIC_FAST:
case CLOCK_UPTIME_FAST:
error = getnanouptime(&bt, tk);
break;
default:
error = ENOSYS;
break;
}
if (error != 0)
return (error);
bintime2timespec(&bt, ts);
if (clock_id == CLOCK_SECOND)
ts->tv_nsec = 0;
return (0);
}
