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vgettimeofday.c
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vgettimeofday.c
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/*
* Userspace implementations of gettimeofday() and friends.
*
* Copyright (C) 2017 Cavium, Inc.
* Copyright (C) 2015 Mentor Graphics Corporation
* Copyright (C) 2012 ARM Limited
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Author: Will Deacon <[email protected]>
* Rewriten from arch64 version into C by: Andrew Pinski <[email protected]>
* Reworked and rebased over arm version by: Mark Salyzyn <[email protected]>
*/
#include <asm/barrier.h>
#include <linux/compiler.h> /* for notrace */
#include <linux/math64.h> /* for __iter_div_u64_rem() */
#include <uapi/linux/time.h> /* for struct timespec */
#include "compiler.h"
#include "datapage.h"
#ifdef ARCH_PROVIDES_TIMER
DEFINE_FALLBACK(gettimeofday, struct timeval *, tv, struct timezone *, tz)
#endif
DEFINE_FALLBACK(clock_gettime, clockid_t, clock, struct timespec *, ts)
DEFINE_FALLBACK(clock_getres, clockid_t, clock, struct timespec *, ts)
static notrace u32 vdso_read_begin(const struct vdso_data *vd)
{
u32 seq;
do {
seq = READ_ONCE(vd->tb_seq_count);
if ((seq & 1) == 0)
break;
cpu_relax();
} while (true);
smp_rmb(); /* Pairs with second smp_wmb in update_vsyscall */
return seq;
}
static notrace int vdso_read_retry(const struct vdso_data *vd, u32 start)
{
u32 seq;
smp_rmb(); /* Pairs with first smp_wmb in update_vsyscall */
seq = READ_ONCE(vd->tb_seq_count);
return seq != start;
}
static notrace int do_realtime_coarse(const struct vdso_data *vd,
struct timespec *ts)
{
u32 seq;
do {
seq = vdso_read_begin(vd);
ts->tv_sec = vd->xtime_coarse_sec;
ts->tv_nsec = vd->xtime_coarse_nsec;
} while (vdso_read_retry(vd, seq));
return 0;
}
static notrace int do_monotonic_coarse(const struct vdso_data *vd,
struct timespec *ts)
{
struct timespec tomono;
u32 seq;
u64 nsec;
do {
seq = vdso_read_begin(vd);
ts->tv_sec = vd->xtime_coarse_sec;
ts->tv_nsec = vd->xtime_coarse_nsec;
tomono.tv_sec = vd->wtm_clock_sec;
tomono.tv_nsec = vd->wtm_clock_nsec;
} while (vdso_read_retry(vd, seq));
ts->tv_sec += tomono.tv_sec;
/* open coding timespec_add_ns */
ts->tv_sec += __iter_div_u64_rem(ts->tv_nsec + tomono.tv_nsec,
NSEC_PER_SEC, &nsec);
ts->tv_nsec = nsec;
return 0;
}
#ifdef ARCH_PROVIDES_TIMER
/*
* Returns the clock delta, in nanoseconds left-shifted by the clock
* shift.
*/
static notrace u64 get_clock_shifted_nsec(const u64 cycle_last,
const u32 mult,
const u64 mask)
{
u64 res;
/* Read the virtual counter. */
res = arch_vdso_read_counter();
res = res - cycle_last;
res &= mask;
return res * mult;
}
static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
{
u32 seq, mult, shift;
u64 nsec, cycle_last;
#ifdef ARCH_CLOCK_FIXED_MASK
static const u64 mask = ARCH_CLOCK_FIXED_MASK;
#else
u64 mask;
#endif
vdso_xtime_clock_sec_t sec;
do {
seq = vdso_read_begin(vd);
if (vd->use_syscall)
return -1;
cycle_last = vd->cs_cycle_last;
mult = vd->cs_mono_mult;
shift = vd->cs_shift;
#ifndef ARCH_CLOCK_FIXED_MASK
mask = vd->cs_mask;
#endif
sec = vd->xtime_clock_sec;
nsec = vd->xtime_clock_snsec;
} while (unlikely(vdso_read_retry(vd, seq)));
nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
nsec >>= shift;
/* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
ts->tv_nsec = nsec;
return 0;
}
static notrace int do_monotonic(const struct vdso_data *vd, struct timespec *ts)
{
u32 seq, mult, shift;
u64 nsec, cycle_last;
#ifdef ARCH_CLOCK_FIXED_MASK
static const u64 mask = ARCH_CLOCK_FIXED_MASK;
#else
u64 mask;
#endif
vdso_wtm_clock_nsec_t wtm_nsec;
__kernel_time_t sec;
do {
seq = vdso_read_begin(vd);
if (vd->use_syscall)
return -1;
cycle_last = vd->cs_cycle_last;
mult = vd->cs_mono_mult;
shift = vd->cs_shift;
#ifndef ARCH_CLOCK_FIXED_MASK
mask = vd->cs_mask;
#endif
sec = vd->xtime_clock_sec;
nsec = vd->xtime_clock_snsec;
sec += vd->wtm_clock_sec;
wtm_nsec = vd->wtm_clock_nsec;
} while (unlikely(vdso_read_retry(vd, seq)));
nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
nsec >>= shift;
nsec += wtm_nsec;
/* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
ts->tv_nsec = nsec;
return 0;
}
static notrace int do_monotonic_raw(const struct vdso_data *vd,
struct timespec *ts)
{
u32 seq, mult, shift;
u64 nsec, cycle_last;
#ifdef ARCH_CLOCK_FIXED_MASK
static const u64 mask = ARCH_CLOCK_FIXED_MASK;
#else
u64 mask;
#endif
vdso_raw_time_sec_t sec;
do {
seq = vdso_read_begin(vd);
if (vd->use_syscall)
return -1;
cycle_last = vd->cs_cycle_last;
mult = vd->cs_raw_mult;
shift = vd->cs_shift;
#ifndef ARCH_CLOCK_FIXED_MASK
mask = vd->cs_mask;
#endif
sec = vd->raw_time_sec;
nsec = vd->raw_time_nsec;
} while (unlikely(vdso_read_retry(vd, seq)));
nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
nsec >>= shift;
/* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
ts->tv_nsec = nsec;
return 0;
}
static notrace int do_boottime(const struct vdso_data *vd, struct timespec *ts)
{
u32 seq, mult, shift;
u64 nsec, cycle_last;
vdso_wtm_clock_nsec_t wtm_nsec;
#ifdef ARCH_CLOCK_FIXED_MASK
static const u64 mask = ARCH_CLOCK_FIXED_MASK;
#else
u64 mask;
#endif
__kernel_time_t sec;
do {
seq = vdso_read_begin(vd);
if (vd->use_syscall)
return -1;
cycle_last = vd->cs_cycle_last;
mult = vd->cs_mono_mult;
shift = vd->cs_shift;
#ifndef ARCH_CLOCK_FIXED_MASK
mask = vd->cs_mask;
#endif
sec = vd->xtime_clock_sec;
nsec = vd->xtime_clock_snsec;
sec += vd->wtm_clock_sec + vd->btm_sec;
wtm_nsec = vd->wtm_clock_nsec + vd->btm_nsec;
} while (unlikely(vdso_read_retry(vd, seq)));
nsec += get_clock_shifted_nsec(cycle_last, mult, mask);
nsec >>= shift;
nsec += wtm_nsec;
/* open coding timespec_add_ns to save a ts->tv_nsec = 0 */
ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
ts->tv_nsec = nsec;
return 0;
}
#endif /* ARCH_PROVIDES_TIMER */
notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
{
const struct vdso_data *vd = __get_datapage();
switch (clock) {
case CLOCK_REALTIME_COARSE:
do_realtime_coarse(vd, ts);
break;
case CLOCK_MONOTONIC_COARSE:
do_monotonic_coarse(vd, ts);
break;
#ifdef ARCH_PROVIDES_TIMER
case CLOCK_REALTIME:
if (do_realtime(vd, ts))
goto fallback;
break;
case CLOCK_MONOTONIC:
if (do_monotonic(vd, ts))
goto fallback;
break;
case CLOCK_MONOTONIC_RAW:
if (do_monotonic_raw(vd, ts))
goto fallback;
break;
case CLOCK_BOOTTIME:
if (do_boottime(vd, ts))
goto fallback;
break;
#endif
default:
goto fallback;
}
return 0;
fallback:
return clock_gettime_fallback(clock, ts);
}
#ifdef ARCH_PROVIDES_TIMER
notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
{
const struct vdso_data *vd = __get_datapage();
if (likely(tv != NULL)) {
struct timespec ts;
if (do_realtime(vd, &ts))
return gettimeofday_fallback(tv, tz);
tv->tv_sec = ts.tv_sec;
tv->tv_usec = ts.tv_nsec / 1000;
}
if (unlikely(tz != NULL)) {
tz->tz_minuteswest = vd->tz_minuteswest;
tz->tz_dsttime = vd->tz_dsttime;
}
return 0;
}
#endif
int __vdso_clock_getres(clockid_t clock, struct timespec *res)
{
long nsec;
switch (clock) {
case CLOCK_REALTIME_COARSE:
case CLOCK_MONOTONIC_COARSE:
nsec = LOW_RES_NSEC;
break;
#ifdef ARCH_PROVIDES_TIMER
case CLOCK_REALTIME:
case CLOCK_MONOTONIC:
case CLOCK_MONOTONIC_RAW:
case CLOCK_BOOTTIME:
nsec = MONOTONIC_RES_NSEC;
break;
#endif
default:
return clock_getres_fallback(clock, res);
}
if (likely(res != NULL)) {
res->tv_sec = 0;
res->tv_nsec = nsec;
}
return 0;
}
notrace time_t __vdso_time(time_t *t)
{
const struct vdso_data *vd = __get_datapage();
time_t result = READ_ONCE(vd->xtime_coarse_sec);
if (t)
*t = result;
return result;
}