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alistair23-linux/lib/vdso/gettimeofday.c
Thomas Gleixner 4c5a116ada vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter() 
MIPS already uses and S390 will need the vdso data pointer in
__arch_get_hw_counter().

This works nicely as long as the architecture does not support time
namespaces in the VDSO. With time namespaces enabled the regular
accessor to the vdso data pointer __arch_get_vdso_data() will return the
namespace specific VDSO data page for tasks which are part of a
non-root time namespace. This would cause the architectures which need
the vdso data pointer in __arch_get_hw_counter() to access the wrong
vdso data page.

Add a vdso_data pointer argument to __arch_get_hw_counter() and hand it in
from the call sites in the core code. For architectures which do not need
the data pointer in their counter accessor function the compiler will just
optimize it out.

Fix up all existing architecture implementations and make MIPS utilize the
pointer instead of invoking the accessor function.

No functional change and no change in the resulting object code (except
MIPS).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/draft-87wo2ekuzn.fsf@nanos.tec.linutronix.de
2020-08-06 10:57:30 +02:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Generic userspace implementations of gettimeofday() and similar.
*/
#include <vdso/datapage.h>
#include <vdso/helpers.h>
#ifndef vdso_calc_delta
/*
* Default implementation which works for all sane clocksources. That
* obviously excludes x86/TSC.
*/
static __always_inline
u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
{
return ((cycles - last) & mask) * mult;
}
#endif
#ifndef vdso_shift_ns
static __always_inline u64 vdso_shift_ns(u64 ns, u32 shift)
{
return ns >> shift;
}
#endif
#ifndef __arch_vdso_hres_capable
static inline bool __arch_vdso_hres_capable(void)
{
return true;
}
#endif
#ifndef vdso_clocksource_ok
static inline bool vdso_clocksource_ok(const struct vdso_data *vd)
{
return vd->clock_mode != VDSO_CLOCKMODE_NONE;
}
#endif
#ifndef vdso_cycles_ok
static inline bool vdso_cycles_ok(u64 cycles)
{
return true;
}
#endif
#ifdef CONFIG_TIME_NS
static int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
struct __kernel_timespec *ts)
{
const struct vdso_data *vd = __arch_get_timens_vdso_data();
const struct timens_offset *offs = &vdns->offset[clk];
const struct vdso_timestamp *vdso_ts;
u64 cycles, last, ns;
u32 seq;
s64 sec;
if (clk != CLOCK_MONOTONIC_RAW)
vd = &vd[CS_HRES_COARSE];
else
vd = &vd[CS_RAW];
vdso_ts = &vd->basetime[clk];
do {
seq = vdso_read_begin(vd);
if (unlikely(!vdso_clocksource_ok(vd)))
return -1;
cycles = __arch_get_hw_counter(vd->clock_mode, vd);
if (unlikely(!vdso_cycles_ok(cycles)))
return -1;
ns = vdso_ts->nsec;
last = vd->cycle_last;
ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
ns = vdso_shift_ns(ns, vd->shift);
sec = vdso_ts->sec;
} while (unlikely(vdso_read_retry(vd, seq)));
/* Add the namespace offset */
sec += offs->sec;
ns += offs->nsec;
/*
* Do this outside the loop: a race inside the loop could result
* in __iter_div_u64_rem() being extremely slow.
*/
ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
ts->tv_nsec = ns;
return 0;
}
#else
static __always_inline const struct vdso_data *__arch_get_timens_vdso_data(void)
{
return NULL;
}
static int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
struct __kernel_timespec *ts)
{
return -EINVAL;
}
#endif
static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
struct __kernel_timespec *ts)
{
const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
u64 cycles, last, sec, ns;
u32 seq;
/* Allows to compile the high resolution parts out */
if (!__arch_vdso_hres_capable())
return -1;
do {
/*
* Open coded to handle VDSO_CLOCKMODE_TIMENS. Time namespace
* enabled tasks have a special VVAR page installed which
* has vd->seq set to 1 and vd->clock_mode set to
* VDSO_CLOCKMODE_TIMENS. For non time namespace affected tasks
* this does not affect performance because if vd->seq is
* odd, i.e. a concurrent update is in progress the extra
* check for vd->clock_mode is just a few extra
* instructions while spin waiting for vd->seq to become
* even again.
*/
while (unlikely((seq = READ_ONCE(vd->seq)) & 1)) {
if (IS_ENABLED(CONFIG_TIME_NS) &&
vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
return do_hres_timens(vd, clk, ts);
cpu_relax();
}
smp_rmb();
if (unlikely(!vdso_clocksource_ok(vd)))
return -1;
cycles = __arch_get_hw_counter(vd->clock_mode, vd);
if (unlikely(!vdso_cycles_ok(cycles)))
return -1;
ns = vdso_ts->nsec;
last = vd->cycle_last;
ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
ns = vdso_shift_ns(ns, vd->shift);
sec = vdso_ts->sec;
} while (unlikely(vdso_read_retry(vd, seq)));
/*
* Do this outside the loop: a race inside the loop could result
* in __iter_div_u64_rem() being extremely slow.
*/
ts->tv_sec = sec + __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
ts->tv_nsec = ns;
return 0;
}
#ifdef CONFIG_TIME_NS
static int do_coarse_timens(const struct vdso_data *vdns, clockid_t clk,
struct __kernel_timespec *ts)
{
const struct vdso_data *vd = __arch_get_timens_vdso_data();
const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
const struct timens_offset *offs = &vdns->offset[clk];
u64 nsec;
s64 sec;
s32 seq;
do {
seq = vdso_read_begin(vd);
sec = vdso_ts->sec;
nsec = vdso_ts->nsec;
} while (unlikely(vdso_read_retry(vd, seq)));
/* Add the namespace offset */
sec += offs->sec;
nsec += offs->nsec;
/*
* Do this outside the loop: a race inside the loop could result
* in __iter_div_u64_rem() being extremely slow.
*/
ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);
ts->tv_nsec = nsec;
return 0;
}
#else
static int do_coarse_timens(const struct vdso_data *vdns, clockid_t clk,
struct __kernel_timespec *ts)
{
return -1;
}
#endif
static __always_inline int do_coarse(const struct vdso_data *vd, clockid_t clk,
struct __kernel_timespec *ts)
{
const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
u32 seq;
do {
/*
* Open coded to handle VDSO_CLOCK_TIMENS. See comment in
* do_hres().
*/
while ((seq = READ_ONCE(vd->seq)) & 1) {
if (IS_ENABLED(CONFIG_TIME_NS) &&
vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
return do_coarse_timens(vd, clk, ts);
cpu_relax();
}
smp_rmb();
ts->tv_sec = vdso_ts->sec;
ts->tv_nsec = vdso_ts->nsec;
} while (unlikely(vdso_read_retry(vd, seq)));
return 0;
}
static __always_inline int
__cvdso_clock_gettime_common(const struct vdso_data *vd, clockid_t clock,
struct __kernel_timespec *ts)
{
u32 msk;
/* Check for negative values or invalid clocks */
if (unlikely((u32) clock >= MAX_CLOCKS))
return -1;
/*
* Convert the clockid to a bitmask and use it to check which
* clocks are handled in the VDSO directly.
*/
msk = 1U << clock;
if (likely(msk & VDSO_HRES))
vd = &vd[CS_HRES_COARSE];
else if (msk & VDSO_COARSE)
return do_coarse(&vd[CS_HRES_COARSE], clock, ts);
else if (msk & VDSO_RAW)
vd = &vd[CS_RAW];
else
return -1;
return do_hres(vd, clock, ts);
}
static __maybe_unused int
__cvdso_clock_gettime_data(const struct vdso_data *vd, clockid_t clock,
struct __kernel_timespec *ts)
{
int ret = __cvdso_clock_gettime_common(vd, clock, ts);
if (unlikely(ret))
return clock_gettime_fallback(clock, ts);
return 0;
}
static __maybe_unused int
__cvdso_clock_gettime(clockid_t clock, struct __kernel_timespec *ts)
{
return __cvdso_clock_gettime_data(__arch_get_vdso_data(), clock, ts);
}
#ifdef BUILD_VDSO32
static __maybe_unused int
__cvdso_clock_gettime32_data(const struct vdso_data *vd, clockid_t clock,
struct old_timespec32 *res)
{
struct __kernel_timespec ts;
int ret;
ret = __cvdso_clock_gettime_common(vd, clock, &ts);
if (unlikely(ret))
return clock_gettime32_fallback(clock, res);
/* For ret == 0 */
res->tv_sec = ts.tv_sec;
res->tv_nsec = ts.tv_nsec;
return ret;
}
static __maybe_unused int
__cvdso_clock_gettime32(clockid_t clock, struct old_timespec32 *res)
{
return __cvdso_clock_gettime32_data(__arch_get_vdso_data(), clock, res);
}
#endif /* BUILD_VDSO32 */
static __maybe_unused int
__cvdso_gettimeofday_data(const struct vdso_data *vd,
struct __kernel_old_timeval *tv, struct timezone *tz)
{
if (likely(tv != NULL)) {
struct __kernel_timespec ts;
if (do_hres(&vd[CS_HRES_COARSE], CLOCK_REALTIME, &ts))
return gettimeofday_fallback(tv, tz);
tv->tv_sec = ts.tv_sec;
tv->tv_usec = (u32)ts.tv_nsec / NSEC_PER_USEC;
}
if (unlikely(tz != NULL)) {
if (IS_ENABLED(CONFIG_TIME_NS) &&
vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
vd = __arch_get_timens_vdso_data();
tz->tz_minuteswest = vd[CS_HRES_COARSE].tz_minuteswest;
tz->tz_dsttime = vd[CS_HRES_COARSE].tz_dsttime;
}
return 0;
}
static __maybe_unused int
__cvdso_gettimeofday(struct __kernel_old_timeval *tv, struct timezone *tz)
{
return __cvdso_gettimeofday_data(__arch_get_vdso_data(), tv, tz);
}
#ifdef VDSO_HAS_TIME
static __maybe_unused __kernel_old_time_t
__cvdso_time_data(const struct vdso_data *vd, __kernel_old_time_t *time)
{
__kernel_old_time_t t;
if (IS_ENABLED(CONFIG_TIME_NS) &&
vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
vd = __arch_get_timens_vdso_data();
t = READ_ONCE(vd[CS_HRES_COARSE].basetime[CLOCK_REALTIME].sec);
if (time)
*time = t;
return t;
}
static __maybe_unused __kernel_old_time_t __cvdso_time(__kernel_old_time_t *time)
{
return __cvdso_time_data(__arch_get_vdso_data(), time);
}
#endif /* VDSO_HAS_TIME */
#ifdef VDSO_HAS_CLOCK_GETRES
static __maybe_unused
int __cvdso_clock_getres_common(const struct vdso_data *vd, clockid_t clock,
struct __kernel_timespec *res)
{
u32 msk;
u64 ns;
/* Check for negative values or invalid clocks */
if (unlikely((u32) clock >= MAX_CLOCKS))
return -1;
if (IS_ENABLED(CONFIG_TIME_NS) &&
vd->clock_mode == VDSO_CLOCKMODE_TIMENS)
vd = __arch_get_timens_vdso_data();
/*
* Convert the clockid to a bitmask and use it to check which
* clocks are handled in the VDSO directly.
*/
msk = 1U << clock;
if (msk & (VDSO_HRES | VDSO_RAW)) {
/*
* Preserves the behaviour of posix_get_hrtimer_res().
*/
ns = READ_ONCE(vd[CS_HRES_COARSE].hrtimer_res);
} else if (msk & VDSO_COARSE) {
/*
* Preserves the behaviour of posix_get_coarse_res().
*/
ns = LOW_RES_NSEC;
} else {
return -1;
}
if (likely(res)) {
res->tv_sec = 0;
res->tv_nsec = ns;
}
return 0;
}
static __maybe_unused
int __cvdso_clock_getres_data(const struct vdso_data *vd, clockid_t clock,
struct __kernel_timespec *res)
{
int ret = __cvdso_clock_getres_common(vd, clock, res);
if (unlikely(ret))
return clock_getres_fallback(clock, res);
return 0;
}
static __maybe_unused
int __cvdso_clock_getres(clockid_t clock, struct __kernel_timespec *res)
{
return __cvdso_clock_getres_data(__arch_get_vdso_data(), clock, res);
}
#ifdef BUILD_VDSO32
static __maybe_unused int
__cvdso_clock_getres_time32_data(const struct vdso_data *vd, clockid_t clock,
struct old_timespec32 *res)
{
struct __kernel_timespec ts;
int ret;
ret = __cvdso_clock_getres_common(vd, clock, &ts);
if (unlikely(ret))
return clock_getres32_fallback(clock, res);
if (likely(res)) {
res->tv_sec = ts.tv_sec;
res->tv_nsec = ts.tv_nsec;
}
return ret;
}
static __maybe_unused int
__cvdso_clock_getres_time32(clockid_t clock, struct old_timespec32 *res)
{
return __cvdso_clock_getres_time32_data(__arch_get_vdso_data(),
clock, res);
}
#endif /* BUILD_VDSO32 */
#endif /* VDSO_HAS_CLOCK_GETRES */
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