linux-stable/kernel/time/vsyscall.c

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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2019 ARM Ltd.
*
* Generic implementation of update_vsyscall and update_vsyscall_tz.
*
* Based on the x86 specific implementation.
*/
#include <linux/hrtimer.h>
#include <linux/timekeeper_internal.h>
#include <vdso/datapage.h>
#include <vdso/helpers.h>
#include <vdso/vsyscall.h>
#include "timekeeping_internal.h"
static inline void update_vdso_data(struct vdso_data *vdata,
struct timekeeper *tk)
{
struct vdso_timestamp *vdso_ts;
u64 nsec, sec;
vdata[CS_HRES_COARSE].cycle_last = tk->tkr_mono.cycle_last;
vdata[CS_HRES_COARSE].mask = tk->tkr_mono.mask;
vdata[CS_HRES_COARSE].mult = tk->tkr_mono.mult;
vdata[CS_HRES_COARSE].shift = tk->tkr_mono.shift;
vdata[CS_RAW].cycle_last = tk->tkr_raw.cycle_last;
vdata[CS_RAW].mask = tk->tkr_raw.mask;
vdata[CS_RAW].mult = tk->tkr_raw.mult;
vdata[CS_RAW].shift = tk->tkr_raw.shift;
/* CLOCK_MONOTONIC */
vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];
vdso_ts->sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
nsec = tk->tkr_mono.xtime_nsec;
nsec += ((u64)tk->wall_to_monotonic.tv_nsec << tk->tkr_mono.shift);
while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
vdso_ts->sec++;
}
vdso_ts->nsec = nsec;
/* Copy MONOTONIC time for BOOTTIME */
sec = vdso_ts->sec;
/* Add the boot offset */
sec += tk->monotonic_to_boot.tv_sec;
nsec += (u64)tk->monotonic_to_boot.tv_nsec << tk->tkr_mono.shift;
/* CLOCK_BOOTTIME */
vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_BOOTTIME];
vdso_ts->sec = sec;
while (nsec >= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift)) {
nsec -= (((u64)NSEC_PER_SEC) << tk->tkr_mono.shift);
vdso_ts->sec++;
}
vdso_ts->nsec = nsec;
/* CLOCK_MONOTONIC_RAW */
vdso_ts = &vdata[CS_RAW].basetime[CLOCK_MONOTONIC_RAW];
vdso_ts->sec = tk->raw_sec;
vdso_ts->nsec = tk->tkr_raw.xtime_nsec;
/* CLOCK_TAI */
vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI];
vdso_ts->sec = tk->xtime_sec + (s64)tk->tai_offset;
vdso_ts->nsec = tk->tkr_mono.xtime_nsec;
}
void update_vsyscall(struct timekeeper *tk)
{
struct vdso_data *vdata = __arch_get_k_vdso_data();
struct vdso_timestamp *vdso_ts;
s32 clock_mode;
u64 nsec;
/* copy vsyscall data */
vdso_write_begin(vdata);
clock_mode = tk->tkr_mono.clock->vdso_clock_mode;
vdata[CS_HRES_COARSE].clock_mode = clock_mode;
vdata[CS_RAW].clock_mode = clock_mode;
/* CLOCK_REALTIME also required for time() */
vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];
vdso_ts->sec = tk->xtime_sec;
vdso_ts->nsec = tk->tkr_mono.xtime_nsec;
/* CLOCK_REALTIME_COARSE */
vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];
vdso_ts->sec = tk->xtime_sec;
vdso_ts->nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
/* CLOCK_MONOTONIC_COARSE */
vdso_ts = &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC_COARSE];
vdso_ts->sec = tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
nsec = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
nsec = nsec + tk->wall_to_monotonic.tv_nsec;
vdso_ts->sec += __iter_div_u64_rem(nsec, NSEC_PER_SEC, &vdso_ts->nsec);
/*
* Read without the seqlock held by clock_getres().
* Note: No need to have a second copy.
*/
WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);
/*
* If the current clocksource is not VDSO capable, then spare the
* update of the high reolution parts.
*/
if (clock_mode != VDSO_CLOCKMODE_NONE)
update_vdso_data(vdata, tk);
__arch_update_vsyscall(vdata, tk);
vdso_write_end(vdata);
__arch_sync_vdso_data(vdata);
}
void update_vsyscall_tz(void)
{
struct vdso_data *vdata = __arch_get_k_vdso_data();
timekeeping/vsyscall: Update VDSO data unconditionally The update of the VDSO data is depending on __arch_use_vsyscall() returning True. This is a leftover from the attempt to map the features of various architectures 1:1 into generic code. The usage of __arch_use_vsyscall() in the actual vsyscall implementations got dropped and replaced by the requirement for the architecture code to return U64_MAX if the global clocksource is not usable in the VDSO. But the __arch_use_vsyscall() check in the update code stayed which causes the VDSO data to be stale or invalid when an architecture actually implements that function and returns False when the current clocksource is not usable in the VDSO. As a consequence the VDSO implementations of clock_getres(), time(), clock_gettime(CLOCK_.*_COARSE) operate on invalid data and return bogus information. Remove the __arch_use_vsyscall() check from the VDSO update function and update the VDSO data unconditionally. [ tglx: Massaged changelog and removed the now useless implementations in asm-generic/ARM64/MIPS ] Fixes: 44f57d788e7deecb50 ("timekeeping: Provide a generic update_vsyscall() implementation") Signed-off-by: Huacai Chen <chenhc@lemote.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Paul Burton <paul.burton@mips.com> Cc: linux-mips@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1571887709-11447-1-git-send-email-chenhc@lemote.com
2019-10-24 03:28:29 +00:00
vdata[CS_HRES_COARSE].tz_minuteswest = sys_tz.tz_minuteswest;
vdata[CS_HRES_COARSE].tz_dsttime = sys_tz.tz_dsttime;
__arch_sync_vdso_data(vdata);
}
/**
* vdso_update_begin - Start of a VDSO update section
*
* Allows architecture code to safely update the architecture specific VDSO
* data. Disables interrupts, acquires timekeeper lock to serialize against
* concurrent updates from timekeeping and invalidates the VDSO data
* sequence counter to prevent concurrent readers from accessing
* inconsistent data.
*
* Returns: Saved interrupt flags which need to be handed in to
* vdso_update_end().
*/
unsigned long vdso_update_begin(void)
{
struct vdso_data *vdata = __arch_get_k_vdso_data();
unsigned long flags;
raw_spin_lock_irqsave(&timekeeper_lock, flags);
vdso_write_begin(vdata);
return flags;
}
/**
* vdso_update_end - End of a VDSO update section
* @flags: Interrupt flags as returned from vdso_update_begin()
*
* Pairs with vdso_update_begin(). Marks vdso data consistent, invokes data
* synchronization if the architecture requires it, drops timekeeper lock
* and restores interrupt flags.
*/
void vdso_update_end(unsigned long flags)
{
struct vdso_data *vdata = __arch_get_k_vdso_data();
vdso_write_end(vdata);
__arch_sync_vdso_data(vdata);
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
}