Thanks Thomas. On 22/08/2019 12:00, Thomas Gleixner wrote: > The VDSO update for CLOCK_BOOTTIME has a overflow issue as it shifts the > nanoseconds based boot time offset left by the clocksource shift. That > overflows once the boot time offset becomes large enough. As a consequence > CLOCK_BOOTTIME in the VDSO becomes a random number causing applications to > misbehave. > > Fix it by storing a timespec64 representation of the offset when boot time > is adjusted and add that to the MONOTONIC base time value in the vdso data > page. Using the timespec64 representation avoids a 64bit division in the > update code. >
I've tested resume from both suspend and hibernate and this patch fixes the problem I reported. Tested-by: Chris Clayton <[email protected]> > Fixes: 44f57d788e7d ("timekeeping: Provide a generic update_vsyscall() > implementation") > Reported-by: Chris Clayton <[email protected]> > Signed-off-by: Thomas Gleixner <[email protected]> > --- > include/linux/timekeeper_internal.h | 5 +++++ > kernel/time/timekeeping.c | 5 +++++ > kernel/time/vsyscall.c | 22 +++++++++++++--------- > 3 files changed, 23 insertions(+), 9 deletions(-) > > --- a/include/linux/timekeeper_internal.h > +++ b/include/linux/timekeeper_internal.h > @@ -57,6 +57,7 @@ struct tk_read_base { > * @cs_was_changed_seq: The sequence number of clocksource change events > * @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second > * @raw_sec: CLOCK_MONOTONIC_RAW time in seconds > + * @monotonic_to_boot: CLOCK_MONOTONIC to CLOCK_BOOTTIME offset > * @cycle_interval: Number of clock cycles in one NTP interval > * @xtime_interval: Number of clock shifted nano seconds in one NTP > * interval. > @@ -84,6 +85,9 @@ struct tk_read_base { > * > * wall_to_monotonic is no longer the boot time, getboottime must be > * used instead. > + * > + * @monotonic_to_boottime is a timespec64 representation of @offs_boot to > + * accelerate the VDSO update for CLOCK_BOOTTIME. > */ > struct timekeeper { > struct tk_read_base tkr_mono; > @@ -99,6 +103,7 @@ struct timekeeper { > u8 cs_was_changed_seq; > ktime_t next_leap_ktime; > u64 raw_sec; > + struct timespec64 monotonic_to_boot; > > /* The following members are for timekeeping internal use */ > u64 cycle_interval; > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -146,6 +146,11 @@ static void tk_set_wall_to_mono(struct t > static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta) > { > tk->offs_boot = ktime_add(tk->offs_boot, delta); > + /* > + * Timespec representation for VDSO update to avoid 64bit division > + * on every update. > + */ > + tk->monotonic_to_boot = ktime_to_timespec64(tk->offs_boot); > } > > /* > --- a/kernel/time/vsyscall.c > +++ b/kernel/time/vsyscall.c > @@ -17,7 +17,7 @@ static inline void update_vdso_data(stru > struct timekeeper *tk) > { > struct vdso_timestamp *vdso_ts; > - u64 nsec; > + u64 nsec, sec; > > vdata[CS_HRES_COARSE].cycle_last = tk->tkr_mono.cycle_last; > vdata[CS_HRES_COARSE].mask = tk->tkr_mono.mask; > @@ -45,23 +45,27 @@ static inline void update_vdso_data(stru > } > 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; > + /* 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 = tk->xtime_sec + tk->wall_to_monotonic.tv_sec; > - nsec = tk->tkr_mono.xtime_nsec; > - nsec += ((u64)(tk->wall_to_monotonic.tv_nsec + > - ktime_to_ns(tk->offs_boot)) << tk->tkr_mono.shift); > + 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; >
