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authorLinus Torvalds <torvalds@linux-foundation.org>2019-08-25 17:08:01 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2019-08-25 17:08:01 (GMT)
commit5a13fc3d8ba00b786056e6fd3612b5102590992f (patch)
tree8a2a1ee75d57896ce45348e3e6e75460e9190af2
parent8a04c2ee62a4020cf1b7818c300626819d62ff5e (diff)
parentb99328a60a482108f5195b4d611f90992ca016ba (diff)
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Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timekeeping fix from Thomas Gleixner: "A single fix for a regression caused by the generic VDSO implementation where a math overflow causes CLOCK_BOOTTIME to become a random number generator" * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timekeeping/vsyscall: Prevent math overflow in BOOTTIME update
-rw-r--r--include/linux/timekeeper_internal.h5
-rw-r--r--kernel/time/timekeeping.c5
-rw-r--r--kernel/time/vsyscall.c22
3 files changed, 23 insertions, 9 deletions
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 7acb953..84ff284 100644
--- 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;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index d911c84..ca69290 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -146,6 +146,11 @@ static void tk_set_wall_to_mono(struct timekeeper *tk, struct timespec64 wtm)
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);
}
/*
diff --git a/kernel/time/vsyscall.c b/kernel/time/vsyscall.c
index 8cf3596..4bc37ac 100644
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -17,7 +17,7 @@ static inline void update_vdso_data(struct vdso_data *vdata,
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(struct vdso_data *vdata,
}
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;