[084/111] timekeeping: Fix clock_gettime vsyscall time warp

[Greg KH]

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Lin Ming <ming.m.lin@xxxxxxxxx>

commit 0696b711e4be45fa104c12329f617beb29c03f78 upstream.

Since commit 0a544198 "timekeeping: Move NTP adjusted clock multiplier
to struct timekeeper" the clock multiplier of vsyscall is updated with
the unmodified clock multiplier of the clock source and not with the
NTP adjusted multiplier of the timekeeper.

This causes user space observerable time warps:
new CLOCK-warp maximum: 120 nsecs,  00000025c337c537 -> 00000025c337c4bf

Add a new argument "mult" to update_vsyscall() and hand in the
timekeeping internal NTP adjusted multiplier.

Signed-off-by: Lin Ming <ming.m.lin@xxxxxxxxx>
Cc: "Zhang Yanmin" <yanmin_zhang@xxxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
LKML-Reference: <1258436990.17765.83.camel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Kurt Garloff <garloff@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/ia64/kernel/time.c       |    4 ++--
 arch/powerpc/kernel/time.c    |    5 +++--
 arch/s390/kernel/time.c       |    3 ++-
 arch/x86/kernel/vsyscall_64.c |    5 +++--
 include/linux/clocksource.h   |    6 ++++--
 kernel/time/timekeeping.c     |    6 +++---
 6 files changed, 17 insertions(+), 12 deletions(-)

--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -473,7 +473,7 @@ void update_vsyscall_tz(void)
 {
 }
 
-void update_vsyscall(struct timespec *wall, struct clocksource *c)
+void update_vsyscall(struct timespec *wall, struct clocksource *c, u32 mult)
 {
         unsigned long flags;
 
@@ -481,7 +481,7 @@ void update_vsyscall(struct timespec *wa
 
         /* copy fsyscall clock data */
         fsyscall_gtod_data.clk_mask = c->mask;
-        fsyscall_gtod_data.clk_mult = c->mult;
+        fsyscall_gtod_data.clk_mult = mult;
         fsyscall_gtod_data.clk_shift = c->shift;
         fsyscall_gtod_data.clk_fsys_mmio = c->fsys_mmio;
         fsyscall_gtod_data.clk_cycle_last = c->cycle_last;
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -864,7 +864,8 @@ static cycle_t timebase_read(struct cloc
 	return (cycle_t)get_tb();
 }
 
-void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
+void update_vsyscall(struct timespec *wall_time, struct clocksource *clock,
+		     u32 mult)
 {
 	u64 t2x, stamp_xsec;
 
@@ -877,7 +878,7 @@ void update_vsyscall(struct timespec *wa
 
 	/* XXX this assumes clock->shift == 22 */
 	/* 4611686018 ~= 2^(20+64-22) / 1e9 */
-	t2x = (u64) clock->mult * 4611686018ULL;
+	t2x = (u64) mult * 4611686018ULL;
 	stamp_xsec = (u64) xtime.tv_nsec * XSEC_PER_SEC;
 	do_div(stamp_xsec, 1000000000);
 	stamp_xsec += (u64) xtime.tv_sec * XSEC_PER_SEC;
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -214,7 +214,8 @@ struct clocksource * __init clocksource_
 	return &clocksource_tod;
 }
 
-void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
+void update_vsyscall(struct timespec *wall_time, struct clocksource *clock,
+		     u32 mult)
 {
 	if (clock != &clocksource_tod)
 		return;
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -73,7 +73,8 @@ void update_vsyscall_tz(void)
 	write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
 }
 
-void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
+void update_vsyscall(struct timespec *wall_time, struct clocksource *clock,
+		     u32 mult)
 {
 	unsigned long flags;
 
@@ -82,7 +83,7 @@ void update_vsyscall(struct timespec *wa
 	vsyscall_gtod_data.clock.vread = clock->vread;
 	vsyscall_gtod_data.clock.cycle_last = clock->cycle_last;
 	vsyscall_gtod_data.clock.mask = clock->mask;
-	vsyscall_gtod_data.clock.mult = clock->mult;
+	vsyscall_gtod_data.clock.mult = mult;
 	vsyscall_gtod_data.clock.shift = clock->shift;
 	vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
 	vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -282,10 +282,12 @@ extern struct clocksource * __init __wea
 extern void clocksource_mark_unstable(struct clocksource *cs);
 
 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
-extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
+extern void
+update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult);
 extern void update_vsyscall_tz(void);
 #else
-static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
+static inline void
+update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult)
 {
 }
 
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -177,7 +177,7 @@ void timekeeping_leap_insert(int leapsec
 {
 	xtime.tv_sec += leapsecond;
 	wall_to_monotonic.tv_sec -= leapsecond;
-	update_vsyscall(&xtime, timekeeper.clock);
+	update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
 }
 
 #ifdef CONFIG_GENERIC_TIME
@@ -337,7 +337,7 @@ int do_settimeofday(struct timespec *tv)
 	timekeeper.ntp_error = 0;
 	ntp_clear();
 
-	update_vsyscall(&xtime, timekeeper.clock);
+	update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
 
 	write_sequnlock_irqrestore(&xtime_lock, flags);
 
@@ -822,7 +822,7 @@ void update_wall_time(void)
 	update_xtime_cache(nsecs);
 
 	/* check to see if there is a new clocksource to use */
-	update_vsyscall(&xtime, timekeeper.clock);
+	update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
 }
 
 /**


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