From: Lin Ming <ming.m.lin@intel.com>
Subject: timekeeping: Fix clock_gettime vsyscall time warp
Patch-mainline: 0696b711e4be45fa104c12329f617beb29c03f78
References: bnc#569238

commit 0696b711e4be45fa104c12329f617beb29c03f78
Author: Lin Ming <ming.m.lin@intel.com>
Date:   Tue Nov 17 13:49:50 2009 +0800

    timekeeping: Fix clock_gettime vsyscall time warp
    
    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@intel.com>
    Cc: "Zhang Yanmin" <yanmin_zhang@linux.intel.com>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Tony Luck <tony.luck@intel.com>
    LKML-Reference: <1258436990.17765.83.camel@minggr.sh.intel.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: Kurt Garloff <garloff@suse.de>

---
 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
@@ -828,7 +828,8 @@ 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;
 
@@ -841,7 +842,7 @@ 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);
 }
 
 /**