[PATCH for 2.6.23] [1/3] x86_64: Add missing mask operation to vdso

[Andi Kleen]

vdso vgetns() didn't mask the time source offset calculation, which could
lead to time problems with 32bit HPET. Add the masking.

Thanks to Chuck Ebbert for tracking down.

Cc: cebbert@xxxxxxxxxx

Signed-off-by: Andi Kleen <ak@xxxxxxx>

Index: linux/arch/x86_64/vdso/vclock_gettime.c
===================================================================
--- linux.orig/arch/x86_64/vdso/vclock_gettime.c
+++ linux/arch/x86_64/vdso/vclock_gettime.c
@@ -34,10 +34,11 @@ static long vdso_fallback_gettime(long c
 
 static inline long vgetns(void)
 {
+	long v;
 	cycles_t (*vread)(void);
 	vread = gtod->clock.vread;
-	return ((vread() - gtod->clock.cycle_last) * gtod->clock.mult) >>
-		gtod->clock.shift;
+	v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
+	return (v * gtod->clock.mult) >> gtod->clock.shift;
 }
 
 static noinline int do_realtime(struct timespec *ts)
-
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