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Fix discrepancy between VDSO based gettimeofday() and sys_gettimeofday().

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On platforms that copy sys_tz into the vdso (currently only x86_64, soon to
include powerpc), it is possible for the vdso to get out of sync if a user
calls (admittedly unusual) settimeofday(NULL, ptr).

This patch adds a hook for architectures that set
CONFIG_GENERIC_TIME_VSYSCALL to ensure when sys_tz is updated they can also
updatee their copy in the vdso.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Acked-by: John Stultz <johnstul@us.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tony Breeds 2007-10-18 03:04:57 -07:00 • committed by Linus Torvalds
parent 6212e3a388
commit 2c62214831
4 changed files with 22 additions and 1 deletions
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5
arch/ia64/kernel/time.c
View file

@ -371,6 +371,11 @@ ia64_setup_printk_clock(void)
ia64_printk_clock = ia64_itc_printk_clock; ia64_printk_clock = ia64_itc_printk_clock;
} }
/* IA64 doesn't cache the timezone */
void update_vsyscall_tz(void)
{
}
void update_vsyscall(struct timespec *wall, struct clocksource *c) void update_vsyscall(struct timespec *wall, struct clocksource *c)
{ {
unsigned long flags; unsigned long flags;

11
arch/x86/kernel/vsyscall_64.c
View file

@ -64,6 +64,16 @@ struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data =
.sysctl_enabled = 1, .sysctl_enabled = 1,
}; };
void update_vsyscall_tz(void)
{
unsigned long flags;
write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
/* sys_tz has changed */
vsyscall_gtod_data.sys_tz = sys_tz;
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)
{ {
unsigned long flags; unsigned long flags;
@ -77,7 +87,6 @@ void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
vsyscall_gtod_data.clock.shift = clock->shift; vsyscall_gtod_data.clock.shift = clock->shift;
vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec; vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec; vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
vsyscall_gtod_data.sys_tz = sys_tz;
vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic; vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic;
write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags); write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
} }

5
include/linux/clocksource.h
View file

@ -221,10 +221,15 @@ extern void clocksource_resume(void);
#ifdef CONFIG_GENERIC_TIME_VSYSCALL #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);
extern void update_vsyscall_tz(void);
#else #else
static inline void update_vsyscall(struct timespec *ts, struct clocksource *c) static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
{ {
} }
static inline void update_vsyscall_tz(void)
{
}
#endif #endif
#endif /* _LINUX_CLOCKSOURCE_H */ #endif /* _LINUX_CLOCKSOURCE_H */

2
kernel/time.c
View file

@ -30,6 +30,7 @@
#include <linux/module.h> #include <linux/module.h>
#include <linux/timex.h> #include <linux/timex.h>
#include <linux/capability.h> #include <linux/capability.h>
#include <linux/clocksource.h>
#include <linux/errno.h> #include <linux/errno.h>
#include <linux/syscalls.h> #include <linux/syscalls.h>
#include <linux/security.h> #include <linux/security.h>
@ -158,6 +159,7 @@ int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
if (tz) { if (tz) {
/* SMP safe, global irq locking makes it work. */ /* SMP safe, global irq locking makes it work. */
sys_tz = *tz; sys_tz = *tz;
update_vsyscall_tz();
if (firsttime) { if (firsttime) {
firsttime = 0; firsttime = 0;
if (!tv) if (!tv)