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 updater their copy in the vdso.
Signed-off-by: Tony Breeds <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: John Stultz <[email protected]>
---
Only compile tested for IA64
Testcase at: http://bakeyournoodle.com/~tony/settimeofday-0.0/
I guess this is aimed at 2.6.24
arch/ia64/kernel/time.c | 5 +++++
arch/x86_64/kernel/vsyscall.c | 11 ++++++++++-
include/linux/clocksource.h | 5 +++++
kernel/time.c | 2 ++
4 files changed, 22 insertions(+), 1 deletions(-)
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 98cfc90..2bb8421 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -371,6 +371,11 @@ ia64_setup_printk_clock(void)
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)
{
unsigned long flags;
diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
index 06c3494..4ff78b0 100644
--- a/arch/x86_64/kernel/vsyscall.c
+++ b/arch/x86_64/kernel/vsyscall.c
@@ -66,6 +66,16 @@ struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data =
.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)
{
unsigned long flags;
@@ -79,7 +89,6 @@ void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
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;
- vsyscall_gtod_data.sys_tz = sys_tz;
vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic;
write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 16ea337..107787a 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -221,10 +221,15 @@ extern void clocksource_resume(void);
#ifdef CONFIG_GENERIC_TIME_VSYSCALL
extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
+extern void update_vsyscall_tz(void);
#else
static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
{
}
+
+static inline void update_vsyscall_tz(void)
+{
+}
#endif
#endif /* _LINUX_CLOCKSOURCE_H */
diff --git a/kernel/time.c b/kernel/time.c
index 2289a8d..9a4873e 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -30,6 +30,7 @@
#include <linux/module.h>
#include <linux/timex.h>
#include <linux/capability.h>
+#include <linux/clocksource.h>
#include <linux/errno.h>
#include <linux/syscalls.h>
#include <linux/security.h>
@@ -163,6 +164,7 @@ int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
if (tz) {
/* SMP safe, global irq locking makes it work. */
sys_tz = *tz;
+ update_vsyscall_tz();
if (firsttime) {
firsttime = 0;
if (!tv)
--
1.5.2.5
Yours Tony
linux.conf.au http://linux.conf.au/ || http://lca2008.linux.org.au/
Jan 28 - Feb 02 2008 The Australian Linux Technical Conference!
On Fri, 2007-08-31 at 13:41 +1000, Tony Breeds wrote:
> 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 updater their copy in the vdso.
Ah. Yea, so after a sys_tz update, until the next timer tick, its
possible to get the stale value. Good catch.
One little comment below.
> Signed-off-by: Tony Breeds <[email protected]>
> Cc: Andi Kleen <[email protected]>
> Cc: Tony Luck <[email protected]>
> Cc: John Stultz <[email protected]>
> ---
>
> Only compile tested for IA64
> Testcase at: http://bakeyournoodle.com/~tony/settimeofday-0.0/
> I guess this is aimed at 2.6.24
>
> arch/ia64/kernel/time.c | 5 +++++
> arch/x86_64/kernel/vsyscall.c | 11 ++++++++++-
> include/linux/clocksource.h | 5 +++++
> kernel/time.c | 2 ++
> 4 files changed, 22 insertions(+), 1 deletions(-)
>
> diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
> index 98cfc90..2bb8421 100644
> --- a/arch/ia64/kernel/time.c
> +++ b/arch/ia64/kernel/time.c
> @@ -371,6 +371,11 @@ ia64_setup_printk_clock(void)
> 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)
> {
> unsigned long flags;
> diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
> index 06c3494..4ff78b0 100644
> --- a/arch/x86_64/kernel/vsyscall.c
> +++ b/arch/x86_64/kernel/vsyscall.c
> @@ -66,6 +66,16 @@ struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data =
> .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)
> {
> unsigned long flags;
> @@ -79,7 +89,6 @@ void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
> 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;
> - vsyscall_gtod_data.sys_tz = sys_tz;
> vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
> vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic;
> write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
Hmm.. I might just extend update_vsyscall() so it takes a timezone and
then it only updates bits that have non-null pointers. Then call it from
sys_settimeofday(). This cuts down the functions each arch has to
implement, and also makes sure we get the full update each tick.
Alternatively update_vsyscall_tz() could live in timekeeping.c, grab the
appropriate locks and static data and call update_vsyscall(), also
minimizing the per-arch logic.
But your way is correct, and fixes a bug, so I won't stand in the way of
it.
-john