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authorNathan Lynch <nathan_lynch@mentor.com>2015-08-10 17:36:06 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2015-08-11 13:42:44 +0100
commit09edea4f8fdeb4e292b80d493296070f5ec64e6e (patch)
tree4215bd594495bc36545a4e092474977ebc44a1e8
parente83dd3770021910293edea6fb2dc2fa306b1bf34 (diff)
ARM: 8410/1: VDSO: fix coarse clock monotonicity regression
Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the real timekeeper last") it has become possible on ARM to: - Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp via syscall. - Subsequently obtain a timestamp for the same clock ID via VDSO which predates the first timestamp (by one jiffy). This is because ARM's update_vsyscall is deriving the coarse time using the __current_kernel_time interface, when it should really be using the timekeeper object provided to it by the timekeeping core. It happened to work before only because __current_kernel_time would access the same timekeeper object which had been passed to update_vsyscall. This is no longer the case. Cc: stable@vger.kernel.org Fixes: 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the real timekeeper last") Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
-rw-r--r--arch/arm/kernel/vdso.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index efe17dd9b921..54a5aeab988d 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -296,7 +296,6 @@ static bool tk_is_cntvct(const struct timekeeper *tk)
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
struct timespec64 *wtm = &tk->wall_to_monotonic;
if (!cntvct_ok) {
@@ -308,10 +307,10 @@ void update_vsyscall(struct timekeeper *tk)
vdso_write_begin(vdso_data);
- xtime_coarse = __current_kernel_time();
vdso_data->tk_is_cntvct = tk_is_cntvct(tk);
- vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec;
- vdso_data->xtime_coarse_nsec = xtime_coarse.tv_nsec;
+ vdso_data->xtime_coarse_sec = tk->xtime_sec;
+ vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >>
+ tk->tkr_mono.shift);
vdso_data->wtm_clock_sec = wtm->tv_sec;
vdso_data->wtm_clock_nsec = wtm->tv_nsec;