[S390] vdso: use ntp adjusted clock multiplier

Commit "timekeeping: Fix clock_gettime vsyscall time warp" (0696b711e)
introduced the new parameter "mult" to update_vsyscall(). This parameter
contains the internal NTP adjusted clock multiplier.

The s390x vdso did not use this adjusted multiplier.  Instead, it used
the constant clock multiplier for gettimeofday() and clock_gettime()
variants.  This may result in observable time warps as explained in
commit 0696b711e.

Make the NTP adjusted clock multiplier available to the s390x vdso
implementation and use it for time calculations.

Cc: <stable@kernel.org>
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/s390/include/asm/vdso.h b/arch/s390/include/asm/vdso.h
index 4a76d9480cce..533f35751aeb 100644
--- a/arch/s390/include/asm/vdso.h
+++ b/arch/s390/include/asm/vdso.h
@@ -29,6 +29,7 @@ struct vdso_data {
         __u32 tz_minuteswest;           /* Minutes west of Greenwich    0x30 */
         __u32 tz_dsttime;               /* Type of dst correction       0x34 */
         __u32 ectg_available;
+        __u32 ntp_mult;                 /* NTP adjusted multiplier      0x3C */
 };
 
 struct vdso_per_cpu_data {