[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>

7 files changed, 15 insertions, 12 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 {
diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index 08db736dded0..a09408952ed0 100644
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -61,6 +61,7 @@ int main(void)
         DEFINE(__VDSO_WTOM_NSEC, offsetof(struct vdso_data, wtom_clock_nsec));
         DEFINE(__VDSO_TIMEZONE, offsetof(struct vdso_data, tz_minuteswest));
         DEFINE(__VDSO_ECTG_OK, offsetof(struct vdso_data, ectg_available));
+        DEFINE(__VDSO_NTP_MULT, offsetof(struct vdso_data, ntp_mult));
         DEFINE(__VDSO_ECTG_BASE, offsetof(struct vdso_per_cpu_data, ectg_timer_base));
         DEFINE(__VDSO_ECTG_USER, offsetof(struct vdso_per_cpu_data, ectg_user_time));
         /* constants used by the vdso */
diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index fba6dec156bf..d906bf19c14a 100644
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -221,6 +221,7 @@ void update_vsyscall(struct timespec *wall_time, struct clocksource *clock,
         vdso_data->xtime_clock_nsec = wall_time->tv_nsec;
         vdso_data->wtom_clock_sec = wall_to_monotonic.tv_sec;
         vdso_data->wtom_clock_nsec = wall_to_monotonic.tv_nsec;
+        vdso_data->ntp_mult = mult;
         smp_wmb();
         ++vdso_data->tb_update_count;
 }
diff --git a/arch/s390/kernel/vdso32/clock_gettime.S b/arch/s390/kernel/vdso32/clock_gettime.S
index 4a98909a8310..969643954273 100644
--- a/arch/s390/kernel/vdso32/clock_gettime.S
+++ b/arch/s390/kernel/vdso32/clock_gettime.S
@@ -38,13 +38,13 @@ __kernel_clock_gettime:
         sl      %r1,__VDSO_XTIME_STAMP+4(%r5)
         brc     3,2f
         ahi     %r0,-1
-2:      mhi     %r0,1000                        /* cyc2ns(clock,cycle_delta) */
+2:      ms      %r0,__VDSO_NTP_MULT(%r5)        /* cyc2ns(clock,cycle_delta) */
         lr      %r2,%r0
-        lhi     %r0,1000
+        l       %r0,__VDSO_NTP_MULT(%r5)
         ltr     %r1,%r1
         mr      %r0,%r0
         jnm     3f
-        ahi     %r0,1000
+        a       %r0,__VDSO_NTP_MULT(%r5)
 3:      alr     %r0,%r2
         srdl    %r0,12
         al      %r0,__VDSO_XTIME_NSEC(%r5)      /*  + xtime */
@@ -86,13 +86,13 @@ __kernel_clock_gettime:
         sl      %r1,__VDSO_XTIME_STAMP+4(%r5)
         brc     3,12f
         ahi     %r0,-1
-12:     mhi     %r0,1000                        /* cyc2ns(clock,cycle_delta) */
+12:     ms      %r0,__VDSO_NTP_MULT(%r5)        /* cyc2ns(clock,cycle_delta) */
         lr      %r2,%r0
-        lhi     %r0,1000
+        l       %r0,__VDSO_NTP_MULT(%r5)
         ltr     %r1,%r1
         mr      %r0,%r0
         jnm     13f
-        ahi     %r0,1000
+        a       %r0,__VDSO_NTP_MULT(%r5)
 13:     alr     %r0,%r2
         srdl    %r0,12
         al      %r0,__VDSO_XTIME_NSEC(%r5)      /*  + xtime */
diff --git a/arch/s390/kernel/vdso32/gettimeofday.S b/arch/s390/kernel/vdso32/gettimeofday.S
index ad8acfc949fb..2d3633175e3b 100644
--- a/arch/s390/kernel/vdso32/gettimeofday.S
+++ b/arch/s390/kernel/vdso32/gettimeofday.S
@@ -35,13 +35,13 @@ __kernel_gettimeofday:
         sl      %r1,__VDSO_XTIME_STAMP+4(%r5)
         brc     3,3f
         ahi     %r0,-1
-3:      mhi     %r0,1000                        /* cyc2ns(clock,cycle_delta) */
+3:      ms      %r0,__VDSO_NTP_MULT(%r5)        /* cyc2ns(clock,cycle_delta) */
         st      %r0,24(%r15)
-        lhi     %r0,1000
+        l       %r0,__VDSO_NTP_MULT(%r5)
         ltr     %r1,%r1
         mr      %r0,%r0
         jnm     4f
-        ahi     %r0,1000
+        a       %r0,__VDSO_NTP_MULT(%r5)
 4:      al      %r0,24(%r15)
         srdl    %r0,12
         al      %r0,__VDSO_XTIME_NSEC(%r5)      /*  + xtime */
diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S
index 49106c6e6f88..f40467884a03 100644
--- a/arch/s390/kernel/vdso64/clock_gettime.S
+++ b/arch/s390/kernel/vdso64/clock_gettime.S
@@ -36,7 +36,7 @@ __kernel_clock_gettime:
         stck    48(%r15)                        /* Store TOD clock */
         lg      %r1,48(%r15)
         sg      %r1,__VDSO_XTIME_STAMP(%r5)     /* TOD - cycle_last */
-        mghi    %r1,1000
+        msgf    %r1,__VDSO_NTP_MULT(%r5)        /*  * NTP adjustment */
         srlg    %r1,%r1,12                      /* cyc2ns(clock,cycle_delta) */
         alg     %r1,__VDSO_XTIME_NSEC(%r5)      /*  + xtime */
         lg      %r0,__VDSO_XTIME_SEC(%r5)
@@ -64,7 +64,7 @@ __kernel_clock_gettime:
         stck    48(%r15)                        /* Store TOD clock */
         lg      %r1,48(%r15)
         sg      %r1,__VDSO_XTIME_STAMP(%r5)     /* TOD - cycle_last */
-        mghi    %r1,1000
+        msgf    %r1,__VDSO_NTP_MULT(%r5)        /*  * NTP adjustment */
         srlg    %r1,%r1,12                      /* cyc2ns(clock,cycle_delta) */
         alg     %r1,__VDSO_XTIME_NSEC(%r5)      /*  + xtime */
         lg      %r0,__VDSO_XTIME_SEC(%r5)
diff --git a/arch/s390/kernel/vdso64/gettimeofday.S b/arch/s390/kernel/vdso64/gettimeofday.S
index f873e75634e1..36ee674722ec 100644
--- a/arch/s390/kernel/vdso64/gettimeofday.S
+++ b/arch/s390/kernel/vdso64/gettimeofday.S
@@ -31,7 +31,7 @@ __kernel_gettimeofday:
         stck    48(%r15)                        /* Store TOD clock */
         lg      %r1,48(%r15)
         sg      %r1,__VDSO_XTIME_STAMP(%r5)     /* TOD - cycle_last */
-        mghi    %r1,1000
+        msgf    %r1,__VDSO_NTP_MULT(%r5)        /*  * NTP adjustment */
         srlg    %r1,%r1,12                      /* cyc2ns(clock,cycle_delta) */
         alg     %r1,__VDSO_XTIME_NSEC(%r5)      /*  + xtime.tv_nsec */
         lg      %r0,__VDSO_XTIME_SEC(%r5)       /* xtime.tv_sec */