s390/vdso: fix vDSO clock_getres()

[ Upstream commit 478237a595120a18e9b52fd2c57a6e8b7a01e411 ]

clock_getres in the vDSO library has to preserve the same behaviour
of posix_get_hrtimer_res().

In particular, posix_get_hrtimer_res() does:
    sec = 0;
    ns = hrtimer_resolution;
and hrtimer_resolution depends on the enablement of the high
resolution timers that can happen either at compile or at run time.

Fix the s390 vdso implementation of clock_getres keeping a copy of
hrtimer_resolution in vdso data and using that directly.

Link: https://lkml.kernel.org/r/20200324121027.21665-1-vincenzo.frascino@arm.com
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[heiko.carstens@de.ibm.com: use llgf for proper zero extension]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/s390/include/asm/vdso.h b/arch/s390/include/asm/vdso.h
index 169d760..f3ba84f 100644 (file)
--- a/arch/s390/include/asm/vdso.h
+++ b/arch/s390/include/asm/vdso.h
@@ -36,6 +36,7 @@ struct vdso_data {
        __u32 tk_shift;                 /* Shift used for xtime_nsec    0x60 */
        __u32 ts_dir;                   /* TOD steering direction       0x64 */
        __u64 ts_end;                   /* TOD steering end             0x68 */
+       __u32 hrtimer_res;              /* hrtimer resolution           0x70 */
 };
 
 struct vdso_per_cpu_data {

diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index b662858..a65cb49 100644 (file)
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -76,6 +76,7 @@ int main(void)
        OFFSET(__VDSO_TK_SHIFT, vdso_data, tk_shift);
        OFFSET(__VDSO_TS_DIR, vdso_data, ts_dir);
        OFFSET(__VDSO_TS_END, vdso_data, ts_end);
+       OFFSET(__VDSO_CLOCK_REALTIME_RES, vdso_data, hrtimer_res);
        OFFSET(__VDSO_ECTG_BASE, vdso_per_cpu_data, ectg_timer_base);
        OFFSET(__VDSO_ECTG_USER, vdso_per_cpu_data, ectg_user_time);
        OFFSET(__VDSO_CPU_NR, vdso_per_cpu_data, cpu_nr);
@@ -87,7 +88,6 @@ int main(void)
        DEFINE(__CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE);
        DEFINE(__CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_COARSE);
        DEFINE(__CLOCK_THREAD_CPUTIME_ID, CLOCK_THREAD_CPUTIME_ID);
-       DEFINE(__CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC);
        DEFINE(__CLOCK_COARSE_RES, LOW_RES_NSEC);
        BLANK();
        /* idle data offsets */

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index e8766be..8ea9db5 100644 (file)
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -310,6 +310,7 @@ void update_vsyscall(struct timekeeper *tk)
 
        vdso_data->tk_mult = tk->tkr_mono.mult;
        vdso_data->tk_shift = tk->tkr_mono.shift;
+       vdso_data->hrtimer_res = hrtimer_resolution;
        smp_wmb();
        ++vdso_data->tb_update_count;
 }

diff --git a/arch/s390/kernel/vdso64/clock_getres.S b/arch/s390/kernel/vdso64/clock_getres.S
index 0814353..0c79caa 100644 (file)
--- a/arch/s390/kernel/vdso64/clock_getres.S
+++ b/arch/s390/kernel/vdso64/clock_getres.S
@@ -17,12 +17,14 @@
        .type  __kernel_clock_getres,@function
 __kernel_clock_getres:
        CFI_STARTPROC
-       larl    %r1,4f
+       larl    %r1,3f
+       lg      %r0,0(%r1)
        cghi    %r2,__CLOCK_REALTIME_COARSE
        je      0f
        cghi    %r2,__CLOCK_MONOTONIC_COARSE
        je      0f
-       larl    %r1,3f
+       larl    %r1,_vdso_data
+       llgf    %r0,__VDSO_CLOCK_REALTIME_RES(%r1)
        cghi    %r2,__CLOCK_REALTIME
        je      0f
        cghi    %r2,__CLOCK_MONOTONIC
@@ -36,7 +38,6 @@ __kernel_clock_getres:
        jz      2f
 0:     ltgr    %r3,%r3
        jz      1f                              /* res == NULL */
-       lg      %r0,0(%r1)
        xc      0(8,%r3),0(%r3)                 /* set tp->tv_sec to zero */
        stg     %r0,8(%r3)                      /* store tp->tv_usec */
 1:     lghi    %r2,0
@@ -45,6 +46,5 @@ __kernel_clock_getres:
        svc     0
        br      %r14
        CFI_ENDPROC
-3:     .quad   __CLOCK_REALTIME_RES
-4:     .quad   __CLOCK_COARSE_RES
+3:     .quad   __CLOCK_COARSE_RES
        .size   __kernel_clock_getres,.-__kernel_clock_getres