[PATCH v4 2/3] s390: Fix vDSO clock_getres()

Vincenzo Frascino
2019-05-23T11:21:15Z

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.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

Note: This patch is independent from the others in this series, hence it
can be merged singularly by the s390 maintainers.

arch/s390/include/asm/vdso.h | 1 +
arch/s390/kernel/asm-offsets.c | 2 +-
arch/s390/kernel/time.c | 1 +
arch/s390/kernel/vdso32/clock_getres.S | 12 +++++++-----
arch/s390/kernel/vdso64/clock_getres.S | 10 +++++-----
5 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/arch/s390/include/asm/vdso.h b/arch/s390/include/asm/vdso.h
index 169d7604eb80..f3ba84fa9bd1 100644
--- 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 41ac4ad21311..4a229a60b24a 100644
--- 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 e8766beee5ad..8ea9db599d38 100644
--- 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/vdso32/clock_getres.S b/arch/s390/kernel/vdso32/clock_getres.S
index eaf9cf1417f6..fecd7684c645 100644
--- a/arch/s390/kernel/vdso32/clock_getres.S
+++ b/arch/s390/kernel/vdso32/clock_getres.S
@@ -18,20 +18,22 @@
__kernel_clock_getres:
CFI_STARTPROC
basr %r1,0
- la %r1,4f-.(%r1)
+10: al %r1,4f-10b(%r1)
+ l %r0,__VDSO_CLOCK_REALTIME_RES(%r1)
chi %r2,__CLOCK_REALTIME
je 0f
chi %r2,__CLOCK_MONOTONIC
je 0f
- la %r1,5f-4f(%r1)
+ basr %r1,0
+ la %r1,5f-.(%r1)
+ l %r0,0(%r1)
chi %r2,__CLOCK_REALTIME_COARSE
je 0f
chi %r2,__CLOCK_MONOTONIC_COARSE
jne 3f
0: ltr %r3,%r3
jz 2f /* res == NULL */
-1: l %r0,0(%r1)
- xc 0(4,%r3),0(%r3) /* set tp->tv_sec to zero */
+1: xc 0(4,%r3),0(%r3) /* set tp->tv_sec to zero */
st %r0,4(%r3) /* store tp->tv_usec */
2: lhi %r2,0
br %r14
@@ -39,6 +41,6 @@ __kernel_clock_getres:
svc 0
br %r14
CFI_ENDPROC
-4: .long __CLOCK_REALTIME_RES
+4: .long _vdso_data - 10b
5: .long __CLOCK_COARSE_RES
.size __kernel_clock_getres,.-__kernel_clock_getres
diff --git a/arch/s390/kernel/vdso64/clock_getres.S b/arch/s390/kernel/vdso64/clock_getres.S
index 081435398e0a..022b58c980db 100644
--- 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
+ l %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
--
2.21.0