Commit 478237a5 authored by Vincenzo Frascino's avatar Vincenzo Frascino Committed by Vasily Gorbik
Browse files

s390/vdso: fix vDSO clock_getres() 

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: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
[heiko.carstens@de.ibm.com: use llgf for proper zero extension]
Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 2b2a2584

arch/s390/include/asm/vdso.h

+1 −0
Original line number Diff line number Diff line
@@ -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 {

arch/s390/kernel/asm-offsets.c

+1 −1
Original line number Diff line number Diff line
@@ -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_GETCPU_VAL, vdso_per_cpu_data, getcpu_val);
@@ -86,7 +87,6 @@ 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 */

arch/s390/kernel/time.c

+1 −0
Original line number Diff line number Diff line
@@ -301,6 +301,7 @@ 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;

}

arch/s390/kernel/vdso64/clock_getres.S

+5 −5
Original line number Diff line number Diff line
@@ -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

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