[PATCH 2/5] powerpc: Fix vDSO clock_getres()

[Christophe Leroy]

On 04/01/2019 11:51 AM, Vincenzo Frascino wrote:
> 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 powerpc vdso implementation of clock_getres keeping a copy of
> hrtimer_resolution in vdso data and using that directly.
> 
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino at arm.com>
> ---
>   arch/powerpc/include/asm/vdso_datapage.h  |  2 ++
>   arch/powerpc/kernel/asm-offsets.c         |  2 +-
>   arch/powerpc/kernel/time.c                |  1 +
>   arch/powerpc/kernel/vdso32/gettimeofday.S | 22 +++++++++++++++-------
>   arch/powerpc/kernel/vdso64/gettimeofday.S | 22 +++++++++++++++-------
>   5 files changed, 34 insertions(+), 15 deletions(-)
> 

[...]

> diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
> index 1e0bc5955a40..b21630079496 100644
> --- a/arch/powerpc/kernel/vdso32/gettimeofday.S
> +++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
> @@ -160,14 +160,21 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
>   	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq
>   	bne	cr0,99f
>   
> -	li	r3,0
> -	cmpli	cr0,r4,0
> +	mflr	r12
> +  .cfi_register lr,r12
> +	mr	r11,r4
> +	bl	__get_datapage at local
> +	lwz	r5,CLOCK_REALTIME_RES(r3)
> +	li	r4,0
> +	cmplwi	r11,0		/* check if res is NULL */
> +	beq	1f
> +
> +	stw	r4,TSPC32_TV_SEC(r11)
> +	stw	r5,TSPC32_TV_NSEC(r11)
> +
> +1:	mtlr	r12
>   	crclr	cr0*4+so
> -	beqlr
> -	lis	r5,CLOCK_REALTIME_RES at h
> -	ori	r5,r5,CLOCK_REALTIME_RES at l
> -	stw	r3,TSPC32_TV_SEC(r4)
> -	stw	r5,TSPC32_TV_NSEC(r4)
> +	li	r3,0
>   	blr

The above can be done simpler, see below

@@ -160,12 +160,15 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
  	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq
  	bne	cr0,99f

+	mflr	r12
+  .cfi_register lr,r12
+	bl	__get_datapage at local
+	lwz	r5,CLOCK_REALTIME_RES(r3)
+	mtlr	r12
  	li	r3,0
  	cmpli	cr0,r4,0
  	crclr	cr0*4+so
  	beqlr
-	lis	r5,CLOCK_REALTIME_RES at h
-	ori	r5,r5,CLOCK_REALTIME_RES at l
  	stw	r3,TSPC32_TV_SEC(r4)
  	stw	r5,TSPC32_TV_NSEC(r4)
  	blr

Christophe

>   
>   	/*
> @@ -175,6 +182,7 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
>   	 */
>   99:
>   	li	r0,__NR_clock_getres
> +  .cfi_restore lr
>   	sc
>   	blr
>     .cfi_endproc
> diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S b/arch/powerpc/kernel/vdso64/gettimeofday.S
> index a4ed9edfd5f0..a7e49bddd475 100644
> --- a/arch/powerpc/kernel/vdso64/gettimeofday.S
> +++ b/arch/powerpc/kernel/vdso64/gettimeofday.S
> @@ -190,14 +190,21 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
>   	cror	cr0*4+eq,cr0*4+eq,cr1*4+eq
>   	bne	cr0,99f
>   
> -	li	r3,0
> -	cmpldi	cr0,r4,0
> +	mflr	r12
> +  .cfi_register lr,r12
> +	mr	r11, r4
> +	bl	V_LOCAL_FUNC(__get_datapage)
> +	lwz	r5,CLOCK_REALTIME_RES(r3)
> +	li	r4,0
> +	cmpldi	r11,0		/* check if res is NULL */
> +	beq	1f
> +
> +	std	r4,TSPC64_TV_SEC(r11)
> +	std	r5,TSPC64_TV_NSEC(r11)
> +
> +1:	mtlr	r12
>   	crclr	cr0*4+so
> -	beqlr
> -	lis	r5,CLOCK_REALTIME_RES at h
> -	ori	r5,r5,CLOCK_REALTIME_RES at l
> -	std	r3,TSPC64_TV_SEC(r4)
> -	std	r5,TSPC64_TV_NSEC(r4)
> +	li	r3,0
>   	blr

The same type of simplification applies here too.

Christophe


>   
>   	/*
> @@ -205,6 +212,7 @@ V_FUNCTION_BEGIN(__kernel_clock_getres)
>   	 */
>   99:
>   	li	r0,__NR_clock_getres
> +  .cfi_restore lr
>   	sc
>   	blr
>     .cfi_endproc
>