[PATCH v2 2/5] powerpc: Fix vDSO clock_getres()

[Christophe Leroy]

Le 16/04/2019 à 18:14, Vincenzo Frascino a écrit :
> 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>

Reviewed-by: Christophe Leroy <christophe.leroy at c-s.fr>

> ---
>   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 | 7 +++++--
>   arch/powerpc/kernel/vdso64/gettimeofday.S | 7 +++++--
>   5 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/vdso_datapage.h b/arch/powerpc/include/asm/vdso_datapage.h
> index bbc06bd72b1f..4333b9a473dc 100644
> --- a/arch/powerpc/include/asm/vdso_datapage.h
> +++ b/arch/powerpc/include/asm/vdso_datapage.h
> @@ -86,6 +86,7 @@ struct vdso_data {
>   	__s32 wtom_clock_nsec;			/* Wall to monotonic clock nsec */
>   	__s64 wtom_clock_sec;			/* Wall to monotonic clock sec */
>   	struct timespec stamp_xtime;		/* xtime as at tb_orig_stamp */
> +	__u32 hrtimer_res;			/* hrtimer resolution */
>      	__u32 syscall_map_64[SYSCALL_MAP_SIZE]; /* map of syscalls  */
>      	__u32 syscall_map_32[SYSCALL_MAP_SIZE]; /* map of syscalls */
>   };
> @@ -107,6 +108,7 @@ struct vdso_data {
>   	__s32 wtom_clock_nsec;
>   	struct timespec stamp_xtime;	/* xtime as at tb_orig_stamp */
>   	__u32 stamp_sec_fraction;	/* fractional seconds of stamp_xtime */
> +	__u32 hrtimer_res;		/* hrtimer resolution */
>      	__u32 syscall_map_32[SYSCALL_MAP_SIZE]; /* map of syscalls */
>   	__u32 dcache_block_size;	/* L1 d-cache block size     */
>   	__u32 icache_block_size;	/* L1 i-cache block size     */
> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> index 86a61e5f8285..52e4b98a8492 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -383,6 +383,7 @@ int main(void)
>   	OFFSET(WTOM_CLOCK_NSEC, vdso_data, wtom_clock_nsec);
>   	OFFSET(STAMP_XTIME, vdso_data, stamp_xtime);
>   	OFFSET(STAMP_SEC_FRAC, vdso_data, stamp_sec_fraction);
> +	OFFSET(CLOCK_REALTIME_RES, vdso_data, hrtimer_res);
>   	OFFSET(CFG_ICACHE_BLOCKSZ, vdso_data, icache_block_size);
>   	OFFSET(CFG_DCACHE_BLOCKSZ, vdso_data, dcache_block_size);
>   	OFFSET(CFG_ICACHE_LOGBLOCKSZ, vdso_data, icache_log_block_size);
> @@ -413,7 +414,6 @@ int main(void)
>   	DEFINE(CLOCK_REALTIME_COARSE, CLOCK_REALTIME_COARSE);
>   	DEFINE(CLOCK_MONOTONIC_COARSE, CLOCK_MONOTONIC_COARSE);
>   	DEFINE(NSEC_PER_SEC, NSEC_PER_SEC);
> -	DEFINE(CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC);
>   
>   #ifdef CONFIG_BUG
>   	DEFINE(BUG_ENTRY_SIZE, sizeof(struct bug_entry));
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index bc0503ef9c9c..62c04a6746d8 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -955,6 +955,7 @@ void update_vsyscall(struct timekeeper *tk)
>   	vdso_data->wtom_clock_nsec = tk->wall_to_monotonic.tv_nsec;
>   	vdso_data->stamp_xtime = xt;
>   	vdso_data->stamp_sec_fraction = frac_sec;
> +	vdso_data->hrtimer_res = hrtimer_resolution;
>   	smp_wmb();
>   	++(vdso_data->tb_update_count);
>   }
> diff --git a/arch/powerpc/kernel/vdso32/gettimeofday.S b/arch/powerpc/kernel/vdso32/gettimeofday.S
> index afd516b572f8..2b5f9e83c610 100644
> --- a/arch/powerpc/kernel/vdso32/gettimeofday.S
> +++ b/arch/powerpc/kernel/vdso32/gettimeofday.S
> @@ -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
> diff --git a/arch/powerpc/kernel/vdso64/gettimeofday.S b/arch/powerpc/kernel/vdso64/gettimeofday.S
> index 1f324c28705b..f07730f73d5e 100644
> --- a/arch/powerpc/kernel/vdso64/gettimeofday.S
> +++ b/arch/powerpc/kernel/vdso64/gettimeofday.S
> @@ -190,12 +190,15 @@ 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	V_LOCAL_FUNC(__get_datapage)
> +	lwz	r5,CLOCK_REALTIME_RES(r3)
> +	mtlr	r12
>   	li	r3,0
>   	cmpldi	cr0,r4,0
>   	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)
>   	blr
>