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

Christophe Leroy <christophe.leroy@xxxxxx> · Tue, 23 Apr 2019 18:33:12 +0200

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@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>

Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxx>

---
  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@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@h
-	ori	r5,r5,CLOCK_REALTIME_RES@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@h
-	ori	r5,r5,CLOCK_REALTIME_RES@l
  	std	r3,TSPC64_TV_SEC(r4)
  	std	r5,TSPC64_TV_NSEC(r4)
  	blr







