3.13.11.3 -stable review patch. If anyone has any objections, please let me
know.
------------------
From: Xiangyu Lu <luxian...@huawei.com>
commit 80bb3ef109ff40a7593d9481c17de9bbc4d7c0e2 upstream.
In big-endian systems, "%1" get the most significant part of the value, cause
the instruction to get the wrong result.
When viewing ftrace record in big-endian ARM systems, we found that
the timestamp errors:
swapper-0 [001] 1325.970000: 0:120:R ==> [001] 16:120:R events/1
events/1-16 [001] 1325.970000: 16:120:S ==> [001] 0:120:R swapper
swapper-0 [000] 1325.1000000: 0:120:R + [000] 15:120:R events/0
swapper-0 [000] 1325.1000000: 0:120:R ==> [000] 15:120:R events/0
swapper-0 [000] 1326.030000: 0:120:R + [000] 1150:120:R sshd
swapper-0 [000] 1326.030000: 0:120:R ==> [000] 1150:120:R sshd
When viewed ftrace records, it will call the do_div(n, base) function, which
achieved arch/arm/include/asm/div64.h in. When n = 10000000, base = 1000000, in
do_div(n, base) will execute "umull %Q0, %R0, %1, %Q2".
Reviewed-by: Dave Martin <dave.mar...@arm.com>
Reviewed-by: Nicolas Pitre <n...@linaro.org>
Signed-off-by: Alex Wu <wuquanm...@huawei.com>
Signed-off-by: Xiangyu Lu <luxian...@huawei.com>
Signed-off-by: Russell King <rmk+ker...@arm.linux.org.uk>
Signed-off-by: Kamal Mostafa <ka...@canonical.com>
---
arch/arm/include/asm/div64.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/div64.h b/arch/arm/include/asm/div64.h
index 191ada6..662c7bd 100644
--- a/arch/arm/include/asm/div64.h
+++ b/arch/arm/include/asm/div64.h
@@ -156,7 +156,7 @@
/* Select the best insn combination to perform the */ \
/* actual __m * __n / (__p << 64) operation. */ \
if (!__c) { \
- asm ( "umull %Q0, %R0, %1, %Q2\n\t" \
+ asm ( "umull %Q0, %R0, %Q1, %Q2\n\t" \
"mov %Q0, #0" \
: "=&r" (__res) \
: "r" (__m), "r" (__n) \
--
1.9.1
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