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| author | Xiangyu Lu <luxiangyu@huawei.com> | 2014-04-15 09:38:17 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-05-06 07:55:27 -0700 |
| commit | 4a91c29ca2e7ae1fa4020e334abfc2174d8c6bdf (patch) | |
| tree | a6f81ca041a866f79a1c8d5fe0a9760f84b1087c | |
| parent | ec474f3aef984135bbc568ddc903083a5170e308 (diff) | |
ARM: 8027/1: fix do_div() bug in big-endian systems
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.Martin@arm.com>
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Alex Wu <wuquanming@huawei.com>
Signed-off-by: Xiangyu Lu <luxiangyu@huawei.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/arm/include/asm/div64.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm/include/asm/div64.h b/arch/arm/include/asm/div64.h index fe92ccf1d0b0..a66061aef29c 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) \ |