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Date: Tue, 17 Jun 2014 09:16:53 -0700 From: Kamal Mostafa <kamal@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Alex Wu <wuquanming@...wei.com>, Xiangyu Lu <luxiangyu@...wei.com>, Russell King <rmk+kernel@....linux.org.uk>, Kamal Mostafa <kamal@...onical.com> Subject: [PATCH 3.8 035/121] ARM: 8027/1: fix do_div() bug in big-endian systems 3.8.13.24 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiangyu Lu <luxiangyu@...wei.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.Martin@....com> Reviewed-by: Nicolas Pitre <nico@...aro.org> Signed-off-by: Alex Wu <wuquanming@...wei.com> Signed-off-by: Xiangyu Lu <luxiangyu@...wei.com> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk> Signed-off-by: Kamal Mostafa <kamal@...onical.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 fe92ccf..a66061a 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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