From: Xiangyu Lu <[email protected]> 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". Cc: <[email protected]> # 2.6.20+ Signed-off-by: Alex Wu <[email protected]> Signed-off-by: Xiangyu Lu <[email protected]> --- 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) \ -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
