Hi Nico,
ignore this one, you were not meant to be on Cc.
Sascha
On Thu, May 23, 2013 at 08:31:15AM +0200, Sascha Hauer wrote:
> From: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>
>
> From Kernel commit 418df63a ARM: 7670/1: fix the memset fix
>
> | Commit 455bd4c430b0 ("ARM: 7668/1: fix memset-related crashes caused by
> | recent GCC (4.7.2) optimizations") attempted to fix a compliance issue
> | with the memset return value. However the memset itself became broken
> | by that patch for misaligned pointers.
> |
> | This fixes the above by branching over the entry code from the
> | misaligned fixup code to avoid reloading the original pointer.
> |
> | Also, because the function entry alignment is wrong in the Thumb mode
> | compilation, that fixup code is moved to the end.
> |
> | While at it, the entry instructions are slightly reworked to help dual
> | issue pipelines.
> |
> | Signed-off-by: Nicolas Pitre <nico@xxxxxxxxxx>
> | Tested-by: Alexander Holler <holler@xxxxxxxxxxxxx>
> | Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
>
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> ---
>
> This was reported one of our customers. One effect was that the
> md5sum implementation produced wrong results.
>
> arch/arm/lib/memset.S | 33 +++++++++++++--------------------
> 1 file changed, 13 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm/lib/memset.S b/arch/arm/lib/memset.S
> index 5e35d7f..c4d2672 100644
> --- a/arch/arm/lib/memset.S
> +++ b/arch/arm/lib/memset.S
> @@ -14,31 +14,15 @@
>
> .text
> .align 5
> - .word 0
> -
> -1: subs r2, r2, #4 @ 1 do we have enough
> - blt 5f @ 1 bytes to align with?
> - cmp r3, #2 @ 1
> - strltb r1, [ip], #1 @ 1
> - strleb r1, [ip], #1 @ 1
> - strb r1, [ip], #1 @ 1
> - add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3))
> -/*
> - * The pointer is now aligned and the length is adjusted. Try doing the
> - * memset again.
> - */
>
> ENTRY(memset)
> -/*
> - * Preserve the contents of r0 for the return value.
> - */
> - mov ip, r0
> - ands r3, ip, #3 @ 1 unaligned?
> - bne 1b @ 1
> + ands r3, r0, #3 @ 1 unaligned?
> + mov ip, r0 @ preserve r0 as return value
> + bne 6f @ 1
> /*
> * we know that the pointer in ip is aligned to a word boundary.
> */
> - orr r1, r1, r1, lsl #8
> +1: orr r1, r1, r1, lsl #8
> orr r1, r1, r1, lsl #16
> mov r3, r1
> cmp r2, #16
> @@ -127,5 +111,14 @@ ENTRY(memset)
> tst r2, #1
> strneb r1, [ip], #1
> mov pc, lr
> +
> +6: subs r2, r2, #4 @ 1 do we have enough
> + blt 5b @ 1 bytes to align with?
> + cmp r3, #2 @ 1
> + strltb r1, [ip], #1 @ 1
> + strleb r1, [ip], #1 @ 1
> + strb r1, [ip], #1 @ 1
> + add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3))
> + b 1b
> ENDPROC(memset)
>
> --
> 1.8.2.rc2
>
>
--
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