[PATCH urgent] ARM: fix the memset fix

[Sascha Hauer]

From: Nicolas Pitre <nicolas.pitre at linaro.org>

>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 at linaro.org>
| Tested-by: Alexander Holler <holler at ahsoftware.de>
| Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---

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