linux-kernel - [PATCH] sparc: Let memset return the address argument

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Message-Id: <1409324901-19291-1-git-send-email-andreas@gaisler.com>
Date:	Fri, 29 Aug 2014 17:08:21 +0200
From:	Andreas Larsson <andreas@...sler.com>
To:	davem@...emloft.net
Cc:	sparclinux@...r.kernel.org, sam@...nborg.org,
	linux-kernel@...r.kernel.org, software@...sler.com
Subject: [PATCH] sparc: Let memset return the address argument

This makes memset follow the standard (instead of returning 0 on success). This
is needed when certain versions of gcc optimizes around memset calls and assume
that the address argument is preserved in %o0.

Signed-off-by: Andreas Larsson <andreas@...sler.com>
---
 arch/sparc/lib/memset.S |   18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/lib/memset.S b/arch/sparc/lib/memset.S
index 99c017b..f75e690 100644
--- a/arch/sparc/lib/memset.S
+++ b/arch/sparc/lib/memset.S
@@ -3,8 +3,9 @@
  * Copyright (C) 1996,1997 Jakub Jelinek (jj@...site.mff.cuni.cz)
  * Copyright (C) 1996 David S. Miller (davem@...p.rutgers.edu)
  *
- * Returns 0, if ok, and number of bytes not yet set if exception
- * occurs and we were called as clear_user.
+ * Calls to memset returns initial %o0. Calls to bzero returns 0, if ok, and
+ * number of bytes not yet set if exception occurs and we were called as
+ * clear_user.
  */
 
 #include <asm/ptrace.h>
@@ -65,6 +66,8 @@ __bzero_begin:
 	.globl	__memset_start, __memset_end
 __memset_start:
 memset:
+	mov	%o0, %g1
+	mov	1, %g4
 	and	%o1, 0xff, %g3
 	sll	%g3, 8, %g2
 	or	%g3, %g2, %g3
@@ -89,6 +92,7 @@ memset:
 	 sub	%o0, %o2, %o0
 
 __bzero:
+	clr	%g4
 	mov	%g0, %g3
 1:
 	cmp	%o1, 7
@@ -151,8 +155,8 @@ __bzero:
 	bne,a	8f
 	 EX(stb	%g3, [%o0], and %o1, 1)
 8:
-	retl
-	 clr	%o0
+	b	0f
+	 nop
 7:
 	be	13b
 	 orcc	%o1, 0, %g0
@@ -164,6 +168,12 @@ __bzero:
 	bne	8b
 	 EX(stb	%g3, [%o0 - 1], add %o1, 1)
 0:
+	andcc	%g4, 1, %g0
+	be	5f
+	 nop
+	retl
+	 mov	%g1, %o0
+5:
 	retl
 	 clr	%o0
 __memset_end:
-- 
1.7.10.4

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