From 7781a976a7b625af003cf96a042240caf42fe8a4 Mon Sep 17 00:00:00 2001
From: rmind <rmind@NetBSD.org>
Date: Wed, 2 Jul 2008 20:07:43 +0000
Subject: [PATCH] Avoid calling a syscall when argument to sbrk(2) is zero. OK
 by <ad>.

---
 lib/libc/arch/i386/sys/sbrk.S   | 10 ++++++++--
 lib/libc/arch/x86_64/sys/sbrk.S | 10 ++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/lib/libc/arch/i386/sys/sbrk.S b/lib/libc/arch/i386/sys/sbrk.S
index 36e97bfeeb8c..359e500574db 100644
--- a/lib/libc/arch/i386/sys/sbrk.S
+++ b/lib/libc/arch/i386/sys/sbrk.S
@@ -1,4 +1,4 @@
-/*	$NetBSD: sbrk.S,v 1.18 2007/03/09 14:30:56 ad Exp $	*/
+/*	$NetBSD: sbrk.S,v 1.19 2008/07/02 20:07:43 rmind Exp $	*/
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
@@ -36,7 +36,7 @@
 
 #include <machine/asm.h>
 #if defined(SYSLIBC_SCCS) && !defined(lint)
-	RCSID("$NetBSD: sbrk.S,v 1.18 2007/03/09 14:30:56 ad Exp $")
+	RCSID("$NetBSD: sbrk.S,v 1.19 2008/07/02 20:07:43 rmind Exp $")
 #endif /* SYSLIBC_SCCS and not lint */
 
 #include "SYS.h"
@@ -59,6 +59,8 @@ ENTRY(_sbrk)
 	movl	PIC_GOT(CURBRK),%edx
 	PIC_EPILOGUE
 	movl	(%edx),%eax
+	test	%ecx,%ecx
+	jz	out
 	addl	%eax,%ecx
 	movl	%ecx,4(%esp)
 	OSYSTRAP(break)	/* don't clobber %ecx */
@@ -68,6 +70,7 @@ ENTRY(_sbrk)
 	PIC_EPILOGUE
 	movl	(%edx),%eax
 	movl	%ecx,(%edx)
+out:
 	ret
 err:
 	PIC_PROLOGUE
@@ -77,11 +80,14 @@ err:
 #else
 	movl	4(%esp),%ecx
 	movl	CURBRK,%eax
+	test	%ecx,%ecx
+	jz	out
 	addl	%eax,4(%esp)
 	OSYSTRAP(break)	/* don't clobber %ecx */
 	jc	err
 	movl	CURBRK,%eax
 	addl	%ecx,CURBRK
+out:
 	ret
 err:
 	jmp	CERROR
diff --git a/lib/libc/arch/x86_64/sys/sbrk.S b/lib/libc/arch/x86_64/sys/sbrk.S
index b0952e8c73e7..65c33625b215 100644
--- a/lib/libc/arch/x86_64/sys/sbrk.S
+++ b/lib/libc/arch/x86_64/sys/sbrk.S
@@ -1,4 +1,4 @@
-/*	$NetBSD: sbrk.S,v 1.2 2003/08/07 16:42:37 agc Exp $	*/
+/*	$NetBSD: sbrk.S,v 1.3 2008/07/02 20:07:43 rmind Exp $	*/
 
 /*-
  * Copyright (c) 1990 The Regents of the University of California.
@@ -36,7 +36,7 @@
 
 #include <machine/asm.h>
 #if defined(SYSLIBC_SCCS) && !defined(lint)
-	RCSID("$NetBSD: sbrk.S,v 1.2 2003/08/07 16:42:37 agc Exp $")
+	RCSID("$NetBSD: sbrk.S,v 1.3 2008/07/02 20:07:43 rmind Exp $")
 #endif /* SYSLIBC_SCCS and not lint */
 
 #include "SYS.h"
@@ -56,24 +56,30 @@ ENTRY(_sbrk)
 #ifdef PIC
 	movq	PIC_GOT(CURBRK),%rdx
 	movq	(%rdx),%rax
+	test	%rdi,%rdi
+	jz	out
 	addq	%rax,%rdi
 	SYSTRAP(break)
 	jc	err
 	movq	PIC_GOT(CURBRK),%rdx
 	movq	(%rdx),%rax
 	movq	%rdi,(%rdx)
+out:
 	ret
 err:
 	mov	PIC_GOT(CERROR),%rdx
 	jmp	*%rdx
 #else
 	movq	CURBRK(%rip),%rax
+	test	%rdi,%rdi
+	jz	out
 	movq	%rdi,%rsi
 	addq	%rax,%rdi
 	SYSTRAP(break)
 	jc	err
 	movq	CURBRK(%rip),%rax
 	addq	%rsi,CURBRK(%rip)
+out:
 	ret
 err:
 	jmp	CERROR