linux-kernel - [PATCH] i386: make kernel_execve() suitable for stack unwinding

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Message-Id: <4C7FBC660200007800013F95@vpn.id2.novell.com>
Date:	Thu, 02 Sep 2010 14:01:58 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<arnd@...db.de>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] i386: make kernel_execve() suitable for stack
	 unwinding

The explicit saving and restoring of %ebx was confusing stack unwind
data consumers, and it is plain unnecessary to do this within the
asm(), since that was only introduced for PIC user mode consumers of
the original _syscall3() macro this was derived from.

Signed-off-by: Jan Beulich <jbeulich@...ell.com>
Cc: Arnd Bergmann <arnd@...db.de>

---
 arch/x86/kernel/sys_i386_32.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- linux-2.6.36-rc3/arch/x86/kernel/sys_i386_32.c
+++ 2.6.36-rc3-i386-unwind-annotations/arch/x86/kernel/sys_i386_32.c
@@ -33,8 +33,8 @@ int kernel_execve(const char *filename,
 		  const char *const envp[])
 {
 	long __res;
-	asm volatile ("push %%ebx ; movl %2,%%ebx ; int $0x80 ; pop %%ebx"
+	asm volatile ("int $0x80"
 	: "=a" (__res)
-	: "0" (__NR_execve), "ri" (filename), "c" (argv), "d" (envp) : "memory");
+	: "0" (__NR_execve), "b" (filename), "c" (argv), "d" (envp) : "memory");
 	return __res;
 }



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