2006-10-18 02:39:53

by Jeremy Fitzhardinge

Subject: [PATCH 2.6.19-rc2-mm1] Fix fake return address

The fake return address was being set to __KERNEL_PDA, rather than 0.
Push it earlier while %eax still equals 0.

Signed-off-by: Jeremy Fitzhardinge <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrew Morton <[email protected]>

diff -r b8e58159855c arch/i386/kernel/head.S
--- a/arch/i386/kernel/head.S Tue Oct 17 19:04:59 2006 -0700
+++ b/arch/i386/kernel/head.S Tue Oct 17 19:05:46 2006 -0700
@@ -316,12 +316,12 @@ 1: movl $(__KERNEL_DS),%eax # reload all
xorl %eax,%eax # Clear FS and LDT
movl %eax,%fs
lldt %ax
+ pushl %eax # fake return address

movl $(__KERNEL_PDA),%eax
mov %eax,%gs

cld # gcc2 wants the direction flag cleared at all times
- pushl %eax # fake return address
#ifdef CONFIG_SMP
movb ready, %cl
movb $1, ready

2006-10-18 11:15:48

by Andi Kleen

Subject: Re: [PATCH 2.6.19-rc2-mm1] Fix fake return address

On Tue, Oct 17, 2006 at 07:21:38PM -0700, Jeremy Fitzhardinge wrote:
> The fake return address was being set to __KERNEL_PDA, rather than 0.
> Push it earlier while %eax still equals 0.

Oops. That might explain some of the unwind problems. Thanks.

-Andi

>
> Signed-off-by: Jeremy Fitzhardinge <[email protected]>
> Cc: Andi Kleen <[email protected]>
> Cc: Andrew Morton <[email protected]>
>
> diff -r b8e58159855c arch/i386/kernel/head.S
> --- a/arch/i386/kernel/head.S Tue Oct 17 19:04:59 2006 -0700
> +++ b/arch/i386/kernel/head.S Tue Oct 17 19:05:46 2006 -0700
> @@ -316,12 +316,12 @@ 1: movl $(__KERNEL_DS),%eax # reload all
> xorl %eax,%eax # Clear FS and LDT
> movl %eax,%fs
> lldt %ax
> + pushl %eax # fake return address
>
> movl $(__KERNEL_PDA),%eax
> mov %eax,%gs
>
> cld # gcc2 wants the direction flag cleared at
> all times
> - pushl %eax # fake return address
> #ifdef CONFIG_SMP
> movb ready, %cl
> movb $1, ready
>
>
>