[PATCH] powerpc: Fix program check handling when lockdep is enabled

[Benjamin Herrenschmidt]

On Tue, 2012-02-21 at 18:32 +1100, Michael Ellerman wrote:
> In commit 54321242afe ("Disable interrupts early in Program Check"), we
> switched from enabling to disabling interrupts in program_check_common.
> 
> Whereas ENABLE_INTS leaves r3 untouched, if lockdep is enabled DISABLE_INTS
> calls into lockdep code and will clobber r3. That means we pass a bogus
> struct pt_regs* into program_check_exception() and all hell breaks loose.
> 
> So load our regs pointer into r3 after we call DISABLE_INTS.

Ah nice catch, thanks !

Cheers,
Ben.

> Signed-off-by: Michael Ellerman <michael at ellerman.id.au>
> ---
>  arch/powerpc/kernel/exceptions-64s.S |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index 3844ca7..15c5a4f 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -774,8 +774,8 @@ alignment_common:
>  program_check_common:
>  	EXCEPTION_PROLOG_COMMON(0x700, PACA_EXGEN)
>  	bl	.save_nvgprs
> -	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	DISABLE_INTS
> +	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	.program_check_exception
>  	b	.ret_from_except
>