[PATCH 03/24] powerpc/6xx: Handle DABR match before calling do_page_fault

[Michael Ellerman]

Benjamin Herrenschmidt <benh at kernel.crashing.org> writes:

> On legacy 6xx 32-bit procesors, we checked for the DABR match bit
> in DSISR from do_page_fault(), in the middle of a pile of ifdef's
> because all other CPU types do it in assembly prior to calling
> do_page_fault. Fix that.
>
> Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> ---
>  arch/powerpc/kernel/entry_32.S | 11 +++++++++++
>  arch/powerpc/mm/fault.c        |  9 ---------
>  2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 8587059ad848..7331df033804 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -586,6 +586,8 @@ ppc_swapcontext:
>  handle_page_fault:
>  	stw	r4,_DAR(r1)
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
> +	andis.  r0,r5,DSISR_DABRMATCH at h
> +	bne-    handle_dabr_fault
>  	bl	do_page_fault
>  	cmpwi	r3,0
>  	beq+	ret_from_except
> @@ -599,6 +601,15 @@ handle_page_fault:
>  	bl	bad_page_fault
>  	b	ret_from_except_full
>  
> +	/* We have a data breakpoint exception - handle it */
> +handle_dabr_fault:
> +	SAVE_NVGPRS(r1)
> +	lwz	r0,_TRAP(r1)
> +	clrrwi	r0,r0,1
> +	stw	r0,_TRAP(r1)
> +	bl      do_break
> +	b	ret_from_except_full

This breaks ~35% of the defconfigs.

eg. ppc44x_defconfig
http://kisskb.ellerman.id.au/kisskb/buildresult/13113408/

  arch/powerpc/kernel/entry_32.S:(.text+0x7ac): undefined reference to `do_break'

For now I've just wrapped the asm above in:

+#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || defined(CONFIG_PPC_8xx))

But would be happy if there was something less gross.

cheers