[PATCH v6 05/39] powerpc: remove arguments from fault handler functions

[Christophe Leroy]

Le 15/01/2021 à 17:49, Nicholas Piggin a écrit :
> Make mm fault handlers all just take the pt_regs * argument and load
> DAR/DSISR from that. Make those that return a value return long.
> 
> This is done to make the function signatures match other handlers, which
> will help with a future patch to add wrappers. Explicit arguments could
> be added for performance but that would require more wrapper macro
> variants.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/include/asm/asm-prototypes.h     |  4 ++--
>   arch/powerpc/include/asm/book3s/64/mmu-hash.h |  2 +-
>   arch/powerpc/include/asm/bug.h                |  2 +-
>   arch/powerpc/kernel/entry_32.S                |  7 +------
>   arch/powerpc/kernel/exceptions-64e.S          |  2 --
>   arch/powerpc/kernel/exceptions-64s.S          | 17 ++++-------------
>   arch/powerpc/kernel/head_40x.S                | 10 +++++-----
>   arch/powerpc/kernel/head_8xx.S                |  6 +++---
>   arch/powerpc/kernel/head_book3s_32.S          |  5 ++---
>   arch/powerpc/kernel/head_booke.h              |  4 +---
>   arch/powerpc/mm/book3s64/hash_utils.c         |  8 +++++---
>   arch/powerpc/mm/book3s64/slb.c                | 11 +++++++----
>   arch/powerpc/mm/fault.c                       |  5 ++---
>   13 files changed, 34 insertions(+), 49 deletions(-)
> 

> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 238eacfda7b0..d6ea3f2d6cc0 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -276,8 +276,7 @@ reenable_mmu:
>   	 * We save a bunch of GPRs,
>   	 * r3 can be different from GPR3(r1) at this point, r9 and r11
>   	 * contains the old MSR and handler address respectively,
> -	 * r4 & r5 can contain page fault arguments that need to be passed
> -	 * along as well. r0, r6-r8, r12, CCR, CTR, XER etc... are left
> +	 * r0, r4-r8, r12, CCR, CTR, XER etc... are left
>   	 * clobbered as they aren't useful past this point.
>   	 */
>   
> @@ -285,15 +284,11 @@ reenable_mmu:
>   	stw	r9,8(r1)
>   	stw	r11,12(r1)
>   	stw	r3,16(r1)

As all functions only take 'regs' as input parameter, maybe we can avoid saving 'r3' by 
recalculating it from r1 after the call with 'addi	r3,r1,STACK_FRAME_OVERHEAD' ?

> -	stw	r4,20(r1)
> -	stw	r5,24(r1)

Patch 6 needs to go before this change. Probably the easiest would be to apply patch 6 before patch 
5. Or this change needs to go after.

>   
>   	/* If we are disabling interrupts (normal case), simply log it with
>   	 * lockdep
>   	 */
>   1:	bl	trace_hardirqs_off
> -	lwz	r5,24(r1)
> -	lwz	r4,20(r1)
>   	lwz	r3,16(r1)
>   	lwz	r11,12(r1)
>   	lwz	r9,8(r1)