[PATCH v2 12/14] powerpc/64s: Use {NULLIFY,SAVE,REST}_GPRS macros in sc, scv 0 handlers

[Christophe Leroy]

Le 25/07/2022 à 08:31, Rohan McLure a écrit :
> Use the convenience macros for saving/clearing/restoring gprs in keeping
> with syscall calling conventions. The plural variants of these macros
> can store a range of registers for concision.
> 
> This works well when the save-to-stack logic is simple (a gpr is saved
> to its corresponding offset in the struct pt_regs on the stack).
> Wherever a different gpr is storing the initial value of another gpr at
> the interrupt location, care must be taken to issue the correct save
> instruction and so the macros are not applied in neighbouring stores.

Some cleaning could also be done in entry_32.S



> 
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
> ---
> V1 -> V2: Update summary
> ---
>   arch/powerpc/kernel/interrupt_64.S | 29 ++++++----------------------
>   1 file changed, 6 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index 34167cfa5d60..efaf162fa772 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -71,12 +71,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
>   	mfcr	r12
>   	li	r11,0
>   	/* Save syscall parameters in r3-r8 */
> -	std	r3,GPR3(r1)
> -	std	r4,GPR4(r1)
> -	std	r5,GPR5(r1)
> -	std	r6,GPR6(r1)
> -	std	r7,GPR7(r1)
> -	std	r8,GPR8(r1)
> +	SAVE_GPRS(3, 8, r1)
>   	/* Zero r9-r12, this should only be required when restoring all GPRs */
>   	std	r11,GPR9(r1)
>   	std	r11,GPR10(r1)
> @@ -156,17 +151,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>   	/* Could zero these as per ABI, but we may consider a stricter ABI
>   	 * which preserves these if libc implementations can benefit, so
>   	 * restore them for now until further measurement is done. */
> -	ld	r0,GPR0(r1)
> -	ld	r4,GPR4(r1)
> -	ld	r5,GPR5(r1)
> -	ld	r6,GPR6(r1)
> -	ld	r7,GPR7(r1)
> -	ld	r8,GPR8(r1)
> +	REST_GPR(0, r1)
> +	REST_GPRS(4, 8, r1)
>   	/* Zero volatile regs that may contain sensitive kernel data */
> -	li	r9,0
> -	li	r10,0
> -	li	r11,0
> -	li	r12,0
> +	NULLIFY_GPRS(9, 12)
>   	mtspr	SPRN_XER,r0
>   
>   	/*
> @@ -188,7 +176,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>   	ld	r4,_LINK(r1)
>   	ld	r5,_XER(r1)
>   
> -	ld	r0,GPR0(r1)
> +	REST_GPR(0, r1)
>   	mtcr	r2
>   	mtctr	r3
>   	mtlr	r4
> @@ -256,12 +244,7 @@ END_BTB_FLUSH_SECTION
>   	mfcr	r12
>   	li	r11,0
>   	/* Save syscall parameters in r3-r8 */
> -	std	r3,GPR3(r1)
> -	std	r4,GPR4(r1)
> -	std	r5,GPR5(r1)
> -	std	r6,GPR6(r1)
> -	std	r7,GPR7(r1)
> -	std	r8,GPR8(r1)
> +	SAVE_GPRS(3, 8, r1)
>   	/* Zero r9-r12, this should only be required when restoring all GPRs */
>   	std	r11,GPR9(r1)
>   	std	r11,GPR10(r1)