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

[Andrew Donnellan]

On Mon, 2022-07-25 at 16:31 +1000, Rohan McLure wrote:
> 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.

This second paragraph is a bit unclear, I think I understand what
you're saying but could you rephrase it for clarity?

> 
> 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)

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd at linux.ibm.com   IBM Australia Limited