Re: [PATCH V3 3/5] riscv: ftrace: Reduce the detour code size to half

From: Conor Dooley
Date: Wed Nov 23 2022 - 15:01:42 EST


On Wed, Nov 23, 2022 at 10:39:48AM -0500, guoren@xxxxxxxxxx wrote:
> From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
>
> Use a temporary register to reduce the size of detour code from
> 16 bytes to 8 bytes. The previous implementation is from
> afc76b8b8011 ("riscv: Using PATCHABLE_FUNCTION_ENTRY instead of
> MCOUNT").
>
> Before the patch:
> <func_prolog>:
> 0: REG_S ra, -SZREG(sp)
> 4: auipc ra, ?
> 8: jalr ?(ra)
> 12: REG_L ra, -SZREG(sp)
> (func_boddy)
>
> After the patch:
> <func_prolog>:
> 0: auipc t0, ?
> 4: jalr t0, ?(t0)
> (func_boddy)
>
> Link: https://lore.kernel.org/linux-riscv/20221122075440.1165172-1-suagrfillet@xxxxxxxxx/
> Co-developed-by: Song Shuai <suagrfillet@xxxxxxxxx>
> Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>

FYI missing a sign-off from Song Shuai. They were happy with you folding
their patch in during the discussion linked above - so I suppose that is
an accidental omission?

Thanks,
Conor.