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

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Date:   Wed, 23 Nov 2022 20:00:51 +0000
From:   Conor Dooley <conor@...nel.org>
To:     guoren@...nel.org
Cc:     anup@...infault.org, paul.walmsley@...ive.com, palmer@...belt.com,
        conor.dooley@...rochip.com, heiko@...ech.de, rostedt@...dmis.org,
        mhiramat@...nel.org, jolsa@...hat.com, bp@...e.de,
        jpoimboe@...nel.org, suagrfillet@...il.com, andy.chiu@...ive.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V3 3/5] riscv: ftrace: Reduce the detour code size to half

On Wed, Nov 23, 2022 at 10:39:48AM -0500, guoren@...nel.org wrote:
> From: Guo Ren <guoren@...ux.alibaba.com>
> 
> 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@gmail.com/
> Co-developed-by: Song Shuai <suagrfillet@...il.com>
> Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@...nel.org>

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.