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

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Message-ID: <CAJF2gTQ1mpa3a9s4T-Q52Z6tugp0jMN4utdrT77ibXv3b52bQw@mail.gmail.com>
Date:   Thu, 24 Nov 2022 10:11:08 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Conor Dooley <conor@...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 Thu, Nov 24, 2022 at 4:00 AM Conor Dooley <conor@...nel.org> wrote:
>
> 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?
My fault, I missed that.

>
> Thanks,
> Conor.
>


-- 
Best Regards
 Guo Ren