linux-kernel - Re: [PATCH/RESEND] recordmcount: arm: Implement make

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Date:   Tue, 15 Nov 2016 10:20:15 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Stephen Boyd <sboyd@...eaurora.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@....linux.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH/RESEND] recordmcount: arm: Implement make_nop

On Tue, 15 Nov 2016 14:19:44 +0000
Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:

> On 19 October 2016 at 00:42, Stephen Boyd <sboyd@...eaurora.org> wrote:
> > In similar spirit to x86 and arm64 support, add a make_nop_arm()
> > to replace calls to mcount with a nop in sections that aren't
> > traced.
> >
> > Cc: Russell King <linux@....linux.org.uk>
> > Acked-by: Rabin Vincent <rabin@....in>
> > Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> > ---
> >  scripts/recordmcount.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 65 insertions(+)
> >
> > diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
> > index 5423a58d1b06..aeb34223167c 100644
> > --- a/scripts/recordmcount.c
> > +++ b/scripts/recordmcount.c
> > @@ -213,6 +213,59 @@ static int make_nop_x86(void *map, size_t const offset)
> >         return 0;
> >  }
> >
> > +static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */
> > +static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */  
> 
> Shouldn't you be taking the difference between BE8 and BE32 into
> account here? IIRC, BE8 uses little endian encoding for instructions.
> 

I was just about to push this to linux-next (where I don't rebase). I'm
guessing I should hold off then.

Luckily, this was the last patch of my tree that I tested, and I can
just remove that one.

-- Steve