linux-kernel - Re: [PATCH] tools/nolibc: x86: Remove `r8`, `r9` and `r10` from the clobber list

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Date:   Tue, 12 Oct 2021 11:06:38 +0200
From:   Willy Tarreau <w@....eu>
To:     Ammar Faizi <ammar.faizi@...dents.amikom.ac.id>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] tools/nolibc: x86: Remove `r8`, `r9` and `r10` from the
 clobber list

On Tue, Oct 12, 2021 at 03:36:44PM +0700, Ammar Faizi wrote:
> I have tried to search for the documentation about this one, but I
> couldn't find any. Checking at `Documentation/x86/entry_64.rst`, but
> it doesn't tell anything relevant.
(...)

OK thanks for the detailed story, thus I didn't miss any obvious
reference.

> My stance comes from SO, Telegram group discussion, and reading source
> code. Therefore, I don't think I can attach the link to it as
> "authoritative information". Or can I?

You're right, that's not exactly what we can call authoritative :-)

> When I sent this patch, I also added entry_64.S's maintainers to CC
> list. In hope they can help to at least acknowledge it. Mainly because
> I can't find the documentation from Linux that tells about this.
> 
> Andy, Thomas, Ingo, Borislav, H. Peter.
> 
> Could one of you shed some light so that I can attach the link to your
> message in the commit message?

Let's indeed wait for any of the x86 maintainers to confirm your
analysis.

Thanks!
Willy