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From:   Sami Tolvanen <samitolvanen@google.com>
Date:   Fri, 18 Oct 2019 12:00:30 -0700
Message-ID: <CABCJKuf1cTHqvAC2hyCWjQbNEdGjx8dtfHGWwEvrEWzv+f7vZg@mail.gmail.com>
Subject: Re: [PATCH 05/18] arm64: kbuild: reserve reg x18 from general
 allocation by the compiler
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Dave Martin <Dave.Martin@arm.com>,
        Kees Cook <keescook@chromium.org>,
        Laura Abbott <labbott@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Oct 18, 2019 at 10:32 AM 'Nick Desaulniers' via Clang Built
Linux <clang-built-linux@googlegroups.com> wrote:
> > and remove the mention from
> > the LL/SC compiler flag override.
>
> was that cut/dropped from this patch?
>
> >
> > Link: https://patchwork.kernel.org/patch/9836881/
>
> ^ Looks like it. Maybe it doesn't matter, but if sending a V2, maybe
> the commit message to be updated?

True. The original patch is from 2017 and the relevant part of
arm64/lib/Makefile no longer exists. I'll update this accordingly.

> I like how this does not conditionally reserve it based on the CONFIG
> for SCS.  Hopefully later patches don't wrap it, but I haven't looked
> through all of them yet.

In a later patch x18 is only reserved with SCS. I'm fine with dropping
that patch and reserving it always, but wouldn't mind hearing thoughts
from the maintainers about this first.

Sami