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From:   Linus Walleij <linus.walleij@linaro.org>
Date:   Wed, 3 Mar 2021 16:31:41 +0100
Message-ID: <CACRpkdYM3x6pJU3Vi+EEHtC3wD1DkrtVbGDd3PFHWL0fxjSA9g@mail.gmail.com>
Subject: Re: [PATCH v4] ARM: Implement SLS mitigation
To:     David Laight <David.Laight@aculab.com>
Cc:     Will Deacon <will@kernel.org>, Jian Cai <jiancai@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Manoj Gupta <manojgupta@google.com>,
        Luis Lozano <llozano@google.com>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Ard Biesheuvel <ardb@kernel.org>,
        =?UTF-8?Q?Andreas_F=C3=A4rber?= <afaerber@suse.de>,
        Ingo Molnar <mingo@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
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On Wed, Mar 3, 2021 at 4:29 PM David Laight <David.Laight@aculab.com> wrote:
> > On Tue, Feb 23, 2021 at 11:05 AM Will Deacon <will@kernel.org> wrote:

> > I wrote some suggestions on follow-ups in my reply, and I can
> > help out doing some of the patches, I think.
> >
> > Since ARM32 RET is mov pc, <>
> > git grep 'mov.*pc,' | wc -l gives 93 sites in arch/arm.
> > I suppose these need to come out:
> >
> > mov pc, lr
> > dsb(nsh);
> > isb();
>
> Won't that go horribly wrong for conditional returns?

It will so I would not insert it after those. It has to be
on a case-by-base basis, I am not planning any
search and replace operations.

Yours,
Linus Walleij