linux-kernel - Re: [GIT PULL] x86/asm changes for v5.6

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Message-ID: <CAHk-=wje_k92K6j0-=HH4F5Jmr8Fv7vB-ANObqbQeGS_RsikWA@mail.gmail.com>
Date:   Thu, 30 Jan 2020 07:27:28 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Borislav Petkov <bp@...e.de>
Cc:     "Luck, Tony" <tony.luck@...el.com>, Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/asm changes for v5.6

On Thu, Jan 30, 2020 at 12:51 AM Borislav Petkov <bp@...e.de> wrote:
>
> However, this new version has hit another shortcoming of the
> alternatives - check this out:

[ Branches not getting fixed up ]

Fair enough. Let's not complicate things just to avoid a few nops.

That does make me wonder about RIP-relative addressing in alternatives
too. Particularly anything where we let gcc pick addressing modes. I
guess we don't have any, but maybe this branch issue and possible RIP
addressing is something that objtool could be taught to warn about?

                  Linus