linux-kernel - Re: [GIT PULL] x86/urgent for v5.11-rc7

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Message-Id: <3C17D187-8691-4521-9B64-F42A0B514F13@amacapital.net>
Date:   Tue, 9 Feb 2021 10:26:37 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...e.de>,
        Dave Hansen <dave.hansen@...el.com>, x86-ml <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        live-patching@...r.kernel.org
Subject: Re: [GIT PULL] x86/urgent for v5.11-rc7



> On Feb 9, 2021, at 10:09 AM, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> On Tue, Feb 9, 2021 at 8:55 AM Andy Lutomirski <luto@...capital.net> wrote:
>> 
>> Or we hack up #CP to handle this case. I don’t quite know how I feel about this.
> 
> I think that's the sane model - if we've replaced the instruction with
> 'int3', and we end up getting #CP due to that, just do the #BP
> handling.
> 
> Anything else would just be insanely complicated, I feel.

The other model is “don’t do that then.”

I suppose a nice property of patching ENDBR to INT3 is that, not only is it atomic, but ENDBR is sort of a NOP, so we don’t need to replace the ENDBR with anything.

> 
>             Linus