linux-kernel - Re: Stackleak vs noinstr (Was: [GIT pull] objtool/core for v5.16-rc1)

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Message-ID: <CAHk-=wghWC3B6tFpQChL=q+HdUKN6R3OohPt53VsEOcKASKrRQ@mail.gmail.com>
Date:   Tue, 2 Nov 2021 10:50:06 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Alexander Popov <alex.popov@...ux.com>
Subject: Re: Stackleak vs noinstr (Was: [GIT pull] objtool/core for v5.16-rc1)

On Tue, Nov 2, 2021 at 3:05 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Having the plugin gate on section name seems a lot hacky, but given it's
> already doing that, one more doesn't hurt.

Looks sane to me.

Some of the other warnings are just odd.

Why is mce_setup() 'noinst'? I'm not seeing any reason for it, but
maybe I'm just blind. That one complains about the memcpy() call.

Of course, I suspect memcpy/memset might be better off noinstr anyway,
exactly because they can happen for very regular C code (struct
assignments etc). But mce_setup() doesn't really seem to have much
reason to not be instrumented.

             Linus