linux-kernel - Re: [GIT pull] locking/urgent for v5.12-rc3

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Message-ID: <CAHk-=wjE1Z2L87B_ahMMEd9E+jumMwsw=HDCgDkV4gmS=F9u6A@mail.gmail.com>
Date:   Mon, 15 Mar 2021 11:59:12 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [GIT pull] locking/urgent for v5.12-rc3

On Mon, Mar 15, 2021 at 10:03 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> Though instead of using objtool, it can be done in the module linker
> script:

This is obviously the way to go, but it raises another question: do we
guarantee that functions are aligned?

We actually have a couple of 32-bit x86 sub-architectures that do

    -falign-functions=0

ie Crusoe, Efficeon, and Cyrix III. Also "-Os" does that, iirc.

Is it only the static_call_sites entry itself that needs the
alignment? Or do we end up depending on the static call function being
at least 4-byte aligned too? The way it plays games with the key makes
me worry.

             Linus