linux-kernel - Re: [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER_

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Message-ID: <CAKwvOdnB=OfCc_31b=PMjxKewvb3CV2WDwhMWrigviWaHrGMhw@mail.gmail.com>
Date:   Mon, 31 Jan 2022 12:45:20 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Segher Boessenkool <segher@...nel.crashing.org>,
        apinski@...vell.com
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        x86@...nel.org, llvm@...ts.linux.dev, linux-sparse@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-toolchains@...r.kernel.org
Subject: Re: [PATCH] objtool: prefer memory clobber & %= to volatile & __COUNTER__

On Tue, Jan 25, 2022 at 3:34 PM Segher Boessenkool
<segher@...nel.crashing.org> wrote:
>
> Hi!
>
> On Mon, Jan 24, 2022 at 03:26:36PM -0800, Nick Desaulniers wrote:
> > I'm more confident that we can remove the `volatile` keyword (I was
> > thinking about adding a new diagnostic to clang to warn that volatile
> > is redundate+implied for asm goto or inline asm that doesn't have
> > outputs) though that's not the problem here and will probably generate
> > some kernel wide cleanup before we could enable such a flag.
>
> Its main value is that it would discourage users from thinking volatile
> is magic.  Seriously worth some pain!

https://reviews.llvm.org/D118297
PTAL
-- 
Thanks,
~Nick Desaulniers