linux-kernel - Re: [PATCH 1/8] kasan,x86: Frob kasan

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Message-ID: <CAHk-=wiDfi_=hny1hDCrxaEUUcgvykaWXt4f1qn+pt1RD1OFLQ@mail.gmail.com>
Date:   Wed, 6 Mar 2019 09:59:11 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Julien Thierry <julien.thierry@....com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>, valentin.schneider@....com,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH 1/8] kasan,x86: Frob kasan_report() in an exception

On Wed, Mar 6, 2019 at 9:37 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> The below seems to 'work'.

Yeah, and makes things cheaper for the non-SMAP case too. Looks sane.

One note:

 +       asm volatile (ALTERNATIVE("", "pushf; pop %0; "
__stringify(__ASM_CLAC),

Hmm. Every single use of __ASM_CLAC is together with "__stringity()".

Maybe we could just get rid of that oddity, and just make __ASM_CLAC
be a string to begin with.

At one point it was used bare in the __ASSEMBLY__ version, but that
does not appear to the case any more since commit 669f8a900198
("x86/smap: Use ALTERNATIVE macro") back in 2015.

                 Linus