linux-kernel - Re: [PATCH 4/4] x86/percpu: Use C for percpu read/write accessors

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Message-ID: <CAFULd4aOSz0ZCtDdh=eST6DCr+ds2B9O2Rk0cyUeS+qQmWdOMA@mail.gmail.com>
Date:   Mon, 9 Oct 2023 14:42:10 +0200
From:   Uros Bizjak <ubizjak@...il.com>
To:     Nadav Amit <namit@...are.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 4/4] x86/percpu: Use C for percpu read/write accessors

On Mon, Oct 9, 2023 at 2:21 PM Nadav Amit <namit@...are.com> wrote:
>
>
>
> > On Oct 9, 2023, at 3:00 PM, Uros Bizjak <ubizjak@...il.com> wrote:
> >
> > !! External Email
> >
> > On Mon, Oct 9, 2023 at 1:51 PM Ingo Molnar <mingo@...nel.org> wrote:
> >>
> >> BTW., while this OK for testing, this is too heavy handed for release
> >> purposes, so please only disable the KASAN instrumentation for the affected
> >> percpu accessors.
> >>
> >> See the various __no_sanitize* attributes available.
> >
> > These attributes are for function declarations. The percpu casts can
> > not be implemented with separate static inline functions. Also,
> > __no_sanitize_address is mutually exclusive with __always_inline.
>
> Right, but for GCC you may be able to do something like:
>
>     #pragma GCC diagnostic push
>     #pragma GCC diagnostic ignored "-fsanitize=address"
>
>     // Your code here...
>     #pragma GCC diagnostic pop
>
> Not sure if there is something equivalent in CLANG, and it should be done with
> the kernel’s _Pragma.

Unfortunately, this is only for diagnostics and expects "-W..." to
suppress warnings. Here we want to disable kernel sanitizer just for
the enclosing access and I'm sure it won't work with diagnostics
pragmas. I don't think that "-fsanitize=..." is included in target or
optimization options allowed in Pragma.

Uros.