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

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Date:   Mon, 9 Oct 2023 12:53:03 +0000
From:   Nadav Amit <namit@...are.com>
To:     Uros Bizjak <ubizjak@...il.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 Oct 9, 2023, at 3:42 PM, Uros Bizjak <ubizjak@...il.com> wrote:
> 
> !! External Email
> 
> 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.

Ugh. Sorry for the noise. You seem to be right.