Re: [PATCH] x86, kasan: add KASAN checks to atomic operations

From	Dmitry Vyukov <dvyukov@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86, kasan: add KASAN checks to atomic operations
Date	2017-03-14 20:30 +0100
Message-ID	<tl0iS-4M7-13@gated-at.bofh.it> (permalink)
References	(6 earlier) <tiLHj-8qM-9@gated-at.bofh.it> <tiOOS-1ZF-5@gated-at.bofh.it> <tkWyD-20n-39@gated-at.bofh.it> <tkWIi-25L-7@gated-at.bofh.it> <tkWRX-29k-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Mar 14, 2017 at 4:44 PM, Mark Rutland <mark.rutland@arm.com> wrote:
>> > -static __always_inline int atomic_read(const atomic_t *v)
>> > +static __always_inline int arch_atomic_read(const atomic_t *v)
>> >  {
>> > -   return READ_ONCE((v)->counter);
>> > +   return READ_ONCE_NOCHECK((v)->counter);
>>
>> Should NOCHEKC come with a comment, because i've no idea why this is so.
>
> I suspect the idea is that given the wrapper will have done the KASAN
> check, duplicating it here is either sub-optimal, or results in
> duplicate splats. READ_ONCE() has an implicit KASAN check,
> READ_ONCE_NOCHECK() does not.
>
> If this is to solve duplicate splats, it'd be worth having a
> WRITE_ONCE_NOCHECK() for arch_atomic_set().
>
> Agreed on the comment, regardless.


Reverted xchg changes.
Added comments re READ_ONCE_NOCHECK() and WRITE_ONCE().
Added file comment.
Split into 3 patches and mailed.

Thanks!

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Re: [PATCH] x86, kasan: add KASAN checks to atomic operations Peter Zijlstra <peterz@infradead.org> - 2017-03-14 16:40 +0100
  Re: [PATCH] x86, kasan: add KASAN checks to atomic operations Mark Rutland <mark.rutland@arm.com> - 2017-03-14 16:50 +0100
    Re: [PATCH] x86, kasan: add KASAN checks to atomic operations Dmitry Vyukov <dvyukov@google.com> - 2017-03-14 20:30 +0100

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