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

From	Mark Rutland <mark.rutland@arm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86, kasan: add KASAN checks to atomic operations
Date	2017-03-14 16:50 +0100
Message-ID	<tkWRX-29k-3@gated-at.bofh.it> (permalink)
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On Tue, Mar 14, 2017 at 04:32:30PM +0100, Peter Zijlstra wrote:
> On Tue, Mar 14, 2017 at 04:22:52PM +0100, Dmitry Vyukov 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.

Thanks,
Mark.

Thread

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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