linux-kernel - Re: [PATCH -tip v2 00/11] Fix KCSAN for new ONCE (require Clang 11)

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Message-ID: <20200521133626.GD6608@willie-the-truck>
Date:   Thu, 21 May 2020 14:36:27 +0100
From:   Will Deacon <will@...nel.org>
To:     Marco Elver <elver@...gle.com>
Cc:     paulmck@...nel.org, dvyukov@...gle.com, glider@...gle.com,
        andreyknvl@...gle.com, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...nel.org,
        peterz@...radead.org, clang-built-linux@...glegroups.com,
        bp@...en8.de
Subject: Re: [PATCH -tip v2 00/11] Fix KCSAN for new ONCE (require Clang 11)

On Thu, May 21, 2020 at 01:08:43PM +0200, Marco Elver wrote:
> This patch series is the conclusion to [1], where we determined that due
> to various interactions with no_sanitize attributes and the new
> {READ,WRITE}_ONCE(), KCSAN will require Clang 11 or later. Other
> sanitizers are largely untouched, and only KCSAN now has a hard
> dependency on Clang 11. To test, a recent Clang development version will
> suffice [2]. While a little inconvenient for now, it is hoped that in
> future we may be able to fix GCC and re-enable GCC support.
> 
> The patch "kcsan: Restrict supported compilers" contains a detailed list
> of requirements that led to this decision.
> 
> Most of the patches are related to KCSAN, however, the first patch also
> includes an UBSAN related fix and is a dependency for the remaining
> ones. The last 2 patches clean up the attributes by moving them to the
> right place, and fix KASAN's way of defining __no_kasan_or_inline,
> making it consistent with KCSAN.
> 
> The series has been tested by running kcsan-test several times and
> completed successfully.

I've left a few minor comments, but the only one that probably needs a bit
of thought is using data_race() with const non-scalar expressions, since I
think that's now prohibited by these changes. We don't have too many
data_race() users yet, so probably not a big deal, but worth bearing in
mind.

Other than that,

Acked-by: Will Deacon <will@...nel.org>

Thanks!

Will