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Subject: Re: [PATCH v14 2/4] kasan: allow architectures to provide an outline
 readiness check
To:     Daniel Axtens <dja@axtens.net>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, kasan-dev@googlegroups.com, elver@google.com,
        akpm@linux-foundation.org, andreyknvl@gmail.com
Cc:     linuxppc-dev@lists.ozlabs.org, aneesh.kumar@linux.ibm.com,
        bsingharora@gmail.com,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
References: <20210617063956.94061-1-dja@axtens.net>
 <20210617063956.94061-3-dja@axtens.net>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <853a39a4-5ec3-08a9-87d0-d599e8828e8b@csgroup.eu>
Date:   Thu, 17 Jun 2021 08:55:40 +0200
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Le 17/06/2021 à 08:39, Daniel Axtens a écrit :
> Allow architectures to define a kasan_arch_is_ready() hook that bails
> out of any function that's about to touch the shadow unless the arch
> says that it is ready for the memory to be accessed. This is fairly
> uninvasive and should have a negligible performance penalty.
> 
> This will only work in outline mode, so an arch must specify
> ARCH_DISABLE_KASAN_INLINE if it requires this.
> 
> Cc: Balbir Singh <bsingharora@gmail.com>
> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Signed-off-by: Daniel Axtens <dja@axtens.net>
> 
> --
> 
> Both previous RFCs for ppc64 - by 2 different people - have
> needed this trick! See:
>   - https://lore.kernel.org/patchwork/patch/592820/ # ppc64 hash series
>   - https://patchwork.ozlabs.org/patch/795211/      # ppc radix series
> 
> I haven't been able to exercise the arch hook error for !GENERIC as I
> don't have a particularly modern aarch64 toolchain or a lot of experience
> cross-compiling with clang. But it does fire for GENERIC + INLINE on x86.

Modern toolchains are available here https://mirrors.edge.kernel.org/pub/tools/crosstool/