Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <cover.1597425745.git.andreyknvl@google.com> <8a499341bbe4767a4ee1d3b8acb8bd83420ce3a5.1597425745.git.andreyknvl@google.com>
 <b7884e93-008f-6b9f-32d8-6c03c7e14243@arm.com>
In-Reply-To: <b7884e93-008f-6b9f-32d8-6c03c7e14243@arm.com>
From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Thu, 27 Aug 2020 14:22:55 +0200
Message-ID: <CAAeHK+x+DMs9jdeB58XaoJTO-kv+iiWT1_BuhYiJzJH-DoY9EQ@mail.gmail.com>
Subject: Re: [PATCH 25/35] kasan: introduce CONFIG_KASAN_HW_TAGS
To:     Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Cc:     Dmitry Vyukov <dvyukov@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Elena Petrova <lenaptr@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Aug 27, 2020 at 1:31 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi Andrey,
>
> On 8/14/20 6:27 PM, Andrey Konovalov wrote:
> > +config=C2=B7KASAN_HW_TAGS
> > +=C2=BB bool=C2=B7"Hardware=C2=B7tag-based=C2=B7mode"
> > +=C2=BB depends=C2=B7on=C2=B7HAVE_ARCH_KASAN_HW_TAGS
> > +=C2=BB depends=C2=B7on=C2=B7SLUB
> > +=C2=BB help
> > +=C2=BB =C2=B7=C2=B7Enables=C2=B7hardware=C2=B7tag-based=C2=B7KASAN=C2=
=B7mode.
> > +
> > +=C2=BB =C2=B7=C2=B7This=C2=B7mode=C2=B7requires=C2=B7both=C2=B7Memory=
=C2=B7Tagging=C2=B7Extension=C2=B7and=C2=B7Top=C2=B7Byte=C2=B7Ignore
> > +=C2=BB =C2=B7=C2=B7support=C2=B7by=C2=B7the=C2=B7CPU=C2=B7and=C2=B7the=
refore=C2=B7is=C2=B7only=C2=B7supported=C2=B7for=C2=B7modern=C2=B7arm64
> > +=C2=BB =C2=B7=C2=B7CPUs=C2=B7(MTE=C2=B7added=C2=B7in=C2=B7ARMv8.5=C2=
=B7ISA).
> > +
>
> I do not thing we should make KASAN_HW_TAGS MTE specific especially becau=
se it
> is in the common code (e.g. SPARC ADI might want to implement it in futur=
e).
>
> Probably would be better to provide some indirection in the generic code =
an
> implement the MTE backend entirely in arch code.
>
> Thoughts?

I think we can reword the help text to say that it enables tag-based
KASAN mode that is backed by the hardware in general, and mention that
this is currently only implemented for arm64 through MTE. I don't
think it makes sense to provide a common arch interface at this point
to keep the code simpler. We can do that when (and if) another
hardware backend is added.