[PATCH 25/35] kasan: introduce CONFIG_KASAN_HW_TAGS

[Andrey Konovalov]

On Thu, Aug 27, 2020 at 1:31 PM Vincenzo Frascino
<vincenzo.frascino at arm.com> wrote:
>
> Hi Andrey,
>
> On 8/14/20 6:27 PM, Andrey Konovalov wrote:
> > +config·KASAN_HW_TAGS
> > +» bool·"Hardware·tag-based·mode"
> > +» depends·on·HAVE_ARCH_KASAN_HW_TAGS
> > +» depends·on·SLUB
> > +» help
> > +» ··Enables·hardware·tag-based·KASAN·mode.
> > +
> > +» ··This·mode·requires·both·Memory·Tagging·Extension·and·Top·Byte·Ignore
> > +» ··support·by·the·CPU·and·therefore·is·only·supported·for·modern·arm64
> > +» ··CPUs·(MTE·added·in·ARMv8.5·ISA).
> > +
>
> I do not thing we should make KASAN_HW_TAGS MTE specific especially because it
> is in the common code (e.g. SPARC ADI might want to implement it in future).
>
> 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.