linux-kernel - Re: [PATCH v9 23/44] kasan: separate metadata_fetch

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Date:   Wed, 11 Nov 2020 17:19:28 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 23/44] kasan: separate metadata_fetch_row for each mode

On Wed, Nov 11, 2020 at 4:22 PM Alexander Potapenko <glider@...gle.com> wrote:
>
> On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
> >
> > This is a preparatory commit for the upcoming addition of a new hardware
> > tag-based (MTE-based) KASAN mode.
> >
> > Rework print_memory_metadata() to make it agnostic with regard to the
> > way metadata is stored. Allow providing a separate metadata_fetch_row()
> > implementation for each KASAN mode. Hardware tag-based KASAN will provide
> > its own implementation that doesn't use shadow memory.
> >
> > No functional changes for software modes.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@....com>
> > Reviewed-by: Marco Elver <elver@...gle.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>

> > +void metadata_fetch_row(char *buffer, void *row)
> > +{
> > +       memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
>
> I think it is important to use __memcpy() instead of memcpy() in KASAN
> runtime to avoid calling instrumented code.

Please disregard this. Turns out we define memcpy to __memcpy for
non-instrumented files.