Re: [PATCH v9 23/44] kasan: separate metadata_fetch_row for each mode

[Alexander Potapenko]

On Wed, Nov 11, 2020 at 4:22 PM Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> On Tue, Nov 10, 2020 at 11:12 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> 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@xxxxxxxxxx>
> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> > Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>

> > +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.