Re: [PATCH v5 11/14] arm64: efi: restore x18 if it was corrupted

Sami Tolvanen
2019-11-07T16:26:59Z

On Thu, Nov 7, 2019 at 2:51 AM Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>
> On Wed, 6 Nov 2019 at 05:46, Miguel Ojeda
> <miguel.ojeda.sandonis@gmail.com> wrote:
> >
> > On Wed, Nov 6, 2019 at 12:56 AM Sami Tolvanen <samitolvanen@google.com> wrote:
> > >
> > > If we detect a corrupted x18 and SCS is enabled, restore the register
> > > before jumping back to instrumented code. This is safe, because the
> > > wrapper is called with preemption disabled and a separate shadow stack
> > > is used for interrupt handling.
> >
> > In case you do v6: I think putting the explanation about why this is
> > safe in the existing comment would be best given it is justifying a
> > subtlety of the code rather than the change itself. Ard?
> >
>
> Agreed, but only if you have to respin for other reasons.

Sure, sounds good to me. I'll update the comment if other changes are needed.

Sami