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

Ard Biesheuvel
2019-11-07T10:52:09Z

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.