Re: [PATCH v4 04/15] cfi: Add DEFINE_CFI_IMMEDIATE_RETURN_STUB

Sami Tolvanen
2021-10-05T21:53:41Z

On Tue, Oct 5, 2021 at 1:58 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Tue, Oct 05, 2021 at 01:29:02PM -0700, Sami Tolvanen wrote:
> > On Mon, Oct 4, 2021 at 11:59 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> > > For x86_64 it should indeed never get called, however if you plan on
> > > supporting i386 then you need the annotation. Also, it might get called
> > > on arm64 which is about to grow basic HAVE_STATIC_CALL support.
> >
> > Good point. I read through the latest arm64 static call proposal and
> > while it can fall back to an indirect call, it doesn't look like that
> > would cause issues with CFI.
>
> Because that call is outside of compiler control?

Correct.

> Same will be true for
> any HAVE_STATIC_CALL implementation I suppose. The trampoline will be
> outside of compiler control.

True, so it shouldn't be a problem.

Sami