Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64

Josh Poimboeuf
2018-11-29T17:46:05Z

On Thu, Nov 29, 2018 at 09:41:33AM -0800, Andy Lutomirski wrote:
>
> > On Nov 29, 2018, at 9:21 AM, Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > On Thu, 29 Nov 2018 12:20:00 -0500
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> >
> >> r8 = return address
> >> r9 = function to call
> >>
> >
> > Bad example, r8 and r9 are args, but r10 and r11 are available.
> >
> > -- Steve
> >
> >> push r8
> >> jmp *r9
> >>
> >> Then have the regs->ip point to that trampoline.
>
> Cute. That’ll need ORC annotations and some kind of retpoline to replace the indirect jump, though.

I'm going with this idea, but the BP is so rare that I really don't see
why a retpoline would be needed.

--
Josh