On Wed, Oct 10, 2018 at 02:56:08PM -0400, Steven Rostedt wrote: > On Wed, 10 Oct 2018 13:33:30 -0500 > Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > Re-reading your suggestion, I may have misunderstood what you're > > suggesting here, but I'm thinking about doing something like what you > > proposed earlier: > > > > GLOBAL(tramp) > > jmp *current_func(%rip) > > ENDPROC(tramp) > > > > That is, doing an indirect jump instead of the above direct jump, so > > that any previous references to the trampoline would still work (and it > > would also work during early boot). > > > > Though it should probably be a retpoline instead of an indirect jump. > > But do we care, as it only takes place during text_poke_bp() right? > > I don't think we need to worry about training trampoline branch > prediction that can only be hit when something enables the jump.
Yeah, I guess it depends on if we'd expect anybody (or gcc) to get a function pointer to the trampoline itself. I can just create a warning for that in objtool. -- Josh
