> On Nov 29, 2018, at 9:45 AM, Josh Poimboeuf <jpoim...@redhat.com> wrote: > >> On Thu, Nov 29, 2018 at 09:41:33AM -0800, Andy Lutomirski wrote: >> >>> On Nov 29, 2018, at 9:21 AM, Steven Rostedt <rost...@goodmis.org> wrote: >>> >>> On Thu, 29 Nov 2018 12:20:00 -0500 >>> Steven Rostedt <rost...@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. >
Without the retpoline in place, you are vulnerable to security researchers causing you a personal denial of service by finding a way to cause the BP to get hit, mistraining the branch predictor, and writing a paper about it :)
