On Thu, Nov 29, 2018 at 09:02:23AM -0800, Andy Lutomirski wrote: > > On Nov 29, 2018, at 8:50 AM, Linus Torvalds <torva...@linux-foundation.org> > > wrote:
> > So no. Do *not* try to change %rsp on the stack in the bp handler. > > Instead, I'd suggest: > > > > - just restart the instruction (with the suggested "ptregs->rip --") > > > > - to avoid any "oh, we're not making progress" issues, just fix the > > instruction yourself to be the right call, by looking it up in the > > "what needs to be fixed" tables. > > > > No? > Or do you think we can avoid the IPI while the int3 is there? I'm thinking Linus is suggesting the #BP handler does the text write too (as a competing store) and then sync_core() and restarts. But I think that is broken, because then there is no telling what the other CPUs will observe.