On Apr 29, 2016 3:11 PM, "Jiri Kosina" <jikos@xxxxxxxxxx> wrote: > > On Fri, 29 Apr 2016, Andy Lutomirski wrote: > > > > NMI, MCE and interrupts aren't a problem because they have dedicated > > > stacks, which are easy to detect. If the tasks' stack is on an > > > exception stack or an irq stack, we consider it unreliable. > > > > Only on x86_64. > > Well, MCEs are more or less x86-specific as well. But otherwise good > point, thanks Andy. > > So, how does stack layout generally look like in case when NMI is actually > running on proper kernel stack? I thought it's guaranteed to contain > pt_regs anyway in all cases. Is that not guaranteed to be the case? > On x86, at least, there will still be pt_regs for the NMI. For the interrupted state, though, there might not be pt_regs, as the NMI might have happened while still populating pt_regs. In fact, the NMI stack could overlap task_pt_regs. For x86_32, there's no guarantee that pt_regs contains sp due to hardware silliness. You need to parse it more carefully, as, !user_mode(regs), then the old sp is just above pt_regs. --Andy -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
