On 11/30/2017, 08:59 PM, Josh Poimboeuf wrote: > On Thu, Nov 30, 2017 at 01:57:10PM -0600, Josh Poimboeuf wrote: >> On Thu, Nov 30, 2017 at 09:03:24AM +0100, Jiri Slaby wrote: >>> save_stack_trace_reliable now returns "non reliable" when there are >>> kernel pt_regs on stack. This means an interrupt or exception happened. >>> Somewhere down the route. It is a problem for frame pointer unwinder, >>> because the frame might now have been set up yet when the irq happened, >>> so it might fail to unwind from the interrupted function. >>> >>> With ORC, this is not a problem, as ORC has out-of-band data. We can >>> find ORC data even for the IP in interrupted function and always unwind >>> one level up. >>> >>> So introduce `unwind_regs_reliable' which decides if this is an issue >>> for the currently selected unwinder at all and change the code >>> accordingly. >> >> Thanks. I'm thinking there a few ways we can simplify things. (Most of >> these are actually issues with the existing code.) >> >> - Currently we check to make sure that there's no frame *after* the user >> space regs. I think there's no way that could ever happen and the >> check is overkill. >> >> - We should probably remove the STACKTRACE_DUMP_ONCE() warnings. There >> are some known places where a stack trace will fail, particularly with >> generated code. I wish we had a DEBUG_WARN_ON() macro which used >> pr_debug(), but oh well. At least the livepatch code has some helpful >> pr_warn()s, those are probably good enough. > ^^^^^^^ > meant to say pr_debug()s. > > Also adding the live patching mailing list as an FYI. The changes are now in: https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git/log/?h=devel Letting 01 bot to run through them, then I will send a v2. thanks, -- js suse labs -- 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
