(2013/12/11 22:31), Jiri Kosina wrote: > On Tue, 3 Dec 2013, Steven Rostedt wrote: > >>> To avoid a kernel crash by probing on lockdep code, call >>> kprobe_int3_handler and kprobe_debug_handler directly >>> from do_int3 and do_debug. Since there is a locking code >>> in notify_die, lockdep code can be invoked. And because >>> the lockdep involves printk() related things, theoretically, >>> we need to prohibit probing on much more code... >>> >>> Anyway, most of the int3 handlers in the kernel are already >>> called from do_int3 directly, e.g. ftrace_int3_handler, >>> poke_int3_handler, kgdb_ll_trap. Actually only >>> kprobe_exceptions_notify is on the notifier_call_chain. >>> >>> So I think this is not a crazy thing. >> >> What? Oh, yeah. No, using notifiers in int3 handler is the crazy >> thing ;-) > > Yeah, it's broken. Obviously, if you happen to trigger int3 before the > notifier has been registered, it'd cause int3 exception to be unhandled. > See > > commit 17f41571bb2c4a398785452ac2718a6c5d77180e > Author: Jiri Kosina <[email protected]> > Date: Tue Jul 23 10:09:28 2013 +0200 > > kprobes/x86: Call out into INT3 handler directly instead of using > notifier > > for one such issue that happened with jump labels. > >> Hmm, if there's no users of the int3 notifier, should we just remove it? > > Hmm, there are still uprobes, right?
Right, uprobes still use it, however, since it only handles user-space breakpoint, there is no problem. Thank you! -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: [email protected] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
