Messages in this thread |  | | Date | Wed, 11 Dec 2013 14:31:33 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [PATCH -tip v4 6/6] [RFC] kprobes/x86: Call exception handlers directly from do_int3/do_debug |
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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 <jkosina@suse.cz> 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?
-- Jiri Kosina SUSE Labs
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