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Date: Wed, 04 Dec 2013 02:39:00 -0000
From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@kernel.org>, Andi Kleen <ak@linux.intel.com>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Sandeepa Prabhu <sandeepa.prabhu@linaro.org>, Frederic Weisbecker <fweisbec@gmail.com>, x86@kernel.org, lkml <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@redhat.com>, systemtap@sourceware.org, "H. Peter Anvin" <hpa@zytor.com>, Sasha Levin <sasha.levin@oracle.com>, Thomas Gleixner <tglx@linutronix.de>, Seiji Aguchi <seiji.aguchi@hds.com>, "David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH -tip v4 6/6] [RFC] kprobes/x86: Call exception handlers directly from do_int3/do_debug
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On Wed, 04 Dec 2013 01:28:56 +0000
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> 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 ;-)

Hmm, if there's no users of the int3 notifier, should we just remove it?

-- Steve