From 6f6343f53d133bae516caf3d254bce37d8774625 Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Date: Thu, 17 Apr 2014 17:17:33 +0900
Subject: [PATCH] kprobes/x86: Call exception handlers directly from
 do_int3/do_debug

To avoid a kernel crash by probing on lockdep code, call
kprobe_int3_handler() and kprobe_debug_handler()(which was
formerly called post_kprobe_handler()) directly from
do_int3 and do_debug.

Currently kprobes uses notify_die() to hook the int3/debug
exceptoins. Since there is a locking code in notify_die,
the lockdep code can be invoked. And because the lockdep
involves printk() related things, theoretically, we need to
prohibit probing on such code, which means much longer blacklist
we'll have. Instead, hooking the int3/debug for kprobes before
notify_die() can avoid this problem.

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.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Jonathan Lebon <jlebon@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Link: http://lkml.kernel.org/r/20140417081733.26341.24423.stgit@ltc230.yrl.intra.hitachi.co.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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