kprobes, x86: Prohibit probing on native_set_debugreg()/load_idt()

Since the kprobes uses do_debug for single stepping,
functions called from do_debug() before notify_die() must not
be probed.

And also native_load_idt() is called from paranoid_exit when
returning int3, this also must not be probed.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20140417081719.26341.65542.stgit@ltc230.yrl.intra.hitachi.co.jpSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/paravirt.c

@@ -390,8 +390,10 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
 	.end_context_switch = paravirt_nop,
 };
 
-/* At this point, native_get_debugreg has a real function entry */
+/* At this point, native_get/set_debugreg has real function entries */
 NOKPROBE_SYMBOL(native_get_debugreg);
+NOKPROBE_SYMBOL(native_set_debugreg);
+NOKPROBE_SYMBOL(native_load_idt);
 
 struct pv_apic_ops pv_apic_ops = {
 #ifdef CONFIG_X86_LOCAL_APIC