kprobes, x86: Prohibit probing on thunk functions and restore

thunk/restore functions are also used for tracing irqoff etc.
and those are involved in kprobe's exception handling.
Prohibit probing on them to avoid kernel crash.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20140417081726.26341.3872.stgit@ltc230.yrl.intra.hitachi.co.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/lib/thunk_64.S

@@ -8,6 +8,7 @@
 #include <linux/linkage.h>
 #include <asm/dwarf2.h>
 #include <asm/calling.h>
+#include <asm/asm.h>
 
 	/* rdi:	arg1 ... normal C conventions. rax is saved/restored. */
 	.macro THUNK name, func, put_ret_addr_in_rdi=0
@@ -25,6 +26,7 @@
 	call \func
 	jmp  restore
 	CFI_ENDPROC
+	_ASM_NOKPROBE(\name)
 	.endm
 
 #ifdef CONFIG_TRACE_IRQFLAGS
@@ -43,3 +45,4 @@ restore:
 	RESTORE_ARGS
 	ret
 	CFI_ENDPROC
+	_ASM_NOKPROBE(restore)