xtensa: add trap_set_handler function

trap_set_handler sets new C-handler in the exception table and returns
previous handler.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/include/asm/traps.h b/arch/xtensa/include/asm/traps.h
new file mode 100644
index 0000000..54f7044
--- /dev/null
+++ b/arch/xtensa/include/asm/traps.h
@@ -0,0 +1,23 @@
+/*
+ * arch/xtensa/include/asm/traps.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2012 Tensilica Inc.
+ */
+#ifndef _XTENSA_TRAPS_H
+#define _XTENSA_TRAPS_H
+
+#include <asm/ptrace.h>
+
+/*
+ * handler must be either of the following:
+ *  void (*)(struct pt_regs *regs);
+ *  void (*)(struct pt_regs *regs, unsigned long exccause);
+ */
+extern void * __init trap_set_handler(int cause, void *handler);
+extern void do_unhandled(struct pt_regs *regs, unsigned long exccause);
+
+#endif /* _XTENSA_TRAPS_H */