x86, trace: Register exception handler to trace IDT

This patch registers exception handlers for tracing to a trace IDT.

To implemented it in set_intr_gate(), this patch does followings.
 - Register the exception handlers to
   the trace IDT by prepending "trace_" to the handler's names.
 - Also, newly introduce trace_page_fault() to add tracepoints
   in a subsequent patch.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Link: http://lkml.kernel.org/r/52716DEC.5050204@hds.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/segment.h

@@ -214,6 +214,9 @@
 #ifdef __KERNEL__
 #ifndef __ASSEMBLY__
 extern const char early_idt_handlers[NUM_EXCEPTION_VECTORS][2+2+5];
+#ifdef CONFIG_TRACING
+#define trace_early_idt_handlers early_idt_handlers
+#endif
 
 /*
  * Load a segment. Fall back on loading the zero