x86-64: Add vsyscall:emulate_vsyscall trace event

Vsyscall emulation is slow, so make it easy to track down.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/cdaad7da946a80b200df16647c1700db3e1171e9.1312378163.git.luto@mit.edu
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/vsyscall_64.c

@@ -50,6 +50,9 @@
 #include <asm/vgtod.h>
 #include <asm/traps.h>
 
+#define CREATE_TRACE_POINTS
+#include "vsyscall_trace.h"
+
 DEFINE_VVAR(int, vgetcpu_mode);
 DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) =
 {
@@ -146,6 +149,9 @@ void dotraplinkage do_emulate_vsyscall(struct pt_regs *regs, long error_code)
 	 * and int 0xcc is two bytes long.
 	 */
 	vsyscall_nr = addr_to_vsyscall_nr(regs->ip - 2);
+
+	trace_emulate_vsyscall(vsyscall_nr);
+
 	if (vsyscall_nr < 0) {
 		warn_bad_vsyscall(KERN_WARNING, regs,
 				  "illegal int 0xcc (exploit attempt?)");

arch/x86/kernel/vsyscall_trace.h

@@ -0,0 +1,29 @@
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM vsyscall
+
+#if !defined(__VSYSCALL_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define __VSYSCALL_TRACE_H
+
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(emulate_vsyscall,
+
+	    TP_PROTO(int nr),
+
+	    TP_ARGS(nr),
+
+	    TP_STRUCT__entry(__field(int, nr)),
+
+	    TP_fast_assign(
+			   __entry->nr = nr;
+			   ),
+
+	    TP_printk("nr = %d", __entry->nr)
+);
+
+#endif
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH ../../arch/x86/kernel
+#define TRACE_INCLUDE_FILE vsyscall_trace
+#include <trace/define_trace.h>