tracing: Add perf counter support for syscalls tracing

The perf counter support is automated for usual trace events. But we
have to define specific callbacks for this to handle syscalls trace
events

Make 'perf stat -e syscalls:sys_enter_blah' work with syscall style
tracepoints.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index df62840..3ab6dd1 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h
@@ -58,5 +58,12 @@
 enum print_line_t print_syscall_enter(struct trace_iterator *iter, int flags);
 enum print_line_t print_syscall_exit(struct trace_iterator *iter, int flags);
 #endif
+#ifdef CONFIG_EVENT_PROFILE
+int reg_prof_syscall_enter(char *name);
+void unreg_prof_syscall_enter(char *name);
+int reg_prof_syscall_exit(char *name);
+void unreg_prof_syscall_exit(char *name);
+
+#endif
 
 #endif /* _TRACE_SYSCALL_H */