tools lib traceevent: Copy trace_clock and free it

The pevent->trace_clock should not be a direct pointer to what was
given. It should be copied and freed.

Note, valgrind pointed this out when a caller passed in a pointer that
needed to be freed and it never was. Ideally, pevent should copy it
(which this change does), and free the copy. It's up to the caller to
free the clock string passed in.

Signed-off-by: Steven Rostedt <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/lib/traceevent/event-parse.c

···
 	return 0;
 }
 
-void pevent_register_trace_clock(struct pevent *pevent, char *trace_clock)
+int pevent_register_trace_clock(struct pevent *pevent, const char *trace_clock)
 {
-	pevent->trace_clock = trace_clock;
+	pevent->trace_clock = strdup(trace_clock);
+	if (!pevent->trace_clock) {
+		errno = ENOMEM;
+		return -1;
+	}
+	return 0;
 }
 
 struct func_map {
···
 		free_handler(handle);
 	}
 
+	free(pevent->trace_clock);
 	free(pevent->events);
 	free(pevent->sort_events);
 

tools/lib/traceevent/event-parse.h

···
 };
 
 int pevent_register_comm(struct pevent *pevent, const char *comm, int pid);
-void pevent_register_trace_clock(struct pevent *pevent, char *trace_clock);
+int pevent_register_trace_clock(struct pevent *pevent, const char *trace_clock);
 int pevent_register_function(struct pevent *pevent, char *name,
 			     unsigned long long addr, char *mod);
 int pevent_register_print_string(struct pevent *pevent, const char *fmt,