samples/trace_event: Add '__rel_loc' using sample event

Add '__rel_loc' using sample event for testing.
User can use this for testing purpose. There is
no reason to use this macro from the kernel.

Link: https://lkml.kernel.org/r/163757343050.510314.2876529802471645178.stgit@devnote2

Cc: Beau Belgrave <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Tom Zanussi <[e-mail]>
Signed-off-by: Masami Hiramatsu <[e-mail]>
Signed-off-by: Steven Rostedt (VMware) <[e-mail]>

samples/trace_events/trace-events-sample.c

···
 
 static void simple_thread_func(int cnt)
 {
+	unsigned long bitmask[1] = {0xdeadbeefUL};
 	int array[6];
 	int len = cnt % 5;
 	int i;
···
 	trace_foo_with_template_cond("prints other times", cnt);
 
 	trace_foo_with_template_print("I have to be different", cnt);
+
+	trace_foo_rel_loc("Hello __rel_loc", cnt, bitmask);
 }
 
 static int simple_thread(void *arg)

samples/trace_events/trace-events-sample.h

···
 	TP_ARGS(foo, bar),
 	TP_printk("bar %s %d", __get_str(foo), __entry->bar));
 
+/*
+ * There are yet another __rel_loc dynamic data attribute. If you
+ * use __rel_dynamic_array() and __rel_string() etc. macros, you
+ * can use this attribute. There is no difference from the viewpoint
+ * of functionality with/without 'rel' but the encoding is a bit
+ * different. This is expected to be used with user-space event,
+ * there is no reason that the kernel event use this, but only for
+ * testing.
+ */
+
+TRACE_EVENT(foo_rel_loc,
+
+	TP_PROTO(const char *foo, int bar, unsigned long *mask),
+
+	TP_ARGS(foo, bar, mask),
+
+	TP_STRUCT__entry(
+		__rel_string(	foo,	foo	)
+		__field(	int,	bar	)
+		__rel_bitmask(	bitmask,
+			BITS_PER_BYTE * sizeof(unsigned long)	)
+	),
+
+	TP_fast_assign(
+		__assign_rel_str(foo, foo);
+		__entry->bar = bar;
+		__assign_rel_bitmask(bitmask, mask,
+			BITS_PER_BYTE * sizeof(unsigned long));
+	),
+
+	TP_printk("foo_rel_loc %s, %d, %s", __get_rel_str(foo), __entry->bar,
+		  __get_rel_bitmask(bitmask))
+);
 #endif
 
 /***** NOTICE! The #if protection ends here. *****/