tools lib traceevent: Add pevent_print_func_field() helper function

Add the pevent_print_func_field() that will look up a field that is
expected to be a function pointer, and it will print the function name
and offset of the address given by the field.

Signed-off-by: Steven Rostedt <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Frederic Weisbecker <[e-mail]>
Cc: Ingo Molnar <[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 -1;
 }
 
+/**
+ * pevent_print_func_field - print a field and a format for function pointers
+ * @s: The seq to print to
+ * @fmt: The printf format to print the field with.
+ * @event: the event that the field is for
+ * @name: The name of the field
+ * @record: The record with the field name.
+ * @err: print default error if failed.
+ *
+ * Returns: 0 on success, -1 field not found, or 1 if buffer is full.
+ */
+int pevent_print_func_field(struct trace_seq *s, const char *fmt,
+			    struct event_format *event, const char *name,
+			    struct pevent_record *record, int err)
+{
+	struct format_field *field = pevent_find_field(event, name);
+	struct pevent *pevent = event->pevent;
+	unsigned long long val;
+	struct func_map *func;
+	char tmp[128];
+
+	if (!field)
+		goto failed;
+
+	if (pevent_read_number_field(field, record->data, &val))
+		goto failed;
+
+	func = find_func(pevent, val);
+
+	if (func)
+		snprintf(tmp, 128, "%s/0x%llx", func->func, func->addr - val);
+	else
+		sprintf(tmp, "0x%08llx", val);
+
+	return trace_seq_printf(s, fmt, tmp);
+
+ failed:
+	if (err)
+		trace_seq_printf(s, "CAN'T FIND FIELD \"%s\"", name);
+	return -1;
+}
+
 static void free_func_handle(struct pevent_function_handler *func)
 {
 	struct pevent_func_params *params;

tools/lib/traceevent/event-parse.h

···
 			   struct event_format *event, const char *name,
 			   struct pevent_record *record, int err);
 
+int pevent_print_func_field(struct trace_seq *s, const char *fmt,
+			   struct event_format *event, const char *name,
+			   struct pevent_record *record, int err);
+
 int pevent_register_event_handler(struct pevent *pevent, int id,
 				  const char *sys_name, const char *event_name,
 				  pevent_event_handler_func func, void *context);