tools lib traceevent: Add offset option for function plugin

When the offset option is set for the function plugin enabled, it will
display the offset of the functions along with their names.  This helps
in finding exactly where a function was called by its parent.

  trace-cmd report -O parent -O offset
 [..]
        rcuc/163-1330  [163]   740.653251: function: _raw_spin_lock+0x0  <-- rcu_cpu_kthread+0x4d8

Link: http://lore.kernel.org/linux-trace-devel/20200702174950.123454-2-tz.stoyanov@gmail.comSigned-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[ Ported from trace-cmd.git ]
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200702185704.986181512@goodmis.orgSigned-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/plugins/plugin_function.c

@@ -49,6 +49,13 @@ struct tep_plugin_option plugin_options[] =
 		"Try to show function call indents, based on parents",
 		.set = 1,
 	},
+	{
+		.name = "offset",
+		.plugin_alias = "ftrace",
+		.description =
+		"Show function names as well as their offsets",
+		.set = 0,
+	},
 	{
 		.name = NULL,
 	}
@@ -56,6 +63,7 @@ struct tep_plugin_option plugin_options[] =
 
 static struct tep_plugin_option *ftrace_parent = &plugin_options[0];
 static struct tep_plugin_option *ftrace_indent = &plugin_options[1];
+static struct tep_plugin_option *ftrace_offset = &plugin_options[2];
 
 static void add_child(struct func_stack *stack, const char *child, int pos)
 {
@@ -123,6 +131,18 @@ static int add_and_get_index(const char *parent, const char *child, int cpu)
 	return 0;
 }
 
+static void show_function(struct trace_seq *s, struct tep_handle *tep,
+			  const char *func, unsigned long long function)
+{
+	unsigned long long offset;
+
+	trace_seq_printf(s, "%s", func);
+	if (ftrace_offset->set) {
+		offset = tep_find_function_address(tep, function);
+		trace_seq_printf(s, "+0x%x ", (int)(function - offset));
+	}
+}
+
 static int function_handler(struct trace_seq *s, struct tep_record *record,
 			    struct tep_event *event, void *context)
 {
@@ -149,14 +169,14 @@ static int function_handler(struct trace_seq *s, struct tep_record *record,
 	trace_seq_printf(s, "%*s", index*3, "");
 
 	if (func)
-		trace_seq_printf(s, "%s", func);
+		show_function(s, tep, func, function);
 	else
 		trace_seq_printf(s, "0x%llx", function);
 
 	if (ftrace_parent->set) {
 		trace_seq_printf(s, " <-- ");
 		if (parent)
-			trace_seq_printf(s, "%s", parent);
+			show_function(s, tep, parent, pfunction);
 		else
 			trace_seq_printf(s, "0x%llx", pfunction);
 	}