tracing/function-graph-tracer: provide a selftest for the function graph tracer

Making it more easy to do a basic regression test for this tracer.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.h

@@ -500,6 +500,8 @@ extern int DYN_FTRACE_TEST_NAME(void);
 #ifdef CONFIG_FTRACE_STARTUP_TEST
 extern int trace_selftest_startup_function(struct tracer *trace,
 					   struct trace_array *tr);
+extern int trace_selftest_startup_function_graph(struct tracer *trace,
+						 struct trace_array *tr);
 extern int trace_selftest_startup_irqsoff(struct tracer *trace,
 					  struct trace_array *tr);
 extern int trace_selftest_startup_preemptoff(struct tracer *trace,

kernel/trace/trace_functions_graph.c

@@ -750,6 +750,9 @@ static struct tracer graph_trace __read_mostly = {
 	.print_line	= print_graph_function,
 	.print_header	= print_graph_headers,
 	.flags		= &tracer_flags,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest	= trace_selftest_startup_function_graph,
+#endif
 };
 
 static __init int init_graph_trace(void)

kernel/trace/trace_selftest.c

@@ -13,6 +13,8 @@ static inline int trace_valid_entry(struct trace_entry *entry)
 	case TRACE_PRINT:
 	case TRACE_SPECIAL:
 	case TRACE_BRANCH:
+	case TRACE_GRAPH_ENT:
+	case TRACE_GRAPH_RET:
 		return 1;
 	}
 	return 0;
@@ -227,6 +229,54 @@ trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
 }
 #endif /* CONFIG_FUNCTION_TRACER */
 
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * Pretty much the same than for the function tracer from which the selftest
+ * has been borrowed.
+ */
+int
+trace_selftest_startup_function_graph(struct tracer *trace,
+					struct trace_array *tr)
+{
+	int ret;
+	unsigned long count;
+
+	ret = tracer_init(trace, tr);
+	if (ret) {
+		warn_failed_init_tracer(trace, ret);
+		goto out;
+	}
+
+	/* Sleep for a 1/10 of a second */
+	msleep(100);
+
+	tracing_stop();
+
+	/* check the trace buffer */
+	ret = trace_test_buffer(tr, &count);
+
+	trace->reset(tr);
+	tracing_start();
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+		goto out;
+	}
+
+	/* Don't test dynamic tracing, the function tracer already did */
+
+out:
+	/* Stop it if we failed */
+	if (ret)
+		ftrace_graph_stop();
+
+	return ret;
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+
 #ifdef CONFIG_IRQSOFF_TRACER
 int
 trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)