ftrace: add self-tests

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/trace/Kconfig

@@ -105,3 +105,16 @@ config DYNAMIC_FTRACE
 	 wakes up once a second and checks to see if any ftrace calls
 	 were made. If so, it runs stop_machine (stops all CPUS)
 	 and modifies the code to jump over the call to ftrace.
+
+config FTRACE_SELFTEST
+	bool
+
+config FTRACE_STARTUP_TEST
+	bool "Perform a startup test on ftrace"
+	depends on TRACING
+	select FTRACE_SELFTEST
+	help
+	  This option performs a series of startup tests on ftrace. On bootup
+	  a series of tests are made to verify that the tracer is
+	  functioning properly. It will do tests on all the configured
+	  tracers of ftrace.

kernel/trace/trace.c

@@ -32,6 +32,8 @@
 unsigned long __read_mostly	tracing_max_latency = (cycle_t)ULONG_MAX;
 unsigned long __read_mostly	tracing_thresh;
 
+static int tracing_disabled = 1;
+
 static long notrace
 ns2usecs(cycle_t nsec)
 {
@@ -217,11 +219,48 @@ int register_tracer(struct tracer *type)
 		}
 	}
 
+#ifdef CONFIG_FTRACE_STARTUP_TEST
+	if (type->selftest) {
+		struct tracer *saved_tracer = current_trace;
+		struct trace_array_cpu *data;
+		struct trace_array *tr = &global_trace;
+		int saved_ctrl = tr->ctrl;
+		int i;
+		/*
+		 * Run a selftest on this tracer.
+		 * Here we reset the trace buffer, and set the current
+		 * tracer to be this tracer. The tracer can then run some
+		 * internal tracing to verify that everything is in order.
+		 * If we fail, we do not register this tracer.
+		 */
+		for_each_possible_cpu(i) {
+			if (!data->trace)
+				continue;
+			data = tr->data[i];
+			tracing_reset(data);
+		}
+		current_trace = type;
+		tr->ctrl = 0;
+		/* the test is responsible for initializing and enabling */
+		pr_info("Testing tracer %s: ", type->name);
+		ret = type->selftest(type, tr);
+		/* the test is responsible for resetting too */
+		current_trace = saved_tracer;
+		tr->ctrl = saved_ctrl;
+		if (ret) {
+			printk(KERN_CONT "FAILED!\n");
+			goto out;
+		}
+		printk(KERN_CONT "PASSED\n");
+	}
+#endif
+
 	type->next = trace_types;
 	trace_types = type;
 	len = strlen(type->name);
 	if (len > max_tracer_type_len)
 		max_tracer_type_len = len;
+
  out:
 	mutex_unlock(&trace_types_lock);
 
@@ -985,6 +1024,11 @@ __tracing_open(struct inode *inode, struct file *file, int *ret)
 {
 	struct trace_iterator *iter;
 
+	if (tracing_disabled) {
+		*ret = -ENODEV;
+		return NULL;
+	}
+
 	iter = kzalloc(sizeof(*iter), GFP_KERNEL);
 	if (!iter) {
 		*ret = -ENOMEM;
@@ -1023,6 +1067,9 @@ __tracing_open(struct inode *inode, struct file *file, int *ret)
 
 int tracing_open_generic(struct inode *inode, struct file *filp)
 {
+	if (tracing_disabled)
+		return -ENODEV;
+
 	filp->private_data = inode->i_private;
 	return 0;
 }
@@ -1128,6 +1175,9 @@ static int show_traces_open(struct inode *inode, struct file *file)
 {
 	int ret;
 
+	if (tracing_disabled)
+		return -ENODEV;
+
 	ret = seq_open(file, &show_traces_seq_ops);
 	if (!ret) {
 		struct seq_file *m = file->private_data;
@@ -1452,6 +1502,11 @@ struct dentry *tracing_init_dentry(void)
 	return d_tracer;
 }
 
+#ifdef CONFIG_FTRACE_SELFTEST
+/* Let selftest have access to static functions in this file */
+#include "trace_selftest.c"
+#endif
+
 static __init void tracer_init_debugfs(void)
 {
 	struct dentry *d_tracer;
@@ -1585,6 +1640,7 @@ __init static int tracer_alloc_buffers(void)
 	void *array;
 	struct page *page;
 	int pages = 0;
+	int ret = -ENOMEM;
 	int i;
 
 	/* Allocate the first page for all buffers */
@@ -1650,6 +1706,9 @@ __init static int tracer_alloc_buffers(void)
 	register_tracer(&no_tracer);
 	current_trace = &no_tracer;
 
+	/* All seems OK, enable tracing */
+	tracing_disabled = 0;
+
 	return 0;
 
  free_buffers:
@@ -1678,7 +1737,7 @@ __init static int tracer_alloc_buffers(void)
 		}
 #endif
 	}
-	return -ENOMEM;
+	return ret;
 }
 
-device_initcall(tracer_alloc_buffers);
+fs_initcall(tracer_alloc_buffers);

kernel/trace/trace.h

@@ -99,6 +99,10 @@ struct tracer {
 	void			(*start)(struct trace_iterator *iter);
 	void			(*stop)(struct trace_iterator *iter);
 	void			(*ctrl_update)(struct trace_array *tr);
+#ifdef CONFIG_FTRACE_STARTUP_TEST
+	int			(*selftest)(struct tracer *trace,
+					    struct trace_array *tr);
+#endif
 	struct tracer		*next;
 	int			print_max;
 };
@@ -185,4 +189,31 @@ extern int unregister_tracer_switch(struct tracer_switch_ops *ops);
 extern unsigned long ftrace_update_tot_cnt;
 #endif
 
+#ifdef CONFIG_FTRACE_STARTUP_TEST
+#ifdef CONFIG_FTRACE
+extern int trace_selftest_startup_function(struct tracer *trace,
+					   struct trace_array *tr);
+#endif
+#ifdef CONFIG_IRQSOFF_TRACER
+extern int trace_selftest_startup_irqsoff(struct tracer *trace,
+					  struct trace_array *tr);
+#endif
+#ifdef CONFIG_PREEMPT_TRACER
+extern int trace_selftest_startup_preemptoff(struct tracer *trace,
+					     struct trace_array *tr);
+#endif
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+extern int trace_selftest_startup_preemptirqsoff(struct tracer *trace,
+						 struct trace_array *tr);
+#endif
+#ifdef CONFIG_SCHED_TRACER
+extern int trace_selftest_startup_wakeup(struct tracer *trace,
+					 struct trace_array *tr);
+#endif
+#ifdef CONFIG_CONTEXT_SWITCH_TRACER
+extern int trace_selftest_startup_sched_switch(struct tracer *trace,
+					       struct trace_array *tr);
+#endif
+#endif /* CONFIG_FTRACE_STARTUP_TEST */
+
 #endif /* _LINUX_KERNEL_TRACE_H */

kernel/trace/trace_functions.c

@@ -63,6 +63,9 @@ static struct tracer function_trace __read_mostly =
 	.init	     = function_trace_init,
 	.reset	     = function_trace_reset,
 	.ctrl_update = function_trace_ctrl_update,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_function,
+#endif
 };
 
 static __init int init_function_trace(void)

kernel/trace/trace_irqsoff.c

@@ -432,6 +432,9 @@ static struct tracer irqsoff_tracer __read_mostly =
 	.close		= irqsoff_tracer_close,
 	.ctrl_update	= irqsoff_tracer_ctrl_update,
 	.print_max	= 1,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_irqsoff,
+#endif
 };
 # define register_irqsoff(trace) register_tracer(&trace)
 #else
@@ -455,6 +458,9 @@ static struct tracer preemptoff_tracer __read_mostly =
 	.close		= irqsoff_tracer_close,
 	.ctrl_update	= irqsoff_tracer_ctrl_update,
 	.print_max	= 1,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_preemptoff,
+#endif
 };
 # define register_preemptoff(trace) register_tracer(&trace)
 #else
@@ -480,6 +486,9 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 	.close		= irqsoff_tracer_close,
 	.ctrl_update	= irqsoff_tracer_ctrl_update,
 	.print_max	= 1,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_preemptirqsoff,
+#endif
 };
 
 # define register_preemptirqsoff(trace) register_tracer(&trace)

kernel/trace/trace_sched_switch.c

@@ -107,6 +107,9 @@ static struct tracer sched_switch_trace __read_mostly =
 	.init		= sched_switch_trace_init,
 	.reset		= sched_switch_trace_reset,
 	.ctrl_update	= sched_switch_trace_ctrl_update,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_sched_switch,
+#endif
 };
 
 __init static int init_sched_switch_trace(void)

kernel/trace/trace_sched_wakeup.c

@@ -295,6 +295,9 @@ static struct tracer wakeup_tracer __read_mostly =
 	.close		= wakeup_tracer_close,
 	.ctrl_update	= wakeup_tracer_ctrl_update,
 	.print_max	= 1,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest    = trace_selftest_startup_wakeup,
+#endif
 };
 
 __init static int init_wakeup_tracer(void)

kernel/trace/trace_selftest.c

+/* Include in trace.c */
+
+#include <linux/kthread.h>
+
+static inline int trace_valid_entry(struct trace_entry *entry)
+{
+	switch (entry->type) {
+	case TRACE_FN:
+	case TRACE_CTX:
+		return 1;
+	}
+	return 0;
+}
+
+static int
+trace_test_buffer_cpu(struct trace_array *tr, struct trace_array_cpu *data)
+{
+	struct page *page;
+	struct trace_entry *entries;
+	int idx = 0;
+	int i;
+
+	page = list_entry(data->trace_pages.next, struct page, lru);
+	entries = page_address(page);
+
+	if (data->trace != entries)
+		goto failed;
+
+	/*
+	 * The starting trace buffer always has valid elements,
+	 * if any element exits.
+	 */
+	entries = data->trace;
+
+	for (i = 0; i < tr->entries; i++) {
+
+		if (i < data->trace_idx &&
+		    !trace_valid_entry(&entries[idx])) {
+			printk(KERN_CONT ".. invalid entry %d ", entries[idx].type);
+			goto failed;
+		}
+
+		idx++;
+		if (idx >= ENTRIES_PER_PAGE) {
+			page = virt_to_page(entries);
+			if (page->lru.next == &data->trace_pages) {
+				if (i != tr->entries - 1) {
+					printk(KERN_CONT ".. entries buffer mismatch");
+					goto failed;
+				}
+			} else {
+				page = list_entry(page->lru.next, struct page, lru);
+				entries = page_address(page);
+			}
+			idx = 0;
+		}
+	}
+
+	page = virt_to_page(entries);
+	if (page->lru.next != &data->trace_pages) {
+		printk(KERN_CONT ".. too many entries");
+		goto failed;
+	}
+
+	return 0;
+
+ failed:
+	printk(KERN_CONT ".. corrupted trace buffer .. ");
+	return -1;
+}
+
+/*
+ * Test the trace buffer to see if all the elements
+ * are still sane.
+ */
+static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
+{
+	unsigned long cnt = 0;
+	int cpu;
+	int ret = 0;
+
+	for_each_possible_cpu(cpu) {
+		if (!tr->data[cpu]->trace)
+			continue;
+
+		cnt += tr->data[cpu]->trace_idx;
+		printk("%d: count = %ld\n", cpu, cnt);
+
+		ret = trace_test_buffer_cpu(tr, tr->data[cpu]);
+		if (ret)
+			break;
+	}
+
+	if (count)
+		*count = cnt;
+
+	return ret;
+}
+
+#ifdef CONFIG_FTRACE
+/*
+ * Simple verification test of ftrace function tracer.
+ * Enable ftrace, sleep 1/10 second, and then read the trace
+ * buffer to see if all is in order.
+ */
+int
+trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long count;
+	int ret;
+
+	/* make sure functions have been recorded */
+	ret = ftrace_force_update();
+	if (ret) {
+		printk(KERN_CONT ".. ftraced failed .. ");
+		return ret;
+	}
+
+	/* start the tracing */
+	tr->ctrl = 1;
+	trace->init(tr);
+	/* Sleep for a 1/10 of a second */
+	msleep(100);
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check the trace buffer */
+	ret = trace_test_buffer(tr, &count);
+	trace->reset(tr);
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+	}
+
+	return ret;
+}
+#endif /* CONFIG_FTRACE */
+
+#ifdef CONFIG_IRQSOFF_TRACER
+int
+trace_selftest_startup_irqsoff(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long save_max = tracing_max_latency;
+	unsigned long count;
+	int ret;
+
+	/* start the tracing */
+	tr->ctrl = 1;
+	trace->init(tr);
+	/* reset the max latency */
+	tracing_max_latency = 0;
+	/* disable interrupts for a bit */
+	local_irq_disable();
+	udelay(100);
+	local_irq_enable();
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check both trace buffers */
+	ret = trace_test_buffer(tr, NULL);
+	if (!ret)
+		ret = trace_test_buffer(&max_tr, &count);
+	trace->reset(tr);
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+	}
+
+	tracing_max_latency = save_max;
+
+	return ret;
+}
+#endif /* CONFIG_IRQSOFF_TRACER */
+
+#ifdef CONFIG_PREEMPT_TRACER
+int
+trace_selftest_startup_preemptoff(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long save_max = tracing_max_latency;
+	unsigned long count;
+	int ret;
+
+	/* start the tracing */
+	tr->ctrl = 1;
+	trace->init(tr);
+	/* reset the max latency */
+	tracing_max_latency = 0;
+	/* disable preemption for a bit */
+	preempt_disable();
+	udelay(100);
+	preempt_enable();
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check both trace buffers */
+	ret = trace_test_buffer(tr, NULL);
+	if (!ret)
+		ret = trace_test_buffer(&max_tr, &count);
+	trace->reset(tr);
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+	}
+
+	tracing_max_latency = save_max;
+
+	return ret;
+}
+#endif /* CONFIG_PREEMPT_TRACER */
+
+#if defined(CONFIG_IRQSOFF_TRACER) && defined(CONFIG_PREEMPT_TRACER)
+int
+trace_selftest_startup_preemptirqsoff(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long save_max = tracing_max_latency;
+	unsigned long count;
+	int ret;
+
+	/* start the tracing */
+	tr->ctrl = 1;
+	trace->init(tr);
+
+	/* reset the max latency */
+	tracing_max_latency = 0;
+
+	/* disable preemption and interrupts for a bit */
+	preempt_disable();
+	local_irq_disable();
+	udelay(100);
+	preempt_enable();
+	/* reverse the order of preempt vs irqs */
+	local_irq_enable();
+
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check both trace buffers */
+	ret = trace_test_buffer(tr, NULL);
+	if (ret)
+		goto out;
+
+	ret = trace_test_buffer(&max_tr, &count);
+	if (ret)
+		goto out;
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+		goto out;
+	}
+
+	/* do the test by disabling interrupts first this time */
+	tracing_max_latency = 0;
+	tr->ctrl = 1;
+	trace->ctrl_update(tr);
+	preempt_disable();
+	local_irq_disable();
+	udelay(100);
+	preempt_enable();
+	/* reverse the order of preempt vs irqs */
+	local_irq_enable();
+
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check both trace buffers */
+	ret = trace_test_buffer(tr, NULL);
+	if (ret)
+		goto out;
+
+	ret = trace_test_buffer(&max_tr, &count);
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+		goto out;
+	}
+
+ out:
+	trace->reset(tr);
+	tracing_max_latency = save_max;
+
+	return ret;
+}
+#endif /* CONFIG_IRQSOFF_TRACER && CONFIG_PREEMPT_TRACER */
+
+#ifdef CONFIG_SCHED_TRACER
+static int trace_wakeup_test_thread(void *data)
+{
+	struct completion *x = data;
+
+	/* Make this a RT thread, doesn't need to be too high */
+
+	rt_mutex_setprio(current, MAX_RT_PRIO - 5);
+
+	/* Make it know we have a new prio */
+	complete(x);
+
+	/* now go to sleep and let the test wake us up */
+	set_current_state(TASK_INTERRUPTIBLE);
+	schedule();
+
+	/* we are awake, now wait to disappear */
+	while (!kthread_should_stop()) {
+		/*
+		 * This is an RT task, do short sleeps to let
+		 * others run.
+		 */
+		msleep(100);
+	}
+
+	return 0;
+}
+
+int
+trace_selftest_startup_wakeup(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long save_max = tracing_max_latency;
+	struct task_struct *p;
+	struct completion isrt;
+	unsigned long count;
+	int ret;
+
+	init_completion(&isrt);
+
+	/* create a high prio thread */
+	p = kthread_run(trace_wakeup_test_thread, &isrt, "ftrace-test");
+	if (!IS_ERR(p)) {
+		printk(KERN_CONT "Failed to create ftrace wakeup test thread ");
+		return -1;
+	}
+
+	/* make sure the thread is running at an RT prio */
+	wait_for_completion(&isrt);
+
+	/* start the tracing */
+	tr->ctrl = 1;
+	trace->init(tr);
+	/* reset the max latency */
+	tracing_max_latency = 0;
+
+	/* sleep to let the RT thread sleep too */
+	msleep(100);
+
+	/*
+	 * Yes this is slightly racy. It is possible that for some
+	 * strange reason that the RT thread we created, did not
+	 * call schedule for 100ms after doing the completion,
+	 * and we do a wakeup on a task that already is awake.
+	 * But that is extremely unlikely, and the worst thing that
+	 * happens in such a case, is that we disable tracing.
+	 * Honestly, if this race does happen something is horrible
+	 * wrong with the system.
+	 */
+
+	wake_up_process(p);
+
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check both trace buffers */
+	ret = trace_test_buffer(tr, NULL);
+	if (!ret)
+		ret = trace_test_buffer(&max_tr, &count);
+
+
+	trace->reset(tr);
+
+	tracing_max_latency = save_max;
+
+	/* kill the thread */
+	kthread_stop(p);
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+	}
+
+	return ret;
+}
+#endif /* CONFIG_SCHED_TRACER */
+
+#ifdef CONFIG_CONTEXT_SWITCH_TRACER
+int
+trace_selftest_startup_sched_switch(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long count;
+	int ret;
+
+	/* start the tracing */
+	tr->ctrl = 1;
+	trace->init(tr);
+	/* Sleep for a 1/10 of a second */
+	msleep(100);
+	/* stop the tracing. */
+	tr->ctrl = 0;
+	trace->ctrl_update(tr);
+	/* check the trace buffer */
+	ret = trace_test_buffer(tr, &count);
+	trace->reset(tr);
+
+	if (!ret && !count) {
+		printk(KERN_CONT ".. no entries found ..");
+		ret = -1;
+	}
+
+	return ret;
+}
+#endif /* CONFIG_CONTEXT_SWITCH_TRACER */
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+#endif /* CONFIG_DYNAMIC_FTRACE */