tracing: tracepoints, samples

Tracepoint example code under samples/.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: 'Peter Zijlstra' <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

samples/Kconfig

@@ -13,6 +13,12 @@ config SAMPLE_MARKERS
 	help
 	  This build markers example modules.
 
+config SAMPLE_TRACEPOINTS
+	tristate "Build tracepoints examples -- loadable modules only"
+	depends on TRACEPOINTS && m
+	help
+	  This build tracepoints example modules.
+
 config SAMPLE_KOBJECT
 	tristate "Build kobject examples"
 	help

samples/Makefile

 # Makefile for Linux samples code
 
-obj-$(CONFIG_SAMPLES)	+= markers/ kobject/ kprobes/
+obj-$(CONFIG_SAMPLES)	+= markers/ kobject/ kprobes/ tracepoints/

samples/tracepoints/Makefile

+# builds the tracepoint example kernel modules;
+# then to use one (as root):  insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_TRACEPOINTS) += tracepoint-sample.o
+obj-$(CONFIG_SAMPLE_TRACEPOINTS) += tracepoint-probe-sample.o
+obj-$(CONFIG_SAMPLE_TRACEPOINTS) += tracepoint-probe-sample2.o

samples/tracepoints/tp-samples-trace.h

+#ifndef _TP_SAMPLES_TRACE_H
+#define _TP_SAMPLES_TRACE_H
+
+#include <linux/proc_fs.h>	/* for struct inode and struct file */
+#include <linux/tracepoint.h>
+
+DEFINE_TRACE(subsys_event,
+	TPPROTO(struct inode *inode, struct file *file),
+	TPARGS(inode, file));
+DEFINE_TRACE(subsys_eventb,
+	TPPROTO(void),
+	TPARGS());
+#endif

samples/tracepoints/tracepoint-probe-sample.c

+/*
+ * tracepoint-probe-sample.c
+ *
+ * sample tracepoint probes.
+ */
+
+#include <linux/module.h>
+#include <linux/file.h>
+#include <linux/dcache.h>
+#include "tp-samples-trace.h"
+
+/*
+ * Here the caller only guarantees locking for struct file and struct inode.
+ * Locking must therefore be done in the probe to use the dentry.
+ */
+static void probe_subsys_event(struct inode *inode, struct file *file)
+{
+	path_get(&file->f_path);
+	dget(file->f_path.dentry);
+	printk(KERN_INFO "Event is encountered with filename %s\n",
+		file->f_path.dentry->d_name.name);
+	dput(file->f_path.dentry);
+	path_put(&file->f_path);
+}
+
+static void probe_subsys_eventb(void)
+{
+	printk(KERN_INFO "Event B is encountered\n");
+}
+
+int __init tp_sample_trace_init(void)
+{
+	int ret;
+
+	ret = register_trace_subsys_event(probe_subsys_event);
+	WARN_ON(ret);
+	ret = register_trace_subsys_eventb(probe_subsys_eventb);
+	WARN_ON(ret);
+
+	return 0;
+}
+
+module_init(tp_sample_trace_init);
+
+void __exit tp_sample_trace_exit(void)
+{
+	unregister_trace_subsys_eventb(probe_subsys_eventb);
+	unregister_trace_subsys_event(probe_subsys_event);
+}
+
+module_exit(tp_sample_trace_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Tracepoint Probes Samples");

samples/tracepoints/tracepoint-probe-sample2.c

+/*
+ * tracepoint-probe-sample2.c
+ *
+ * 2nd sample tracepoint probes.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include "tp-samples-trace.h"
+
+/*
+ * Here the caller only guarantees locking for struct file and struct inode.
+ * Locking must therefore be done in the probe to use the dentry.
+ */
+static void probe_subsys_event(struct inode *inode, struct file *file)
+{
+	printk(KERN_INFO "Event is encountered with inode number %lu\n",
+		inode->i_ino);
+}
+
+int __init tp_sample_trace_init(void)
+{
+	int ret;
+
+	ret = register_trace_subsys_event(probe_subsys_event);
+	WARN_ON(ret);
+
+	return 0;
+}
+
+module_init(tp_sample_trace_init);
+
+void __exit tp_sample_trace_exit(void)
+{
+	unregister_trace_subsys_event(probe_subsys_event);
+}
+
+module_exit(tp_sample_trace_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Tracepoint Probes Samples");

samples/tracepoints/tracepoint-sample.c

+/* tracepoint-sample.c
+ *
+ * Executes a tracepoint when /proc/tracepoint-example is opened.
+ *
+ * (C) Copyright 2007 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/proc_fs.h>
+#include "tp-samples-trace.h"
+
+struct proc_dir_entry *pentry_example;
+
+static int my_open(struct inode *inode, struct file *file)
+{
+	int i;
+
+	trace_subsys_event(inode, file);
+	for (i = 0; i < 10; i++)
+		trace_subsys_eventb();
+	return -EPERM;
+}
+
+static struct file_operations mark_ops = {
+	.open = my_open,
+};
+
+static int example_init(void)
+{
+	printk(KERN_ALERT "example init\n");
+	pentry_example = proc_create("tracepoint-example", 0444, NULL,
+		&mark_ops);
+	if (!pentry_example)
+		return -EPERM;
+	return 0;
+}
+
+static void example_exit(void)
+{
+	printk(KERN_ALERT "example exit\n");
+	remove_proc_entry("tracepoint-example", NULL);
+}
+
+module_init(example_init)
+module_exit(example_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Tracepoint example");