Linux Kernel Markers - Samples

Module example showing how to use the Linux Kernel Markers.

[[email protected]: coding-style fixes]
Signed-off-by: Mathieu Desnoyers <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/marker.h

@@ -61,7 +61,6 @@ struct marker {
 		__attribute__((section("__markers"), aligned(8))) =	\
 		{ __mstrtab_name_##name, __mstrtab_format_##name,	\
 		0, __mark_empty_function, NULL };			\
-		asm volatile("" : : "i" (&__mark_##name));		\
 		__mark_check_format(format, ## args);			\
 		if (unlikely(__mark_##name.state)) {			\
 			preempt_disable();				\

samples/Kconfig

@@ -7,5 +7,10 @@ menuconfig SAMPLES
 
 if SAMPLES
 
+config SAMPLE_MARKERS
+	tristate "Build markers examples -- loadable modules only"
+	depends on MARKERS && m
+	help
+	  This build markers example modules.
 
 endif # SAMPLES

samples/Makefile

@@ -0,0 +1,3 @@
+# Makefile for Linux samples code
+
+obj-$(CONFIG_SAMPLES)	+= markers/

samples/markers/Makefile

@@ -0,0 +1,4 @@
+# builds the kprobes example kernel modules;
+# then to use one (as root):  insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_MARKERS) += probe-example.o marker-example.o

samples/markers/marker-example.c

@@ -0,0 +1,54 @@
+/* marker-example.c
+ *
+ * Executes a marker when /proc/marker-example is opened.
+ *
+ * (C) Copyright 2007 Mathieu Desnoyers <[email protected]>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/marker.h>
+#include <linux/sched.h>
+#include <linux/proc_fs.h>
+
+struct proc_dir_entry *pentry_example;
+
+static int my_open(struct inode *inode, struct file *file)
+{
+	int i;
+
+	trace_mark(subsystem_event, "%d %s", 123, "example string");
+	for (i = 0; i < 10; i++)
+		trace_mark(subsystem_eventb, MARK_NOARGS);
+	return -EPERM;
+}
+
+static struct file_operations mark_ops = {
+	.open = my_open,
+};
+
+static int example_init(void)
+{
+	printk(KERN_ALERT "example init\n");
+	pentry_example = create_proc_entry("marker-example", 0444, NULL);
+	if (pentry_example)
+		pentry_example->proc_fops = &mark_ops;
+	else
+		return -EPERM;
+	return 0;
+}
+
+static void example_exit(void)
+{
+	printk(KERN_ALERT "example exit\n");
+	remove_proc_entry("marker-example", NULL);
+}
+
+module_init(example_init)
+module_exit(example_exit)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Marker example");

samples/markers/probe-example.c

@@ -0,0 +1,98 @@
+/* probe-example.c
+ *
+ * Connects two functions to marker call sites.
+ *
+ * (C) Copyright 2007 Mathieu Desnoyers <[email protected]>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/marker.h>
+#include <asm/atomic.h>
+
+struct probe_data {
+	const char *name;
+	const char *format;
+	marker_probe_func *probe_func;
+};
+
+void probe_subsystem_event(const struct marker *mdata, void *private,
+	const char *format, ...)
+{
+	va_list ap;
+	/* Declare args */
+	unsigned int value;
+	const char *mystr;
+
+	/* Assign args */
+	va_start(ap, format);
+	value = va_arg(ap, typeof(value));
+	mystr = va_arg(ap, typeof(mystr));
+
+	/* Call printk */
+	printk(KERN_DEBUG "Value %u, string %s\n", value, mystr);
+
+	/* or count, check rights, serialize data in a buffer */
+
+	va_end(ap);
+}
+
+atomic_t eventb_count = ATOMIC_INIT(0);
+
+void probe_subsystem_eventb(const struct marker *mdata, void *private,
+	const char *format, ...)
+{
+	/* Increment counter */
+	atomic_inc(&eventb_count);
+}
+
+static struct probe_data probe_array[] =
+{
+	{	.name = "subsystem_event",
+		.format = "%d %s",
+		.probe_func = probe_subsystem_event },
+	{	.name = "subsystem_eventb",
+		.format = MARK_NOARGS,
+		.probe_func = probe_subsystem_eventb },
+};
+
+static int __init probe_init(void)
+{
+	int result;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(probe_array); i++) {
+		result = marker_probe_register(probe_array[i].name,
+				probe_array[i].format,
+				probe_array[i].probe_func, &probe_array[i]);
+		if (result)
+			printk(KERN_INFO "Unable to register probe %s\n",
+				probe_array[i].name);
+		result = marker_arm(probe_array[i].name);
+		if (result)
+			printk(KERN_INFO "Unable to arm probe %s\n",
+				probe_array[i].name);
+	}
+	return 0;
+}
+
+static void __exit probe_fini(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(probe_array); i++)
+		marker_probe_unregister(probe_array[i].name);
+	printk(KERN_INFO "Number of event b : %u\n",
+			atomic_read(&eventb_count));
+}
+
+module_init(probe_init);
+module_exit(probe_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("SUBSYSTEM Probe");