Linux Kernel Markers - Samples

Module example showing how to use the Linux Kernel Markers.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

6 files changed, 164 insertions, 1 deletions

diff --git a/include/linux/marker.h b/include/linux/marker.h
index 8038d89b835d..5f36cf946bcb 100644
--- a/include/linux/marker.h
+++ b/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();                              \
diff --git a/samples/Kconfig b/samples/Kconfig
index b46b4cf4382f..57bb2236952c 100644
--- a/samples/Kconfig
+++ b/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
diff --git a/samples/Makefile b/samples/Makefile
new file mode 100644
index 000000000000..5a4f0b6bcbed
--- /dev/null
+++ b/samples/Makefile
@@ -0,0 +1,3 @@
+# Makefile for Linux samples code
+
+obj-$(CONFIG_SAMPLES)   += markers/
diff --git a/samples/markers/Makefile b/samples/markers/Makefile
new file mode 100644
index 000000000000..6d7231265f0f
--- /dev/null
+++ b/samples/markers/Makefile
@@ -0,0 +1,4 @@
+# builds the kprobes example kernel modules;
+# then to use one (as root):  insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_MARKERS) += probe-example.o marker-example.o
diff --git a/samples/markers/marker-example.c b/samples/markers/marker-example.c
new file mode 100644
index 000000000000..e787c6d16dd7
--- /dev/null
+++ b/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 <mathieu.desnoyers@polymtl.ca>
+ *
+ * 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");
diff --git a/samples/markers/probe-example.c b/samples/markers/probe-example.c
new file mode 100644
index 000000000000..238b2e384fc8
--- /dev/null
+++ b/samples/markers/probe-example.c
@@ -0,0 +1,98 @@
+/* probe-example.c
+ *
+ * Connects two functions to marker call sites.
+ *
+ * (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/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");