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Linux Kernel Markers - Samples
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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]>
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Mathieu Desnoyers authored and Linus Torvalds committed Oct 19, 2007
1 parent 267c402 commit 31155bc
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Showing 6 changed files with 164 additions and 1 deletion.
1 change: 0 additions & 1 deletion include/linux/marker.h
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Expand Up @@ -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(); \
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5 changes: 5 additions & 0 deletions samples/Kconfig
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Expand Up @@ -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
3 changes: 3 additions & 0 deletions samples/Makefile
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@@ -0,0 +1,3 @@
# Makefile for Linux samples code

obj-$(CONFIG_SAMPLES) += markers/
4 changes: 4 additions & 0 deletions samples/markers/Makefile
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@@ -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
54 changes: 54 additions & 0 deletions samples/markers/marker-example.c
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@@ -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");
98 changes: 98 additions & 0 deletions samples/markers/probe-example.c
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@@ -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");

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