[GitHub/mt8127/android_kernel_alcatel_ttab.git] / samples / kprobes / kretprobe_example.c

/*
 * kretprobe_example.c
 *
 * Here's a sample kernel module showing the use of return probes to
 * report the return value and total time taken for probed function
 * to run.
 *
 * usage: insmod kretprobe_example.ko func=<func_name>
 *
 * If no func_name is specified, do_fork is instrumented
 *
 * For more information on theory of operation of kretprobes, see
 * Documentation/kprobes.txt
 *
 * Build and insert the kernel module as done in the kprobe example.
 * You will see the trace data in /var/log/messages and on the console
 * whenever the probed function returns. (Some messages may be suppressed
 * if syslogd is configured to eliminate duplicate messages.)
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kprobes.h>
#include <linux/ktime.h>
#include <linux/limits.h>
#include <linux/sched.h>

static char func_name[NAME_MAX] = "do_fork";
module_param_string(func, func_name, NAME_MAX, S_IRUGO);
MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
			" function's execution time");

/* per-instance private data */
struct my_data {
	ktime_t entry_stamp;
};

/* Here we use the entry_hanlder to timestamp function entry */
static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
{
	struct my_data *data;

	if (!current->mm)
		return 1;	/* Skip kernel threads */

	data = (struct my_data *)ri->data;
	data->entry_stamp = ktime_get();
	return 0;
}

/*
 * Return-probe handler: Log the return value and duration. Duration may turn
 * out to be zero consistently, depending upon the granularity of time
 * accounting on the platform.
 */
static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
{
	int retval = regs_return_value(regs);
	struct my_data *data = (struct my_data *)ri->data;
	s64 delta;
	ktime_t now;

	now = ktime_get();
	delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
	printk(KERN_INFO "%s returned %d and took %lld ns to execute\n",
			func_name, retval, (long long)delta);
	return 0;
}

static struct kretprobe my_kretprobe = {
	.handler		= ret_handler,
	.entry_handler		= entry_handler,
	.data_size		= sizeof(struct my_data),
	/* Probe up to 20 instances concurrently. */
	.maxactive		= 20,
};

static int __init kretprobe_init(void)
{
	int ret;

	my_kretprobe.kp.symbol_name = func_name;
	ret = register_kretprobe(&my_kretprobe);
	if (ret < 0) {
		printk(KERN_INFO "register_kretprobe failed, returned %d\n",
				ret);
		return -1;
	}
	printk(KERN_INFO "Planted return probe at %s: %p\n",
			my_kretprobe.kp.symbol_name, my_kretprobe.kp.addr);
	return 0;
}

static void __exit kretprobe_exit(void)
{
	unregister_kretprobe(&my_kretprobe);
	printk(KERN_INFO "kretprobe at %p unregistered\n",
			my_kretprobe.kp.addr);

	/* nmissed > 0 suggests that maxactive was set too low. */
	printk(KERN_INFO "Missed probing %d instances of %s\n",
		my_kretprobe.nmissed, my_kretprobe.kp.symbol_name);
}

module_init(kretprobe_init)
module_exit(kretprobe_exit)
MODULE_LICENSE("GPL");
Commit	Line	Data
804defea AM	1	/*
	2	* kretprobe_example.c
	3	*
	4	* Here's a sample kernel module showing the use of return probes to
	5	* report the return value and total time taken for probed function
	6	* to run.
	7	*
	8	* usage: insmod kretprobe_example.ko func=<func_name>
	9	*
	10	* If no func_name is specified, do_fork is instrumented
	11	*
	12	* For more information on theory of operation of kretprobes, see
	13	* Documentation/kprobes.txt
	14	*
	15	* Build and insert the kernel module as done in the kprobe example.
	16	* You will see the trace data in /var/log/messages and on the console
	17	* whenever the probed function returns. (Some messages may be suppressed
	18	* if syslogd is configured to eliminate duplicate messages.)
	19	*/
	20
	21	#include <linux/kernel.h>
	22	#include <linux/module.h>
	23	#include <linux/kprobes.h>
	24	#include <linux/ktime.h>
	25	#include <linux/limits.h>
8abf9196	26	#include <linux/sched.h>
804defea AM	27
	28	static char func_name[NAME_MAX] = "do_fork";
	29	module_param_string(func, func_name, NAME_MAX, S_IRUGO);
	30	MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
	31	" function's execution time");
	32
	33	/* per-instance private data */
	34	struct my_data {
	35	ktime_t entry_stamp;
	36	};
	37
	38	/* Here we use the entry_hanlder to timestamp function entry */
	39	static int entry_handler(struct kretprobe_instance ri, struct pt_regs regs)
	40	{
	41	struct my_data *data;
	42
	43	if (!current->mm)
	44	return 1; /* Skip kernel threads */
	45
	46	data = (struct my_data *)ri->data;
	47	data->entry_stamp = ktime_get();
	48	return 0;
	49	}
	50
	51	/*
	52	* Return-probe handler: Log the return value and duration. Duration may turn
	53	* out to be zero consistently, depending upon the granularity of time
	54	* accounting on the platform.
	55	*/
	56	static int ret_handler(struct kretprobe_instance ri, struct pt_regs regs)
	57	{
	58	int retval = regs_return_value(regs);
	59	struct my_data data = (struct my_data )ri->data;
	60	s64 delta;
	61	ktime_t now;
	62
	63	now = ktime_get();
	64	delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
	65	printk(KERN_INFO "%s returned %d and took %lld ns to execute\n",
	66	func_name, retval, (long long)delta);
	67	return 0;
	68	}
	69
	70	static struct kretprobe my_kretprobe = {
	71	.handler = ret_handler,
	72	.entry_handler = entry_handler,
	73	.data_size = sizeof(struct my_data),
	74	/* Probe up to 20 instances concurrently. */
	75	.maxactive = 20,
	76	};
	77
	78	static int __init kretprobe_init(void)
	79	{
	80	int ret;
	81
	82	my_kretprobe.kp.symbol_name = func_name;
	83	ret = register_kretprobe(&my_kretprobe);
	84	if (ret < 0) {
	85	printk(KERN_INFO "register_kretprobe failed, returned %d\n",
	86	ret);
	87	return -1;
	88	}
	89	printk(KERN_INFO "Planted return probe at %s: %p\n",
	90	my_kretprobe.kp.symbol_name, my_kretprobe.kp.addr);
91	return 0;
92	}
93
94	static void __exit kretprobe_exit(void)
95	{
96	unregister_kretprobe(&my_kretprobe);
97	printk(KERN_INFO "kretprobe at %p unregistered\n",
98	my_kretprobe.kp.addr);
99
100	/* nmissed > 0 suggests that maxactive was set too low. */
101	printk(KERN_INFO "Missed probing %d instances of %s\n",
102	my_kretprobe.nmissed, my_kretprobe.kp.symbol_name);
103	}
104
105	module_init(kretprobe_init)
106	module_exit(kretprobe_exit)
107	MODULE_LICENSE("GPL");