mirror of https://gitee.com/openkylin/linux.git
107 lines
2.9 KiB
C
107 lines
2.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* 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)
|
|
{
|
|
unsigned long 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));
|
|
pr_info("%s returned %lu 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) {
|
|
pr_err("register_kretprobe failed, returned %d\n", ret);
|
|
return -1;
|
|
}
|
|
pr_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);
|
|
pr_info("kretprobe at %p unregistered\n", my_kretprobe.kp.addr);
|
|
|
|
/* nmissed > 0 suggests that maxactive was set too low. */
|
|
pr_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");
|