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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>
26#include <linux/sched.h>
27
28static char func_name[NAME_MAX] = "_do_fork";
29module_param_string(func, func_name, NAME_MAX, S_IRUGO);
30MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
31 " function's execution time");
32
33
34struct my_data {
35 ktime_t entry_stamp;
36};
37
38
39static 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;
45
46 data = (struct my_data *)ri->data;
47 data->entry_stamp = ktime_get();
48 return 0;
49}
50
51
52
53
54
55
56static 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
70static struct kretprobe my_kretprobe = {
71 .handler = ret_handler,
72 .entry_handler = entry_handler,
73 .data_size = sizeof(struct my_data),
74
75 .maxactive = 20,
76};
77
78static 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
94static 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
101 printk(KERN_INFO "Missed probing %d instances of %s\n",
102 my_kretprobe.nmissed, my_kretprobe.kp.symbol_name);
103}
104
105module_init(kretprobe_init)
106module_exit(kretprobe_exit)
107MODULE_LICENSE("GPL");
108