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1 | /* |
2 | * NOTE: This example is works on x86 and powerpc. |
3 | * Here's a sample kernel module showing the use of kprobes to dump a |
4 | * stack trace and selected registers when do_fork() is called. |
5 | * |
6 | * For more information on theory of operation of kprobes, see |
7 | * Documentation/kprobes.txt |
8 | * |
9 | * You will see the trace data in /var/log/messages and on the console |
10 | * whenever do_fork() is invoked to create a new process. |
11 | */ |
12 | |
13 | #include <linux/kernel.h> |
14 | #include <linux/module.h> |
15 | #include <linux/kprobes.h> |
16 | |
17 | /* For each probe you need to allocate a kprobe structure */ |
18 | static struct kprobe kp = { |
19 | .symbol_name = "do_fork", |
20 | }; |
21 | |
22 | /* kprobe pre_handler: called just before the probed instruction is executed */ |
23 | static int handler_pre(struct kprobe *p, struct pt_regs *regs) |
24 | { |
25 | #ifdef CONFIG_X86 |
26 | printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx," |
27 | " flags = 0x%lx\n", |
28 | p->addr, regs->ip, regs->flags); |
29 | #endif |
30 | #ifdef CONFIG_PPC |
31 | printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx," |
32 | " msr = 0x%lx\n", |
33 | p->addr, regs->nip, regs->msr); |
34 | #endif |
35 | #ifdef CONFIG_MIPS |
36 | printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx," |
37 | " status = 0x%lx\n", |
38 | p->addr, regs->cp0_epc, regs->cp0_status); |
39 | #endif |
40 | |
41 | /* A dump_stack() here will give a stack backtrace */ |
42 | return 0; |
43 | } |
44 | |
45 | /* kprobe post_handler: called after the probed instruction is executed */ |
46 | static void handler_post(struct kprobe *p, struct pt_regs *regs, |
47 | unsigned long flags) |
48 | { |
49 | #ifdef CONFIG_X86 |
50 | printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n", |
51 | p->addr, regs->flags); |
52 | #endif |
53 | #ifdef CONFIG_PPC |
54 | printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n", |
55 | p->addr, regs->msr); |
56 | #endif |
57 | #ifdef CONFIG_MIPS |
58 | printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx\n", |
59 | p->addr, regs->cp0_status); |
60 | #endif |
61 | } |
62 | |
63 | /* |
64 | * fault_handler: this is called if an exception is generated for any |
65 | * instruction within the pre- or post-handler, or when Kprobes |
66 | * single-steps the probed instruction. |
67 | */ |
68 | static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr) |
69 | { |
70 | printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn", |
71 | p->addr, trapnr); |
72 | /* Return 0 because we don't handle the fault. */ |
73 | return 0; |
74 | } |
75 | |
76 | static int __init kprobe_init(void) |
77 | { |
78 | int ret; |
79 | kp.pre_handler = handler_pre; |
80 | kp.post_handler = handler_post; |
81 | kp.fault_handler = handler_fault; |
82 | |
83 | ret = register_kprobe(&kp); |
84 | if (ret < 0) { |
85 | printk(KERN_INFO "register_kprobe failed, returned %d\n", ret); |
86 | return ret; |
87 | } |
88 | printk(KERN_INFO "Planted kprobe at %p\n", kp.addr); |
89 | return 0; |
90 | } |
91 | |
92 | static void __exit kprobe_exit(void) |
93 | { |
94 | unregister_kprobe(&kp); |
95 | printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr); |
96 | } |
97 | |
98 | module_init(kprobe_init) |
99 | module_exit(kprobe_exit) |
100 | MODULE_LICENSE("GPL"); |
101 |
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