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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
54aea454 4 * stack trace and selected registers when _do_fork() is called.
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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
54aea454 10 * whenever _do_fork() is invoked to create a new process.
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11 */
12
13#include <linux/kernel.h>
14#include <linux/module.h>
15#include <linux/kprobes.h>
16
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17#define MAX_SYMBOL_LEN 64
18static char symbol[MAX_SYMBOL_LEN] = "_do_fork";
19module_param_string(symbol, symbol, sizeof(symbol), 0644);
20
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21/* For each probe you need to allocate a kprobe structure */
22static struct kprobe kp = {
d04659ac 23 .symbol_name = symbol,
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24};
25
26/* kprobe pre_handler: called just before the probed instruction is executed */
27static int handler_pre(struct kprobe *p, struct pt_regs *regs)
28{
29#ifdef CONFIG_X86
ea9b5013 30 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, ip = %lx,"
804defea 31 " flags = 0x%lx\n",
ea9b5013 32 p->symbol_name, p->addr, regs->ip, regs->flags);
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33#endif
34#ifdef CONFIG_PPC
ea9b5013 35 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, nip = 0x%lx,"
804defea 36 " msr = 0x%lx\n",
ea9b5013 37 p->symbol_name, p->addr, regs->nip, regs->msr);
804defea 38#endif
8a149237 39#ifdef CONFIG_MIPS
ea9b5013 40 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, epc = 0x%lx,"
8a149237 41 " status = 0x%lx\n",
ea9b5013 42 p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
8a149237 43#endif
3fa17c39 44#ifdef CONFIG_TILEGX
ea9b5013 45 printk(KERN_INFO "<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
3fa17c39 46 " ex1 = 0x%lx\n",
ea9b5013 47 p->symbol_name, p->addr, regs->pc, regs->ex1);
3fa17c39 48#endif
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49#ifdef CONFIG_ARM64
50 pr_info("<%s> pre_handler: p->addr = 0x%p, pc = 0x%lx,"
51 " pstate = 0x%lx\n",
52 p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
53#endif
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54
55 /* A dump_stack() here will give a stack backtrace */
56 return 0;
57}
58
59/* kprobe post_handler: called after the probed instruction is executed */
60static void handler_post(struct kprobe *p, struct pt_regs *regs,
61 unsigned long flags)
62{
63#ifdef CONFIG_X86
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64 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, flags = 0x%lx\n",
65 p->symbol_name, p->addr, regs->flags);
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66#endif
67#ifdef CONFIG_PPC
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68 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, msr = 0x%lx\n",
69 p->symbol_name, p->addr, regs->msr);
804defea 70#endif
8a149237 71#ifdef CONFIG_MIPS
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72 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, status = 0x%lx\n",
73 p->symbol_name, p->addr, regs->cp0_status);
8a149237 74#endif
3fa17c39 75#ifdef CONFIG_TILEGX
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76 printk(KERN_INFO "<%s> post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
77 p->symbol_name, p->addr, regs->ex1);
3fa17c39 78#endif
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79#ifdef CONFIG_ARM64
80 pr_info("<%s> post_handler: p->addr = 0x%p, pstate = 0x%lx\n",
81 p->symbol_name, p->addr, (long)regs->pstate);
82#endif
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83}
84
85/*
86 * fault_handler: this is called if an exception is generated for any
87 * instruction within the pre- or post-handler, or when Kprobes
88 * single-steps the probed instruction.
89 */
90static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
91{
92 printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
93 p->addr, trapnr);
94 /* Return 0 because we don't handle the fault. */
95 return 0;
96}
97
98static int __init kprobe_init(void)
99{
100 int ret;
101 kp.pre_handler = handler_pre;
102 kp.post_handler = handler_post;
103 kp.fault_handler = handler_fault;
104
105 ret = register_kprobe(&kp);
106 if (ret < 0) {
107 printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
108 return ret;
109 }
110 printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
111 return 0;
112}
113
114static void __exit kprobe_exit(void)
115{
116 unregister_kprobe(&kp);
117 printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
118}
119
120module_init(kprobe_init)
121module_exit(kprobe_exit)
122MODULE_LICENSE("GPL");