kprobe_example.c
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/*
* NOTE: This example is works on x86 and powerpc.
* Here's a sample kernel module showing the use of kprobes to dump a
* stack trace and selected registers when do_fork() is called.
*
* For more information on theory of operation of kprobes, see
* Documentation/kprobes.txt
*
* You will see the trace data in /var/log/messages and on the console
* whenever do_fork() is invoked to create a new process.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kprobes.h>
/* For each probe you need to allocate a kprobe structure */
static struct kprobe kp = {
.symbol_name = "do_fork",
};
/* kprobe pre_handler: called just before the probed instruction is executed */
static int handler_pre(struct kprobe *p, struct pt_regs *regs)
{
#ifdef CONFIG_X86
printk(KERN_INFO "pre_handler: p->addr = 0x%p, ip = %lx,"
" flags = 0x%lx\n",
p->addr, regs->ip, regs->flags);
#endif
#ifdef CONFIG_PPC
printk(KERN_INFO "pre_handler: p->addr = 0x%p, nip = 0x%lx,"
" msr = 0x%lx\n",
p->addr, regs->nip, regs->msr);
#endif
#ifdef CONFIG_MIPS
printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx,"
" status = 0x%lx\n",
p->addr, regs->cp0_epc, regs->cp0_status);
#endif
#ifdef CONFIG_TILEGX
printk(KERN_INFO "pre_handler: p->addr = 0x%p, pc = 0x%lx,"
" ex1 = 0x%lx\n",
p->addr, regs->pc, regs->ex1);
#endif
/* A dump_stack() here will give a stack backtrace */
return 0;
}
/* kprobe post_handler: called after the probed instruction is executed */
static void handler_post(struct kprobe *p, struct pt_regs *regs,
unsigned long flags)
{
#ifdef CONFIG_X86
printk(KERN_INFO "post_handler: p->addr = 0x%p, flags = 0x%lx\n",
p->addr, regs->flags);
#endif
#ifdef CONFIG_PPC
printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx\n",
p->addr, regs->msr);
#endif
#ifdef CONFIG_MIPS
printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx\n",
p->addr, regs->cp0_status);
#endif
#ifdef CONFIG_TILEGX
printk(KERN_INFO "post_handler: p->addr = 0x%p, ex1 = 0x%lx\n",
p->addr, regs->ex1);
#endif
}
/*
* fault_handler: this is called if an exception is generated for any
* instruction within the pre- or post-handler, or when Kprobes
* single-steps the probed instruction.
*/
static int handler_fault(struct kprobe *p, struct pt_regs *regs, int trapnr)
{
printk(KERN_INFO "fault_handler: p->addr = 0x%p, trap #%dn",
p->addr, trapnr);
/* Return 0 because we don't handle the fault. */
return 0;
}
static int __init kprobe_init(void)
{
int ret;
kp.pre_handler = handler_pre;
kp.post_handler = handler_post;
kp.fault_handler = handler_fault;
ret = register_kprobe(&kp);
if (ret < 0) {
printk(KERN_INFO "register_kprobe failed, returned %d\n", ret);
return ret;
}
printk(KERN_INFO "Planted kprobe at %p\n", kp.addr);
return 0;
}
static void __exit kprobe_exit(void)
{
unregister_kprobe(&kp);
printk(KERN_INFO "kprobe at %p unregistered\n", kp.addr);
}
module_init(kprobe_init)
module_exit(kprobe_exit)
MODULE_LICENSE("GPL");