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samples/kprobes/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 ", 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 ", p->addr, regs->nip, regs->msr); #endif |
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#ifdef CONFIG_MIPS printk(KERN_INFO "pre_handler: p->addr = 0x%p, epc = 0x%lx," " status = 0x%lx ", p->addr, regs->cp0_epc, regs->cp0_status); #endif |
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/* 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 ", p->addr, regs->flags); #endif #ifdef CONFIG_PPC printk(KERN_INFO "post_handler: p->addr = 0x%p, msr = 0x%lx ", p->addr, regs->msr); #endif |
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#ifdef CONFIG_MIPS printk(KERN_INFO "post_handler: p->addr = 0x%p, status = 0x%lx ", p->addr, regs->cp0_status); #endif |
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} /* * 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 ", ret); return ret; } printk(KERN_INFO "Planted kprobe at %p ", kp.addr); return 0; } static void __exit kprobe_exit(void) { unregister_kprobe(&kp); printk(KERN_INFO "kprobe at %p unregistered ", kp.addr); } module_init(kprobe_init) module_exit(kprobe_exit) MODULE_LICENSE("GPL"); |