Messages in this thread | | | Date | Sun, 20 Oct 2013 01:00:18 +0900 | From | Masami Hiramatsu <> | Subject | Re: kprobe pre_handler change return IP |
| |
(2013/10/17 21:57), Liuyongan wrote: > I use kprobe to probe a function suppose: > int is_winter(int num) { ... } > int replace_is_winter(int num) { ...} > I want to replace is_winter() with replace_is_winter(), so when we call is_winter, replace_is_winter will be called. > > so: > int my_pre_handler(struct kprobe *p, struct pt_regs *regs) > { > regs->ip = (unsigned long)&replace_is_winter; > return 1; > } > > and echo 0 > /proc/sys/debug/kprobes-optimization so that jump instruction will not be used. > > I got a exception in fault_handler, and trap number is 14. > > fault_handler: p->addr = 0xffffffffa08e201a, ip = ffffffff8021c59d, trap #14n > > Anyone here can help me ?
If you want to replace something with kprobes, the pre_handler must clean current_kprobe up. Actually the same thing has been done in setup_detour_execution(). So, what you need to do is
> int my_pre_handler(struct kprobe *p, struct pt_regs *regs) > { > regs->ip = (unsigned long)&replace_is_winter;
reset_current_kprobe(); preempt_enable_no_resched();
> return 1; > }
Happy hacking! ;)
Thank you,
-- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
| |