powerpc: kprobes: Use generic kretprobe trampoline handler

void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs)

{

	ri->ret_addr = (kprobe_opcode_t *)regs->link;

	ri->fp = NULL;

	/* Replace the return addr with trampoline addr */

	regs->link = (unsigned long)kretprobe_trampoline;

 */

static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)

{

	struct kretprobe_instance *ri = NULL;

	struct hlist_head *head, empty_rp;

	struct hlist_node *tmp;

	unsigned long flags, orig_ret_address = 0;

	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;

	INIT_HLIST_HEAD(&empty_rp);

	kretprobe_hash_lock(current, &head, &flags);

	/*

	 * It is possible to have multiple instances associated with a given

	 * task either because an multiple functions in the call path

	 * have a return probe installed on them, and/or more than one return

	 * return probe was registered for a target function.

	 *

	 * We can handle this because:

	 *     - instances are always inserted at the head of the list

	 *     - when multiple return probes are registered for the same

	 *       function, the first instance's ret_addr will point to the

	 *       real return address, and all the rest will point to

	 *       kretprobe_trampoline

	 */

	hlist_for_each_entry_safe(ri, tmp, head, hlist) {

		if (ri->task != current)

			/* another task is sharing our hash bucket */

			continue;

		if (ri->rp && ri->rp->handler)

			ri->rp->handler(ri, regs);

		orig_ret_address = (unsigned long)ri->ret_addr;

		recycle_rp_inst(ri, &empty_rp);

		if (orig_ret_address != trampoline_address)

			/*

			 * This is the real return address. Any other

			 * instances associated with this task are for

			 * other calls deeper on the call stack

			 */

			break;

	}

	kretprobe_assert(ri, orig_ret_address, trampoline_address);

	unsigned long orig_ret_address;

	orig_ret_address = __kretprobe_trampoline_handler(regs, &kretprobe_trampoline, NULL);

	/*

	 * We get here through one of two paths:

	 * 1. by taking a trap -> kprobe_handler() -> here

	regs->nip = orig_ret_address - 4;

	regs->link = orig_ret_address;

	kretprobe_hash_unlock(current, &flags);

	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {

		hlist_del(&ri->hlist);

		kfree(ri);

	}

	return 0;

}

NOKPROBE_SYMBOL(trampoline_probe_handler);