static int __kprobes pre_kprobes_handler()

in kernel/kprobes.c [695:791]

• 61 lines of code
• 12 McCabe index (conditional complexity)

static int __kprobes pre_kprobes_handler(struct die_args *args)
{
	struct kprobe *p;
	int ret = 0;
	struct pt_regs *regs = args->regs;
	kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);
	struct kprobe_ctlblk *kcb;

	/*
	 * We don't want to be preempted for the entire
	 * duration of kprobe processing
	 */
	preempt_disable();
	kcb = get_kprobe_ctlblk();

	/* Handle recursion cases */
	if (kprobe_running()) {
		p = get_kprobe(addr);
		if (p) {
			if ((kcb->kprobe_status == KPROBE_HIT_SS) &&
	 		     (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) {
				ia64_psr(regs)->ss = 0;
				goto no_kprobe;
			}
			/* We have reentered the pre_kprobe_handler(), since
			 * another probe was hit while within the handler.
			 * We here save the original kprobes variables and
			 * just single step on the instruction of the new probe
			 * without calling any user handlers.
			 */
			save_previous_kprobe(kcb);
			set_current_kprobe(p, kcb);
			kprobes_inc_nmissed_count(p);
			prepare_ss(p, regs);
			kcb->kprobe_status = KPROBE_REENTER;
			return 1;
		} else if (!is_ia64_break_inst(regs)) {
			/* The breakpoint instruction was removed by
			 * another cpu right after we hit, no further
			 * handling of this interrupt is appropriate
			 */
			ret = 1;
			goto no_kprobe;
		} else {
			/* Not our break */
			goto no_kprobe;
		}
	}

	p = get_kprobe(addr);
	if (!p) {
		if (!is_ia64_break_inst(regs)) {
			/*
			 * The breakpoint instruction was removed right
			 * after we hit it.  Another cpu has removed
			 * either a probepoint or a debugger breakpoint
			 * at this address.  In either case, no further
			 * handling of this interrupt is appropriate.
			 */
			ret = 1;

		}

		/* Not one of our break, let kernel handle it */
		goto no_kprobe;
	}

	set_current_kprobe(p, kcb);
	kcb->kprobe_status = KPROBE_HIT_ACTIVE;

	if (p->pre_handler && p->pre_handler(p, regs)) {
		reset_current_kprobe();
		preempt_enable_no_resched();
		return 1;
	}

#if !defined(CONFIG_PREEMPTION)
	if (p->ainsn.inst_flag == INST_FLAG_BOOSTABLE && !p->post_handler) {
		/* Boost up -- we can execute copied instructions directly */
		ia64_psr(regs)->ri = p->ainsn.slot;
		regs->cr_iip = (unsigned long)&p->ainsn.insn->bundle & ~0xFULL;
		/* turn single stepping off */
		ia64_psr(regs)->ss = 0;

		reset_current_kprobe();
		preempt_enable_no_resched();
		return 1;
	}
#endif
	prepare_ss(p, regs);
	kcb->kprobe_status = KPROBE_HIT_SS;
	return 1;

no_kprobe:
	preempt_enable_no_resched();
	return ret;
}