Commit 0e917cc3 authored by Martin Schwidefsky's avatar Martin Schwidefsky Committed by Martin Schwidefsky
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[S390] kprobes: restructure handler function 



Restructure the kprobe breakpoint handler function. Add comments to
make it more comprehensible and add a sanity check for re-entering
kprobes.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 92b8cbf1

arch/s390/kernel/kprobes.c

+71 −43
Original line number Diff line number Diff line
@@ -238,25 +238,44 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri, 
	regs->gprs[14] = (unsigned long)&kretprobe_trampoline;

}



static void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,

					   struct kprobe *p)

{

	switch (kcb->kprobe_status) {

	case KPROBE_HIT_SSDONE:

	case KPROBE_HIT_ACTIVE:

		kprobes_inc_nmissed_count(p);

		break;

	case KPROBE_HIT_SS:

	case KPROBE_REENTER:

	default:

		/*

		 * A kprobe on the code path to single step an instruction

		 * is a BUG. The code path resides in the .kprobes.text

		 * section and is executed with interrupts disabled.

		 */

		printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);

		dump_kprobe(p);

		BUG();

	}

}



static int __kprobes kprobe_handler(struct pt_regs *regs)

{

	struct kprobe *p;

	int ret = 0;

	unsigned long *addr = (unsigned long *)

		((regs->psw.addr & PSW_ADDR_INSN) - 2);

	struct kprobe_ctlblk *kcb;

	struct kprobe *p;



	/*

	 * We don't want to be preempted for the entire

	 * duration of kprobe processing

	 * We want to disable preemption for the entire duration of kprobe

	 * processing. That includes the calls to the pre/post handlers

	 * and single stepping the kprobe instruction.

	 */

	preempt_disable();

	kcb = get_kprobe_ctlblk();

	p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));



	/* Check we're not actually recursing */

	if (kprobe_running()) {

		p = get_kprobe(addr);

	if (p) {

		if (kprobe_running()) {

			/*

			 * We have hit a kprobe while another is still

			 * active. This can happen in the pre and post
@@ -266,45 +285,54 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
			 * push_kprobe and pop_kprobe saves and restores

			 * the currently active kprobe.

			 */

			kprobe_reenter_check(kcb, p);

			push_kprobe(kcb, p);

			kprobes_inc_nmissed_count(p);

			enable_singlestep(kcb, regs,

					  (unsigned long) p->ainsn.insn);

			kcb->kprobe_status = KPROBE_REENTER;

			return 1;

		} else {

			p = __get_cpu_var(current_kprobe);

			if (p->break_handler && p->break_handler(p, regs)) {

				goto ss_probe;

			}

		}

		goto no_kprobe;

	}



	p = get_kprobe(addr);

	if (!p)

			/*

		 * No kprobe at this address. The fault has not been

		 * caused by a kprobe breakpoint. The race of breakpoint

		 * vs. kprobe remove does not exist because on s390 we

		 * use stop_machine to arm/disarm the breakpoints.

			 * If we have no pre-handler or it returned 0, we

			 * continue with single stepping. If we have a

			 * pre-handler and it returned non-zero, it prepped

			 * for calling the break_handler below on re-entry

			 * for jprobe processing, so get out doing nothing

			 * more here.

			 */

		goto no_kprobe;



	kcb->kprobe_status = KPROBE_HIT_ACTIVE;

			push_kprobe(kcb, p);

			kcb->kprobe_status = KPROBE_HIT_ACTIVE;

			if (p->pre_handler && p->pre_handler(p, regs))

		/* handler has already set things up, so skip ss setup */

				return 1;



ss_probe:

			kcb->kprobe_status = KPROBE_HIT_SS;

		}

		enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);

		return 1;

	} else if (kprobe_running()) {

		p = __get_cpu_var(current_kprobe);

		if (p->break_handler && p->break_handler(p, regs)) {

			/*

			 * Continuation after the jprobe completed and

			 * caused the jprobe_return trap. The jprobe

			 * break_handler "returns" to the original

			 * function that still has the kprobe breakpoint

			 * installed. We continue with single stepping.

			 */

			kcb->kprobe_status = KPROBE_HIT_SS;

			enable_singlestep(kcb, regs,

					  (unsigned long) p->ainsn.insn);

			return 1;



no_kprobe:

		} /* else:

		   * No kprobe at this address and the current kprobe

		   * has no break handler (no jprobe!). The kernel just

		   * exploded, let the standard trap handler pick up the

		   * pieces.

		   */

	} /* else:

	   * No kprobe at this address and no active kprobe. The trap has

	   * not been caused by a kprobe breakpoint. The race of breakpoint

	   * vs. kprobe remove does not exist because on s390 as we use

	   * stop_machine to arm/disarm the breakpoints.

	   */

	preempt_enable_no_resched();

	return ret;

	return 0;

}



/*