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Commit b9760156 authored by Harvey Harrison's avatar Harvey Harrison Committed by Ingo Molnar
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x86: kprobes change kprobe_handler flow 



Make the control flow of kprobe_handler more obvious.

Collapse the separate if blocks/gotos with if/else blocks
this unifies the duplication of the check for a breakpoint
instruction race with another cpu.

Create two jump targets:
	preempt_out: re-enables preemption before returning ret
	out: only returns ret

Signed-off-by: default avatarHarvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 33cb5243

arch/x86/kernel/kprobes.c

+28 −32
Original line number Diff line number Diff line
@@ -494,32 +494,28 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	preempt_disable();

	kcb = get_kprobe_ctlblk();



	/* Check we're not actually recursing */

	if (kprobe_running()) {

	p = get_kprobe(addr);

	if (p) {

		/* Check we're not actually recursing */

		if (kprobe_running()) {

			ret = reenter_kprobe(p, regs, kcb);

			if (kcb->kprobe_status == KPROBE_REENTER)

				return 1;

		} else {

			if (*addr != BREAKPOINT_INSTRUCTION) {

			/* The breakpoint instruction was removed by

			 * another cpu right after we hit, no further

			 * handling of this interrupt is appropriate

			 */

				regs->ip = (unsigned long)addr;

			{

				ret = 1;

				goto no_kprobe;

				goto out;

			}

			p = __get_cpu_var(current_kprobe);

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

				goto ss_probe;

			goto preempt_out;

		} else {

			set_current_kprobe(p, regs, kcb);

			kcb->kprobe_status = KPROBE_HIT_ACTIVE;

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

			{

				/* handler set things up, skip ss setup */

				ret = 1;

				goto out;

			}

		goto no_kprobe;

		}



	p = get_kprobe(addr);

	if (!p) {

	} else {

		if (*addr != BREAKPOINT_INSTRUCTION) {

			/*

			 * The breakpoint instruction was removed right
@@ -532,34 +528,34 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
			 */

			regs->ip = (unsigned long)addr;

			ret = 1;

			goto preempt_out;

		}

		if (kprobe_running()) {

			p = __get_cpu_var(current_kprobe);

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

				goto ss_probe;

		}

		/* Not one of ours: let kernel handle it */

		goto no_kprobe;

		goto preempt_out;

	}



	set_current_kprobe(p, regs, kcb);

	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:

	ret = 1;

#if !defined(CONFIG_PREEMPT) || defined(CONFIG_PM)

	if (p->ainsn.boostable == 1 && !p->post_handler) {

		/* Boost up -- we can execute copied instructions directly */

		reset_current_kprobe();

		regs->ip = (unsigned long)p->ainsn.insn;

		preempt_enable_no_resched();

		return 1;

		goto preempt_out;

	}

#endif

	prepare_singlestep(p, regs);

	kcb->kprobe_status = KPROBE_HIT_SS;

	return 1;

	goto out;



no_kprobe:

preempt_out:

	preempt_enable_no_resched();

out:

	return ret;

}