x86: kprobes change kprobe_handler flow (f315decb) · Commits · jan.koester / Linux

arch/x86/kernel/kprobes.c

+86 −67

Original line number	Diff line number	Diff line
		@@ -442,6 +442,34 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
		/* Replace the return addr with trampoline addr */
		*sara = (unsigned long) &kretprobe_trampoline;
		}

		static void __kprobes recursive_singlestep(struct kprobe *p,
		struct pt_regs *regs,
		struct kprobe_ctlblk *kcb)
		{
		save_previous_kprobe(kcb);
		set_current_kprobe(p, regs, kcb);
		kprobes_inc_nmissed_count(p);
		prepare_singlestep(p, regs);
		kcb->kprobe_status = KPROBE_REENTER;
		}

		static void __kprobes setup_singlestep(struct kprobe p, struct pt_regs regs,
		struct kprobe_ctlblk *kcb)
		{
		#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;
		}
		#endif
		prepare_singlestep(p, regs);
		kcb->kprobe_status = KPROBE_HIT_SS;
		}

		/*
		* We have reentered the kprobe_handler(), since another probe was hit while
		* within the handler. We save the original kprobes variables and just single
		@@ -450,13 +478,9 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
		static int __kprobes reenter_kprobe(struct kprobe p, struct pt_regs regs,
		struct kprobe_ctlblk *kcb)
		{
		if (kcb->kprobe_status == KPROBE_HIT_SS &&
		*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
		regs->flags &= ~X86_EFLAGS_TF;
		regs->flags \|= kcb->kprobe_saved_flags;
		return 0;
		switch (kcb->kprobe_status) {
		case KPROBE_HIT_SSDONE:
		#ifdef CONFIG_X86_64
		} else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
		/* TODO: Provide re-entrancy from post_kprobes_handler() and
		* avoid exception stack corruption while single-stepping on
		* the instruction of the new probe.
		@@ -464,14 +488,26 @@ static int __kprobes reenter_kprobe(struct kprobe p, struct pt_regs regs,
		arch_disarm_kprobe(p);
		regs->ip = (unsigned long)p->addr;
		reset_current_kprobe();
		return 1;
		preempt_enable_no_resched();
		break;
		#endif
		case KPROBE_HIT_ACTIVE:
		recursive_singlestep(p, regs, kcb);
		break;
		case KPROBE_HIT_SS:
		if (*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
		regs->flags &= ~TF_MASK;
		regs->flags \|= kcb->kprobe_saved_flags;
		return 0;
		} else {
		recursive_singlestep(p, regs, kcb);
		}
		save_previous_kprobe(kcb);
		set_current_kprobe(p, regs, kcb);
		kprobes_inc_nmissed_count(p);
		prepare_singlestep(p, regs);
		kcb->kprobe_status = KPROBE_REENTER;
		break;
		default:
		/* impossible cases */
		WARN_ON(1);
		}

		return 1;
		}

		@@ -481,83 +517,66 @@ static int __kprobes reenter_kprobe(struct kprobe p, struct pt_regs regs,
		*/
		static int __kprobes kprobe_handler(struct pt_regs *regs)
		{
		struct kprobe *p;
		int ret = 0;
		kprobe_opcode_t *addr;
		struct kprobe *p;
		struct kprobe_ctlblk *kcb;

		addr = (kprobe_opcode_t *)(regs->ip - sizeof(kprobe_opcode_t));
		if (*addr != BREAKPOINT_INSTRUCTION) {
		/*
		* 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.
		* Back up over the (now missing) int3 and run
		* the original instruction.
		*/
		regs->ip = (unsigned long)addr;
		return 1;
		}

		/*
		* We don't want to be preempted for the entire
		* duration of kprobe processing
		* duration of kprobe processing. We conditionally
		* re-enable preemption at the end of this function,
		* and also in reenter_kprobe() and setup_singlestep().
		*/
		preempt_disable();
		kcb = get_kprobe_ctlblk();

		kcb = get_kprobe_ctlblk();
		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)
		{
		ret = 1;
		goto out;
		}
		goto preempt_out;
		if (reenter_kprobe(p, regs, kcb))
		return 1;
		} 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;
		}
		}
		} else {
		if (*addr != BREAKPOINT_INSTRUCTION) {

		/*
		* 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.
		* Back up over the (now missing) int3 and run
		* the original instruction.
		* If we have no pre-handler or it returned 0, we
		* continue with normal processing. 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.
		*/
		regs->ip = (unsigned long)addr;
		ret = 1;
		goto preempt_out;
		if (!p->pre_handler \|\| !p->pre_handler(p, regs))
		setup_singlestep(p, regs, kcb);
		return 1;
		}
		if (kprobe_running()) {
		} else 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 preempt_out;
		}

		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;
		goto preempt_out;
		if (p->break_handler && p->break_handler(p, regs)) {
		setup_singlestep(p, regs, kcb);
		return 1;
		}
		#endif
		prepare_singlestep(p, regs);
		kcb->kprobe_status = KPROBE_HIT_SS;
		goto out;
		} /* else: not a kprobe fault; let the kernel handle it */

		preempt_out:
		preempt_enable_no_resched();
		out:
		return ret;
		return 0;
		}

		/*