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Commit d217d545 authored by Ananth N Mavinakayanahalli's avatar Ananth N Mavinakayanahalli Committed by Linus Torvalds
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[PATCH] Kprobes: preempt_disable/enable() simplification 



Reorganize the preempt_disable/enable calls to eliminate the extra preempt
depth.  Changes based on Paul McKenney's review suggestions for the kprobes
RCU changeset.

Signed-off-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: default avatarAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 991a51d8

arch/i386/kernel/kprobes.c

+15 −10
Original line number Diff line number Diff line
@@ -153,7 +153,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	int ret = 0;

	kprobe_opcode_t *addr = NULL;

	unsigned long *lp;

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	struct kprobe_ctlblk *kcb;



	/*

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

	 * duration of kprobe processing

	 */

	preempt_disable();

	kcb = get_kprobe_ctlblk();



	/* Check if the application is using LDT entry for its code segment and

	 * calculate the address by reading the base address from the LDT entry.
@@ -221,11 +228,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
		goto no_kprobe;

	}



	/*

	 * This preempt_disable() matches the preempt_enable_no_resched()

	 * in post_kprobe_handler()

	 */

	preempt_disable();

	set_current_kprobe(p, regs, kcb);

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
@@ -239,6 +241,7 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	return 1;



no_kprobe:

	preempt_enable_no_resched();

	return ret;

}
@@ -310,8 +313,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 


	/*

	 * By returning a non-zero value, we are telling

	 * kprobe_handler() that we have handled unlocking

	 * and re-enabling preemption

	 * kprobe_handler() that we don't want the post_handler

	 * to run (and have re-enabled preemption)

	 */

        return 1;

}
@@ -455,7 +458,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
	struct die_args *args = (struct die_args *)data;

	int ret = NOTIFY_DONE;



	rcu_read_lock();

	switch (val) {

	case DIE_INT3:

		if (kprobe_handler(args->regs))
@@ -467,14 +469,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
		break;

	case DIE_GPF:

	case DIE_PAGE_FAULT:

		/* kprobe_running() needs smp_processor_id() */

		preempt_disable();

		if (kprobe_running() &&

		    kprobe_fault_handler(args->regs, args->trapnr))

			ret = NOTIFY_STOP;

		preempt_enable();

		break;

	default:

		break;

	}

	rcu_read_unlock();

	return ret;

}
@@ -537,6 +541,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) 
		*regs = kcb->jprobe_saved_regs;

		memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,

		       MIN_STACK_SIZE(stack_addr));

		preempt_enable_no_resched();

		return 1;

	}

	return 0;

arch/ia64/kernel/kprobes.c

+20 −17
Original line number Diff line number Diff line
@@ -391,8 +391,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 


	/*

	 * By returning a non-zero value, we are telling

         * kprobe_handler() that we have handled unlocking

	 * and re-enabling preemption

	 * kprobe_handler() that we don't want the post_handler

	 * to run (and have re-enabled preemption)

	 */

        return 1;

}
@@ -604,7 +604,14 @@ static int __kprobes pre_kprobes_handler(struct die_args *args) 
	int ret = 0;

	struct pt_regs *regs = args->regs;

	kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	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()) {
@@ -659,11 +666,6 @@ static int __kprobes pre_kprobes_handler(struct die_args *args) 
		goto no_kprobe;

	}



	/*

	 * This preempt_disable() matches the preempt_enable_no_resched()

	 * in post_kprobes_handler()

	 */

	preempt_disable();

	set_current_kprobe(p, kcb);

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
@@ -681,6 +683,7 @@ static int __kprobes pre_kprobes_handler(struct die_args *args) 
	return 1;



no_kprobe:

	preempt_enable_no_resched();

	return ret;

}
@@ -716,9 +719,6 @@ static int __kprobes kprobes_fault_handler(struct pt_regs *regs, int trapnr) 
	struct kprobe *cur = kprobe_running();

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	if (!cur)

		return 0;



	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))

		return 1;
@@ -737,7 +737,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
	struct die_args *args = (struct die_args *)data;

	int ret = NOTIFY_DONE;



	rcu_read_lock();

	switch(val) {

	case DIE_BREAK:

		if (pre_kprobes_handler(args))
@@ -748,12 +747,15 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
			ret = NOTIFY_STOP;

		break;

	case DIE_PAGE_FAULT:

		if (kprobes_fault_handler(args->regs, args->trapnr))

		/* kprobe_running() needs smp_processor_id() */

		preempt_disable();

		if (kprobe_running() &&

			kprobes_fault_handler(args->regs, args->trapnr))

			ret = NOTIFY_STOP;

		preempt_enable();

	default:

		break;

	}

	rcu_read_unlock();

	return ret;

}
@@ -785,6 +787,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) 
	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();



	*regs = kcb->jprobe_saved_regs;

	preempt_enable_no_resched();

	return 1;

}

arch/ppc64/kernel/kprobes.c

+15 −10
Original line number Diff line number Diff line
@@ -148,7 +148,14 @@ static inline int kprobe_handler(struct pt_regs *regs) 
	struct kprobe *p;

	int ret = 0;

	unsigned int *addr = (unsigned int *)regs->nip;

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	struct kprobe_ctlblk *kcb;



	/*

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

	 * duration of kprobe processing

	 */

	preempt_disable();

	kcb = get_kprobe_ctlblk();



	/* Check we're not actually recursing */

	if (kprobe_running()) {
@@ -207,11 +214,6 @@ static inline int kprobe_handler(struct pt_regs *regs) 
		goto no_kprobe;

	}



	/*

	 * This preempt_disable() matches the preempt_enable_no_resched()

	 * in post_kprobe_handler().

	 */

	preempt_disable();

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;

	set_current_kprobe(p, regs, kcb);

	if (p->pre_handler && p->pre_handler(p, regs))
@@ -224,6 +226,7 @@ static inline int kprobe_handler(struct pt_regs *regs) 
	return 1;



no_kprobe:

	preempt_enable_no_resched();

	return ret;

}
@@ -296,8 +299,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 


        /*

         * By returning a non-zero value, we are telling

         * kprobe_handler() that we have handled unlocking

         * and re-enabling preemption.

         * kprobe_handler() that we don't want the post_handler

         * to run (and have re-enabled preemption)

         */

        return 1;

}
@@ -385,7 +388,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
	struct die_args *args = (struct die_args *)data;

	int ret = NOTIFY_DONE;



	rcu_read_lock();

	switch (val) {

	case DIE_BPT:

		if (kprobe_handler(args->regs))
@@ -396,14 +398,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
			ret = NOTIFY_STOP;

		break;

	case DIE_PAGE_FAULT:

		/* kprobe_running() needs smp_processor_id() */

		preempt_disable();

		if (kprobe_running() &&

		    kprobe_fault_handler(args->regs, args->trapnr))

			ret = NOTIFY_STOP;

		preempt_enable();

		break;

	default:

		break;

	}

	rcu_read_unlock();

	return ret;

}
@@ -440,6 +444,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) 
	 * saved regs...

	 */

	memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));

	preempt_enable_no_resched();

	return 1;

}

arch/sparc64/kernel/kprobes.c

+13 −8
Original line number Diff line number Diff line
@@ -113,7 +113,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	struct kprobe *p;

	void *addr = (void *) regs->tpc;

	int ret = 0;

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	struct kprobe_ctlblk *kcb;



	/*

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

	 * duration of kprobe processing

	 */

	preempt_disable();

	kcb = get_kprobe_ctlblk();



	if (kprobe_running()) {

		p = get_kprobe(addr);
@@ -159,11 +166,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
		goto no_kprobe;

	}



	/*

	 * This preempt_disable() matches the preempt_enable_no_resched()

	 * in post_kprobes_handler()

	 */

	preempt_disable();

	set_current_kprobe(p, regs, kcb);

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;

	if (p->pre_handler && p->pre_handler(p, regs))
@@ -175,6 +177,7 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) 
	return 1;



no_kprobe:

	preempt_enable_no_resched();

	return ret;

}
@@ -321,7 +324,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
	struct die_args *args = (struct die_args *)data;

	int ret = NOTIFY_DONE;



	rcu_read_lock();

	switch (val) {

	case DIE_DEBUG:

		if (kprobe_handler(args->regs))
@@ -333,14 +335,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
		break;

	case DIE_GPF:

	case DIE_PAGE_FAULT:

		/* kprobe_running() needs smp_processor_id() */

		preempt_disable();

		if (kprobe_running() &&

		    kprobe_fault_handler(args->regs, args->trapnr))

			ret = NOTIFY_STOP;

		preempt_enable();

		break;

	default:

		break;

	}

	rcu_read_unlock();

	return ret;

}
@@ -426,6 +430,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) 
		       &(kcb->jprobe_saved_stack),

		       sizeof(kcb->jprobe_saved_stack));



		preempt_enable_no_resched();

		return 1;

	}

	return 0;

arch/x86_64/kernel/kprobes.c

+15 −14
Original line number Diff line number Diff line
@@ -286,16 +286,19 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe *rp, 
        }

}



/*

 * Interrupts are disabled on entry as trap3 is an interrupt gate and they

 * remain disabled thorough out this function.

 */

int __kprobes kprobe_handler(struct pt_regs *regs)

{

	struct kprobe *p;

	int ret = 0;

	kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));

	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

	struct kprobe_ctlblk *kcb;



	/*

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

	 * duration of kprobe processing

	 */

	preempt_disable();

	kcb = get_kprobe_ctlblk();



	/* Check we're not actually recursing */

	if (kprobe_running()) {
@@ -359,11 +362,6 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
		goto no_kprobe;

	}



	/*

	 * This preempt_disable() matches the preempt_enable_no_resched()

	 * in post_kprobe_handler()

	 */

	preempt_disable();

	set_current_kprobe(p, regs, kcb);

	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
@@ -377,6 +375,7 @@ int __kprobes kprobe_handler(struct pt_regs *regs) 
	return 1;



no_kprobe:

	preempt_enable_no_resched();

	return ret;

}
@@ -448,8 +447,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 


        /*

         * By returning a non-zero value, we are telling

         * kprobe_handler() that we have handled unlocking

	 * and re-enabling preemption

         * kprobe_handler() that we don't want the post_handler

	 * to run (and have re-enabled preemption)

         */

        return 1;

}
@@ -594,7 +593,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
	struct die_args *args = (struct die_args *)data;

	int ret = NOTIFY_DONE;



	rcu_read_lock();

	switch (val) {

	case DIE_INT3:

		if (kprobe_handler(args->regs))
@@ -606,14 +604,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, 
		break;

	case DIE_GPF:

	case DIE_PAGE_FAULT:

		/* kprobe_running() needs smp_processor_id() */

		preempt_disable();

		if (kprobe_running() &&

		    kprobe_fault_handler(args->regs, args->trapnr))

			ret = NOTIFY_STOP;

		preempt_enable();

		break;

	default:

		break;

	}

	rcu_read_unlock();

	return ret;

}
@@ -675,6 +675,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) 
		*regs = kcb->jprobe_saved_regs;

		memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,

		       MIN_STACK_SIZE(stack_addr));

		preempt_enable_no_resched();

		return 1;

	}

	return 0;