Commit a35fb2bc authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google)
Browse files

kprobes: Use guard for rcu_read_lock 

Use guard(rcu) for rcu_read_lock so that it can remove unneeded
gotos and make it more structured.

Link: https://lore.kernel.org/all/173371209846.480397.3852648910271029695.stgit@devnote2/



Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent 54c79390

kernel/kprobes.c

+36 −30
Original line number Diff line number Diff line
@@ -144,8 +144,8 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c) 


	/* Since the slot array is not protected by rcu, we need a mutex */

	guard(mutex)(&c->mutex);

 retry:

	rcu_read_lock();

	do {

		guard(rcu)();

		list_for_each_entry_rcu(kip, &c->pages, list) {

			if (kip->nused < slots_per_page(c)) {

				int i;
@@ -154,7 +154,6 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c) 
					if (kip->slot_used[i] == SLOT_CLEAN) {

						kip->slot_used[i] = SLOT_USED;

						kip->nused++;

					rcu_read_unlock();

						return kip->insns + (i * c->insn_size);

					}

				}
@@ -163,11 +162,8 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c) 
				WARN_ON(1);

			}

		}

	rcu_read_unlock();



	/* If there are any garbage slots, collect it and try again. */

	if (c->nr_garbage && collect_garbage_slots(c) == 0)

		goto retry;

	} while (c->nr_garbage && collect_garbage_slots(c) == 0);



	/* All out of space.  Need to allocate a new page. */

	kip = kmalloc(struct_size(kip, slot_used, slots_per_page(c)), GFP_KERNEL);
@@ -246,25 +242,35 @@ static int collect_garbage_slots(struct kprobe_insn_cache *c) 
	return 0;

}



void __free_insn_slot(struct kprobe_insn_cache *c,

		      kprobe_opcode_t *slot, int dirty)

static long __find_insn_page(struct kprobe_insn_cache *c,

	kprobe_opcode_t *slot, struct kprobe_insn_page **pkip)

{

	struct kprobe_insn_page *kip;

	struct kprobe_insn_page *kip = NULL;

	long idx;



	guard(mutex)(&c->mutex);

	rcu_read_lock();

	guard(rcu)();

	list_for_each_entry_rcu(kip, &c->pages, list) {

		idx = ((long)slot - (long)kip->insns) /

			(c->insn_size * sizeof(kprobe_opcode_t));

		if (idx >= 0 && idx < slots_per_page(c))

			goto out;

		if (idx >= 0 && idx < slots_per_page(c)) {

			*pkip = kip;

			return idx;

		}

	}

	/* Could not find this slot. */

	WARN_ON(1);

	kip = NULL;

out:

	rcu_read_unlock();

	*pkip = NULL;

	return -1;

}



void __free_insn_slot(struct kprobe_insn_cache *c,

		      kprobe_opcode_t *slot, int dirty)

{

	struct kprobe_insn_page *kip = NULL;

	long idx;



	guard(mutex)(&c->mutex);

	idx = __find_insn_page(c, slot, &kip);

	/* Mark and sweep: this may sleep */

	if (kip) {

		/* Check double free */