Commit 41fb61c2 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

ftrace: Balance records when updating the hash 



Whenever the hash of the ftrace_ops is updated, the record counts
must be balance. This requires disabling the records that are set
in the original hash, and then enabling the records that are set
in the updated hash.

Moving the update into ftrace_hash_move() removes the bug where the
hash was updated but the records were not, which results in ftrace
triggering a warning and disabling itself because the ftrace_ops filter
is updated while the ftrace_ops was registered, and then the failure
happens when the ftrace_ops is unregistered.

The current code will not trigger this bug, but new code will.

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 4376cac6

kernel/trace/ftrace.c

+33 −16
Original line number Diff line number Diff line
@@ -1170,8 +1170,14 @@ alloc_and_copy_ftrace_hash(int size_bits, struct ftrace_hash *hash) 
	return NULL;

}



static void

ftrace_hash_rec_disable(struct ftrace_ops *ops, int filter_hash);

static void

ftrace_hash_rec_enable(struct ftrace_ops *ops, int filter_hash);



static int

ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src)

ftrace_hash_move(struct ftrace_ops *ops, int enable,

		 struct ftrace_hash **dst, struct ftrace_hash *src)

{

	struct ftrace_func_entry *entry;

	struct hlist_node *tp, *tn;
@@ -1181,8 +1187,15 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
	unsigned long key;

	int size = src->count;

	int bits = 0;

	int ret;

	int i;



	/*

	 * Remove the current set, update the hash and add

	 * them back.

	 */

	ftrace_hash_rec_disable(ops, enable);



	/*

	 * If the new source is empty, just free dst and assign it

	 * the empty_hash.
@@ -1203,9 +1216,10 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
	if (bits > FTRACE_HASH_MAX_BITS)

		bits = FTRACE_HASH_MAX_BITS;



	ret = -ENOMEM;

	new_hash = alloc_ftrace_hash(bits);

	if (!new_hash)

		return -ENOMEM;

		goto out;



	size = 1 << src->size_bits;

	for (i = 0; i < size; i++) {
@@ -1224,7 +1238,16 @@ ftrace_hash_move(struct ftrace_hash **dst, struct ftrace_hash *src) 
	rcu_assign_pointer(*dst, new_hash);

	free_ftrace_hash_rcu(old_hash);



	return 0;

	ret = 0;

 out:

	/*

	 * Enable regardless of ret:

	 *  On success, we enable the new hash.

	 *  On failure, we re-enable the original hash.

	 */

	ftrace_hash_rec_enable(ops, enable);



	return ret;

}



/*
@@ -2845,7 +2868,7 @@ ftrace_set_regex(struct ftrace_ops *ops, unsigned char *buf, int len, 
		ftrace_match_records(hash, buf, len);



	mutex_lock(&ftrace_lock);

	ret = ftrace_hash_move(orig_hash, hash);

	ret = ftrace_hash_move(ops, enable, orig_hash, hash);

	mutex_unlock(&ftrace_lock);



	mutex_unlock(&ftrace_regex_lock);
@@ -3028,18 +3051,12 @@ ftrace_regex_release(struct inode *inode, struct file *file) 
			orig_hash = &iter->ops->notrace_hash;



		mutex_lock(&ftrace_lock);

		/*

		 * Remove the current set, update the hash and add

		 * them back.

		 */

		ftrace_hash_rec_disable(iter->ops, filter_hash);

		ret = ftrace_hash_move(orig_hash, iter->hash);

		if (!ret) {

			ftrace_hash_rec_enable(iter->ops, filter_hash);

			if (iter->ops->flags & FTRACE_OPS_FL_ENABLED

		ret = ftrace_hash_move(iter->ops, filter_hash,

				       orig_hash, iter->hash);

		if (!ret && (iter->ops->flags & FTRACE_OPS_FL_ENABLED)

		    && ftrace_enabled)

			ftrace_run_update_code(FTRACE_ENABLE_CALLS);

		}



		mutex_unlock(&ftrace_lock);

	}

	free_ftrace_hash(iter->hash);

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