Commit 8d2c1233 authored by Jiri Olsa's avatar Jiri Olsa Committed by Andrii Nakryiko
Browse files

ftrace: Add update_ftrace_direct_del function 



Adding update_ftrace_direct_del function that removes all entries
(ip -> addr) provided in hash argument to direct ftrace ops and
updates its attachments.

The difference to current unregister_ftrace_direct is
 - hash argument that allows to unregister multiple ip -> direct
   entries at once
 - we can call update_ftrace_direct_del multiple times on the
   same ftrace_ops object, becase we do not need to unregister
   all entries at once, we can do it gradualy with the help of
   ftrace_update_ops function

This change will allow us to have simple ftrace_ops for all bpf
direct interface users in following changes.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/bpf/20251230145010.103439-6-jolsa@kernel.org
parent 05dc5e9c

include/linux/ftrace.h

+6 −0
Original line number Diff line number Diff line
@@ -544,6 +544,7 @@ int modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr); 
int modify_ftrace_direct_nolock(struct ftrace_ops *ops, unsigned long addr);



int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash);

int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash);



void ftrace_stub_direct_tramp(void);
@@ -576,6 +577,11 @@ static inline int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace 
	return -ENODEV;

}



static inline int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)

{

	return -ENODEV;

}



/*

 * This must be implemented by the architecture.

 * It is the way the ftrace direct_ops helper, when called

kernel/trace/ftrace.c

+127 −0
Original line number Diff line number Diff line
@@ -6418,6 +6418,133 @@ int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash) 
	return err;

}



/**

 * hash_sub - substracts @b from @a and returns the result

 * @a: struct ftrace_hash object

 * @b: struct ftrace_hash object

 *

 * Returns struct ftrace_hash object on success, NULL on error.

 */

static struct ftrace_hash *hash_sub(struct ftrace_hash *a, struct ftrace_hash *b)

{

	struct ftrace_func_entry *entry, *del;

	struct ftrace_hash *sub;

	int size;



	sub = alloc_and_copy_ftrace_hash(a->size_bits, a);

	if (!sub)

		return NULL;



	size = 1 << b->size_bits;

	for (int i = 0; i < size; i++) {

		hlist_for_each_entry(entry, &b->buckets[i], hlist) {

			del = __ftrace_lookup_ip(sub, entry->ip);

			if (WARN_ON_ONCE(!del)) {

				free_ftrace_hash(sub);

				return NULL;

			}

			remove_hash_entry(sub, del);

			kfree(del);

		}

	}

	return sub;

}



/**

 * update_ftrace_direct_del - Updates @ops by removing its direct

 * callers provided in @hash

 * @ops: The address of the struct ftrace_ops object

 * @hash: The address of the struct ftrace_hash object

 *

 * This is used to delete custom direct callers (ip -> addr) in

 * @ops specified via @hash. The @ops will be either unregistered

 * updated.

 *

 * Returns: zero on success. Non zero on error, which includes:

 *  -EINVAL - The @hash is empty

 *  -EINVAL - The @ops is not registered

 */

int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)

{

	struct ftrace_hash *old_direct_functions = NULL;

	struct ftrace_hash *new_direct_functions;

	struct ftrace_hash *new_filter_hash = NULL;

	struct ftrace_hash *old_filter_hash;

	struct ftrace_func_entry *entry;

	struct ftrace_func_entry *del;

	unsigned long size;

	int err = -EINVAL;



	if (!hash_count(hash))

		return -EINVAL;

	if (check_direct_multi(ops))

		return -EINVAL;

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

		return -EINVAL;

	if (direct_functions == EMPTY_HASH)

		return -EINVAL;



	mutex_lock(&direct_mutex);



	old_filter_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL;



	if (!hash_count(old_filter_hash))

		goto out_unlock;



	/* Make sure requested entries are already registered. */

	size = 1 << hash->size_bits;

	for (int i = 0; i < size; i++) {

		hlist_for_each_entry(entry, &hash->buckets[i], hlist) {

			del = __ftrace_lookup_ip(direct_functions, entry->ip);

			if (!del || del->direct != entry->direct)

				goto out_unlock;

		}

	}



	err = -ENOMEM;

	new_filter_hash = hash_sub(old_filter_hash, hash);

	if (!new_filter_hash)

		goto out_unlock;



	new_direct_functions = hash_sub(direct_functions, hash);

	if (!new_direct_functions)

		goto out_unlock;



	/* If there's nothing left, we need to unregister the ops. */

	if (ftrace_hash_empty(new_filter_hash)) {

		err = unregister_ftrace_function(ops);

		if (!err) {

			/* cleanup for possible another register call */

			ops->func = NULL;

			ops->trampoline = 0;

			ftrace_free_filter(ops);

			ops->func_hash->filter_hash = NULL;

		}

	} else {

		err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);

		/*

		 * new_filter_hash is dup-ed, so we need to release it anyway,

		 * old_filter_hash either stays on error or is already released

		 */

	}



	if (err) {

		/* free the new_direct_functions */

		old_direct_functions = new_direct_functions;

	} else {

		rcu_assign_pointer(direct_functions, new_direct_functions);

	}



 out_unlock:

	mutex_unlock(&direct_mutex);



	if (old_direct_functions && old_direct_functions != EMPTY_HASH)

		call_rcu_tasks(&old_direct_functions->rcu, register_ftrace_direct_cb);

	free_ftrace_hash(new_filter_hash);



	return err;

}



#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */



/**