Commit e93672f7 authored by Jiri Olsa's avatar Jiri Olsa Committed by Andrii Nakryiko
Browse files

ftrace: Add update_ftrace_direct_mod function 



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

The difference to current modify_ftrace_direct is:
- hash argument that allows to modify multiple ip -> direct
  entries at once

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/20251230145010.103439-7-jolsa@kernel.org
parent 8d2c1233

include/linux/ftrace.h

+6 −0
Original line number Diff line number Diff line
@@ -545,6 +545,7 @@ 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);

int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, bool do_direct_lock);



void ftrace_stub_direct_tramp(void);
@@ -582,6 +583,11 @@ static inline int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace 
	return -ENODEV;

}



static inline int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, bool do_direct_lock)

{

	return -ENODEV;

}



/*

 * This must be implemented by the architecture.

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

kernel/trace/ftrace.c

+94 −0
Original line number Diff line number Diff line
@@ -6545,6 +6545,100 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) 
	return err;

}



/**

 * update_ftrace_direct_mod - Updates @ops by modifing its direct

 * callers provided in @hash

 * @ops: The address of the struct ftrace_ops object

 * @hash: The address of the struct ftrace_hash object

 * @do_direct_lock: If true lock the direct_mutex

 *

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

 * @ops specified via @hash.

 *

 * This can be called from within ftrace ops_func callback with

 * direct_mutex already locked, in which case @do_direct_lock

 * needs to be false.

 *

 * 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_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, bool do_direct_lock)

{

	struct ftrace_func_entry *entry, *tmp;

	static struct ftrace_ops tmp_ops = {

		.func		= ftrace_stub,

		.flags		= FTRACE_OPS_FL_STUB,

	};

	struct ftrace_hash *orig_hash;

	unsigned long size, i;

	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;



	/*

	 * We can be called from within ops_func callback with direct_mutex

	 * already taken.

	 */

	if (do_direct_lock)

		mutex_lock(&direct_mutex);



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

	if (!orig_hash)

		goto unlock;



	/* Enable the tmp_ops to have the same functions as the direct ops */

	ftrace_ops_init(&tmp_ops);

	tmp_ops.func_hash = ops->func_hash;



	err = register_ftrace_function_nolock(&tmp_ops);

	if (err)

		goto unlock;



	/*

	 * Call __ftrace_hash_update_ipmodify() here, so that we can call

	 * ops->ops_func for the ops. This is needed because the above

	 * register_ftrace_function_nolock() worked on tmp_ops.

	 */

	err = __ftrace_hash_update_ipmodify(ops, orig_hash, orig_hash, true);

	if (err)

		goto out;



	/*

	 * Now the ftrace_ops_list_func() is called to do the direct callers.

	 * We can safely change the direct functions attached to each entry.

	 */

	mutex_lock(&ftrace_lock);



	size = 1 << hash->size_bits;

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

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

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

			if (!tmp)

				continue;

			tmp->direct = entry->direct;

		}

	}



	mutex_unlock(&ftrace_lock);



out:

	/* Removing the tmp_ops will add the updated direct callers to the functions */

	unregister_ftrace_function(&tmp_ops);



unlock:

	if (do_direct_lock)

		mutex_unlock(&direct_mutex);

	return err;

}



#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */



/**