Commit f96f644a authored by Song Liu's avatar Song Liu Committed by Daniel Borkmann
Browse files

ftrace: Add modify_ftrace_direct_multi_nolock 



This is similar to modify_ftrace_direct_multi, but does not acquire
direct_mutex. This is useful when direct_mutex is already locked by the
user.

Signed-off-by: default avatarSong Liu <song@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/bpf/20220720002126.803253-2-song@kernel.org
parent f664f9c6

include/linux/ftrace.h

+5 −0
Original line number Diff line number Diff line
@@ -340,6 +340,7 @@ unsigned long ftrace_find_rec_direct(unsigned long ip); 
int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);

int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);

int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);

int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr);



#else

struct ftrace_ops;
@@ -384,6 +385,10 @@ static inline int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned lo 
{

	return -ENODEV;

}

static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr)

{

	return -ENODEV;

}

#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */



#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS

kernel/trace/ftrace.c

+62 −24
Original line number Diff line number Diff line
@@ -5691,22 +5691,8 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) 
}

EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);



/**

 * modify_ftrace_direct_multi - Modify an existing direct 'multi' call

 * to call something else

 * @ops: The address of the struct ftrace_ops object

 * @addr: The address of the new trampoline to call at @ops functions

 *

 * This is used to unregister currently registered direct caller and

 * register new one @addr on functions registered in @ops object.

 *

 * Note there's window between ftrace_shutdown and ftrace_startup calls

 * where there will be no callbacks called.

 *

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

 *  -EINVAL - The @ops object was not properly registered.

 */

int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)

static int

__modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)

{

	struct ftrace_hash *hash;

	struct ftrace_func_entry *entry, *iter;
@@ -5717,12 +5703,7 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) 
	int i, size;

	int err;



	if (check_direct_multi(ops))

		return -EINVAL;

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

		return -EINVAL;



	mutex_lock(&direct_mutex);

	lockdep_assert_held_once(&direct_mutex);



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

	ftrace_ops_init(&tmp_ops);
@@ -5730,7 +5711,7 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) 


	err = register_ftrace_function(&tmp_ops);

	if (err)

		goto out_direct;

		return err;



	/*

	 * Now the ftrace_ops_list_func() is called to do the direct callers.
@@ -5754,7 +5735,64 @@ int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr) 
	/* Removing the tmp_ops will add the updated direct callers to the functions */

	unregister_ftrace_function(&tmp_ops);



 out_direct:

	return err;

}



/**

 * modify_ftrace_direct_multi_nolock - Modify an existing direct 'multi' call

 * to call something else

 * @ops: The address of the struct ftrace_ops object

 * @addr: The address of the new trampoline to call at @ops functions

 *

 * This is used to unregister currently registered direct caller and

 * register new one @addr on functions registered in @ops object.

 *

 * Note there's window between ftrace_shutdown and ftrace_startup calls

 * where there will be no callbacks called.

 *

 * Caller should already have direct_mutex locked, so we don't lock

 * direct_mutex here.

 *

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

 *  -EINVAL - The @ops object was not properly registered.

 */

int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsigned long addr)

{

	if (check_direct_multi(ops))

		return -EINVAL;

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

		return -EINVAL;



	return __modify_ftrace_direct_multi(ops, addr);

}

EXPORT_SYMBOL_GPL(modify_ftrace_direct_multi_nolock);



/**

 * modify_ftrace_direct_multi - Modify an existing direct 'multi' call

 * to call something else

 * @ops: The address of the struct ftrace_ops object

 * @addr: The address of the new trampoline to call at @ops functions

 *

 * This is used to unregister currently registered direct caller and

 * register new one @addr on functions registered in @ops object.

 *

 * Note there's window between ftrace_shutdown and ftrace_startup calls

 * where there will be no callbacks called.

 *

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

 *  -EINVAL - The @ops object was not properly registered.

 */

int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)

{

	int err;



	if (check_direct_multi(ops))

		return -EINVAL;

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

		return -EINVAL;



	mutex_lock(&direct_mutex);

	err = __modify_ftrace_direct_multi(ops, addr);

	mutex_unlock(&direct_mutex);

	return err;

}