Commit 689624f0 authored by Joe Burton's avatar Joe Burton Committed by Andrii Nakryiko
Browse files

libbpf: Deprecate bpf_objects_list 

Add a flag to `enum libbpf_strict_mode' to disable the global
`bpf_objects_list', preventing race conditions when concurrent threads
call bpf_object__open() or bpf_object__close().

bpf_object__next() will return NULL if this option is set.

Callers may achieve the same workflow by tracking bpf_objects in
application code.

  [0] Closes: https://github.com/libbpf/libbpf/issues/293



Signed-off-by: default avatarJoe Burton <jevburton@google.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211026223528.413950-1-jevburton.kernel@gmail.com
parent 20d1b54a

tools/lib/bpf/libbpf.c

+7 −1
Original line number Diff line number Diff line
@@ -1148,6 +1148,7 @@ static struct bpf_object *bpf_object__new(const char *path, 
					  size_t obj_buf_sz,

					  const char *obj_name)

{

	bool strict = (libbpf_mode & LIBBPF_STRICT_NO_OBJECT_LIST);

	struct bpf_object *obj;

	char *end;
@@ -1188,6 +1189,7 @@ static struct bpf_object *bpf_object__new(const char *path, 
	obj->loaded = false;



	INIT_LIST_HEAD(&obj->list);

	if (!strict)

		list_add(&obj->list, &bpf_objects_list);

	return obj;

}
@@ -7935,6 +7937,10 @@ struct bpf_object * 
bpf_object__next(struct bpf_object *prev)

{

	struct bpf_object *next;

	bool strict = (libbpf_mode & LIBBPF_STRICT_NO_OBJECT_LIST);



	if (strict)

		return NULL;



	if (!prev)

		next = list_first_entry(&bpf_objects_list,

tools/lib/bpf/libbpf.h

+2 −1
Original line number Diff line number Diff line
@@ -168,7 +168,8 @@ LIBBPF_API struct bpf_program * 
bpf_object__find_program_by_name(const struct bpf_object *obj,

				 const char *name);



LIBBPF_API struct bpf_object *bpf_object__next(struct bpf_object *prev);

LIBBPF_API LIBBPF_DEPRECATED_SINCE(0, 7, "track bpf_objects in application code instead")

struct bpf_object *bpf_object__next(struct bpf_object *prev);

#define bpf_object__for_each_safe(pos, tmp)			\

	for ((pos) = bpf_object__next(NULL),		\

		(tmp) = bpf_object__next(pos);		\

tools/lib/bpf/libbpf_legacy.h

+6 −0
Original line number Diff line number Diff line
@@ -57,6 +57,12 @@ enum libbpf_strict_mode { 
	 * function name instead of section name.

	 */

	LIBBPF_STRICT_SEC_NAME = 0x04,

	/*

	 * Disable the global 'bpf_objects_list'. Maintaining this list adds

	 * a race condition to bpf_object__open() and bpf_object__close().

	 * Clients can maintain it on their own if it is valuable for them.

	 */

	LIBBPF_STRICT_NO_OBJECT_LIST = 0x08,



	__LIBBPF_STRICT_LAST,

};