Commit 4e885fab authored by Anton Protopopov's avatar Anton Protopopov Committed by Andrii Nakryiko
Browse files

bpf: Add a __btf_get_by_fd helper 



Add a new helper to get a pointer to a struct btf from a file
descriptor. This helper doesn't increase a refcnt. Add a comment
explaining this and pointing to a corresponding function which
does take a reference.

Signed-off-by: default avatarAnton Protopopov <aspsk@isovalent.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241213130934.1087929-2-aspsk@isovalent.com
parent 6a10d2d3

include/linux/bpf.h

+17 −0
Original line number Diff line number Diff line
@@ -2301,6 +2301,14 @@ void __bpf_obj_drop_impl(void *p, const struct btf_record *rec, bool percpu); 
struct bpf_map *bpf_map_get(u32 ufd);

struct bpf_map *bpf_map_get_with_uref(u32 ufd);



/*

 * The __bpf_map_get() and __btf_get_by_fd() functions parse a file

 * descriptor and return a corresponding map or btf object.

 * Their names are double underscored to emphasize the fact that they

 * do not increase refcnt. To also increase refcnt use corresponding

 * bpf_map_get() and btf_get_by_fd() functions.

 */



static inline struct bpf_map *__bpf_map_get(struct fd f)

{

	if (fd_empty(f))
@@ -2310,6 +2318,15 @@ static inline struct bpf_map *__bpf_map_get(struct fd f) 
	return fd_file(f)->private_data;

}



static inline struct btf *__btf_get_by_fd(struct fd f)

{

	if (fd_empty(f))

		return ERR_PTR(-EBADF);

	if (unlikely(fd_file(f)->f_op != &btf_fops))

		return ERR_PTR(-EINVAL);

	return fd_file(f)->private_data;

}



void bpf_map_inc(struct bpf_map *map);

void bpf_map_inc_with_uref(struct bpf_map *map);

struct bpf_map *__bpf_map_inc_not_zero(struct bpf_map *map, bool uref);

kernel/bpf/btf.c

+3 −8
Original line number Diff line number Diff line
@@ -7746,13 +7746,8 @@ struct btf *btf_get_by_fd(int fd) 
	struct btf *btf;

	CLASS(fd, f)(fd);



	if (fd_empty(f))

		return ERR_PTR(-EBADF);



	if (fd_file(f)->f_op != &btf_fops)

		return ERR_PTR(-EINVAL);



	btf = fd_file(f)->private_data;

	btf = __btf_get_by_fd(f);

	if (!IS_ERR(btf))

		refcount_inc(&btf->refcnt);



	return btf;