Commit 005142b8 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

bpf: Factor out bpf_link_by_id() helper. 



Refactor the code a bit to extract bpf_link_by_id() helper.
It's similar to existing bpf_prog_by_id().

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200819042759.51280-2-alexei.starovoitov@gmail.com
parent 6e9cab2e

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -1358,6 +1358,7 @@ int btf_check_type_match(struct bpf_verifier_env *env, struct bpf_prog *prog, 
			 struct btf *btf, const struct btf_type *t);



struct bpf_prog *bpf_prog_by_id(u32 id);

struct bpf_link *bpf_link_by_id(u32 id);



const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id);

#else /* !CONFIG_BPF_SYSCALL */

kernel/bpf/syscall.c

+28 −18
Original line number Diff line number Diff line
@@ -4014,40 +4014,50 @@ static int link_detach(union bpf_attr *attr) 
	return ret;

}



static int bpf_link_inc_not_zero(struct bpf_link *link)

static struct bpf_link *bpf_link_inc_not_zero(struct bpf_link *link)

{

	return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? 0 : -ENOENT;

	return atomic64_fetch_add_unless(&link->refcnt, 1, 0) ? link : ERR_PTR(-ENOENT);

}



#define BPF_LINK_GET_FD_BY_ID_LAST_FIELD link_id



static int bpf_link_get_fd_by_id(const union bpf_attr *attr)

struct bpf_link *bpf_link_by_id(u32 id)

{

	struct bpf_link *link;

	u32 id = attr->link_id;

	int fd, err;



	if (CHECK_ATTR(BPF_LINK_GET_FD_BY_ID))

		return -EINVAL;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;

	if (!id)

		return ERR_PTR(-ENOENT);



	spin_lock_bh(&link_idr_lock);

	link = idr_find(&link_idr, id);

	/* before link is "settled", ID is 0, pretend it doesn't exist yet */

	link = idr_find(&link_idr, id);

	if (link) {

		if (link->id)

			err = bpf_link_inc_not_zero(link);

			link = bpf_link_inc_not_zero(link);

		else

			err = -EAGAIN;

			link = ERR_PTR(-EAGAIN);

	} else {

		err = -ENOENT;

		link = ERR_PTR(-ENOENT);

	}

	spin_unlock_bh(&link_idr_lock);

	return link;

}



	if (err)

		return err;

#define BPF_LINK_GET_FD_BY_ID_LAST_FIELD link_id



static int bpf_link_get_fd_by_id(const union bpf_attr *attr)

{

	struct bpf_link *link;

	u32 id = attr->link_id;

	int fd;



	if (CHECK_ATTR(BPF_LINK_GET_FD_BY_ID))

		return -EINVAL;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	link = bpf_link_by_id(id);

	if (IS_ERR(link))

		return PTR_ERR(link);



	fd = bpf_link_new_fd(link);

	if (fd < 0)