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bpf: Factor out bpf_link_by_id() helper.

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

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200819042759.51280-2-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2020-08-18 21:27:56 -07:00 committed by Daniel Borkmann
parent 6e9cab2e3f
commit 005142b8a1
2 changed files with 29 additions and 18 deletions
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1
include/linux/bpf.h
View File

@ -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 */

46
kernel/bpf/syscall.c
View File

@ -4014,9 +4014,31 @@ 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);
}
struct bpf_link *bpf_link_by_id(u32 id)
{
struct bpf_link *link;
if (!id)
return ERR_PTR(-ENOENT);
spin_lock_bh(&link_idr_lock);
/* before link is "settled", ID is 0, pretend it doesn't exist yet */
link = idr_find(&link_idr, id);
if (link) {
if (link->id)
link = bpf_link_inc_not_zero(link);
else
link = ERR_PTR(-EAGAIN);
} else {
link = ERR_PTR(-ENOENT);
}
spin_unlock_bh(&link_idr_lock);
return link;
}
#define BPF_LINK_GET_FD_BY_ID_LAST_FIELD link_id
@ -4025,7 +4047,7 @@ static int bpf_link_get_fd_by_id(const union bpf_attr *attr)
{
struct bpf_link *link;
u32 id = attr->link_id;
int fd, err;
int fd;
if (CHECK_ATTR(BPF_LINK_GET_FD_BY_ID))
return -EINVAL;
@ -4033,21 +4055,9 @@ static int bpf_link_get_fd_by_id(const union bpf_attr *attr)
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
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 */
if (link) {
if (link->id)
err = bpf_link_inc_not_zero(link);
else
err = -EAGAIN;
} else {
err = -ENOENT;
}
spin_unlock_bh(&link_idr_lock);
if (err)
return err;
link = bpf_link_by_id(id);
if (IS_ERR(link))
return PTR_ERR(link);
fd = bpf_link_new_fd(link);
if (fd < 0)