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Message-Id: <20200724055854.59013-2-alexei.starovoitov@gmail.com>
Date: Thu, 23 Jul 2020 22:58:51 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: davem@...emloft.net
Cc: daniel@...earbox.net, torvalds@...ux-foundation.org,
netdev@...r.kernel.org, bpf@...r.kernel.org, kernel-team@...com
Subject: [PATCH v3 bpf-next 1/4] bpf: Factor out bpf_link_get_by_id() helper.
From: Alexei Starovoitov <ast@...nel.org>
Refactor the code a bit to extract bpf_link_get_by_id() helper.
It's similar to existing bpf_prog_by_id().
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Andrii Nakryiko <andriin@...com>
---
include/linux/bpf.h | 1 +
kernel/bpf/syscall.c | 46 +++++++++++++++++++++++++++-----------------
2 files changed, 29 insertions(+), 18 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8357be349133..d5c4e2cc24a0 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1355,6 +1355,7 @@ 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 */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index ee290b1f2d9e..42eb0d622980 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3984,40 +3984,50 @@ static int link_update(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)
--
2.23.0
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