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[bpf-next,1/3] bpf: Factor out bpf_link_get_by_id() helper.

Message ID 20200702200329.83224-2-alexei.starovoitov@gmail.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series bpf: Populate bpffs with map and prog iterators | expand

Commit Message

Alexei Starovoitov July 2, 2020, 8:03 p.m. UTC 
From: Alexei Starovoitov <ast@kernel.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@kernel.org>
---
 include/linux/bpf.h  |  1 +
 kernel/bpf/syscall.c | 46 +++++++++++++++++++++++++++-----------------
 2 files changed, 29 insertions(+), 18 deletions(-)

Comments

Andrii Nakryiko July 6, 2020, 11:08 p.m. UTC | #1 
On Thu, Jul 2, 2020 at 1:04 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.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@kernel.org>
> ---

LGTM.

Acked-by: Andrii Nakryiko <andriin@fb.com>


>  include/linux/bpf.h  |  1 +
>  kernel/bpf/syscall.c | 46 +++++++++++++++++++++++++++-----------------
>  2 files changed, 29 insertions(+), 18 deletions(-)
>

[...]
diff mbox series

Patch

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 3c659f36591d..4fcff4895f27 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1319,6 +1319,7 @@  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 e236a6c0aea4..a2ce46f4a987 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3969,40 +3969,50 @@  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)