bpf: Add support for BPF_OBJ_GET_INFO_BY_FD for bpf_link

Add ability to fetch bpf_link details through BPF_OBJ_GET_INFO_BY_FD command.
Also enhance show_fdinfo to potentially include bpf_link type-specific
information (similarly to obj_info).

Also introduce enum bpf_link_type stored in bpf_link itself and expose it in
UAPI. bpf_link_tracing also now will store and return bpf_attach_type.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200429001614.1544-5-andriin@fb.com

4 files changed, 41 insertions, 3 deletions

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index a9cb9a5bf8e9..272626cc3fc9 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -57,8 +57,6 @@ struct bpf_cgroup_link {
 	enum bpf_attach_type type;
 };
 
-extern const struct bpf_link_ops bpf_cgroup_link_lops;
-
 struct bpf_prog_list {
 	struct list_head node;
 	struct bpf_prog *prog;
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 875d1f0af803..c07b1d2f3824 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1026,9 +1026,11 @@ extern const struct file_operations bpf_prog_fops;
 	extern const struct bpf_verifier_ops _name ## _verifier_ops;
 #define BPF_MAP_TYPE(_id, _ops) \
 	extern const struct bpf_map_ops _ops;
+#define BPF_LINK_TYPE(_id, _name)
 #include <linux/bpf_types.h>
 #undef BPF_PROG_TYPE
 #undef BPF_MAP_TYPE
+#undef BPF_LINK_TYPE
 
 extern const struct bpf_prog_ops bpf_offload_prog_ops;
 extern const struct bpf_verifier_ops tc_cls_act_analyzer_ops;
@@ -1086,6 +1088,7 @@ int bpf_prog_new_fd(struct bpf_prog *prog);
 struct bpf_link {
 	atomic64_t refcnt;
 	u32 id;
+	enum bpf_link_type type;
 	const struct bpf_link_ops *ops;
 	struct bpf_prog *prog;
 	struct work_struct work;
@@ -1103,9 +1106,12 @@ struct bpf_link_ops {
 	void (*dealloc)(struct bpf_link *link);
 	int (*update_prog)(struct bpf_link *link, struct bpf_prog *new_prog,
 			   struct bpf_prog *old_prog);
+	void (*show_fdinfo)(const struct bpf_link *link, struct seq_file *seq);
+	int (*fill_link_info)(const struct bpf_link *link,
+			      struct bpf_link_info *info);
 };
 
-void bpf_link_init(struct bpf_link *link,
+void bpf_link_init(struct bpf_link *link, enum bpf_link_type type,
 		   const struct bpf_link_ops *ops, struct bpf_prog *prog);
 int bpf_link_prime(struct bpf_link *link, struct bpf_link_primer *primer);
 int bpf_link_settle(struct bpf_link_primer *primer);
diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h
index ba0c2d56f8a3..8345cdf553b8 100644
--- a/include/linux/bpf_types.h
+++ b/include/linux/bpf_types.h
@@ -118,3 +118,9 @@ BPF_MAP_TYPE(BPF_MAP_TYPE_STACK, stack_map_ops)
 #if defined(CONFIG_BPF_JIT)
 BPF_MAP_TYPE(BPF_MAP_TYPE_STRUCT_OPS, bpf_struct_ops_map_ops)
 #endif
+
+BPF_LINK_TYPE(BPF_LINK_TYPE_RAW_TRACEPOINT, raw_tracepoint)
+BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing)
+#ifdef CONFIG_CGROUP_BPF
+BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup)
+#endif
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7e6541fceade..0eccafae55bb 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -222,6 +222,15 @@ enum bpf_attach_type {
 
 #define MAX_BPF_ATTACH_TYPE __MAX_BPF_ATTACH_TYPE
 
+enum bpf_link_type {
+	BPF_LINK_TYPE_UNSPEC = 0,
+	BPF_LINK_TYPE_RAW_TRACEPOINT = 1,
+	BPF_LINK_TYPE_TRACING = 2,
+	BPF_LINK_TYPE_CGROUP = 3,
+
+	MAX_BPF_LINK_TYPE,
+};
+
 /* cgroup-bpf attach flags used in BPF_PROG_ATTACH command
  *
  * NONE(default): No further bpf programs allowed in the subtree.
@@ -3612,6 +3621,25 @@ struct bpf_btf_info {
 	__u32 id;
 } __attribute__((aligned(8)));
 
+struct bpf_link_info {
+	__u32 type;
+	__u32 id;
+	__u32 prog_id;
+	union {
+		struct {
+			__aligned_u64 tp_name; /* in/out: tp_name buffer ptr */
+			__u32 tp_name_len;     /* in/out: tp_name buffer len */
+		} raw_tracepoint;
+		struct {
+			__u32 attach_type;
+		} tracing;
+		struct {
+			__u64 cgroup_id;
+			__u32 attach_type;
+		} cgroup;
+	};
+} __attribute__((aligned(8)));
+
 /* User bpf_sock_addr struct to access socket fields and sockaddr struct passed
  * by user and intended to be used by socket (e.g. to bind to, depends on
  * attach attach type).