4 files changed, 48 insertions, 24 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9be88a90a4aa..6ae748f6ea11 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2518,7 +2518,7 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
 	return 0;
 }
 
-static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
+static bool prog_needs_vmlinux_btf(struct bpf_program *prog)
 {
 	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
 	    prog->type == BPF_PROG_TYPE_LSM)
@@ -2533,37 +2533,43 @@ static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
 	return false;
 }
 
-static int bpf_object__load_vmlinux_btf(struct bpf_object *obj)
+static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
 {
-	bool need_vmlinux_btf = false;
 	struct bpf_program *prog;
-	int i, err;
+	int i;
 
 	/* CO-RE relocations need kernel BTF */
 	if (obj->btf_ext && obj->btf_ext->core_relo_info.len)
-		need_vmlinux_btf = true;
+		return true;
 
 	/* Support for typed ksyms needs kernel BTF */
 	for (i = 0; i < obj->nr_extern; i++) {
 		const struct extern_desc *ext;
 
 		ext = &obj->externs[i];
-		if (ext->type == EXT_KSYM && ext->ksym.type_id) {
-			need_vmlinux_btf = true;
-			break;
-		}
+		if (ext->type == EXT_KSYM && ext->ksym.type_id)
+			return true;
 	}
 
 	bpf_object__for_each_program(prog, obj) {
 		if (!prog->load)
 			continue;
-		if (libbpf_prog_needs_vmlinux_btf(prog)) {
-			need_vmlinux_btf = true;
-			break;
-		}
+		if (prog_needs_vmlinux_btf(prog))
+			return true;
 	}
 
-	if (!need_vmlinux_btf)
+	return false;
+}
+
+static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
+{
+	int err;
+
+	/* btf_vmlinux could be loaded earlier */
+	if (obj->btf_vmlinux)
+		return 0;
+
+	if (!force && !obj_needs_vmlinux_btf(obj))
 		return 0;
 
 	obj->btf_vmlinux = libbpf_find_kernel_btf();
@@ -7475,7 +7481,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 	}
 
 	err = bpf_object__probe_loading(obj);
-	err = err ? : bpf_object__load_vmlinux_btf(obj);
+	err = err ? : bpf_object__load_vmlinux_btf(obj, false);
 	err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
 	err = err ? : bpf_object__sanitize_and_load_btf(obj);
 	err = err ? : bpf_object__sanitize_maps(obj);
@@ -10870,23 +10876,33 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
 				   int attach_prog_fd,
 				   const char *attach_func_name)
 {
-	int btf_id;
+	int btf_obj_fd = 0, btf_id = 0, err;
 
 	if (!prog || attach_prog_fd < 0 || !attach_func_name)
 		return -EINVAL;
 
-	if (attach_prog_fd)
+	if (prog->obj->loaded)
+		return -EINVAL;
+
+	if (attach_prog_fd) {
 		btf_id = libbpf_find_prog_btf_id(attach_func_name,
 						 attach_prog_fd);
-	else
-		btf_id = libbpf_find_vmlinux_btf_id(attach_func_name,
-						    prog->expected_attach_type);
-
-	if (btf_id < 0)
-		return btf_id;
+		if (btf_id < 0)
+			return btf_id;
+	} else {
+		/* load btf_vmlinux, if not yet */
+		err = bpf_object__load_vmlinux_btf(prog->obj, true);
+		if (err)
+			return err;
+		err = find_kernel_btf_id(prog->obj, attach_func_name,
+					 prog->expected_attach_type,
+					 &btf_obj_fd, &btf_id);
+		if (err)
+			return err;
+	}
 
 	prog->attach_btf_id = btf_id;
-	prog->attach_btf_obj_fd = 0;
+	prog->attach_btf_obj_fd = btf_obj_fd;
 	prog->attach_prog_fd = attach_prog_fd;
 	return 0;
 }
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 6909ee81113a..3c35eb401931 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -536,6 +536,7 @@ LIBBPF_API int ring_buffer__add(struct ring_buffer *rb, int map_fd,
 				ring_buffer_sample_fn sample_cb, void *ctx);
 LIBBPF_API int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms);
 LIBBPF_API int ring_buffer__consume(struct ring_buffer *rb);
+LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
 
 /* Perf buffer APIs */
 struct perf_buffer;
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 7c4126542e2b..1c0fd2dd233a 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -346,6 +346,7 @@ LIBBPF_0.3.0 {
 		btf__parse_split;
 		btf__new_empty_split;
 		btf__new_split;
+		ring_buffer__epoll_fd;
 		xsk_setup_xdp_prog;
 		xsk_socket__update_xskmap;
 } LIBBPF_0.2.0;
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 98537ff2679e..8caaafe7e312 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -282,3 +282,9 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
 	}
 	return cnt < 0 ? -errno : res;
 }
+
+/* Get an fd that can be used to sleep until data is available in the ring(s) */
+int ring_buffer__epoll_fd(const struct ring_buffer *rb)
+{
+	return rb->epoll_fd;
+}