libbpf: Open code raw_tp_open and link_create commands.

Open code raw_tracepoint_open and link_create used by light skeleton
to be able to avoid full libbpf eventually.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220131220528.98088-4-alexei.starovoitov@gmail.com

tools/bpf/bpftool/gen.c

@@ -381,13 +381,13 @@ static void codegen_attach_detach(struct bpf_object *obj, const char *obj_name)
 		switch (bpf_program__type(prog)) {
 		case BPF_PROG_TYPE_RAW_TRACEPOINT:
 			tp_name = strchr(bpf_program__section_name(prog), '/') + 1;
-			printf("\tint fd = bpf_raw_tracepoint_open(\"%s\", prog_fd);\n", tp_name);
+			printf("\tint fd = skel_raw_tracepoint_open(\"%s\", prog_fd);\n", tp_name);
 			break;
 		case BPF_PROG_TYPE_TRACING:
 			if (bpf_program__expected_attach_type(prog) == BPF_TRACE_ITER)
-				printf("\tint fd = bpf_link_create(prog_fd, 0, BPF_TRACE_ITER, NULL);\n");
+				printf("\tint fd = skel_link_create(prog_fd, 0, BPF_TRACE_ITER);\n");
 			else
-				printf("\tint fd = bpf_raw_tracepoint_open(NULL, prog_fd);\n");
+				printf("\tint fd = skel_raw_tracepoint_open(NULL, prog_fd);\n");
 			break;
 		default:
 			printf("\tint fd = ((void)prog_fd, 0); /* auto-attach not supported */\n");

tools/lib/bpf/skel_internal.h

@@ -110,6 +110,32 @@ static inline int skel_map_update_elem(int fd, const void *key,
 	return skel_sys_bpf(BPF_MAP_UPDATE_ELEM, &attr, attr_sz);
 }
 
+static inline int skel_raw_tracepoint_open(const char *name, int prog_fd)
+{
+	const size_t attr_sz = offsetofend(union bpf_attr, raw_tracepoint.prog_fd);
+	union bpf_attr attr;
+
+	memset(&attr, 0, attr_sz);
+	attr.raw_tracepoint.name = (long) name;
+	attr.raw_tracepoint.prog_fd = prog_fd;
+
+	return skel_sys_bpf(BPF_RAW_TRACEPOINT_OPEN, &attr, attr_sz);
+}
+
+static inline int skel_link_create(int prog_fd, int target_fd,
+				   enum bpf_attach_type attach_type)
+{
+	const size_t attr_sz = offsetofend(union bpf_attr, link_create.iter_info_len);
+	union bpf_attr attr;
+
+	memset(&attr, 0, attr_sz);
+	attr.link_create.prog_fd = prog_fd;
+	attr.link_create.target_fd = target_fd;
+	attr.link_create.attach_type = attach_type;
+
+	return skel_sys_bpf(BPF_LINK_CREATE, &attr, attr_sz);
+}
+
 static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts)
 {
 	int map_fd = -1, prog_fd = -1, key = 0, err;