selftests/bpf: Add tests for bpf_object__prepare

Add selftests, checking that running bpf_object__prepare successfully
creates maps before load step.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250303135752.158343-5-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/prog_tests/prepare.c

@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta */
+
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "prepare.skel.h"
+
+static bool check_prepared(struct bpf_object *obj)
+{
+	bool is_prepared = true;
+	const struct bpf_map *map;
+
+	bpf_object__for_each_map(map, obj) {
+		if (bpf_map__fd(map) < 0)
+			is_prepared = false;
+	}
+
+	return is_prepared;
+}
+
+static void test_prepare_no_load(void)
+{
+	struct prepare *skel;
+	int err;
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = &pkt_v4,
+		    .data_size_in = sizeof(pkt_v4),
+	);
+
+	skel = prepare__open();
+	if (!ASSERT_OK_PTR(skel, "prepare__open"))
+		return;
+
+	if (!ASSERT_FALSE(check_prepared(skel->obj), "not check_prepared"))
+		goto cleanup;
+
+	err = bpf_object__prepare(skel->obj);
+
+	if (!ASSERT_TRUE(check_prepared(skel->obj), "check_prepared"))
+		goto cleanup;
+
+	if (!ASSERT_OK(err, "bpf_object__prepare"))
+		goto cleanup;
+
+cleanup:
+	prepare__destroy(skel);
+}
+
+static void test_prepare_load(void)
+{
+	struct prepare *skel;
+	int err, prog_fd;
+	LIBBPF_OPTS(bpf_test_run_opts, topts,
+		    .data_in = &pkt_v4,
+		    .data_size_in = sizeof(pkt_v4),
+	);
+
+	skel = prepare__open();
+	if (!ASSERT_OK_PTR(skel, "prepare__open"))
+		return;
+
+	if (!ASSERT_FALSE(check_prepared(skel->obj), "not check_prepared"))
+		goto cleanup;
+
+	err = bpf_object__prepare(skel->obj);
+	if (!ASSERT_OK(err, "bpf_object__prepare"))
+		goto cleanup;
+
+	err = prepare__load(skel);
+	if (!ASSERT_OK(err, "prepare__load"))
+		goto cleanup;
+
+	if (!ASSERT_TRUE(check_prepared(skel->obj), "check_prepared"))
+		goto cleanup;
+
+	prog_fd = bpf_program__fd(skel->progs.program);
+	if (!ASSERT_GE(prog_fd, 0, "prog_fd"))
+		goto cleanup;
+
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	if (!ASSERT_OK(err, "test_run_opts err"))
+		goto cleanup;
+
+	if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
+		goto cleanup;
+
+	ASSERT_EQ(skel->bss->err, 0, "err");
+
+cleanup:
+	prepare__destroy(skel);
+}
+
+void test_prepare(void)
+{
+	if (test__start_subtest("prepare_load"))
+		test_prepare_load();
+	if (test__start_subtest("prepare_no_load"))
+		test_prepare_no_load();
+}

tools/testing/selftests/bpf/progs/prepare.c

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+//#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+int err;
+
+struct {
+	__uint(type, BPF_MAP_TYPE_RINGBUF);
+	__uint(max_entries, 4096);
+} ringbuf SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, __u32);
+} array_map SEC(".maps");
+
+SEC("cgroup_skb/egress")
+int program(struct __sk_buff *skb)
+{
+	err = 0;
+	return 0;
+}