selftests/bpf: test case for register_bpf_struct_ops().

Create a new struct_ops type called bpf_testmod_ops within the bpf_testmod
module. When a struct_ops object is registered, the bpf_testmod module will
invoke test_2 from the module.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240119225005.668602-15-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2020 Facebook */
+#include <linux/bpf.h>
 #include <linux/btf.h>
 #include <linux/btf_ids.h>
 #include <linux/delay.h>
@@ -521,11 +522,75 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_test_static_unused_arg)
 BTF_ID_FLAGS(func, bpf_kfunc_call_test_offset)
 BTF_SET8_END(bpf_testmod_check_kfunc_ids)
 
+static int bpf_testmod_ops_init(struct btf *btf)
+{
+	return 0;
+}
+
+static bool bpf_testmod_ops_is_valid_access(int off, int size,
+					    enum bpf_access_type type,
+					    const struct bpf_prog *prog,
+					    struct bpf_insn_access_aux *info)
+{
+	return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
+}
+
+static int bpf_testmod_ops_init_member(const struct btf_type *t,
+				       const struct btf_member *member,
+				       void *kdata, const void *udata)
+{
+	return 0;
+}
+
 static const struct btf_kfunc_id_set bpf_testmod_kfunc_set = {
 	.owner = THIS_MODULE,
 	.set   = &bpf_testmod_check_kfunc_ids,
 };
 
+static const struct bpf_verifier_ops bpf_testmod_verifier_ops = {
+	.is_valid_access = bpf_testmod_ops_is_valid_access,
+};
+
+static int bpf_dummy_reg(void *kdata)
+{
+	struct bpf_testmod_ops *ops = kdata;
+	int r;
+
+	r = ops->test_2(4, 3);
+
+	return 0;
+}
+
+static void bpf_dummy_unreg(void *kdata)
+{
+}
+
+static int bpf_testmod_test_1(void)
+{
+	return 0;
+}
+
+static int bpf_testmod_test_2(int a, int b)
+{
+	return 0;
+}
+
+static struct bpf_testmod_ops __bpf_testmod_ops = {
+	.test_1 = bpf_testmod_test_1,
+	.test_2 = bpf_testmod_test_2,
+};
+
+struct bpf_struct_ops bpf_bpf_testmod_ops = {
+	.verifier_ops = &bpf_testmod_verifier_ops,
+	.init = bpf_testmod_ops_init,
+	.init_member = bpf_testmod_ops_init_member,
+	.reg = bpf_dummy_reg,
+	.unreg = bpf_dummy_unreg,
+	.cfi_stubs = &__bpf_testmod_ops,
+	.name = "bpf_testmod_ops",
+	.owner = THIS_MODULE,
+};
+
 extern int bpf_fentry_test1(int a);
 
 static int bpf_testmod_init(void)
@@ -536,6 +601,7 @@ static int bpf_testmod_init(void)
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_testmod_kfunc_set);
 	ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_testmod_kfunc_set);
+	ret = ret ?: register_bpf_struct_ops(&bpf_bpf_testmod_ops, bpf_testmod_ops);
 	if (ret < 0)
 		return ret;
 	if (bpf_fentry_test1(0) < 0)

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.h

@@ -28,4 +28,9 @@ struct bpf_iter_testmod_seq {
 	int cnt;
 };
 
+struct bpf_testmod_ops {
+	int (*test_1)(void);
+	int (*test_2)(int a, int b);
+};
+
 #endif /* _BPF_TESTMOD_H */

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

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <test_progs.h>
+#include <time.h>
+
+#include "struct_ops_module.skel.h"
+
+static void check_map_info(struct bpf_map_info *info)
+{
+	struct bpf_btf_info btf_info;
+	char btf_name[256];
+	u32 btf_info_len = sizeof(btf_info);
+	int err, fd;
+
+	fd = bpf_btf_get_fd_by_id(info->btf_vmlinux_id);
+	if (!ASSERT_GE(fd, 0, "get_value_type_btf_obj_fd"))
+		return;
+
+	memset(&btf_info, 0, sizeof(btf_info));
+	btf_info.name = ptr_to_u64(btf_name);
+	btf_info.name_len = sizeof(btf_name);
+	err = bpf_btf_get_info_by_fd(fd, &btf_info, &btf_info_len);
+	if (!ASSERT_OK(err, "get_value_type_btf_obj_info"))
+		goto cleanup;
+
+	if (!ASSERT_EQ(strcmp(btf_name, "bpf_testmod"), 0, "get_value_type_btf_obj_name"))
+		goto cleanup;
+
+cleanup:
+	close(fd);
+}
+
+static void test_struct_ops_load(void)
+{
+	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts);
+	struct struct_ops_module *skel;
+	struct bpf_map_info info = {};
+	struct bpf_link *link;
+	int err;
+	u32 len;
+
+	skel = struct_ops_module__open_opts(&opts);
+	if (!ASSERT_OK_PTR(skel, "struct_ops_module_open"))
+		return;
+
+	err = struct_ops_module__load(skel);
+	if (!ASSERT_OK(err, "struct_ops_module_load"))
+		goto cleanup;
+
+	len = sizeof(info);
+	err = bpf_map_get_info_by_fd(bpf_map__fd(skel->maps.testmod_1), &info,
+				     &len);
+	if (!ASSERT_OK(err, "bpf_map_get_info_by_fd"))
+		goto cleanup;
+
+	link = bpf_map__attach_struct_ops(skel->maps.testmod_1);
+	ASSERT_OK_PTR(link, "attach_test_mod_1");
+
+	/* test_2() will be called from bpf_dummy_reg() in bpf_testmod.c */
+	ASSERT_EQ(skel->bss->test_2_result, 7, "test_2_result");
+
+	bpf_link__destroy(link);
+
+	check_map_info(&info);
+
+cleanup:
+	struct_ops_module__destroy(skel);
+}
+
+void serial_test_struct_ops_module(void)
+{
+	if (test__start_subtest("test_struct_ops_load"))
+		test_struct_ops_load();
+}
+

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

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "../bpf_testmod/bpf_testmod.h"
+
+char _license[] SEC("license") = "GPL";
+
+int test_2_result = 0;
+
+SEC("struct_ops/test_1")
+int BPF_PROG(test_1)
+{
+	return 0xdeadbeef;
+}
+
+SEC("struct_ops/test_2")
+int BPF_PROG(test_2, int a, int b)
+{
+	test_2_result = a + b;
+	return a + b;
+}
+
+SEC(".struct_ops.link")
+struct bpf_testmod_ops testmod_1 = {
+	.test_1 = (void *)test_1,
+	.test_2 = (void *)test_2,
+};
+