Commit 0623e733 authored by Kui-Feng Lee's avatar Kui-Feng Lee Committed by Andrii Nakryiko
Browse files

selftests/bpf: Test if shadow types work correctly. 



Change the values of fields, including scalar types and function pointers,
and check if the struct_ops map works as expected.

The test changes the field "test_2" of "testmod_1" from the pointer to
test_2() to pointer to test_3() and the field "data" to 13. The function
test_2() and test_3() both compute a new value for "test_2_result", but in
different way. By checking the value of "test_2_result", it ensures the
struct_ops map works as expected with changes through shadow types.

Signed-off-by: default avatarKui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240229064523.2091270-6-thinker.li@gmail.com
parent f2e81192

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

+10 −1
Original line number Diff line number Diff line
@@ -539,6 +539,15 @@ static int bpf_testmod_ops_init_member(const struct btf_type *t, 
				       const struct btf_member *member,

				       void *kdata, const void *udata)

{

	if (member->offset == offsetof(struct bpf_testmod_ops, data) * 8) {

		/* For data fields, this function has to copy it and return

		 * 1 to indicate that the data has been handled by the

		 * struct_ops type, or the verifier will reject the map if

		 * the value of the data field is not zero.

		 */

		((struct bpf_testmod_ops *)kdata)->data = ((struct bpf_testmod_ops *)udata)->data;

		return 1;

	}

	return 0;

}
@@ -559,7 +568,7 @@ static int bpf_dummy_reg(void *kdata) 
	 * initialized, so we need to check for NULL.

	 */

	if (ops->test_2)

		ops->test_2(4, 3);

		ops->test_2(4, ops->data);



	return 0;

}

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

+8 −0
Original line number Diff line number Diff line
@@ -35,6 +35,14 @@ struct bpf_testmod_ops { 
	void (*test_2)(int a, int b);

	/* Used to test nullable arguments. */

	int (*test_maybe_null)(int dummy, struct task_struct *task);



	/* The following fields are used to test shadow copies. */

	char onebyte;

	struct {

		int a;

		int b;

	} unsupported;

	int data;

};



#endif /* _BPF_TESTMOD_H */

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

+15 −4
Original line number Diff line number Diff line
@@ -32,17 +32,23 @@ static void check_map_info(struct bpf_map_info *info) 


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);

	skel = struct_ops_module__open();

	if (!ASSERT_OK_PTR(skel, "struct_ops_module_open"))

		return;



	skel->struct_ops.testmod_1->data = 13;

	skel->struct_ops.testmod_1->test_2 = skel->progs.test_3;

	/* Since test_2() is not being used, it should be disabled from

	 * auto-loading, or it will fail to load.

	 */

	bpf_program__set_autoload(skel->progs.test_2, false);



	err = struct_ops_module__load(skel);

	if (!ASSERT_OK(err, "struct_ops_module_load"))

		goto cleanup;
@@ -56,8 +62,13 @@ static void test_struct_ops_load(void) 
	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");

	/* test_3() will be called from bpf_dummy_reg() in bpf_testmod.c

	 *

	 * In bpf_testmod.c it will pass 4 and 13 (the value of data) to

	 * .test_2.  So, the value of test_2_result should be 20 (4 + 13 +

	 * 3).

	 */

	ASSERT_EQ(skel->bss->test_2_result, 20, "check_shadow_variables");



	bpf_link__destroy(link);

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

+8 −0
Original line number Diff line number Diff line
@@ -21,9 +21,17 @@ void BPF_PROG(test_2, int a, int b) 
	test_2_result = a + b;

}



SEC("struct_ops/test_3")

int BPF_PROG(test_3, int a, int b)

{

	test_2_result = a + b + 3;

	return a + b + 3;

}



SEC(".struct_ops.link")

struct bpf_testmod_ops testmod_1 = {

	.test_1 = (void *)test_1,

	.test_2 = (void *)test_2,

	.data = 0x1,

};