Re: [PATCH bpf-next 5/5] selftests/bpf: test return value handling for struct_ops prog

[Hou Tao <houtao1@huawei.com>]

Hi,

On 9/29/2021 7:19 AM, Andrii Nakryiko wrote:
> On Mon, Sep 27, 2021 at 7:38 PM Hou Tao <houtao1@huawei.com> wrote:
>> Running a BPF_PROG_TYPE_STRUCT_OPS prog for dummy_st_ops::init()
>> through bpf_prog_test_run(). Three test cases are added:
>> (1) attach dummy_st_ops should fail
>> (2) function return value of bpf_dummy_ops::init() is expected
>> (3) pointer argument of bpf_dummy_ops::init() works as expected
>>
>> Signed-off-by: Hou Tao <houtao1@huawei.com>
>> ---
>>  .../selftests/bpf/prog_tests/dummy_st_ops.c   | 81 +++++++++++++++++++
>>  .../selftests/bpf/progs/dummy_st_ops.c        | 33 ++++++++
>>  2 files changed, 114 insertions(+)
>>  create mode 100644 tools/testing/selftests/bpf/prog_tests/dummy_st_ops.c
>>  create mode 100644 tools/testing/selftests/bpf/progs/dummy_st_ops.c
>>
>> diff --git a/tools/testing/selftests/bpf/prog_tests/dummy_st_ops.c b/tools/testing/selftests/bpf/prog_tests/dummy_st_ops.c
>> new file mode 100644
>> index 000000000000..4b1b52b847e6
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/dummy_st_ops.c
>> @@ -0,0 +1,81 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (C) 2021. Huawei Technologies Co., Ltd */
>> +#include <test_progs.h>
>> +#include "dummy_st_ops.skel.h"
>> +
>> +/* Need to keep consistent with definitions in include/linux/bpf_dummy_ops.h */
>> +struct bpf_dummy_ops_state {
>> +       int val;
>> +};
>> +
>> +static void test_dummy_st_ops_attach(void)
>> +{
>> +       struct dummy_st_ops *skel;
>> +       struct bpf_link *link;
>> +
>> +       skel = dummy_st_ops__open_and_load();
>> +       if (!ASSERT_OK_PTR(skel, "dummy_st_ops_load"))
>> +               goto out;
> no need for __destroy() as we haven't created skeleton, so this could
> be just a return
Will do.
>> +
>> +       link = bpf_map__attach_struct_ops(skel->maps.dummy_1);
>> +       if (!ASSERT_EQ(libbpf_get_error(link), -EOPNOTSUPP,
>> +                      "dummy_st_ops_attach"))
>> +               goto out;
> nit: unless you expect to add something here soon, probably doing
> ASSERT_EQ() and let it fall through to out: and destroy would be a bit
> more readable
Make sense. Will do.
>
>> +out:
>> +       dummy_st_ops__destroy(skel);
>> +}
>> +
>> +static void test_dummy_init_ret_value(void)
>> +{
>> +       struct dummy_st_ops *skel;
>> +       int err, fd;
>> +       __u32 duration = 0, retval = 0;
>> +
>> +       skel = dummy_st_ops__open_and_load();
>> +       if (!ASSERT_OK_PTR(skel, "dummy_st_ops_load"))
>> +               goto out;
> same, just return is fine and no need for out: label
OK. Will do in v2.
>> +
>> +       fd = bpf_program__fd(skel->progs.init_1);
>> +       err = bpf_prog_test_run(fd, 1, NULL, 0,
>> +                               NULL, NULL, &retval, &duration);
>> +       ASSERT_OK(err, "test_run");
>> +       ASSERT_EQ(retval, 0xf2f3f4f5, "test_ret");
>> +out:
>> +       dummy_st_ops__destroy(skel);
>> +}
>> +
>> +static void test_dummy_init_ptr_arg(void)
>> +{
>> +       struct dummy_st_ops *skel;
>> +       int err, fd;
>> +       __u32 duration = 0, retval = 0;
>> +       struct bpf_dummy_ops_state in_state, out_state;
>> +       __u32 state_size;
>> +
>> +       skel = dummy_st_ops__open_and_load();
>> +       if (!ASSERT_OK_PTR(skel, "dummy_st_ops_load"))
>> +               goto out;
> here as well
OK. Will do.
>
>> +
>> +       fd = bpf_program__fd(skel->progs.init_1);
>> +       memset(&in_state, 0, sizeof(in_state));
>> +       in_state.val = 0xbeef;
>> +       memset(&out_state, 0, sizeof(out_state));
>> +       err = bpf_prog_test_run(fd, 1, &in_state, sizeof(in_state),
>> +                               &out_state, &state_size, &retval, &duration);
>> +       ASSERT_OK(err, "test_run");
>> +       ASSERT_EQ(state_size, sizeof(out_state), "test_data_out");
>> +       ASSERT_EQ(out_state.val, 0x5a, "test_ptr_ret");
>> +       ASSERT_EQ(retval, in_state.val, "test_ret");
>> +out:
>> +       dummy_st_ops__destroy(skel);
>> +}
>> +
>> +void test_dummy_st_ops(void)
>> +{
>> +       if (test__start_subtest("dummy_st_ops_attach"))
>> +               test_dummy_st_ops_attach();
>> +       if (test__start_subtest("dummy_init_ret_value"))
>> +               test_dummy_init_ret_value();
>> +       if (test__start_subtest("dummy_init_ptr_arg"))
>> +               test_dummy_init_ptr_arg();
>> +}
>> diff --git a/tools/testing/selftests/bpf/progs/dummy_st_ops.c b/tools/testing/selftests/bpf/progs/dummy_st_ops.c
>> new file mode 100644
>> index 000000000000..133c328f082a
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/dummy_st_ops.c
>> @@ -0,0 +1,33 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (C) 2021. Huawei Technologies Co., Ltd */
>> +#include <linux/bpf.h>
>> +#include <bpf/bpf_helpers.h>
>> +#include <bpf/bpf_tracing.h>
>> +
>> +struct bpf_dummy_ops_state {
>> +       int val;
>> +} __attribute__((preserve_access_index));
>> +
>> +struct bpf_dummy_ops {
>> +       int (*init)(struct bpf_dummy_ops_state *state);
>> +};
>> +
>> +char _liencse[] SEC("license") = "GPL";
> typo: _license (but it doesn't matter to libbpf, it looks at the
> section name only
Will fix.
>
>> +
>> +SEC("struct_ops/init_1")
>> +int BPF_PROG(init_1, struct bpf_dummy_ops_state *state)
>> +{
>> +       int ret;
>> +
>> +       if (!state)
>> +               return 0xf2f3f4f5;
>> +
>> +       ret = state->val;
>> +       state->val = 0x5a;
>> +       return ret;
>> +}
>> +
>> +SEC(".struct_ops")
>> +struct bpf_dummy_ops dummy_1 = {
>> +       .init = (void *)init_1,
>> +};
>> --
>> 2.29.2
>>
> .