netdev - Re: [PATCH v5 bpf-next 3/3] selftests/bpf: add raw_tp_test

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Date:   Fri, 25 Sep 2020 10:31:29 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Song Liu <songliubraving@...com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kernel Team <kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH v5 bpf-next 3/3] selftests/bpf: add raw_tp_test_run

On Thu, Sep 24, 2020 at 4:03 PM Song Liu <songliubraving@...com> wrote:
>
> This test runs test_run for raw_tracepoint program. The test covers ctx
> input, retval output, and running on correct cpu.
>
> Signed-off-by: Song Liu <songliubraving@...com>
> ---

Few suggestions below, but overall looks good to me:

Acked-by: Andrii Nakryiko <andriin@...com>

>  .../bpf/prog_tests/raw_tp_test_run.c          | 98 +++++++++++++++++++
>  .../bpf/progs/test_raw_tp_test_run.c          | 24 +++++
>  2 files changed, 122 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/raw_tp_test_run.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_raw_tp_test_run.c
>

[...]

> +
> +       err = bpf_prog_test_run_xattr(&test_attr);
> +       CHECK(err == 0, "test_run", "should fail for too small ctx\n");
> +
> +       test_attr.ctx_size_in = sizeof(args);
> +       err = bpf_prog_test_run_xattr(&test_attr);
> +       CHECK(err < 0, "test_run", "err %d\n", errno);
> +       CHECK(test_attr.retval != expected_retval, "check_retval",
> +             "expect 0x%x, got 0x%x\n", expected_retval, test_attr.retval);
> +
> +       for (i = 0; i < nr_online; i++) {
> +               if (online[i]) {

if (!online[i])
    continue;

That will reduce nestedness by one level

> +                       DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
> +                               .ctx_in = args,
> +                               .ctx_size_in = sizeof(args),
> +                               .flags = BPF_F_TEST_RUN_ON_CPU,
> +                               .retval = 0,
> +                               .cpu = i,
> +                       );

this declares variable, so should be at the top of the lexical scope


> +
> +                       err = bpf_prog_test_run_opts(prog_fd, &opts);
> +                       CHECK(err < 0, "test_run_opts", "err %d\n", errno);
> +                       CHECK(skel->data->on_cpu != i, "check_on_cpu",
> +                             "expect %d got %d\n", i, skel->data->on_cpu);
> +                       CHECK(opts.retval != expected_retval,
> +                             "check_retval", "expect 0x%x, got 0x%x\n",
> +                             expected_retval, opts.retval);
> +
> +                       if (i == 0) {

I agree that this looks a bit obscure. You can still re-use
DECLARE_LIBBPF_OPTS, just move it outside the loop. And then you can
just modify it in place to adjust to a particular case. And in log
output, we'll see 30+ similar success messages for the else branch,
which is indeed unnecessary.

> +                               /* invalid cpu ID should fail with ENXIO */
> +                               opts.cpu = 0xffffffff;
> +                               err = bpf_prog_test_run_opts(prog_fd, &opts);
> +                               CHECK(err != -1 || errno != ENXIO,
> +                                     "test_run_opts_fail",
> +                                     "should failed with ENXIO\n");
> +                       } else {
> +                               /* non-zero cpu w/o BPF_F_TEST_RUN_ON_CPU
> +                                * should fail with EINVAL
> +                                */
> +                               opts.flags = 0;
> +                               err = bpf_prog_test_run_opts(prog_fd, &opts);
> +                               CHECK(err != -1 || errno != EINVAL,
> +                                     "test_run_opts_fail",
> +                                     "should failed with EINVAL\n");
> +                       }
> +               }
> +       }

[...]