netdev - Re: [PATCH bpf-next v5 8/8] selftests/bpf: Adding test for arg dereference in extension trace

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Date:   Wed, 16 Sep 2020 13:44:55 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        KP Singh <kpsingh@...omium.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v5 8/8] selftests/bpf: Adding test for arg
 dereference in extension trace

On Tue, Sep 15, 2020 at 5:50 PM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> From: Jiri Olsa <jolsa@...nel.org>
>
> Adding test that setup following program:
>
>   SEC("classifier/test_pkt_md_access")
>   int test_pkt_md_access(struct __sk_buff *skb)
>
> with its extension:
>
>   SEC("freplace/test_pkt_md_access")
>   int test_pkt_md_access_new(struct __sk_buff *skb)
>
> and tracing that extension with:
>
>   SEC("fentry/test_pkt_md_access_new")
>   int BPF_PROG(fentry, struct sk_buff *skb)
>
> The test verifies that the tracing program can
> dereference skb argument properly.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---

Looks good, with a minor CHECK() complaint below.

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

>  tools/testing/selftests/bpf/prog_tests/trace_ext.c |  113 ++++++++++++++++++++
>  tools/testing/selftests/bpf/progs/test_trace_ext.c |   18 +++
>  .../selftests/bpf/progs/test_trace_ext_tracing.c   |   25 ++++
>  3 files changed, 156 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/trace_ext.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_trace_ext.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_trace_ext_tracing.c
>

[...]

> +       err = test_trace_ext_tracing__attach(skel_trace);
> +       if (CHECK(err, "setup", "tracing/test_pkt_md_access_new attach failed: %d\n", err))
> +               goto cleanup;
> +
> +       /* trigger the test */
> +       err = bpf_prog_test_run(pkt_fd, 1, &pkt_v4, sizeof(pkt_v4),
> +                               NULL, NULL, &retval, &duration);
> +       CHECK(err || retval, "",

please don't use empty string here

> +             "err %d errno %d retval %d duration %d\n",
> +             err, errno, retval, duration);

who and why cares about duration here?..

> +
> +       bss_ext = skel_ext->bss;
> +       bss_trace = skel_trace->bss;
> +
> +       len = bss_ext->ext_called;
> +
> +       CHECK(bss_ext->ext_called == 0,
> +               "check", "failed to trigger freplace/test_pkt_md_access\n");
> +       CHECK(bss_trace->fentry_called != len,
> +               "check", "failed to trigger fentry/test_pkt_md_access_new\n");
> +       CHECK(bss_trace->fexit_called != len,
> +               "check", "failed to trigger fexit/test_pkt_md_access_new\n");
> +
> +cleanup:
> +       test_trace_ext_tracing__destroy(skel_trace);
> +       test_trace_ext__destroy(skel_ext);
> +       test_pkt_md_access__destroy(skel_pkt);
> +}

[...]