netdev - Re: [PATCH bpf-next] selftests/bpf: make libbpf_probe_prog_types testcase aware of kernel configuration

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Date:   Fri, 30 Sep 2022 16:06:41 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Artem Savkov <asavkov@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        jbenc@...hat.com
Subject: Re: [PATCH bpf-next] selftests/bpf: make libbpf_probe_prog_types
 testcase aware of kernel configuration

On Fri, Sep 30, 2022 at 4:09 AM Artem Savkov <asavkov@...hat.com> wrote:
>
> At the moment libbpf_probe_prog_types test iterates over all available
> BPF_PROG_TYPE regardless of kernel configuration which can exclude some
> of those. Unfortunately there is no direct way to tell which types are
> available, but we can look at struct bpf_ctx_onvert to tell which ones
> are available.
>
> Signed-off-by: Artem Savkov <asavkov@...hat.com>
> ---

Many selftests assume correct kernel configuration which is encoded in
config and config.<arch> files. So it seems fair to assume that all
defined program types are available on kernel-under-test.

If someone is running selftests under custom more minimal kernel they
can use denylist to ignore specific prog type subtests?


>  .../selftests/bpf/prog_tests/libbpf_probes.c  | 33 +++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/libbpf_probes.c b/tools/testing/selftests/bpf/prog_tests/libbpf_probes.c
> index 9f766ddd946ab..753ddf79cf5e0 100644
> --- a/tools/testing/selftests/bpf/prog_tests/libbpf_probes.c
> +++ b/tools/testing/selftests/bpf/prog_tests/libbpf_probes.c
> @@ -4,12 +4,29 @@
>  #include <test_progs.h>
>  #include <bpf/btf.h>
>
> +static int find_type_in_ctx_convert(struct btf *btf,
> +                                   const char *prog_type_name,
> +                                   const struct btf_type *t)
> +{
> +       const struct btf_member *m;
> +       size_t cmplen = strlen(prog_type_name);
> +       int i, n;
> +
> +       for (m = btf_members(t), i = 0, n = btf_vlen(t); i < n; m++, i++) {
> +               const char *member_name = btf__str_by_offset(btf, m->name_off);
> +
> +               if (!strncmp(prog_type_name, member_name, cmplen))
> +                       return 1;
> +       }
> +       return 0;
> +}
> +
>  void test_libbpf_probe_prog_types(void)
>  {
>         struct btf *btf;
> -       const struct btf_type *t;
> +       const struct btf_type *t, *context_convert_t;
>         const struct btf_enum *e;
> -       int i, n, id;
> +       int i, n, id, context_convert_id;
>
>         btf = btf__parse("/sys/kernel/btf/vmlinux", NULL);
>         if (!ASSERT_OK_PTR(btf, "btf_parse"))
> @@ -23,6 +40,14 @@ void test_libbpf_probe_prog_types(void)
>         if (!ASSERT_OK_PTR(t, "bpf_prog_type_enum"))
>                 goto cleanup;
>
> +       context_convert_id = btf__find_by_name_kind(btf, "bpf_ctx_convert",
> +                                                   BTF_KIND_STRUCT);
> +       if (!ASSERT_GT(context_convert_id, 0, "bpf_ctx_convert_id"))
> +               goto cleanup;
> +       context_convert_t = btf__type_by_id(btf, context_convert_id);
> +       if (!ASSERT_OK_PTR(t, "bpf_ctx_convert_type"))
> +               goto cleanup;
> +
>         for (e = btf_enum(t), i = 0, n = btf_vlen(t); i < n; e++, i++) {
>                 const char *prog_type_name = btf__str_by_offset(btf, e->name_off);
>                 enum bpf_prog_type prog_type = (enum bpf_prog_type)e->val;
> @@ -31,6 +56,10 @@ void test_libbpf_probe_prog_types(void)
>                 if (prog_type == BPF_PROG_TYPE_UNSPEC)
>                         continue;
>
> +               if (!find_type_in_ctx_convert(btf, prog_type_name,
> +                                             context_convert_t))
> +                       continue;
> +
>                 if (!test__start_subtest(prog_type_name))
>                         continue;
>
> --
> 2.37.3
>