Re: [PATCH bpf-next v4 3/3] selftests/bpf: Switches existing selftests to using open_opts for custom BTF

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng
<chengshuyi@linux.alibaba.com> wrote:
>
> This patch mainly replaces the bpf_object_load_attr of
> the core_autosize.c and core_reloc.c files with bpf_object_open_opts.
>
> Signed-off-by: Shuyi Cheng <chengshuyi@linux.alibaba.com>
> ---
>  .../selftests/bpf/prog_tests/core_autosize.c       | 22 ++++++++---------
>  .../testing/selftests/bpf/prog_tests/core_reloc.c  | 28 ++++++++++------------
>  2 files changed, 24 insertions(+), 26 deletions(-)
>

So I applied this, but it's obvious you haven't bothered even
*building* selftests, because it had at least one compilation warning
and one compilation *error*, not building test_progs at all. I've
noted stuff I fixed (and still remember) below. I understand it might
be your first kernel contribution, but it's not acceptable to submit
patches that don't build. Next time please be more thorough.

[...]

>
> -       load_attr.obj = skel->obj;
> -       load_attr.target_btf_path = btf_file;
> -       err = bpf_object__load_xattr(&load_attr);
> +       err = bpf_object__load(skel);

This didn't compile outright, because it should have been
test_core_autosize__load(skel).

>         if (!ASSERT_ERR(err, "bad_prog_load"))
>                 goto cleanup;
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
> index d02e064..10eb2407 100644
> --- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
> +++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
> @@ -816,7 +816,7 @@ static size_t roundup_page(size_t sz)
>  void test_core_reloc(void)
>  {
>         const size_t mmap_sz = roundup_page(sizeof(struct data));
> -       struct bpf_object_load_attr load_attr = {};
> +       struct bpf_object_open_opts open_opts = {};
>         struct core_reloc_test_case *test_case;
>         const char *tp_name, *probe_name;
>         int err, i, equal;
> @@ -846,9 +846,17 @@ void test_core_reloc(void)
>                                 continue;
>                 }
>
> -               obj = bpf_object__open_file(test_case->bpf_obj_file, NULL);
> +               if (test_case->btf_src_file) {
> +                       err = access(test_case->btf_src_file, R_OK);
> +                       if (!ASSERT_OK(err, "btf_src_file"))
> +                               goto cleanup;
> +               }
> +
> +               open_opts.btf_custom_path = test_case->btf_src_file;

This was reporting a valid warning about dropping const modifier. For
good reason, becyase btf_custom_path in open_opts should have been
`const char *`, I fixed that.

> +               open_opts.sz = sizeof(struct bpf_object_open_opts);
> +               obj = bpf_object__open_file(test_case->bpf_obj_file, &open_opts);
>                 if (!ASSERT_OK_PTR(obj, "obj_open"))
> -                       continue;
> +                       goto cleanup;
>
>                 probe_name = "raw_tracepoint/sys_enter";
>                 tp_name = "sys_enter";

[...]