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

[Shuyi Cheng]

On 7/17/21 4:27 AM, Andrii Nakryiko wrote:
> On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng
> <chengshuyi@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
> > ---
> >   .../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.

I'm very sorry, it was my fault. Although I learned a lot from libbpf, 
there is still a lot to learn and improve. Thank you very much for your 
advice and the very powerful libbpf.

regards,
Shuyi

> [...]
>
> > -       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";
>
> [...]