netdev - Re: [PATCH bpf-next 02/11] selftest/bpf: relax btf

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Date:   Fri, 30 Oct 2020 11:44:59 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Song Liu <song@...nel.org>
Cc:     Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 02/11] selftest/bpf: relax btf_dedup test checks

On Fri, Oct 30, 2020 at 9:43 AM Song Liu <song@...nel.org> wrote:
>
> On Thu, Oct 29, 2020 at 1:40 AM Andrii Nakryiko <andrii@...nel.org> wrote:
> >
> > Remove the requirement of a strictly exact string section contents. This used
> > to be true when string deduplication was done through sorting, but with string
> > dedup done through hash table, it's no longer true. So relax test harness to
> > relax strings checks and, consequently, type checks, which now don't have to
> > have exactly the same string offsets.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
> > ---
> >  tools/testing/selftests/bpf/prog_tests/btf.c | 34 +++++++++++---------
> >  1 file changed, 19 insertions(+), 15 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/btf.c b/tools/testing/selftests/bpf/prog_tests/btf.c
> > index 93162484c2ca..2ccc23b2a36f 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/btf.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/btf.c
> > @@ -6652,7 +6652,7 @@ static void do_test_dedup(unsigned int test_num)
> >         const void *test_btf_data, *expect_btf_data;
> >         const char *ret_test_next_str, *ret_expect_next_str;
> >         const char *test_strs, *expect_strs;
> > -       const char *test_str_cur, *test_str_end;
> > +       const char *test_str_cur;
> >         const char *expect_str_cur, *expect_str_end;
> >         unsigned int raw_btf_size;
> >         void *raw_btf;
> > @@ -6719,12 +6719,18 @@ static void do_test_dedup(unsigned int test_num)
> >                 goto done;
> >         }
> >
> > -       test_str_cur = test_strs;
> > -       test_str_end = test_strs + test_hdr->str_len;
> >         expect_str_cur = expect_strs;
> >         expect_str_end = expect_strs + expect_hdr->str_len;
> > -       while (test_str_cur < test_str_end && expect_str_cur < expect_str_end) {
> > +       while (expect_str_cur < expect_str_end) {
> >                 size_t test_len, expect_len;
> > +               int off;
> > +
> > +               off = btf__find_str(test_btf, expect_str_cur);
> > +               if (CHECK(off < 0, "exp str '%s' not found: %d\n", expect_str_cur, off)) {
> > +                       err = -1;
> > +                       goto done;
> > +               }
> > +               test_str_cur = btf__str_by_offset(test_btf, off);
> >
> >                 test_len = strlen(test_str_cur);
> >                 expect_len = strlen(expect_str_cur);
> > @@ -6741,15 +6747,8 @@ static void do_test_dedup(unsigned int test_num)
> >                         err = -1;
> >                         goto done;
> >                 }
> > -               test_str_cur += test_len + 1;
> >                 expect_str_cur += expect_len + 1;
> >         }
> > -       if (CHECK(test_str_cur != test_str_end,
> > -                 "test_str_cur:%p != test_str_end:%p",
> > -                 test_str_cur, test_str_end)) {
> > -               err = -1;
> > -               goto done;
> > -       }
> >
> >         test_nr_types = btf__get_nr_types(test_btf);
> >         expect_nr_types = btf__get_nr_types(expect_btf);
> > @@ -6775,10 +6774,15 @@ static void do_test_dedup(unsigned int test_num)
> >                         err = -1;
> >                         goto done;
> >                 }
> > -               if (CHECK(memcmp((void *)test_type,
> > -                                (void *)expect_type,
> > -                                test_size),
> > -                         "type #%d: contents differ", i)) {
>
> I guess test_size and expect_size are not needed anymore?

hm.. they are used just one check above, still needed

>
> > +               if (CHECK(btf_kind(test_type) != btf_kind(expect_type),
> > +                         "type %d kind: exp %d != got %u\n",
> > +                         i, btf_kind(expect_type), btf_kind(test_type))) {
> > +                       err = -1;
> > +                       goto done;
> > +               }
> > +               if (CHECK(test_type->info != expect_type->info,
> > +                         "type %d info: exp %d != got %u\n",
> > +                         i, expect_type->info, test_type->info)) {
>
> btf_kind() returns part of ->info, so we only need the second check, no?

technically yes, but when kind mismatches, figuring that out from raw
info field is quite painful, so having a better, more targeted check
is still good.

>
> IIUC, test_type and expect_type may have different name_off now. Shall
> we check ->size matches?

yep, sure, I'll add

>
>
> >                         err = -1;
> >                         goto done;
> >                 }
> > --
> > 2.24.1
> >