Re: [PATCH bpf-next] selftest/bpf: Switch recursion test to use htab_map_delete_elem

[Song Liu <song@kernel.org>]

On Sun, Oct 3, 2021 at 9:58 AM Jiri Olsa <jolsa@redhat.com> wrote:
>
> Currently the recursion test is hooking __htab_map_lookup_elem
> function, which is invoked both from bpf_prog and bpf syscall.
>
> But in our kernel build, the __htab_map_lookup_elem gets inlined
> within the htab_map_lookup_elem, so it's not trigered and the
> test fails.
>
> Fixing this by using htab_map_delete_elem, which is not inlined
> for bpf_prog calls (like htab_map_lookup_elem is) and is used
> directly as pointer for map_delete_elem, so it won't disappear
> by inlining.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>

Acked-by: Song Liu <songliubraving@fb.com>

> ---
>  tools/testing/selftests/bpf/prog_tests/recursion.c | 10 +++++-----
>  tools/testing/selftests/bpf/progs/recursion.c      |  9 +++------
>  2 files changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/recursion.c b/tools/testing/selftests/bpf/prog_tests/recursion.c
> index 0e378d63fe18..f3af2627b599 100644
> --- a/tools/testing/selftests/bpf/prog_tests/recursion.c
> +++ b/tools/testing/selftests/bpf/prog_tests/recursion.c
> @@ -20,18 +20,18 @@ void test_recursion(void)
>                 goto out;
>
>         ASSERT_EQ(skel->bss->pass1, 0, "pass1 == 0");
> -       bpf_map_lookup_elem(bpf_map__fd(skel->maps.hash1), &key, 0);
> +       bpf_map_delete_elem(bpf_map__fd(skel->maps.hash1), &key);
>         ASSERT_EQ(skel->bss->pass1, 1, "pass1 == 1");
> -       bpf_map_lookup_elem(bpf_map__fd(skel->maps.hash1), &key, 0);
> +       bpf_map_delete_elem(bpf_map__fd(skel->maps.hash1), &key);
>         ASSERT_EQ(skel->bss->pass1, 2, "pass1 == 2");
>
>         ASSERT_EQ(skel->bss->pass2, 0, "pass2 == 0");
> -       bpf_map_lookup_elem(bpf_map__fd(skel->maps.hash2), &key, 0);
> +       bpf_map_delete_elem(bpf_map__fd(skel->maps.hash2), &key);
>         ASSERT_EQ(skel->bss->pass2, 1, "pass2 == 1");
> -       bpf_map_lookup_elem(bpf_map__fd(skel->maps.hash2), &key, 0);
> +       bpf_map_delete_elem(bpf_map__fd(skel->maps.hash2), &key);
>         ASSERT_EQ(skel->bss->pass2, 2, "pass2 == 2");
>
> -       err = bpf_obj_get_info_by_fd(bpf_program__fd(skel->progs.on_lookup),
> +       err = bpf_obj_get_info_by_fd(bpf_program__fd(skel->progs.on_delete),
>                                      &prog_info, &prog_info_len);
>         if (!ASSERT_OK(err, "get_prog_info"))
>                 goto out;
> diff --git a/tools/testing/selftests/bpf/progs/recursion.c b/tools/testing/selftests/bpf/progs/recursion.c
> index 49f679375b9d..3c2423bb19e2 100644
> --- a/tools/testing/selftests/bpf/progs/recursion.c
> +++ b/tools/testing/selftests/bpf/progs/recursion.c
> @@ -24,8 +24,8 @@ struct {
>  int pass1 = 0;
>  int pass2 = 0;
>
> -SEC("fentry/__htab_map_lookup_elem")
> -int BPF_PROG(on_lookup, struct bpf_map *map)
> +SEC("fentry/htab_map_delete_elem")
> +int BPF_PROG(on_delete, struct bpf_map *map)
>  {
>         int key = 0;
>
> @@ -35,10 +35,7 @@ int BPF_PROG(on_lookup, struct bpf_map *map)
>         }
>         if (map == (void *)&hash2) {
>                 pass2++;
> -               /* htab_map_gen_lookup() will inline below call
> -                * into direct call to __htab_map_lookup_elem()
> -                */
> -               bpf_map_lookup_elem(&hash2, &key);
> +               bpf_map_delete_elem(&hash2, &key);
>                 return 0;
>         }
>
> --
> 2.31.1
>