netdev - Re: [PATCH bpf-next v1 4/6] bpf: selftests: Move test_ksyms

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Date:   Thu, 7 Oct 2021 13:33:49 -0700
From:   Song Liu <song@...nel.org>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next v1 4/6] bpf: selftests: Move test_ksyms_weak test
 to lskel, add libbpf test

On Tue, Oct 5, 2021 at 5:29 PM Kumar Kartikeya Dwivedi <memxor@...il.com> wrote:
>
> Also, avoid using CO-RE features, as lskel doesn't support CO-RE, yet.
> Create a file for testing libbpf skeleton as well, so that both
> gen_loader and libbpf get tested.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@...il.com>
[...]
> diff --git a/tools/testing/selftests/bpf/prog_tests/ksyms_weak_libbpf.c b/tools/testing/selftests/bpf/prog_tests/ksyms_weak_libbpf.c
> new file mode 100644
> index 000000000000..b75725e28647
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/ksyms_weak_libbpf.c
> @@ -0,0 +1,31 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <test_progs.h>
> +#include "test_ksyms_weak.skel.h"
> +
> +void test_ksyms_weak_libbpf(void)

This is (almost?) the same as test_weak_syms(), right? Why do we need both?

> +{
> +       struct test_ksyms_weak *skel;
> +       struct test_ksyms_weak__data *data;
> +       int err;
> +
> +       skel = test_ksyms_weak__open_and_load();
> +       if (!ASSERT_OK_PTR(skel, "test_ksyms_weak__open_and_load"))
> +               return;

[...]

> diff --git a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
> index 5f8379aadb29..521e7b99db08 100644
> --- a/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
> +++ b/tools/testing/selftests/bpf/progs/test_ksyms_weak.c
> @@ -21,7 +21,6 @@ __u64 out__non_existent_typed = -1;
>  extern const struct rq runqueues __ksym __weak; /* typed */
>  extern const void bpf_prog_active __ksym __weak; /* typeless */
>
> -
>  /* non-existent weak symbols. */
>
>  /* typeless symbols, default to zero. */
> @@ -38,7 +37,7 @@ int pass_handler(const void *ctx)
>         /* tests existing symbols. */
>         rq = (struct rq *)bpf_per_cpu_ptr(&runqueues, 0);
>         if (rq)
> -               out__existing_typed = rq->cpu;
> +               out__existing_typed = 0;

Why do we need this change?

>         out__existing_typeless = (__u64)&bpf_prog_active;
>
>         /* tests non-existent symbols. */
> --
> 2.33.0
>