netdev - Re: [PATCH bpf-next v10 01/23] selftests/bpf: regroup and declare similar kfuncs selftests in an array

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Date:   Tue, 6 Sep 2022 18:12:43 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Jiri Kosina <jikos@...nel.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>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Shuah Khan <shuah@...nel.org>,
        Dave Marchevsky <davemarchevsky@...com>,
        Joe Stringer <joe@...ium.io>, Jonathan Corbet <corbet@....net>,
        Tero Kristo <tero.kristo@...ux.intel.com>,
        lkml <linux-kernel@...r.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>
Subject: Re: [PATCH bpf-next v10 01/23] selftests/bpf: regroup and declare
 similar kfuncs selftests in an array

On Tue, Sep 6, 2022 at 3:50 PM Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
>
> On Tue, Sep 6, 2022 at 5:27 AM Kumar Kartikeya Dwivedi <memxor@...il.com> wrote:
> >
> > On Tue, 6 Sept 2022 at 05:25, Kumar Kartikeya Dwivedi <memxor@...il.com> wrote:
> > >
> > > On Fri, 2 Sept 2022 at 15:29, Benjamin Tissoires
> > > <benjamin.tissoires@...hat.com> wrote:
> > > >
> > > > Similar to tools/testing/selftests/bpf/prog_tests/dynptr.c:
> > > > we declare an array of tests that we run one by one in a for loop.
> > > >
> > > > Followup patches will add more similar-ish tests, so avoid a lot of copy
> > > > paste by grouping the declaration in an array.
> > > >
> > > > To be able to call bpf_object__find_program_by_name(), we need to use
> > > > plain libbpf calls, and not light skeletons. So also change the Makefile
> > > > to not generate light skeletons.
> > > >
> > > > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > > >
> > > > ---
> > >
> > > I see your point, but this is also a test so that we keep verifying
> > > kfunc call in light skeleton.
> > > Code for relocating both is different in libbpf (we generate BPF ASM
> > > for light skeleton so it is done inside a loader BPF program instead
> > > of userspace).
> >
> > Err, hit send too early.
> > We can probably use a macro to hide how program is called, then do
> > X(prog1)
> > X(prog2)
> > in a series, won't look too bad and avoids duplication at the same time.
> >
> > > You might then be able to make it work for both light and normal skeleton.
> > >
> > WDYT?
> >
>
> On this patch alone, I concede the benefit is minimum. But if you look
> at 6/23, I must confess I definitely prefer having just an array of
> tests at the beginning instead of crippling the tests functions with
> calls or macros.
>
> The actual reason for me to ditch light skeletons was because I was
> using bpf_object__find_program_by_name().
>
> But I can work around that by relying on the offsetof() macro, and
> make the whole thing working for *both* light skeleton and libbpf:
> +struct kfunc_test_params {
> +       const char *prog_name;
> +       unsigned long int lskel_prog_desc_offset;
> +       int retval;
> +};
> +
> +#define TC_TEST(name,__retval) \
> +       { \
> +         .prog_name = #name, \
> +         .lskel_prog_desc_offset = offsetof(struct
> kfunc_call_test_lskel, progs.name), \
> +         .retval = __retval, \
> +       }
> +
> +static struct kfunc_test_params kfunc_tests[] = {
> +       TC_TEST(kfunc_call_test1, 12),
> +       TC_TEST(kfunc_call_test2, 3),
> +       TC_TEST(kfunc_call_test_ref_btf_id, 0),
> +};
> +
> +static void verify_success(struct kfunc_test_params *param)
>  {
> [...]
> +       struct bpf_prog_desc *lskel_prog = (struct bpf_prog_desc
> *)((char *)lskel + param->lskel_prog_desc_offset);
>
> However, for failing tests, I can not really rely on light skeletons
> because we can not dynamically set the autoload property.
> So either I split every failed test in its own file, or I only test
> the ones that are supposed to load, which don't add a lot IMO.
>
> I'll repost the bpf-core changes only so you can have a better idea of
> what I am saying.
>

FWIW, I have now sent them at [0] and dropped all of the people not in
get_maintainers.pl.

Cheers,
Benjamin

[0] https://lore.kernel.org/all/20220906151303.2780789-1-benjamin.tissoires@redhat.com/T/#u