netdev - Re: [PATCH bpf-next 0/4] libbpf: add raw BTF type dumping

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Message-ID: <CAEf4BzYByimHd+FogxVHdq2-L_GLjdGEa_ku7p_c1V-hpyJrWA@mail.gmail.com>
Date:   Tue, 29 Sep 2020 17:44:48 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>, 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 0/4] libbpf: add raw BTF type dumping

On Tue, Sep 29, 2020 at 5:03 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Tue, Sep 29, 2020 at 04:28:39PM -0700, Andrii Nakryiko wrote:
> > Add btf_dump__dump_type_raw() API that emits human-readable low-level BTF type
> > information, same as bpftool output. bpftool is not switched to this API
> > because bpftool still needs to perform all the same BTF type processing logic
> > to do JSON output, so benefits are pretty much zero.
>
> If the only existing user cannot actually use such api it speaks heavily
> against adding such api to libbpf. Comparing strings in tests is nice, but
> could be done with C output just as well.

It certainly can, it just won't save much code, because bpftool would
still need to have a big switch over BTF type kinds to do JSON output.
I can do such conversion, if you prefer. I'm also thinking about
switching pahole to use this during BTF dedup verbose mode, if Arnaldo
will be fine with changing output format a bit.