Re: [PATCH bpf-next] tools/bpftool: show btf id in program information

From: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>, Yonghong Song <yhs@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Quentin Monnet <quentin.monnet@netronome.com>,
	Martin Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Andrii Nakryiko <andriin@fb.com>
Subject: Re: [PATCH bpf-next] tools/bpftool: show btf id in program information
Date: Tue, 16 Apr 2019 17:57:14 +0900	[thread overview]
Message-ID: <0aade06e-5b1c-f80d-8bc2-a5782b586adf@lab.ntt.co.jp> (raw)
In-Reply-To: <CAEf4BzZUnk+qAyp86UW-w6MWYKYq+HqL5Q5e8SfKkna4pxFRcw@mail.gmail.com>

On 4/16/2019 9:54 AM, Andrii Nakryiko wrote:
> On Thu, Apr 11, 2019 at 8:38 AM Yonghong Song <yhs@fb.com> wrote:
>>
>>
>> cc Andrii
>>
>> On 4/11/19 12:51 AM, Daniel Borkmann wrote:
>>> On 04/10/2019 05:39 PM, Jakub Kicinski wrote:
>>>> On Wed, 10 Apr 2019 13:56:42 +0900, Prashant Bhole wrote:
>>>>> Let's add a way to know whether a program has btf context.
>>>>> Patch adds 'btf_id' in the output of program listing.
>>>>> When btf_id is present, it means program has btf context.
>>>>>
>>>>> Sample output:
>>>>> user@test# bpftool prog list
>>>>> 25: xdp  name xdp_prog1  tag 539ec6ce11b52f98  gpl
>>>>>      loaded_at 2019-04-10T11:44:20+0900  uid 0
>>>>>      xlated 488B  not jited  memlock 4096B  map_ids 23
>>>>>      btf_id 1
>>>>>
>>>>> Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
>>>>
>>>> Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
>>>
>>> Applied, thanks!
>>>
>>> What would be the plan for the maps listing?
>> [...]
>>> I think what we could also potentially have is some way to dump
>>> the BTF type info based on such above id. Perhaps it would make
>>> sense to similarly share the verifier's printer with bpftool?
>>
>> Agreed. It does make sense to print the detailed info for a btf id
>> through bpftool.
>>
>> Andrii had a btf dumper to dump types as well as BTF elf file .btf.ext
>> contents in his private branch. Maybe Andrii can comment further
>> on this subject.
> 
> Yes, absolutely, we should have this as part of bpftool. I'm going to
> start porting this logic from my private prototype very soon.
> 
> I think we should be able to have both low-level (though still
> human-readable) BTF dump as close to underlying BTF data as possible,
> as well as an ability to dump struct/union/datasec definitions in
> compilable C format. E.g., for struct/union it will be struct/union
> definition, as well as all the necessary dependent types, for
> datasec/vars it will be a list of global variables declaration w/ all
> the necessary types. Thoughts?
> 

It will be nice to have this functionality in bpftool.
Meanwhile I will send a patch to show btf id of map.

- prashant