netdev - Re: [PATCH bpf-next 2/3] bpf: btf: add btf json print functionality

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Date:   Fri, 22 Jun 2018 11:39:13 +0100
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Okash Khawaja <osk@...com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Yonghong Song <yhs@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        kernel-team@...com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 2/3] bpf: btf: add btf json print functionality

2018-06-22 11:24 UTC+0100 ~ Okash Khawaja <osk@...com>
> On Thu, Jun 21, 2018 at 11:42:59AM +0100, Quentin Monnet wrote:
>> Hi Okash,
> hi and sorry about delay in responding. the email got routed to
> incorrect folder.
>>
>> 2018-06-20 13:30 UTC-0700 ~ Okash Khawaja <osk@...com>
>>> This consumes functionality exported in the previous patch. It does the
>>> main job of printing with BTF data. This is used in the following patch
>>> to provide a more readable output of a map's dump. It relies on
>>> json_writer to do json printing. Below is sample output where map keys
>>> are ints and values are of type struct A:
>>>
>>> typedef int int_type;
>>> enum E {
>>>         E0,
>>>         E1,
>>> };
>>>
>>> struct B {
>>>         int x;
>>>         int y;
>>> };
>>>
>>> struct A {
>>>         int m;
>>>         unsigned long long n;
>>>         char o;
>>>         int p[8];
>>>         int q[4][8];
>>>         enum E r;
>>>         void *s;
>>>         struct B t;
>>>         const int u;
>>>         int_type v;
>>>         unsigned int w1: 3;
>>>         unsigned int w2: 3;
>>> };
>>>
>>> $ sudo bpftool map dump -p id 14
>>> [{
>>>         "key": 0
>>>     },{
>>>         "value": {
>>>             "m": 1,
>>>             "n": 2,
>>>             "o": "c",
>>>             "p": [15,16,17,18,15,16,17,18
>>>             ],
>>>             "q": [[25,26,27,28,25,26,27,28
>>>                 ],[35,36,37,38,35,36,37,38
>>>                 ],[45,46,47,48,45,46,47,48
>>>                 ],[55,56,57,58,55,56,57,58
>>>                 ]
>>>             ],
>>>             "r": 1,
>>>             "s": 0x7ffff6f70568,
>>
>> Hexadecimal values, without quotes, are not valid JSON. Please stick to
>> decimal values.
> ah sorry, i used a buggy json validator. this should be a quick fix.
> which would be better:  pointers be output hex strings or integers?

I would go for integers. Although this is harder to read for humans, it
is easier to process for machines, which remain the primary targets for
JSON output.

Quentin