netdev - Re: [PATCH bpf-next v3 2/3] libbpf: add bpf_object__load_xattr() API function to pass log

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Message-ID: <5895821e-0d79-2169-d631-0fa7560135ec@netronome.com>
Date:   Fri, 24 May 2019 12:51:14 +0100
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH bpf-next v3 2/3] libbpf: add bpf_object__load_xattr() API
 function to pass log_level

2019-05-24 13:22 UTC+0200 ~ Jesper Dangaard Brouer <brouer@...hat.com>
> On Fri, 24 May 2019 11:36:47 +0100
> Quentin Monnet <quentin.monnet@...ronome.com> wrote:
> 
>> libbpf was recently made aware of the log_level attribute for programs,
>> used to specify the level of information expected to be dumped by the
>> verifier. Function bpf_prog_load_xattr() got support for this log_level
>> parameter.
>>
>> But some applications using libbpf rely on another function to load
>> programs, bpf_object__load(), which does accept any parameter for log
>> level. Create an API function based on bpf_object__load(), but accepting
>> an "attr" object as a parameter. Then add a log_level field to that
>> object, so that applications calling the new bpf_object__load_xattr()
>> can pick the desired log level.
> 
> Does this allow us to extend struct bpf_object_load_attr later?

I see no reason why it could not. Having the _xattr() version of the
function is precisely a way to have something extensible in the future,
without having to create additional API functions each time we want to
pass a new parameter. And e.g. struct bpf_prog_load_attr (used with
bpf_prog_load_xattr()) has already been extended in the past. So, yeah,
we can add to it in the future. Do you have something in mind?

Quentin