linux-kernel - Re: [PATCH bpf-next 2/5] libbpf: support BPF_PROG_TYPE

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Date:   Tue, 4 Aug 2020 01:18:07 +0000
From:   Song Liu <songliubraving@...com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
CC:     open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Xu <dlxu@...com>
Subject: Re: [PATCH bpf-next 2/5] libbpf: support BPF_PROG_TYPE_USER programs



> On Aug 2, 2020, at 6:40 PM, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
> 
> On Sat, Aug 1, 2020 at 1:50 AM Song Liu <songliubraving@...com> wrote:
>> 

[...]

> 
>> };
>> 
>> LIBBPF_API int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr);
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index b9f11f854985b..9ce175a486214 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -6922,6 +6922,7 @@ static const struct bpf_sec_def section_defs[] = {
>>        BPF_PROG_SEC("lwt_out",                 BPF_PROG_TYPE_LWT_OUT),
>>        BPF_PROG_SEC("lwt_xmit",                BPF_PROG_TYPE_LWT_XMIT),
>>        BPF_PROG_SEC("lwt_seg6local",           BPF_PROG_TYPE_LWT_SEG6LOCAL),
>> +       BPF_PROG_SEC("user",                    BPF_PROG_TYPE_USER),
> 
> let's do "user/" for consistency with most other prog types (and nice
> separation between prog type and custom user name)

About "user" vs. "user/", I still think "user" is better. 

Unlike kprobe and tracepoint, user prog doesn't use the part after "/". 
This is similar to "perf_event" for BPF_PROG_TYPE_PERF_EVENT, "xdl" for 
BPF_PROG_TYPE_XDP, etc. If we specify "user" here, "user/" and "user/xxx" 
would also work. However, if we specify "user/" here, programs that used 
"user" by accident will fail to load, with a message like:

	libbpf: failed to load program 'user'

which is confusing. 

Thanks,
Song

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