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

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Message-ID: <3B31DE6E-B128-48D7-91A9-84D51BDF205B@fb.com>
Date:   Mon, 3 Aug 2020 04:21:20 +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:
>> 
>> Add cpu_plus to bpf_prog_test_run_attr. Add BPF_PROG_SEC "user" for
>> BPF_PROG_TYPE_USER programs.
>> 
>> Signed-off-by: Song Liu <songliubraving@...com>
>> ---
>> tools/lib/bpf/bpf.c           | 1 +
>> tools/lib/bpf/bpf.h           | 3 +++
>> tools/lib/bpf/libbpf.c        | 1 +
>> tools/lib/bpf/libbpf_probes.c | 1 +
>> 4 files changed, 6 insertions(+)
>> 
>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
>> index e1bdf214f75fe..b28c3daa9c270 100644
>> --- a/tools/lib/bpf/bpf.c
>> +++ b/tools/lib/bpf/bpf.c
>> @@ -693,6 +693,7 @@ int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr)
>>        attr.test.ctx_size_in = test_attr->ctx_size_in;
>>        attr.test.ctx_size_out = test_attr->ctx_size_out;
>>        attr.test.repeat = test_attr->repeat;
>> +       attr.test.cpu_plus = test_attr->cpu_plus;
>> 
>>        ret = sys_bpf(BPF_PROG_TEST_RUN, &attr, sizeof(attr));
>>        test_attr->data_size_out = attr.test.data_size_out;
>> diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
>> index 6d367e01d05e9..0c799740df566 100644
>> --- a/tools/lib/bpf/bpf.h
>> +++ b/tools/lib/bpf/bpf.h
>> @@ -205,6 +205,9 @@ struct bpf_prog_test_run_attr {
>>        void *ctx_out;      /* optional */
>>        __u32 ctx_size_out; /* in: max length of ctx_out
>>                             * out: length of cxt_out */
>> +       __u32 cpu_plus;     /* specify which cpu to run the test with
>> +                            * cpu_plus = cpu_id + 1.
>> +                            * If cpu_plus = 0, run on current cpu */
> 
> We can't do this due to ABI guarantees. We'll have to add a new API
> using OPTS arguments.

To make sure I understand this correctly, the concern is when we compile
the binary with one version of libbpf and run it with libbpf.so of a 
different version, right? 

Thanks,
Song

> 
>> };
>> 
>> 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)

Will update.