netdev - Re: [PATCH bpf-next 3/5] selftests/bpf: add selftest for BPF_PROG_TYPE

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Date:   Mon, 3 Aug 2020 04:33:45 +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 3/5] selftests/bpf: add selftest for
 BPF_PROG_TYPE_USER



> On Aug 2, 2020, at 6:43 PM, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
> 
> On Sat, Aug 1, 2020 at 1:50 AM Song Liu <songliubraving@...com> wrote:
>> 
>> This test checks the correctness of BPF_PROG_TYPE_USER program, including:
>> running on the right cpu, passing in correct args, returning retval, and
>> being able to call bpf_get_stack|stackid.
>> 
>> Signed-off-by: Song Liu <songliubraving@...com>
>> ---
>> .../selftests/bpf/prog_tests/user_prog.c      | 52 +++++++++++++++++
>> tools/testing/selftests/bpf/progs/user_prog.c | 56 +++++++++++++++++++
>> 2 files changed, 108 insertions(+)
>> create mode 100644 tools/testing/selftests/bpf/prog_tests/user_prog.c
>> create mode 100644 tools/testing/selftests/bpf/progs/user_prog.c
>> 
>> diff --git a/tools/testing/selftests/bpf/prog_tests/user_prog.c b/tools/testing/selftests/bpf/prog_tests/user_prog.c
>> new file mode 100644
>> index 0000000000000..416707b3bff01
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/user_prog.c
>> @@ -0,0 +1,52 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2020 Facebook */
>> +#include <test_progs.h>
>> +#include "user_prog.skel.h"
>> +
>> +static int duration;
>> +
>> +void test_user_prog(void)
>> +{
>> +       struct bpf_user_prog_args args = {{0, 1, 2, 3, 4}};
>> +       struct bpf_prog_test_run_attr attr = {};
>> +       struct user_prog *skel;
>> +       int i, numcpu, ret;
>> +
>> +       skel = user_prog__open_and_load();
>> +
>> +       if (CHECK(!skel, "user_prog__open_and_load",
>> +                 "skeleton open_and_laod failed\n"))
>> +               return;
>> +
>> +       numcpu = libbpf_num_possible_cpus();
> 
> nit: possible doesn't mean online right now, so it will fail on
> offline or non-present CPUs

Just found parse_cpu_mask_file(), will use it to fix this. 

[...]

>> +
>> +volatile int cpu_match = 1;
>> +volatile __u64 sum = 1;
>> +volatile int get_stack_success = 0;
>> +volatile int get_stackid_success = 0;
>> +volatile __u64 stacktrace[PERF_MAX_STACK_DEPTH];
> 
> nit: no need for volatile for non-static variables
> 
>> +
>> +SEC("user")
>> +int user_func(struct bpf_user_prog_ctx *ctx)
> 
> If you put args in bpf_user_prog_ctx as a first field, you should be
> able to re-use the BPF_PROG macro to access those arguments in a more
> user-friendly way.

I am not sure I am following here. Do you mean something like:

struct bpf_user_prog_ctx {
        __u64 args[BPF_USER_PROG_MAX_ARGS];
        struct pt_regs *regs;
};

(swap args and regs)? 

Thanks,
Song