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

From: Song Liu <songliubraving@fb.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: open list <linux-kernel@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <Kernel-team@fb.com>,
	john fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	Daniel Xu <dlxu@fb.com>
Subject: Re: [PATCH bpf-next 3/5] selftests/bpf: add selftest for BPF_PROG_TYPE_USER
Date: Mon, 3 Aug 2020 04:33:45 +0000	[thread overview]
Message-ID: <C5606E9B-D3EC-4425-82F5-DA5865836D3E@fb.com> (raw)
In-Reply-To: <CAEf4BzazkFMw3LAs3M2hxSLWWZJ7ywykwte=0WDhC1zgMYw-3A@mail.gmail.com>

> On Aug 2, 2020, at 6:43 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> 
> On Sat, Aug 1, 2020 at 1:50 AM Song Liu <songliubraving@fb.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@fb.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