netdev - Re: [PATCH v2 bpf-next 7/7] selftests/bpf: Add unit tests for global functions

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Date:   Thu, 9 Jan 2020 22:35:48 +0000
From:   Song Liu <songliubraving@...com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Song Liu <song@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 7/7] selftests/bpf: Add unit tests for global
 functions



> On Jan 9, 2020, at 2:09 PM, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> 
> On Thu, Jan 09, 2020 at 09:27:26AM -0800, Song Liu wrote:
>> On Wed, Jan 8, 2020 at 10:39 PM Alexei Starovoitov <ast@...nel.org> wrote:
>>> 
>>> test_global_func[12] - check 512 stack limit.
>>> test_global_func[34] - check 8 frame call chain limit.
>>> test_global_func5    - check that non-ctx pointer cannot be passed into
>>>                       a function that expects context.
>>> test_global_func6    - check that ctx pointer is unmodified.
>>> 
>>> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
>> 
>> Acked-by: Song Liu <songliubraving@...com>
>> 
>>> ---
>>> .../bpf/prog_tests/test_global_funcs.c        | 81 +++++++++++++++++++
>>> .../selftests/bpf/progs/test_global_func1.c   | 45 +++++++++++
>>> .../selftests/bpf/progs/test_global_func2.c   |  4 +
>>> .../selftests/bpf/progs/test_global_func3.c   | 65 +++++++++++++++
>>> .../selftests/bpf/progs/test_global_func4.c   |  4 +
>>> .../selftests/bpf/progs/test_global_func5.c   | 31 +++++++
>>> .../selftests/bpf/progs/test_global_func6.c   | 31 +++++++
>>> 7 files changed, 261 insertions(+)
>>> create mode 100644 tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
>>> create mode 100644 tools/testing/selftests/bpf/progs/test_global_func1.c
>>> create mode 100644 tools/testing/selftests/bpf/progs/test_global_func2.c
>>> create mode 100644 tools/testing/selftests/bpf/progs/test_global_func3.c
>>> create mode 100644 tools/testing/selftests/bpf/progs/test_global_func4.c
>>> create mode 100644 tools/testing/selftests/bpf/progs/test_global_func5.c
>>> create mode 100644 tools/testing/selftests/bpf/progs/test_global_func6.c
>>> 
>>> diff --git a/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
>>> new file mode 100644
>>> index 000000000000..bc588fa87d65
>>> --- /dev/null
>>> +++ b/tools/testing/selftests/bpf/prog_tests/test_global_funcs.c
>>> @@ -0,0 +1,81 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/* Copyright (c) 2020 Facebook */
>>> +#include <test_progs.h>
>>> +
>>> +const char *err_str;
>>> +bool found;
>>> +
>>> +static int libbpf_debug_print(enum libbpf_print_level level,
>>> +                             const char *format, va_list args)
>>> +{
>>> +       char *log_buf;
>>> +
>>> +       if (level != LIBBPF_WARN ||
>>> +           strcmp(format, "libbpf: \n%s\n")) {
>>> +               vprintf(format, args);
>>> +               return 0;
>>> +       }
>>> +
>>> +       log_buf = va_arg(args, char *);
>>> +       if (!log_buf)
>>> +               goto out;
>>> +       if (strstr(log_buf, err_str) == 0)
>>> +               found = true;
>>> +out:
>>> +       printf(format, log_buf);
>>> +       return 0;
>>> +}
>> 
>> libbpf_debug_print() looks very useful. Maybe we can move it to some
>> header files?
> 
> I think it's hack that goes deep into libbpf internals that should be
> discouraged. It's clearly very useful for selftests, but imo libbpf's log_buf
> api should be redesigned instead. It's imo the worst part of the library.

Yeah, those global variables don't look good. 

Song