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

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Message-ID: <20200109220935.iyabjybd5bsesszy@ast-mbp>
Date:   Thu, 9 Jan 2020 14:09:37 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Song Liu <song@...nel.org>
Cc:     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 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.