netdev - Re: [PATCH bpf-next v6 7/7] selftests/bpf: Test "bpftool gen min_core

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Date:   Tue, 15 Feb 2022 17:56:40 -0500
From:   Mauricio Vásquez Bernal <mauricio@...volk.io>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Rafael David Tinoco <rafaeldtinoco@...il.com>,
        Lorenzo Fontana <lorenzo.fontana@...stic.co>,
        Leonardo Di Donato <leonardo.didonato@...stic.co>
Subject: Re: [PATCH bpf-next v6 7/7] selftests/bpf: Test "bpftool gen min_core_btf"

On Fri, Feb 11, 2022 at 7:42 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Wed, Feb 9, 2022 at 2:27 PM Mauricio Vásquez <mauricio@...volk.io> wrote:
> >
> > This commit reuses the core_reloc test to check if the BTF files
> > generated with "bpftool gen min_core_btf" are correct. This introduces
> > test_core_btfgen() that runs all the core_reloc tests, but this time
> > the source BTF files are generated by using "bpftool gen min_core_btf".
> >
> > The goal of this test is to check that the generated files are usable,
> > and not to check if the algorithm is creating an optimized BTF file.
> >
> > Signed-off-by: Mauricio Vásquez <mauricio@...volk.io>
> > Signed-off-by: Rafael David Tinoco <rafael.tinoco@...asec.com>
> > Signed-off-by: Lorenzo Fontana <lorenzo.fontana@...stic.co>
> > Signed-off-by: Leonardo Di Donato <leonardo.didonato@...stic.co>
> > ---
> >  .../selftests/bpf/prog_tests/core_reloc.c     | 46 ++++++++++++++++++-
> >  1 file changed, 45 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
> > index b8bdd1c3efca..10a1d5fb788e 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c
> > @@ -2,6 +2,7 @@
> >  #include <test_progs.h>
> >  #include "progs/core_reloc_types.h"
> >  #include "bpf_testmod/bpf_testmod.h"
> > +#include <linux/limits.h>
> >  #include <sys/mman.h>
> >  #include <sys/syscall.h>
> >  #include <bpf/btf.h>
> > @@ -354,6 +355,8 @@ static int duration = 0;
> >         .fails = true,                                                  \
> >  }
> >
> > +#define BTFGEN_BTF_PATH "/tmp/btfgen.btf"
>
> let's not use fixed file path, better use mkstemp() to create
> temporary file (see core_autosize.c for an example)
>

You're right.


> > +
> >  struct core_reloc_test_case;
> >
> >  typedef int (*setup_test_fn)(struct core_reloc_test_case *test);
> > @@ -836,7 +839,21 @@ static size_t roundup_page(size_t sz)
> >         return (sz + page_size - 1) / page_size * page_size;
> >  }
> >
> > -void test_core_reloc(void)
> > +static int run_btfgen(const char *src_btf, const char *dst_btf, const char *objpath)
> > +{
> > +       char command[4096];
> > +       int n;
> > +
> > +       n = snprintf(command, sizeof(command),
> > +                    "./tools/build/bpftool/bpftool gen min_core_btf %s %s %s",
> > +                    src_btf, dst_btf, objpath);
> > +       if (n < 0 || n >= sizeof(command))
> > +               return -1;
> > +
> > +       return system(command);
> > +}
> > +
> > +static void _test_core_reloc(bool btfgen)
>
> ugh, please don't do leading underscore. Call it
> "run_core_reloc_tests" or whatever, it's easy.
>
> another naming nit (I did get confused for a second because of this):
> use_btfgen, otherwise below in the code my first guess was that
> "btfgen" is actually a path to bpftool or something like that
>
>
> >  {
> >         const size_t mmap_sz = roundup_page(sizeof(struct data));
> >         DECLARE_LIBBPF_OPTS(bpf_object_open_opts, open_opts);
> > @@ -863,6 +880,22 @@ void test_core_reloc(void)
> >                         continue;
> >                 }
> >
> > +               /* generate a "minimal" BTF file and use it as source */
> > +               if (btfgen) {
> > +                       if (!test_case->btf_src_file || test_case->fails) {
> > +                               test__skip();
> > +                               continue;
> > +                       }
> > +
> > +                       unlink(BTFGEN_BTF_PATH);
> > +                       err = run_btfgen(test_case->btf_src_file, BTFGEN_BTF_PATH,
> > +                                        test_case->bpf_obj_file);
> > +                       if (!ASSERT_OK(err, "run_btfgen"))
> > +                               goto cleanup;
> > +
> > +                       test_case->btf_src_file = BTFGEN_BTF_PATH;
> > +               }
> > +
> >                 if (test_case->setup) {
> >                         err = test_case->setup(test_case);
> >                         if (CHECK(err, "test_setup", "test #%d setup failed: %d\n", i, err))
> > @@ -954,8 +987,19 @@ void test_core_reloc(void)
> >                         CHECK_FAIL(munmap(mmap_data, mmap_sz));
> >                         mmap_data = NULL;
> >                 }
> > +               unlink(BTFGEN_BTF_PATH);
> >                 bpf_link__destroy(link);
> >                 link = NULL;
> >                 bpf_object__close(obj);
> >         }
> >  }
> > +
> > +void test_core_reloc(void)
> > +{
> > +       _test_core_reloc(false);
> > +}
> > +
> > +void test_core_btfgen(void)
> > +{
> > +       _test_core_reloc(true);
> > +}
> > --
> > 2.25.1
> >