netdev - Re: [PATCH bpf-next 06/11] selftests/bpf: add checking of raw type dump in BTF writer APIs selftests

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Date:   Mon, 2 Nov 2020 21:14:39 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Song Liu <songliubraving@...com>
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH bpf-next 06/11] selftests/bpf: add checking of raw type
 dump in BTF writer APIs selftests

On Mon, Nov 2, 2020 at 4:08 PM Song Liu <songliubraving@...com> wrote:
>
>
>
> > On Oct 28, 2020, at 5:58 PM, Andrii Nakryiko <andrii@...nel.org> wrote:
> >
> > From: Andrii Nakryiko <andriin@...com>
> >
> > Add re-usable btf_helpers.{c,h} to provide BTF-related testing routines. Start
> > with adding a raw BTF dumping helpers.
> >
> > Raw BTF dump is the most succinct and at the same time a very human-friendly
> > way to validate exact contents of BTF types. Cross-validate raw BTF dump and
> > writable BTF in a single selftest. Raw type dump checks also serve as a good
> > self-documentation.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
>
> Acked-by: Song Liu <songliubraving@...com>
>
> with a couple nits:
>
> [...]
>
> > +
> > +/* Print raw BTF type dump into a local buffer and return string pointer back.
> > + * Buffer *will* be overwritten by subsequent btf_type_raw_dump() calls
> > + */
> > +const char *btf_type_raw_dump(const struct btf *btf, int type_id)
> > +{
> > +     static char buf[16 * 1024];
> > +     FILE *buf_file;
> > +
> > +     buf_file = fmemopen(buf, sizeof(buf) - 1, "w");
> > +     if (!buf_file) {
> > +             fprintf(stderr, "Failed to open memstream: %d\n", errno);
> > +             return NULL;
> > +     }
> > +
> > +     fprintf_btf_type_raw(buf_file, btf, type_id);
> > +     fflush(buf_file);
> > +     fclose(buf_file);
> > +
> > +     return buf;
> > +}
> > diff --git a/tools/testing/selftests/bpf/btf_helpers.h b/tools/testing/selftests/bpf/btf_helpers.h
> > new file mode 100644
> > index 000000000000..2c9ce1b61dc9
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/btf_helpers.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/* Copyright (c) 2020 Facebook */
> > +#ifndef __BTF_HELPERS_H
> > +#define __BTF_HELPERS_H
> > +
> > +#include <stdio.h>
> > +#include <bpf/btf.h>
> > +
> > +int fprintf_btf_type_raw(FILE *out, const struct btf *btf, __u32 id);
> > +const char *btf_type_raw_dump(const struct btf *btf, int type_id);
> > +
> > +#endif
> > diff --git a/tools/testing/selftests/bpf/prog_tests/btf_write.c b/tools/testing/selftests/bpf/prog_tests/btf_write.c
> > index 314e1e7c36df..bc1412de1b3d 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/btf_write.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/btf_write.c
> > @@ -2,6 +2,7 @@
> > /* Copyright (c) 2020 Facebook */
> > #include <test_progs.h>
> > #include <bpf/btf.h>
> > +#include "btf_helpers.h"
> >
> > static int duration = 0;
> >
> > @@ -11,12 +12,12 @@ void test_btf_write() {
> >       const struct btf_member *m;
> >       const struct btf_enum *v;
> >       const struct btf_param *p;
> > -     struct btf *btf;
> > +     struct btf *btf = NULL;
>
> No need to initialize btf.
>
> >       int id, err, str_off;
> >
> >       btf = btf__new_empty();
> >       if (CHECK(IS_ERR(btf), "new_empty", "failed: %ld\n", PTR_ERR(btf)))
> > -             return;
> > +             goto err_out;
>
> err_out is not needed either.

eagle eye ;) fixed both

>
> [...]