> On Oct 28, 2020, at 5:58 PM, Andrii Nakryiko <andrii@xxxxxxxxxx> wrote:
>
> From: Andrii Nakryiko <andriin@xxxxxx>
>
> 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@xxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
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.
[...]
