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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Thu, 3 Nov 2022 11:45:55 -0700
Message-ID: <CAEf4BzYAcGgM93r5YfF2ZQWjAnc4k=aN5C3in-bZ-6n+Jrn1vw@mail.gmail.com>
Subject: Re: [PATCH bpf-next] selftests/bpf: cgroup_helpers.c: Fix strncpy()
 fortify warning
To:     Rong Tao <rtoax@foxmail.com>
Cc:     daniel@iogearbox.net, andrii@kernel.org, ast@kernel.org,
        bpf@vger.kernel.org, david.laight@aculab.com, haoluo@google.com,
        john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        martin.lau@linux.dev, mykolal@fb.com, rongtao@cestc.cn,
        sdf@google.com, shuah@kernel.org, song@kernel.org, yhs@fb.com
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On Wed, Nov 2, 2022 at 5:59 AM Rong Tao <rtoax@foxmail.com> wrote:
>
> From: Rong Tao <rongtao@cestc.cn>
>
> Move libbpf_strlcpy() to libbpf_common.h, and replace strncpy() with
> libbpf_strlcpy(), fix compile warning.
>
> We can't use libbpf_internal.h directly, because it introduces a lot of
> header dependency issues. So move libbpf_strlcpy() into libbpf_common.h,
> and if you need to use the libbpf_strlcpy() function, you need to include
> the header file libbpf.h

well, no, we should make libbpf_strlcpy as a public API, it's internal
helper. libbpf_common.h is part of libbpf's UAPI.

So don't touch libbpf, please. Name the function as _strlcpy or
something like that, put it into bpf_util.h and use that from
selftests.

>
> How to reproduce this compilation warning:
>
> $ make -C samples/bpf
> cgroup_helpers.c: In function =E2=80=98__enable_controllers=E2=80=99:
> cgroup_helpers.c:80:17: warning: =E2=80=98strncpy=E2=80=99 specified boun=
d 4097 equals destination size [-Wstringop-truncation]
>    80 |                 strncpy(enable, controllers, sizeof(enable));
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Signed-off-by: Rong Tao <rongtao@cestc.cn>
> ---
>  tools/lib/bpf/libbpf_common.h                | 19 +++++++++++++++++++
>  tools/lib/bpf/libbpf_internal.h              | 19 -------------------
>  tools/testing/selftests/bpf/cgroup_helpers.c |  3 ++-
>  tools/testing/selftests/bpf/xsk.c            | 19 -------------------
>  4 files changed, 21 insertions(+), 39 deletions(-)
>

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