netdev - Re: [PATCH bpf-next 1/2] bpf: Use --no-fail option if CONFIG

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Message-ID: <CAEf4BzZc6DE85wUTGwE=2FKPuwuuH4480Fh+v63q8J=PRxjgEw@mail.gmail.com>
Date:   Mon, 21 Sep 2020 14:55:27 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Seth Forshee <seth.forshee@...onical.com>
Subject: Re: [PATCH bpf-next 1/2] bpf: Use --no-fail option if CONFIG_BPF is
 not enabled

On Fri, Sep 18, 2020 at 5:30 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Currently all the resolve_btfids 'users' are under CONFIG_BPF
> code, so if we have CONFIG_BPF disabled, resolve_btfids will
> fail, because there's no data to resolve.
>
> In case CONFIG_BPF is disabled, using resolve_btfids --no-fail
> option, that makes resolve_btfids leave quietly if there's no
> data to resolve.
>
> Fixes: c9a0f3b85e09 ("bpf: Resolve BTF IDs in vmlinux image")
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---

If no CONFIG_BTF is specified, there is no need to even run
resolve_btfids. So why not do just that -- run resolve_btfids only
if both CONFIG_BPF and CONFIG_DEBUG_INFO_BTF are specified?


>  scripts/link-vmlinux.sh | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index e6e2d9e5ff48..3173b8cf08cb 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -342,8 +342,13 @@ vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
>
>  # fill in BTF IDs
>  if [ -n "${CONFIG_DEBUG_INFO_BTF}" ]; then
> -info BTFIDS vmlinux
> -${RESOLVE_BTFIDS} vmlinux
> +       info BTFIDS vmlinux
> +       # Let's be more permissive if CONFIG_BPF is disabled
> +       # and do not fail if there's no data to resolve.
> +       if [ -z "${CONFIG_BPF}" ]; then
> +         no_fail=--no-fail
> +       fi
> +       ${RESOLVE_BTFIDS} $no_fail vmlinux
>  fi
>
>  if [ -n "${CONFIG_BUILDTIME_TABLE_SORT}" ]; then
> --
> 2.26.2
>