linux-kernel - Re: [RFC PATCH bpf-next 0/2] bpf, libbpf: share BTF data show functionality

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Message-ID: <20210112024545.spoxpownh5dybffa@ast-mbp>
Date:   Mon, 11 Jan 2021 18:45:45 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, rostedt@...dmis.org,
        mingo@...hat.com, haoluo@...gle.com, jolsa@...nel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
        shuah@...nel.org
Subject: Re: [RFC PATCH bpf-next 0/2] bpf, libbpf: share BTF data show
 functionality

On Mon, Jan 11, 2021 at 05:32:51PM +0000, Alan Maguire wrote:
> The BPF Type Format (BTF) can be used in conjunction with the helper
> bpf_snprintf_btf() to display kernel data with type information.
> 
> This series generalizes that support and shares it with libbpf so
> that libbpf can display typed data.  BTF display functionality is
> factored out of kernel/bpf/btf.c into kernel/bpf/btf_show_common.c,
> and that file is duplicated in tools/lib/bpf.  Similarly, common
> definitions and inline functions needed for this support are
> extracted into include/linux/btf_common.h and this header is again
> duplicated in tools/lib/bpf.

I think duplication will inevitable cause code to diverge.
Could you keep a single copy?
Take a look at kernel/bpf/disasm.[ch]
It compiled once for the kernel and once for bpftool.
So should be possible to do something similar for this case as well?