netdev - Re: [PATCH bpf-next v2 00/13] bpf: add btf func info support

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Message-ID: <eac35eaf-5164-2bba-5cca-c165302a4b4a@solarflare.com>
Date:   Wed, 17 Oct 2018 12:02:03 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Yonghong Song <yhs@...com>, <ast@...com>, <kafai@...com>,
        <daniel@...earbox.net>, <netdev@...r.kernel.org>
CC:     <kernel-team@...com>
Subject: Re: [PATCH bpf-next v2 00/13] bpf: add btf func info support

I think the BTF work needs to be better documented; at the moment the only way
 to determine how BTF sections are structured is to read through the headers,
 and cross-reference with the DWARF spec to guess at the semantics of various
 fields.  I've been working on adding BTF support to ebpf_asm, and finding
 very frustrating the amount of guesswork required.
Therefore please make sure that each patch extending the BTF format includes
 documentation patches describing both the layout and the semantics of the new
 extensions.  For example in patch #9 there is no explanation of
 btf_ext_header.line_info_off and btf_ext_header.line_info_len (they're not
 even used by the code, so one cannot reverse-engineer it); while it's fairly
 clear that they indicate the bounds of the line_info subsection, there is no
 specification of what this subsection contains.

-Ed