netdev - Re: [PATCH bpf-next 3/3] selftests/bpf: allow compiling BPF objects without BTF

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Date:   Fri, 19 Mar 2021 19:21:56 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Andrii Nakryiko <andrii@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, kernel-team@...com
Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: allow compiling BPF objects
 without BTF

On Fri, Mar 19, 2021 at 01:59:09PM -0700, Andrii Nakryiko wrote:
> Add ability to skip BTF generation for some BPF object files. This is done
> through using a convention of .nobtf.c file name suffix.
> 
> Also add third statically linked file to static_linked selftest. This file has
> no BTF, causing resulting object file to have only some of DATASEC BTF types.
> It also is using (from BPF code) global variables. This tests both libbpf's
> static linking logic and bpftool's skeleton generation logic.

I don't like the long term direction of patch 1 and 3.
BTF is mandatory for the most bpf kernel features added in the last couple years.
Making user space do quirks for object files without BTF is not something
we should support or maintain. If there is no BTF the linker and skeleton
generation shouldn't crash, of course, but they should reject such object.