linux-kernel - Re: [PATCH] kbuild: use objcopy to generate asm-offsets

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Message-ID: <d1bb2638-2e0e-44ef-b8da-9746ed532ed1@oracle.com>
Date: Tue, 3 Sep 2024 09:20:56 +0200
From: Vegard Nossum <vegard.nossum@...cle.com>
To: Michael Ellerman <mpe@...erman.id.au>,
        Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
        kvmarm@...ts.linux.dev, kvm@...r.kernel.org,
        linux-um@...ts.infradead.org, bpf@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] kbuild: use objcopy to generate asm-offsets

On 03/09/2024 01:45, Michael Ellerman wrote:
> Vegard Nossum <vegard.nossum@...cle.com> writes:
>> Remove the sed script and compile the C source listing structs and
>> offsets to an object file (instead of assembly code) that embeds C source
>> directly. Then extract the C source using objcopy.
>>
> 
> I threw some builders at this and hit a few errors:

Thanks, I also got the ones from kernel test robot and figured something
was going a bit wrong.

There are several issues: clang wants - instead of /dev/stdout as an
argument to objcopy, and then gcc has some bugs that prevent the numbers
from appearing correctly on some architectures, also I had an extra # in
the COMMENT() macro which only resulted in an error on some
architectures. I've attached a tentative v2 that fixes these issues, but
I'm still trying to figure out why m68k is giving me slightly different
output for include/generated/asm-offsets.h and why the arc assembler
fails.

In the end I'm wondering if this patch is really worth it, given all the
failures and little workarounds :-| If I can sort out the last few
failures I'll submit it as an RFC.

> Full list here, but note there are some unrelated pre-existing failures:
>    http://kisskb.ellerman.id.au/kisskb/head/259bba3447faaf5e5b12ae41a26a62978d4c1965/

Thanks again,

Vegard
View attachment "0001-kbuild-use-objcopy-to-generate-asm-offsets.patch" of type "text/x-patch" (11240 bytes)