linux-kernel - Re: [PATCH 3/4] kbuild: slim down package for building external modules

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Message-ID: <20250220-kickass-famous-kittiwake-c11f5b@l-nschier-nb>
Date: Thu, 20 Feb 2025 16:54:39 +0100
From: Nicolas Schier <n.schier@....de>
To: Jeffrey Hugo <quic_jhugo@...cinc.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH 3/4] kbuild: slim down package for building external
 modules

On Thu, Feb 20, 2025 at 08:03:32AM -0700, Jeffrey Hugo wrote:
> On 2/20/2025 3:03 AM, Nicolas Schier wrote:
> > On Tue, Feb 18, 2025 at 01:25:38PM -0700, Jeffrey Hugo wrote:
> > > On 7/27/2024 1:42 AM, Masahiro Yamada wrote:
> > > > Exclude directories and files unnecessary for building external modules:
> > > > 
> > > >    - include/config/  (except include/config/auto.conf)
> > > >    - scripts/atomic/
> > > >    - scripts/dtc/
> > > >    - scripts/kconfig/
> > > >    - scripts/mod/mk_elfconfig
> > > >    - scripts/package/
> > > >    - scripts/unifdef
> > > >    - .config
> > > 
> > > Please revert this (the removal of .config).
> > > 
> > > I got some strange reports that our external module install broke, and
> > > traced it to this change.  Our external module references the .config
> > > because we have different logic for the build depending on if other, related
> > > modules are present or not.
> > > 
> > > Also, it looks like this broke DKMS for some configurations, which not only
> > > impacts DKMS itself [1] but also downstream projects [2].
> > > 
> > > While DKMS may be updated going forward to avoid this issue, there are
> > > plenty of affected version out in the wild.
> > > 
> > > Also, I haven't surveyed every distro, but it looks like Ubuntu still
> > > packages the .config with their headers in their upcoming "Plucky" release
> > > based on 6.12.  I suspect they wouldn't do that if they didn't feel it was
> > > needed/useful.
> > > 
> > > -Jeff
> > > 
> > > [1]: https://github.com/dell/dkms/issues/464
> > > [2]: https://github.com/linux-surface/linux-surface/issues/1654
> > 
> > Hi Jeff,
> > 
> > do you know the related thread [1]?  According to the last mail, DKMS
> > has fixed its issue already in December.
> 
> DKMS tip might be fixed, but production versions are in various distros,
> which are not updated.  Therefore actual users are impacted by this.
> 
> What happened to the #1 rule of kernel, that we do not break users?

I think, Masahiro already provided valid and profound reasons for
keeping it the way it is.  Users of run-time kernel interfaces are not
affected by the change.  Concretely reported issues were, as far as I
know, only a matter of specific non-official way to work with .config
for other reasons than just building external kernel modules in the way
it is thought to work.

Kind regards,
Nicolas

> This still needs to be reverted.
> 
> -Jeff
> 
> > 
> > Kind regards,
> > Nicolas
> > 
> > [1]: https://lore.kernel.org/linux-kbuild/CAK7LNARqEOVOzP5vdUVF0KxQBNb9xtYs-COSXXWDMpBzGaLGow@mail.gmail.com/T/#m95f48caf46357a41c1df5e038e227a01ab89dbda
>