Re: [PATCH v2 04/24] linux-module: Do not use shell environment

[Uladzimir Bely <ubely@ilbers.de>]

In the email from Friday, 19 Nov 2021. 15:44:12 +03 user Jan Kiszka wrote:
> On 19.11.21 13:13, Uladzimir Bely wrote:
> 
> > +KDIR := $(shell dpkg -L $(KERNEL_DEP) | grep "/lib/modules/.*/build")
> > +endif
> > +
> > +# With sbuild `dh clean` is called before chroot's apt database updated.
> > So, +# KDIR is empty at that moment and the override causes error. Will
> > skip it. +ifneq ($(KDIR),)
> > 
> >  override_dh_auto_clean:
> >  	$(MAKE) -C $(KDIR) M=$(PWD) clean
> > 
> > +endif
> 
> This looks wrong, or at least fragile. Why can we live without a proper
> clean on the kernel tree?
> 
> Jan

Actually, this workaround with `ifneq ($(KDIR),)` I added to the patch after 
the commit https://github.com/ilbers/isar/commit/248436880eb2 was applied to 
`next`.

This change doesn't cancel a proper clean on the kernel. Here are some example 
logs:

`next`: https://gist.github.com/WiseLord/0fb98bc036532ec03e4f763b2ba06a41
`sbuild`: https://gist.github.com/WiseLord/3c35d477efc025bcc9cd3c5cbd3dbc5d

On current `next` code dh_clean (and override-related `make ... clean` on 
kernel code) is executed by dpkg-buildpackage. At this point KDIR is set to a 
proper value, so it works as expected.

With sbuild dh_clean happens to be executed twice:
- 1: immediately after sbuild is run, executed by sbuild itself
- 2: after few stages (like downloading deps and so on), executed by dpkg-
buildpackage.

The issue is that at 1st execution KDIR is not set, so `make ... clean` 
(coming with override) produces wrong command.

That's why this workaround (skip `make ... clean` in case of empty KDIR) was 
added. Proper cleaning is still performed, but on the second call of dh_clean.

Probably, there is a way to say sbuild not to run this 'generic' dh_clean and 
use just one from dpkg-buildpackage later...

-- 
Uladzimir Bely
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