Package: v4l2loopback-dkms
Version: 0.13.1-1
Severity: serious

DKMS make.log for v4l2loopback-0.13.1 for kernel 6.7.12-686-pae (i686)
Mon May 13 09:57:13 UTC 2024

++++++ To sign the  module, you must set KBUILD_SIGN_KEY/KBUILD_SIGN_CERT to 
point to the signing key/certificate!
++++++ For your convenience, we try to read these variables as 
'mok_signing_key' resp. 'mok_certificate' from /etc/dkms/framework.conf

++++++ If your certificate requires a password, pass it via the KBUILD_SIGN_PIN 
env-var!
++++++ E.g. using 'export KBUILD_SIGN_PIN; read -s -p "Passphrase for signing 
key : " KBUILD_SIGN_PIN; sudo --preserve-env=KBUILD_SIGN_PIN make sign'

Building v4l2-loopback driver...
make -C /lib/modules/6.7.12-686-pae/build 
M=/var/lib/dkms/v4l2loopback/0.13.1/build KCPPFLAGS="" modules
make[1]: Entering directory '/usr/src/linux-headers-6.7.12-686-pae'
  CC [M]  /var/lib/dkms/v4l2loopback/0.13.1/build/v4l2loopback.o
  MODPOST /var/lib/dkms/v4l2loopback/0.13.1/build/Module.symvers
ERROR: modpost: "__moddi3" 
[/var/lib/dkms/v4l2loopback/0.13.1/build/v4l2loopback.ko] undefined!
make[3]: *** 
[/usr/src/linux-headers-6.7.12-common/scripts/Makefile.modpost:145: 
/var/lib/dkms/v4l2loopback/0.13.1/build/Module.symvers] Error 1
make[2]: *** [/usr/src/linux-headers-6.7.12-common/Makefile:1888: modpost] 
Error 2
make[1]: *** [/usr/src/linux-headers-6.7.12-common/Makefile:246: __sub-make] 
Error 2
make[1]: Leaving directory '/usr/src/linux-headers-6.7.12-686-pae'
make: *** [Makefile:53: v4l2loopback.ko] Error 2


This probably affects more 32-bit architectures ...

IIRC gcc generates a __moddi3 function call for
        (long long) a % (long long) b
(or a similar operation on long long) on architectures without native
support for long long. The symbol is provided by libgcc_s but for
obvious reasons the kernel cannot be linked agaist that library.

This seems to be a regression from the v4l2loopback-dkms +
linux-headers-* combination in bookworm.

This problem does not appear during the autopkgtest since that is
restricted to amd64 and arm64 (which is probably a copy+paste mistake as
the commit references bbswitch-dkms which is only useful on platforms
with the proprietary nvidia driver and thus restricted to these
architectures).


Andreas

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