Closing as user requests
** Changed in: dkms (Ubuntu)
Status: New => Invalid
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https://bugs.launchpad.net/bugs/2112114
Title:
dkms 3.2.1 does not correctly set kernel CC version
Status in dkms package in Ubuntu:
Invalid
Bug description:
This package just landed on 22.04 (and I think also on 24.04):
ii dkms 1:3.2.1-1 all Dynamic Kernel Module System
(DKMS)
On a 22.04 machine, Nvidia kernel modules fail to build with this version,
even
though the same module against the same kernel version did build with the
previous dkms. Downgrading to dkms=2.8.7-2ubuntu2.2 allows the module to build
again.
This is because:
1. The new version of dkms fails to parse the compiler version out of kernel
config
2. Current kernels for jammy are compiled with gcc-12
3. The default compiler on jammy is gcc-11
4. The kernel compiler flags include -ftrivial-auto-var-init=zero which is
not supported in gcc-11.
This is difficult to work around, because setting CC has no effect
(the dkms script deliberately unsets it), and update-alternatives does
not admit /usr/bin/gcc-12 as a valid alternative for 'cc'.
This bug doesn't currently affect noble only because the default
compiler is the same one that was used to compile the kernel.
Why dkms fails to extract the compiler version - it's down to this sed
expression:
cc=$(sed -n 's|^CONFIG_CC_VERSION_TEXT="\([^ ]*\) .*"|\1|p'
"${kernel_config}")
Version 2.8.7 applies this to '.config' in the kernel build dir, while
version 3.2.1 applies it to 'include/config/auto.conf'. But we will
see that the quotes that that expression expects are not present in
the latter config file.
$ grep CONFIG_CC_VERSION_TEXT= /lib/modules/6.8.0-59-generic/build/.config
CONFIG_CC_VERSION_TEXT="x86_64-linux-gnu-gcc-12 (Ubuntu
12.3.0-1ubuntu1~22.04) 12.3.0"
$ grep CONFIG_CC_VERSION_TEXT=
/lib/modules/6.8.0-59-generic/build/include/config/auto.conf
CONFIG_CC_VERSION_TEXT=x86_64-linux-gnu-gcc-12 (Ubuntu 12.3.0-1ubuntu1~22.04)
12.3.0
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