Build a Single in Tree Linux Kernel Module (Debian & Clones)

How misleading and complicated this task should be that I’m writing such an article in 2022?
Anyway, if you struggle compiling a simple, standalone Linux kernel module on Debian, Ubuntu, Mint and the like, here’s the recipe:

• Fetch linux-source-<version> and linux-headers-<version>

$ sudo apt install linux-source-5.4.0 linux-headers-$(uname -r)

Do not use apt-get source linux-source-<version>, only pain will you find.

• Untar the fetched archive where you’d like

$ tar jxvf /usr/src/linux-source-5.4.0.tar.bz2

• Copy your current kernel configuration

$ cd linux-source-5.4.0
$ cp /boot/config-$(uname -r) .config

• Prepare the build environment

$ make oldconfig scripts prepare modules_prepare

• Copy current kernel exported symbols file

$ cp /usr/src/linux-headers-$(uname -r)/Module.symvers .

• Build the module you need

$ make -C . M=arch/x86/kvm

• Test it

$ sudo insmod arch/x86/kvm/kvm-intel.ko

Eventually backup the current loaded module (modinfo <module>), replace it with your freshly built one and don’t forget to depmod -a.