WSL2 Kernel CI

Github Actions CI config for WSL2 Kernel.

What's This?

Microsoft's original WSL2 kernel misses many kernel modules, incluing:

• Various FS (like squashfs)
• nftables related modules (iptables-nftables won't work)
• Security features (lxc, AppArmor, etc.)

Also, if you are on Dev Insider channel, WSL kernel would often be updated, causing you having to rebuild the kernel each time.

The Kernel Building CI

This CI does these things for you:

• Auto-Merging: Merges Ubuntu's Kconfig onto Microsoft's Kconfig automatically
  • achieved by blacklisting some config symbols based on menuconfig's section, and then merges only good symbols
  • You can find the parts that are masked in config_filter/blacklist_sections, with some notes on what options differs between each other
  • See config_examples directory for a complete list of menuconfig section, and example config after merging & make prepare
• Auto-Update: Automatically Monitor Microsoft's WSL2-Linux-Kernel, and build them once there's a new release
• Deb-Packaging: You can download the deb to install latest kernel header
• Preserve-Version: Built kernel will having the same version as original one, so scripts detecting kernel version would still work

Download

Please goto Repo's Release ;)

Hacking & Tweaking

The CI works by following steps:

1. (Before compiling in Github Actions) Configuring this repo by users:
   • Generate config sections tree by parsing Kconfig: make scriptconfig PYTHONCMD=python3 SCRIPT=~/wsl2-kernel-ci/config_filter/parse_kconfig.py SCRIPT_ARG="gen_configtree" > all_sections
   • Select config sections that needs to be masked out based on the output in last step
2. Merge kernel configs:
   • Get blacklisted symbols based on blacklist_sections files: cat blacklist_sections | make scriptconfig PYTHONCMD=python3 SCRIPT=~/wsl2-kernel-ci/config_filter/parse_kconfig.py SCRIPT_ARG="get_blacklist_sym" > blacklist_syms
   • Mask overriding config (usually Ubuntu' one) using filter_config.py, symbols that are blacklisted will be deleted
   • Merge config using merge_config.py, symbols will be replaced, and =m will be replaced to =y so that linux-modules packages are not needed
3. Reconfigure the Kernel: executing yes "" | make prepare to fix the dependency issue of merged config
4. Compile and Package the Kernel:
   • WSL2's kernel version has capital letters -WSL, causing debian packaging tools goes into error
   • Patched several Makefile to lowercase the version in package name, but still uppercase in the kernel (see build.yml)

You can tweak this repo by changing blacklist_sections based on all_sections to cut down the kernel size from ~30MB to ~10MB