Enable CONFIG_IKHEADERS=m in WSL kernel

[ahupp]

Is your feature request related to a problem? Please describe.
I'm using BPF to build profiling tools. This depends on having kernel headers that match the currently running kernel. However, there's (of course) no -headers package in debian for the MS kernel. I can probably pull the kernel source from github and use those headers but this a bit of a pain.

Describe the solution you'd like
Modern kernels can be packaged with the headers as a kernel module using CONFIG_IKHEADERS=m. This is the simplest way to make sure there's headers available that are in sync with the running kernel, esp if that kernel is distributed outside of the distribution I'm running.

Describe alternatives you've considered
I could maybe try to run a stock kernel (this works in WSL2, yes?), or download the headers, but that seems more error prone than the proposal.

Additional context
N/A

[benhillis]

I like this suggestion, I will see about adding this support. Looks like 4.19 does not support this config flag, but we are moving to 5.4 "soon".

[therealkenc]

Heads up archivemount, at least as a thought experiment if not an entirely serious proposal. Given that the idea of a cross-distro /usr/lib/wsl/lib automount has been entertained, /usr/lib/wsl/include/kernel is not a long walk, philosophically. Just sayin'.

[chadbrewbaker]

@benhillis stupid question. I have the git branch for 4.19.104-microsoft-standard built. What are the steps for copying the kernel headers to to a linux-headers-4.19.104-microsoft-standard directory for bpf tools? Ubuntu20.04 if it matters.

[chadbrewbaker]

Figured it out. Aww yeah ... BPF tools under WSL2 🥳

cd /path/to/WSL2-Linux-Kernel #check out branch corresponding to uname -r tag
make KCONFIG_CONFIG=Microsoft/config-wsl
sudo ln /path/to/WSL2-Linux-Kernel -s /lib/modules/4.19.104-microsoft-standard/build

[jthoward64]

Any progress on this issue now that 5.4 is way further along?

[ThomsonTan]

Any progress on this issue since 5.10 was released for some time?

[MageekChiu]

Wondering this myself

[danielkatz]

@benhillis Can we get an update of this proposal? It's a trivial (as far as i understand it) change that'll lower the bar for entry to the already complicated enough world of eBPF programming.

[clouds56]

Let's moving forward on this, there are lots of user scenarios requiring linux-headers. Most of them are following some scripts or tech blogs asking apt install linux-headers-$(uname -r), so it might be hard for them to sync git and build linux just for headers every month.

e.g. #11942 #11596 #11557 #10967 #10913 #10069 (comment) #7437 #6650 #6635 #4132 #4128 #3235 #2649 #2363

It would be great to take advantage of github actions in https://github.com/microsoft/WSL2-Linux-Kernel that build headers at release.

For those who have to built headers themselves and lost in many dup issues.

git clone https://github.com/microsoft/WSL2-Linux-Kernel.git
cd WSL2-Linux-Kernel

We need to update config

# cp -af Microsoft/config-wsl .config # if use default config
zcat /proc/config.gz > .config # if use current config
sudo make INSTALL_HDR_PATH=/usr/lib/modules/"$(uname -r)"/build headers_install