Enable EBPF on WSL2

enable_ebpf_on_wsl2

By default, EBPF programs will not run on WSL2 due to required kernel modules missing. The following example error is an 
indication of this problem:
  modprobe: ERROR: ../libkmod/libkmod.c:586 kmod_search_moddep() could not open moddep file '/lib/modules/4.19.84-microso
  ft-standard/modules.dep.bin'
  modprobe: FATAL: Module kheaders not found in directory /lib/modules/4.19.84-microsoft-standard
  chdir(/lib/modules/4.19.84-microsoft-standard/build): No such file or directory

To fix this you need to rebuild the WSL2 kernel with the missing kernel modules. The below instructions are for Ubuntu 18.04 WSL2.

1. git clone https://github.com/microsoft/WSL2-Linux-Kernel.git
2. cd WSL2-Linux-Kernel
3. sudo apt install flex bison build-essential libelf-dev libncurses-dev  libssl-dev
4. cp Microsoft/config-wsl .config
5. Add the kernel flags specified in https://github.com/iovisor/bcc/blob/master/INSTALL.md#kernel-configuration to .config
6. export KERNELRELEASE=4.19.84-microsoft-standard 
    NOTE: Make sure the version corresponds to the version of WSL2. Run: uname -a
7. make KERNELRELEASE=$KERNELRELEASE -j 4
8. make KERNELRELEASE=$KERNELRELEASE modules -j 4
9. sudo make KERNELRELEASE=$KERNELRELEASE modules_install 
10. (confirm you can see files under /lib/modules/$(uname -r))
11. sudo mount -t debugfs debugfs /sys/kernel/debug (for any apps that uses it since its not mounted by default)

Hi, @MetaT1an @satanshiro,

Have you tried using the following command

export KERNELRELEASE=$(uname -r)

to replace the original one in https://gist.github.com/MarioHewardt/5759641727aae880b29c8f715ba4d30f#file-enable_ebpf_on_wsl2-L15

For me, I can see the new content in /lib/modules/$(uname -r) after rebuilding the kernel.

The kernel KERNELRELEASE should have -WSL2 as the suffix.

Thank you! It works!