WSL

.wslconfig

[wsl2]
kernel=C:\\Users\\JAKA\\vmlinux

README.md

WSL notes

Rebuilding kernel with kvm support

This instructions are based on https://microhobby.com.br/blog/2019/09/21/compiling-your-own-linux-kernel-for-windows-wsl2/

1. Clone source

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

2. Reconfigure kernel

Enable kvm, as described here https://wiki.gentoo.org/wiki/QEMU#Kernel

make menuconfig KCONFIG_CONFIG=Microsoft/config-wsl

3. Build kernel

make KCONFIG_CONFIG=Microsoft/config-wsl -j8

4. Copy kernel

cp vmlinux /mnt/c/Users/<seuUser>/

5. Copy .wslconfig file to user home

Starting WSL with KVM support

1. Copy run-wsl.bat, attach.wdbg and patch_wsl_nested.js to same folder
2. Fix path in attach.wdbg
3. Open admin powershell in that folder
4. Run ./run-wsl.bat and follow instructions

attach.wdbg

bm vmcompute!Marshal::JsonParser::JsonParser ".scriptrun C:\\Users\\JAKA\\Documents\\patch_wsl_nested.js"

nix-daemon

#! /bin/sh
### BEGIN INIT INFO
# Provides:          nix-daemon
# Required-Start:
# Required-Stop:
# X-Stop-After:      sendsigs
# Default-Start:     3 4 5
# Default-Stop:      0 1 2 6
# Short-Description: Starts the nix daemon
# Description:       This is a daemon which enable the multi-user mode
#                     of the nix package manager.
### END INIT INFO

#
# Author: Michael Biebl <biebl@debian.org>
#

# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin
DESC="nix-daemon"
NAME=nix-daemon

NIX_DAEMON=nix-daemon
NIX_DAEMON_OPTIONS=--daemon
DAEMON=/nix/var/nix/profiles/per-user/root/profile/bin/nix-daemon
PIDFILE=/run/nix-daemon.pid

SCRIPTNAME=/etc/init.d/$NAME

# Exit if the package is not installed
[ -x "$DAEMON" ] || exit 0

# Read configuration variable file if it is present
[ -r /etc/default/$NAME ] && . /etc/default/$NAME

# Define LSB log_* functions.
. /lib/lsb/init-functions

do_start()
{
	# Return
	#   0 if daemon has been started
	#   1 if daemon was already running
	#   other if daemon could not be started or a failure occured
	start-stop-daemon --start --quiet --pidfile $PIDFILE --make-pidfile --exec $DAEMON --background -- $NIX_DAEMON_OPTIONS
}

do_stop()
{
	# Return
	#   0 if daemon has been stopped
	#   1 if daemon was already stopped
	#   other if daemon could not be stopped or a failure occurred
	start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE --exec $DAEMON
}

sendsigs_omit() {
	OMITDIR=/run/sendsigs.omit.d
	mkdir -p $OMITDIR
	ln -sf $PIDFILE $OMITDIR/nix-daemon
}

case "$1" in
  start)
	log_daemon_msg "Starting $DESC" "$NIX_DAEMON"
	do_start
	case "$?" in
		0) sendsigs_omit
		   log_end_msg 0 ;;
		1) log_progress_msg "already started"
		   log_end_msg 0 ;;
		*) log_end_msg 1 ;;
	esac

	;;
  stop)
	log_daemon_msg "Stopping $DESC" "$NIX_DAEMON"
	do_stop
	case "$?" in
		0) log_end_msg 0 ;;
		1) log_progress_msg "already stopped"
		   log_end_msg 0 ;;
		*) log_end_msg 1 ;;
	esac

	;;
  restart|force-reload)
	$0 stop
	$0 start
	;;
  try-restart)
	$0 status >/dev/null 2>&1 && $0 restart
	;;
  status)
	status_of_proc -p $PIDFILE $DAEMON $NIX_DAEMON && exit 0 || exit $?
	;;
  *)
	echo "Usage: $SCRIPTNAME {start|stop|restart|force-reload|try-restart|status}" >&2
	exit 3
	;;
esac

:

patch_wsl_nested.js

"use strict";

function initializeScript()
{
    return [new host.apiVersionSupport(1, 3)];
}

function continueExecution() {
    var cmd = "g";
    host.diagnostics.debugLog(cmd);
    var lines = host.namespace.Debugger.Utility.Control.ExecuteCommand(cmd)
    for (var line of lines) host.diagnostics.debugLog("  ", line, "\n");
}

function invokeScript()
{
    /* bp vmcompute!Marshal::JsonParser::JsonParser */

    var cmd;
    var lines;

    // 1. Check if WSL
    var magic = host.memory.readWideString(host.currentThread.Registers.User.rdx, 14);
    if (magic == '{"Owner":"WSL"') {
        host.diagnostics.debugLog("IS WSL\n");
    } else {
        host.diagnostics.debugLog("IS NOT WSL request\n");
        return continueExecution();
    }

    // dump length and read machine spec json
    var len = host.currentThread.Registers.User.r8;
    host.diagnostics.debugLog("String length: ", len, " dumping memory: ", host.currentThread.Registers.User.rdx, "\n");
    var jsonString = host.memory.readWideString(host.currentThread.Registers.User.rdx, len);
    host.diagnostics.debugLog("Before: ", jsonString, "\n");

    // parse and modify machine spec json
    var machineSpec = JSON.parse(jsonString);
    machineSpec.VirtualMachine.ComputeTopology.Processor.ExposeVirtualizationExtensions = true;
    var machineSpecJson = JSON.stringify(machineSpec);
    host.diagnostics.debugLog("After:  ", JSON.stringify(machineSpec), "\n");
    var newLen = "0x" + machineSpecJson.length.toString(16);

    // allocate memory
    cmd = ".dvalloc 4096"
    lines = host.namespace.Debugger.Utility.Control.ExecuteCommand(cmd)
    var addr = lines[0];
    var addrParts = addr.split(" ");
    var freeMem = addrParts[addrParts.length-1].replace("`", "");
    host.diagnostics.debugLog("Allocated ", freeMem, "\n");
    
    // write memory
    host.diagnostics.debugLog("Writing memory ", freeMem, " length: ", newLen, "\n");
    cmd = "eu " + freeMem + ' "' + machineSpecJson.split("\\").join("\\\\").split('"').join('\\"') + '"';
    lines = host.namespace.Debugger.Utility.Control.ExecuteCommand(cmd)
    for (var line of lines) host.diagnostics.debugLog("  ", line, "\n");

    // patch rdx with new memory
    var cmd = "r @rdx = " + freeMem;
    host.diagnostics.debugLog(cmd);
    var lines = host.namespace.Debugger.Utility.Control.ExecuteCommand(cmd)
    for (var line of lines) host.diagnostics.debugLog("  ", line, "\n");

    // patch r8 with new memory size
    var cmd = "r @r8 = " + newLen;
    host.diagnostics.debugLog(cmd);
    var lines = host.namespace.Debugger.Utility.Control.ExecuteCommand(cmd)
    for (var line of lines) host.diagnostics.debugLog("  ", line, "\n");

    return continueExecution();
}

run-wsl.bat

REM Ensure vmcompute.exe is running
wsl.exe --shutdown
wsl.exe -e true
REM Listen for and Intercept utility vm creation
start Windbgx.exe -pn vmcompute.exe -c "$$<attach.wdbg;g"
REM Ensure WSL Utility VM is not running (hopefully windb starts up fast enough...)
net stop LxssManager
net start LxssManager
echo "Press Enter if the debugger is running"
pause
REM Start WSL
start wsl.exe
echo "Detach debugger from process, check if you have kvm support using kvm-ok command"