HVM Debugging

Qubes 4.0 windows debugging

Advanced guest Windows HVM debugging requires host (win7dbg) and target VM (win7new) configuration. The following text provides instructions to set up debugging with a virtual serial port in the Qubes 4.0 environment.

There are two main issues to be adopted to get all things to work.

Add a virtual serial port

Qemu in the stub domain with virtual serial port added in a recommended way (<serial type="pty"/>) fails to start (Could not open '/dev/hvc1': No such device). It seems like a lack of multiple xen consoles support/configuration. The only way that I have found is to attach serial port explicitly to the available console.

1. Unpack stub domain in dom0:

$ mkdir stubroot
$ cp /usr/lib/xen/boot/stubdom-linux-rootfs stubroot/stubdom-linux-rootfs.gz
$ cd stubroot
$ gunzip stubdom-linux-rootfs.gz
$ cpio -i -d -H newc --no-absolute-filenames < stubdom-linux-rootfs
$ rm stubdom-linux-rootfs

2. Edit Init script to remove last loop and to add "-serial /dev/hvc0" to the qemu command line.

3. Apply changes:

$ find . -print0 | cpio --null -ov --format=newc | gzip -9 > ../stubdom-linux-rootfs
$ sudo mv ../stubdom-linux-rootfs /usr/lib/xen/boot

Connect two consoles

Run the following script:

debugname1=win7new
debugname2=win7dbg
id1=$(xl domid "$debugname1-dm")
id2=$(xl domid "$debugname2-dm")

tty1=$(xenstore-read /local/domain/${id1}/console/tty)
tty2=$(xenstore-read /local/domain/${id1}/console/tty)

socat tty1,raw $tty2,raw