Feature Request: Debian/x32 VM (or x32-enabled amd64)

[mirabilos]

I can test most architectures by cross-compiling and with qemu-user, or with jirutka/setup-alpine or vmactions.

However, x32 (amd64ilp32, not to be confused with i386) still elides me.

Notably, x32 only exists in Debian-Ports, not in any released distribution, and as such is a moving target, so installing an x32 system will be tricky. If you wish to do that, I’ll certainly help (best to coordinate this in #debian-ports on OFTC IRC, where the main porter (cbmuser) also sits).

If not, I’d like to request a Debian/amd64 VM with syscall.x32=y added to GRUB_CMDLINE_LINUX in /etc/default/grub (and sudo update-grub ran once afterwards). The x32 architecture uses the standard amd64 kernel but a different syscall ABI surface which needs to be explicitly enabled because it is nowhere near as well-tested (also for security fuzzing), and the standard runners don’t have that, so one cannot use an x32 Docker image on them.

Users could then create a Debian/x32 chroot on the VM during test runs, with debootstrap. (Incidentally, i386 as well, which was recently removed as full architecture.)

[neilpang]

how to build the qcow2 file for amd64ilp32 ?

[mirabilos]

On Mon, 8 Dec 2025, neil wrote: how to build the qcow2 file for amd64ilp32 ?

I guess it’s complicated, especially if you need to also boot it. You need to mix amd64 and x32 packages in the target system, but you need a host whose kernel has the syscall.x32=y flag set to even be able to run the postinst in the chroot… … and qemu-user doesn’t do x32, either. Perhaps the best mix between effort to create the image and action runtime would be to create an amd64 install, change the kernel flag, run update-grub, and create an x32 chroot under /srv/x32 or something which one can then chroot into. Perhaps pre-populate bind mounts for everything (/dev, /dev/shm, /proc, /sys, /tmp). I can help with that. The tricky part about this is that the chroot creation must be done within the booted VM. You can create the baseline amd64 VM with debian-installer or any other bootstrapping method, even cross, but not the chroot for x32…