How to return control to GRUB

[Fabian Greffrath]

Dear GRUB developers,

I take care of the Debian package 'grub-invaders'. This is a multiboot
compliant kernel-game that resembles Space Invaders, but I guess you
knew that already.

One thing that annoys me about the game is, that you cannot return to
the GRUB menu. The only chance to leave the game is rebooting the
machine.

I'd like to implement a feature that makes the game return the control
back to GRUB when the ESC key is pressed (I wrote a small patch which
called the PC-BIOS cold-boot routine as found in GRUB, but this of
course will not work with iee1275 or linuxbios). Robert Milan already
pointed me to the multiboot docs, but I did not find what I was looking
for.

Can you please help me find the information needed to implement this
feature?

Thank you very much.

Cheers,
Fabian