I spent an unreasonable amount of time working on grub2. The stuff I looked at the most where the uefi spec http://wiki.phoenix.com/wiki/index.php/Category:UE

I spent an unreasonable amount of time working on grub2. The stuff I looked at the most where the uefi spec http://wiki.phoenix.com/wiki/index.php/Category:UEFI http://wiki.phoenix.com/wiki/index.php/Category:UEFI And then the uefi stub code in the Linux kernel, as well as the grub2 source code. It’s not too hard to figure out the flow in grub2, just figure out where it does EXIT_BOOT_SERVICES and work from there.