Not a full review. Just one blocking problem
>
> }
> + case MULTIBOOT_LOAD_TYPE_PE:
> + grub_fatal ("Unsupported load type: %u\n", mld.load_type);
> + default:
> + /* should be impossible */
> + grub_fatal ("Unknown load type: %u\n", mld.load_type);
>
Don't use grub_fatal for this. grub_fatal is only when continue to execute
grub is unwise. Here you just have an unsupported file. This is definitely
a GRUB_ERR_BAD_OS
>
