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


>