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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2017 Mathieu Othacehe <>
;;; Copyright © 2019 Ludovic Courtès <>
;;; This file is part of GNU Guix.
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;; GNU Guix is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; GNU General Public License for more details.
;;; You should have received a copy of the GNU General Public License
;;; along with GNU Guix. If not, see <>.
(define-module (gnu build bootloader)
#:use-module (guix build utils)
#:use-module (guix utils)
#:use-module (ice-9 binary-ports)
#:use-module (ice-9 format)
#:export (write-file-on-device
;;; Writing utils.
(define (write-file-on-device file size device offset)
"Write SIZE bytes from FILE to DEVICE starting at OFFSET."
(call-with-input-file file
(lambda (input)
(let ((bv (get-bytevector-n input size)))
(call-with-output-file device
(lambda (output)
(seek output offset SEEK_SET)
(put-bytevector output bv))
#:binary #t)))))
;;; EFI bootloader.
(define (install-efi grub grub-config esp)
"Write a self-contained GRUB EFI loader to the mounted ESP using GRUB-CONFIG."
(let* ((system %host-type)
;; Hard code the output location to a well-known path recognized by
;; compliant firmware. See " Removable Media Boot Behaviour":
(grub-mkstandalone (string-append grub "/bin/grub-mkstandalone"))
(efi-directory (string-append esp "/EFI/BOOT"))
;; Map grub target names to boot file names.
(efi-targets (cond ((string-prefix? "x86_64" system)
'("x86_64-efi" . "BOOTX64.EFI"))
((string-prefix? "i686" system)
'("i386-efi" . "BOOTIA32.EFI"))
((string-prefix? "armhf" system)
'("arm-efi" . "BOOTARM.EFI"))
((string-prefix? "aarch64" system)
'("arm64-efi" . "BOOTAA64.EFI")))))
;; grub-mkstandalone requires a TMPDIR to prepare the firmware image.
(setenv "TMPDIR" esp)
(mkdir-p efi-directory)
(invoke grub-mkstandalone "-O" (car efi-targets)
"-o" (string-append efi-directory "/"
(cdr efi-targets))
;; Graft the configuration file onto the image.
(string-append "boot/grub/grub.cfg=" grub-config))))
(define (install-efi-loader grub-efi esp)
"Install in ESP directory the given GRUB-EFI bootloader. Configure it to
load the Grub bootloader located in the 'Guix_image' root partition."
(let ((grub-config "grub.cfg"))
(call-with-output-file grub-config
(lambda (port)
;; Create a tiny configuration file telling the embedded grub where to
;; load the real thing. XXX This is quite fragile, and can prevent
;; the image from booting when there's more than one volume with this
;; label present. Reproducible almost-UUIDs could reduce the risk
;; (not eliminate it).
(format port
"insmod part_msdos~@
search --set=root --label Guix_image~@
configfile /boot/grub/grub.cfg~%")))
(install-efi grub-efi grub-config esp)
(delete-file grub-config)))