Subject: [PATCH 2/2] image: Add new efi32-raw format for 32bit UEFI on 64bit systems

From: Denis 'GNUtoo' Carikli <[email-masked]>
Date: Tue, 10 May 2022 01:24:51 +0200

* gnu/bootloader/grub.scm (grub-efi32-bootloader): New variable.
  (install-grub-efi32): New variable
* gnu/build/bootloader.scm (install-efi32-loader): New variable.
  (install-efi32-loader): New variable.
* gnu/build/image.scm (initialize-efi32-partition): New variable
* gnu/packages/bootloaders.scm (grub-efi32): New variable.
* gnu/system/image.scm (esp32-partition): New variable
  (efi32-disk-image): New variable
  (efi32-raw-image-type): New variable.
  (partition-image): Add partition-image keyword
---
 gnu/bootloader/grub.scm      | 32 +++++++++++++++++++++++++
 gnu/build/bootloader.scm     | 46 +++++++++++++++++++++++++++++++++++-
 gnu/build/image.scm          |  9 +++++++
 gnu/packages/bootloaders.scm | 13 ++++++++++
 gnu/system/image.scm         | 19 +++++++++++++++
 5 files changed, 118 insertions(+), 1 deletion(-)

diff --git a/gnu/bootloader/grub.scm b/gnu/bootloader/grub.scm
index 120cd55012..1ea356030f 100644
--- a/gnu/bootloader/grub.scm
+++ b/gnu/bootloader/grub.scm
@@ -7,6 +7,7 @@
 ;;; Copyright © 2019, 2020 Miguel Ángel Arruga Vivas <[email-masked]>
 ;;; Copyright © 2020 Maxim Cournoyer <[email-masked]>
 ;;; Copyright © 2020 Stefan <[email-masked]>
+;;; Copyright © 2022 Denis 'GNUtoo' Carikli <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -54,6 +55,7 @@ (define-module (gnu bootloader grub)
 
             grub-bootloader
             grub-efi-bootloader
+            grub-efi32-bootloader
             grub-efi-netboot-bootloader
             grub-mkrescue-bootloader
             grub-minimal-bootloader
@@ -608,6 +610,29 @@ (define install-grub-efi
                         "--bootloader-id=Guix"
                         "--efi-directory" target-esp)))))
 
+(define install-grub-efi32
+  #~(lambda (bootloader efi-dir mount-point)
+      ;; There is nothing useful to do when called in the context of a disk
+      ;; image generation.
+      (when efi-dir
+        ;; Install GRUB onto the EFI partition mounted at EFI-DIR, for the
+        ;; system whose root is mounted at MOUNT-POINT.
+        (let ((grub-install (string-append bootloader "/sbin/grub-install"))
+              (install-dir (string-append mount-point "/boot"))
+              ;; When installing Guix, it's common to mount EFI-DIR below
+              ;; MOUNT-POINT rather than /boot/efi on the live image.
+              (target-esp (if (file-exists? (string-append mount-point efi-dir))
+                              (string-append mount-point efi-dir)
+                              efi-dir)))
+          ;; Tell 'grub-install' that there might be a LUKS-encrypted /boot or
+          ;; root partition.
+          (setenv "GRUB_ENABLE_CRYPTODISK" "y")
+          (invoke/quiet grub-install "--boot-directory" install-dir
+                        "--bootloader-id=Guix"
+			(cond ((target-x86?) "--target=i386-efi")
+                              ((target-arm?) "--target=arm-efi"))
+                        "--efi-directory" target-esp)))))
+
 (define (install-grub-efi-netboot subdir)
   "Define a grub-efi-netboot bootloader installer for installation in SUBDIR,
 which is usually efi/Guix or efi/boot."
@@ -734,6 +759,13 @@ (define grub-efi-bootloader
    (name 'grub-efi)
    (package grub-efi)))
 
+(define grub-efi32-bootloader
+  (bootloader
+   (inherit grub-efi-bootloader)
+   (installer install-grub-efi32)
+   (name 'grub-efi32)
+   (package grub-efi32)))
+
 (define grub-efi-netboot-bootloader
   (bootloader
    (inherit grub-efi-bootloader)
diff --git a/gnu/build/bootloader.scm b/gnu/build/bootloader.scm
index 9a89fe55cb..d41143d98e 100644
--- a/gnu/build/bootloader.scm
+++ b/gnu/build/bootloader.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2017 Mathieu Othacehe <[email-masked]>
 ;;; Copyright © 2019 Ludovic Courtès <[email-masked]>
+;;; Copyright © 2022 Denis 'GNUtoo' Carikli <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -25,7 +26,8 @@ (define-module (gnu build bootloader)
   #:use-module (rnrs io ports)
   #:use-module (rnrs io simple)
   #:export (write-file-on-device
-            install-efi-loader))
+            install-efi-loader
+            install-efi32-loader))
 
 
 ;;;
@@ -81,6 +83,29 @@ (define (install-efi grub grub-config esp)
             ;; Graft the configuration file onto the image.
             (string-append "boot/grub/grub.cfg=" grub-config))))
 
+(define (install-efi32 grub grub-config esp)
+  "Write a self-contained GRUB EFI 32bit 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 "3.5.1.1 Removable Media Boot Behaviour":
+         ;; http://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_6.pdf
+         (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 ((target-x86?)
+                             '("i386-efi" . "BOOTIA32.EFI"))
+                            ((target-arm?)
+                             '("arm-efi" . "BOOTARM.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."
@@ -99,3 +124,22 @@ (define (install-efi-loader grub-efi esp)
                configfile /boot/grub/grub.cfg~%")))
     (install-efi grub-efi grub-config esp)
     (delete-file grub-config)))
+
+(define (install-efi32-loader grub-efi32 esp)
+  "Install in ESP directory the given GRUB-EFI 32bit 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~@
+               insmod part_gpt~@
+               search --set=root --label Guix_image~@
+               configfile /boot/grub/grub.cfg~%")))
+    (install-efi32 grub-efi32 grub-config esp)
+    (delete-file grub-config)))
diff --git a/gnu/build/image.scm b/gnu/build/image.scm
index 81caa424f8..bae747494f 100644
--- a/gnu/build/image.scm
+++ b/gnu/build/image.scm
@@ -5,6 +5,7 @@
 ;;; Copyright © 2017 Marius Bakke <[email-masked]>
 ;;; Copyright © 2020, 2022 Tobias Geerinckx-Rice <[email-masked]>
 ;;; Copyright © 2020 Mathieu Othacehe <[email-masked]>
+;;; Copyright © 2022 Denis 'GNUtoo' Carikli <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -40,6 +41,7 @@ (define-module (gnu build image)
             convert-disk-image
             genimage
             initialize-efi-partition
+            initialize-efi32-partition
             initialize-root-partition
 
             make-iso9660-image))
@@ -162,6 +164,13 @@ (define* (initialize-efi-partition root
   "Install in ROOT directory, an EFI loader using GRUB-EFI."
   (install-efi-loader grub-efi root))
 
+(define* (initialize-efi32-partition root
+                                     #:key
+                                     grub-efi32
+                                     #:allow-other-keys)
+  "Install in ROOT directory, an EFI 32bit loader using GRUB-EFI32."
+  (install-efi32-loader grub-efi32 root))
+
 (define* (initialize-root-partition root
                                     #:key
                                     bootcfg
diff --git a/gnu/packages/bootloaders.scm b/gnu/packages/bootloaders.scm
index 7ea6f5a647..f133d9f604 100644
--- a/gnu/packages/bootloaders.scm
+++ b/gnu/packages/bootloaders.scm
@@ -15,6 +15,7 @@
 ;;; Copyright © 2020, 2021 Pierre Langlois <[email-masked]>
 ;;; Copyright © 2021 Vincent Legoll <[email-masked]>
 ;;; Copyright © 2021 Brice Waegeneire <[email-masked]>
+;;; Copyright © 2022 Denis 'GNUtoo' Carikli <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -332,6 +333,18 @@ (define-public grub-efi
                                        "/bin/mcopy\"")))
                      #t))))))))))
 
+(define-public grub-efi32
+  (package
+    (inherit grub-efi)
+    (name "grub-efi32")
+    (synopsis "GRand Unified Boot loader (UEFI 32bit version)")
+    (arguments
+     `(,@(substitute-keyword-arguments (package-arguments grub-efi)
+           ((#:configure-flags flags
+             ''()) `(cons* ,(cond ((target-x86?) "--target=i386")
+                                  ((target-arm?) "--target=arm"))
+                           ,flags)))))))
+
 ;; Because grub searches hardcoded paths it's easiest to just build grub
 ;; again to make it find both grub-pc and grub-efi.  There is a command
 ;; line argument which allows you to specify ONE platform - but
diff --git a/gnu/system/image.scm b/gnu/system/image.scm
index 42e215f614..e35c54ca50 100644
--- a/gnu/system/image.scm
+++ b/gnu/system/image.scm
@@ -1,6 +1,7 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2020, 2021 Mathieu Othacehe <[email-masked]>
 ;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <[email-masked]>
+;;; Copyright © 2022 Denis 'GNUtoo' Carikli <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -65,6 +66,7 @@ (define-module (gnu system image)
             root-label
 
             esp-partition
+            esp32-partition
             root-partition
 
             efi-disk-image
@@ -74,6 +76,7 @@ (define-module (gnu system image)
 
             image-with-os
             efi-raw-image-type
+            efi32-raw-image-type
             qcow2-image-type
             iso-image-type
             uncompressed-iso-image-type
@@ -109,6 +112,11 @@ (define esp-partition
    (flags '(esp))
    (initializer (gexp initialize-efi-partition))))
 
+(define esp32-partition
+  (partition
+   (inherit esp-partition)
+   (initializer (gexp initialize-efi32-partition))))
+
 (define root-partition
   (partition
    (size 'guess)
@@ -122,6 +130,11 @@ (define efi-disk-image
    (format 'disk-image)
    (partitions (list esp-partition root-partition))))
 
+(define efi32-disk-image
+  (image
+   (format 'disk-image)
+   (partitions (list esp32-partition root-partition))))
+
 (define iso9660-image
   (image
    (format 'iso9660)
@@ -163,6 +176,11 @@ (define efi-raw-image-type
    (name 'efi-raw)
    (constructor (cut image-with-os efi-disk-image <>))))
 
+(define efi32-raw-image-type
+  (image-type
+   (name 'efi32-raw)
+   (constructor (cut image-with-os efi32-disk-image <>))))
+
 (define qcow2-image-type
   (image-type
    (name 'qcow2)
@@ -352,6 +370,7 @@ (define (partition-image partition)
                                                 #$(image-shared-store? image))
                               #:system-directory #$os
                               #:grub-efi #+grub-efi
+                              #:grub-efi32 #+grub-efi32
                               #:bootloader-package
                               #+(bootloader-package bootloader)
                               #:bootloader-installer
-- 
2.36.0