[bug#73927] [PATCH v3 03/17] bootloader: grub: Remove hardcoded partition number for the Hurd.

[Janneke Nieuwenhuizen <janneke@gnu.org>]

This supports using another than the default DISK0 PART1 and using LABEL or
UUID as root file-system specifier.  It still defaults to DISK0 PART1 if
the file-system cannot be found, i.e., lives only at the build side: A
virtual machine/childhurd build.

* gnu/bootloader/grub.scm (%device-spec-regexp): New variable.
(string->device-spec, device-spec->hurd-device): Use it in new procedures.
(device->hurd-device): New procedure.
(make-grub-configuration): Use them to remove hardcoded partition
number (root-index 1).

Change-Id: I49fa93dacc09883dfb4d695402c5eac2e0e17286
---
 gnu/bootloader/grub.scm | 42 +++++++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 6 deletions(-)

diff --git a/gnu/bootloader/grub.scm b/gnu/bootloader/grub.scm
index 2723eda5f4..c929af691b 100644
--- a/gnu/bootloader/grub.scm
+++ b/gnu/bootloader/grub.scm
@@ -3,7 +3,7 @@
 ;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
 ;;; Copyright © 2017 Leo Famulari <leo@famulari.name>
 ;;; Copyright © 2017, 2020 Mathieu Othacehe <m.othacehe@gmail.com>
-;;; Copyright © 2019, 2020, 2023 Janneke Nieuwenhuizen <janneke@gnu.org>
+;;; Copyright © 2019, 2020, 2023, 2024 Janneke Nieuwenhuizen <janneke@gnu.org>
 ;;; Copyright © 2019, 2020 Miguel Ángel Arruga Vivas <rosen644835@gmail.com>
 ;;; Copyright © 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com>
 ;;; Copyright © 2020 Stefan <stefan-guix@vodafonemail.de>
@@ -34,6 +34,7 @@ (define-module (gnu bootloader grub)
   #:use-module (guix gexp)
   #:use-module (gnu artwork)
   #:use-module (gnu bootloader)
+  #:use-module (gnu build file-systems)
   #:use-module (gnu system uuid)
   #:use-module (gnu system file-systems)
   #:use-module (gnu system keyboard)
@@ -45,6 +46,7 @@ (define-module (gnu bootloader grub)
   #:use-module (ice-9 regex)
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-2)
+  #:use-module (srfi srfi-26)
   #:export (grub-theme
             grub-theme?
             grub-theme-image
@@ -355,6 +357,34 @@ (define (grub-root-search device file)
         ((or #f (? string?))
          #~(format #f "search --file --set ~a" #$file)))))
 
+(define %device-spec-regexp "/dev/[hsvw]d([abcd])([0-9]*)")
+(define (string->device-spec str)
+  "Return device spec STR as /dev/XdYZ, also catering for uuid or label."
+  (cond ((string-match %device-spec-regexp str)
+         str)
+        ((string->uuid str)
+         =>
+         find-partition-by-uuid)
+        (else
+         (find-partition-by-label str))))
+
+(define* (device-spec->hurd-device device-spec #:key (disk "w"))
+  "Return DEVICE-SPEC as a Hurd device spec:
+     part:PART-NUMBER:device:DISKdDISK-INDEX
+Default to part:1:device:DISKd0 if partition cannot be found."
+  (let* ((m (and=> device-spec (cute string-match %device-spec-regexp <>)))
+         (disk-char (and m (and=> (match:substring m 1) (compose car string->list))))
+         (disk-index (or (and disk-char (- (char->integer disk-char) (char->integer #\a)))
+                         0))
+         (partition-number (or (and m (and=> (match:substring m 2) string->number))
+                               1)))
+    (format #f "part:~a:device:~ad~a" partition-number disk disk-index)))
+
+(define* (device->hurd-device device #:key (disk "w"))
+  "Return DEVICE as a Hurd device spec: part:PART-NUMBER:device:DISKdDISK-INDEX."
+  (let ((device-spec (canonicalize-device-spec device)))
+    (device-spec->hurd-device device-spec #:disk disk)))
+
 (define* (make-grub-configuration grub config entries
                                   #:key
                                   (locale #f)
@@ -413,16 +443,16 @@ (define (menu-entry->gexp entry)
                ;; IDE driver ("hdX") and those understood by rumpdisk ("wdX"
                ;; in the "noide" case).
                (disk (if (member "noide" arguments) "w" "h"))
-               (modules (menu-entry-multiboot-modules entry))
-               (root-index 1))          ; XXX EFI will need root-index 2
+               (device-string (file-system-device->string device))
+               (device-spec (and=> device-string string->device-spec))
+               (modules (menu-entry-multiboot-modules entry)))
           #~(format port "
 menuentry ~s {
-  multiboot ~a root=part:~a:device:~ad0~a~a
+  multiboot ~a root=~a~a~a
 }~%"
                     #$label
                     #$kernel
-                    #$root-index
-                    #$disk
+                    #$(device-spec->hurd-device device-spec #:disk disk)
                     (string-join (list #$@arguments) " " 'prefix)
                     (string-join (map string-join '#$modules)
                                  "\n  module " 'prefix))))
-- 
2.46.0