gnu: grub: Cross-build fix for system i686-linux.

* gnu/packages/patches/grub-cross-system-i686.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/bootloaders.scm (grub): Use it.

gnu/local.mk

@@ -1048,6 +1048,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/grocsvs-dont-use-admiral.patch		\
   %D%/packages/patches/gromacs-tinyxml2.patch			\
   %D%/packages/patches/groovy-add-exceptionutilsgenerator.patch	\
+  %D%/packages/patches/grub-cross-system-i686.patch		\
   %D%/packages/patches/grub-efi-fat-serial-number.patch		\
   %D%/packages/patches/grub-setup-root.patch			\
   %D%/packages/patches/grub-verifiers-Blocklist-fallout-cleanup.patch \

gnu/packages/bootloaders.scm

@@ -2,7 +2,7 @@
 ;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015, 2018 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2015 Leo Famulari <leo@famulari.name>
-;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
+;;; Copyright © 2016, 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
 ;;; Copyright © 2016, 2017, 2018 Marius Bakke <mbakke@fastmail.com>
 ;;; Copyright © 2016, 2017 Danny Milosavljevic <dannym@scratchpost.org>
 ;;; Copyright © 2016, 2017 David Craven <david@craven.ch>
@@ -11,7 +11,6 @@
 ;;; Copyright © 2019 nee <nee@cock.li>
 ;;; Copyright © 2019 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;; Copyright © 2020 Björn Höfling <bjoern.hoefling@bjoernhoefling.de>
-;;; Copyright © 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
 ;;; Copyright © 2018, 2019, 2020 Vagrant Cascadian <vagrant@debian.org>
 ;;; Copyright © 2020 Pierre Langlois <pierre.langlois@gmx.com>
 ;;;
@@ -97,7 +96,8 @@
              (patches (search-patches
                        "grub-efi-fat-serial-number.patch"
                        "grub-setup-root.patch"
-                       "grub-verifiers-Blocklist-fallout-cleanup.patch"))))
+                       "grub-verifiers-Blocklist-fallout-cleanup.patch"
+                       "grub-cross-system-i686.patch"))))
     (build-system gnu-build-system)
     (arguments
      `(#:configure-flags

gnu/packages/patches/grub-cross-system-i686.patch

@@ -0,0 +1,79 @@
+Not upstreamed.
+Fixes cross-build for the Hurd, from i686-linux,
+see <https://bugs.gnu.org/41982>.
+
+From 270667540146f8ef9ea7a44258a71b3837a7af4a Mon Sep 17 00:00:00 2001
+From: "Jan (janneke) Nieuwenhuizen" <janneke@gnu.org>
+Date: Sun, 21 Jun 2020 15:10:40 +0200
+Subject: [PATCH] grub-core: Build fixes for i386
+
+* grub-core/lib/i386/relocator64.S: Avoid x86_64 instructions on i386.
+---
+ grub-core/lib/i386/relocator64.S | 26 +++++++++++++++++++++++++-
+ 1 file changed, 25 insertions(+), 1 deletion(-)
+
+diff --git a/grub-core/lib/i386/relocator64.S b/grub-core/lib/i386/relocator64.S
+index 148f38adb..45fed9444 100644
+--- a/grub-core/lib/i386/relocator64.S
++++ b/grub-core/lib/i386/relocator64.S
+@@ -63,7 +63,9 @@ VARIABLE(grub_relocator64_cr3)
+ 	movq	%rax, %cr3
+ #endif
+ 
++#ifdef __x86_64__
+ 	.code64
++#endif
+ 
+ 	/* mov imm64, %rax */
+ 	.byte 	0x48
+@@ -71,7 +73,14 @@ VARIABLE(grub_relocator64_cr3)
+ VARIABLE(grub_relocator64_rsp)
+ 	.quad	0
+ 
++#ifndef __x86_64__
++	/* movq	%rax, %rsp */
++	.byte 	0x48
++	.byte	0x89
++	.byte	0xc4
++#else
+ 	movq	%rax, %rsp
++#endif
+ 
+ #ifdef GRUB_MACHINE_EFI
+ 	jmp	LOCAL(skip_efi_stack_align)
+@@ -95,8 +104,15 @@ LOCAL(skip_efi_stack_align):
+ VARIABLE(grub_relocator64_rsi)
+ 	.quad	0
+ 
++#ifndef	__x86_64__
++	/* movq	%rax, %rsi */
++	.byte 	0x48
++	.byte	0x89
++	.byte 	0xc6
++#else
+ 	movq	%rax, %rsi
+-	
++#endif
++
+ 	/* mov imm64, %rax */
+ 	.byte 	0x48
+ 	.byte	0xb8
+@@ -128,6 +144,14 @@ VARIABLE(grub_relocator64_rdx)
+ #ifdef __APPLE__
+ 	.byte 0xff, 0x25
+ 	.quad 0
++#elif !defined (__x86_64__)
++	/* jmp *LOCAL(jump_addr) (%rip) */
++	.byte 0xff
++        .byte 0x25
++	.byte 0
++	.byte 0
++	.byte 0
++	.byte 0
+ #else
+ 	jmp *LOCAL(jump_addr) (%rip)
+ #endif
+-- 
+Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
+Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com
+