[PATCH 2/2] img/combined: avoid chainloading in GRUB

[Alyssa Ross <hi@alyssa.is>]

Some UEFI implementations (like the one on Ville's Thinkpad P43s)
failed to chainload Spectrum from GRUB.  Now that Spectrum has a
proper bootloader, we can avoid that chainloading entirely, which will
hopefully make the broken firmware happier.

Reported-by: Ville Ilvonen <ville.ilvonen@unikie.com>
Cc: Puck Meerburg <puck@puckipedia.com>
---
 img/combined/default.nix | 10 ++++++++++
 img/combined/grub.cfg.in |  5 +++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/img/combined/default.nix b/img/combined/default.nix
index 86e07e2..16cd506 100644
--- a/img/combined/default.nix
+++ b/img/combined/default.nix
@@ -35,6 +35,16 @@ let
 
   grubCfg = substituteAll {
     src = ./grub.cfg.in;
+
+    nativeBuildInputs = [ mtools ];
+
+    preInstall = ''
+      export spectrumKernelParams="$(
+          mcopy -i ${eosimages.image}@@1M ::/loader/entries/spectrum.conf - |
+          grep '^options ' |
+          sed 's/^options //')"
+    '';
+
     linux = removePrefix storeDir installer.kernel;
     initrd = removePrefix storeDir installer.initramfs;
     inherit (installer) kernelParams;
diff --git a/img/combined/grub.cfg.in b/img/combined/grub.cfg.in
index 1a91a75..31b09d6 100644
--- a/img/combined/grub.cfg.in
+++ b/img/combined/grub.cfg.in
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: EUPL-1.2
-# SPDX-FileCopyrightText: 2021 Alyssa Ross <hi@alyssa.is>
+# SPDX-FileCopyrightText: 2021-2022 Alyssa Ross <hi@alyssa.is>
 
 insmod efi_gop
 insmod efi_uga
@@ -13,7 +13,8 @@ terminal_output gfxterm
 
 menuentry "Try Spectrum" {
   loopback live (hd0,gpt3)/Spectrum-0.0-x86_64-generic.0.Live.img
-  chainloader (live,gpt1)/efi/boot/bootx64.efi
+  linux (live,gpt1)/spectrum/linux @spectrumKernelParams@
+  initrd (live,gpt1)/spectrum/initrd
 }
 
 menuentry "Install Spectrum" {
-- 
2.35.1