seabios: build vgabios for qemu use, with custom resolution

overlay/overlay.nix

@@ -101,6 +101,9 @@ in
       kernel-builder-gcc6 = callPackage ./mobile-nixos/kernel/builder.nix {
         stdenv = with self; overrideCC stdenv buildPackages.gcc6;
       };
+      virtualization = {
+        bios = callPackage ./seabios {};
+      };
     };
 
     imageBuilder = callPackage ../lib/image-builder {};

overlay/seabios/0001-HACK-Adds-mobile-like-VGA-modes.patch

@@ -0,0 +1,41 @@
+From fe256e0ac58e583b06640106f664ad9ae131d6ba Mon Sep 17 00:00:00 2001
+From: Samuel Dionne-Riel <samuel@dionne-riel.com>
+Date: Sat, 5 Oct 2019 01:27:34 -0400
+Subject: [PATCH] HACK: Adds mobile-like VGA modes
+
+---
+ vgasrc/bochsvga.c | 3 +++
+ vgasrc/cbvga.c    | 3 +++
+ 2 files changed, 6 insertions(+)
+
+diff --git a/vgasrc/bochsvga.c b/vgasrc/bochsvga.c
+index ec5d101..62e38fb 100644
+--- a/vgasrc/bochsvga.c
++++ b/vgasrc/bochsvga.c
+@@ -100,6 +100,9 @@ static struct bochsvga_mode
+     { 0x190, { MM_DIRECT, 1920, 1080, 16, 8, 16, SEG_GRAPH } },
+     { 0x191, { MM_DIRECT, 1920, 1080, 24, 8, 16, SEG_GRAPH } },
+     { 0x192, { MM_DIRECT, 1920, 1080, 32, 8, 16, SEG_GRAPH } },
++    // "Mobile" modes
++    { 0x193, { MM_DIRECT,  720, 1280, 32, 8, 16, SEG_GRAPH } },
++    { 0x194, { MM_DIRECT, 1080, 1920, 32, 8, 16, SEG_GRAPH } },
+ };
+ 
+ static int dispi_found VAR16 = 0;
+diff --git a/vgasrc/cbvga.c b/vgasrc/cbvga.c
+index f85989a..8d7395b 100644
+--- a/vgasrc/cbvga.c
++++ b/vgasrc/cbvga.c
+@@ -81,6 +81,9 @@ static struct cbvga_mode_s
+     { 0x190, { MM_DIRECT, 1920, 1080, 16, 8, 16, SEG_GRAPH } },
+     { 0x191, { MM_DIRECT, 1920, 1080, 24, 8, 16, SEG_GRAPH } },
+     { 0x192, { MM_DIRECT, 1920, 1080, 32, 8, 16, SEG_GRAPH } },
++    // "Mobile" modes
++    { 0x193, { MM_DIRECT,  720, 1280, 32, 8, 16, SEG_GRAPH } },
++    { 0x194, { MM_DIRECT, 1080, 1920, 32, 8, 16, SEG_GRAPH } },
+ };
+ 
+ struct vgamode_s *cbvga_find_mode(int mode)
+-- 
+2.23.0
+

overlay/seabios/default.nix

@@ -0,0 +1,33 @@
+{ seabios }:
+
+seabios.overrideAttrs({patches ? [], ...}: {
+  # Config taken from the QEMU source.
+  configurePhase = ''
+    cat > .config <<EOF
+    # for qemu machine types 2.0 + newer
+    CONFIG_QEMU=y
+    CONFIG_ROM_SIZE=256
+    CONFIG_ATA_DMA=n
+    CONFIG_NO_VGABIOS=n
+    CONFIG_VGA_BOCHS=y
+    EOF
+
+    make oldnoconfig
+  '';
+
+  patches = [
+    ./0001-HACK-Adds-mobile-like-VGA-modes.patch
+  ];
+
+  installPhase = ''
+    mkdir -p $out
+    cp ".config" "out/bios.bin" "out/vgabios.bin" $out/
+    (
+    cd $out;
+    ln -sf vgabios.bin vgabios-stdvga.bin
+    )
+  '';
+
+  dontStrip = true;
+  hardeningDisable = [ "all" ];
+})