nixos/modules/installer/sd-card/sd-image-mips64el.nix: init

This cross-compiles a complete NixOS installer image. The image is built specifically for Cavium Octeon chips, because currently these are the Mips64 products that are commercially available: you can order a Ubiquiti Edgerouter from Amazon and have it the next day. All of Debian's non-Longsoon MIPS builders are Octeons: https://wiki.debian.org/MIPSPort Co-authored-by: Samuel Dionne-Riel <[email protected]>
NixOS · Aug 2, 2023 · ed45b4a · ed45b4a
1 parent 3c24c7b
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diff --git a/lib/systems/examples.nix b/lib/systems/examples.nix
@@ -106,6 +106,8 @@ rec {
   mips64-linux-gnuabi64    = { config = "mips64-unknown-linux-gnuabi64";    } // platforms.gcc_mips64r2_64;
   mips64el-linux-gnuabi64  = { config = "mips64el-unknown-linux-gnuabi64";  } // platforms.gcc_mips64r2_64;
 
+  octeon = { config = "mips64el-unknown-linux-gnuabi64"; } // platforms.gcc_mips64r2_64 // platforms.octeon;
+
   muslpi = raspberryPi // {
     config = "armv6l-unknown-linux-musleabihf";
   };

diff --git a/lib/systems/platforms.nix b/lib/systems/platforms.nix
@@ -526,6 +526,46 @@ rec {
     };
   };
 
+  # Cavium Octeon series chips, which represent nearly all mips64
+  # chips in production as of 2023
+  octeon = {
+
+    # Note: qemu will segfault if you try to run a binary that uses
+    # the -march=octeon instructions.  Much of nixpkgs'
+    # cross-compilation requires qemu.
+
+    # gcc = { arch = "octeon"; };
+
+    linux-kernel = {
+      name = "mips64el";
+      baseConfig = "cavium_octeon_defconfig";
+      target = "vmlinux";
+      DTB = true;
+      autoModules = true;
+      extraConfig =
+        lib.concatStringsSep "\n"
+          (lib.mapAttrsToList (k: v: "${k} ${v}") {
+            CPU_CAVIUM_OCTEON = "y";
+            CPU_LITTLE_ENDIAN = "y";
+            KBUILD_SYM32 = "n";
+            MODULES = "y";
+
+            # MIPS kernels are ELF images, with ELF structure, so you
+            # can stick things into them (and patchelf them!).  We can
+            # also attach the desired DTB directly to the kernel image,
+            # and even use the DTB as a "grub.conf".
+            MIPS_ELF_APPENDED_DTB = "y";
+
+            # Take boot command line from the DTB, but allow the
+            # bootloader to supersede those choices.
+            MIPS_CMDLINE_DTB_EXTEND = "y";
+
+            # > ERROR: modpost: "__tracepoint_ata_bmdma_stop" [drivers/ata/pata_octeon_cf.ko] undefined!
+            PATA_OCTEON_CF = "n";
+          });
+    };
+  };
+
   ##
   ## Other
   ##

diff --git a/nixos/modules/installer/sd-card/sd-image-mips64el.nix b/nixos/modules/installer/sd-card/sd-image-mips64el.nix
@@ -0,0 +1,42 @@
+/*
+To build, use:
+nix-build nixos -I nixos-config=nixos/modules/installer/sd-card/sd-image-mips64el.nix -A config.system.build.sdImage
+
+Since mips hardware is found mostly in routers which are optimized
+for I/O throughput rather than compilation speed, you probably
+want to cross-compile this.  To do so, use:
+
+nix-build nixos \
+  -A config.system.build.sdImage \
+  --arg configuration '{config,lib,pkgs,...}@args: (import ./nixos/modules/installer/sd-card/sd-image-mips64el.nix args) // { nixpkgs.hostPlatform = lib.systems.examples.octeon; nixpkgs.buildPlatform = builtins.currentSystem; }'
+*/
+{ config, lib, pkgs, ... }:
+
+{
+  imports = [
+    ../../profiles/base.nix
+    ./sd-image.nix
+  ];
+
+  boot.loader = {
+    grub.enable = false;
+    generic-extlinux-compatible = {
+      enable = true;
+    };
+  };
+
+  services.xserver.enable = lib.mkForce false;
+  services.xserver.libinput.enable = lib.mkForce false;
+
+  boot.consoleLogLevel = lib.mkDefault 7;
+  boot.kernelParams = [ "console=ttyS0,115200" ];
+  boot.initrd.includeDefaultModules = false;
+
+  sdImage = {
+    populateFirmwareCommands = "";
+    populateRootCommands = ''
+      mkdir -p ./files/boot
+      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
+    '';
+  };
+}