move everything into own nix files

vm.nix

@@ -1,128 +1,24 @@
 {
-  pkgs,
-  pigeon-toolchain,
-  pigeon-vcpu-count ? 1,
-  pigeon-memory-size ? 512,
-  pigeon-disc-size ? "1G",
-  pigeon-kernel-params ? [
-    "64BIT" "TTY" "SERIAL_8250" "SERIAL_8250_CONSOLE" "PRINTK"
-
-    "HYPERVISOR_GUEST" "PARAVIRT" "KVM_GUEST"
-
-    "BLOCK" "VIRTIO_MENU" "VIRTIO" "VIRTIO_PCI" "VIRTIO_MMIO" "VIRTIO_BLK"
-    "EXT4_FS" "SHMEM" "TMPFS" "PROC_FS" "PROC_SYSCTL" "SYSFS" "DEVTMPFS"
-
-    "ACPI" "PCI" "PCI_MSI" "MAGIC_SYSRQ"
-
-    "BINFMT_ELF" "BINFMT_SCRIPT" "MULTIUSER" "FUTEX" "EPOLL" "EVENTFD"
-    "SIGNALFD" "TIMERFD" "POSIX_TIMERS" "FILE_LOCKING" "ADVISE_SYSCALLS"
-    "NET" "UNIX"
-  ]
+  writeShellApplication,
+  coreutils, firecracker, jq,
+  pigeon-vmconfig
 }:
 
-let
-  kernel = pkgs.stdenv.mkDerivation {
-    inherit (pkgs.linux_6_1) src version;
-    pname = "pigeon-kernel";
+writeShellApplication {
+  name = "pigeon-vm";
+  runtimeInputs = [ coreutils firecracker jq ];
+  text = ''
+    [ "$#" -ne 3 ] && exit 1
 
-    nativeBuildInputs = with pkgs; [ bc bison elfutils flex perl ];
-    hardeningDisable = [ "all" ];
-    enableParallelBuilding = true;
+    CONFIG="$(mktemp)"
+    trap 'rm -rf "$CONFIG"' EXIT
 
-    configurePhase = ''
-      runHook preConfigure
-      patchShebangs scripts tools
-      make tinyconfig
-      for OPTION in ${toString pigeon-kernel-params}; do
-        scripts/config --enable $OPTION
-      done
-      make olddefconfig
-      for OPTION in ${toString pigeon-kernel-config}; do
-        grep -qx "CONFIG_$OPTION=y" .config || exit 1
-      done
-      runHook postConfigure
-    '';
+    jq --arg s "$1" --arg g "$2" --arg r "$3" '
+      (.drives[] | select(.drive_id == "student").path_on_host) = $s |
+      (.drives[] | select(.drive_id == "grader").path_on_host) = $g |
+      (.drives[] | select(.drive_id == "results").path_on_host) = $r
+    ' ${pigeon-vmconfig} >"$CONFIG"
 
-    buildFlags = [ "vmlinux" ];
-
-    installPhase = ''
-      runHook preInstall
-      cp vmlinux "$out"
-      runHook postInstall
-    '';
-  };
-
-  toolchain = pkgs.buildEnv { name = "pigeon-toolchain"; paths = pigeon-toolchain; };
-  closure = pkgs.closureInfo { rootPaths = [ toolchain ]; };
-  rootfs = pkgs.runCommand "pigeon-rootfs" { nativeBuildInputs = [ pkgs.e2fsprogs ]; } ''
-    mkdir -p rootfs && cd rootfs
-    mkdir -p dev proc sys tmp usr nix/store root/student root/grader root/results
-    chmod 700 root
-
-    for FILE in $(cat ${closure}/store-paths); do
-      cp -a "$FILE" nix/store
-    done
-    ln -s ${toolchain}/bin bin
-    ln -s ${toolchain}/bin usr/bin
-    install -m 755 ${./init.sh} init
-    install -m 755 ${./run.sh} run
-
-    cd ..
-    mkfs.ext4 -q -F -d rootfs $out ${pigeon-disc-size}
+    firecracker --no-api --config-file "$CONFIG"
   '';
-  
-  vmconfig = pkgs.writeText "pigeon-vm.json" (builtins.toJSON {
-    boot-source = {
-      kernel_image_path = "${kernel}";
-      boot_args = "reboot=k panic=1 quiet init=/init nomodule 8250.nr_uarts=0 i8042.noaux i8042.nomux i8042.dumbkbd swiotlb=noforce";
-    };
-    drives = [
-      {
-        drive_id = "rootfs";
-        path_on_host = "${rootfs}";
-        is_root_device = true;
-        is_read_only = true;
-      }
-      {
-        drive_id = "student";
-        path_on_host = "";
-        is_root_device = false;
-        is_read_only = true;
-      }
-      {
-        drive_id = "grader";
-        path_on_host = "";
-        is_root_device = false;
-        is_read_only = true;
-      }
-      {
-        drive_id = "results";
-        path_on_host = "";
-        is_root_device = false;
-        is_read_only = false;
-      }
-    ];
-    machine-config = {
-      vcpu_count = pigeon-vcpu-count;
-      mem_size_mib = pigeon-memory-size;
-    };
-  });
-in
-  pkgs.writeShellApplication {
-    name = "pigeon-vm";
-    runtimeInputs = with pkgs; [ coreutils firecracker jq ];
-    text = ''
-      [ "$#" -ne 3 ] && exit 1
-
-      CONFIG="$(mktemp)"
-      trap 'rm -rf "$CONFIG"' EXIT
-
-      jq --arg s "$1" --arg g "$2" --arg r "$3" '
-        (.drives[] | select(.drive_id == "student").path_on_host) = $s |
-        (.drives[] | select(.drive_id == "grader").path_on_host) = $g |
-        (.drives[] | select(.drive_id == "result").path_on_host) = $r
-      ' ${vmconfig} >"$CONFIG"
-
-      firecracker --no-api --config-file "$CONFIG"
-    '';
-  }
+}