nova-image: write image to stdout

apps/default.nix

@@ -30,8 +30,8 @@ rec {
     type = "app";
     program = "${drv}/bin/nova-image";
     function = attrs: bootDesc:
-      nixpkgs.runCommand "nova-iso" (attrs // { inherit bootDesc; })
-      "XDG_CACHE_HOME=$TMPDIR ${drv}/bin/nova-image $bootDesc > $out";
+      nixpkgs.runCommand "nova-iso" attrs
+      ''XDG_CACHE_HOME=$TMPDIR ${drv}/bin/nova-image "${bootDesc}" > $out'';
   };
 
   nova-iso = let

apps/nova-image/default.nix

@@ -10,14 +10,6 @@ in nixpkgs.writeScriptBin "nova-image" (with nixpkgs.buildPackages;
     #!${runtimeShell}
     set -eu
 
-    out="$1"
-    shift
-
-    if [ -e "$out" ]; then
-      echo "refusing to overwrite $out as output" > /dev/stderr
-      exit 1
-    fi
-
     CC="${cc}/bin/${cc.targetPrefix}cc"
     LD="${buildPackages.binutils}/bin/${buildPackages.binutils.targetPrefix}ld"
 
@@ -39,6 +31,6 @@ in nixpkgs.writeScriptBin "nova-image" (with nixpkgs.buildPackages;
     	-T${base-nova.src}/repos/base-nova/src/core/core-bss.ld \
     	-z max-page-size=0x1000 \
     	-Ttext=0x100000 -gc-sections \
-    	"''${CORE_NOVA:-${base-nova}/lib/core-nova.o}" "$TMPDIR/boot_modules.o" \
-        -o "$out"
+    	"''${CORE_NOVA:-${base-nova}/lib/core-nova.o}" "$TMPDIR/boot_modules.o"
+    cat a.out
   '')

apps/nova-iso/default.nix

@@ -15,7 +15,7 @@ nixpkgs.writeScriptBin "nova-iso" (with nixpkgs.buildPackages;
     trap "rm -rf $TMPDIR" err exit
 
     mkdir -p "$TMPDIR/boot/syslinux"
-    ${nova-image.program} "$TMPDIR/boot/image.elf" $@
+    ${nova-image.program} $@ > "$TMPDIR/boot/image.elf"
 
     pushd "$TMPDIR" > /dev/null
     out="nova.iso"

tests/driver-nova.nix

@@ -145,7 +145,7 @@ let
       sotest = hostPkgs.runCommand "nova-${name}-sotest" env' ''
         export XDG_CACHE_HOME=''${TMPDIR:-/tmp}
         ${apps.nova-image.program} \
-          image.elf "${./driver-nova-config.dhall} ${testConfig}"
+          "${./driver-nova-config.dhall} ${testConfig}" > image.elf
         cp "${testPkgs.bender}" bender
         cp "${testPkgs.NOVA}/hypervisor-x86_64" hypervisor
         mkdir -p $out/nix-support