linux: expose KBUILD_IMAGE as a property of the kernel

lib/systems/inspect.nix

@@ -48,6 +48,7 @@ rec {
     isRiscV64      = { cpu = { family = "riscv"; bits = 64; }; };
     isRx           = { cpu = { family = "rx"; }; };
     isSparc        = { cpu = { family = "sparc"; }; };
+    isSparc64      = { cpu = { family = "sparc"; bits = 64; }; };
     isWasm         = { cpu = { family = "wasm"; }; };
     isMsp430       = { cpu = { family = "msp430"; }; };
     isVc4          = { cpu = { family = "vc4"; }; };

lib/systems/platforms.nix

@@ -14,7 +14,6 @@ rec {
       baseConfig = "defconfig";
       # Build whatever possible as a module, if not stated in the extra config.
       autoModules = true;
-      target = "bzImage";
     };
   };
 
@@ -27,7 +26,6 @@ rec {
       name = "PowerNV";
 
       baseConfig = "powernv_defconfig";
-      target = "vmlinux";
       autoModules = true;
       # avoid driver/FS trouble arising from unusual page size
       extraConfig = ''
@@ -384,7 +382,6 @@ rec {
         # which our initrd builder can't currently do easily.
         USB_XHCI_TEGRA m
       '';
-      target = "Image";
     };
     gcc = {
       arch = "armv8-a";
@@ -534,7 +531,6 @@ rec {
   riscv-multiplatform = {
     linux-kernel = {
       name = "riscv-multiplatform";
-      target = "Image";
       autoModules = true;
       baseConfig = "defconfig";
       DTB = true;

pkgs/os-specific/linux/kernel/common-config.nix

@@ -894,7 +894,8 @@ let
 
       EFI_STUB            = yes; # EFI bootloader in the bzImage itself
       EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER =
-          whenOlder "6.2" (whenAtLeast "5.8" yes); # initrd kernel parameter for EFI
+        whenOlder "6.2" (whenAtLeast "5.8" yes); # initrd kernel parameter for EFI
+      EFI_ZBOOT = whenAtLeast "6.1" yes; # Generic compression support for EFI payloads
       CGROUPS             = yes; # used by systemd
       FHANDLE             = yes; # used by systemd
       SECCOMP             = yes; # used by systemd >= 231

pkgs/os-specific/linux/kernel/generic.nix

@@ -1,3 +1,12 @@
+let
+  # Map of images representations to legacy Makefile targets.
+  defaultMapImageToTargets = {
+    "uImage" = "uinstall";
+    "zImage" = "zinstall";
+    "Image.gz" = "zinstall";
+    "vmlinux" = "install";
+  };
+in
 { buildPackages
 , callPackage
 , perl
@@ -57,6 +66,11 @@
 # easy overrides to stdenv.hostPlatform.linux-kernel members
 , autoModules ? stdenv.hostPlatform.linux-kernel.autoModules or true
 , preferBuiltin ? stdenv.hostPlatform.linux-kernel.preferBuiltin or false
+, kernelTarget ? null
+# FIXME: this should go whenever we can rely on KBUILD_IMAGE to install
+# our kernel targets, MIPS is probably the only recent kernel in-tree
+# which does not support that yet.
+, installTargets ? [ ]
 , kernelArch ? stdenv.hostPlatform.linuxArch
 , kernelTests ? []
 , nixosTests
@@ -92,6 +106,41 @@ let
     ia32Emulation = true;
   } // features) kernelPatches;
 
+
+  # Legacy compatibility layer for
+  # systems relying on `installTarget`
+  # being a property of the platform.
+  defaultKernelInstallTargets = [
+    stdenv.hostPlatform.linux-kernel.installTarget or
+    (defaultMapImageToTargets.${stdenv.hostPlatform.linux-kernel.target or "vmlinux"})
+  ];
+
+  # Default kernel target in the case no install target or kernelTarget is mentioned
+  # We aim to derive the "best" kernel given the current constraints.
+  defaultKernelTarget =
+  if stdenv.hostPlatform.isx86
+    then "bzImage"
+  else if stdenv.hostPlatform.isAarch64
+    then "Image.gz"
+  else if (stdenv.hostPlatform.isAarch || stdenv.hostPlatform.isArmv7)
+    then "vmlinuz"
+  else if stdenv.hostPlatform.isMips
+    then "vmlinux"
+  else if stdenv.hostPlatform.isRiscV
+    then "Image.xz"
+  else if stdenv.hostPlatform.isSparc64
+    then "Image.gz"
+  else if stdenv.hostPlatform.isSparc
+    then "vmlinux"
+  else if stdenv.hostPlatform.isS390
+    then "bzImage"
+  else if stdenv.hostplatform.isLoongArch64
+    then "Image.gz"
+  else "vmlinux";
+
+  finalKernelTarget = if kernelTarget == null then defaultKernelTarget else kernelTarget;
+  finalInstallTargets = if installTargets != [] then defaultKernelInstallTargets else installTargets;
+
   commonStructuredConfig = import ./common-config.nix {
     inherit lib stdenv version;
 
@@ -193,6 +242,9 @@ let
 
   kernel = (callPackage ./manual-config.nix { inherit lib stdenv buildPackages; }) (basicArgs // {
     inherit kernelPatches randstructSeed extraMakeFlags extraMeta configfile;
+    kernelTarget = finalKernelTarget;
+    # kernelTarget has precedence
+    installTargets = if installTargets != [ ] then finalInstallTargets else [ ];
     pos = builtins.unsafeGetAttrPos "version" args;
 
     config = { CONFIG_MODULES = "y"; CONFIG_FW_LOADER = "m"; };
@@ -201,6 +253,10 @@ let
   passthru = basicArgs // {
     features = kernelFeatures;
     inherit commonStructuredConfig structuredExtraConfig extraMakeFlags isZen isHardened isLibre;
+
+    kernelTarget = if kernelTarget == null then defaultKernelTarget else kernelTarget;
+    installTargets = if installTargets != [] then defaultKernelInstallTargets else installTargets;
+
     isXen = lib.warn "The isXen attribute is deprecated. All Nixpkgs kernels that support it now have Xen enabled." true;
 
     # Adds dependencies needed to edit the config:

pkgs/os-specific/linux/kernel/manual-config.nix

@@ -30,6 +30,16 @@ in lib.makeOverridable ({
   src,
   # a list of { name=..., patch=..., extraConfig=...} patches
   kernelPatches ? [],
+  # KBUILD_IMAGE
+  kernelTarget ? null,
+  # a list of install targets, e.g. :
+  # - uinstall for uImage, U-Boot wrapped image
+  # - zinstall for zImage, self-extracting images
+  # - install, the generic binary image
+  # those targets are legacy and are present
+  # only for compatibility with old kernels or MIPS for now.
+  # prefer KBUILD_IMAGE instead.
+  installTargets ? [],
   # The kernel .config file
   configfile,
   # Manually specified nixexpr representing the config
@@ -88,14 +98,16 @@ let
   isModular = config.isYes "MODULES";
 
   kernelConf = stdenv.hostPlatform.linux-kernel;
-  target = kernelConf.target or "vmlinux";
-
   buildDTBs = kernelConf.DTB or false;
 in
 
 assert lib.versionOlder version "5.8" -> libelf != null;
 assert lib.versionAtLeast version "5.8" -> elfutils != null;
 
+# An kernel image target must be explicit as we cannot learn it
+# from the defaults in the different Makefile.
+assert kernelTarget != null || installTargets != [];
+
 stdenv.mkDerivation ({
   pname = "linux";
   inherit version src;
@@ -220,6 +232,7 @@ stdenv.mkDerivation ({
   ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
     "CROSS_COMPILE=${stdenv.cc.targetPrefix}"
   ] ++ (kernelConf.makeFlags or [])
+    ++ lib.optional (kernelTarget != null) "KBUILD_IMAGE=${kernelTarget}"
     ++ extraMakeFlags;
 
   karch = stdenv.hostPlatform.linuxArch;
@@ -296,12 +309,7 @@ stdenv.mkDerivation ({
   '';
 
   # Some image types need special install targets (e.g. uImage is installed with make uinstall)
-  installTargets = [
-    (kernelConf.installTarget or (
-      /**/ if target == "uImage" then "uinstall"
-      else if target == "zImage" || target == "Image.gz" then "zinstall"
-      else "install"))
-  ];
+  installTargets = if installTargets == [ ] then [ "install" ] else installTargets;
 
   postInstall = optionalString isModular ''
     if [ -z "''${dontStrip-}" ]; then
@@ -332,7 +340,8 @@ stdenv.mkDerivation ({
         cp -HR $buildRoot/$f $dev/lib/modules/${modDirVersion}/build/$f
       fi
     done
-    ln -s $dev/lib/modules/${modDirVersion}/build/vmlinux $dev
+    mkdir $debug/
+    ln -s $dev/lib/modules/${modDirVersion}/build/vmlinux $debug
 
     # !!! No documentation on how much of the source tree must be kept
     # If/when kernel builds fail due to missing files, you can add
@@ -424,5 +433,5 @@ stdenv.mkDerivation ({
 } // optionalAttrs (pos != null) {
   inherit pos;
 } // optionalAttrs isModular {
-  outputs = [ "out" "dev" ];
+  outputs = [ "out" "dev" "debug" ];
 }))