linux: add flavor metadata

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

@@ -45,6 +45,11 @@
                        stdenv.hostPlatform != stdenv.buildPlatform
 , extraMeta ? {}
 
+, isXen      ? features.xen_dom0 or false
+, isZen      ? false
+, isLibre    ? false
+, isHardened ? false
+
 # easy overrides to stdenv.hostPlatform.platform members
 , autoModules ? stdenv.hostPlatform.platform.kernelAutoModules
 , preferBuiltin ? stdenv.hostPlatform.platform.kernelPreferBuiltin or false
@@ -175,7 +180,9 @@ let
 
   passthru = {
     features = kernelFeatures;
-    inherit commonStructuredConfig;
+    inherit commonStructuredConfig isXen isZen isHardened isLibre;
+    kernelOlder = lib.versionOlder version;
+    kernelAtLeast = lib.versionAtLeast version;
     passthru = kernel.passthru // (removeAttrs passthru [ "passthru" ]);
   };
 

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

@@ -17,6 +17,7 @@ let
 in linux.override {
   argsOverride = {
     modDirVersion = "${linux.modDirVersion}-gnu";
+    isLibre = true;
 
     src = stdenv.mkDerivation {
       name = "${linux.name}-libre-src";

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

@@ -7,6 +7,7 @@ in
 buildLinux (args // {
   modDirVersion = "${version}-zen1";
   inherit version;
+  isZen = true;
 
   src = fetchFromGitHub {
     owner = "zen-kernel";

pkgs/top-level/all-packages.nix

@@ -18014,6 +18014,10 @@ in
     inherit kernel;
     inherit (kernel) stdenv; # in particular, use the same compiler by default
 
+    # to help determine module compatibility
+    inherit (kernel) isXen isZen isHardened isLibre;
+    inherit (kernel) kernelOlder kernelAtLeast;
+
     # Obsolete aliases (these packages do not depend on the kernel).
     inherit (pkgs) odp-dpdk pktgen; # added 2018-05
 
@@ -18277,6 +18281,7 @@ in
         kernelPatches.hardened.${kernel.meta.branch}
       ];
       modDirVersionArg = kernel.modDirVersion + "-hardened";
+      isHardened = true;
   });
 
   linuxPackages_hardened = recurseIntoAttrs (hardenedLinuxPackagesFor pkgs.linux { });