Keep Makefile patch for a few kmods that want gcc

README.md

@@ -365,6 +365,16 @@ Additional arguments are passed through to `buildLinux` from nixpkgs. See [nixpk
     # Additional args are available. See kernel-cachyos/mkCachyKernel.nix
   };
 
+  # For non-LTO kernels
   kernelPackages = pkgs.linuxKernel.packagesFor kernel;
+
+
+  # For LTO kernels, helpers.kernelModuleLLVMOverride fixes compilation for some
+  # out-of-tree modules in nixpkgs.
+  kernelPackagesWithLTOFix = let
+    # helpers.nix provides a few utilities for building kernel with LTO.
+    # I haven't figured out a clean way to expose it in flakes.
+    helpers = pkgs.callPackage "${inputs.nix-cachyos-kernel.outPath}/helpers.nix" {};
+  in helpers.kernelModuleLLVMOverride (pkgs.linuxKernel.packagesFor kernel);
 }
 ```

helpers.nix

@@ -55,4 +55,28 @@ rec {
         pkgs.patchelf
       ];
     });
+
+  kernelModuleLLVMOverride =
+    kernelPackages_:
+    kernelPackages_.extend (
+      _final: prev:
+      lib.mapAttrs (
+        n: v:
+        if
+          builtins.elem "LLVM=1" kernelPackages_.kernel.commonMakeFlags
+          && !(builtins.elem n [ "kernel" ])
+          && lib.isDerivation v
+          && ((v.overrideAttrs or null) != null)
+        then
+          v.overrideAttrs (old: {
+            postPatch = (if (old.postPatch or null) == null then "" else old.postPatch) + ''
+              if [ -f Makefile ]; then
+                substituteInPlace Makefile --replace "gcc" "cc"
+              fi
+            '';
+          })
+        else
+          v
+      ) prev
+    );
 }

kernel-cachyos/packages.nix

@@ -6,12 +6,16 @@
   ...
 }:
 let
+  helpers = callPackage ../helpers.nix { };
+  inherit (helpers) kernelModuleLLVMOverride;
+
   kernels = lib.filterAttrs (_: lib.isDerivation) (callPackage ./. { inherit inputs; });
 in
 lib.mapAttrs' (
   n: v:
   let
-    packages = (linuxKernel.packagesFor v).extend (
+    packages = kernelModuleLLVMOverride (
+      (linuxKernel.packagesFor v).extend (
         final: prev:
         let
           variant = lib.removePrefix "linux-cachyos-" v.cachyosConfigVariant;
@@ -21,6 +25,7 @@ lib.mapAttrs' (
             inherit inputs variant;
           };
         }
+      )
     );
   in
   lib.nameValuePair "linuxPackages-${lib.removePrefix "linux-" n}" packages