linux_latest: optionally build Linux 6.7 and onwards with rust support

With the current patching situation around enabling Linux to build
with whatever rustc/bindgen version we have in nixpkgs, it feels like
supporting a Rust-by-default build at this time is not fully
justified.

Co-authored-by: Julian Stecklina <julian.stecklina@cyberus-technology.de>

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

@@ -380,6 +380,16 @@ let
       DRM_VC4_HDMI_CEC = yes;
     };
 
+    # Enables Rust support in the Linux kernel. This is currently not enabled by default, because it occasionally requires
+    # patching the Linux kernel for the specific Rust toolchain in nixpkgs. These patches usually take a bit
+    # of time to appear and this would hold up Linux kernel and Rust toolchain updates.
+    #
+    # Once Rust in the kernel has more users, we can reconsider enabling it by default.
+    rust = optionalAttrs ((features.rust or false) && versionAtLeast version "6.7") {
+      RUST = yes;
+      GCC_PLUGINS = no;
+    };
+
     sound = {
       SND_DYNAMIC_MINORS  = yes;
       SND_AC97_POWER_SAVE = yes; # AC97 Power-Saving Mode

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

@@ -9,6 +9,9 @@
 , pahole
 , lib
 , stdenv
+, rustc
+, rustPlatform
+, rust-bindgen
 
 , # The kernel source tarball.
   src
@@ -117,6 +120,8 @@ let
         map ({extraConfig ? "", ...}: extraConfig) kernelPatches;
     in lib.concatStringsSep "\n" ([baseConfigStr] ++ configFromPatches);
 
+  withRust = ((configfile.moduleStructuredConfig.settings.RUST or {}).tristate or null) == "y";
+
   configfile = stdenv.mkDerivation {
     inherit ignoreConfigErrors autoModules preferBuiltin kernelArch extraMakeFlags;
     pname = "linux-config";
@@ -130,7 +135,11 @@ let
     depsBuildBuild = [ buildPackages.stdenv.cc ];
     nativeBuildInputs = [ perl gmp libmpc mpfr ]
       ++ lib.optionals (lib.versionAtLeast version "4.16") [ bison flex ]
-      ++ lib.optional (lib.versionAtLeast version "5.2") pahole;
+      ++ lib.optional (lib.versionAtLeast version "5.2") pahole
+      ++ lib.optionals withRust [ rust-bindgen rustc ]
+    ;
+
+    RUST_LIB_SRC = lib.optionalString withRust rustPlatform.rustLibSrc;
 
     platformName = stdenv.hostPlatform.linux-kernel.name;
     # e.g. "defconfig"
@@ -202,7 +211,7 @@ let
     inherit kernelPatches randstructSeed extraMakeFlags extraMeta configfile;
     pos = builtins.unsafeGetAttrPos "version" args;
 
-    config = { CONFIG_MODULES = "y"; CONFIG_FW_LOADER = "m"; };
+    config = { CONFIG_MODULES = "y"; CONFIG_FW_LOADER = "m"; } // lib.optionalAttrs withRust { CONFIG_RUST = "y"; };
   } // lib.optionalAttrs (modDirVersion != null) { inherit modDirVersion; });
 
   passthru = basicArgs // {

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

@@ -1,6 +1,7 @@
 { lib, stdenv, buildPackages, runCommand, nettools, bc, bison, flex, perl, rsync, gmp, libmpc, mpfr, openssl
 , libelf, cpio, elfutils, zstd, python3Minimal, zlib, pahole, kmod, ubootTools
 , fetchpatch
+, rustc, rust-bindgen, rustPlatform
 }:
 
 let
@@ -56,15 +57,6 @@ let
   inherit (lib)
     hasAttr getAttr optional optionals optionalString optionalAttrs maintainers platforms;
 
-  # Dependencies that are required to build kernel modules
-  moduleBuildDependencies = [
-    pahole
-    perl
-    libelf
-    # module makefiles often run uname commands to find out the kernel version
-    (buildPackages.deterministic-uname.override { inherit modDirVersion; })
-  ] ++ optional (lib.versionAtLeast version "5.13") zstd;
-
   drvAttrs = config_: kernelConf: kernelPatches: configfile:
     let
       config = let attrName = attr: "CONFIG_" + attr; in {
@@ -84,14 +76,27 @@ let
       } // config_;
 
       isModular = config.isYes "MODULES";
+      withRust = config.isYes "RUST";
 
       buildDTBs = kernelConf.DTB or false;
 
+      # Dependencies that are required to build kernel modules
+      moduleBuildDependencies = [
+        pahole
+        perl
+        libelf
+        # module makefiles often run uname commands to find out the kernel version
+        (buildPackages.deterministic-uname.override { inherit modDirVersion; })
+      ]
+      ++ optional (lib.versionAtLeast version "5.13") zstd
+      ++ optionals withRust [ rustc rust-bindgen ]
+      ;
+
     in (optionalAttrs isModular { outputs = [ "out" "dev" ]; }) // {
       passthru = rec {
         inherit version modDirVersion config kernelPatches configfile
           moduleBuildDependencies stdenv;
-        inherit isZen isHardened isLibre;
+        inherit isZen isHardened isLibre withRust;
         isXen = lib.warn "The isXen attribute is deprecated. All Nixpkgs kernels that support it now have Xen enabled." true;
         baseVersion = lib.head (lib.splitString "-rc" version);
         kernelOlder = lib.versionOlder baseVersion;
@@ -100,6 +105,16 @@ let
 
       inherit src;
 
+      depsBuildBuild = [ buildPackages.stdenv.cc ];
+      nativeBuildInputs = [ perl bc nettools openssl rsync gmp libmpc mpfr zstd python3Minimal kmod ubootTools ]
+                          ++ optional  (lib.versionOlder version "5.8") libelf
+                          ++ optionals (lib.versionAtLeast version "4.16") [ bison flex ]
+                          ++ optionals (lib.versionAtLeast version "5.2")  [ cpio pahole zlib ]
+                          ++ optional  (lib.versionAtLeast version "5.8")  elfutils
+                          ++ optionals withRust [ rustc rust-bindgen ];
+
+      RUST_LIB_SRC = lib.optionalString withRust rustPlatform.rustLibSrc;
+
       patches =
         map (p: p.patch) kernelPatches
         # Required for deterministic builds along with some postPatch magic.
@@ -363,14 +378,6 @@ stdenv.mkDerivation ((drvAttrs config stdenv.hostPlatform.linux-kernel kernelPat
 
   enableParallelBuilding = true;
 
-  depsBuildBuild = [ buildPackages.stdenv.cc ];
-  nativeBuildInputs = [ perl bc nettools openssl rsync gmp libmpc mpfr zstd python3Minimal kmod ubootTools ]
-      ++ optional  (lib.versionOlder version "5.8") libelf
-      ++ optionals (lib.versionAtLeast version "4.16") [ bison flex ]
-      ++ optionals (lib.versionAtLeast version "5.2")  [ cpio pahole zlib ]
-      ++ optional  (lib.versionAtLeast version "5.8")  elfutils
-      ;
-
   hardeningDisable = [ "bindnow" "format" "fortify" "stackprotector" "pic" "pie" ];
 
   # Absolute paths for compilers avoid any PATH-clobbering issues.