config/default.nix

@@ -1,6 +1,8 @@
 {
   config,
   pkgs,
+  lib,
+  system,
   ...
 }: {
   imports = [

config/installer.nix

@@ -14,4 +14,9 @@
   boot.kernelPackages = lib.mkForce pkgs.linuxPackages_testing_bcachefs;
   networking.hostId = "8425e349";
   nix.settings.post-build-hook = lib.mkForce "true";
+  nixpkgs.localSystem = {
+    system = "x86_64-linux";
+    gcc.arch = "skylake";
+    gcc.tune = "skylake";
+  };
 }

config/instance-20221213-1915.nix

@@ -145,4 +145,9 @@
   };
 
   services.restic.backups.sysbackup.paths = ["/persist"];
+  nixpkgs.localSystem = {
+    system = "aarch64-linux";
+    gcc.arch = "armv8.2-a";
+    gcc.tune = "neoverse-n1";
+  };
 }

config/nas.nix

@@ -170,4 +170,10 @@
     "/ip4/0.0.0.0/tcp/5001"
     "/ip6/::/tcp/5001"
   ]; # Only exposed over the tailed scale
+
+  nixpkgs.localSystem = {
+    system = "x86_64-linux";
+    gcc.arch = "znver1";
+    gcc.tune = "znver1";
+  };
 }

config/netboot.nix

@@ -14,4 +14,9 @@
   boot.kernelPackages = lib.mkForce pkgs.linuxPackages_testing_bcachefs;
   networking.hostId = "8425e349";
   nix.settings.post-build-hook = lib.mkForce "true";
+  nixpkgs.localSystem = {
+    system = "x86_64-linux";
+    gcc.arch = "skylake";
+    gcc.tune = "skylake";
+  };
 }

config/nixos-8gb-fsn1-1.nix

@@ -206,4 +206,9 @@
   services.resolved.enable = false;
   services.bind.forwarders = lib.mkForce [];
   services.tailscale.useRoutingFeatures = "server";
+  nixpkgs.localSystem = {
+    system = "x86_64-linux";
+    gcc.arch = "skylake";
+    gcc.tune = "skylake";
+  };
 }

config/nutty-noon.nix

@@ -121,4 +121,9 @@
   ];
   services.tailscale.useRoutingFeatures = "client";
   home-manager.users.darkkirb._module.args.withNSFW = lib.mkForce true;
+  nixpkgs.localSystem = {
+    system = "x86_64-linux";
+    gcc.arch = "znver2";
+    gcc.tune = "znver2";
+  };
 }

config/specialization.nix

@@ -1,19 +1,12 @@
 # Configuration file configuring specialization
-{
-  pkgs,
-  config,
-  lib,
-  ...
-}: {
-  nixpkgs.overlays = [
-    (self: prev: {
-      custom_xanmod = pkgs.linuxPackagesFor (pkgs.linuxKernel.kernels.linux_xanmod.override {
-        ignoreConfigErrors = true;
-        autoModules = true;
-        kernelPreferBuiltin = true;
-        enableParallelBuilding = true;
-        extraConfig = import (../extra/linux/config- + "${config.networking.hostName}.nix");
-      });
-    })
-  ];
+{config, ...}: {
+  environment.etc."nix/local-system.json".text = builtins.toJSON {
+    inherit (config.nixpkgs.localSystem) system gcc rustc linux-kernel;
+  };
+
+  # Instead of overriding stdenv, we provide a user hook that appends the correct configure flags
+  nixpkgs.config.stdenv.userHook = ''
+    NIX_CFLAGS_COMPILE+="-O3 -pipe -flto"
+    unset doCheck doInstallCheck
+  '';
 }

config/thinkrac.nix

@@ -180,4 +180,9 @@
   hardware.bluetooth.enable = true;
   services.blueman.enable = true;
   services.tailscale.useRoutingFeatures = "client";
+  nixpkgs.localSystem = {
+    system = "x86_64-linux";
+    gcc.arch = "skylake";
+    gcc.tune = "skylake";
+  };
 }

extra/nixpkgs.patch

@@ -0,0 +1,136 @@
+diff --git a/lib/systems/architectures.nix b/lib/systems/architectures.nix
+index 94127fa9..5253e4bb 100644
+--- a/lib/systems/architectures.nix
++++ b/lib/systems/architectures.nix
+@@ -32,9 +32,24 @@ rec {
+     armv5te        = [ ];
+     armv6          = [ ];
+     armv7-a        = [ ];
+-    armv8-a        = [ ];
++    armv8-a        = [ "fp" "simd" ];
++    "armv8.1-a"    = [ "crc" "lse" "rdma" ] ++ features.armv8-a;
++    "armv8.2-a"    = features."armv8.1-a";
++    "armv8.3-a"    = [ "pauth" ] ++ features."armv8.2-a";
++    "armv8.4-a"    = [ "flagm" "fp16fml" "dotprod" ] ++ features."armv8.3-a";
++    "armv8.5-a"    = [ "sb" "sbss" "predres" ] ++ features."armv8.4-a";
++    "armv8.6-a"    = [ "bf16" "i8mm" ] ++ features."armv8.5-a";
++    "armv8.7-a"    = [ "ls64" ] ++ features."armv8.6-a";
++    "armv8.8-a"    = [ "mops" ] ++ features."armv8.7-a";
++    "armv9-a"      = [ "sve" "sve2" ] ++ features."armv8.5-a";
++    "armv9.1-a"    = [ "bf16" "i8mm" ] ++ features."armv9-a";
++    "armv9.2-a"    = [ "ls64" ] ++ features."armv9.1-a";
++    "armv9.3-a"    = [ "mops" ] ++ features."armv9.2-a";
+     mips32         = [ ];
+     loongson2f     = [ ];
++    riscv64-g      = [ "multiply" "atomic" "float" "double" "csr" "ifencei" ];
++    riscv64-gc     = [ "compressed" ] ++ features.riscv64-g;
++    riscv64-gcv    = [ "vector" ] ++ features.riscv64-gc;
+   };
+
+   # a superior CPU has all the features of an inferior and is able to build and test code for it
+@@ -85,8 +100,23 @@ rec {
+     armv6          = [ ];
+     armv7-a        = [ ];
+     armv8-a        = [ ];
++    "armv8.1-a"    = [ "armv8-a" ] ++ inferiors.armv8-a;
++    "armv8.2-a"    = [ "armv8.1-a" ] ++ inferiors."armv8.1-a";
++    "armv8.3-a"    = [ "armv8.2-a" ] ++ inferiors."armv8.2-a";
++    "armv8.4-a"    = [ "armv8.3-a" ] ++ inferiors."armv8.3-a";
++    "armv8.5-a"    = [ "armv8.4-a" ] ++ inferiors."armv8.4-a";
++    "armv8.6-a"    = [ "armv8.5-a" ] ++ inferiors."armv8.5-a";
++    "armv8.7-a"    = [ "armv8.6-a" ] ++ inferiors."armv8.6-a";
++    "armv8.8-a"    = [ "armv8.7-a" ] ++ inferiors."armv8.7-a";
++    "armv9-a"      = [ "armv8.5-a" ] ++ inferiors."armv8.5-a";
++    "armv9.1-a"    = [ "armv9-a" "armv8.6-a" ] ++ inferiors."armv9-a" ++ inferiors."armv8.6-a";
++    "armv9.2-a"    = [ "armv9.1-a" "armv8.7-a" ] ++ inferiors."armv9.1-a" ++ inferiors."armv8.7-a";
++    "armv9.3-a"    = [ "armv9.2-a" "armv8.8-a" ] ++ inferiors."armv9.2-a" ++ inferiors."armv8.8-a";
+     mips32         = [ ];
+     loongson2f     = [ ];
++    riscv64-g      = [ ];
++    riscv64-gc     = [ "riscv64-g" ] ++ inferiors.riscv64-g;
++    riscv64-gcv    = [ "riscv64-gc" ] ++ inferiors.riscv64-gc;
+   };
+
+   predicates = let
+diff --git a/pkgs/build-support/cc-wrapper/default.nix b/pkgs/build-support/cc-wrapper/default.nix
+index e0ee3dae41f..49dbbe56594 100644
+--- a/pkgs/build-support/cc-wrapper/default.nix
++++ b/pkgs/build-support/cc-wrapper/default.nix
+@@ -122,6 +122,10 @@ let
+         znver1         = versionAtLeast ccVersion "6.0";
+         znver2         = versionAtLeast ccVersion "9.0";
+         znver3         = versionAtLeast ccVersion "11.0";
++        # ARM
++        # TODO: Fill in as needed
++        # RISCV
++        # TODO: Fill in as needed
+       }.${arch} or true
+     else if isClang then
+       { # Intel
+@@ -132,6 +136,10 @@ let
+         # AMD
+         znver1         = versionAtLeast ccVersion "4.0";
+         znver2         = versionAtLeast ccVersion "9.0";
++        # AMD
++        # TODO: Fill in as needed
++        # RISCV
++        # TODO: Fill in as needed
+       }.${arch} or true
+     else
+       false;
+diff --git a/pkgs/stdenv/cross/default.nix b/pkgs/stdenv/cross/default.nix
+index bf410ec0..10b240b7 100644
+--- a/pkgs/stdenv/cross/default.nix
++++ b/pkgs/stdenv/cross/default.nix
+@@ -26,9 +26,9 @@ in lib.init bootStages ++ [
+     inherit config overlays;
+     selfBuild = false;
+     stdenv =
+-      assert vanillaPackages.stdenv.buildPlatform == localSystem;
+-      assert vanillaPackages.stdenv.hostPlatform == localSystem;
+-      assert vanillaPackages.stdenv.targetPlatform == localSystem;
++      assert vanillaPackages.stdenv.buildPlatform.system == localSystem.system;
++      assert vanillaPackages.stdenv.hostPlatform.system == localSystem.system;
++      assert vanillaPackages.stdenv.targetPlatform.system == localSystem.system;
+       vanillaPackages.stdenv.override { targetPlatform = crossSystem; };
+     # It's OK to change the built-time dependencies
+     allowCustomOverrides = true;
+diff --git a/pkgs/top-level/impure.nix b/pkgs/top-level/impure.nix
+index 4d847e280f4..874b776c1e1 100644
+--- a/pkgs/top-level/impure.nix
++++ b/pkgs/top-level/impure.nix
+@@ -9,12 +9,15 @@ let
+   # Return ‘x’ if it evaluates, or ‘def’ if it throws an exception.
+   try = x: def: let res = builtins.tryEval x; in if res.success then res.value else def;
+
++  configuredLocalSystem = if builtins.pathExists "/etc/nix/local-system.json" then builtins.fromJSON (builtins.readFile "/etc/nix/local-system.json") else { system = builtins.currentSystem; };
++  localSystemOverriden = args: args ? system && (args.system != configuredLocalSystem);
++  defaultLocalSystem = args: if localSystemOverriden args then { system = args.system; } else configuredLocalSystem;
+ in
+
+ { # We put legacy `system` into `localSystem`, if `localSystem` was not passed.
+   # If neither is passed, assume we are building packages on the current
+   # (build, in GNU Autotools parlance) platform.
+-  localSystem ? { system = args.system or builtins.currentSystem; }
++  localSystem ? null
+
+ # These are needed only because nix's `--arg` command-line logic doesn't work
+ # with unnamed parameters allowed by ...
+@@ -78,6 +81,9 @@ in
+
+ , ...
+ } @ args:
++let
++  localSystem' = if localSystem == null then defaultLocalSystem args else localSystem;
++in
+
+ # If `localSystem` was explicitly passed, legacy `system` should
+ # not be passed, and vice-versa.
+@@ -85,5 +91,6 @@ assert args ? localSystem -> !(args ? system);
+ assert args ? system -> !(args ? localSystem);
+
+ import ./. (builtins.removeAttrs args [ "system" ] // {
+-  inherit config overlays localSystem;
++  inherit config overlays;
++  localSystem = localSystem';
+ })

flake.nix

@@ -107,6 +107,22 @@ rec {
     nur,
     ...
   } @ args: let
+    nixpkgsFor = system:
+      import ./utils/patched-nixpkgs.nix {
+        inherit nixpkgs system;
+        patches = [./extra/nixpkgs.patch];
+      };
+    pkgsFor = system:
+      import (nixpkgsFor system) {
+        localSystem.system = system;
+        overlays = [
+          self.overlays.${system}
+          nur.overlay
+          args.prismmc.overlay
+        ];
+        config.allowUnfree = true;
+        config.contentAddressedByDefault = true;
+      };
     systems = [
       {
         name = "nixos-8gb-fsn1-1"; # Hetzner Server
@@ -143,16 +159,21 @@ rec {
         name,
         system,
         configName ? name,
-      }: {
+      }: let
+        nixpkgs' = nixpkgsFor system;
+        pkgs = pkgsFor system;
+        nixosSystem = import "${nixpkgs'}/nixos/lib/eval-config.nix";
+      in {
         inherit name;
         value =
-          nixpkgs.lib.nixosSystem
+          nixosSystem
           {
             inherit system;
             specialArgs =
               args
               // {
                 inherit system;
+                nixpkgs = nixpkgs';
               };
             modules = [
               (./config + "/${configName}.nix")
@@ -163,9 +184,13 @@ rec {
                 nixpkgs.overlays = [
                   nur.overlay
                 ];
-                home-manager.extraSpecialArgs = args // {inherit system;};
+                home-manager.extraSpecialArgs = args // {inherit system; nixpkgs = nixpkgs';};
               })
-              (import utils/link-input.nix args)
+              (import utils/link-input.nix (args // {nixpkgs = nixpkgs';}))
+              {
+                system.nixos.versionSuffix = ".${pkgs.lib.substring 0 8 (self.lastModifiedDate or self.lastModified or "19700101")}.${self.shortRev or "dirty"}";
+                system.nixos.revision = pkgs.lib.mkIf (nixpkgs ? rev) nixpkgs.rev;
+              }
             ];
           };
       })
@@ -175,10 +200,7 @@ rec {
       aarch64-linux = import ./overlays args "aarch64-linux";
     };
     devShell.x86_64-linux = let
-      pkgs = import nixpkgs {
-        system = "x86_64-linux";
-        overlays = [self.overlays.x86_64-linux];
-      };
+      pkgs = pkgsFor "x86_64-linux";
     in
       pkgs.mkShell {
         nativeBuildInputs = with pkgs; [
@@ -197,10 +219,11 @@ rec {
       };
     formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.alejandra;
     packages.x86_64-linux = let
-      pkgs = import nixpkgs {
+      pkgs = import (nixpkgsFor "x86_64-linux") {
         system = "x86_64-linux";
         overlays = [self.overlays.x86_64-linux];
         config.allowUnfree = true;
+        config.contentAddressedByDefault = true;
       };
     in {
       neovim-base = args.nix-neovim.buildNeovim {
@@ -213,10 +236,11 @@ rec {
       };
     };
     packages.aarch64-linux = let
-      pkgs = import nixpkgs {
+      pkgs = import (nixpkgsFor "aarch64-linux") {
         system = "aarch64-linux";
         overlays = [self.overlays.aarch64-linux];
         config.allowUnfree = true;
+        config.contentAddressedByDefault = true;
       };
     in {
       neovim-base = args.nix-neovim.buildNeovim {

utils/link-input.nix

@@ -1,7 +1,20 @@
-inputs: {lib, ...}: let
+inputs': {
+  system,
+  lib,
+  ...
+}: let
   # Taken from https://github.com/gytis-ivaskevicius/flake-utils-plus/blob/master/lib/options.nix
   inherit (lib) filterAttrs mapAttrs';
-  flakes = filterAttrs (name: value: (name != "self") && (value ? outputs)) inputs;
+  inputs =
+    inputs'
+    // {
+      nixpkgs = import ./patched-nixpkgs.nix {
+        inherit (inputs') nixpkgs;
+        inherit system;
+        patches = "${inputs'.self}/extra/nixpkgs.patch";
+      };
+    };
+  flakes = filterAttrs (name: value: value ? outputs) inputs;
   nixRegistry =
     builtins.mapAttrs
     (name: v: {flake = v;})
@@ -9,11 +22,16 @@ inputs: {lib, ...}: let
 in {
   nix.registry = nixRegistry;
   environment.etc =
-    mapAttrs'
-    (name: value: {
-      name = "nix/inputs/${name}";
-      value = {source = value.outPath;};
-    })
-    inputs;
+    (
+      mapAttrs'
+      (name: value: {
+        name = "nix/inputs/${name}";
+        value = {source = value.outPath;};
+      })
+      inputs
+    )
+    // {
+      "nix/inputs/nixpkgs-overlays".source = lib.mkForce ./nixpkgs-overlays;
+    };
   nix.nixPath = ["/etc/nix/inputs"];
 }

utils/nixpkgs-overlays/overlay.nix

@@ -0,0 +1 @@
+(import <self>).overlays.${builtins.currentSystem}

utils/patched-nixpkgs.nix

@@ -0,0 +1,15 @@
+{
+  nixpkgs,
+  patches,
+  system,
+}: let
+  pkgs = import nixpkgs {
+    inherit system;
+  };
+  nixpkgs-new = pkgs.applyPatches {
+    name = "nixpkgs-patched";
+    src = nixpkgs;
+    inherit patches;
+  };
+in
+  nixpkgs-new