Nix: Add a baremetal shell (arm-embedded)

- This commits adds a new shell: arm-embedded for baremetal targets.

- It includes arm-none-eabi-gcc, qemu, and platform support files from
pqmx (currently limited to the MPS3 AN547 Cortex-M55).

Signed-off-by: willieyz <[email protected]>

Author: willieyz

flake.nix

@@ -82,6 +82,15 @@
               } ++ pkgs.lib.optionals (!pkgs.stdenv.isDarwin) [ config.packages.valgrind_varlat ];
           };
 
+          # arm-none-eabi-gcc + platform files from pqmx
+          packages.m55-an547 = util.m55-an547;
+          devShells.arm-embedded = util.mkShell {
+            packages = builtins.attrValues
+              {
+                inherit (config.packages) m55-an547;
+                inherit (pkgs) gcc-arm-embedded qemu coreutils python3 git;
+              };
+          };
           devShells.hol_light = util.mkShell {
             packages = builtins.attrValues {
               inherit (config.packages) linters hol_light s2n_bignum;

nix/m55-an547-arm-none-eabi/default.nix

@@ -0,0 +1,39 @@
+# Copyright (c) The mldsa-native project authors
+# Copyright (c) The mlkem-native project authors
+# SPDX-License-Identifier: Apache-2.0 OR ISC OR MIT
+
+{ stdenvNoCC
+, fetchFromGitHub
+, writeText
+}:
+
+stdenvNoCC.mkDerivation {
+  pname = "mlkem-native-m55-an547";
+  version = "main-2025-10-02";
+
+
+  # Fetch platform files from pqmx (envs/m55-an547)
+  src = fetchFromGitHub {
+    owner = "slothy-optimizer";
+    repo = "pqmx";
+    rev = "4ed493d3cf2af62a08fd9fe36c3472a0dc50ad9f";
+    hash = "sha256-jLIqwknjRwcoDeEAETlMhRqZQ5a3QGCDZX9DENelGeQ=";
+  };
+
+  dontBuild = true;
+
+  installPhase = ''
+    mkdir -p $out/platform/m55-an547/src/platform/
+    cp -r envs/m55-an547/src/platform/. $out/platform/m55-an547/src/platform/
+    cp integration/*.c $out/platform/m55-an547/src/platform/
+  '';
+
+  setupHook = writeText "setup-hook.sh" ''
+    export M55_AN547_PATH="$1/platform/m55-an547/src/platform/"
+  '';
+
+  meta = {
+    description = "Platform files for the Cortex-M55 (AN547)";
+    homepage = "https://github.com/slothy-optimizer/pqmx";
+  };
+}

nix/util.nix

@@ -28,6 +28,7 @@ rec {
       riscv64-gcc = wrap-gcc pkgs.pkgsCross.riscv64;
       riscv32-gcc = wrap-gcc pkgs.pkgsCross.riscv32;
       ppc64le-gcc = wrap-gcc pkgs.pkgsCross.powernv;
+      arm-embedded-gcc = wrap-gcc pkgs.armToolchain;
       aarch64_be-gcc = (pkgs.callPackage ./aarch64_be-none-linux-gnu-gcc.nix { });
     in
     # NOTE:
@@ -100,6 +101,7 @@ rec {
   hol_light' = pkgs.callPackage ./hol_light { };
   s2n_bignum = pkgs.callPackage ./s2n_bignum { };
   slothy = pkgs.callPackage ./slothy { };
+  m55-an547 = pkgs.callPackage ./m55-an547-arm-none-eabi { };
 
   # Helper function to build individual cross toolchains
   _individual_toolchain = { name, cross_compilers }: