Add initramfs PoC with busybox init

1 files changed, 89 insertions, 0 deletions

diff --git a/nix/flake.nix b/nix/flake.nix
index dbc4e2d..cdffdcc 100644
--- a/nix/flake.nix
+++ b/nix/flake.nix
@@ -2,7 +2,96 @@
   outputs = { self, nixpkgs }: let
     system = "x86_64-linux";
     pkgs = import nixpkgs { inherit system; config.allowUnfree = true; };
+
+    crossSystem = "arm-linux";
+    cross = import nixpkgs {
+      inherit system;
+
+      config.allowUnsupportedSystem = true;
+
+      crossSystem = {
+        config = "arm-unknown-linux-gnueabi";
+
+        gcc = {
+          # > Switch "--with-arch" may not be used with switch "--with-cpu"
+          # > make[1]: *** [Makefile:4315: configure-gcc] Error 1
+          #arch = "armv4";
+
+          # Ver SA110 en arch/arm/mm/Kconfig, es parecido 
+          cpu = "arm810";
+        };
+
+        linux-kernel = {
+          name = "taller";
+          target = "uImage";
+          makeFlags = [ "LOADADDR=0x8000" ];
+          autoModules = false;
+          baseConfig = "taller_defconfig";
+        };
+      };
+    };
   in {
+    # Tomado de pkgs/build-support/vm/default.nix
+    packages."${crossSystem}".proof-of-concept = cross.makeInitrd {
+      contents = [
+        {
+          symlink = "/init";
+
+          object = with cross; let
+            initrdUtils = runCommand "initrd-utils"
+              { nativeBuildInputs = [ buildPackages.nukeReferences ];
+                allowedReferences = [ "out" ]; # prevent accidents like glibc being included in the initrd
+              }
+              ''
+                mkdir -p $out/bin
+                mkdir -p $out/lib
+
+                # Copy what we need from Glibc.
+                cp -p ${cross.glibc.out}/lib/ld-linux*.so.? $out/lib
+                cp -p ${cross.glibc.out}/lib/libc.so.* $out/lib
+                cp -p ${cross.glibc.out}/lib/libm.so.* $out/lib
+                cp -p ${cross.glibc.out}/lib/libresolv.so.* $out/lib
+
+                # Copy BusyBox.
+                cp -pd ${cross.busybox}/bin/* $out/bin
+
+                # Run patchelf to make the programs refer to the copied libraries.
+                for i in $out/bin/* $out/lib/*; do if ! test -L $i; then nuke-refs $i; fi; done
+
+                for i in $out/bin/*; do
+                    if [ -f "$i" -a ! -L "$i" ]; then
+                        echo "patching $i..."
+                        patchelf --set-interpreter $out/lib/ld-linux*.so.? --set-rpath $out/lib $i || true
+                    fi
+                done
+              '';
+
+
+            path = lib.makeSearchPath "bin" [
+              #bashInteractive
+              #coreutils-full
+              #gnugrep
+              #neofetch
+              #util-linux
+            ];
+          in writeScript "init" ''
+            #!${initrdUtils}/bin/ash
+
+            export PATH=${initrdUtils}/bin
+
+            mkdir -p /dev /etc /proc /sys
+            echo -n > /etc/fstab
+
+            mount -t devtmpfs devtmpfs /dev
+            mount -t proc none /proc
+            mount -t sysfs none /sys
+
+            exec ash
+          '';
+        }
+      ];
+    };
+
     devShells."${system}" = with pkgs; {
       default = mkShell {
         buildInputs = [