boots to userland and runs busybox init

README.md

@@ -8,12 +8,34 @@ Līminis + Nix
 
 ## What is this?
 
-This is a reboot/restart of NixWRT: a Nix-based collection of software
+This is a Nix-based collection of software tailored for domestic wifi
-tailored for domestic wifi router or IoT device devices, of the kind
+router or IoT device devices, of the kind that OpenWrt or DD-WRT or
-that OpenWrt or DD-WRT or Gargoyle or Tomato run on.
+Gargoyle or Tomato run on. It's a reboot/restart/rewrite of NixWRT.
 
 This is not NixOS-on-your-router: it's aimed at devices that are
-underpowered for the full NixOS experience.
+underpowered for the full NixOS experience. It uses busybox tools,
+musl instead of GNU libc, and s6-rc instead of systemd.
+
+
+## Building
+
+These instructions assume you have nixpkgs checked out in a peer
+directory of this one.
+
+You need a `configuration.nix` file pointed to by `<liminix-config>`, a
+hardware device definition as argument `device`, and to choose an
+appropriate output attribute depending on what your device is and how
+you plan to install onto it. For example:
+
+    NIX_PATH=nixpkgs=../nixpkgs:$NIX_PATH NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build -I liminix-config=./tests/smoke/configuration.nix --arg device "import ./devices/qemu.nix" -A outputs.default
+
+`outputs.default` is intended to do something appropriate for the
+device, whatever that is. For the qemu device, it creates a directory
+containing a squashfs root image and a kernel, with which you could
+then run
+
+    ./run-qemu.sh result/vmlinux result/squashfs
+
 
 ## Running tests
 
@@ -22,7 +44,6 @@ Assuming you have nixpkgs checked out in a peer directory of this one,
     NIX_PATH=nixpkgs=../nixpkgs:$NIX_PATH ./run-tests.sh
 
 
-
 ## Articles of interest
 
 * [Build Safety of Software in 28 Popular Home Routers](https://cyber-itl.org/assets/papers/2018/build_safety_of_software_in_28_popular_home_routers.pdf):

default.nix

@@ -25,5 +25,11 @@ let
 in {
   outputs = {
     inherit squashfs kernel;
+    default = nixpkgs.pkgs.runCommand "both-kinds" {} ''
+      mkdir $out
+      cd $out
+      ln -s ${squashfs} squashfs
+      ln -s ${kernel.vmlinux} vmlinux
+   '';
   };
 }

devices/qemu.nix

@@ -9,6 +9,9 @@
     };
   };
   kernel = {
+    checkedConfig = {
+      "BINFMT_SCRIPT" = "y";
+    };
     config = {
       SYSVIPC= "y";
       NO_HZ= "y";
@@ -343,17 +346,9 @@
       UIO_CIF= "m";
       EXT2_FS= "y";
       EXT3_FS= "y";
-      REISERFS_FS= "m";
-      REISERFS_PROC_INFO= "y";
-      REISERFS_FS_XATTR= "y";
-      REISERFS_FS_POSIX_ACL= "y";
-      REISERFS_FS_SECURITY= "y";
       JFS_FS= "m";
       JFS_POSIX_ACL= "y";
       JFS_SECURITY= "y";
-      XFS_FS= "m";
-      XFS_QUOTA= "y";
-      XFS_POSIX_ACL= "y";
       QUOTA= "y";
       QFMT_V2= "y";
       FUSE_FS= "m";
@@ -366,9 +361,6 @@
       PROC_KCORE= "y";
       TMPFS= "y";
       CONFIGFS_FS= "y";
-      AFFS_FS= "m";
-      HFS_FS= "m";
-      HFSPLUS_FS= "m";
       BEFS_FS= "m";
       BFS_FS= "m";
       EFS_FS= "m";
@@ -382,10 +374,10 @@
       ROMFS_FS= "m";
       SYSV_FS= "m";
       UFS_FS= "m";
-      NFS_FS= "y";
+      # NFS_FS= "y";
-      ROOT_NFS= "y";
+      # ROOT_NFS= "y";
-      NFSD= "y";
+      # NFSD= "y";
-      NFSD_V3= "y";
+      # NFSD_V3= "y";
       NLS_CODEPAGE_437= "m";
       NLS_CODEPAGE_737= "m";
       NLS_CODEPAGE_775= "m";
@@ -444,6 +436,13 @@
       CRYPTO_TWOFISH= "m";
       RCU_CPU_STALL_TIMEOUT = "60";
       ENABLE_DEFAULT_TRACERS = "y";
+
+
+      SQUASHFS = "y";
+      SQUASHFS_XZ = "y";
+      VIRTIO_PCI = "y";
+      VIRTIO_BLK = "y";
+      VIRTIO_NET = "y";
     };
   };
 }

make-image.nix

@@ -1,6 +1,14 @@
 pkgs: config:
 let
-  inherit (pkgs) callPackage stdenvNoCC closureInfo stdenv writeText s6-rc;
+  inherit (pkgs)
+    callPackage
+    closureInfo
+    runCommand
+    s6-rc
+    stdenv
+    stdenvNoCC
+    writeScript
+    writeText;
 
   # we need to generate s6 db,  by generating closure of all
   # config.services and calling s6-rc-compile on them
@@ -28,8 +36,46 @@ let
     s6-rc-compile $out/compiled $srcs
     '';
   };
-  makeSquashfs = callPackage <nixpkgs/nixos/lib/make-squashfs.nix> {
+  rcS = writeScript "rcS" ''
-    storeContents = [ s6db ] ++ config.packages ;
+    #!${pkgs.pkgsStatic.busybox}/bin/sh
+    echo WHEEEE
+    PATH=${pkgs.pkgsStatic.busybox}/bin:$PATH
+    export PATH
+    mount -t devtmpfs none /dev/
+    mount -t devpts none /dev/pts
+    mount -t proc none /proc
+    mkdir -p /run/services
+  '';
+  storefs = callPackage <nixpkgs/nixos/lib/make-squashfs.nix> {
+    storeContents = [ rcS pkgs.pkgsStatic.busybox s6db pkgs.s6-linux-init ] ++ config.packages ;
     # comp =  "xz -Xdict-size 100%"
   };
-in  makeSquashfs
+  pseudofiles = writeText "pseudofiles" ''
+     / d 0755 0 0
+     /bin d 0755 0 0
+     /etc d 0755 0 0
+     /run d 0755 0 0
+     /dev d 0755 0 0
+     /dev/console c 0600 root root 5 1
+     /dev/null c 0666 root root 1 3
+     /dev/tty c 0777 root root 5 0
+     /dev/tty1 c 0777 root root 4 1
+     /dev/tty2 c 0777 root root 4 2
+     /dev/tty3 c 0777 root root 4 3
+     /dev/tty4 c 0777 root root 4 4
+     /dev/zero c 0666 root root 1 5
+     /proc d 0555 root root
+     /dev/pts d 0755 0 0
+     /etc/init.d d 0755 0 0
+     /bin/init s 0755 0 0 ${pkgs.pkgsStatic.busybox}/bin/init
+     /bin/sh s 0755 0 0 ${pkgs.pkgsStatic.busybox}/bin/sh
+     /bin/busybox s 0755 0 0 ${pkgs.pkgsStatic.busybox}/bin/busybox
+     /etc/init.d/rcS s 0755 0 0 ${rcS}
+  '';
+in runCommand "frob-squashfs" {} ''
+  cp ${storefs} ./store.img
+  chmod +w store.img
+  ${pkgs.buildPackages.squashfsTools}/bin/mksquashfs - store.img -no-recovery -quiet -no-progress  -root-becomes store -p "/ d 0755 0 0"
+  ${pkgs.buildPackages.squashfsTools}/bin/mksquashfs - store.img -no-recovery -quiet -no-progress  -root-becomes nix  -pf ${pseudofiles}
+  cp store.img $out
+''

make-kernel.nix

@@ -24,6 +24,6 @@ in
 {
   vmlinux = callPackage ./make-vmlinux.nix {
     inherit tree;
-    config = config.kernel.config;
+    inherit (config.kernel) config;# checkedConfig;
   };
 }

run-qemu.sh

@@ -1,6 +1,8 @@
 #!/usr/bin/env nix-shell
 #! nix-shell -i bash -p qemu
 
-qemu-system-mips -M malta -m 256 \
+qemu-system-mips \
+    -M malta -m 256 \
     -append "earlyprintk=serial,ttyS0 console=ttyS0,38400n8 panic=10 oops=panic init=/bin/init loglevel=8 root=/dev/vda" \
+    -drive file=$2,format=raw,readonly,if=virtio \
     -kernel $1  -nographic -display none -serial mon:stdio