Merge pull request #1010 from offlinehacker.

Although this is a release canidate version of kernel 3.12, there are
reasons for merging this anyway, as discussed in #1010 and #1006.

Thanks to @offlinehacker for this and the initial pull request.

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

@@ -169,6 +169,9 @@ with stdenv.lib;
   SECURITY_SELINUX_BOOTPARAM_VALUE 0 # Disable SELinux by default
   DEVKMEM n # Disable /dev/kmem
   CC_STACKPROTECTOR y # Detect buffer overflows on the stack
+  ${optionalString (versionAtLeast version "3.12") ''
+    USER_NS y # Support for user namespaces
+  ''}
 
   # Misc. options.
   8139TOO_8129 y

pkgs/os-specific/linux/kernel/linux-3.12.nix

@@ -0,0 +1,16 @@
+{ stdenv, fetchurl, ... } @ args:
+
+import ./generic.nix (args // rec {
+  version = "3.12-rc2";
+
+  src = fetchurl {
+    url = "https://www.kernel.org/pub/linux/kernel/v3.0/testing/linux-${version}.tar.gz";
+    sha256 = "1m24fh3cwmkb1scn3sl7gbc50jl53v357kjpgda9avi3ljxmyq5z";
+  };
+
+  features.iwlwifi = true;
+  features.efiBootStub = true;
+  features.needsCifsUtils = true;
+  features.canDisableNetfilterConntrackHelpers = true;
+  features.netfilterRPFilter = true;
+})