cm: SELinux policy for persistent properties API

* Set up persistent properties for devices with a /persist partition.

Change-Id: I78974dd4e25831338462c91fc25e36e343795510

prebuilt/common/etc/init.local.rc

@@ -104,6 +104,9 @@ on boot
     setprop net.tcp.usercfg.wifi       1
     setprop net.tcp.usercfg.lte        1
 
+    # Persistent properties (only created if persist exists)
+    mkdir /persist/properties 0770 system system
+
 # adb over network
 on property:service.adb.tcp.port=5555
     stop adbd

sepolicy/file.te

@@ -11,3 +11,6 @@ type sysfs_devices_system_iosched, file_type, sysfs_type;
 
 # Recovery's "cache"
 type recovery_cache_file, file_type, mlstrustedobject;
+
+# Persistent property storage
+type persist_property_file, file_type;

sepolicy/file_contexts

@@ -34,3 +34,6 @@
 
 # Lockscreen wallpaper
 /data/system/users/[0-9]+/keyguard_wallpaper   u:object_r:wallpaper_file:s0
+
+# Persistent properties
+/persist/properties         u:object_r:persist_property_file:s0

sepolicy/system_server.te

@@ -1,2 +1,6 @@
 allow system_server recovery_cache_file:dir rw_dir_perms;
 allow system_server recovery_cache_file:file create_file_perms;
+
+# Persistent properties
+allow system_server persist_property_file:dir rw_dir_perms;
+allow system_server persist_property_file:file { create_file_perms unlink };