Add /apex tmpfs mount and mount it.

APEX filesystem images will now be mounted in /apex.

Also, make sure /data/apex is created with the right ACL.

Bug: 112455435
Test: flash and wipe, /apex is mounted as tmpfs, /data/apex is created
Change-Id: Ie27775e9f40a27b510272f212762624a04e94f1d

rootdir/Android.mk

@@ -77,7 +77,7 @@ endif
 #
 # create some directories (some are mount points) and symlinks
 LOCAL_POST_INSTALL_CMD := mkdir -p $(addprefix $(TARGET_ROOT_OUT)/, \
-    sbin dev proc sys system data odm oem acct config storage mnt $(BOARD_ROOT_EXTRA_FOLDERS)); \
+    sbin dev proc sys system data odm oem acct config storage mnt apex $(BOARD_ROOT_EXTRA_FOLDERS)); \
     ln -sf /system/bin $(TARGET_ROOT_OUT)/bin; \
     ln -sf /system/etc $(TARGET_ROOT_OUT)/etc; \
     ln -sf /data/user_de/0/com.android.shell/files/bugreports $(TARGET_ROOT_OUT)/bugreports; \

rootdir/init.rc

@@ -269,6 +269,12 @@ on init
     # that they can be chown'd to system:system later on boot
     write /sys/class/leds/vibrator/trigger "transient"
 
+    # Setup APEX mount point and its security context
+    mount tmpfs tmpfs /apex nodev noexec nosuid
+    chmod 0755 /apex
+    chown root root /apex
+    restorecon /apex
+
 # Healthd can trigger a full boot from charger mode by signaling this
 # property when the power button is held.
 on property:sys.boot_from_charger_mode=1
@@ -523,6 +529,8 @@ on post-fs-data
 
     mkdir /data/anr 0775 system system
 
+    mkdir /data/apex 0770 root root
+
     # NFC: create data/nfc for nv storage
     mkdir /data/nfc 0770 nfc nfc
     mkdir /data/nfc/param 0770 nfc nfc