Document the SELinux extensions to the Android init language.

Change-Id: I9b066e0789c93e5147c28a60baeed91c44dd9359
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
diff --git a/init/readme.txt b/init/readme.txt
index fe0d15d..9cc291c 100644
--- a/init/readme.txt
+++ b/init/readme.txt
@@ -88,6 +88,13 @@
    supplemental groups of the process (via setgroups()).
    Currently defaults to root.  (??? probably should default to nobody)
 
+seclabel <securitycontext>
+  Change to securitycontext before exec'ing this service.
+  Primarily for use by services run from the rootfs, e.g. ueventd, adbd.
+  Services on the system partition can instead use policy-defined transitions
+  based on their file security context.
+  If not specified and no transition is defined in policy, defaults to the init context.
+
 oneshot
    Do not restart the service when it exits.
 
@@ -182,6 +189,21 @@
    device by name.
    <mountoption>s include "ro", "rw", "remount", "noatime", ...
 
+restorecon <path>
+   Restore the file named by <path> to the security context specified
+   in the file_contexts configuration.
+   Not required for directories created by the init.rc as these are
+   automatically labeled correctly by init.
+
+setcon <securitycontext>
+   Set the current process security context to the specified string.
+   This is typically only used from early-init to set the init context
+   before any other process is started.
+
+setenforce 0|1
+   Set the SELinux system-wide enforcing status.
+   0 is permissive (i.e. log but do not deny), 1 is enforcing.
+
 setkey
    TBD
 
@@ -191,6 +213,10 @@
 setrlimit <resource> <cur> <max>
    Set the rlimit for a resource.
 
+setsebool <name>=<value>
+   Set SELinux boolean <name> to <value>.
+   <value> may be 1|true|on or 0|false|off
+
 start <service>
    Start a service running if it is not already running.