On boot, Android runs restorecon on a number of virtual directories,
such as /sys and /sys/kernel/debug, to ensure that the SELinux labels
are correct. To avoid causing excessive boot time delays, the restorecon
code aggressively prunes directories, to avoid recursing down directory
trees which will never have a matching SELinux label.

See:
* https://android-review.googlesource.com/93401
* https://android-review.googlesource.com/109103

The key to this optimization is avoiding unnecessarily broad regular
expressions in file_contexts. If an overly broad regex exists, the tree
pruning code is ineffective, and the restorecon ends up visiting lots of
unnecessary directories.

The directory /sys/kernel/debug/tracing contains approximately 4500
files normally, and on debuggable builds, this number can jump to over
9000 files when the processing from wifi-events.rc occurs. For
comparison, the entire /sys/kernel/debug tree (excluding
/sys/kernel/debug/tracing) only contains approximately 8000 files. The
regular expression "/sys/kernel(/debug)?/tracing/(.*)?" ends up matching
a significant number of files, which impacts boot performance.

Instead of using an overly broad regex, refine the regex so only the
files needed have an entry in file_contexts. This list of files is
essentially a duplicate of the entries in
frameworks/native/cmds/atrace/atrace.rc .

This change reduces the restorecon_recursive call for /sys/kernel/debug
from approximately 260ms to 40ms, a boot time reduction of approximately
220ms.

Bug: 35248779
Test: device boots, no SELinux denials, faster boot.
Change-Id: I70f8af102762ec0180546b05fcf014c097135f3e

app_domain was split up in commit: 2e00e637 to
enable compilation by hiding type_transition rules from public policy.  These
rules need to be hidden from public policy because they describe how objects are
labeled, of which non-platform should be unaware.  Instead of cutting apart the
app_domain macro, which non-platform policy may rely on for implementing new app
types, move all app_domain calls to private policy.

(cherry-pick of commit: 76035ea0)

Bug: 33428593
Test: bullhead and sailfish both boot. sediff shows no policy change.
Change-Id: I4beead8ccc9b6e13c6348da98bb575756f539665

In order to support platform changes without simultaneous updates from
non-platform components, the platform and non-platform policies must be
split.  In order to provide a guarantee that policy written for
non-platform objects continues to provide the same access, all types
exposed to non-platform policy are versioned by converting them and the
policy using them into attributes.

This change performs that split, the subsequent versioning and also
generates a mapping file to glue the different policy components
together.

Test: Device boots and runs.
Bug: 31369363
Change-Id: Ibfd3eb077bd9b8e2ff3b2e6a0ca87e44d78b1317