Overview about the priv-app applications
Core permissions:
Permissions which is defined in the frameworks/base/core/res/AndroidManifest.xml
Before Oreo(8.0),
SignatureorSystem permission is no longer supported to /system partition
APKs which are inside the /system/priv-app directory only able to access signature permissions
On Oreo(8.0),
privapp-permissions.xml is introduced to grant system permissions
After Oreo(8.0),
Device won’t boot if permissions are not granted or deny in the privapp-permissions.xml
