Another feature of system apps is that they use native libraries (libsomething.so files) from the common system libraries directory (typically /system/lib or /system/lib64), and not from the app-private libraries directory (e.g., /data/app/com.example.HelloJni/lib/arm). Before Android Nougat, user apps were free to load and use the system native libraries. Restrictions have been imposed later, see https://developer.android.com/about/versions/nougat/android-7.0-changes.html#ndk.