You can hook system process like system_server in Android 5.0+ devices. #How to build? 1 You should download ndk-r10c and export ndk root path to your bash profile.
2 Then enter Hook/jni path and input ndk-build.

#How to use? You should ensure that your device is root firstly.
1 Use adb push ../libs/armeabi/inject to /data/tmp/local
2 Then adb push ../libs/armeabi/libpayload.so to /system/lib
3 Next adb shell
4 Next su
5 Last ./data/tmp/local/inject

When adb shows Read-Only FileSystem, you should input mount -o remount rw /system in super status.