This article explains how to reverse engineer Samsung's proprietary bootloader a.k.a. aboot and describes an undocumented feature which allows an end user to lock his bootloader and to prevent someone from using the download mode without his consent.
SELinux is part of the Android security model since Android 4.3. This article covers various aspects of the SELinux kernel policy in Android. I have dissected how the monolithic policy file is created in current Android's version. While analyzing checkpolicy source code, I digress a little on the policy file format. Finally, I present a tool to decompile a sepolicy file into a semantically equivalent set of SELinux statements (and which can be compiled back into a sepolicy!).