Book Image

Android System Programming

By : Roger Ye, Shen Liu
Book Image

Android System Programming

By: Roger Ye, Shen Liu

Overview of this book

Android system programming involves both hardware and software knowledge to work on system level programming. The developers need to use various techniques to debug the different components in the target devices. With all the challenges, you usually have a deep learning curve to master relevant knowledge in this area. This book will not only give you the key knowledge you need to understand Android system programming, but will also prepare you as you get hands-on with projects and gain debugging skills that you can use in your future projects. You will start by exploring the basic setup of AOSP, and building and testing an emulator image. In the first project, you will learn how to customize and extend the Android emulator. Then you’ll move on to the real challenge—building your own Android system on VirtualBox. You’ll see how to debug the init process, resolve the bootloader issue, and enable various hardware interfaces. When you have a complete system, you will learn how to patch and upgrade it through recovery. Throughout the book, you will get to know useful tips on how to integrate and reuse existing open source projects such as LineageOS (CyanogenMod), Android-x86, Xposed, and GApps in your own system.
Table of Contents (15 chapters)

Kernel changes

With effect from Android 4.4, SELinux is on by default. When we change the filesystem in Android, we have to take care of the SELinux settings as well. This will make the configuration more complicated than what we expect. If you are interested in this, you can do your homework to configure SELinux for this case.

In this book, we will disable SELinux by default so that we can concentrate on our topics. To disable SELinux, we have to make some changes the kernel configuration file. You can check the changes using the git command as follows:

$ cd $AOSP/kernel
$ git branch
* android-x86emu-3.10
$ gitk

We can see the changes in the android-x86emu-3.10 branch using gitk, as shown in the following screenshot. We can see that we set the default security to DAC and removed the SELinux setting, CONFIG_SECURITY_SELINUX=y:

Disabling SELinux in the ranchu kernel