What is The Binder framework?

The Binder framework is one of the new features that Android introduces for Linux Kernel. It is meant for inter-process communication. Therefore, processes and thread are needed to understand the binder framework, a thorough concept on the underlying theories, such as multitasking. 

Android is developed by the Open Handset Alliance and Google on the basis of the Linux 2.6 standard kernel with new features for use in mobile devices. Out of various kernel modules, Binder driver offers a new IPC mechanism for Linux. Systems are developed by using four programming languages. The Java native interface enables Java to overcome obstacles in direct execution of native code. 

Although The Dalvik virtual machine (DVM) does not claim to be a Java virtual machine (JVM) due to licensing reasons but serves the same purpose. It is well adapted to ARM hardware. This different design principle is essential for mobile purposes with limited battery capacity. The use of native libraries can allow bypassing the type and border checking of the virtual machine and opens the door to stack-overflow attacks.

How does the binder framework work?

Once the DVM is started each of its new instances is cloned a system service called Zygote. When an Android application starts, this process enables it for the manipulation of the heap without using the original data. It also makes a similar layout for each application. 

Each application of Android is written with up to 4 different components at a time. Each component has a special subject for long duration purposes. The activity enables applications to perform screening and receiving interaction created by the user. The service component is used by Android for longer performance and all background tasks must be done here. The content provider enables an interface to access data like a file or network streams such as SQL-like databases. The broadcast receiver handles the messages like ‘new message’, ‘low battery’, etc. The application manifest stores information Android. 

Different data are exchanged through inter-component communication, or inter-process communication, provided the specific components belong to different processes (apps). The communication works with a basic data-structure. The operation of services is controlled by IPC. Actually, the IPC Binder mechanism is the key technology for the distributive system in the Android OS. There is a three-layer security measure in Android. The basic layer consists of two partitions, called system and data. DAC model Linux is used for separation among apps and the identification of the author. Then the MAC model is used. This model has a set of permissions and a set of exported services inclusive of access restrictions. The problem created because of same UID and GID has been overcome by the system of differentiation of apps into type A and type B. 

What are the advantages of the binder framework over other operating systems?

Developed under the leadership of Dianne Hackborn, the binder provides a richer abstraction that the traditional modern operating system cannot provide. More specifically, the Binder imposes bindings upon functions and data in a different execution environment. And, Android’s Binder is a customized implementation of OpenBinder. 

The Binder framework provides some advanced facilities that a simple interprocess messaging system cannot provide. The most crucial enhancement is that methods on remote objects can be called like a local object method by using synchronous method call. There are some concepts behind such facilities. Firstly, the communication model can simultaneously work on the client service and on the server side by using a client-side proxy and a thread pool. Secondly, sending data from one process to another process is called transaction. During the transaction process of data, various types of fields are used, such as cookie field, data field, target command field etc. Moreover, this concept facilitates the implementation of the asynchronous IPC protocol. Thirdly, from the object’s point of view, the transaction data are called parcel. This is, actually, the transmitted data structure. The process of parcel building is called marshaling or flattening an object. Fourthly, the death notification is provided to a local Binder object when a remote Binder object is terminated. 

The context manager is a special module of the Binder framework. This is needed to establish communication between clients and remote Binder without hampering security feature of the Binder. However, in Android, this is called service manager. An intent is a type of message used on Java API layer by the developers. This is abstract in this sense that the performer of the expected operation should not necessarily be defined. The Binder is widely used in Android for communication between processes. So, it’s a very important module. The Binder security model secures the communication channel between the processes and guarantees identification. It checks security matters before delivering the PID and UID numbers. 

Where is the binder framework is used? (Use of the binder framework)

Implementation of the Binder framework includes AIDL, Java API Wrapper, JNI Wrapper, C++ Middleware and C Kernel Driver. Kernel Driver is written in C language and is the central unit of the Binder framework; therefore, it uses several mechanisms such as Binder Tread Support, Binder Transactions and several others. The example of IPC Message Flow includes Testing Environment, Message Flow, and Call Stacks.