The key issues for teaching or learning Android and Linux Kernel

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NTU CSIE 2017.01.16The key issues for teaching or learning

Android and Linux Kernel梁文耀, CTO

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■ Android: http://www.slideshare.net/williamwyliang/an-introduction-to-the-android-framework-a-core-architecture-view-from-apps-to-the-kernel

■ Linux Kernel: http://www.slideshare.net/williamwyliang/an-introduction-to-the-linux-kernel-and-device-drives-ntu-201603-59718004

■ Android Device Drivers: http://www.slideshare.net/williamwyliang/android-device-driver-structure-introduction

■ Design Pricinple for H/W Drivers: http://www.slideshare.net/williamwyliang/operating-systems-and-software-design-for-hardware-components

References

http://www.slideshare.net/williamwyliang/an-introduction-to-the-android-framework-a-core-architecture-view-from-apps-to-the-kernel



http://www.slideshare.net/williamwyliang/an-introduction-to-the-linux-kernel-and-device-drives-ntu-201603-59718004



http://www.slideshare.net/williamwyliang/android-device-driver-structure-introduction



http://www.slideshare.net/williamwyliang/operating-systems-and-software-design-for-hardware-components





Basic Topics for Kernel 1/2

■ Device file concept■ File operations■ System calls■ Dynamic loadable kernel module■ Kernel memory management■ Concurrency control■ Synchronizations■ Performance issues



Basic Topics for Kernel 2/2

■ Interrupt handling and ISR■ Process control■ Waiting queues■ Blocking accesses■ Bottom half■ Atomic context■ Linux device model and sysfs■ Other types of device drivers



Basic Topics for Android 1/2

■ Android framework integration overview■ Apps and framework programming■ Kernel vs. user space device drivers■ Native shared libraries■ Android NDK■ Java native interface■ Device control flow for Android and Linux■ Framework and hardware services



■ Android device control model and service-oriented device management

■ Binder IPC and AIDL■ Android booting flow■ System services and service

management■ Android HAL and interfaces■ HAL Stub and HAL Module

Basic Topics for Android 1/2



in 15 minutes

A Brief Introduction for Android and LInux Kernel



Android vs. Linux

■ Android differs from the typical GNU/Linux in that Android adopts only the Linux kernel, not everything.

■ The first process ‘init’ transfers to Android’s own application environment.

■ The Bionic libc is used instead of glibc or uClibc.

■ As a result, it is called Android/Linux, not GNU/Linux.



Android Architecture



The Linux Kernel

• Android relies on Linux version 2.6 and later for core system services such as security, memory management, process management, network stack, and driver model.

• The kernel also acts as an abstraction layer between the hardware and the rest of the software stack.

Why Linux?

• Great memory and process management

• Permissions-based security model

• Proven driver model

• Support for shared libraries

• It’s already open source!



About the Linux Kernel

• An implementation of UNIX• Multitasking• File systems• Distributions• Device Management• System Interface• Threading• IPC



Android Framework

• Mixed Language/Layer Design• Application Framework• Services• Native Shared Library• Dalvik Virtual Machine



An Overview: from Apps to H/W

• User level (user mode)• Write a user program• Compile & Link• Execution

• Kernel (kernel mode)• Load the program• System call• Device driver

• Hardware manipulation



Linux Kernel and the Drivers



OS for I/O

• Provide protection to shared I/O resources• Provides abstraction for accessing devices• Handles the interrupts generated by I/O devices• Provide equitable access to the shared I/O

resources• Schedule accesses in order to enhance system

throughput

© Computer Organization and Design: The Hardware/Software Interface, David Patterson and John Hennessy



Role of the Device Drivers

• Device drivers are usually treated as black boxes for the application developers.

• They resemble as a software layer lying between the applications and the actual devices.

• A device driver performs user requests in a standardized manner.



How Linux Treats Devices

• Unix/Linux see devices as special files•Device files

• Enable users to employ familiar commands and functions such as open, read, write, and close

•File Operations vs. Device Accesses



• Android Application

• Android Application Framework• Android Java/C/C++ Interface• Android/Linux Native Layers• Linux System Calls• Linux Device Driver• Hardware and Control

Android/Linux Integration



The Android HAL



System Integration Flow

• Implement the device driver• Implement the HAL Module• Implement the Native Stub• Implement the Hardware Service• Implement the Software Management

Component• Implement Applications



Kernel Module (.ko)

Kernel Module(C Code)

Implement Device Driver

File Operations



Shared Library (.so)


HAL Module(Native Code)

Implement HAL Module

System call Kernel Module (.ko)

HAL DeviceInterface

File Operations




HAL Stub(JNI Native Code)



Implement Native Stub

hw_get_module

System callKernel Module (.ko)


HAL DeviceInterface

File Operations

NativeFunctions






Implement Hardware Service

hw_get_module

System callKernel Module (.ko)


Android Service (APK+.so)

Hardware Service(Java Code)

JNI

BinderInterfac

e

HAL DeviceInterface

NativeFunctions

File Operations



Hardware Service(Java Code)


External Library (JAR)



Device Manager(Java Code)

Implement Mgmt. Component

hw_get_module

JNI

System call

Android Service (APK+.so)


Kernel Module (.ko)

Binder IPC

BinderInterfac

e

HAL DeviceInterface

NativeFunctions

File Operations



for the rest time of the talk, if still available :p

Let’s go back and review the contents of the reference

pages.



Q&A