There a lot of mobile platforms SymbianOS IPhoneOS BlackberryOS WinMo ALP OpenMoko WebOS Android BadaOS

1. Technical Review
www.folio3.com

2. www.folio3.com
Mobile Platforms
 There a lot of mobile
platforms
 SymbianOS
 IPhoneOS
 BlackberryOS
 WinMo
 ALP
 OpenMoko
 WebOS
 Android
 BadaOS
 Mobile Platform
requirements
 Stable real-time kernel
 Steady HAL
 Power management
 Rich system libraries
 Rich application
framework
 Essential applications
 Steady UI
 Optimized application
management

3. www.folio3.com
Introduction
 Another Mobile Platform
 Offers
 Operating System
 Kernel: Linux 2.6
 Sys Library: Subset of LibC, LibM,
 A complete application stack
 User land applications
 Development infrastructure
 SDK 2.0.1
 Java
 NDK 1.5
 C/C++
 Components reusability and integration
 Based on ARM based processor
 Can be run on x86 platform

4. (Cont.) Introduction
 License
 Open source from the beginning
 Apache License
 Made available
 Primarily for
 Cell (mobile) devices
 But can also be use on
 MIDs
 Nettops
 Mobile gaming devices
 Other light weight devices
 Releases
 1.5 – Cupcake
 1.6 – Donut
 2.0 – Eclair
 2.1 – Extension to Eclair
www.folio3.com

5. Support
 Full multimedia hardware and software stack
 Advanced application supports
 Background services
 Complex widgets
 Easy and manageable lifecycle
 Full control of the hardware through well designed
APIs
 Advanced I/O supports
www.folio3.com

6. History
 July 2005
 Google acquired Android Inc.
 November 2007
 OHA, Open Handset Alliance, consortium started with
 Texas Instruments, Broadcom Corporation, Google, HTC, Intel, LG, Marvell
Technology Group, Motorola, Nvidia, Qualcomm, Samsung Electronics, Sprint
Nextel, T-Mobile
 October 2008
 First Android phone release – HTC Dream
 December 2008
 OHA, Open Handset Alliance, expanded with
 ARM Holdings, Atheros Communications, Asustek Computer Inc, Garmin Ltd.,
Softbank, Sony Ericsson, Toshiba Corp, Vodafone Group
 January 2010
 OHA, Open Handset Alliance, expanded with
 China Mobile Comm Corp., China Telecomm Corp., China United
Network Comm., KDDI Corp., NTT DoCoMo Inc., Bouygues Telecom, etc
www.folio3.com

7. Open Handset Alliance

8. Kashif Ali Siddiqui - ksiddiqui@folio3.com | 2010
Architecture & Design

9. The Kernel
 Kernel – Linux 2.6
 Patches – Android
 Ashmem, binder, and Android Power Management (PM)
 OS HAL
 Provides management for
 Memory modules (Primary, Secondary)
 Processes
 Provides networking stack
 Full TCP/IP v4 support
 Provides device drivers
 Telephony, GSM, CDMA, GPRS, Edge, 3G, WiFi, Bluetooth, others
transceivers
 Accelerometer, gyroscope , GPS transceiver, magnetometer
 Touchscreen, keyboard, keypad, camera
 VGA display
 Others
www.folio3.com

10. Native System Libraries
 C/C++ libraries
 Interface through Java layer
 Includes …
1. Standard UNIX libc libraries
 Called BIONIC
 Derived from BSD
 Only on ARM and x86 platforms
1. Surface manager
2. 3D graphics with/without H/W acceleration using OpenGL ES
3. 2D scalable vector graphics using SGL (Skia)
4. TrueType fonts
5. Media frameworks including audio, video codecs
6. HTTP rendering engine – Webkit
7. Light database management through SQLite3
8. TCP socket security through SSL
www.folio3.com

11. Java Runtime
 Specialized Virtual Machine
 Dalvik Virtual Machine
 Written by Dan Bornstein
 Architecture - Register-based machine
 Class files - Delvik Executibles .dex files
 Structures ? Difference from normal class files
 Light weight, compact, and processor and memory efficient
 An uncompressed .dex size is less than compressed .jar
 Can contain several classes
 Code reordering and re-organization at installation time
 Designed to enable execution of multiple instances
www.folio3.com

12. (Cont.) Java Runtime
 Relies on Linux for underlying functionality such as
multi-threading and low level memory management
 The dx utility
 No official JIT compiler
 Core library – Java 1.5 SDK
 Completely not compatible with Java SE and ME
class library profiles
 E.g., J2ME, AWT, Swing are not supported
 Subset of the Apache Harmony
www.folio3.com

13. Dalvik Virtual Machine
 Motivation
 Can run on lesser RAM
 Can run on slower CPUs
 Can run without swap space defined
 Can run with less power
 Can enable concurrent execution of multiple instances
 Memory efficiency
 More memory requirement
 Each application runs in its own address space – process
 Optimization
 Shared constant pool in .dex files
 Minimal repetition
 Per type pools (implicit typing)
 Implicit labeling
www.folio3.com

14. (Cont.) Dalvik Virtual Machine
 Emphasis to use clean (shared/private) memory
 Emphasis to limit the use of dirty private memory
 Memory types
 Clean memories
 Common .dex files (shared)
 Application specific .dex files (private)
 Private dirty memories
 Application “live” .dex structures
 Application heap
 Shared dirty memories
 Common “live” .dex structures
 Shared COW heap
www.folio3.com

15. (Cont.) Dalvik Virtual Machine
 Separate Garbage Collection meta
 Specialized GC meta structures
 Optimized for memory usage with less fragmentation and sharing
 Each application heap is GCed independently
 Run time efficiency
 Install time verification
 Static type and reference checking, indices and offset checking
 Reduces run-time cost of checking the code
 Install time optimization
 Byte swapping and padding
 Static linking
 Inlining special native methods
 Pruning empty methods
 Adding auxiliary data
 Creating shared constant pools
www.folio3.com

16. (Cont.) Dalvik Virtual Machine
 Why
 To avoid instruction dispatch
 Avoid unnecessary memory accesses
 Consume instruction stream efficiently
 Higher semantic density per instruction
 Uses register based interpreter
 Stacks are used to keep tracks on the methods nesting and
calling sequence
 Efficient initialization and management of array data
www.folio3.com

17. Enter the Zygote
 The first process
 Similar to UNIX init process
 Preloads and preinitializes shared classes
 Create clean shared memories
 Create dirty shared memories
 Uses UNIX fork() to start a new application
 Provides shared mapping to the child
processes for shared classes
 Promotes the sharing of common code
www.folio3.com

18. Application Framework
 All Java Libraries
1. Activity manager – Manages application life cycle
 An activity is an application UI window
 Activities are managed through system’s activity stack
 Four states of activity
 Foreground – top on activity stack
 Paused – when lost focus, and still showing (partially) on the screen.
 Stopped – When completely hidden by another activity
 Killed - Killing the process
1. Package manager – Installed software manager
2. Window manager – Manages UI components along with
screens and transitions
3. Telephony manager – Provides the interface to the underneath
telephony/GSM services
www.folio3.com

19. (Cont.) Application Framework
5. Resource manager – Provides access to the non-code
components such as images, icons, audio/video, string
tables, etc.
6. Content manager – Mediates in the data sharing among
applications, such as contacts are shared to other
application.
 Various content providers
 Can access others, and publish own
 Content provider security
5. Location manager – Provides intends on registered
location. Uses GPS, or GSM tower ID or WiFi location
beacons to determine location.
www.folio3.com

20. (Cont.) Application Framework
8. View system – Provides widgets to the
application to create activities
 Two new views; MapView and WebView
8. Notification manager – Enables the application
to show custom alerts on the status bar.
9. XMPP services – Peer-to-peer Android device
communication layer
www.folio3.com

21. Applications
 Java applications
 Runs in separate user address space - process
 Each is managed by its own DVM instance
 Can be replaced
 Can be installed from
 Online app stores
 Usually end up in calling native code that might
goes to the kernel system call
www.folio3.com

22. Security & Access Control
 Only Java applications can be installed
 Each application runs in its process under DVM
 Each process (DVM) is a sandbox
 Each application has its own UIDs and GIDs
 Additional access control on several operations
 Architecture:
 No application by default has permission to perform any operation that would
adversely impact other applications, operating system, or the user.
 Such as
 R/W on user’s private data; contacts
 R/W on another application data files
 Performing network (through GPRS/Edge, Wifi), bluetooth access, or
 Keeping the device awake
 Application certificate, UID/GID, Access Control and URI Permissions
www.folio3.com

23. (Cont.) Security & Access
Control
 Application signing and certification
 Contains authors identification, and signing authority
 Access control
 The sandbox is executed with some permissions (access control) to the
operations.
 These access control permissions are defined in the application package,
 Set at installation point, and
 Can be modified by user when OS prompt for the permission to perform the
operation
 UIDs and GIDs
 Each application and its components are installed with unique UID
 Limits the applications to access
 Shared UIDs
 Only allow applications with identical digital signature
 Each file created has the creator’s UID
www.folio3.com

24. (Cont.) Security & Access
Control
 URI permissions
 Mainly for content providers
 Allows capability like access control
 Enables applications to manage other application’s accesses on their shared
contents
www.folio3.com

25. OS Concerns
 Kernel
 No udev support
 Static hardware linking and policy
 No dynamic hotplug control and management
 Replaced by Vold
 Provides static hotplug events processing
 Storage devices are not managed by HAL (VFS)
 Replaced by Vold
 Responsible of mounting and unmounting of MMC subsystem
device
 Hardcoded power-management policy
 Layered PM design
 Android PM mapped on Linux PM module
 To change the Android PM policy requires code change
www.folio3.com

26. (Cont.) OS Concerns
 Limited, un-natural (non-Linux style) I/O support
 Un-orthodox touchscreen support
 No official support through tslib
 Fixed sized framebuffer
 No support for larger resolution > 1024x768
 Static hardware support assumptions
 Telephony (3G signal indicator hardcoded)
 Wifi (signal indicator hardcoded)
 Ringer volume slider assumes telephony present
 No official Ethernet support
 No X Window System support
www.folio3.com

27. (Cont.) OS Concerns
 LibC - Bionic
 No glibc support
 Only available on ARM and x86 platforms
 Partial pthreads support
 No SysV IPC support
 Limited C++ support
 No STL support
 No Linux headers
 Limiting the development of native binaries
www.folio3.com

28. Application Development
 Online official guide
 http://developer.android.com/guide/index.html
 Development with Eclipse
 Using ADT plugin
 Tools
 Android – To create/update projects
 Emulator – Qemu based ARM emulation system
 Debugger bridge – To interface with the emulator
 Ant – To compile and build projects into .apk files
 Keytool – To maintain keystore and private keys
 Jarsigner – To sign .apk files with private keys
www.folio3.com

29. (Cont.) Application
Development
 Requires to learn the following skills
1. Java programming language
2. Java 1.5 SDK library
3. Android application life cycle
4. Android APIs
5. Mobile HPC programming
6. Use of sensory hardware and Internet services
www.folio3.com

30. (Cont.) Application
Development
 Native Development (NDK)
 http://developer.android.com/sdk/ndk
 Java Vs. Native development
 Why native development is required?
 Situations
 Resource intensive work
 Complex algorithms
 Hardware interactions
 …
www.folio3.com

31. Limitations
 Kernel
 Limited support for Mass Storage Devices
 No official support for mouse, Ethernet devices
 No support of other filesystems, and hardware
 Very thin network protocol stack
 System libraries
 No support for IPC among the application
 Replaced by content manager
 Limited pthread support
 Limited UNIX/Linux native library support
www.folio3.com

32. (Cont.) Limitations
 Application
 Applications can only be installed on the primary nonvolatile
memory
 Most of the Linux binaries will failed to run on Android
 Only Java based application can be executed
 Native code can be only packaged as library modules for the Java
application
 No compatibility to the Jave ME and SE platforms
 No Enterprise integration solutions
 Missing push messaging or notifications
www.folio3.com

33. Comparison With Other
Mobile Platforms
IPhone Blackberry Android
Background application   
Multiprocessing   
Peer-to-peer communication   
Extensible & Scalable in HW support   
Platform support   
Application development & publishing   
www.folio3.com

34. Comparison With Other
Mobile Platforms
IPhone Blackberry Android
Third party community support   
Enterprise integration   
Multimedia support   
Optimized Java support   
Native development   
Security   
Organization Support   
www.folio3.com

35. Future of Android
 IS VERY BIG
 Increasing support for more hardware and platforms
 Extensions to more system level libraries
 Extensions to more Java runtime libraries
 Enterprise level support
 Increase in platform domain from cellphone market
to military, gaming, medical, and other domains
 And more …
www.folio3.com

36. Conclusion
 It uses Linux, but loses all the flexibility of Linux
 Based on the assumption of hardware support available on the
smart-phones with no/limited flexibility for dynamic adjustments
 Requires custom work and patching to enable Android to run on
other non-mobile platform and/or with more hardware
 Provides native development, but disallows the creation,
execution of the native applications
 Provides easy application development using Java
 Provides rich application stack and multimedia support
 Backed by a stronger organization Google
 Technically more stronger and mature platform than other mobile
OS platforms such as IPhoneOS, Blackberry OS and WinMo
www.folio3.com