Android internals 05 - Dalvik VM (rev_1.1)

Android internalsEgor ElizarovSPbSU 2012

Egor Elizarov SPbSU 20122

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Lecture 5

Dalvik VM

yegor.yelizarov(at)gmail.com

http://vk.com/android_internalsRev: 1.1Last update: 05/30/2012


Previous time

Vanilla

Kernel types

Android/Kernel interaction

“Androdized” kernel features

Bionic

Log system


Virtual Machines

VM concept was introduced in 1960s in Cambridge

Defined by Popek & Goldberg in 1973 as "an efficient, isolated duplicate of a real machine"

System VM (Whole OS emulation)

Process VM (One program emulation)


Virtualization approaches

Paravirtualization

Full virtualization

HW assisted virtualization


Process VM types

Register VM

Limited number of registers with addresses

State register

List of instructions

Stack VM

Stack

Reverse Polish notation

Load/Store


Dalvik VM

Register based

Designed for low memory requirements

Relying on OS– Memory management

– Thread support

– Process isolation


Dalvik VM (2)

Allow multiple VM instances to run once

Supports Java Debug Wire Protocol

Based on Apache Harmony (Open Source Java)


Dalvik bytecode

Quite similar to common real architectures

Fixed size frames with particular number of registers (one per method)

32-bit registers

Reach meta information for each method


Dalvik bytecode example


ARM ASM example


Interpreter core

Portable (C)

Fast (C + ASM)

JIT (C + ASM + JIT)

Debug (C + ASM + profiling & single stepping)


Just-In-Time

Source: http://dl.google.com/googleio/2010/android-jit-compiler-androids-dalvik-vm.pdf


Android application

No single entry point

Activities, Services, Broadcast Receivers, Content Providers

Intents

New VM instance (Copy on write)


Dalvik EXecutable

Source: http://stid.googlecode.com/files/2008-05-29-Presentation-Of-Dalvik-VM-Internals.pdf


Zygote

Nascent VM process

Starts at boot time

Preloads and preinitializes classes

fork()s on command


Java application caching


Java application launching

Source: http://coltf.blogspot.com/p/android-os-processes-and-zygote.html


Dalvik porting

Core libraries should work from scratch

Implement JNI call bridge

Use portable interpreter

Replace opcode stubs

Use debug execution mode for debugging


Next Time

Android IPC

Typical Android subsystem


Useful links

http://vk.com/android_internals

K.Sutner. Register Machines. Carnegie Mellon University. Fall 2011 URL: http://www.cs.cmu.edu/~cdm/pdf/RegisterMach-6up.pdf

M.Schoeberl. Design and implementation of an Effective Stack Machine. Viena, Austria. URL: http://ti.tuwien.ac.at/rts/people/schoeberl/publications/stack.pdf

Y. Shi, D. Gregg, A. Beatty, M. A. Ertl. Virtual Machine Showdown: Stack Versus Registers. Dublin, Viena. URL: http://static.usenix.org/events/vee05/full_papers/p153-yunhe.pdf

http://www.dalvikvm.com/


Useful links (2)

http://pallergabor.uw.hu/common/understandingdalvikbytecode.pdf

$ANDROID_ROOT/dalvik/docs/

http://s.android.com/tech/dalvik/dalvik-bytecode.html

D. Bornstein. Dalvik VM Internals. 2008 URL: http://stid.googlecode.com/files/2008-05-29-Presentation-Of-Dalvik-VM-Internals.pdf

http://coltf.blogspot.com/p/android-os-processes-and-zygote.html

http://www.google.com/events/io/2010/sessions/jit-compiler-androids-dalvik-vm.html

http://pallergabor.uw.hu/common/understandingdalvikbytecode.pdf

http://s.android.com/tech/dalvik/dalvik-bytecode.html

http://coltf.blogspot.com/p/android-os-processes-and-zygote.html


Thanks to

Sergey Matyukevich for review and advices (www.linkedin.com/pub/sergey-matyukevich/31/889/769)

Nikolay F. Fominykh for review and advices

Nikita Shulga for advices and notes (http://www.linkedin.com/pub/nikita-shulga/8/582/287)

Grigory Tolstolytkin for advices and notes (http://www.linkedin.com/pub/grigory-tolstolytkin/2a/b41/74)

Android internals 05 - Dalvik VM (rev_1.1)

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