April 13, 2023

Porting and BindingDalvikVM with GlibC

Pipat Methavanitpong

Kunieda-Isshiki Laboratory

Outline Introduction to Android Introduction to Dalvik VM Introduction to Bionic LibC Introduction to QEMU Merits of Porting GLibC Dalvik VM Porting Attempted Approaches Available Alternative Ports How to Setup AOSP Build System

Introduction Android Open Source OS for smart devices

Smartphones, Tablets, Gadgets Developed by Google Based on Linux Kernel

With several custom modules Ranked 1st among other Smart Device OSes

81% market share in Q3, 2013 – IDC Report

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Google I/O 2013: Keynote – May 15, 2013

Android API Level Name ChartRelease Year 2009

1.5 – Cupcake 1.6 – Donut 2.0 – Éclair 2.1 – Éclair

2010 2.2 – Froyo 2.3 – Gingerbread

2011 3.0 – Honeycomb 3.1 – Honeycomb

2012 3.2 – Honeycomb

2013 4.0 – Ice-cream Sandwich 4.1 – Jellybean 4.2 – Jellybean 4.3 – Jellybean 4.4 – KitKat

Wikipedia – Android Version History (cited Nov 25, 2013)

Android System Architecture

Google I/O 2008 – Dalvik Virtual Machine InternalsE-Linux – Android Architecture (cited Nov 25, 2013)

Android Low-Level Architecture

Porting Android to Devices (cited Nov 25, 2013)

Android Architecture

K. Yaghmour, Embedded Android 1st edition, Chapter 2, Figure 2-1

Framework AOSP/dalvik

AOSP/libcoreAOSP/frameworks

AOSP/externals

FoundationAOSP/bionic

AOSP/systemAOSP/libnativehelper

AOSP/hardware…

Fancy AppsAOSP/packages

Introduction to Dalvik VM

K. Yaghmour, Embedded Android 1st edition, Chapter 2, Figure 2-1

Introduction to Dalvik VM The core of Android Applications

All fancy Android applications are run by it Register-based Process Virtual Machine

Think of running a Java application Intermediate Language = Dalvik Bytecode Executable File = Dalvik Executable (DEX)

A converted Java class done by “dx” tool Reduce redundancy in variables

Introduction to Dalvik VM Variable Length ISA

1 Word = 2 bytes = 16 bits Fetched 1 word a time

OP code is 8-bit length = Max of 256 instructions Use only 246 instructions Attached in the 1st word

Default Endianess is Little Default OP code handles up to 65536 Virtual Registers (VRs)

Ideally infinite VRs are 32-bit width 64-bit variable = concatenate 2 consecutive VRs together Has Pseudo Instruction concept

Must be optimized by “dexopt” before run 4 Types of constant pool: String, Type, Field, Method 2 Types of prelinked offset: VTab offset, Field offset

Source Android – Bytecode for the Dalvik VM (cited Nov 26, 2013)Source Android – Dalvik VM Instruction Formats (cited Nov 26, 2013)

Introduction to Dalvik VM 2 Modes of Machine Code Interpretation (Mterp)

Fast – Based on manually written assembly code for each OP code Portable – Based on compiled generic C++ files for each OP code

Enhancement Java Native Interface

Allow Dalvik VM to call native functions Just-In-Time compiler

Prepare bytecode segments into machine code ahead during run-time Zygote

Mother process which Create a Dalvik VM And preloads frequently used shared libraries

New Dalvik VM starts by forking from this template Dalvik VM Reduce loading time Save memory space (Copy-On-Write)

Forays in software development – Stack based vs Register based Virtual Machine Architecture, and the Dalvik VM (cited Nov 26, 2013)Linux For You – Virtual Machines For Abstraction: The Dalvik VM (cited Nov 26, 2013)Wikipedia – Just-in-time compilation (cited Nov 26, 2013)Google I/O 2010 – A JIT Compiler for Android’s Dalvik VM

Stack-based Virtual Machine Don’t name register in instuctions

Everything is queued up in its stack Simple design Instruction width is short Redundancy in using same variables

No name to registers = Copy on a stack repetitively

More instructions used to complete a task But, total program size is smaller than

Register-based

Y. Shi, D. Gregg, A. Beatty, Virtual Machine Showdown: Stack versus Registers, VEE’05Forays in software development – Stack based vs Register based Virtual Machine Architecture, and the Dalvik VM (cited Nov 26, 2013)Linux For You – Virtual Machines For Abstraction: The Dalvik VM (cited Nov 26, 2013)Coursera – Computer Architecture by David Wentzlaff L1S5: Machine Models

Register-based Virtual Machine Physical CPU analogy Explicitly naming register Instruction width is longer Can do complex register manipulation

No need to be in order like in Stack-based Fast

Fewer VM instructions An effect from larger instruction width can be

neglected A bit memory consuming

Larger program size Normally require a lot of space for virtual registers

Y. Shi, D. Gregg, A. Beatty, Virtual Machine Showdown: Stack versus Registers, VEE’05

From Source Code to Execution

Optimized DEX

dalvikvm

DEX filedexopt

Java Classdx

Java Source Codejavac

Forays in software development – Stack based vs Register based Virtual Machine Architecture, and the Dalvik VM (cited Nov 26, 2013)

DEX StructureHEADER The Header (size of 0x70 bytes)

STRING_IDS String Identifier List

TYPE_IDS Type Identifier List

PROTO_IDS Method Prototype Identifier List

FIELD_IDS Field Identifier List

METHOD_IDS Method Identifier List

CLASS_DEFS Class Definition List

DATA Data area for support contents above

LINK_DATA Data used in statically linked files

Source Android – Dalvik Executable Format (cited Nov 26, 2013)

How to port Dalvik VM to new Architecture Google mentions only for porting to other Android with

different architecture In short = Build for Target Document in AOSP/dalvik/docs/porting-guide.html

Steps Create new Machine Interpreter (Mterp) in both C and its

machine code for each instruction code Create new Mterp config for your architecture Update Mterp by AOSP/dalvik/vm/mterp/rebuild.sh

This assembles your written instruction codes InterpAsm-Your_Arch.S + InterpC-Your_Arch.cpp

Modify Target build configuration in AOSP/dalvik/vm/Dvm.mk

Set $(TARGET_ARCH) by lunch or export TARGET_ARCH=Your_Arch

Build new libdvm.so by m libdvm

libART (Android RunTime Library) Android 4.4’s experimental virtual machine library

Disabled by default Turn on by checking this option in Developer options

Changing to libART from libDVM Requires all apps to be recompiled = Restart + Super long first boot

Use Ahead-Of-Time (AOT) scheme instead of JIT Precompile Dalvik Bytecode into machine language during

installation Take longer time to install for the first time

Applications run faster Apps are in native form, so they are very ready to be executed

Saving more energy Apps end faster = More PEs idle time

Occupy more storage space Decompress to machine code

Android Headlines – Google is Looking to Replace Dalvik with ART (cited Nov 26, 2013)

Introduction to Bionic LibC Derivation of BSD standard C

library NetBSD (libc) + FreeBSD (libm)

Developed by Google Small

Fast Optimized for low clock

processors Upto 114% faster than GLibC

JNI vs. Native C bound with GLibC

Has several Linux kernel specific features

License

Fast Pthread implementation Based on Futexes Completely rewritten by Google

Currently support for ARM / x86 / MIPS

Partially POSIX compatible Not compatible with GLibC

No SysV IPC support Android has Binder IPC

No wchar support No C++ exception support Not full C++ STL Not fully POSIX Thread

compliant

BSD LGPL GPL MIT

BionicGLibC, uClibc

dietlibc musl

GLibC 2.11uClibc 0.9.30

Bionic 2.1

1,208,224 bytes

424,235 bytes

243,938 bytes

Wikipedia – Bionic (software) (cited Nov 25, 2013)ICCAS2012 – Benchmarking Java Application using JNI and Native C Application on AndroidCoding Relic – The Six Million Dollar LibC (cited Nov 25, 2013)Embedded Linux Conference 2013 – olibc: Another C Runtime Library

Introduction to QEMU Quick EMUlator Free and Open Source Hardware Virtualizer Can emulate

Whole system / board – Versatile Express-A9 qemu-arm-softmmu -M vexpress-a9

Only CPU – x86, sparc, ARM qemu-i386

Has Kernel-based Virtual Machine (KVM) support Accelerate emulation with same CPU architecture

as its Host

Wikipedia – QEMU (cited Nov 25, 2013)

Merits of Porting GLibC Dalvik VM Getting full capability of GLibC

C++ Exception handling Wide charactor handling POSIX Thread compliant

Can be run on any ordinary Linux GlibC is shipped with Linux by almost distros Consistence with other existing Linux programs

Can talk to each other under same SysV IPC

------------------------------------------------------------------ What could come after this

Comparison between Bionic and GLibC Dalvik VM Porting GLibC Dalvik VM for TCT processor

GLibC porting to TCT is under going

Porting Attempted Approaches1. Copy-Paste Bionic Dalvik VM

Failed Cannot find libraries

2. Copy-Paste Bionic Dalvik VM + Bionic LibC Failed

Something low-level failed

3. Copy-Paste Bionic Dalvik VM + Bionic LibC + Ashmem

Failed Something low-level failed (same output as previous attempt)

4. GLibC - Dalvik VM porting Not done Make modification to build/core Makefiles

Only HOST configurations

Testing Environment ARM

Use QEMU to emulate VExpress-A9 with bare Linux kernel with Busybox shell http://balau82.wordpress.com/2010/03/27/busybox-for-arm-on-qemu/

Use QEMU to emulate Vexpress-A9 with Ubuntu 13.04 http://releases.linaro.org/13.04/ubuntu/vexpress/

x86 Use QEMU to emulate QEMU’s x86 default board with Debian 7

Squeeze Run on Host machine directly

1st Attempt Copy-Paste Bionic Dalvik VM Does not work

No Bionic LibC for it Error message is

bash: [Directory to Dalvik VM]/dalvikvm: No such file or directory

This error message is ALSO OCCUR when run a GLibC linked program on an Android Emulator

2nd Attempt Copy-Paste Bionic Dalvik VM Copy Bionic LibC to /system/lib

/system/bin/linker is hardcoded to link with /system/lib It is done by setting “rpath” flag

Create dalvik-cache directory for Optimized DEX /data/dalvik-cache

Error message is Dalvik VM init failed (checked log file)

There is no Log file left No porting of liblog and Logger

3rd Attempt Setting is same as 2nd attempt This attempt was tested only on

Emulated VExpress-A9 with bare Linux kernel with Busybox shell

Linux kernel is shipped with Ashmem Ashmem = Annonymous Shared Memory

Sometimes, people call it Android Shared Memory Now shipped with Linux mainline residing in Staging

directory It is said that Ashmem is needed for Dalvik VM porting

Error message is Dalvik VM init failed (checked log file)

Failure cause is still unknownDalvik Virtual Machine on TS-7800 SBC (cited Nov 26, 2013)

4th Attempt Host version of Dalvik VM is linked with GLibC Fake an attribute of Host: HOST_ARCH

GLibC linked Dalvik VM for that architecture Try with ARM architecture

Modify several Makefiles to make sure AOSP builds for only Host side Many Makefiles contains builds for Host and Target in one file m dalvik-host conscrypt-hostdex

Minimum Dalvik VM build for Host

Create new Makefiles and Includes for new host architectures

Still not complete Configuration problems

Modifying Guide Build acp (Android’s cp tool)

Modify build/core/config.mk Force use acp for x86 Host From

To

Modify build/core/envsetup.mk to accept Host Architecture Overwrite From

To

$ m acp

$ BUILD_ARCH := $(HOST_ARCH)

$ BUILD_ARCH := $(HOST_ARCH)$ ifneq ($(HOST_ARCH_OWR),)$ HOST_ARCH := $(HOST_ARCH_OWR)$ endif

$ ACP := $(BUILD_OUT_EXECUTABLES)/acp$(BUILD_EXECUTABLE_SUFFIX)

$ ACP := $(HOST_OUT_ROOT)/linux-x86/bin/acp$(BUILD_EXECUTABLE_SUFFIX)

Guide Build acp (Android’s cp tool)

Modify build/core/config.mk Force use acp for x86 Host From

To

Modify build/core/envsetup.mk to accept Host Architecture Overwrite From

To

$ m acp

$ BUILD_ARCH := $(HOST_ARCH)

$ BUILD_ARCH := $(HOST_ARCH)$ ifneq ($(HOST_ARCH_OWR),)$ HOST_ARCH := $(HOST_ARCH_OWR)$ endif

$ ACP := $(BUILD_OUT_EXECUTABLES)/acp$(BUILD_EXECUTABLE_SUFFIX)

$ ACP := $(HOST_OUT_ROOT)/linux-x86/bin/acp$(BUILD_EXECUTABLE_SUFFIX)

Guide Modify build/tools/acp/Android.mk Disable acp build

From

To

Create new build/core/combo/HOST_linux-arm.mk Manually merge between HOST_linux-x86.mk and TARGET_linux-

arm.mk

Create new build/core/combo/include/arch/host_linux-arm/AndroidConfig.h Manually merge between linux-x86, target_linux-x86, and

target_linux-arm

$ include $(BUILD_HOST_EXECUTABLE)

$ ifeq ($(HOST_ARCH),x86)$ include $(BUILD_HOST_EXECUTABLE)$ endif

Available Alternative Ports idvk – Independent Dalvik

Not actually porting Just extract what Dalvik VM needs to be built from AOSP

Myriad Alien Dalvik Run Android apps on non-Android devices

IcedRobot Use OpenJDK instead of Sun JDK which was under license

problem between Google and Oracle libhybris.so

Overwrite Bionic symbol to solve incompatibility with GLibC

Written by Mer developer Used by Sailfish OS and Ubuntu Touch

How to Setup AOSP This guide assumes an environment of x86 Ubuntu-64bit

12.04++

1. Download and Install Oracle JDK6 (see later slide)

2. Download and Install Other Required Software1. Required Packages

2. Repo

Source Android – Downloading and Building (cited Nov 26, 2013)

$ sudo apt-get install git gnupg flex bison gperf build-essential zip curl libc6-dev libncurses5-dev:i386 \x11proto-core-dev libx11-dev:i386 libreadline6-dev:i386 libgl1-mesa-glx:i386 libgl1-mesa-dev g++-multilib \mingw32 tofrodos python-markdown libxml2-utils xsltproc zlib1g-dev:i386 $ sudo ln -s /usr/lib/i386-linux-gnu-mesa-libGL.so.1 /usr/lib/i386-linux-gnu/libGL.so

$ mkdir ~/bin$ PATH=~/bin:$PATH$ curl http://commondatastorage.googleapis.com/git-repo-downloads/repo > ~/bin/repo$ chmod a+x ~/bin/repo

How to Setup AOSP (cont.) 3. Set up repo repository

4. Sync with server

5. Add GPG key

1. Copy the following key

2. Then press Ctrl+D

Source Android – Downloading and Building (cited Nov 26, 2013)

$ mkdir AOSP$ cd AOSP$ repo init -u https://android.googlesource.com/platform/manifest

$ repo sync

$ gpg --import

-----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v1.4.2.2 (GNU/Linux) mQGiBEnnWD4RBACt9/h4v9xnnGDou13y3dvOx6/t43LPPIxeJ8eX9WB+8LLuROSV lFhpHawsVAcFlmi7f7jdSRF+OvtZL9ShPKdLfwBJMNkU66/TZmPewS4m782ndtw7 8tR1cXb197Ob8kOfQB3A9yk2XZ4ei4ZC3i6wVdqHLRxABdncwu5hOF9KXwCgkxMD u4PVgChaAJzTYJ1EG+UYBIUEAJmfearb0qRAN7dEoff0FeXsEaUA6U90sEoVks0Z wNj96SA8BL+a1OoEUUfpMhiHyLuQSftxisJxTh+2QclzDviDyaTrkANjdYY7p2cq /HMdOY7LJlHaqtXmZxXjjtw5Uc2QG8UY8aziU3IE9nTjSwCXeJnuyvoizl9/I1S5 jU5SA/9WwIps4SC84ielIXiGWEqq6i6/sk4I9q1YemZF2XVVKnmI1F4iCMtNKsR4 MGSa1gA8s4iQbsKNWPgp7M3a51JCVCu6l/8zTpA+uUGapw4tWCp4o0dpIvDPBEa9 b/aF/ygcR8mh5hgUfpF9IpXdknOsbKCvM9lSSfRciETykZc4wrRCVGhlIEFuZHJv aWQgT3BlbiBTb3VyY2UgUHJvamVjdCA8aW5pdGlhbC1jb250cmlidXRpb25AYW5k cm9pZC5jb20+iGAEExECACAFAknnWD4CGwMGCwkIBwMCBBUCCAMEFgIDAQIeAQIX gAAKCRDorT+BmrEOeNr+AJ42Xy6tEW7r3KzrJxnRX8mij9z8tgCdFfQYiHpYngkI 2t09Ed+9Bm4gmEO5Ag0ESedYRBAIAKVW1JcMBWvV/0Bo9WiByJ9WJ5swMN36/vAl QN4mWRhfzDOk/Rosdb0csAO/l8Kz0gKQPOfObtyYjvI8JMC3rmi+LIvSUT9806Up hisyEmmHv6U8gUb/xHLIanXGxwhYzjgeuAXVCsv+EvoPIHbY4L/KvP5x+oCJIDbk C2b1TvVk9PryzmE4BPIQL/NtgR1oLWm/uWR9zRUFtBnE411aMAN3qnAHBBMZzKMX LWBGWE0znfRrnczI5p49i2YZJAjyX1P2WzmScK49CV82dzLo71MnrF6fj+Udtb5+ OgTg7Cow+8PRaTkJEW5Y2JIZpnRUq0CYxAmHYX79EMKHDSThf/8AAwUIAJPWsB/M pK+KMs/s3r6nJrnYLTfdZhtmQXimpoDMJg1zxmL8UfNUKiQZ6esoAWtDgpqt7Y7s KZ8laHRARonte394hidZzM5nb6hQvpPjt2OlPRsyqVxw4c/KsjADtAuKW9/d8phb N8bTyOJo856qg4oOEzKG9eeF7oaZTYBy33BTL0408sEBxiMior6b8LrZrAhkqDjA vUXRwm/fFKgpsOysxC6xi553CxBUCH2omNV6Ka1LNMwzSp9ILz8jEGqmUtkBszwo G1S8fXgE0Lq3cdDM/GJ4QXP/p6LiwNF99faDMTV3+2SAOGvytOX6KjKVzKOSsfJQ hN0DlsIw8hqJc0WISQQYEQIACQUCSedYRAIbDAAKCRDorT+BmrEOeCUOAJ9qmR0l EXzeoxcdoafxqf6gZlJZlACgkWF7wi2YLW3Oa+jv2QSTlrx4KLM= =Wi5D -----END PGP PUBLIC KEY BLOCK-----

How to Setup AOSP (cont. 2) 5. Setup AOSP environment

6. Select Target build

** Example of building full options for generic ARM target

-jN flag specifies N jobs to run simultaneously = Many cores processors benefit from it

Source Android – Downloading and Building (cited Nov 26, 2013)

$ . build/envsetup.sh

$ lunch

$ . build/envsetup.sh

$ lunch full-eng

$ make -j8

Installing Oracle JDK6 Download JDK6 from Oracle Execute the downloaded bin file = File extract Make a directory for it

sudo mkdir /usr/lib/jvm

Copy the extracted files to that directory sudo mv jdk-1.6.0_xx /usr/lib/jvm/jdk-1.6.0_xx

Add Java alternatives sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk-1.6.0_xx/bin/javac 1 sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk-1.6.0_xx/bin/java 1 sudo update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk-1.6.0_xx/bin/javaws 1

Update Java alternatives sudo update-alternatives --config javac sudo update-alternatives --config java sudo update-alternatives --config javaws

Enable Java plugin for Mozilla Firefox and Google Chrome 64-bit: sudo ln -s /usr/lib/jvm-1.6.0_xx/jre/lib/amd64/libnpjp2.so /usr/lib/mozilla/plugins 32-bit: sudo ln -s /usr/lib/jvm-1.6.0_xx/jre/lib/i386/libnpjp2.so /usr/lib/mozilla/plugins

dev sniper – Ubuntu 12.04 – install sun jdk 6-7 (cited Nov 26, 2013)