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QEMU in

Cross Building

Tetsuyuki Kobayashi

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Who am I?

20+ years involved in embedded systems 10 years in real time OS, such as iTRON 10 years in embedded Java Virtual Machine Now Gcc, Linux, QEMU, Android, …

Blogs http://d.hatena.ne.jp/embedded/ (Personal) http://blog.kmckk.com/ (Corporate)

Twitter @tetsu_koba

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Today's topic

About QEMU Native build vs Cross build Easy but too slow: building on

system emulator Fast but too complex:

Scratchbox Just simple : building on user

mode QEMU

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Today's topic

About QEMU Native build vs Cross build Easy but too slow: building on

system emulator Fast but too complex:

Scratchbox Just simple : building on user

mode QEMU

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About QEMU

http://wiki.qemu.org/ QEMU is

a generic and open source machine emulatorand virtualizer.

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QEMU is used …

As virtualizer, KVM Xen VirtualBox

Host CPU == Target CPU Today I don't focus on this.

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QEMU is used …

As a system emulator, Host CPU != Target CPU Many open source projects such as:

Android Maemo Symbian ARM port of Open Solaris ...

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QEMU has …

Virtual disk. Many of virtual devices. Tiny Code Generator (TCG) to execute fast. Port redirector, Virtual network card. Bootloader to boot Linux kernel. gdbserver to connect gdb. …

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User mode QEMU

Emulate only user mode of linux. Not all system calls implemented,

but enough for building.

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Today's topic

About QEMU Native build vs Cross build Easy but too slow: building on

system emulator Fast but too complex:

Scratchbox Just simple : building on user

mode QEMU

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Native build vs Cross build

Native build – compile and run on the same machine.

Cross build – compile and run on the different arch machine. Embedded system does not have enough

CPU and memory for native building.

Configure problem

In many open source project

$ configure$ make$ make install

This suppose to be native build. Configure generate many small programand compile and run to check environment.

This does not work on cross build.

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Today's topic

About QEMU Native build vs Cross build Easy but too slow: building on

system emulator Fast but too complex:

Scratchbox Just simple : building on user

mode QEMU

Building on system QEMU

Apt-get works. Very easy to install compilers and libraries

Too slow to compile Emulating the whole system including kernel. Cannot take advantage of SMP becase

QEMU runs on single thread.

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Today's topic

About QEMU Native build vs Cross build Easy but too slow: building on

system emulator Fast but too complex:

Scratchbox Just simple : building on user

mode QEMU

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ScratchBox

Magical environment for cross building

running ARM executable using user mode QEMU

invoking the cross compiler on native

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ScratchBox 1

http://www.scratchbox.org/ Maemo project on Nokia mechanism

chroot binfmt_misc scratch-box-aware tool chains

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ScratchBox 2

http://www.freedesktop.org/wiki/Software/sbox2 Another implementation of scratch box Tool chain agnostic Hosted by Freedesktop.org mechanism

Wrap libc by PRELOAD magic of ld.so Hook system calls Insert QEMU when exec target binary Path name translation by LUA script

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ScratchBox* is

Pretty fast to compile Very hard to customize and

troubleshooting

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Today's topic

About QEMU Native build vs Cross build Easy but too slow: building on

system emulator Fast but too complex:

Scratchbox Just simple : building on user

mode QEMU

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Let's try simpler way

Just use user mode QEMU Use chroot and binfmt_misc Compiler running on QEMU, too

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binfmt_misc

Mechanism to execute foreign executable. ex) Used in Wine for dos executable. $ cat /proc/sys/fs/binfmt_misc/qemu-arm

enabledinterpreter /usr/bin/qemu-arm-staticflags: OCoffset 0magic 7f454c4601010100000000000000000002002800mask ffffffffffffff00fffffffffffffffffeffffff$

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Chroot

Make dedicated directory tree Used for public ftp server to make

sand box

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Static linked QEMU

Nice idea to avoid conflict in chrooted target root file system Dynamically linked QEMU needs so many library

files, which are likey conflict file names to target ones.

Static linked QEMU is stand alone. Just copy one file to target root file system.

I found this idea in rootstock script in Ubuntu

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Just Try

Make arm root file system by rootstock on Ubuntu 10.04

$ sudo apt-get install rootstock$ mkdir arm-ubuntu$ cd arm-ubuntu/$ sudo rootstock --fqdn arm-lucid --login user --password user

$ mkdir root$ cd root$ sudo tar xvf ../armel-rootfs-201005031740.tgz

It takes more than 10 minutes ...

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Just Try

$ lsbin dev home lost+found mnt proc sbin srv tmp varboot etc lib media opt root selinux sys usr$ uname -mx86_64

$ sudo chroot . /bin/bash## uname -marmv7l

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Build time comparison

80min (on system QEMU) 8min (user mode QEMU, make -j4) http://blog.kmckk.com/archives/2342452.html

Not yet try on scratchbox.It would be faster if I could.

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/proc

ps command fails

Don't worry. Mount /proc

# psCannot find /proc/version - is /proc mounted?

# mount proc /proc -t proc# ps PID TTY TIME CMD15434 ? 00:00:00 bash15440 ? 00:00:00 ps#

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Networking

Failed to resolve name OK, just add ip address to /etc/hosts# cat /etc/hosts127.0.0.1 localhost ubuntu1004127.0.1.1 arm-lucid91.189.88.36 ports.ubuntu.com

Then apt-get works. So far, it's enough.

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Distcc http://code.google.com/p/distcc/ Preprocessing and linking locally. Compiling and assembling remotely. Invoke cross compiler remotely. Distcc will enhance build time.

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Q & A

& Demo

Thank you for listening!Any comments to blogs are welcome.