QEMU in Cross building
4 likes3,379 views
The document discusses building software for embedded systems across different architectures using QEMU. It describes native building versus cross building, and compares building directly on a system emulator versus Scratchbox. It proposes that a simpler approach is to use just the user mode of QEMU, along with chroot and binfmt_misc. An example is given of setting up a basic ARM chroot environment and building software faster using user mode QEMU instead of a full system emulator. Issues like mounting proc and networking are also addressed.
QEMU in Cross building
- 1. QEMU in Cross Building Tetsuyuki Kobayashi 1
- 2. 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 2
- 3. 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 3
- 4. 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 4
- 5. About QEMU http://wiki.qemu.org/ QEMU is a generic and open source machine emulator and virtualizer. 5
- 6. QEMU is used … As virtualizer, KVM Xen VirtualBox Host CPU == Target CPU Today I don't focus on this. 6
- 7. 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 ... 7
- 8. 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. … 8
- 9. User mode QEMU Emulate only user mode of linux. Not all system calls implemented, but enough for building. 9
- 10. 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 10
- 11. 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. 11
- 12. Configure problem In many open source project $ configure $ make $ make install This suppose to be native build. Configure generate many small program and compile and run to check environment. This does not work on cross build.
- 13. 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 13
- 14. 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.
- 15. 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 15
- 16. ScratchBox Magical environment for cross building running ARM executable using user mode QEMU invoking the cross compiler on native 16
- 17. ScratchBox 1 http://www.scratchbox.org/ Maemo project on Nokia mechanism chroot binfmt_misc scratch-box-aware tool chains 17
- 18. 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 18
- 19. ScratchBox* is Pretty fast to compile Very hard to customize and troubleshooting 19
- 20. 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 20
- 21. Let's try simpler way Just use user mode QEMU Use chroot and binfmt_misc Compiler running on QEMU, too 21
- 22. binfmt_misc Mechanism to execute foreign executable. ex) Used in Wine for dos executable. $ cat /proc/sys/fs/binfmt_misc/qemu-arm enabled interpreter /usr/bin/qemu-arm-static flags: OC offset 0 magic 7f454c4601010100000000000000000002002800 mask ffffffffffffff00fffffffffffffffffeffffff $ 22
- 23. Chroot Make dedicated directory tree Used for public ftp server to make sand box 23
- 24. 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 24
- 25. 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 It takes more than 10 minutes ... $ mkdir root $ cd root $ sudo tar xvf ../armel-rootfs-201005031740.tgz 25
- 26. Just Try $ ls bin dev home lost+found mnt proc sbin srv tmp var boot etc lib media opt root selinux sys usr $ uname -m x86_64 $ sudo chroot . /bin/bash # # uname -m armv7l 26
- 27. 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. 27
- 28. /proc ps command fails # ps Cannot find /proc/version - is /proc mounted? Don't worry. Mount /proc # mount proc /proc -t proc # ps PID TTY TIME CMD 15434 ? 00:00:00 bash 15440 ? 00:00:00 ps # 28
- 29. Networking Failed to resolve name OK, just add ip address to /etc/hosts # cat /etc/hosts 127.0.0.1 localhost ubuntu1004 127.0.1.1 arm-lucid 91.189.88.36 ports.ubuntu.com Then apt-get works. So far, it's enough. 29
- 30. Distcc http://code.google.com/p/distcc/ Preprocessing and linking locally. Compiling and assembling remotely. Invoke cross compiler remotely. Distcc will enhance build time. 30
- 31. Q&A & Demo Thank you for listening! Any comments to blogs are welcome. 31