On the #uploadfilter problem

The copyright holders in europe are pushing hard mandate upload filters for internet. We have been here before - when they outlawed circumventing DRM. Both have roots in the same problem. The copyright holders look at computers and see bad things happening to their revenue. They come to IT companies and say "FIX IT". It industry comes back and says.. "We cant.. making data impossible to copy is like trying to make water not wet!". But we fail at convincing copyright holders in how perfect DRM or upload filter is not possible. Then copyright holders go to law makers and ask them in turn to fix it.

We need to turn tables around. If they want something impossible, it should be upto them to implement it.

It is simply unfair to require each online provider to implement an AI to detect copyright infringement, manage a database of copyrighted content and pay for the costs running it all.. ..And getting slapped with a lawsuit anyways, since copyrighted content is still slipping through.

The burden of implementing #uploadfilter should be on the copyright holder organizations. Implement as a SaaS. Youtube other web platforms call your API and pay $0.01 each time a pirate content is detected. On the other side, to ensure correctness of the filter, copyright holders have to pay any lost revenue, court costs and so on for each false positive.

Filtering uploads is still problematic. But it's now the copyright holders problem. Instead people blaming web companies for poor filters, it's the copyright holders now who have to answer to the public why their filters are rejecting content that doesn't belong to them.

Making sense of /proc/cpuinfo on ARM

Ever stared at output of /proc/cpuinfo and wondered what the CPU is?

...
processor       : 7
BogoMIPS        : 2.40
Features        : fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd03
CPU revision    : 3

Or maybe like:

$ cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 2 (v7l)
BogoMIPS        : 50.00
Features        : half thumb fastmult vfp edsp thumbee vfpv3 tls idiva idivt vfpd32 lpae
CPU implementer : 0x56
CPU architecture: 7
CPU variant     : 0x2
CPU part        : 0x584
CPU revision    : 2
...

The bits "CPU implementer" and "CPU part" could be mapped to human understandable strings. But the Kernel developers are heavily against the idea. Therefor, to the next idea: Parse in userspace. Turns out, there is a common tool almost everyone has installed does similar stuff. lscpu(1) from util-linux. So I proposed a patch to do ID mapping on arm/arm64 to util-linux, and it was accepted! So using lscpu from util-linux 2.32 (hopefully to be released soon) the above two systems look like:

Architecture:        aarch64
Byte Order:          Little Endian
CPU(s):              8
On-line CPU(s) list: 0-7
Thread(s) per core:  1
Core(s) per socket:  4
Socket(s):           2
NUMA node(s):        1
Vendor ID:           ARM
Model:               3
Model name:          Cortex-A53
Stepping:            r0p3
CPU max MHz:         1200.0000
CPU min MHz:         208.0000
BogoMIPS:            2.40
L1d cache:           unknown size
L1i cache:           unknown size
L2 cache:            unknown size
NUMA node0 CPU(s):   0-7
Flags:               fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid

And

$ lscpu
Architecture:        armv7l
Byte Order:          Little Endian
CPU(s):              4
On-line CPU(s) list: 0-3
Thread(s) per core:  1
Core(s) per socket:  4
Socket(s):           1
Vendor ID:           Marvell
Model:               2
Model name:          PJ4B-MP
Stepping:            0x2
CPU max MHz:         1333.0000
CPU min MHz:         666.5000
BogoMIPS:            50.00
Flags:               half thumb fastmult vfp edsp thumbee vfpv3 tls idiva idivt vfpd32 lpae

As we can see, lscpu is quite versatile and can show more information than just what is available in cpuinfo.

Cross-compiling with debian stretch

Debian stretch comes with cross-compiler packages for selected architectures:

 $ apt-cache search cross-build-essential
crossbuild-essential-arm64 - Informational list of cross-build-essential packages for
crossbuild-essential-armel - ...
crossbuild-essential-armhf - ...
crossbuild-essential-mipsel - ...
crossbuild-essential-powerpc - ...
crossbuild-essential-ppc64el - ...
⏎                                                                                       

Lets have a quick exact steps guide. But first - while you can use do all this in your desktop PC rootfs, it is more wise to contain yourself. Fortunately, Debian comes with a container tool out of box:

sudo debootstrap stretch /var/lib/container/stretch http://deb.debian.org/debian
echo "strech_cross" | sudo tee /var/lib/container/stretch/etc/debian_chroot
sudo systemd-nspawn -D /var/lib/container/stretch

Then we set up cross-building enviroment for arm64 inside the container:

# Tell dpkg we can install arm64
dpkg --add-architecture arm64
# Add src line to make "apt-get source" work
echo "deb-src http://deb.debian.org/debian stretch main" >> /etc/apt/sources.list
apt-get update
# Install cross-compiler and other essential build tools
apt install --no-install-recommends build-essential crossbuild-essential-arm64

Now we have a nice build enviroment, lets choose something more complicated than the usual kernel/BusyBox to cross-build, qemu:

# Get qemu sources from debian
apt-get source qemu
cd qemu-*
# New in stretch: build-dep works in unpacked source tree 
apt-get build-dep -a arm64 .
# Cross-build Qemu for arm64
dpkg-buildpackage -aarm64 -j6 -b

Now that works perfectly for Qemu. For other packages, challenges may appear. For example you may have to se "nocheck" flag to skip build-time unit tests. Or some of the build-dependencies may not be multiarch-enabled. So work continues :)

Deploying OBS

Open Build Service from SuSE is web service building deb/rpm packages. It has recently been added to Debian, so finally there is relatively easy way to set up PPA style repositories in Debian. Relative as in "there is a learning curve, but nowhere near the complexity of replicating Debian's internal infrastructure". OBS will give you both repositories and build infrastructure with a clickety web UI and command line client (osc) to manage. See Hectors blog for quickstart instructions.

Things to learned while setting up OBS

Me coming from Debian background, and OBS coming from SuSE/RPM world, there are some quirks that can take by surprise.

Well done packaging

Usually web services are a tough fit for Distros. The cascade of weird dependencies and build systems where the only practical way to build an "open source" web service is by replicating the upstream CI scripts. Not in case of OBS. Being done by distro people shows.

OBS does automatic rebuilds of reverse dependencies

Aka automatic binNMUs when you update a library. This however means you need lots of build power around. OBS has it's own dependency resolver on the server that recalculate what packages need rebuilding when - workers just get a list of packages to install for build-depends. This a major divergence from Debian, where sbuild handles dependencies client side. The OBS dependency handler doesn't handle virtual packages* / alternative build-deps like Debian - you may have to add a specific "Prefer: foo-dev" into the OBS project config to solve alternative choices.

OBS server and worker do http requests in both directions

On startup workers connect to OBS server, open a TCP port and wait requests coming OBS. Having connections both directions is a bit of hassle firewall-wise. On the bright side, no need to setup uploads via FTP here..

Signing repositories is complicated

With Debian 9.0 making signed repositories pretty much mandatory, OBS makes signing rather complicated. obs-signd isn't included in Debian, since it depends on gnupg patch that hasn't been upstreamed. Fortunately I found a workaround. OBS signs release files with /usr/bin/sign -d /path/to/release. Where replacing the obs-signd provided sign command your own script is easy ;)

Git integration is rather bolted-on than integrated

OBS provides a method to integrate with git using services. - There is no clickety UI to link to git repo, instead you make an xml file called _service with osc. There is no way to have debian/ tree in git.

The upstream community is friendly

Including the happiest thanks from an upstream I've seen recently.

Summary

All in all rather satisfied with OBS. If you have a home-grown jenkins etc based solution for building DEB/RPM packages, you should definitely consider OBS. For simpler uses, no need to install OBS yourself, openSUSE public OBS will happily build Debian packages for you.

*How useful are virtual packages anymore? "foo-defaults" packages seem to be the go-to solution for most real usecases anyways.

Booting ubuntu 16.04 cloud images on Arm64

For testing kvm/qemu, prebaked images cloud images are nice. However, there is a few steps to get started. First we need a recent Qemu (2.5 is good enough). An efi firmware is needed, and cloud-utils, for customizing our VM.

sudo apt install -y qemu qemu-utils cloud-utils
wget https://releases.linaro.org/components/kernel/uefi-linaro/15.12/release/qemu64/QEMU_EFI.fd
wget https://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-arm64-uefi1.img

Cloud images are plain - there is no user setup, no default user/pw combo, so to log in to the image, we need to customize the image on first boot. The defacto tool for this is cloud-init. The simplest method for using cloud-init is passing a block media with a settings file - of course for real cloud deployment, you would use one of fancy network based initialization protocols cloud-init supports. Enter the following to a file, say cloud.txt:

#cloud-config

users:
  - name: you
    ssh-authorized-keys:
      - ssh-rsa AAAAB3Nz....
    sudo: ['ALL=(ALL) NOPASSWD:ALL']
    groups: sudo
    shell: /bin/bash

This minimal config will just set you a user with ssh key. A more complex setup can install packages, write files and run arbitrary commands on first boot. In professional setups, you would most likely end up using cloud-init only to start Ansible or another configuration management tool.

cloud-localds cloud.img cloud.txt
qemu-system-aarch64 -smp 2 -m 1024 -M virt -bios QEMU_EFI.fd -nographic \
       -device virtio-blk-device,drive=image \
       -drive if=none,id=image,file=xenial-server-cloudimg-arm64-uefi1.img \
       -device virtio-blk-device,drive=cloud \
       -drive if=none,id=cloud,file=cloud.img \
       -netdev user,id=user0 -device virtio-net-device,netdev=user0 -redir tcp:2222::22 \
       -enable-kvm -cpu host 

If you are on an X86 host and want to use qemu to run an aarch64 image, replace the last line with "-cpu cortex-a57". Now, since the example uses user networking with tcp port redirect, you can ssh into the VM:

ssh -p 2222 you@localhost
Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-22-generic aarch64)
....

Ancient Linux swag

Since I've now been using Linux for 20 years, I've dug up some artifacts from the early journey.

1. First the book, from late 1995. This from before Tux, so the penguin in the cover is just a co-incidence. The book came with a slackware 3.0 CD, which was my entrance to Linux. Today, almost all of the book is outdated - slackware and lilo install? printing with lpr? mtools and dosemu? ftp, telnet with SLIP dialup? Manually configuring XFree86 and fvwm? How I miss those times!* The only parts of the book are still valid are: shell and vi guides. I didn't read latter, and instead imported my favorite editor from dos FTE.
2. Fast forward some years, into my first programming job. Ready to advertise the Linux revolution, I bought the mug on right. Nobody else would have a Tux mug, so nobody would accidentally take my mug from the office dishwasher. That only worked for my first work place (a huge and nationally hated IT consultant house). The next workplace, a mobile gaming startup (in 2001, I was there before it was trendy!) - and there was already plenty of Linux mugs when I joined...
3. While today it may be hard to imagine, those days using Microsoft office tools was mandatory. That leads to the third memorabilia in the picture. Wordperfect for Linux existed for a brief while, and in the box (can you imagine, software came in physical boxes?) came a Tux plush.

* Wait no, I don't miss those times at all

Using ser2net for serial access.

Is your table a mess of wires? Do you have multiple devices connected via serial and can't remember which is /dev/ttyUSBX is connected to what board? Unless you are a embedded developer, you are unlikely to deal with serial much anymore - In that case you can just jump to the next post in your news feed.

Introducting ser2net

Usually people start with minicom for serial access. There are better tools - picocom, screen, etc. But to easily map multiple serial ports, use ser2net. Ser2net makes serial ports available over telnet.

Persistent usb device names and ser2net

To remember which usb-serial adapter is connected to what, we use the /dev/serial tree created by udev, in /etc/ser2net.conf:

# arndale
7004:telnet:0:'/dev/serial/by-path/pci-0000:00:1d.0-usb-0:1.8.1:1.0-port0':115200 8DATABITS NONE 1STOPBIT
# cubox
7005:telnet:0:/dev/serial/by-id/usb-Prolific_Technology_Inc._USB-Serial_Controller_D-if00-port0:115200 8DATABITS NONE 1STOPBIT
# sonic-screwdriver
7006:telnet:0:/dev/serial/by-id/usb-FTDI_FT230X_96Boards_Console_DAZ0KA02-if00-port0:115200 8DATABITS NONE 1STOPBIT

The by-path syntax is needed, if you have many identical usb-to-serial adapters. In that case a Patch from BTS is needed to support quoting in serial path. Ser2net doesn't seems very actively maintained upstream - a sure sign that project is stagnant is a homepage still at sourceforge.net... This patch among other interesting features can be also be found in various ser2net forks in github.

Setting easy to remember names

Finally, unless you want to memorize the port numbers, set TCP port to name mappings in /etc/services:

# Local services
arndale            7004/tcp
cubox              7005/tcp
sonic-screwdriver  7006/tcp

Now finally:

telnet localhost sonic-screwdriver

^Mandatory picture of serial port connection in action

Migration to Scaleway ARM server

The C1 Server

Scaleway started selling ARM based hosted server in April. I've intended to blog about this for a while, since it was time to upgrade from wheezy to jessie was timely, why not switch provider from an X86 based to ARM one at the same time?

In many ways scaleway node is opposite to what "Enterprise ARM" people are working on. Each server is based on an oldish ARMv7 Quad-Core Marvell Armada XP, instead of a brand new 64-bit ARMv8 cpu. There is no UEFI, ACPI or any other "industry standards" involved, just a smooth web interface and a command line tool to manage your node(s). And the node is yours, it's not shared with others with virtualization. The picture above is a single node, which is stacked with 911 other nodes into a single rack.

This week, the C1 price was dropped to a very reasonable €2.99 per month, or €0.006 per hour.

Software runs on hardware, news at 11

The performance is more than enough for my needs - shell, email and light web serving. dovecot, postfix, irssi and apache2 are just an apt-get away. Anyone who says you need x86 for Linux servers is forgetting that Linux software is open source, and if not already available, can be compiled to any architecture with little effort. Thus the migration pains were only because I chose to modernize configuration of dovecot and friends. Details of the new setup shall be left for another post.

Fastest way to change running dtb

Tollef posted about using BeagleBone Black for temperature monitoring. There was a passage about patching the DTB (device tree) file:

... This needs to be compiled into a .dtb. I found the easiest way was just to drop the patched .dts into an unpacked kernel tree and then running make dtbs.

There are easier ways. For example, you can get the current device tree file generated from /proc:

apt-get install device-tree-compiler
dtc -I fs -O dts -o current.dts /proc/device-tree/

(Why /proc and not /sys ? because device tree predates /sys) Now you can just modify and build the dtb again, and install it back to where bootloader reads the dtb from:

vim current.dts
dtc -I dts -O dtb -o new.dtb current.dts

Alternative, of course, is to build a brand new mainline kernel and use the dynamic Device tree code now available.

Crowdfunding better GCompris graphics

GCompris is the most established open source kids educational game. Here we practice use of mouse with an Efika smartbook. In this subgame, mouse is moved around to uncover a image behind.

While GCompris is nice, it needs nice graphics badly. Now the GCompris authors are running a indiegogo crowfund exactly for that - to get new unified graphics.

Why should you fund? Apart from the "I want to be nice for any oss project", I see a couple of reasons specific for this crowdfund.

First, to show kids that apps can be changed! Instead of just using existing iPad apps as a consumer, Gcompris allows you to show kids how games are built and modified. With the new graphics, more kids will play longer, and eventually some will ask if something can be changed/added..

Second, GCompris has recently become QT/QML based, making it more portable than before. Wouldn't you like to see it in your Jolla tablet or a future Ubuntu phone? The crowfund doesn't promise to make new ports, but if you are eager to show your friends nice looking apps on your platform, this probably one of the easiest ways to help them happen.

Finally, as a nice way to say happy new year 2015 :)

Adventures in setting up local lava service

Linaro uses LAVA as a tool to test variety of devices. So far I had not installed it myself, mostly due to assuming it to be enermously complex to set up. But thanks to Neil Williams work on packaging, installation has got a lot easier. Follow the Official Install Doc and Official install to debian Doc, roughly looking like:

1. Install Jessie into kvm

kvm -m 2048 -drive file=lava2.img,if=virtio -cdrom debian-testing-amd64-netinst.iso

2. Install lava-server

apt-get update; apt-get install -y postgresql nfs-kernel-server apache2
apt-get install lava-server
# answer debconf questions
a2dissite 000-default && a2ensite lava-server.conf 
service apache2 reload
lava-server manage createsuperuser --username default --email=foo.bar@example.com
$EDITOR /etc/lava-dispatcher/lava-dispatcher.conf # make sure LAVA_SERVER_IP is right

That's the generic setup. Now you can point your browser to the IP address of the kvm machine, and log in with the default user and the password you made.

3 ... 1000 Each LAVA instance is site customized for the boards, network, serial ports, etc. In this example, I now add a single arndale board.

cp /usr/lib/python2.7/dist-packages/lava_dispatcher/default-config/lava-dispatcher/device-types/arndale.conf /etc/lava-dispatcher/device-types/
sudo /usr/share/lava-server/add_device.py -s arndale arndale-01 -t 7001

This generates us a almost usable config for the arndale. For site specifics I have usb-to-serial. Outside kvm, I provide access to serial ports using the following ser2net config:

7001:telnet:0:/dev/ttyUSB0:115200 8DATABITS NONE 1STOPBIT
7002:telnet:0:/dev/ttyUSB1:115200 8DATABITS NONE 1STOPBIT

TODO: make ser2net not run as root and ensure usb2serial devices always get same name..

For automatic power reset, I wanted something cheap, yet something that wouldn't require much soldering (I'm not a real embedded engineer.. I prefer software side ;) . Discussed with Hector, who hinted about prebuilt relay boxes. Chose one from Ebay, a kmtronic 8-port USB Relay. So now I have this cute boxed nonsense hack.

The USB relay is driven with a short script, hard-reset-1

stty -F /dev/ttyACM0 9600
echo -e '\xFF\x01\x00' > /dev/ttyACM0
sleep 1
echo -e '\xFF\x01\x01' > /dev/ttyACM0

Sidenote: If you don't have or want automated power relay for lava, you can always replace this this script with something along "mpg123 puny_human_press_the_power_button_now.mp3"

Both the serial port and reset script are on server with dns name aimless. So we take the /etc/lava-dispatcher/devices/arndale-01.conf that add_device.py created and make it look like:

device_type = arndale
hostname = arndale-01
connection_command = telnet aimless 7001
hard_reset_command = slogin lava@aimless -i /etc/lava-dispatcher/id_rsa /home/lava/hard-reset-1

Since in my case I'm only going to test with tftp/nfs boot, the arndale board needs only to be setup to have a u-boot bootloader ready on power-on.

Now everything is ready for a test job. I have a locally built kernel and device tree, and I export the directory using the httpd available by default in debian.. Python!

cd out/
python -m SimpleHTTPServer

Go to the lava web server, select api->tokens and create a new token. Next we add the token and use it to submit a job

$ sudo apt-get install lava-tool
$ lava-tool auth-add http://default@lava-server/RPC2/
$ lava-tool submit-job http://default@lava-server/RPC2/ lava_test.json
submitted as job id: 1
$

The first job should now be visible in the lava web frontend, in the scheduler -> jobs part. If everything goes fine, the relay will click in a moment and the job will finish in a few minutes.

Using networkd for kvm tap networking

Setting up basic systemd-network was recently described by Joachim, and the post inspired me to try it as well. The twist is that in my case I need a bridge for my KVM with Lava server and arm/aarch64 qemu system emulators...

For background, qemu/kvm support a few ways to provide network to guests. The default is user networking, which requires no privileges, but is slow and based on ancient SLIRP code. The other common option is tap networking, which is fast, but complicated to set up. Turns out, with networkd and qemu bridge helper, tap is easy to set up.

$ for file in /etc/systemd/network/*; do echo $file; cat $file; done
/etc/systemd/network/eth.network
[Match]
Name=eth1
[Network]
Bridge=br0

/etc/systemd/network/kvm.netdev
[NetDev]
Name=br0
Kind=bridge

/etc/systemd/network/kvm.network
[Match]
Name=br0
[Network]
DHCP=yes

Diverging from Joachims simple example, we replaced "DHCP=yes" with "Bridge=br0". Then we proceed to define the bridge (in the kvm.netdev) and give it an ip via dhcp in kvm.network. From the kvm side, if you haven't used the bridge helper before, you need to give the helper permissions (setuid root or cap_net_admin) to create a tap device to attach on the bridge. The helper needs an configuration file to tell what bridge it may meddle with.

# cat > /etc/qemu/bridge.conf <<__END__
allow br0
__END__
# setcap cap_net_admin=ep /usr/lib/qemu/qemu-bridge-helper

Now we can start kvm with bridge networking as easily as with user networking:

$ kvm -m 2048 -drive file=jessie.img,if=virtio -net bridge -net nic,model=virtio -serial stdio

The manpages systemd.network(5) and systemd.netdev(5) do a great job explaining the files. Qemu/kvm networking docs are unfortunately not as detailed.

Booting Linaro ARMv8 OE images with Qemu

A quick update - Linaro ARMv8 OpenEmbbeded images work just fine with qemu 2.1 as well:

$ http://releases.linaro.org/14.07/openembedded/aarch64/Image
$ http://releases.linaro.org/14.07/openembedded/aarch64/vexpress64-openembedded_lamp-armv8-gcc-4.9_20140727-682.img.gz
$ qemu-system-aarch64 -m 1024 -cpu cortex-a57 -nographic -machine virt \
 -kernel Image -append 'root=/dev/vda2 rw rootwait mem=1024M console=ttyAMA0,38400n8' \
 -drive if=none,id=image,file=vexpress64-openembedded_lamp-armv8-gcc-4.9_20140727-682.img \
 -netdev user,id=user0 -device virtio-net-device,netdev=user0  -device virtio-blk-device,drive=image 
[    0.000000] Linux version 3.16.0-1-linaro-vexpress64 (buildslave@x86-64-07) (gcc version 4.8.3 20140401 (prerelease) (crosstool-NG linaro-1.13.1-4.8-2014.04 - Linaro GCC 4.8-2014.04) ) #1ubuntu1~ci+140726114341 SMP PREEMPT Sat Jul 26 11:44:27 UTC 20
[    0.000000] CPU: AArch64 Processor [411fd070] revision 0
...
root@genericarmv8:~# 

Quick benchmarking with age-old ByteMark nbench:

Index	Qemu	Foundation	Host
Memory	4.294	0.712	44.534
Integer	6.270	0.686	41.983
Float	1.463	1.065	59.528
Baseline (LINUX) : AMD K6/233*

Qemu is upto 8x faster than Foundation model on Integers, but only 50% faster on Math. Meanwhile, the Host pc spends 7-40x slower emulating ARMv8 than executing native instructions.

Testing qemu 2.1 arm64 support

Qemu 2.1 was just released a few days ago, and is now a available on Debian/unstable. Trying out an (virtual) arm64 machine is now just a few steps away for unstable users:

$ sudo apt-get install qemu-system-arm 
$ wget https://cloud-images.ubuntu.com/trusty/current/trusty-server-cloudimg-arm64-disk1.img
$ wget https://cloud-images.ubuntu.com/trusty/current/unpacked/trusty-server-cloudimg-arm64-vmlinuz-generic
$ qemu-system-aarch64 -m 1024 -cpu cortex-a57 -nographic -machine virt -kernel trusty-server-cloudimg-arm64-vmlinuz-generic \ 
-append 'root=/dev/vda1 rw rootwait mem=1024M console=ttyAMA0,38400n8 init=/usr/lib/cloud-init/uncloud-init ds=nocloud ubuntu-pass=randomstring' \
-drive if=none,id=image,file=trusty-server-cloudimg-arm64-disk1.img \
-netdev user,id=user0 -device virtio-net-device,netdev=user0 -device virtio-blk-device,drive=image 
[    0.000000] Linux version 3.13.0-32-generic (buildd@beebe) (gcc version 4.8.2 (Ubuntu/Linaro 4.8.2-19ubuntu1) ) #57-Ubuntu SMP Tue Jul 15 03:52:14 UTC 2014 (Ubuntu 3.13.0-32.57-generic 3.13.11.4)
[    0.000000] CPU: AArch64 Processor [411fd070] revision 0
...
-snip-
...
ubuntu@ubuntu:~$ cat /proc/cpuinfo 
Processor       : AArch64 Processor rev 0 (aarch64)
processor       : 0
Features        : fp asimd evtstrm 
CPU implementer : 0x41
CPU architecture: AArch64
CPU variant     : 0x1
CPU part        : 0xd07
CPU revision    : 0

Hardware        : linux,dummy-virt
ubuntu@ubuntu:~$

The "init=/usr/lib/cloud-init/uncloud-init ds=nocloud ubuntu-pass=randomstring" is ubuntu cloud stuff that will set the ubuntu user password to "randomstring" - don't use "randomstring" literally there, if you are connected to internets...

For more detailed writeup of using qemu-system-aarch64, check the excellent writeup from Alex Bennee.

Arm builder updates

Debian has recently received a donation of 8 build machines from Marvell. The new machines come with Quad core MV78460 Armada XP CPU's, DDR3 DIMM slot so we can plug in more memory, and speedy sata ports. They replace the well served Marvell MV78200 based builders - ones that have been building debian armel since 2009. We are planning a more detailed announcement, but I'll provide a quick summary:

The speed increase provided by MV78460 can viewed by comparing build times on selected builds since early april:

Qemu build times.

We can now build Qemu in 2h instead of 16h -8x faster than before! Certainly a substantial improvement, so impressive kit from Marvell! But not all packages gain this amount of speedup:

webkitgtk build times.

This example, webkitgtk, builds barely 3x faster. The explanation is found from debian/rules of webkitgkt:

# Parallel builds are unstable, see #714072 and #722520
# ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
#   NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
#   MAKEARGUMENTS += -j$(NUMJOBS)
# endif

The old builders are single-core[1], so the regardless of parallel building, you can easily max out the cpu. New builders will use only 1 of 4 cores without parallel build support in debian/rules.

During this buildd cpu usage graph, we see most time only one CPU is consumed. So for fast package build times.. make sure your packages supports parallel building.

For developers, abel.debian.org is porter machine with Armada XP. It has schroot's for both armel and armhf. set "DEB_BUILD_OPTIONS=parallel=4" and off you go.

Finally I'd like to thank Thomas Petazzoni, Maen Suleiman, Hector Oron, Steve McIntyre, Adam Conrad and Jon Ward for making the upgrade happen.

Meanwhile, we have unrelated trouble - a bunch of disks have broken within a few days apart. I take the warranty just run out...

[1] only from Linux's point of view. - mv78200 has actually 2 cores, just not SMP or coherent. You could run an RTOS on the other core while you run Linux on the other.

ACPI on ARM storm in teacup

A recent google+ post by Jon Masters caused some stormy and some less stormy responses.

A lot of BIOS/UEFI/ACPI hate comes X86, where ACPI is used from everything from suspending devices to reading buttons and setting leds. So when X86 kernel suspends, it does magic calls to ACPI and prays that the firmware vendor did not screw it up. Now vendors do screw up, hence lots of cursing and ugly workarounds in the kernel follows. My Lenovo has a firwmare bug where the FN-buttons and Fan stops working if the laptop is attached on AC adapter for too long. The fan is probably a simple i2c device the kernel could control directly without jumping through ACPI hiding layer hoops. But the X86 people hold the view it is better to trust the firmware engineer to control devices instead of having the kernel folk to write device drivers to ... control devices!

Now on ARM(64) the idea of using ACPI is to have none of that.

Instead the idea is to use ACPI only to provide tables for enumerating what devices are available in the platform. Just like what device tree does. Now if this is the same as device tree, why bother?

The main reason is to allow the distribution installer behave same on X86 / ARM / ARM64. This is crucial for distributions like fedora and RHEL where a cabal holds the point of view that X86 distribution development must not be constrained by ARM support. But it also important for everyone that the method of installing your favorite distribution to an ARM64 server is standard and works the same for any server from any vendor. Now while UEFI and ACPI are definitely not my preferred solutions, I can accept them as necessary evil for having a more standard platform.

On behalf of aarch64 porters

Public service announcement

When porting GNU/Linux applications to a new architecture, such as 64-Bit ARM, one gets familiar with the following error message:

checking build system type... x86_64-pc-linux-gnu
checking host system type... Invalid configuration `aarch64-oe-linux': machine `aarch64-oe' not recognized
configure: error: /bin/sh config.sub aarch64-oe-linux failed

This in itself is trivial to fix - run autoreconf or just copy in new versions of config.sub and config.guess. However, when bootstrapping a distribution of 12000+ packages, this becomes quickly tiresome. Thus we have a small request:

If you are an upstream of a software that uses autoconf - Please run autoreconf against autotools-dev 20120210.1 or later, and make a release of your software.

Aarch64 porters will be grateful as updated software trickles down to distributions.

This was the most discussed point during my FOSDEM talk "Porting applications to 64-Bit ARM".

Adventures in perlsembly

Some Debian packages are missing important optimizations. This one was noticed when comparing openssl benchmarks by monkeyiq to the results got on a pandaboard (OMAP 4430). Being a Cortex-A9, it should have clearly been same or faster than the N9 in the benchmark (OMAP 3630). And it was, except for AES benchmarks. Since AES is quite important, that seemed a bit odd. Turns out, that Debian/Ubuntu package had some hand-crafted arm assembler optimizations missing. Enable them, and the results with openssl speed command benchmark were quite nice:

The 'numbers' are in 1000s of bytes per second processed.

benchmark    debian       with patch +%
sha1         55836.67k -> 73599.08k +31.811%
aes-128 cbc  18451.11k -> 36305.34k +96.765%
aes-256 cbc  13552.30k -> 27108.31k +100.027%
sha256       20092.25k -> 43469.45k +116.349%
sha512       8052.74k  -> 37194.28k +361.884 %
rsa 1024     1904.2v/S -> 3650.5v/s +91.708 %

Curiously, the assembler code is actually in perl files that output assembler code. This kind of code is affectionately called "perlsembly". A bug with patch has been filed, hopefully applied at the soonest.

Mosh - better remote shell

In this age of 3d accelerated desktops and all that fancy stuff, one does not expect practical innovation happening in the remote terminal emulation area. But it has just happened. It is called Mosh, a shorthand for "Mobile Shell".

What does it do better than ssh we have learned to love?

• Less lag! Being UDP based, it is not prone to TCP congestion effects. Considering that voip, games and everything else latency critical has been UDP based, it is (almost) surprising that it wasn't done for interactive terminals before...
• Even less lag! Mosh provides local echo and line editing when the other side is not being responsive. To do this, mosh actually becomes a terminal emulator of it's own. This stuff is sweet on unstable 3G and conference wifi networks.
• Survives suspending. Resume your laptop and *bam* all your remote mutt and vim editors are still there instead of the "connection reset" you get from ssh.
• Roaming. Got another IP? Moved from wifi to ethernet to 3G? your sessions are still open! Another thing a TCP based protocol couldn't do easily...

It doesn't replace ssh, as it still borrows authentication from ssh. But that's cool, as you can keep your ssh authorized keys.

Available in Debian unstable,testing and Backports today, and many other systems as well. Hopefully an Android client comes available soon, as the above mentioned advantages seem really tailored for android like mobile systems.

Caveat: This is new stuff, and thus hasn't quite been proven to be secure.

Cross Compiling with MultiArch

Congrats to the Ubuntu Folk for the new LTS release. Incidentally this is also the first release where our work on MultiArch bears fruit. We can now cross-compile relatively easily without resorting to hacks like scratchbox, qemu chroot or dpkg-cross/xdeb.

Lets show short practical guide on cross-building Qemu for armhf. The instructions refer to precise, but the goodiness is on the way to Debian as well. Biggest missing piece being the cross-compiler packages, which we have an Summer of Code project. The example is operated in a chroot to avoid potentially messing up your working machine. Qemu-linaro is not a shining example, as cross-building it doesn't work out of box. But that is educational, it allows me to show what kind of issues you can bump into, and how to fix them.

 $ sudo debootstrap --variant=buildd precise /srv/precise

Edit the /srv/precise/etc/apt.sources.list to the following (replace amd64 with i386 if you made an i386 chroot)

deb [arch=amd64] http://archive.ubuntu.com/ubuntu precise main universe
deb [arch=armhf] http://ports.ubuntu.com/ubuntu-ports precise main universe
deb-src http://archive.ubuntu.com/ubuntu precise main universe

Edit the /srv/precise/etc/dpkg/dpkg.cfg.d/multiarch by adding the following line:

foreign-architecture armhf

Finally disable install of recommends by editing /srv/precise/etc/apt/apt.conf.d/10local:

APT::Install-Recommends "0";
APT::Install-Suggests "0";

Install the armhf crosscompiler the chroot

 $ sudo chroot /srv/precise/
 # unset LANG LANGUAGE
 # mount -t proc proc /proc
 # apt-get update
 # apt-get install g++-arm-linux-gnueabihf pkg-config-arm-linux-gnueabihf

Get the sources and try to install the cross-buildeps:

 # cd /tmp
 # apt-get source qemu-linaro
 # cd qemu-linaro-*
 # apt-get build-dep -aarmhf qemu-linaro

As we see, the build-dep bombs out ugly, with a them of "perl" being unable to be installed. This is because apt-get can't figure out if we should install and armhf or amd64 version of perl. We don't use the required syntax yet in Build-Dep line, "perl:any", as dpkg and apt in previous released don't support it. Thus back porting would no longer be possible. One way to fix it, would be to drop perl build-dep, as perl is already pulled by other build-deps. But lets instead show howto install it the build-deps manually. First we build system build-deps, then target architecture ones:

 # apt-get install debhelper texinfo
 # apt-get install zlib1g-dev:armhf libasound2-dev:armhf libsdl1.2-dev:armhf libx11-dev:armhf libpulse-dev:armhf libncurses5-dev:armhf libbrlapi-dev:armhf libcurl4-gnutls-dev:armhf libgnutls-dev:armhf libsasl2-dev:armhf uuid-dev:armhf libvdeplug2-dev:armhf libbluetooth-dev:armhf

And try the build[1]:

 # dpkg-buildpackage -aarmhf -B

Which sadly errors out. Turns out the cross-build support in debian/rules is broken. Instead of --cc we need to feed an --cross-prefix to the ./configure of qemu. Edit the debian/rules with replacing

-  conf_arch += --cc=$(DEB_HOST_GNU_TYPE)-gcc --cpu=$(QEMU_CPU)
+  conf_arch += --cross-prefix=$(DEB_HOST_GNU_TYPE)-

Optional: Since we are cross-compiling from a multicore machine, lets also add parallel building support, by changing the override_dh_auto_build: rule to have --parallel flags in debian/rules as well:

override_dh_auto_build:
        # system build
        dh_auto_build -B system-build --parallel
ifeq ($(DEB_HOST_ARCH_OS),linux)
        # user build
        dh_auto_build -B user-build --parallel

        # static user build
        dh_auto_build -B user-static-build --parallel

Try the build again:

 # export DEB_BUILD_OPTIONS=parallel=4 # I have dual-core hyperthreading machine, build with all four threads
 # time dpkg-buildpackage -aarmhf -B
 ...
dpkg-buildpackage: binary only upload (no source included)

real    18m53.425s
user    65m42.570s
sys     2m50.383s

The Native build of qemu-linaro took 4h 11min.

[1] You should not build as root - but to keep instructions short, I'm not explaining howto add and use a unprivileged user in a chroot. Do as I *say*, not as I *do*!