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Martin Stein avatar

Spunky #3: Desktop system, FOSDEM video, scheduler, plans


In this series of articles I'll illustrate a hobby project of mine that is trying to create a kernel for Genode written in Ada 2012. This project is not about writing a kernel from scratch but rather successively take parts from the existing base-hw kernel and translate them to Ada. Thus, the design mainly follows the approach taken with base-hw. To be able to test the already translated parts, I link them together with the remaining parts from base-hw. The interfacing between the Ada and the C++ parts is done on the level of object methods. Over time, the code base of the new kernel will become more and more Ada and less C++. Maybe later this work will also lead to some formal verification with SPARK. But for now, I'm happy with Ada. So let's go!

You can find the code behind this article on my Github branch. If you're interested in the recent state of my work, you may have a look at the Github issue. You also might want to read the former articles of this series:

Running the Sculpt desktop OS on Spunky

Running Sculpt on the new kernel was not only a wonderful real-world test lurking from right behind the corner but also an absolute must-have for me! In the end, one main motivation for starting with Spunky, was the perspective of having it running underneath the system I'm working on. So, Sculpt now fluently runs on Spunky. At this point I'd like to thank Stefan Kalkowski for providing several Sculpt tweaks and Alexander Böttcher for enabling write-combining support in no time!

Do you like to try it yourself?

Get the sources:

 git clone https://github.com/m-stein/genode.git
 cd genode
 git checkout 3308_spunky_a_kernel_using_ada

Create a build directory:

 ./tool/create_builddir x86_64
 cd build/x86_64

Open etc/build.conf and enable all repositories, automatic package creation, and parallel building by uncommenting these lines:

 #MAKE += -j4
 ...
 #RUN_OPT += --depot-auto-update
 ...
 #REPOSITORIES += ...
 #REPOSITORIES += ...
 ...

Enable creation of a disk image by changing –include image/iso to –include image/disk in the same file. Save and close the file.

Prepare required third-party sources (they will all be downloaded to <YOUR_GENODE_DIR>/contrib):

 ../../tool/ports/prepare_port -j4 \
    ada-runtime bash coreutils curl dde_ipxe dde_linux dde_rump \
    e2fsprogs gnupg jitterentropy libarchive libc libgcrypt libpng \
    libssh ncurses openssl stb ttf-bitstream-vera vim x86emu xz zlib \
    grub2

Start building:

 KERNEL=spunky BOARD=pc make run/sculpt

It may take a while. Once it finished successfully, you can write the image directly to a bootable USB stick:

 sudo dd if=var/run/sculpt.img of=/dev/sdX bs=1M conv=fsync

For information about what you can do with your freshly created Spunky Sculpt, please refer to the Sculpt documentation

FOSDEM video

I totally enjoyed the FOSDEM and I'm still happy that the Ada folks let me present Spunky in their Devroom. I sensed so much interest in my little project - that motivated me a lot, thanks! If you'd like to watch a recording of the presentation online, the excellent FOSDEM staff made it available to everyone:

Scheduler

The CPU scheduler of Spunky now is also written in Ada. I'm getting more and more accustomed to the frictionlessness of integrating new packages. But the scheduler already is one of the most complex units of the design and it's especially critical to the system performance. Anyways, the new Sculpt scenario doesn't show any problems with the update and while I'm writing this, I'm already sitting at the next module - my first encounter with real low-level programming in Ada - the APIC timer driver.

Plans

By the way, Spunky has made it to the official Genode roadmap! Until August this year I'm planning to make Spunky all Ada and remove all dependencies to base-hw code. Once this is done, I will start thinking about how to re-design the kernel to make it SPARK compliant. I hope that I can do some first basic proves (flow mode) till the end of the year.