This post was originally published as A look from behind the Open Source Bios on Scaleway’s blog.
This is a followup post of Open Source Bios at Scale so you might what to read it first as this post will get more into details.
As explained in the previous post our BIOS is build with three main components: coreboot, Intel FSP and TianoCore. We will describe here how those three parts are fitting together.
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This post is a summary of my talk at FOSDEM’18 and was originally posted on Scaleway’s blog.
At Scaleway we started to design our servers with the ARM C1.
Later we switched to a x86 architecture to provide the C2 and Dedibox SC2016.
On x86 a BIOS is required to start the server. BIOS software got many legacy and backward compatible software to ensure a reliable behavior across many boards. I was in charge of the BIOS development for our new generation of x86 servers.
This article presents technical choices we used during our development.
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Now that I have access to the serial console on Samsung e60 reader let’s build a new linux kernel for it.
The e60 reader has an ARM processor, to compile the kernel we need a cross compilation toolchain.
The first option is to use the one Samsung released with the other sources. It must work, however I don’t really like the idea to run binaries from unknown sources.
The second option is to build our own toolchain, we often have to do that for systems that requires patches on the compiler.
Here, Samsung’s binutils look like they were taken between 2.17 and 2.18 release (they are named 2.17.50 but are still slightly different from this snapshot) but they don’t seam to embed homemade patches. As for ggc I didn’t take time to check.
I choose to use the emdebian cross-development toolchain lenny version. (As the article in the french open silicium magazine #1 about FriendlyARM proposes to do).
First the archive keys:
sudo apt-get install emdebian-archive-keyring
Then we add a /etc/apt/sources.list.d/emdebian.list file with the following content:
deb http://ftp.uk.debian.org/emdebian/toolchains lenny main deb-src http://ftp.uk.debian.org/emdebian/toolchains lenny main
The we update the package list to install the needed packages:
sudo apt-get update sudo apt-get install libc6-armel-cross libc6-dev-armel-cross libstdc++6-armel-cross binutils-arm-linux-gnueabi gcc-4.3-arm-linux-gnueabi g++-4.3-arm-linux-gnueabi
That’s it ! We have now our cross-compilation toolchain installed from packages, so easy to update or remove.
Samsung released it’s modified 2.6.29.4 version. By cloning the kernel 2.6.29.y git branch, I could quickly see that their changes applied well to the 2.6.29.6 version (the last in the branch).
In order to better sort the changes michel.s had splat them into several patches
(patchs on e60-open project). After a few trials I build a series file allowing to apply those patches with quilt or better to import them to a git branch with git quiltimport. The order I choose allows to drop easily some patches (the last ones).
One particular point on those patches is that some include binary files:
fs/rfs/*.o a proprietary journaling layer over FAT. If you want my point ov vue, we don’t need that. After all we have free journaling file systems available and linux is able to mount something else than FAT over USB…drivers/usb/gadget/file_storage.o also the corresponding .c file was removed, the BSD/GPL license from the original code allows a binary distribution (however I didn’t check if Alan Stern’s name appears in the doc) but I’d have liked that Samsung give that source code.Before compiling the kernel, we need the mkimage utility from U-Boot. Here, Let’s build the U-Boot released by Samsung, and let’s just copy the tools/mkimage to a location in our PATH (that’s the only install method I could find).
make smdkc100_config make CROSS_COMPILE=arm-linux-gnueabi- cp tools/mkimage ~/bin/
For the config, one of the patches includes a .config. That file is a copy of config_rfs so even without the previous patch, we can get Samsung’s config.
Finally we can compile!
make CROSS_COMPILE=arm-linux-gnueabi- CFLAGS="-march=armv4t -mtune=cortex-a8" CXXFLAGS="-march=armv4t -mtune=cortex-a8" ARCH=arm uImage
We can then load our kernel by following The kernel testing howto from e60-open project. To load the kernel we will need the following command:
sudo dnw arch/arm/boot/uImage
That’it, and it works ! Well almost, the kernel cannot find his modules. This will not be a big deal for the ones included in the sources (but the subject of a next post) but the /lib/modules/max14540.ko and lib/modules/dhd.ko modules are not included in the sources while reporting a GPL license to the kernel.
The Samsung Open Source Release Center website has a contact form, but it does not seam to work (I even booted my netbook on windows to try with IE8 without success). After browsing the french e60 forum I found their email address and mailed them, no answer so far (not even automatic). Let’s wait …
We can compile a kernel for the e60 reader without using the cross tools from Samsung.
There still some work to load modules as the one on the reader are copiled for 2.6.29.4 and our kernel does not want to load them. (I’ve already done a few tests but that will be a next posts’ topic.)
But without the missing sources it will be hard for us to best use our e60 reader.
Update: I got an answer from Samsung, they updated the released archive. I still have to look at it.
I wanted to work on linux kernel from some time, but didn’t really know where to start. One day a wise man told me “a good way to learn is to do it! So get an USB device and write the driver for it.” I answered: “Well I didn’t thought of that, usually I’d use libusb for such cases.”
Some days later, I didn’t find any nice device, but I thought, why not building it as well?
As I already told you, I’ve already hacked out an USB device: USBtinyISP. So I got back to the original code: usbtiny and I build myself a small device with 4 LED and 2 buttons:
I didn’t use and ATtiny, but an ATmega8 to keep more room for future improvements 😉 (The ATtiny2313 is already full with the USBtinyISP code).
And here is the schematic: (as picture, the gschem sources stay in git under the sch folder):
Once the wiring done, some few lines of code based on the usbtiny sample, and that’s it: A firmware for the ATmega (in the root of the project).
Then I needed to test it, so back to the first idea, some code lines using libusb, available in the test, helped to improve the firmware 😉
Everything’s OK, let’s write a driver.
Well I just followed some tutorials:
Finaly looking at the usbled.c file in Linux sources to get some more updates.
This build a module that adds the files leds and keys in the device folder that Linux creates in /sys/bus/usb/.
That’s it! I don’t know if you learned something, but I did learn a lot! 😉
All source code are available under GPL2 or GPL2+ on my gitweb: jvdg_usbgadget.git
As for the egocentric name, it’s just to avoid any name conflict. This has no mean to be integrated anywhere anyway. (The device uses an USB ID reserved to prototyping, so unusable for products…)
I’ve been more on software recently, and I didn’t blog much…
I’m still maintaining openchrome Xorg driver, not much to do now that the latest upstream SVN version is on KiBi’s X autobuild system. Except waiting for the bugs to occur.
I also just requested to become DM to release the X Strike Force of the task of sponsoring me…
After a rather awkward first message (still sorry about that), I started working on webalizer’s debian package.
Nothing’s published yet, but this will come.
Finally I received an email from Axel Beckert about xrootconsole, well he already blogged about it, I accepted to co-maintain xrootconsole with him. More details on my xrootconsole page.
To conclude, after some month following the debian community, I’m starting to feel part of it!
After some work here it is : netsed 1.00a !!
Basically this version is an architecture rewrite to add UDP support and remove the use of fork().
I’m pretty happy with the current feature set and code state so I think it will stay like that for a moment.
However feel free to test it and report bugs.
I’ve recently learned to use git (for my xorg adapted packages) and used it later for netsed.
In order to develop UDP in netsed, I had to try several stuff, my network programming experience in C is back to some school time, so this was really trial and errors. And here git really helps, all I had to do is create branches for each trial, so I don’t loose any tracks I’ve taken, then when I found the right way to do it, I could just merge or cherry pick from the branches (or even just copy past from gitk to my favorite editor gvim) and that was it !
Of course I can now delete the trial branches, but those were really helpful during development time.
This meant abusing of git commit --amend, git merge ( --squash ) and git cherry-pick commands, but well you cannot build a clean code without effort.
I should probably give another look at git stash which seams to fill similar needs.
Netsed, the network packet stream editor, is a program originally written by Michal Zalewski
While the program idea is good, it’s implementation had some lack, and nobody seamed to care enough to fix it.
I did already hack it some years ago, and it appeared that my changes was fixing a debian RC bug (#586037) so I took netsed maintenance as one of my new projects!
For now only my changes and patches proposed by Mats Erik Andersson are integrated.
But I will start working on a test suite (still have to find the right tools for that, would ruby be nice ?), and of course implement UDP support.
Also I’d like to really thank Mats Erik Andersson and Tim Retout for their answers and support.
Resources:
After yesterday’s trouble, I just upgraded all my plugins.
Gengo’s URI renaming scheme with language code at the end was leading to an infinite redirect (adding fr+en/ to the URI) so I had to disable it. But doing so breaks the existing URI on your bookmarks (if you had some) and on Google…
So I hacked gengo again so that if the URI ends with a language code, it is redirected to the basic URI.
A recent reading : Cool URIs don’t change is just about keeping the URI, here I’m redirecting, that’s not as good, but at least you wont get the 404 😉
The link was on Peter Eisentraut’s Blog. I was reading his article about Remove and Purge. I was tempted to do the same, I even did for a few days. Then I read the comments, and ended using aptitude l~c view 😉 . I was previously using synaptic only for purging residual configuration…
Trying to use zenphoto I found it does not have an option to have the admin tasks in https and the gallery in regular http.
WordPress is doing this and reading Rian’s article: SSL and Cookies in WordPress 2.6
I had a better idea on how it works.
Before coding, I also read How to Properly Provide Mixed HTTP and HTTPS Support from mikeperry’s blog.
And this is basically what I implemented.
For once the result of my work is not hosted on my blog but directly on zenphoto’s trac : The ticket with zenphoto patch to allow both http and https.