It’s that time of the year. Google is, yet again, sponsoring students to write some awesome open source code this summer. If you’re a student, and you’d like to make some money contributing to some of the most well known and exciting open source software projects out there, you’d be missing out on a lot by not applying.

If you’re wondering about what the best way to get started is, check out this great advice page. All projects have also been tagged by programming language and field in this delicious profile. You can also search for ideas here.

I’m going to be mentoring for Mozilla, Glendix (under the Plan 9 Umbrella) and Gentoo this year. Get in touch if you’re interested in any of those ideas

The window for applications opens in a few hours. Good luck everyone!

As a developer, I have to say that FOSS.IN/08 is possibly the most productive conference I’ve been to until now! In just 5 days, I’ve got more things done than I have in the last 5 months

Let’s start with the Beacon workout: Nandeep joined us via VoIP and we got started almost immediately, thanks to the dynamic nature and small size of our project – we didn’t have any infrastructural trouble as a few other C/C++ projects with huge codebases and complex build systems did. We had a list of 6 tasks in mind, and we managed to complete 3 of them. Salil Kothadia got started with writing a PDO data backend, and promptly submitted the patch to us next day. Thanks Salil, hope you continue to contribute to the development of Beacon (thereby increasing the development team size by 25%)!

I also attended Philip’s workout on porting HTML::Template to Javascript. As mentioned on the Wiki page, we mostly worked on the design during the first half or so, and then moved on to writing a skeleton for the whole framework. I think this is an extremely interesting project, and am very happy to be associated with its birth. Hope we can continue the momentum and work until it is finished.

Perhaps the biggest take-away from the conference for me was the ability to give a lightning talk about Glendix, with several kernel hackers present in the audience. Christoph then kindly offered to review some of the patches during the workout. Even the possibility of Plan 9 binary emulation being considered for inclusion into the main kernel tree is amazing, let alone the fact that I got the guidance of an experienced kernel hacker for a good 2 hours! I think the effort was largely successful – I now have a better idea of what I need to do in order to get a kernel patch in order, and also got a few hints as to how I can implement the missing bits.

My primary focus at the conference was to give a talk on Mozilla Labs and Innovation. I think I managed to stir up a decent amount of interest in the various Labs initiatives. I covered the different ways in which members of the community can contribute, specifically focussing on Weave, Ubiquity and the Concept Series. We even covered how easy it is to actually write an Ubiquity command. I now look forward to increased participation by the Indian Mozilla community in Labs projects. Don’t forget to thank Mary for all the goodies!

All this, apart from regular conference happenings like catching up with old friends, making new ones and free swag (great mugs and t-shirts this time around) makes FOSS.IN/08 one of the most successful conferences I’ve been to so far! I can’t wait for the 2009 edition

Glendix has been making the rounds on the web lately, with coverage from OSNews, Reddit, and even a Russian site, Linux.org.ru. It’s really motivating to see some buzz around the project, giving me the extra boost needed to push the completion of a usable release!

Some of the major obstacles that have to be crossed before making a beta-quality release are the completion of critical synthetic filesystems – especially /net and /draw. We also have to work out the kinks with per-process namespaces and union mounts. I don’t know if we’ll be able to get Rio running as a WM before an official release; if not, Plan9Port’s Rio and WMII are good candidates.

The biggest criticism of Glendix seems to be the reasoning that Plan9 user-space tools are somehow superior to their GNU counterparts, and several people have asked us to substantiate our claims. At this point, however, I don’t think that it is really important, or even relevant. Even if Plan9 user-space tools aren’t somehow better – I think it is generally a refreshing idea to see Linux combined with a user-space other than GNU.

We’re at FOSS.IN this year, where a large number of kernel developers have gathered; and I hope to get some of their valuable input on the problems Glendix currently faces, and maybe even write some code to solve them

Thanks for all the community support and critical comments, they are all very vital feedback for the project and are much appreciated!

Continuing with my travel spree, I made a trip to Volos, Greece and back for the 3rd International workshop on Plan 9. I was to make short presentation on Glendix, a paper on which was selected for the workshop.

Being a brown single guy in his early twenties, traveling around Europe is not exactly fun. Just saying. I got picked out not once, not twice, but THREE times for “random passport and security checks”. Once in Munich on my way to Volos, once on the streets of Athens, and finally on my way back at the Frankfurt airport. Not that I’m complaning, they were just doing their job; but really, they need to get better at profiling.

Athens is a really nice city, though it reminds me of India: crowded trains, chaotic traffic and sketchy bus stations. I knew most of the Greek symbols, thanks to high school Math courses, but pronouncing them wasn’t easy. Thankfully, the people at the counters in the Airport, Bus and Metro stations knew English. After a 5 hour bus ride, I reached Volos in the wee hours of Thursday. After around 3 hours of sleep and about 30 minutes of slide preparation, I was set for my talk.

Considering I was at a Plan 9 conference, talking about integrating it into Linux, my talk was very well received. Certainly beyond my general expectations: I got some really excellent questions, comments and general observations, and most importantly, a lot of help on the current issues that Glendix faces. All the other talks during the conference were extremely interesting as well, I was particularly fascinated by the concept of “Upperware”, the Inferno port to Nindento DS, and the Mrph morphological analyzer. Do check out the entire conference proceedings.

It was great to finally meet all the Plan 9 and Bell Labs folks in-person, especially: Sape Mullender, Charles Forsyth, Bruce Ellis; not to mention the IRC regulars uriel, quintile, sqweek and fgb!

The return trip was a bit more scenic, thanks to it being afternoon. After spening the night in Athens, I was back in Amsterdam the next day. More adventures followed, but that’s for another blog post.

Nothing like a trip to IWP9 to humble you!

P.S. Cool Glenda goodies for sale at Cafepress

The first step in the Glendix project was to write a binary loader for the Plan 9 a.out format. Linux has a clean interface for registering new binary format handlers from a module. Basically, you define a structure of type linux_binfmt and call register_binfmt during initialization of the module. Now all that’s left to do is implement the three functions that you pointed to in your structure: load_binary, load_shlib and core_dump.

Luckily for me, all Plan 9 executables are statically linked so I can just leave load_shlib as NULL. core_dump is also not that important during the development stages, although the final product must definitely implement it. To get a feel of what I needed to do in load_binary, I decided to take a peek into some of the other binary format handlers. I tried to comprehend the code for ELF with not much luck. I then turned to UTLK, which helped me understand what was going on. I highly recommend the book for anyone interested in kernel programming.

Anyway, here is when I found out that all ELF executables have sections that are actually page aligned! That means every ELF executable contains a bunch of zeroes after the TEXT section, so that the DATA section starts at the next page address. That’s how the executable is supposed to be laid out in memory, but I had no idea someone would actually think of doing it in the file. I guess they have their reasons, all the binary format loader does is mmap the file. Maybe for ELF2 they could put in zeros for the BSS section in the file too

Plan 9 executables on the other hand, are just normal files with no padding. This gives me a headache because I can no longer use mmap. Recall that all addressees passed to mmap have to be page-aligned. But the DATA section in Plan 9’s a.out will start at a non-page-aligned address most of the time.

One of the first things I tried to do was to mmap the file into a high address, copy portions into the appropriate locations and then free the mapping. That didn’t work so well because:

• memcpy works only on physical addresses. Logical addresses from the virtual process address space can’t be easily translated to physical ones because Linux delays physical memory allocation for as long as possible. Now we know why all the loaders use mmap, it is fundamental to the “Linux way” of memory management.
• There is no generic copy_in_user implementation. There are specific ones that use assembly code for PPC, SPARC and even x86_64, but none for x86. The alternative was to use copy_from_user to move data into kernel addresses and then bring them back using copy_to_user. That didn’t work out well either – copy_to_user kept failing for some reason.

I ended up writing a userspace program called ‘pad’ that page-aligns a Plan 9 a.out executable. The loader just mmap’s the file, like all other loaders. The solution is suboptimal, if someone knows a clean way of doing all of this in kernel-space, I’ll be grateful for the help. The ultimate goal is to run Plan 9 executables on Linux, unmodified.

The code for the loader and the pad program can be found on git here.