Kernel Development Made Easier

08 March 2017

A little while ago I wrote a post about creating a Linux system call. In it, I explained how to create a virtual machine, get the Linux source, modify it, build it, and boot your custom kernel. This is a totally valid way to do kernel development, but it can be a bit inconvenient. For one, the code was stored within the VM, so all editing and compiling was done in a VM too. For another, there was a pretty complex process to build an “initrd” in order for Arch Linux to boot properly. And finally, the kernel configuration we used was pretty massive, resulting in longer build times for extra features and device support to be compiled into the kernel.

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Introducing CWRU Love

19 February 2017

On Valentine’s Day, Yelp announced that they had open-sourced Yelp Love. What is it? In their own words:

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Revisiting the BART Algorithm

11 December 2016

Over the summer I wrote about my hackathon project, an app that virtually swaps BART tickets in order to reduce fares. This was a purely academic exercise, to apply some concepts I had learned from my “Advanced Algorithms” course to a problem in the real world. I described how you could model this problem as an (integer) linear program, and I guessed that the problem is, in fact, totally unimodular. However I offered no proof of this, and due to hackathon time constraints I was forced to use a slow, somewhat half-baked greedy algorithm to solve the problem.

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Tutorial - Write a System Call

14 November 2016

A while back, I wrote about writing a shell in C, a task which lets you peek under the covers of a tool you use daily. Underneath even a simple shell are many operating system calls, like read, fork, exec, wait, write, and chdir (to name a few). Now, it’s time to continue this journey down another level, and learn just how these system calls are implemented in Linux.

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Kernel Segfaults for Fun (but no profit)

03 November 2016

In “episode 2” of my kernel development series, I’m going to talk about how I put Python into an uninterruptible sleep. This spooky story involves a rogue kernel module, segmentation faults, and reference counting (a topic already well established to be spooky). And only a few days late for Halloween!

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Stephen Tries Kernel Development: Episode I

13 October 2016

For the past few weeks I’ve been dipping my toes into Linux kernel development, as part of the work I’m doing for my master’s thesis. Like most things that stir up my nerdy interests, it’s leaked onto Twitter quite a bit…

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Hello, HTTPS!

27 September 2016

An exciting announcement! Starting a few days ago, when you visit my website, you should see a green padlock next to the URL bar.

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Fare Hacking on BART

23 July 2016

Imagine that you’re taking a long train ride on the BART. Maybe from Millbrae to North Concord. Chances are, at the very same moment, somebody else is going the other direction. For example, maybe from Pittsburgh/Bay Point to San Bruno. In case you haven’t memorized BART’s stops, here’s a useful map illustrating these rides:

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Authentication with Hash Chains in C

19 June 2016

One of my silliest long-running projects is a chatbot called cbot. All it does is connect to an IRC (Internet Relay Chat) server, and respond to people’s messages. For instance, if you greet it, it will greet you back. If you insult it, it will send you a poorly-constructed comeback. Obviously there’s nothing groundbreaking about it - there are other chatbots that are much better. I made cbot because I wanted to learn some new concepts (specifically the IRC protocol and dynamic loading), and it was really helpful for that purpose. Plus, it’s another project in C, and I like projects in C!

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Academic Dishonesty

29 March 2016

Last night I had a sobering experience. A faculty member from another university sent me a message letting me know that some of their students had turned in modified versions of my shell, lsh, for a homework assignment. Maybe I shouldn’t be too surprised. Writing a shell is a very common assignment for computer science students. My tutorial based on lsh has somehow managed to climb the ladder to the first page of search results for many queries related to writing shells. So at the end of the day, I guess this was bound to happen. And even though I can’t really be held responsible for what other people do with my tutorial and code, I feel pretty bad about this. Although there’s not much I can do to prevent students from presenting my shell as their own, I feel like I should point out why it’s such a terrible idea.

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