E81 CSE 522S: Advanced Operating Systems

Spring 2019

1. Course Description
2. Prerequisites
3. Discussions/Studios
4. Labs
5. Course Project
6. Class FAQ
7. Textbooks and Other Resources
8. Grading
9. Accessibility
10. Academic Integrity

Course Description

The objectives of this course are for each student to:

• develop a strong system-level intuition about the operation of the Linux kernel;
• use tools to monitor and examine what kernel mechanisms are actually doing; and
• gain hands-on experience using kernel mechanisms in a variety of scenarios and evaluating (and potentially affecting) whether the resulting behavior conforms to given performance specifications.

This is a hands-on graduate-level course dealing with complex systems software, which is being substantially revised again this semester (largely to refine the ordering of topics and give more attention to issues that arose in its previous edition). Hiccups are to be expected, and finding new and exciting ways to break course exercises is encouraged, as the instructor continues to fine-tune the content and scope of each class meeting.

Prerequisites

• CSE 422S (Operating Systems Organization) or an equivalent hands-on undergraduate level operating systems course is a firm prerequisite. If you have not taken CSE 422S here at Washington University in St. Louis with Profs. Kocoloski or Gill, you are strongly encouraged to review and make use of (and possibly even repeat) selected readings and studios that can be found on Prof. Kocoloski's CSE 422 web site.

Discussions and Studios

Most class periods are accompanied by suggested readings. The Linux kernel is a particularly compelling subject of study, in that many of the discussions (and disagreements) among the original developers have been saved verbatim in repositories such as the the Linux Kernel Mailing List (LKML) or documented by firsthand witnesses at sites such as lwn.net. The course textbooks can be used as technical references for kernel mechanisms, and supplemental readings in them can be used to understand the particular design choices made in the course of kernel development.

The course schedule is as follows. Note that this schedule may change over the course of the semester. If changes occur, students will be notified in class and in Canvas and given enough advance notice so that readings and other preparation may be accommodated.

Labs

There will be two lab assignments for this course. The purpose of these labs is to apply course concepts and to evaluate competing design alternatives for kernel mechanisms. As such, each lab will require a written report detailing your findings in addition to a code submission.

Each lab will be completed in a team of two or three students, and teams may be different for each lab. Students from different teams may discuss the lab assignments only during course meeting times. Students on the same team are of course encouraged to discuss and work on lab assignments at any time.

Labs submitted on time (as determined by the email server's receipt time stamp) will be given full credit. Labs submitted up to 24 hours late will be given a ten percent penalty. Labs submitted between 24 and 48 hours late will be given a twenty percent penalty. Labs submitted after 48 hours late will not be given credit, except in the case of extenuating circumstances approved by the instructor.

Course Project

The course project gives a team of two or three students an opportunity to propose and complete their own significant extension of, or modification to, the Linux kernel. This may be an entirely new capability or an alteration to some existing functionality. Each team will evaluate the effectiveness of its modification by developing their own test cases that can successfully demonstrate the new behavior. Students are encouraged to look to their own labs, interests, and/or research projects for inspiration and ideas for projects.

In either case, students will justify their proposal in a written document, in order to ensure that the scope of the project is achieveable. The proposal document will:

1. Propose a modification of, or extension to, Linux kernel behavior
2. Clearly explain the purpose of the modification or extension
3. Identify any kernel files that will require modification or extension
4. Identify any kernel data structures that will need to be changed or extended
5. Identify any kernel concepts and control paths that will need to be changed or extended
6. Propose a set of test cases that demonstrate and test the modification or extension
7. Identify any kernel modules or user space programs that will be produced in order to implement, or to validate and test, the modification or extension
8. Include a five-week planned schedule for the project, including detailed design, implementation, initial evaluation, project presentation, and project writeup phases.

The project will be evaluated in part based on a live presentation at the end of the semester, as well as based on submitted code and documentation. This presentation should explain the modification or extension to the other students in the course; describe any alterations or extensions to kernel files, data structures, or concepts; present timing graphs or other data to verify the behavior of the modified system; and may include a short demo (if possible within the allotted time).

Class FAQ

Current and past instructors, TAs, and students of this course have contributed various tips, tricks, and solutions to problems that they have encountered. Please let your instructor know if you have something you'd like to add here!

Class FAQ

Textbook and Class Resources

Students should consider the in-class studios and assigned readings to be a guided tour of the Linux kernel. Like any good tour group, we want to see the sights and learn some neat highlights about who built it and what they were trying to accomplish. But, the studios and assigned readings will not make you an expert on the Linux kernel. When it comes to learning the details of a code base as deep and complex as this, there is no substitute for reading source code. Lectures and studios will come with pointers to relevant source code files, and it is expected that students will spend time absorbing the content there as well. Therefore, assigned readings are kept moderately short with the expectation that you will spend some independent time in the source code.

To be clear, you are not expected to understand or memorize every line of the Linux source. Exams will not have questions derived from the Linux source (though basic kernel concepts and pseudo-code are fair game). However, the kernel is a huge set of deeply interdependent source code files. The only way you will ever understand it is by looking through it many times.

There are two required course textbooks: Linux Kernel Development by Robert Love, 2010 (noted as LKD in the assigned readings) and Linux System Programming by Robert Love, 2013 (noted as LSP in the assigned readings). These are both excellent, compact, and inexpensive texts that give the reader a basic understanding of Linux kernel and library design and usage, written in depth by an expert Linux veteran.

Readings in one optional additional course textbook also will be suggested: The Linux Programming Interface by Michael Kerrisk, 2010 (noted as LPI in the suggested additional readings, which will be added to the syllabus as the semester progresses).This an excellent, somewhat more extensive reference manual, also written in depth by an expert Linux veteran.

There are a variety of other useful references as well. None of these will give you the level of competency that comes from looking at code itself, but they are very useful for starting points and clarifying problems. However, the Linux kernel is rapidly updated, so while the general information in these books is correct, details such as source code, names of files, and where files exist is likely to can and does change.

• Understanding the Linux Kernel by Bovet and Cesati, 2006. This is a more exhaustive reference to the kernel than the course textbook, covering many data structures and code snippets in detail. Available online for free through the university's subscription to the O'Riley Safari service.

• Linux Device Drivers by Corbet, Rubini, and Kroah-Hartman, 2005. This book covers a topic that we will not go into in detail, but contains some useful reference material over kernel modules, kernel development, kernel locking, timing, and other topics. Available online for free through lwn.net.

• LWN.net is a news and information outlet for the open source community. They often run very high quality articles about kernel development, kernel architecture, and kernel mechanisms. When I have trouble finding a good online resource, a search for "lwn.net (my_topic)" often yields good results. However, beware of out-of-date material.

• Linux Journal is a magazine covering the Linux community. They often run very high quality articles about kernel development, kernel architecture, and kernel mechanisms. Similar to above, searching for "Linux Journal (my_topic)" often yields good results. As above, beware of out-of-date material.

• Linux Cross Reference by free-electrons.com. This tool easily allows you to browse the Linux source code as well as search for identifiers. Beware that the source code on this site is not identical to the code base we are using in class, but it is still useful.

Students will require a Raspberry Pi 3 in order to complete daily studios and lab assignments. The course has been designed with the intention that students bring these devices to class, plug them in, and do some hacking there. Monitors, keyboards, and mice will all be provided for this purpose- you will need to provide the Raspberry Pi 3, a power cord, and an HDMI cable.

If you so desire, you may set up your Raspberry Pi 3 in your home or office and configure it for remote access. However, the instructor cannot support you in this, and we are modifying the kernel so you may be rather lost if you reboot and can't ssh back into your machine. Also, be forewarned that some exercises will require an X11 window, so simple ssh access will not be enough to do everything remotely.

Grading

There are four activities for which you will receive credit in this course: studios, labs, exams, and the course project. Studios are daily guided assignments primarily designed to familiarize students with course concepts, development tools, and the kernel source code (i.e. knowledge and comprehension tasks). Two lab assignments will ask students to apply general course concepts and analyze kernel design alternatives. The course project requires that students propose and complete a novel kernel modification. Two in-semester exams will evaluate your technical understanding of course concepts.

Your grade will be determined as follows:

Accessibility

Academic Integrity

Each studio, lab, and project assigned in this course is expected to be completed collaboratively by two or three people (and not more or less than that). Student teams may change from assignment to assignment, but the sharing of code between teams working on the same assignment is strictly prohibited, and you must acknowledge and document in detail all contributions that anyone has made to the work.

Exams must be completed individually without assistance from any other person and without reference to materials or devices, except as specifically allowed by the instructor (documentation of what is allowed will be described in class, provided in the corresponding review slides, and written on the font page of the exam).

Cheating costs everyone something. Someone who cheats misses out on the intended opportunity to improve through the assigned work, and like anyone helping them cheat is at risk of diminshed reputation as well as of specific sanctions. Cheating also degrades the value of the degree earned by those who complete their work with integrity.

We take academic integrity very seriously in this course, and any cases of cheating will be referred immediately to the Engineering School's academic integrity process. The instructor will make final determinations on whether or not to make any such referral. If in any doubt, please ask first.

Acadmic integrity is itself worth studying and thinking about as a key component of your education. Please read, familiarize yourself with, and reflect on the Engineering School's and Washington University's undergraduate and graduate policies on academic integrity.