Sp 2025 is over; see you in Sp 2026!

OVERVIEW | LAB1 | LAB2 | LAB3 | LAB4 | LAB5

PAPER

• Syllabus for CS4414/6456, Spring 2025
• Set up the VM
• Set up the rpi3 hardware
• Set up JTAG for rpi3
• Prepare SD cards for experiments
• How to submit

This course is a "guided tour". In one semester, it takes students, who have basic knowledge of the computer software/hardware stack, on the journey of building a modern operating system.

Building an OS can be a tough process, and this course is designed to give students continuous rewards -- both intellectually and emotionally -- just as a good video game or theme park would do.

This course will start from bare-metal hardware ("boot") and incrementally build more features, enable more applications, and eventually run a full-fledged OS, which can run multiple applications ("DOOM") and on a multicore processor.

All OS prototypes are functional, albeit increasingly more "modern". The class assignments (called "quests") will involve completing key features in these prototypes, enabling more applications to run.

Proto 1: Baremetal
A single CPU core can boot, print messages from UART, and display pixels. Interrupts work, allowing periodic rendering of a simple "donut" animation. Everything runs in privileged mode (EL1).

Proto 2: Embedded
This OS resembles what you would see in an "embedded systems" course. In addition to Proto 1 features, it can run multiple tasks and preempt their execution. However, everything still runs at EL1.

Proto 3: Minimal User
This OS introduces virtual memory and user/kernel separation. It provides syscalls and can run one or multiple "Mario" applications concurrently in userspace.

Proto 4: Simple User
The OS now includes file abstraction and file systems. Userspace is built independently of the kernel and executed via exec(). The OS implements more I/O drivers, notably for USB keyboards and a sound device, exposing them via /proc and /dev to userspace. Userspace comprises a simplified libc and applications including Mario, slider, shell, and a sound tester.

Proto 5: Rich User
The OS now boots on multicore (four in rpi3). It includes a FAT32 filesystem and an SD driver, allowing file exchange with PC or Mac. It also includes a "SurfaceFlinger," allowing multiple apps to render on the screen and dispatching input events to the correct app. Userspace is more complete, including a full libc, as well as DOOM (a 3D game), a music player, a blockchain miner, etc.

Proto 5 demo (with sound):

All the code and quests can run on both the emulator (QEMU) and real hardware (Raspberry Pi 3, or rpi3). Using emulator simplifies debugging, while the rpi3 offers a more authentic OS experience.

This course was inspired by and took content from many open-source projects:

• NJU OS course (ProjectN): user/kernel interfaces, rich user apps
• MIT xv6: kernel design
• Circle: bare-metal Raspberry Pi programming
• (and many more)