A tiny, modern kernel for Raspberry Pi 3

Experiment descriptions are for you to read & reproduce. The assignments will be on Collab. They include Q&A and coding assignments.

Get the code:

git clone https://github.com/fxlin/p1-kernel

A tiny kernel incrementally built for OS education.

Start with minimal, baremetal code. Then add kernel features in small doses.

Each experiment is a self-contained and can run on both Rpi3 hardware and QEMU.

Rationale

The kernel must run on cheap & modern hardware.

Showing the kernel's evolution path is important. Along the path, each version must be self-contained runnable.

We deem the following kernel functions crucial to implement: * protection modes * interrupt handling * preemptive scheduling * virtual memory

Experimenting with these features is difficult with commodity kernels due to their complexity.

Goals

Primary: * Learning by doing: the core concepts of a modern OS kernel * Experiencing OS engineering: hands-on programming & debugging at the hardware/software boundary * Daring to plumb: working with baremetal hardware: CPU protection modes, registers, IO, MMU, etc.

Secondary: * Armv8 programming. Arm is everywhere, including future Mac. * Working with C and assembly * Cross-platform development

Non-goals:

• Non-core or advanced functions of OS kernel, e.g. filesystem or power management, which can be learnt via experimenting with commodity OS.
• Rpi3-specific hardware details. The SoC of Rpi3 is notoriously unfriendly to kernel hackers.
• Implementation details of commodity kernels, e.g. Linux or Windows.

Experiments

1. Sharpen your tools! (p1 exp0)
2. Helloworld from baremetal (p1 exp1)
   • Power on + UART bring up
   • Simplifying dev workflow
3. Exception elevated (p1 exp2)
   • CPU initialization, exception levels
4. Heartbeats on (p1 exp3)
   • Interrupt handling
   • Interrupt-driven animation
5. Process scheduler (p1 exp4)
   • A. Cooperative
   • B. Preemptive
6. A world of two lands (p1 exp5)
   • User processes and system calls
7. Into virtual (p1 exp6)
   • Virtual memory management

Assignment weights

Exp	Weights
00 Sharpen your tools	10
01 Helloworld from baremetal	10
02 Exception elevated	10
03 Heartbeats on	10
04a Process scheduler - cooperative	10
04b Process scheduler - preemptive	10
05 A world of two lands	20
06 Into virtual	20

The weights are relative and may not necessarily add up to 100.

Acknowledgement

Derived from the RPi OS project and its tutorials, which is modeled after the Linux kernel.