zhiming-xu / p1-kernel

A tiny, modern kernel on real hardware

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

0. Sharpen your tools! (p1 exp0)
1. Helloworld from baremetal (p1 exp1)
   • Power on + UART bring up
   • Simplifying dev workflow
2. Exception elevated (p1 exp2)
   • CPU initialization, exception levels
3. Heartbeats on (p1 exp3)
   • Interrupt handling
   • Interrupt-driven animation
4. Process scheduler (p1 exp4)
   • A. Cooperative
   • B. Preemptive
5. A world of two lands (p1 exp5)
   • User processes and system calls
6. 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 (6a:10; 6b:10)	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.