AdelaideOS

AdelaideOS is a small operating system kernel designed for teaching purposes. It was developed in 2008 for use in the operating systems course at Adelaide University.

The kernel is around 5,000 lines of code, and has the following features:

• A minimal C library containing printf and several string-manipulation functions
• Dynamic memory allocation (malloc)
• Multitasking and memory protection
• UNIX-style process management using fork, execve, and waitpid
• Interprocess communication using pipes & message passing
• A read-only ramdisk-based filesystem

The code is split into nine different versions, each of which builds on the previous one and adds one or more new features. The purpose of this arrangement is to demonstrate how one can start with a very simple kernel and add features piece by piece. It also permits the kernel to be used as a teaching aid, whereby each new version of the kernel can be covered in a week, and at the end of the semester students will have seen how to construct many of the essential components of a UNIX-like operating system. A series of accompanying lecture notes explain the full details of the kernel's operation, and can be used as a study guide by students while working through a course.

The breakdown of features introduced in each version are as follows:

• Version 1: Displays "Hello world", and illustrates the use of keyboard & timer interrupt handlers

• Version 2: Introduces a few basic C library functions such as such as memset, strlen, strcmp, and printf

• Version 3: Initial multitasking support. All processes run in kernel mode, and have direct acceess to physical memory

• Version 4: Virtual memory and memory protection. All processes run in user mode and can only access memory mapped into their own private address space

• Version 5: System calls

• Version 6: malloc implementation using buddy allocation

• Version 7: Support for pipes and I/O redirection via file descriptors

• Version 8: fork and exec, plus a basic filesystem

• Version 9: Solutions to the two practical exercises: message passing and POSIX-style filesystem access

The source code for AdelaideOS is in the public domain.

Download

• AdelaideOS source code, release 1.0
• AdelaideOS kernel development guide
• Practical exercise: Inter-process communication
• Practical exercise: Filesystem access

Build instructions are given in the kernel development guide. Note: The build scripts only work on 32-bit Linux systems.

The nine different versions are all generated from a common source. The original source files and scripts used to generate the different versions can be accessed from the project Git repository.

For any questions about AdelaideOS, please contact Peter Kelly.