Between Tuesday August 20th, 5:00pm and Thursday August 22nd, 8:00am will be down for an upgrade to version 10.8.7.



KOS ("Chaos") is an experimental operating system kernel.


KOS (pronounce "Chaos") is an experimental operating system kernel that is designed to be simple and accessible to serve as a platform for research, experimentation, and teaching. The current version runs on a bare-metal AMD/Intel 64-bit platform (x86-64), utilizing all CPU cores in 64-bit mode, and using virtual memory through 64-bit paging. The system is comprised of a small runtime nucleus along with other subsystems typically found in an operating system kernel -- at various levels of maturity. For example, KOS provides basic memory management, scheduling, threads, address spaces, processes, system calls, etc. It implements APIC programming, interrupt handling, and PCI enumeration. A few device drivers are included. It also comes with basic debugging support using gdb remote debugging. The system has been tested on the virtual platforms qemu, bochs, and VirtualBox, as well as a few actual machines.


Installation instructions are provided in

Known bugs are described in


A draft document describes the principles, design, and implementation of KOS.


The user-level fibre runtime in src/libfibre/ has been developed in close collaboration with Saman Barghi. All bugs are mine though. ;-)


The following students (in alphabetical order) have helped with various parts of KOS and the shared runtime code:

  • Saman Barghi (lock-free intrusive mpsc queue)
  • Sukown Oh (e1000, gdb)
  • Behrooz Shafiee (elf, keyboard, lwip, pit, syscall/sysret)
  • Priyaa Varshinee Srinivasan (synchronization)
  • Alex Szlavik (bootstrap)
  • Cameron White (clang support)

The following students (in alphabetical order) have helped with various parts of libfibre:

  • Qin An (FreeBSD/kqueue)
  • Bilal Akhtar (gdb extension)
  • Peng Chen (split stack support)
  • Wen Shi (gdb extension)
  • Shuangyi Tong (multiple event scopes)


KOS is currently distributed under the GNU GPL license, although this could change in the future.

Third-Party Software

KOS is built using gcc with newlib as the C library, as well as grub for booting. KOS can also be compiled using clang (using gcc's C++ library). Further, KOS integrates acpica and lwip as external software packages. Please see their respective license information when downloading the source code. Finally, KOS is distributed with and uses the following software packages, which can be found in the src/extern/ directory. Please see the source code for detailed license information. The summary below is just a high-level overview of my interpretation of the license terms.

  • cdi: BSD-type license
  • dlmalloc: public domain / creative commons license
  • elfio: BSD-type license
  • multiboot: BSD-type license

Feedback / Questions

Please send any questions or feedback to mkarsten|at|