This is my attempt at self-learning operating systems by implementing new features for xv6. All new implementation is my own work (unless specified otherwise), done in my own time and not for any academic course. When test files have been borrowed from publicly available xv6 labs, credit has been given through the commit history.
In addition to the xv6 source code, Operating Systems: Three Easy Pieces (OSTEP) is an excellent free book for learning bigger-picture ideas about operating system design.
This list will be updated as I implement new features. Implementation is under the "main" branch unless specified otherwise.
- New system call tracing for programs.
- A shared read-only page between kernel and user space to reduce kernel crossings.
- Lazy physical memory allocation for virtual pages in a process's user heap.
xv6 is a re-implementation of Dennis Ritchie's and Ken Thompson's Unix Version 6 (v6). xv6 loosely follows the structure and style of v6, but is implemented for a modern RISC-V multiprocessor using ANSI C.
ACKNOWLEDGMENTS
xv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peer to Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14, 2000)). See also https://pdos.csail.mit.edu/6.1810/, which provides pointers to on-line resources for v6.
The following people have made contributions: Russ Cox (context switching, locking), Cliff Frey (MP), Xiao Yu (MP), Nickolai Zeldovich, and Austin Clements.
We are also grateful for the bug reports and patches contributed by Takahiro Aoyagi, Silas Boyd-Wickizer, Anton Burtsev, carlclone, Ian Chen, Dan Cross, Cody Cutler, Mike CAT, Tej Chajed, Asami Doi, eyalz800, Nelson Elhage, Saar Ettinger, Alice Ferrazzi, Nathaniel Filardo, flespark, Peter Froehlich, Yakir Goaron, Shivam Handa, Matt Harvey, Bryan Henry, jaichenhengjie, Jim Huang, Matúš Jókay, John Jolly, Alexander Kapshuk, Anders Kaseorg, kehao95, Wolfgang Keller, Jungwoo Kim, Jonathan Kimmitt, Eddie Kohler, Vadim Kolontsov, Austin Liew, l0stman, Pavan Maddamsetti, Imbar Marinescu, Yandong Mao, Matan Shabtay, Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel Nider, Hayato Ohhashi, OptimisticSide, Harry Porter, Greg Price, Jude Rich, segfault, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Fumiya Shigemitsu, Cam Tenny, tyfkda, Warren Toomey, Stephen Tu, Rafael Ubal, Amane Uehara, Pablo Ventura, Xi Wang, WaheedHafez, Keiichi Watanabe, Nicolas Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng, ZhUyU1997, and Zou Chang Wei.
The code in the files that constitute xv6 is Copyright 2006-2022 Frans Kaashoek, Robert Morris, and Russ Cox.
ERROR REPORTS
Please send errors and suggestions to Frans Kaashoek and Robert Morris (kaashoek,[email protected]). The main purpose of xv6 is as a teaching operating system for MIT's 6.1810, so we are more interested in simplifications and clarifications than new features.
BUILDING AND RUNNING XV6
You will need a RISC-V "newlib" tool chain from https://github.com/riscv/riscv-gnu-toolchain, and qemu compiled for riscv64-softmmu. Once they are installed, and in your shell search path, you can run "make qemu".