# xv6

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.

## Testing

The makefile exposes several targets inspired by FreeBSD: kernel, world and fs.img

```bash
make -j$(nproc) kernel
make -j$(nproc) world
make -j$(nproc) fs.img
```

To do everything in one sweep:
```bash
make -j$(nproc) qemu
```

## Dependencies

    - Qemu (RV)
    - Make (GNU variant)
    - GCC (RV)
    - clang-format (optional)

<details>
    <summary>Fedora</summary>

    Only essentials:
    sudo dnf install make qemu-system-riscv gcc-riscv64-linux-gnu clang-format

    Alternatively, if you want all "batteries included":
    sudo dnf group install "C Development Tools and Libraries" "Development Tools"

</details>

## From upstream readme:

> 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,rtm@mit.edu).  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".