VIMIX OS Readme

VIMIX OS is a small Unix like OS which started as a fork of xv6 (which is a partial re-implementation of Unix version 6 for RISC V 32 and 64-bit).

See contributors for original xv6 contributors and authors of other 3rd party components.

Quick Links

Compile and try out:

• Build requirements and instructions.
• How to run on qemu.
• Overview of the directories.
• The kernel.
• The user space.

How it looks like (text mode via UART only) running on qemu:

init device riscv,plic0... OK (8,0)
init device ns16550a... OK (13,0)

VIMIX OS 64 bit (RISC V) kernel version 36bb03d is booting
Console: ns16550a
Timer source: sstc extension
init memory management...
init process and syscall support...
init filesystem...
init remaining devices...
init device /dev/null... OK (3,0)
init device /dev/zero... OK (4,0)
init device /dev/random... OK (10,0)
init device google,goldfish-rtc... OK (6,0)
init device syscon... OK (7,0)
init device virtio,mmio... OK (1,0)
init device virtio,mmio... OK (1,1)
fs root device: virtio,mmio (1,0)
SBI implementation: OpenSBI (version 65541)
SBI specification: v2.0
SBI extension SRST detected: register SBI reboot/shutdown functions
init userspace...
CPU 0 starting 
CPU 2 starting 
CPU 3 starting 
CPU 1 starting (boot CPU)
forkret() mounting /... OK
forkret() loading /usr/bin/init... OK
init mounting /dev... OK
init mounting /sys... OK
init mounting /home... OK
init starting /usr/bin/sh
$ ls /
/:
drwxr-xr-x root root     1024 B  2.11.2025  19:48:58 .
drwxr-xr-x root root     1024 B  2.11.2025  19:48:58 ..
.rw-r--r-- root root     5911 B  2.11.2025  19:43:25 README.md
drwxr-xr-x root root        0 B  2.11.2025  19:48:58 dev
drwxr-xr-x root root     5120 B  1.11.2025  12:38:22 etc
drwxr-xr-x root root      256 B  2.11.2025  09:34:08 home
drwxr-x--- root root      128 B  19.10.2025 08:45:18 root
drwxr-xr-x root root        0 B  2.11.2025  19:48:58 sys
drwxr-xr-x root root     7168 B  26.10.2025 16:43:02 tests
drwxrwxrwt root root      128 B  31.10.2025 23:16:27 tmp
drwxr-xr-x root root      256 B  31.10.2025 21:40:22 usr
$ cat /README.md | grep RISC | wc
4 78 607 
$ fortune
I'd spell creat with an e. - Ken Thompson when asked what he would do differently if he were to redesign UNIX
$ 

Changes from xv6

• Added documentation in docs.
• Cleanups: Reorganized code, separate headers, renamed many functions and variables, using stdint types, general refactoring, reduced number of GOTOs, ...
• Support 32-bit RISC V (in addition to 64-bit), both booting in M-mode and S-mode in a SBI environment. Inspired by a 32-bit xv6 port by Michael Schröder (https://github.com/x653/xv6-riscv-fpga/tree/main/xv6-riscv).
• The user space tries to mimics a real UNIX. Some apps can get compiled unchanged for Linux too.
• Changed memory map; app stacks grow dynamically.
• Added applications:
  • stat, shutdown, mknod, date, sleep, rmdir, cp, mount, umount, fortune, wumpus, time, which, meminfo, fsinfo, statvfs, fsbench, chown, chmod, id, login, su
• Added syscalls:
  • get_dirent
  • reboot
  • clock_gettime
  • lseek
  • split unlink() into unlink and rmdir
  • mount and umount
  • statvfs
  • truncate
  • chown and chmod
  • getresgid / getresuid
  • setuid / setgid / setresgid / setresuid
  • fstat
  • umask
• Support multiple devices, not just two hard coded ones.
• Added devices:
  • /dev/null, /dev/zero, /dev/random
  • ramdisk
  • jh7110 temperature sensor
• The file system was changed to store more meta data and support larger files. It was also moved behind a virtual file system abstraction.
• Parse the device tree at boot.
• Added /dev as a special file system exposing all devices.
• Added /sys as a special file system exposing various kernel objects.
• Boot in M-mode now mimics SBI to the S-mode kernel.
• Added a buddy allocator. kmalloc() now supports smaller allocations of one page via a slab allocator (see memory_management).
• Added Inter Processor Interrupts.