azey.net

An experimental Unix-like operating system written entirely in pure static frameworkless browser Javascript, complete with a kernel and userspace!

Science isn't about WHY. It's about WHY NOT!
~ Cave Johnson

Currently implemented features:

• a bootloader - doesn't do much except show a selection menu and import() the kernel
• a fully functional monolithic kernel including drivers, process management, TTYs, all that good stuff
• a userspace consisting of a libc-like libjs, init, getty, a shell and a few basic commands

azix kernel

Now, I know what you're thinking. "A kernel, written in javascript? For a website? What? Why? What? Are you high?" To the last question: No, unfortunately I wrote this fully conscious and of my own free will. As for the others, honestly, I have no idea. See Cave Johnson quote at the top of the README.

You can find the source code in static/boot/kernels/azix. Might make it a separate repo and include it here as a submodule eventually.

Features:

• a single-root node graph VFS layer
• modular drivers taking the "everything is a file" philosophy to its logical conclusion - all drivers are implemented as mountable filesystems
  • a read-only httpfs filesystem that mounts the webroot at /, with read() implemented using fetch()
    • assumes that the server serves an autoindex on /<path>/__autoindex.json, since the alternative is just fuzzing the site and that seems a bit excessive for ls
  • a tmpfs filesystem mounted in /dev, mostly for other device drivers
  • an input driver mounted as a file at /dev/input, buffers JS keydown events
  • a domfs (HTML DOM, don't get excited) driver mounted at /dev/dom for graphical output, replaces traditional VGA drivers
  • 8 (by default) TTYs mounted at /dev/ttyN, with each mount corresponding to 1 TTY (except for tty0, which is the currently focused TTY). Processes /dev/input, also handles line discipline using kernel functions (see tty.js). Uses input & domfs.
  • TODO: PTY driver mounted at /dev/pts, handles line discipline & links /dev/pts/N with a /dev/pts/ptmx file descriptor, inspired by the Linux implementation
  • a ttyctl driver mounted at /dev/tty, exposes several files for TTY control:
    • ctty: get/set the current process' controlling TTY
    • pgid: get/set TTY's foreground process group
    • ldisc: get/set TTY's line discipline (n_tty, n_echo or n_null)
  • a pipe driver, mounting it creates a named FIFO; also used by the pipe() syscall
  • a localfs driver using JS localStorage mounted in /etc and /root - with an /etc/fstab actually used on "boot" by the init program and /root/.azsh_history used for shell history
• process management
  • each process is a web worker, started from a createObjectURL blob read from the filesystem
  • job control, setsid() and setpgid()
  • signals
  • syscalls (see docs/SYSCALL.md for full list)
    • tried to use as few as possible, very much inspired by Plan9
    • to make a syscall, a process (web worker) calls postMessage and then Atomics.waits on a shared array buffer, which then contains the syscall's return value
    • read() and other calls that return strings take a SharedArrayBuffer and length as arguments, C function-like

Userspace

The kernel/userpace separation is implemented using web workers with postMessage+SharedArrayBuffer+Atomics imitating syscalls, because, yknow, why not. Args and env vars are transferred right after process creation in a postMessage.

Current features:

• a libc-like library in /lib/libjs
  • handles the initial setup, incl. waiting for args+env before running the program and setting up standard i/o streams
  • streams! including buffering and all the familiar fwrite, fflush, setvbuf etc functions, most implementations stolen from inspired by musl
  • a few miscellaneous C-like functions like getopt
• a few basic binaries in /bin
  • init.js - started by the kernel, runs getty.js on all TTYs
  • getty.js - prints welcome message and starts shell in a loop
  • sh.js - a barely-interactive proof of concept shell using canonical TTY line discipline without job control, comparable to dash
  • azsh.js - a more advanced and generally much nicer shell using raw TTY ldisc, visuals inspired by fish
    • includes piping and file redirection support, history and pretty colors TODO
  • a bunch of coreutils: head, tail, cat, rm, echo, ls, mount, etc.

TODO