Wnix

DISCLAIMER: this project is in early stage development, and therefore not suitable for production environments.

Wnix (pronounced woo-nix or double u-nix) is a small, Unix-like operating system aimed towards resource-constrained devices without a MMU. Virtual memory semantics are instead achieved by exclusively running WebAssembly applications on its userspace, using the small and flexible interpreter NanoWasm as its backend.

For the sake of simplicity, and as opposed to most operating systems, Wnix only requires one execution thread to perform all tasks. In other words, Wnix is highly concurrent, but not parallel, and relies entirely on co-operative execution of asynchronous (i.e., fast) tasks to achieve concurrency.

Note: while designed to remain portable, Wnix currently only targets the original PlayStation.

Dependencies

A mipsel-unknown-elf cross-toolchain (i.e., GNU binutils and GCC). Here are some notes to build it from source.
clang-18
libclang-18-dev
Copy libclang_rt.builtins-wasm32.a (get from WASI-SDK) to /usr/lib/llvm-18/lib/clang/18/lib.
C and C++ compilers for the host platform.

How to build

Configure with:

cmake -B build -DCMAKE_TOOLCHAIN_FILE=cmake/ps1-toolchain.cmake -DVIDEO_MODE=VMODE_PAL

Build with:

cmake --build build/ # Optionally, add -j$(nproc)

FAQ

Why not a fully-fledged operating system like GNU/Linux or BSDs?

While all these projects truly deserve uttermost respect, these are very complex projects that target a diverse range of highly sophisticated hardware.

More specifically, regarding the original PlayStation there have been several unsuccessful attempts at running ancient versions of the Linux kernel (circa 2.4), with concerns about newer versions not being able to fit into the console's 2 MiB RAM.

On the other hand, kernels like Linux are focused on running native executables (i.e., ELF files), where the semantics provided by MMUs would not be available on limited hardware like the original PlayStation. While it might still be possible to configure Linux to exclusively run WebAssembly applications somehow, Linux is still a very large and complex project that would require a big effort to port to a PlayStation.

Since binary compatibility with existing Linux software is not a requirement, a simple operating system with Unix-like semantics is enough to allow WebAssembly applications to interact with the system via WASI.

Moreover, not having a MMU available would typically mean executables would be dumped to RAM before execution, with a non-negligible footprint. On the other hand, NanoWasm is designed to allow direct execution from any source, including read-only media like CD-ROMs.

Similarly, NanoWasm allows to allocate and manipulate WebAssembly memories (linear memory, stack, etc.) from any source, including but not limited to memory cards or any other external mass storage, therefore allowing the system to outgrow its RAM size limitations, similarly to how fully-fledged operating systems like GNU/Linux implement virtual memory.

More importantly, running userspace applications without a MMU would allow a malicious application to read/write memory from/to other processes, or even the kernel itself. Confining userspace applications into a sandbox can be achieved via WebAssembly, a bytecode representation that can be easily compiled down to from popular programming languages, such as C or C++, via [wasi-sdk].

Of course, the design decisions above were made with memory efficiency and security in mind, at the cost of execution speed. Wnix is meant to provide similar tools compared to fully-fledged operating systems, at a fraction of their size.

And last, but not least, Wnix was written as an attempt to learn about operating systems in general, and a way to have fun while implementing interesting ways to achieve virtual memory semantics and concurrency by software.

License

wnix, a Unix-like operating system for WebAssembly applications.
Copyright (C) 2025  Xavier Del Campo Romero

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.

Wnix includes source code from other projects under various free software licenses. Unless explicitly noted otherwise, Wnix is licensed according to LICENSE.

Disclaimer

Linux is a registered trademark of Linus Torvalds.
PlayStation is a registered trademark of its respective owners.
Unix is a registered trademark of its respective owners.