wasbox

This is a minimal and primitive WebAssembly virtual machine for running WASM modules in a sandboxed environment.

It is written from scratch in Rust and is designed to be as simple as possible, and to support a simplified API and workflow for some specific use cases I have in mind for my own projects.

In particular, I need a wasm runtime that can do the following for another project I'm working on:

• Be suspended and resumed at will, and the contents of stack frames easily serialized.
• Be Send across threads.
• Cooperate / interoperate with other VMs co-hosted in the same runtime
• Easily bind to native functions and other services within that runtime.
• Be easy to understand and modify by me.
• No fancy stuff with funky lifetimes, just simple code being simple and living the simple life.

I don't need it to be JIT-blazing fast, just reasonable. I don't need a pile of extensions yet. I don't need wasi and similar. I just want an embedded VM for running a subset of programs. And I banged my head against wasmtime and wasmer on and off for many months before just getting annoyed enough that I decided to try my hand at writing my own.

But you shouldn't use it. At least not yet.

status

It can currently do the following

• Decode (but not link or run) the entirety of the 'wast' test suite (see tests/testsuite) into a Module structure
• Scan and decode the core WASM opcodes into a set of stack-based VM opcodes.
• Execute said opcodes in stack frames that run against a Memory which is for now a statically sized (un growable) slice.
• Execute the above well enough to run the included itoa function in itoa.wat / itoa.wasm. Produces the expected results.

Notably missing (and this is just the start of the list):

• Import binding. And likely a pile of of "link" time features.
• Testing against anything other than "itoa". Will for sure fail on anything but the simplest programs right now as it likely has a pile of bugs
• Does not support vectors/simd, reference types, tables, GC extensions, etc. etc. etc.
• Optimization.

license

GPL 3.0.

Copyleft, free software.

If you want (for some crazy reason) to use this, you can, but you have to share your changes.