This repository demonstrates the use of the POSIX virtual memory API to map externally allocated buffers into multiple separate WebAssembly processes.
Three implementations are included: a simple terminal-based one in C and a GTK "game" in both C and Rust. In all three, a host process creates two shared memory buffers then forks two container processes which embed a wasm engine to execute separate wasm modules. The containers map the shared buffers into the wasm linear memory, one with read-only and one with read-write flags.
The C implementations use
wasm-micro-runtime
and the Rust one uses wasmi.
The terminal implementation performs some basic memory checks and confirms cross-process interaction via the buffers.
The GTK implementations presents a grid field with actors controlled by the wasm modules: a "hunter" that chases some "runners". The hunter is controlled by one wasm instance and the runners by the other. The grid data is held in the read-only shared buffer (initialised by the host) while the actor coordinates are in the read-write one.
The GTK interface has a couple of buttons to show the memory protection at work. One instructs the host process to update the read-only buffer (to which it has write access) and modify the grid. The other instructs the hunter container process to do the same, at which point it will crash.