Wasmgrind

In this book we present Wasmgrind, an analysis framework and runtime for multithreaded WebAssembly programs written in Rust.

What Wasmgrind Is for

With the threads-proposal of WebAssembly being implemented in most modern browser and native runtimes concurrent access of memory regions as well as the implementation of synchronization primitives like mutexes became possible.

However, at the time of this writing there is no standardized way of creating and joining threads from within WebAssembly. Because of this, its currently quite difficult and error prone to write multithreaded programs in WebAssembly inducing the need for a convenient way to write, run and test multithreaded programs - ideally in a platform independent way.

The Core Features of Wasmgrind

Wasmgrind tries to fullfill the above needs by providing two mostly independent core utilities.

Execution of Multithreaded WebAssembly Programs

Currently, Wasmgrind implements a subset of the WebAssembly Linux Interface (WALI) to enable execution of various multithreaded programs that have been compiled using the WALI Toolchain.

Creation of Execution Traces

In order to identify common concurrency bugs like dataraces or deadlocks, Wasmgrind offers the ability to record important events like operations on mutexes, creation and joining of threads as well as memory accesses during program execution for offline analysis. It uses binary instrumentation to patch the binary before execution.