This commit removes the binaryen support for fuzzing from wasmtime, instead switching over to `wasm-smith`. In general it's great to have what fuzzing we can, but our binaryen support suffers from a few issues: * The Rust crate, binaryen-sys, seems largely unmaintained at this point. While we could likely take ownership and/or send PRs to update the crate it seems like the maintenance is largely on us at this point. * Currently the binaryen-sys crate doesn't support fuzzing anything beyond MVP wasm, but we're interested at least in features like bulk memory and reference types. Additionally we'll also be interested in features like module-linking. New features would require either implementation work in binaryen or the binaryen-sys crate to support. * We have 4-5 fuzz-bugs right now related to timeouts simply in generating a module for wasmtime to fuzz. One investigation along these lines in the past revealed a bug in binaryen itself, and in any case these bugs would otherwise need to get investigated, reported, and possibly fixed ourselves in upstream binaryen. Overall I'm not sure at this point if maintaining binaryen fuzzing is worth it with the advent of `wasm-smith` which has similar goals for wasm module generation, but is much more readily maintainable on our end. Additonally in this commit I've added a fuzzer for wasm-smith's `SwarmConfig`-based fuzzer which should expand the coverage of tested modules. Closes #2163
Fuzzing Infrastructure for Wasmtime
This crate provides test case generators and oracles for use with fuzzing.
These generators and oracles are generally independent of the fuzzing engine
that might be using them and driving the whole fuzzing process (e.g. libFuzzer
or AFL). As such, this crate does not contain any actual fuzz targets
itself. Those are generally just a couple lines of glue code that plug raw input
from (for example) libFuzzer into a generator, and then run one or more
oracles on the generated test case.
If you're looking for the actual fuzz target definitions we currently have, they
live in wasmtime/fuzz/fuzz_targets/* and are driven by cargo fuzz and
libFuzzer.