d3c463aac0
This change is a follow-on from #4515 to add the ability to configure the `differential` fuzz target by limiting which engines and modules are used for fuzzing. This is incredibly useful when troubleshooting, e.g., when an engine is more prone to failure, we can target that engine exclusively. The effect of this configuration is visible in the statistics now printed out from #4739. Engines are configured using the `ALLOWED_ENGINES` environment variable. We can either subtract from the set of allowed engines (e.g., `ALLOWED_ENGINES=-v8`) or build up a set of allowed engines (e.g., `ALLOWED_ENGINES=wasmi,spec`), but not both at the same time. `ALLOWED_ENGINES` only configures the left-hand side engine; the right-hand side is always Wasmtime. When omitted, `ALLOWED_ENGINES` defaults to [`wasmtime`, `wasmi`, `spec`, `v8`]. The generated WebAssembly modules are configured using `ALLOWED_MODULES`. This environment variables works the same as above but the available options are: [`wasm-smith`, `single-inst`].
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.