4376cf2609
* Add differential fuzzing against V8 This commit adds a differential fuzzing target to Wasmtime along the lines of the wasmi and spec interpreters we already have, but with V8 instead. The intention here is that wasmi is unlikely to receive updates over time (e.g. for SIMD), and the spec interpreter is not suitable for fuzzing against in general due to its performance characteristics. The hope is that V8 is indeed appropriate to fuzz against because it's naturally receiving updates and it also is expected to have good performance. Here the `rusty_v8` crate is used which provides bindings to V8 as well as precompiled binaries by default. This matches exactly the use case we need and at least for now I think the `rusty_v8` crate will be maintained by the Deno folks as they continue to develop it. If it becomes an issue though maintaining we can evaluate other options to have differential fuzzing against. For now this commit enables the SIMD and bulk-memory feature of fuzz-target-generation which should enable them to get differentially-fuzzed with V8 in addition to the compilation fuzzing we're already getting. * Use weak linkage for GDB jit helpers This should help us deduplicate our symbol with other JIT runtimes, if any. For now this leans on some C helpers to define the weak linkage since Rust doesn't support that on stable yet. * Don't use rusty_v8 on MinGW They don't have precompiled libraries there. * Fix msvc build * Comment about execution
cargo fuzz Targets for Wasmtime
This crate defines various libFuzzer
fuzzing targets for Wasmtime, which can be run via cargo fuzz.
These fuzz targets just glue together pre-defined test case generators with
oracles and pass libFuzzer-provided inputs to them. The test case generators and
oracles themselves are independent from the fuzzing engine that is driving the
fuzzing process and are defined in wasmtime/crates/fuzzing.
Example
To start fuzzing run the following command, where $MY_FUZZ_TARGET is one of
the available fuzz targets:
cargo fuzz run $MY_FUZZ_TARGET
Available Fuzz Targets
At the time of writing, we have the following fuzz targets:
compile: Attempt to compile libFuzzer's raw input bytes with Wasmtime.instantiate: Attempt to compile and instantiate libFuzzer's raw input bytes with Wasmtime.instantiate_translated: Pass libFuzzer's input bytes towasm-opt -ttfto generate a random, valid Wasm module, and then attempt to instantiate it.
The canonical list of fuzz targets is the .rs files in the fuzz_targets
directory:
ls wasmtime/fuzz/fuzz_targets/
Corpora
While you can start from scratch, libFuzzer will work better if it is given a corpus of seed inputs to kick start the fuzzing process. We maintain a corpus for each of these fuzz targets in a dedicated repo on github.
You can use our corpora by cloning it and placing it at wasmtime/fuzz/corpus:
git clone \
https://github.com/bytecodealliance/wasmtime-libfuzzer-corpus.git \
wasmtime/fuzz/corpus