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bytecodealliance / lucet

Lucet, the Sandboxing WebAssembly Compiler.
Apache License 2.0
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Add differential fuzzing between old and new Cranelift backends. #617

Closed cfallin closed 3 years ago

cfallin commented 3 years ago

This PR adds a fuzz target runnable via cargo-fuzz (with libFuzzer) that builds an arbitrary Wasm module, produced by wasm-smith, with lucetc using both the old and new Cranelift x86-64 backends. It then instantiates both and invokes the start function in both, comparing the global values and heap contents after the call returns.

The intent of this differential fuzzing is to validate that the new backend works as well as the old one for the purposes of Lucet.

This change pulls in a new version of wasmtime and fixes a few small issues (panics that should be errors) that the fuzzing immediately discovered.

cfallin commented 3 years ago

Should be ready for review now (sorry for churn) -- verified that this is doing interesting things locally, with coverage across old/new backend.