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diff --git a/third_party/rust/wasm-smith/README.md b/third_party/rust/wasm-smith/README.md new file mode 100644 index 0000000000..720472ebb6 --- /dev/null +++ b/third_party/rust/wasm-smith/README.md @@ -0,0 +1,101 @@ +# `wasm-smith` + +**A WebAssembly test case generator.** + +[](https://docs.rs/wasm-smith/) +[](https://crates.io/crates/wasm-smith) +[](https://crates.io/crates/wasm-smith) + + +* [Features](#features) +* [Usage](#usage) + * [With `cargo fuzz` and `libfuzzer-sys`](#with-cargo-fuzz-and-libfuzzer-sys) + * [As a Command Line Tool](#as-a-command-line-tool) + +## Features + +* **Always valid:** All generated Wasm modules pass validation. `wasm-smith` + gets past your wasm parser and validator, exercising the guts of your Wasm + compiler, runtime, or tool. + +* **Supports the full WebAssembly language:** Doesn't have blind spots or + unimplemented instructions. + +* **Implements the + [`Arbitrary`](https://docs.rs/arbitrary/*/arbitrary/trait.Arbitrary.html) + trait**: Easy to use with [`cargo + fuzz`](https://github.com/rust-fuzz/cargo-fuzz) and + [`libfuzzer-sys`](https://github.com/rust-fuzz/libfuzzer)! + +* **Deterministic:** Given the same input seed, always generates the same output + Wasm module, so you can always reproduce test failures. + +* **Plays nice with mutation-based fuzzers:** Small changes to the input tend to + produce small changes to the output Wasm module. Larger inputs tend to + generate larger Wasm modules. + +## Usage + +### With `cargo fuzz` and `libfuzzer-sys` + +First, use `cargo fuzz` to define a new fuzz target: + +```shell +$ cargo fuzz add my_wasm_smith_fuzz_target +``` + +Next, add `wasm-smith` to your dependencies: + +```shell +$ cargo add wasm-smith +``` + +Then, define your fuzz target so that it takes arbitrary `wasm_smith::Module`s +as an argument, convert the module into serialized Wasm bytes via the `to_bytes` +method, and then feed it into your system: + +```rust +// fuzz/fuzz_targets/my_wasm_smith_fuzz_target.rs + +#![no_main] + +use libfuzzer_sys::fuzz_target; +use wasm_smith::Module; + +fuzz_target!(|module: Module| { + let wasm_bytes = module.to_bytes(); + + // Your code here... +}); +``` + +Finally, start fuzzing: + +```shell +$ cargo fuzz run my_wasm_smith_fuzz_target +``` + +> **Note:** Also check out [the `validate` fuzz +> target](https://github.com/fitzgen/wasm-smith/blob/main/fuzz/fuzz_targets/validate.rs) +> defined in this repository. Using the `wasmparser` crate, it checks that every +> module generated by `wasm-smith` validates successfully. + +### As a Command Line Tool + +Install the CLI tool via `cargo`: + +```shell +$ cargo install wasm-tools +``` + +Convert some arbitrary input into a valid Wasm module: + +```shell +$ head -c 100 /dev/urandom | wasm-tools smith -o test.wasm +``` + +Finally, run your tool on the generated Wasm module: + +```shell +$ my-wasm-tool test.wasm +``` |