10dbb19983
* Improve wasmi differential fuzzer * Support modules with a `start` function * Implement trap-matching to ensure that wasmi and Wasmtime both report the same flavor of trap. * Support differential fuzzing where no engines match Locally I was attempting to run against just one wasm engine with `ALLOWED_ENGINES=wasmi` but the fuzzer quickly panicked because the generated test case didn't match wasmi's configuration. This commit updates engine-selection in the differential fuzzer to return `None` if no engine is applicable, throwing out the test case. This won't be hit at all with oss-fuzz-based runs but for local runs it'll be useful to have. * Improve proposal support in differential fuzzer * De-prioritize unstable wasm proposals such as multi-memory and memory64 by making them more unlikely with `Unstructured::ratio`. * Allow fuzzing multi-table (reference types) and multi-memory by avoiding setting their maximums to 1 in `set_differential_config`. * Update selection of the pooling strategy to unconditionally support the selected module config rather than the other way around. * Improve handling of traps in differential fuzzing This commit fixes an issue found via local fuzzing where engines were reporting different results but the underlying reason for this was that one engine was hitting stack overflow before the other. To fix the underlying issue I updated the execution to check for stack overflow and, if hit, it discards the entire fuzz test case from then on. The rationale behind this is that each engine can have unique limits for stack overflow. One test case I was looking at for example would stack overflow at less than 1000 frames with epoch interruption enabled but would stack overflow at more than 1000 frames with it disabled. This means that the state after the trap started to diverge and it looked like the engines produced different results. While I was at it I also improved the "function call returned a trap" case to compare traps to make sure the same trap reason popped out. * Fix fuzzer tests
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
Guide | Contributing | Website | Chat
Installation
The Wasmtime CLI can be installed on Linux and macOS with a small install script:
curl https://wasmtime.dev/install.sh -sSf | bash
Windows or otherwise interested users can download installers and binaries directly from the GitHub Releases page.
Example
If you've got the Rust compiler installed then you can take some Rust source code:
fn main() {
println!("Hello, world!");
}
and compile/run it with:
$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!
Features
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code either at runtime or ahead-of-time. Wasmtime is optimized for efficient instantiation, low-overhead calls between the embedder and wasm, and scalability of concurrent instances.
-
Secure. Wasmtime's development is strongly focused on correctness and security. Building on top of Rust's runtime safety guarantees, each Wasmtime feature goes through careful review and consideration via an RFC process. Once features are designed and implemented, they undergo 24/7 fuzzing donated by Google's OSS Fuzz. As features stabilize they become part of a release, and when things go wrong we have a well-defined security policy in place to quickly mitigate and patch any issues. We follow best practices for defense-in-depth and integrate protections and mitigations for issues like Spectre. Finally, we're working to push the state-of-the-art by collaborating with academic researchers to formally verify critical parts of Wasmtime and Cranelift.
-
Configurable. Wasmtime uses sensible defaults, but can also be configured to provide more fine-grained control over things like CPU and memory consumption. Whether you want to run Wasmtime in a tiny environment or on massive servers with many concurrent instances, we've got you covered.
-
WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
-
Standards Compliant. Wasmtime passes the official WebAssembly test suite, implements the official C API of wasm, and implements future proposals to WebAssembly as well. Wasmtime developers are intimately engaged with the WebAssembly standards process all along the way too.
Language Support
You can use Wasmtime from a variety of different languages through embeddings of the implementation:
- Rust - the
wasmtimecrate - C - the
wasm.h,wasi.h, andwasmtime.hheaders, CMake orwasmtimeConan package - C++ - the
wasmtime-cpprepository or usewasmtime-cppConan package - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the
wasmtime-gorepository
Documentation
📚 Read the Wasmtime guide here! 📚
The wasmtime guide is the best starting point to learn about what Wasmtime can do for you or help answer your questions about Wasmtime. If you're curious in contributing to Wasmtime, it can also help you do that!
It's Wasmtime.