62c5af68b5
* components: Limit the recursive size of types in Wasmtime This commit is aimed at fixing #4814 by placing a hard limit on the maximal recursive depth a type may have in the component model. The component model theoretically allows for infinite recursion but many various types of operations within the component model are naturally written as recursion over the structure of a type which can lead to stack overflow with deeply recursive types. Some examples of recursive operations are: * Lifting and lowering a type - currently the recursion here is modeled in Rust directly with `#[derive]` implementations as well as the implementations for the `Val` type. * Compilation of adapter trampolines which iterates over the type structure recursively. * Historically many various calculations like the size of a type, the flattened representation of a type, etc, were all done recursively. Many of these are more efficiently done via other means but it was still natural to implement these recursively initially. By placing a hard limit on type recursion Wasmtime won't be able to load some otherwise-valid modules. The hope, though, is that no human-written program is likely to ever reach this limit. This limit can be revised and/or the locations with recursion revised if it's ever reached. The implementation of this feature is done by generalizing the current flattened-representation calculation which now keeps track of a type's depth and size. The size calculation isn't used just yet but I plan to use it in fixing #4816 and it was natural enough to write here as well. The depth is checked after a type is translated and if it exceeds the maximum then an error is returned. Additionally the `Arbitrary for Type` implementation was updated to prevent generation of a type that's too-recursive. Closes #4814 * Remove unused size calculation * Bump up just under the limit
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
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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.
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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.
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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.
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WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
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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.