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* Change how unwind information is stored on Windows Unwind information on Windows is stored in two separate locations. The first location is the unwind information itself which corresponds to `UNWIND_INFO`. The second location is a list of `RUNTIME_INFO` structures which point to function bodes and `UNWIND_INFO` structures. Currently in Wasmtime the `UNWIND_INFO` structures are stored just after functions themselves with a somewhat cryptic comment indicating that Windows prefers this (I'm unsure as to the provenance of this comment). The `RUNTIME_INFO` data is then stored in a separate section which has the custom name of `_wasmtime_winx64_unwind`. After my recent foray into trying to debug windows-2022 bad unwind information again I realized though that Windows actually has official sections for these two unwind information items. The `.xdata` section is used to store the `UNWIND_INFO` structures and the `.pdata` section stores the `RUNTIME_INFO` list. To try to be somewhat idiomatic and perhaps one day even hook into standard Windows debugging tools I went ahead and refactored how our unwind information is stored to match this. Perhaps the main benefit of this is that it reduces the size of the read/execute section of the binary. Previously the unwind information was executable since it was stored in the `.text` section, but unnecessarily so. Now it's in a read-only section which is in theory a small amount of hardening. Otherwise though I don't think this will really help all that much to hook up in to standard debugging tools like `objdump` because it's all still stored in an ELF file rather than a COFF file. * Review comments
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's runtime is also optimized for cases such as efficient instantiation, low-overhead transitions between the embedder and wasm, and scalability of concurrent instances.
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Secure. Wasmtime's development is strongly focused on the correctness of its implementation with 24/7 fuzzing donated by Google's OSS Fuzz, leveraging Rust's API and runtime safety guarantees, careful design of features and APIs through an RFC process, a security policy in place for when things go wrong, and a release policy for patching older versions as well. We follow best practices for defense-in-depth and known 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. Wastime supports a rich set of APIs and build time configuration to provide many options such as further means of restricting WebAssembly beyond its basic guarantees such as its CPU and Memory consumption. Wasmtime also runs in tiny environments all the way up to massive servers with many concurrent instances.
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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 or usewasmtimeConan 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.