363cd2d20f
* Expose memory-related options in `Config` This commit was initially motivated by looking more into #1501, but it ended up balooning a bit after finding a few issues. The high-level items in this commit are: * New configuration options via `wasmtime::Config` are exposed to configure the tunable limits of how memories are allocated and such. * The `MemoryCreator` trait has been updated to accurately reflect the required allocation characteristics that JIT code expects. * A bug has been fixed in the cranelift wasm code generation where if no guard page was present bounds checks weren't accurately performed. The new `Config` methods allow tuning the memory allocation characteristics of wasmtime. Currently 64-bit platforms will reserve 6GB chunks of memory for each linear memory, but by tweaking various config options you can change how this is allocate, perhaps at the cost of slower JIT code since it needs more bounds checks. The methods are intended to be pretty thoroughly documented as to the effect they have on the JIT code and what values you may wish to select. These new methods have been added to the spectest fuzzer to ensure that various configuration values for these methods don't affect correctness. The `MemoryCreator` trait previously only allocated memories with a `MemoryType`, but this didn't actually reflect the guarantees that JIT code expected. JIT code is generated with an assumption about the minimum size of the guard region, as well as whether memory is static or dynamic (whether the base pointer can be relocated). These properties must be upheld by custom allocation engines for JIT code to perform correctly, so extra parameters have been added to `MemoryCreator::new_memory` to reflect this. Finally the fuzzing with `Config` turned up an issue where if no guard pages present the wasm code wouldn't correctly bounds-check memory accesses. The issue here was that with a guard page we only need to bounds-check the first byte of access, but without a guard page we need to bounds-check the last byte of access. This meant that the code generation needed to account for the size of the memory operation (load/store) and use this as the offset-to-check in the no-guard-page scenario. I've attempted to make the various comments in cranelift a bit more exhaustive too to hopefully make it a bit clearer for future readers! Closes #1501 * Review comments * Update a comment
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
-
Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.
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Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
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Configurable. Whether you need to precompile your wasm ahead of time, generate code blazingly fast with Lightbeam, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
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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 - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the wasmtime-go repository
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.