c9a0ba81a0
* Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I've tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they're interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they've run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they're out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It's intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don't work when you're interrupting host code, so if you've got a host import blocking for a long time an interrupt won't actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn't handled by hitting the guard page, but rather it's explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don't use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
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.