833ebeed76
This patch makes spillslot allocation, spilling and reloading all based on register class only. Hence when we have a 32- or 64-bit value in a 128-bit XMM register on x86-64 or vector register on aarch64, this results in larger spillslots and spills/restores. Why make this change, if it results in less efficient stack-frame usage? Simply put, it is safer: there is always a risk when allocating spillslots or spilling/reloading that we get the wrong type and make the spillslot or the store/load too small. This was one contributing factor to CVE-2021-32629, and is now the source of a fuzzbug in SIMD code that puns an arbitrary user-controlled vector constant over another stackslot. (If this were a pointer, that could result in RCE. SIMD is not yet on by default in a release, fortunately. In particular, we have not been particularly careful about using moves between values of different types, for example with `raw_bitcast` or with certain SIMD operations, and such moves indicate to regalloc.rs that vregs are in equivalence classes and some arbitrary vreg in the class is provided when allocating the spillslot or spilling/reloading. Since regalloc.rs does not track actual type, and since we haven't been careful about moves, we can't really trust this "arbitrary vreg in equivalence class" to provide accurate type information. In the fix to CVE-2021-32629 we fixed this for integer registers by always spilling/reloading 64 bits; this fix can be seen as the analogous change for FP/vector regs.
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.
-
Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
-
Configurable. Whether you need to precompile your wasm ahead of time, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
-
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 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.