cranelift

rust jit wasm webassembly runtime wasi cranelift sandbox wasmtime

Alex Crichton 550a16f539 Fix a soundness issue with the component model and async (#6509 ) * Force `execute_across_threads` to use multiple threads Currently this uses tokio's `spawn_blocking` but that will reuse threads in its thread pool. Instead spawn a thread and perform a single poll on that thread to force lots of fresh threads to be used and ideally stress TLS management further. * Add a guard against using stale stacks This commit adds a guard to Wasmtime's async support to double-check that when a call to `poll` is finished that the currently active TLS activation pointer does not point to the stack that is being switched off of. This is attempting to be a bit of a defense-in-depth measure to prevent stale pointers from sticking around in TLS. This is currently happening and causing #6493 which can result in unsoundness but currently is manifesting as a crash. * Fix a soundness issue with the component model and async This commit addresses #6493 by fixing a soundness issue with the async implementation of the component model. This issue has been presence since the inception of the addition of async support to the component model and doesn't represent a recent regression. The underlying problem is that one of the base assumptions of the trap handling code is that there's only one single activation in TLS that needs to be pushed/popped when a stack is switched (e.g. a fiber is switched to or from). In the case of the component model there might be two activations: one for an invocation of a component function and then a second for an invocation of a `realloc` function to return results back to wasm (e.g. in the case an imported function returns a list). This problem is fixed by changing how TLS is managed in the presence of fibers. Previously when a fiber was suspended it would pop a single activation from the top of the stack and save that to get pushed when the fiber was resumed. This has the benefit of maintaining an entire linked list of activations for the current thread but has the problem above where it doesn't handle a fiber with multiple activations on it. Instead now TLS management is done when a fiber is resumed instead of suspended. Instead of pushing/popping a single activation the entire linked list of activations is tracked for a particular fiber and stored within the fiber itself. In this manner resuming a fiber will push all activations onto the current thread and suspending a fiber will pop all activations for the fiber (and store them as a new linked list in the fiber's state itself). This end result is that all activations on a fiber should now be managed correctly, regardless of how many there are. The main downside of this commit is that fiber suspension and resumption is more complicated, but the hope there is that fiber suspension typically corresponds with I/O not being ready or similar so the order of magnitude of TLS operations isn't too significant compared to the I/O overhead. Closes #6493 * Review comments * Fix restoration during panic		1 year ago
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src	Fix a soundness issue with the component model and async (#6509)	1 year ago
Cargo.toml	Refactor test-programs to build modules and components (#6385)	1 year ago
LICENSE	Add license files	3 years ago
build.rs	Add rerun-if-changed to fiber/build.rs (#4377)	2 years ago