7717d8fa55
* wiggle: adapt Wiggle guest slices for `unsafe` shared use When multiple threads can concurrently modify a WebAssembly shared memory, the underlying data for a Wiggle `GuestSlice` and `GuestSliceMut` could change due to access from other threads. This breaks Rust guarantees when `&[T]` and `&mut [T]` slices are handed out. This change modifies `GuestPtr` to make `as_slice` and `as_slice_mut` return an `Option` which is `None` when the underlying WebAssembly memory is shared. But WASI implementations still need access to the underlying WebAssembly memory, both to read to it and write from it. This change adds new APIs: - `GuestPtr::to_vec` copies the bytes from WebAssembly memory (from which we can safely take a `&[T]`) - `GuestPtr::as_unsafe_slice_mut` returns a wrapper `struct` from which we can `unsafe`-ly return a mutable slice (users must accept the unsafety of concurrently modifying a `&mut [T]`) This approach allows us to maintain Wiggle's borrow-checking infrastructure, which enforces the guarantee that Wiggle will not modify overlapping regions, e.g. This is important because the underlying system calls may expect this. Though other threads may modify the same underlying region, this is impossible to prevent; at least Wiggle will not be able to do so. Finally, the changes to Wiggle's API are propagated to all WASI implementations in Wasmtime. For now, code locations that attempt to get a guest slice will panic if the underlying memory is shared. Note that Wiggle is not enabled for shared memory (that will come later in something like #5054), but when it is, these panics will be clear indicators of locations that must be re-implemented in a thread-safe way. * review: remove double cast * review: refactor to include more logic in 'UnsafeGuestSlice' * review: add reference to #4203 * review: link all thread-safe WASI fixups to #5235 * fix: consume 'UnsafeGuestSlice' during conversion to safe versions * review: remove 'as_slice' and 'as_slice_mut' * review: use 'as_unsafe_slice_mut' in 'to_vec' * review: add `UnsafeBorrowResult`
wasi-common
A Bytecode Alliance project
A library providing a common implementation of WASI hostcalls for re-use in any WASI-enabled runtime.
The wasi-common crate will ultimately serve as a library providing a common implementation of
WASI hostcalls for re-use in any WASI (and potentially non-WASI) runtimes
such as Wasmtime and Lucet.
The library is an adaption of lucet-wasi crate from the Lucet project, and it is currently based on 40ae1df git revision.
Please note that the library requires Rust compiler version at least 1.37.0.
Supported syscalls
*nix
In our *nix implementation, we currently support the entire WASI API
with the exception of the proc_raise hostcall, as it is expected to
be dropped entirely from WASI.
Windows
In our Windows implementation, we currently support the minimal subset of WASI API which allows for running the very basic "Hello world!" style WASM apps. More coming shortly, so stay tuned!
Development hints
When testing the crate, you may want to enable and run full wasm32 integration testsuite. This
requires wasm32-wasi target installed which can be done as follows using rustup
rustup target add wasm32-wasi
Now, you should be able to run the integration testsuite by running cargo test on the
test-programs package with test-programs/test_programs feature enabled:
cargo test --features test-programs/test_programs --package test-programs