wasmtime/runtime/func.rs
1use crate::prelude::*;
2use crate::runtime::Uninhabited;
3use crate::runtime::vm::{
4 ExportFunction, InterpreterRef, SendSyncPtr, StoreBox, VMArrayCallHostFuncContext,
5 VMCommonStackInformation, VMContext, VMFuncRef, VMFunctionImport, VMOpaqueContext,
6 VMStoreContext,
7};
8use crate::store::{AutoAssertNoGc, StoreId, StoreOpaque};
9use crate::type_registry::RegisteredType;
10use crate::{
11 AsContext, AsContextMut, CallHook, Engine, Extern, FuncType, Instance, ModuleExport, Ref,
12 StoreContext, StoreContextMut, Val, ValRaw, ValType,
13};
14use alloc::sync::Arc;
15use core::ffi::c_void;
16use core::mem::{self, MaybeUninit};
17use core::ptr::NonNull;
18#[cfg(feature = "async")]
19use core::{future::Future, pin::Pin};
20use wasmtime_environ::VMSharedTypeIndex;
21
22/// A reference to the abstract `nofunc` heap value.
23///
24/// The are no instances of `(ref nofunc)`: it is an uninhabited type.
25///
26/// There is precisely one instance of `(ref null nofunc)`, aka `nullfuncref`:
27/// the null reference.
28///
29/// This `NoFunc` Rust type's sole purpose is for use with [`Func::wrap`]- and
30/// [`Func::typed`]-style APIs for statically typing a function as taking or
31/// returning a `(ref null nofunc)` (aka `Option<NoFunc>`) which is always
32/// `None`.
33///
34/// # Example
35///
36/// ```
37/// # use wasmtime::*;
38/// # fn _foo() -> Result<()> {
39/// let mut config = Config::new();
40/// config.wasm_function_references(true);
41/// let engine = Engine::new(&config)?;
42///
43/// let module = Module::new(
44/// &engine,
45/// r#"
46/// (module
47/// (func (export "f") (param (ref null nofunc))
48/// ;; If the reference is null, return.
49/// local.get 0
50/// ref.is_null nofunc
51/// br_if 0
52///
53/// ;; If the reference was not null (which is impossible)
54/// ;; then raise a trap.
55/// unreachable
56/// )
57/// )
58/// "#,
59/// )?;
60///
61/// let mut store = Store::new(&engine, ());
62/// let instance = Instance::new(&mut store, &module, &[])?;
63/// let f = instance.get_func(&mut store, "f").unwrap();
64///
65/// // We can cast a `(ref null nofunc)`-taking function into a typed function that
66/// // takes an `Option<NoFunc>` via the `Func::typed` method.
67/// let f = f.typed::<Option<NoFunc>, ()>(&store)?;
68///
69/// // We can call the typed function, passing the null `nofunc` reference.
70/// let result = f.call(&mut store, NoFunc::null());
71///
72/// // The function should not have trapped, because the reference we gave it was
73/// // null (as it had to be, since `NoFunc` is uninhabited).
74/// assert!(result.is_ok());
75/// # Ok(())
76/// # }
77/// ```
78#[derive(Copy, Clone, Debug, PartialEq, Eq)]
79pub struct NoFunc {
80 _inner: Uninhabited,
81}
82
83impl NoFunc {
84 /// Get the null `(ref null nofunc)` (aka `nullfuncref`) reference.
85 #[inline]
86 pub fn null() -> Option<NoFunc> {
87 None
88 }
89
90 /// Get the null `(ref null nofunc)` (aka `nullfuncref`) reference as a
91 /// [`Ref`].
92 #[inline]
93 pub fn null_ref() -> Ref {
94 Ref::Func(None)
95 }
96
97 /// Get the null `(ref null nofunc)` (aka `nullfuncref`) reference as a
98 /// [`Val`].
99 #[inline]
100 pub fn null_val() -> Val {
101 Val::FuncRef(None)
102 }
103}
104
105/// A WebAssembly function which can be called.
106///
107/// This type typically represents an exported function from a WebAssembly
108/// module instance. In this case a [`Func`] belongs to an [`Instance`] and is
109/// loaded from there. A [`Func`] may also represent a host function as well in
110/// some cases, too.
111///
112/// Functions can be called in a few different ways, either synchronous or async
113/// and either typed or untyped (more on this below). Note that host functions
114/// are normally inserted directly into a [`Linker`](crate::Linker) rather than
115/// using this directly, but both options are available.
116///
117/// # `Func` and `async`
118///
119/// Functions from the perspective of WebAssembly are always synchronous. You
120/// might have an `async` function in Rust, however, which you'd like to make
121/// available from WebAssembly. Wasmtime supports asynchronously calling
122/// WebAssembly through native stack switching. You can get some more
123/// information about [asynchronous configs](crate::Config::async_support), but
124/// from the perspective of `Func` it's important to know that whether or not
125/// your [`Store`](crate::Store) is asynchronous will dictate whether you call
126/// functions through [`Func::call`] or [`Func::call_async`] (or the typed
127/// wrappers such as [`TypedFunc::call`] vs [`TypedFunc::call_async`]).
128///
129/// # To `Func::call` or to `Func::typed().call()`
130///
131/// There's a 2x2 matrix of methods to call [`Func`]. Invocations can either be
132/// asynchronous or synchronous. They can also be statically typed or not.
133/// Whether or not an invocation is asynchronous is indicated via the method
134/// being `async` and [`call_async`](Func::call_async) being the entry point.
135/// Otherwise for statically typed or not your options are:
136///
137/// * Dynamically typed - if you don't statically know the signature of the
138/// function that you're calling you'll be using [`Func::call`] or
139/// [`Func::call_async`]. These functions take a variable-length slice of
140/// "boxed" arguments in their [`Val`] representation. Additionally the
141/// results are returned as an owned slice of [`Val`]. These methods are not
142/// optimized due to the dynamic type checks that must occur, in addition to
143/// some dynamic allocations for where to put all the arguments. While this
144/// allows you to call all possible wasm function signatures, if you're
145/// looking for a speedier alternative you can also use...
146///
147/// * Statically typed - if you statically know the type signature of the wasm
148/// function you're calling, then you'll want to use the [`Func::typed`]
149/// method to acquire an instance of [`TypedFunc`]. This structure is static proof
150/// that the underlying wasm function has the ascripted type, and type
151/// validation is only done once up-front. The [`TypedFunc::call`] and
152/// [`TypedFunc::call_async`] methods are much more efficient than [`Func::call`]
153/// and [`Func::call_async`] because the type signature is statically known.
154/// This eschews runtime checks as much as possible to get into wasm as fast
155/// as possible.
156///
157/// # Examples
158///
159/// One way to get a `Func` is from an [`Instance`] after you've instantiated
160/// it:
161///
162/// ```
163/// # use wasmtime::*;
164/// # fn main() -> anyhow::Result<()> {
165/// let engine = Engine::default();
166/// let module = Module::new(&engine, r#"(module (func (export "foo")))"#)?;
167/// let mut store = Store::new(&engine, ());
168/// let instance = Instance::new(&mut store, &module, &[])?;
169/// let foo = instance.get_func(&mut store, "foo").expect("export wasn't a function");
170///
171/// // Work with `foo` as a `Func` at this point, such as calling it
172/// // dynamically...
173/// match foo.call(&mut store, &[], &mut []) {
174/// Ok(()) => { /* ... */ }
175/// Err(trap) => {
176/// panic!("execution of `foo` resulted in a wasm trap: {}", trap);
177/// }
178/// }
179/// foo.call(&mut store, &[], &mut [])?;
180///
181/// // ... or we can make a static assertion about its signature and call it.
182/// // Our first call here can fail if the signatures don't match, and then the
183/// // second call can fail if the function traps (like the `match` above).
184/// let foo = foo.typed::<(), ()>(&store)?;
185/// foo.call(&mut store, ())?;
186/// # Ok(())
187/// # }
188/// ```
189///
190/// You can also use the [`wrap` function](Func::wrap) to create a
191/// `Func`
192///
193/// ```
194/// # use wasmtime::*;
195/// # fn main() -> anyhow::Result<()> {
196/// let mut store = Store::<()>::default();
197///
198/// // Create a custom `Func` which can execute arbitrary code inside of the
199/// // closure.
200/// let add = Func::wrap(&mut store, |a: i32, b: i32| -> i32 { a + b });
201///
202/// // Next we can hook that up to a wasm module which uses it.
203/// let module = Module::new(
204/// store.engine(),
205/// r#"
206/// (module
207/// (import "" "" (func $add (param i32 i32) (result i32)))
208/// (func (export "call_add_twice") (result i32)
209/// i32.const 1
210/// i32.const 2
211/// call $add
212/// i32.const 3
213/// i32.const 4
214/// call $add
215/// i32.add))
216/// "#,
217/// )?;
218/// let instance = Instance::new(&mut store, &module, &[add.into()])?;
219/// let call_add_twice = instance.get_typed_func::<(), i32>(&mut store, "call_add_twice")?;
220///
221/// assert_eq!(call_add_twice.call(&mut store, ())?, 10);
222/// # Ok(())
223/// # }
224/// ```
225///
226/// Or you could also create an entirely dynamic `Func`!
227///
228/// ```
229/// # use wasmtime::*;
230/// # fn main() -> anyhow::Result<()> {
231/// let mut store = Store::<()>::default();
232///
233/// // Here we need to define the type signature of our `Double` function and
234/// // then wrap it up in a `Func`
235/// let double_type = wasmtime::FuncType::new(
236/// store.engine(),
237/// [wasmtime::ValType::I32].iter().cloned(),
238/// [wasmtime::ValType::I32].iter().cloned(),
239/// );
240/// let double = Func::new(&mut store, double_type, |_, params, results| {
241/// let mut value = params[0].unwrap_i32();
242/// value *= 2;
243/// results[0] = value.into();
244/// Ok(())
245/// });
246///
247/// let module = Module::new(
248/// store.engine(),
249/// r#"
250/// (module
251/// (import "" "" (func $double (param i32) (result i32)))
252/// (func $start
253/// i32.const 1
254/// call $double
255/// drop)
256/// (start $start))
257/// "#,
258/// )?;
259/// let instance = Instance::new(&mut store, &module, &[double.into()])?;
260/// // .. work with `instance` if necessary
261/// # Ok(())
262/// # }
263/// ```
264#[derive(Copy, Clone, Debug)]
265#[repr(C)] // here for the C API
266pub struct Func {
267 /// The store that the below pointer belongs to.
268 ///
269 /// It's only safe to look at the contents of the pointer below when the
270 /// `StoreOpaque` matching this id is in-scope.
271 store: StoreId,
272
273 /// The raw `VMFuncRef`, whose lifetime is bound to the store this func
274 /// belongs to.
275 ///
276 /// Note that this field has an `unsafe_*` prefix to discourage use of it.
277 /// This is only safe to read/use if `self.store` is validated to belong to
278 /// an ambiently provided `StoreOpaque` or similar. Use the
279 /// `self.func_ref()` method instead of this field to perform this check.
280 unsafe_func_ref: SendSyncPtr<VMFuncRef>,
281}
282
283// Double-check that the C representation in `extern.h` matches our in-Rust
284// representation here in terms of size/alignment/etc.
285const _: () = {
286 #[repr(C)]
287 struct C(u64, *mut u8);
288 assert!(core::mem::size_of::<C>() == core::mem::size_of::<Func>());
289 assert!(core::mem::align_of::<C>() == core::mem::align_of::<Func>());
290 assert!(core::mem::offset_of!(Func, store) == 0);
291};
292
293macro_rules! for_each_function_signature {
294 ($mac:ident) => {
295 $mac!(0);
296 $mac!(1 A1);
297 $mac!(2 A1 A2);
298 $mac!(3 A1 A2 A3);
299 $mac!(4 A1 A2 A3 A4);
300 $mac!(5 A1 A2 A3 A4 A5);
301 $mac!(6 A1 A2 A3 A4 A5 A6);
302 $mac!(7 A1 A2 A3 A4 A5 A6 A7);
303 $mac!(8 A1 A2 A3 A4 A5 A6 A7 A8);
304 $mac!(9 A1 A2 A3 A4 A5 A6 A7 A8 A9);
305 $mac!(10 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10);
306 $mac!(11 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11);
307 $mac!(12 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12);
308 $mac!(13 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13);
309 $mac!(14 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14);
310 $mac!(15 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15);
311 $mac!(16 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 A16);
312 $mac!(17 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 A16 A17);
313 };
314}
315
316mod typed;
317use crate::runtime::vm::VMStackChain;
318pub use typed::*;
319
320impl Func {
321 /// Creates a new `Func` with the given arguments, typically to create a
322 /// host-defined function to pass as an import to a module.
323 ///
324 /// * `store` - the store in which to create this [`Func`], which will own
325 /// the return value.
326 ///
327 /// * `ty` - the signature of this function, used to indicate what the
328 /// inputs and outputs are.
329 ///
330 /// * `func` - the native code invoked whenever this `Func` will be called.
331 /// This closure is provided a [`Caller`] as its first argument to learn
332 /// information about the caller, and then it's passed a list of
333 /// parameters as a slice along with a mutable slice of where to write
334 /// results.
335 ///
336 /// Note that the implementation of `func` must adhere to the `ty` signature
337 /// given, error or traps may occur if it does not respect the `ty`
338 /// signature. For example if the function type declares that it returns one
339 /// i32 but the `func` closures does not write anything into the results
340 /// slice then a trap may be generated.
341 ///
342 /// Additionally note that this is quite a dynamic function since signatures
343 /// are not statically known. For a more performant and ergonomic `Func`
344 /// it's recommended to use [`Func::wrap`] if you can because with
345 /// statically known signatures Wasmtime can optimize the implementation
346 /// much more.
347 ///
348 /// For more information about `Send + Sync + 'static` requirements on the
349 /// `func`, see [`Func::wrap`](#why-send--sync--static).
350 ///
351 /// # Errors
352 ///
353 /// The host-provided function here returns a
354 /// [`Result<()>`](anyhow::Result). If the function returns `Ok(())` then
355 /// that indicates that the host function completed successfully and wrote
356 /// the result into the `&mut [Val]` argument.
357 ///
358 /// If the function returns `Err(e)`, however, then this is equivalent to
359 /// the host function triggering a trap for wasm. WebAssembly execution is
360 /// immediately halted and the original caller of [`Func::call`], for
361 /// example, will receive the error returned here (possibly with
362 /// [`WasmBacktrace`](crate::WasmBacktrace) context information attached).
363 ///
364 /// For more information about errors in Wasmtime see the [`Trap`]
365 /// documentation.
366 ///
367 /// [`Trap`]: crate::Trap
368 ///
369 /// # Panics
370 ///
371 /// Panics if the given function type is not associated with this store's
372 /// engine.
373 pub fn new<T: 'static>(
374 store: impl AsContextMut<Data = T>,
375 ty: FuncType,
376 func: impl Fn(Caller<'_, T>, &[Val], &mut [Val]) -> Result<()> + Send + Sync + 'static,
377 ) -> Self {
378 assert!(ty.comes_from_same_engine(store.as_context().engine()));
379 let ty_clone = ty.clone();
380 unsafe {
381 Func::new_unchecked(store, ty, move |caller, values| {
382 Func::invoke_host_func_for_wasm(caller, &ty_clone, values, &func)
383 })
384 }
385 }
386
387 /// Creates a new [`Func`] with the given arguments, although has fewer
388 /// runtime checks than [`Func::new`].
389 ///
390 /// This function takes a callback of a different signature than
391 /// [`Func::new`], instead receiving a raw pointer with a list of [`ValRaw`]
392 /// structures. These values have no type information associated with them
393 /// so it's up to the caller to provide a function that will correctly
394 /// interpret the list of values as those coming from the `ty` specified.
395 ///
396 /// If you're calling this from Rust it's recommended to either instead use
397 /// [`Func::new`] or [`Func::wrap`]. The [`Func::wrap`] API, in particular,
398 /// is both safer and faster than this API.
399 ///
400 /// # Errors
401 ///
402 /// See [`Func::new`] for the behavior of returning an error from the host
403 /// function provided here.
404 ///
405 /// # Unsafety
406 ///
407 /// This function is not safe because it's not known at compile time that
408 /// the `func` provided correctly interprets the argument types provided to
409 /// it, or that the results it produces will be of the correct type.
410 ///
411 /// # Panics
412 ///
413 /// Panics if the given function type is not associated with this store's
414 /// engine.
415 pub unsafe fn new_unchecked<T: 'static>(
416 mut store: impl AsContextMut<Data = T>,
417 ty: FuncType,
418 func: impl Fn(Caller<'_, T>, &mut [ValRaw]) -> Result<()> + Send + Sync + 'static,
419 ) -> Self {
420 assert!(ty.comes_from_same_engine(store.as_context().engine()));
421 let store = store.as_context_mut().0;
422 let host = HostFunc::new_unchecked(store.engine(), ty, func);
423 host.into_func(store)
424 }
425
426 /// Creates a new host-defined WebAssembly function which, when called,
427 /// will run the asynchronous computation defined by `func` to completion
428 /// and then return the result to WebAssembly.
429 ///
430 /// This function is the asynchronous analogue of [`Func::new`] and much of
431 /// that documentation applies to this as well. The key difference is that
432 /// `func` returns a future instead of simply a `Result`. Note that the
433 /// returned future can close over any of the arguments, but it cannot close
434 /// over the state of the closure itself. It's recommended to store any
435 /// necessary async state in the `T` of the [`Store<T>`](crate::Store) which
436 /// can be accessed through [`Caller::data`] or [`Caller::data_mut`].
437 ///
438 /// For more information on `Send + Sync + 'static`, see
439 /// [`Func::wrap`](#why-send--sync--static).
440 ///
441 /// # Panics
442 ///
443 /// This function will panic if `store` is not associated with an [async
444 /// config](crate::Config::async_support).
445 ///
446 /// Panics if the given function type is not associated with this store's
447 /// engine.
448 ///
449 /// # Errors
450 ///
451 /// See [`Func::new`] for the behavior of returning an error from the host
452 /// function provided here.
453 ///
454 /// # Examples
455 ///
456 /// ```
457 /// # use wasmtime::*;
458 /// # fn main() -> anyhow::Result<()> {
459 /// // Simulate some application-specific state as well as asynchronous
460 /// // functions to query that state.
461 /// struct MyDatabase {
462 /// // ...
463 /// }
464 ///
465 /// impl MyDatabase {
466 /// async fn get_row_count(&self) -> u32 {
467 /// // ...
468 /// # 100
469 /// }
470 /// }
471 ///
472 /// let my_database = MyDatabase {
473 /// // ...
474 /// };
475 ///
476 /// // Using `new_async` we can hook up into calling our async
477 /// // `get_row_count` function.
478 /// let engine = Engine::new(Config::new().async_support(true))?;
479 /// let mut store = Store::new(&engine, MyDatabase {
480 /// // ...
481 /// });
482 /// let get_row_count_type = wasmtime::FuncType::new(
483 /// &engine,
484 /// None,
485 /// Some(wasmtime::ValType::I32),
486 /// );
487 /// let get = Func::new_async(&mut store, get_row_count_type, |caller, _params, results| {
488 /// Box::new(async move {
489 /// let count = caller.data().get_row_count().await;
490 /// results[0] = Val::I32(count as i32);
491 /// Ok(())
492 /// })
493 /// });
494 /// // ...
495 /// # Ok(())
496 /// # }
497 /// ```
498 #[cfg(all(feature = "async", feature = "cranelift"))]
499 pub fn new_async<T, F>(store: impl AsContextMut<Data = T>, ty: FuncType, func: F) -> Func
500 where
501 F: for<'a> Fn(
502 Caller<'a, T>,
503 &'a [Val],
504 &'a mut [Val],
505 ) -> Box<dyn Future<Output = Result<()>> + Send + 'a>
506 + Send
507 + Sync
508 + 'static,
509 T: 'static,
510 {
511 assert!(
512 store.as_context().async_support(),
513 "cannot use `new_async` without enabling async support in the config"
514 );
515 assert!(ty.comes_from_same_engine(store.as_context().engine()));
516 Func::new(store, ty, move |mut caller, params, results| {
517 let async_cx = caller
518 .store
519 .as_context_mut()
520 .0
521 .async_cx()
522 .expect("Attempt to spawn new action on dying fiber");
523 let future = func(caller, params, results);
524 match unsafe { async_cx.block_on(Pin::from(future)) } {
525 Ok(Ok(())) => Ok(()),
526 Ok(Err(trap)) | Err(trap) => Err(trap),
527 }
528 })
529 }
530
531 pub(crate) unsafe fn from_vm_func_ref(
532 store: &StoreOpaque,
533 func_ref: NonNull<VMFuncRef>,
534 ) -> Func {
535 debug_assert!(func_ref.as_ref().type_index != VMSharedTypeIndex::default());
536 Func {
537 store: store.id(),
538 unsafe_func_ref: func_ref.into(),
539 }
540 }
541
542 /// Creates a new `Func` from the given Rust closure.
543 ///
544 /// This function will create a new `Func` which, when called, will
545 /// execute the given Rust closure. Unlike [`Func::new`] the target
546 /// function being called is known statically so the type signature can
547 /// be inferred. Rust types will map to WebAssembly types as follows:
548 ///
549 /// | Rust Argument Type | WebAssembly Type |
550 /// |-----------------------------------|-------------------------------------------|
551 /// | `i32` | `i32` |
552 /// | `u32` | `i32` |
553 /// | `i64` | `i64` |
554 /// | `u64` | `i64` |
555 /// | `f32` | `f32` |
556 /// | `f64` | `f64` |
557 /// | `V128` on x86-64 and aarch64 only | `v128` |
558 /// | `Option<Func>` | `funcref` aka `(ref null func)` |
559 /// | `Func` | `(ref func)` |
560 /// | `Option<Nofunc>` | `nullfuncref` aka `(ref null nofunc)` |
561 /// | `NoFunc` | `(ref nofunc)` |
562 /// | `Option<Rooted<ExternRef>>` | `externref` aka `(ref null extern)` |
563 /// | `Rooted<ExternRef>` | `(ref extern)` |
564 /// | `Option<NoExtern>` | `nullexternref` aka `(ref null noextern)` |
565 /// | `NoExtern` | `(ref noextern)` |
566 /// | `Option<Rooted<AnyRef>>` | `anyref` aka `(ref null any)` |
567 /// | `Rooted<AnyRef>` | `(ref any)` |
568 /// | `Option<Rooted<EqRef>>` | `eqref` aka `(ref null eq)` |
569 /// | `Rooted<EqRef>` | `(ref eq)` |
570 /// | `Option<I31>` | `i31ref` aka `(ref null i31)` |
571 /// | `I31` | `(ref i31)` |
572 /// | `Option<Rooted<StructRef>>` | `(ref null struct)` |
573 /// | `Rooted<StructRef>` | `(ref struct)` |
574 /// | `Option<Rooted<ArrayRef>>` | `(ref null array)` |
575 /// | `Rooted<ArrayRef>` | `(ref array)` |
576 /// | `Option<NoneRef>` | `nullref` aka `(ref null none)` |
577 /// | `NoneRef` | `(ref none)` |
578 ///
579 /// Note that anywhere a `Rooted<T>` appears, a `ManuallyRooted<T>` may also
580 /// be used.
581 ///
582 /// Any of the Rust types can be returned from the closure as well, in
583 /// addition to some extra types
584 ///
585 /// | Rust Return Type | WebAssembly Return Type | Meaning |
586 /// |-------------------|-------------------------|-----------------------|
587 /// | `()` | nothing | no return value |
588 /// | `T` | `T` | a single return value |
589 /// | `(T1, T2, ...)` | `T1 T2 ...` | multiple returns |
590 ///
591 /// Note that all return types can also be wrapped in `Result<_>` to
592 /// indicate that the host function can generate a trap as well as possibly
593 /// returning a value.
594 ///
595 /// Finally you can also optionally take [`Caller`] as the first argument of
596 /// your closure. If inserted then you're able to inspect the caller's
597 /// state, for example the [`Memory`](crate::Memory) it has exported so you
598 /// can read what pointers point to.
599 ///
600 /// Note that when using this API, the intention is to create as thin of a
601 /// layer as possible for when WebAssembly calls the function provided. With
602 /// sufficient inlining and optimization the WebAssembly will call straight
603 /// into `func` provided, with no extra fluff entailed.
604 ///
605 /// # Why `Send + Sync + 'static`?
606 ///
607 /// All host functions defined in a [`Store`](crate::Store) (including
608 /// those from [`Func::new`] and other constructors) require that the
609 /// `func` provided is `Send + Sync + 'static`. Additionally host functions
610 /// always are `Fn` as opposed to `FnMut` or `FnOnce`. This can at-a-glance
611 /// feel restrictive since the closure cannot close over as many types as
612 /// before. The reason for this, though, is to ensure that
613 /// [`Store<T>`](crate::Store) can implement both the `Send` and `Sync`
614 /// traits.
615 ///
616 /// Fear not, however, because this isn't as restrictive as it seems! Host
617 /// functions are provided a [`Caller<'_, T>`](crate::Caller) argument which
618 /// allows access to the host-defined data within the
619 /// [`Store`](crate::Store). The `T` type is not required to be any of
620 /// `Send`, `Sync`, or `'static`! This means that you can store whatever
621 /// you'd like in `T` and have it accessible by all host functions.
622 /// Additionally mutable access to `T` is allowed through
623 /// [`Caller::data_mut`].
624 ///
625 /// Most host-defined [`Func`] values provide closures that end up not
626 /// actually closing over any values. These zero-sized types will use the
627 /// context from [`Caller`] for host-defined information.
628 ///
629 /// # Errors
630 ///
631 /// The closure provided here to `wrap` can optionally return a
632 /// [`Result<T>`](anyhow::Result). Returning `Ok(t)` represents the host
633 /// function successfully completing with the `t` result. Returning
634 /// `Err(e)`, however, is equivalent to raising a custom wasm trap.
635 /// Execution of WebAssembly does not resume and the stack is unwound to the
636 /// original caller of the function where the error is returned.
637 ///
638 /// For more information about errors in Wasmtime see the [`Trap`]
639 /// documentation.
640 ///
641 /// [`Trap`]: crate::Trap
642 ///
643 /// # Examples
644 ///
645 /// First up we can see how simple wasm imports can be implemented, such
646 /// as a function that adds its two arguments and returns the result.
647 ///
648 /// ```
649 /// # use wasmtime::*;
650 /// # fn main() -> anyhow::Result<()> {
651 /// # let mut store = Store::<()>::default();
652 /// let add = Func::wrap(&mut store, |a: i32, b: i32| a + b);
653 /// let module = Module::new(
654 /// store.engine(),
655 /// r#"
656 /// (module
657 /// (import "" "" (func $add (param i32 i32) (result i32)))
658 /// (func (export "foo") (param i32 i32) (result i32)
659 /// local.get 0
660 /// local.get 1
661 /// call $add))
662 /// "#,
663 /// )?;
664 /// let instance = Instance::new(&mut store, &module, &[add.into()])?;
665 /// let foo = instance.get_typed_func::<(i32, i32), i32>(&mut store, "foo")?;
666 /// assert_eq!(foo.call(&mut store, (1, 2))?, 3);
667 /// # Ok(())
668 /// # }
669 /// ```
670 ///
671 /// We can also do the same thing, but generate a trap if the addition
672 /// overflows:
673 ///
674 /// ```
675 /// # use wasmtime::*;
676 /// # fn main() -> anyhow::Result<()> {
677 /// # let mut store = Store::<()>::default();
678 /// let add = Func::wrap(&mut store, |a: i32, b: i32| {
679 /// match a.checked_add(b) {
680 /// Some(i) => Ok(i),
681 /// None => anyhow::bail!("overflow"),
682 /// }
683 /// });
684 /// let module = Module::new(
685 /// store.engine(),
686 /// r#"
687 /// (module
688 /// (import "" "" (func $add (param i32 i32) (result i32)))
689 /// (func (export "foo") (param i32 i32) (result i32)
690 /// local.get 0
691 /// local.get 1
692 /// call $add))
693 /// "#,
694 /// )?;
695 /// let instance = Instance::new(&mut store, &module, &[add.into()])?;
696 /// let foo = instance.get_typed_func::<(i32, i32), i32>(&mut store, "foo")?;
697 /// assert_eq!(foo.call(&mut store, (1, 2))?, 3);
698 /// assert!(foo.call(&mut store, (i32::max_value(), 1)).is_err());
699 /// # Ok(())
700 /// # }
701 /// ```
702 ///
703 /// And don't forget all the wasm types are supported!
704 ///
705 /// ```
706 /// # use wasmtime::*;
707 /// # fn main() -> anyhow::Result<()> {
708 /// # let mut store = Store::<()>::default();
709 /// let debug = Func::wrap(&mut store, |a: i32, b: u32, c: f32, d: i64, e: u64, f: f64| {
710 ///
711 /// println!("a={}", a);
712 /// println!("b={}", b);
713 /// println!("c={}", c);
714 /// println!("d={}", d);
715 /// println!("e={}", e);
716 /// println!("f={}", f);
717 /// });
718 /// let module = Module::new(
719 /// store.engine(),
720 /// r#"
721 /// (module
722 /// (import "" "" (func $debug (param i32 i32 f32 i64 i64 f64)))
723 /// (func (export "foo")
724 /// i32.const -1
725 /// i32.const 1
726 /// f32.const 2
727 /// i64.const -3
728 /// i64.const 3
729 /// f64.const 4
730 /// call $debug))
731 /// "#,
732 /// )?;
733 /// let instance = Instance::new(&mut store, &module, &[debug.into()])?;
734 /// let foo = instance.get_typed_func::<(), ()>(&mut store, "foo")?;
735 /// foo.call(&mut store, ())?;
736 /// # Ok(())
737 /// # }
738 /// ```
739 ///
740 /// Finally if you want to get really fancy you can also implement
741 /// imports that read/write wasm module's memory
742 ///
743 /// ```
744 /// use std::str;
745 ///
746 /// # use wasmtime::*;
747 /// # fn main() -> anyhow::Result<()> {
748 /// # let mut store = Store::default();
749 /// let log_str = Func::wrap(&mut store, |mut caller: Caller<'_, ()>, ptr: i32, len: i32| {
750 /// let mem = match caller.get_export("memory") {
751 /// Some(Extern::Memory(mem)) => mem,
752 /// _ => anyhow::bail!("failed to find host memory"),
753 /// };
754 /// let data = mem.data(&caller)
755 /// .get(ptr as u32 as usize..)
756 /// .and_then(|arr| arr.get(..len as u32 as usize));
757 /// let string = match data {
758 /// Some(data) => match str::from_utf8(data) {
759 /// Ok(s) => s,
760 /// Err(_) => anyhow::bail!("invalid utf-8"),
761 /// },
762 /// None => anyhow::bail!("pointer/length out of bounds"),
763 /// };
764 /// assert_eq!(string, "Hello, world!");
765 /// println!("{}", string);
766 /// Ok(())
767 /// });
768 /// let module = Module::new(
769 /// store.engine(),
770 /// r#"
771 /// (module
772 /// (import "" "" (func $log_str (param i32 i32)))
773 /// (func (export "foo")
774 /// i32.const 4 ;; ptr
775 /// i32.const 13 ;; len
776 /// call $log_str)
777 /// (memory (export "memory") 1)
778 /// (data (i32.const 4) "Hello, world!"))
779 /// "#,
780 /// )?;
781 /// let instance = Instance::new(&mut store, &module, &[log_str.into()])?;
782 /// let foo = instance.get_typed_func::<(), ()>(&mut store, "foo")?;
783 /// foo.call(&mut store, ())?;
784 /// # Ok(())
785 /// # }
786 /// ```
787 pub fn wrap<T, Params, Results>(
788 mut store: impl AsContextMut<Data = T>,
789 func: impl IntoFunc<T, Params, Results>,
790 ) -> Func
791 where
792 T: 'static,
793 {
794 let store = store.as_context_mut().0;
795 // part of this unsafety is about matching the `T` to a `Store<T>`,
796 // which is done through the `AsContextMut` bound above.
797 unsafe {
798 let host = HostFunc::wrap(store.engine(), func);
799 host.into_func(store)
800 }
801 }
802
803 #[cfg(feature = "async")]
804 fn wrap_inner<F, T, Params, Results>(mut store: impl AsContextMut<Data = T>, func: F) -> Func
805 where
806 F: Fn(Caller<'_, T>, Params) -> Results + Send + Sync + 'static,
807 Params: WasmTyList,
808 Results: WasmRet,
809 T: 'static,
810 {
811 let store = store.as_context_mut().0;
812 // part of this unsafety is about matching the `T` to a `Store<T>`,
813 // which is done through the `AsContextMut` bound above.
814 unsafe {
815 let host = HostFunc::wrap_inner(store.engine(), func);
816 host.into_func(store)
817 }
818 }
819
820 /// Same as [`Func::wrap`], except the closure asynchronously produces the
821 /// result and the arguments are passed within a tuple. For more information
822 /// see the [`Func`] documentation.
823 ///
824 /// # Panics
825 ///
826 /// This function will panic if called with a non-asynchronous store.
827 #[cfg(feature = "async")]
828 pub fn wrap_async<T, F, P, R>(store: impl AsContextMut<Data = T>, func: F) -> Func
829 where
830 F: for<'a> Fn(Caller<'a, T>, P) -> Box<dyn Future<Output = R> + Send + 'a>
831 + Send
832 + Sync
833 + 'static,
834 P: WasmTyList,
835 R: WasmRet,
836 T: 'static,
837 {
838 assert!(
839 store.as_context().async_support(),
840 concat!("cannot use `wrap_async` without enabling async support on the config")
841 );
842 Func::wrap_inner(store, move |mut caller: Caller<'_, T>, args| {
843 let async_cx = caller
844 .store
845 .as_context_mut()
846 .0
847 .async_cx()
848 .expect("Attempt to start async function on dying fiber");
849 let future = func(caller, args);
850
851 match unsafe { async_cx.block_on(Pin::from(future)) } {
852 Ok(ret) => ret.into_fallible(),
853 Err(e) => R::fallible_from_error(e),
854 }
855 })
856 }
857
858 /// Returns the underlying wasm type that this `Func` has.
859 ///
860 /// # Panics
861 ///
862 /// Panics if `store` does not own this function.
863 pub fn ty(&self, store: impl AsContext) -> FuncType {
864 self.load_ty(&store.as_context().0)
865 }
866
867 /// Forcibly loads the type of this function from the `Engine`.
868 ///
869 /// Note that this is a somewhat expensive method since it requires taking a
870 /// lock as well as cloning a type.
871 pub(crate) fn load_ty(&self, store: &StoreOpaque) -> FuncType {
872 FuncType::from_shared_type_index(store.engine(), self.type_index(store))
873 }
874
875 /// Does this function match the given type?
876 ///
877 /// That is, is this function's type a subtype of the given type?
878 ///
879 /// # Panics
880 ///
881 /// Panics if this function is not associated with the given store or if the
882 /// function type is not associated with the store's engine.
883 pub fn matches_ty(&self, store: impl AsContext, func_ty: &FuncType) -> bool {
884 self._matches_ty(store.as_context().0, func_ty)
885 }
886
887 pub(crate) fn _matches_ty(&self, store: &StoreOpaque, func_ty: &FuncType) -> bool {
888 let actual_ty = self.load_ty(store);
889 actual_ty.matches(func_ty)
890 }
891
892 pub(crate) fn ensure_matches_ty(&self, store: &StoreOpaque, func_ty: &FuncType) -> Result<()> {
893 if !self.comes_from_same_store(store) {
894 bail!("function used with wrong store");
895 }
896 if self._matches_ty(store, func_ty) {
897 Ok(())
898 } else {
899 let actual_ty = self.load_ty(store);
900 bail!("type mismatch: expected {func_ty}, found {actual_ty}")
901 }
902 }
903
904 pub(crate) fn type_index(&self, data: &StoreOpaque) -> VMSharedTypeIndex {
905 unsafe { self.vm_func_ref(data).as_ref().type_index }
906 }
907
908 /// Invokes this function with the `params` given and writes returned values
909 /// to `results`.
910 ///
911 /// The `params` here must match the type signature of this `Func`, or an
912 /// error will occur. Additionally `results` must have the same
913 /// length as the number of results for this function. Calling this function
914 /// will synchronously execute the WebAssembly function referenced to get
915 /// the results.
916 ///
917 /// This function will return `Ok(())` if execution completed without a trap
918 /// or error of any kind. In this situation the results will be written to
919 /// the provided `results` array.
920 ///
921 /// # Errors
922 ///
923 /// Any error which occurs throughout the execution of the function will be
924 /// returned as `Err(e)`. The [`Error`](anyhow::Error) type can be inspected
925 /// for the precise error cause such as:
926 ///
927 /// * [`Trap`] - indicates that a wasm trap happened and execution was
928 /// halted.
929 /// * [`WasmBacktrace`] - optionally included on errors for backtrace
930 /// information of the trap/error.
931 /// * Other string-based errors to indicate issues such as type errors with
932 /// `params`.
933 /// * Any host-originating error originally returned from a function defined
934 /// via [`Func::new`], for example.
935 ///
936 /// Errors typically indicate that execution of WebAssembly was halted
937 /// mid-way and did not complete after the error condition happened.
938 ///
939 /// [`Trap`]: crate::Trap
940 ///
941 /// # Panics
942 ///
943 /// This function will panic if called on a function belonging to an async
944 /// store. Asynchronous stores must always use `call_async`. Also panics if
945 /// `store` does not own this function.
946 ///
947 /// [`WasmBacktrace`]: crate::WasmBacktrace
948 pub fn call(
949 &self,
950 mut store: impl AsContextMut,
951 params: &[Val],
952 results: &mut [Val],
953 ) -> Result<()> {
954 assert!(
955 !store.as_context().async_support(),
956 "must use `call_async` when async support is enabled on the config",
957 );
958 let mut store = store.as_context_mut();
959
960 let _need_gc = self.call_impl_check_args(&mut store, params, results)?;
961
962 #[cfg(feature = "gc")]
963 if _need_gc {
964 store.gc(None);
965 }
966
967 unsafe { self.call_impl_do_call(&mut store, params, results) }
968 }
969
970 /// Invokes this function in an "unchecked" fashion, reading parameters and
971 /// writing results to `params_and_returns`.
972 ///
973 /// This function is the same as [`Func::call`] except that the arguments
974 /// and results both use a different representation. If possible it's
975 /// recommended to use [`Func::call`] if safety isn't necessary or to use
976 /// [`Func::typed`] in conjunction with [`TypedFunc::call`] since that's
977 /// both safer and faster than this method of invoking a function.
978 ///
979 /// Note that if this function takes `externref` arguments then it will
980 /// **not** automatically GC unlike the [`Func::call`] and
981 /// [`TypedFunc::call`] functions. This means that if this function is
982 /// invoked many times with new `ExternRef` values and no other GC happens
983 /// via any other means then no values will get collected.
984 ///
985 /// # Errors
986 ///
987 /// For more information about errors see the [`Func::call`] documentation.
988 ///
989 /// # Unsafety
990 ///
991 /// This function is unsafe because the `params_and_returns` argument is not
992 /// validated at all. It must uphold invariants such as:
993 ///
994 /// * It's a valid pointer to an array
995 /// * It has enough space to store all parameters
996 /// * It has enough space to store all results (not at the same time as
997 /// parameters)
998 /// * Parameters are initially written to the array and have the correct
999 /// types and such.
1000 /// * Reference types like `externref` and `funcref` are valid at the
1001 /// time of this call and for the `store` specified.
1002 ///
1003 /// These invariants are all upheld for you with [`Func::call`] and
1004 /// [`TypedFunc::call`].
1005 pub unsafe fn call_unchecked(
1006 &self,
1007 mut store: impl AsContextMut,
1008 params_and_returns: *mut [ValRaw],
1009 ) -> Result<()> {
1010 let mut store = store.as_context_mut();
1011 let func_ref = self.vm_func_ref(store.0);
1012 let params_and_returns = NonNull::new(params_and_returns).unwrap_or(NonNull::from(&mut []));
1013 Self::call_unchecked_raw(&mut store, func_ref, params_and_returns)
1014 }
1015
1016 pub(crate) unsafe fn call_unchecked_raw<T>(
1017 store: &mut StoreContextMut<'_, T>,
1018 func_ref: NonNull<VMFuncRef>,
1019 params_and_returns: NonNull<[ValRaw]>,
1020 ) -> Result<()> {
1021 invoke_wasm_and_catch_traps(store, |caller, vm| {
1022 func_ref.as_ref().array_call(
1023 vm,
1024 VMOpaqueContext::from_vmcontext(caller),
1025 params_and_returns,
1026 )
1027 })
1028 }
1029
1030 /// Converts the raw representation of a `funcref` into an `Option<Func>`
1031 ///
1032 /// This is intended to be used in conjunction with [`Func::new_unchecked`],
1033 /// [`Func::call_unchecked`], and [`ValRaw`] with its `funcref` field.
1034 ///
1035 /// # Unsafety
1036 ///
1037 /// This function is not safe because `raw` is not validated at all. The
1038 /// caller must guarantee that `raw` is owned by the `store` provided and is
1039 /// valid within the `store`.
1040 pub unsafe fn from_raw(mut store: impl AsContextMut, raw: *mut c_void) -> Option<Func> {
1041 Self::_from_raw(store.as_context_mut().0, raw)
1042 }
1043
1044 pub(crate) unsafe fn _from_raw(store: &mut StoreOpaque, raw: *mut c_void) -> Option<Func> {
1045 Some(Func::from_vm_func_ref(store, NonNull::new(raw.cast())?))
1046 }
1047
1048 /// Extracts the raw value of this `Func`, which is owned by `store`.
1049 ///
1050 /// This function returns a value that's suitable for writing into the
1051 /// `funcref` field of the [`ValRaw`] structure.
1052 ///
1053 /// # Unsafety
1054 ///
1055 /// The returned value is only valid for as long as the store is alive and
1056 /// this function is properly rooted within it. Additionally this function
1057 /// should not be liberally used since it's a very low-level knob.
1058 pub unsafe fn to_raw(&self, mut store: impl AsContextMut) -> *mut c_void {
1059 self.vm_func_ref(store.as_context_mut().0).as_ptr().cast()
1060 }
1061
1062 /// Invokes this function with the `params` given, returning the results
1063 /// asynchronously.
1064 ///
1065 /// This function is the same as [`Func::call`] except that it is
1066 /// asynchronous. This is only compatible with stores associated with an
1067 /// [asynchronous config](crate::Config::async_support).
1068 ///
1069 /// It's important to note that the execution of WebAssembly will happen
1070 /// synchronously in the `poll` method of the future returned from this
1071 /// function. Wasmtime does not manage its own thread pool or similar to
1072 /// execute WebAssembly in. Future `poll` methods are generally expected to
1073 /// resolve quickly, so it's recommended that you run or poll this future
1074 /// in a "blocking context".
1075 ///
1076 /// For more information see the documentation on [asynchronous
1077 /// configs](crate::Config::async_support).
1078 ///
1079 /// # Errors
1080 ///
1081 /// For more information on errors see the [`Func::call`] documentation.
1082 ///
1083 /// # Panics
1084 ///
1085 /// Panics if this is called on a function in a synchronous store. This
1086 /// only works with functions defined within an asynchronous store. Also
1087 /// panics if `store` does not own this function.
1088 #[cfg(feature = "async")]
1089 pub async fn call_async(
1090 &self,
1091 mut store: impl AsContextMut<Data: Send>,
1092 params: &[Val],
1093 results: &mut [Val],
1094 ) -> Result<()> {
1095 let mut store = store.as_context_mut();
1096 assert!(
1097 store.0.async_support(),
1098 "cannot use `call_async` without enabling async support in the config",
1099 );
1100
1101 let _need_gc = self.call_impl_check_args(&mut store, params, results)?;
1102
1103 #[cfg(feature = "gc")]
1104 if _need_gc {
1105 store.gc_async(None).await?;
1106 }
1107
1108 let result = store
1109 .on_fiber(|store| unsafe { self.call_impl_do_call(store, params, results) })
1110 .await??;
1111 Ok(result)
1112 }
1113
1114 /// Perform dynamic checks that the arguments given to us match
1115 /// the signature of this function and are appropriate to pass to this
1116 /// function.
1117 ///
1118 /// This involves checking to make sure we have the right number and types
1119 /// of arguments as well as making sure everything is from the same `Store`.
1120 ///
1121 /// This must be called just before `call_impl_do_call`.
1122 ///
1123 /// Returns whether we need to GC before calling `call_impl_do_call`.
1124 fn call_impl_check_args<T>(
1125 &self,
1126 store: &mut StoreContextMut<'_, T>,
1127 params: &[Val],
1128 results: &mut [Val],
1129 ) -> Result<bool> {
1130 let ty = self.load_ty(store.0);
1131 if ty.params().len() != params.len() {
1132 bail!(
1133 "expected {} arguments, got {}",
1134 ty.params().len(),
1135 params.len()
1136 );
1137 }
1138 if ty.results().len() != results.len() {
1139 bail!(
1140 "expected {} results, got {}",
1141 ty.results().len(),
1142 results.len()
1143 );
1144 }
1145
1146 for (ty, arg) in ty.params().zip(params) {
1147 arg.ensure_matches_ty(store.0, &ty)
1148 .context("argument type mismatch")?;
1149 if !arg.comes_from_same_store(store.0) {
1150 bail!("cross-`Store` values are not currently supported");
1151 }
1152 }
1153
1154 #[cfg(feature = "gc")]
1155 {
1156 // Check whether we need to GC before calling into Wasm.
1157 //
1158 // For example, with the DRC collector, whenever we pass GC refs
1159 // from host code to Wasm code, they go into the
1160 // `VMGcRefActivationsTable`. But the table might be at capacity
1161 // already. If it is at capacity (unlikely) then we need to do a GC
1162 // to free up space.
1163 let num_gc_refs = ty.as_wasm_func_type().non_i31_gc_ref_params_count();
1164 if let Some(num_gc_refs) = core::num::NonZeroUsize::new(num_gc_refs) {
1165 return Ok(store
1166 .0
1167 .optional_gc_store()
1168 .is_some_and(|s| s.gc_heap.need_gc_before_entering_wasm(num_gc_refs)));
1169 }
1170 }
1171
1172 Ok(false)
1173 }
1174
1175 /// Do the actual call into Wasm.
1176 ///
1177 /// # Safety
1178 ///
1179 /// You must have type checked the arguments by calling
1180 /// `call_impl_check_args` immediately before calling this function. It is
1181 /// only safe to call this function if that one did not return an error.
1182 unsafe fn call_impl_do_call<T>(
1183 &self,
1184 store: &mut StoreContextMut<'_, T>,
1185 params: &[Val],
1186 results: &mut [Val],
1187 ) -> Result<()> {
1188 // Store the argument values into `values_vec`.
1189 let ty = self.load_ty(store.0);
1190 let values_vec_size = params.len().max(ty.results().len());
1191 let mut values_vec = store.0.take_wasm_val_raw_storage();
1192 debug_assert!(values_vec.is_empty());
1193 values_vec.resize_with(values_vec_size, || ValRaw::v128(0));
1194 for (arg, slot) in params.iter().cloned().zip(&mut values_vec) {
1195 unsafe {
1196 *slot = arg.to_raw(&mut *store)?;
1197 }
1198 }
1199
1200 unsafe {
1201 self.call_unchecked(
1202 &mut *store,
1203 core::ptr::slice_from_raw_parts_mut(values_vec.as_mut_ptr(), values_vec_size),
1204 )?;
1205 }
1206
1207 for ((i, slot), val) in results.iter_mut().enumerate().zip(&values_vec) {
1208 let ty = ty.results().nth(i).unwrap();
1209 *slot = unsafe { Val::from_raw(&mut *store, *val, ty) };
1210 }
1211 values_vec.truncate(0);
1212 store.0.save_wasm_val_raw_storage(values_vec);
1213 Ok(())
1214 }
1215
1216 #[inline]
1217 pub(crate) fn vm_func_ref(&self, store: &StoreOpaque) -> NonNull<VMFuncRef> {
1218 self.store.assert_belongs_to(store.id());
1219 self.unsafe_func_ref.as_non_null()
1220 }
1221
1222 pub(crate) unsafe fn from_wasmtime_function(
1223 export: ExportFunction,
1224 store: &StoreOpaque,
1225 ) -> Self {
1226 Self::from_vm_func_ref(store, export.func_ref)
1227 }
1228
1229 pub(crate) fn vmimport(&self, store: &StoreOpaque) -> VMFunctionImport {
1230 unsafe {
1231 let f = self.vm_func_ref(store);
1232 VMFunctionImport {
1233 // Note that this is a load-bearing `unwrap` here, but is
1234 // never expected to trip at runtime. The general problem is
1235 // that host functions do not have a `wasm_call` function so
1236 // the `VMFuncRef` type has an optional pointer there. This is
1237 // only able to be filled out when a function is "paired" with
1238 // a module where trampolines are present to fill out
1239 // `wasm_call` pointers.
1240 //
1241 // This pairing of modules doesn't happen explicitly but is
1242 // instead managed lazily throughout Wasmtime. Specifically the
1243 // way this works is one of:
1244 //
1245 // * When a host function is created the store's list of
1246 // modules are searched for a wasm trampoline. If not found
1247 // the `wasm_call` field is left blank.
1248 //
1249 // * When a module instantiation happens, which uses this
1250 // function, the module will be used to fill any outstanding
1251 // holes that it has trampolines for.
1252 //
1253 // This means that by the time we get to this point any
1254 // relevant holes should be filled out. Thus if this panic
1255 // actually triggers then it's indicative of a missing `fill`
1256 // call somewhere else.
1257 wasm_call: f.as_ref().wasm_call.unwrap(),
1258 array_call: f.as_ref().array_call,
1259 vmctx: f.as_ref().vmctx,
1260 }
1261 }
1262 }
1263
1264 pub(crate) fn comes_from_same_store(&self, store: &StoreOpaque) -> bool {
1265 self.store == store.id()
1266 }
1267
1268 fn invoke_host_func_for_wasm<T>(
1269 mut caller: Caller<'_, T>,
1270 ty: &FuncType,
1271 values_vec: &mut [ValRaw],
1272 func: &dyn Fn(Caller<'_, T>, &[Val], &mut [Val]) -> Result<()>,
1273 ) -> Result<()> {
1274 // Translate the raw JIT arguments in `values_vec` into a `Val` which
1275 // we'll be passing as a slice. The storage for our slice-of-`Val` we'll
1276 // be taking from the `Store`. We preserve our slice back into the
1277 // `Store` after the hostcall, ideally amortizing the cost of allocating
1278 // the storage across wasm->host calls.
1279 //
1280 // Note that we have a dynamic guarantee that `values_vec` is the
1281 // appropriate length to both read all arguments from as well as store
1282 // all results into.
1283 let mut val_vec = caller.store.0.take_hostcall_val_storage();
1284 debug_assert!(val_vec.is_empty());
1285 let nparams = ty.params().len();
1286 val_vec.reserve(nparams + ty.results().len());
1287 for (i, ty) in ty.params().enumerate() {
1288 val_vec.push(unsafe { Val::from_raw(&mut caller.store, values_vec[i], ty) })
1289 }
1290
1291 val_vec.extend((0..ty.results().len()).map(|_| Val::null_func_ref()));
1292 let (params, results) = val_vec.split_at_mut(nparams);
1293 func(caller.sub_caller(), params, results)?;
1294
1295 // Unlike our arguments we need to dynamically check that the return
1296 // values produced are correct. There could be a bug in `func` that
1297 // produces the wrong number, wrong types, or wrong stores of
1298 // values, and we need to catch that here.
1299 for (i, (ret, ty)) in results.iter().zip(ty.results()).enumerate() {
1300 ret.ensure_matches_ty(caller.store.0, &ty)
1301 .context("function attempted to return an incompatible value")?;
1302 unsafe {
1303 values_vec[i] = ret.to_raw(&mut caller.store)?;
1304 }
1305 }
1306
1307 // Restore our `val_vec` back into the store so it's usable for the next
1308 // hostcall to reuse our own storage.
1309 val_vec.truncate(0);
1310 caller.store.0.save_hostcall_val_storage(val_vec);
1311 Ok(())
1312 }
1313
1314 /// Attempts to extract a typed object from this `Func` through which the
1315 /// function can be called.
1316 ///
1317 /// This function serves as an alternative to [`Func::call`] and
1318 /// [`Func::call_async`]. This method performs a static type check (using
1319 /// the `Params` and `Results` type parameters on the underlying wasm
1320 /// function. If the type check passes then a `TypedFunc` object is returned,
1321 /// otherwise an error is returned describing the typecheck failure.
1322 ///
1323 /// The purpose of this relative to [`Func::call`] is that it's much more
1324 /// efficient when used to invoke WebAssembly functions. With the types
1325 /// statically known far less setup/teardown is required when invoking
1326 /// WebAssembly. If speed is desired then this function is recommended to be
1327 /// used instead of [`Func::call`] (which is more general, hence its
1328 /// slowdown).
1329 ///
1330 /// The `Params` type parameter is used to describe the parameters of the
1331 /// WebAssembly function. This can either be a single type (like `i32`), or
1332 /// a tuple of types representing the list of parameters (like `(i32, f32,
1333 /// f64)`). Additionally you can use `()` to represent that the function has
1334 /// no parameters.
1335 ///
1336 /// The `Results` type parameter is used to describe the results of the
1337 /// function. This behaves the same way as `Params`, but just for the
1338 /// results of the function.
1339 ///
1340 /// # Translating Between WebAssembly and Rust Types
1341 ///
1342 /// Translation between Rust types and WebAssembly types looks like:
1343 ///
1344 /// | WebAssembly | Rust |
1345 /// |-------------------------------------------|---------------------------------------|
1346 /// | `i32` | `i32` or `u32` |
1347 /// | `i64` | `i64` or `u64` |
1348 /// | `f32` | `f32` |
1349 /// | `f64` | `f64` |
1350 /// | `externref` aka `(ref null extern)` | `Option<Rooted<ExternRef>>` |
1351 /// | `(ref extern)` | `Rooted<ExternRef>` |
1352 /// | `nullexternref` aka `(ref null noextern)` | `Option<NoExtern>` |
1353 /// | `(ref noextern)` | `NoExtern` |
1354 /// | `anyref` aka `(ref null any)` | `Option<Rooted<AnyRef>>` |
1355 /// | `(ref any)` | `Rooted<AnyRef>` |
1356 /// | `eqref` aka `(ref null eq)` | `Option<Rooted<EqRef>>` |
1357 /// | `(ref eq)` | `Rooted<EqRef>` |
1358 /// | `i31ref` aka `(ref null i31)` | `Option<I31>` |
1359 /// | `(ref i31)` | `I31` |
1360 /// | `structref` aka `(ref null struct)` | `Option<Rooted<StructRef>>` |
1361 /// | `(ref struct)` | `Rooted<StructRef>` |
1362 /// | `arrayref` aka `(ref null array)` | `Option<Rooted<ArrayRef>>` |
1363 /// | `(ref array)` | `Rooted<ArrayRef>` |
1364 /// | `nullref` aka `(ref null none)` | `Option<NoneRef>` |
1365 /// | `(ref none)` | `NoneRef` |
1366 /// | `funcref` aka `(ref null func)` | `Option<Func>` |
1367 /// | `(ref func)` | `Func` |
1368 /// | `(ref null <func type index>)` | `Option<Func>` |
1369 /// | `(ref <func type index>)` | `Func` |
1370 /// | `nullfuncref` aka `(ref null nofunc)` | `Option<NoFunc>` |
1371 /// | `(ref nofunc)` | `NoFunc` |
1372 /// | `v128` | `V128` on `x86-64` and `aarch64` only |
1373 ///
1374 /// (Note that this mapping is the same as that of [`Func::wrap`], and that
1375 /// anywhere a `Rooted<T>` appears, a `ManuallyRooted<T>` may also appear).
1376 ///
1377 /// Note that once the [`TypedFunc`] return value is acquired you'll use either
1378 /// [`TypedFunc::call`] or [`TypedFunc::call_async`] as necessary to actually invoke
1379 /// the function. This method does not invoke any WebAssembly code, it
1380 /// simply performs a typecheck before returning the [`TypedFunc`] value.
1381 ///
1382 /// This method also has a convenience wrapper as
1383 /// [`Instance::get_typed_func`](crate::Instance::get_typed_func) to
1384 /// directly get a typed function value from an
1385 /// [`Instance`](crate::Instance).
1386 ///
1387 /// ## Subtyping
1388 ///
1389 /// For result types, you can always use a supertype of the WebAssembly
1390 /// function's actual declared result type. For example, if the WebAssembly
1391 /// function was declared with type `(func (result nullfuncref))` you could
1392 /// successfully call `f.typed::<(), Option<Func>>()` because `Option<Func>`
1393 /// corresponds to `funcref`, which is a supertype of `nullfuncref`.
1394 ///
1395 /// For parameter types, you can always use a subtype of the WebAssembly
1396 /// function's actual declared parameter type. For example, if the
1397 /// WebAssembly function was declared with type `(func (param (ref null
1398 /// func)))` you could successfully call `f.typed::<Func, ()>()` because
1399 /// `Func` corresponds to `(ref func)`, which is a subtype of `(ref null
1400 /// func)`.
1401 ///
1402 /// Additionally, for functions which take a reference to a concrete type as
1403 /// a parameter, you can also use the concrete type's supertype. Consider a
1404 /// WebAssembly function that takes a reference to a function with a
1405 /// concrete type: `(ref null <func type index>)`. In this scenario, there
1406 /// is no static `wasmtime::Foo` Rust type that corresponds to that
1407 /// particular Wasm-defined concrete reference type because Wasm modules are
1408 /// loaded dynamically at runtime. You *could* do `f.typed::<Option<NoFunc>,
1409 /// ()>()`, and while that is correctly typed and valid, it is often overly
1410 /// restrictive. The only value you could call the resulting typed function
1411 /// with is the null function reference, but we'd like to call it with
1412 /// non-null function references that happen to be of the correct
1413 /// type. Therefore, `f.typed<Option<Func>, ()>()` is also allowed in this
1414 /// case, even though `Option<Func>` represents `(ref null func)` which is
1415 /// the supertype, not subtype, of `(ref null <func type index>)`. This does
1416 /// imply some minimal dynamic type checks in this case, but it is supported
1417 /// for better ergonomics, to enable passing non-null references into the
1418 /// function.
1419 ///
1420 /// # Errors
1421 ///
1422 /// This function will return an error if `Params` or `Results` does not
1423 /// match the native type of this WebAssembly function.
1424 ///
1425 /// # Panics
1426 ///
1427 /// This method will panic if `store` does not own this function.
1428 ///
1429 /// # Examples
1430 ///
1431 /// An end-to-end example of calling a function which takes no parameters
1432 /// and has no results:
1433 ///
1434 /// ```
1435 /// # use wasmtime::*;
1436 /// # fn main() -> anyhow::Result<()> {
1437 /// let engine = Engine::default();
1438 /// let mut store = Store::new(&engine, ());
1439 /// let module = Module::new(&engine, r#"(module (func (export "foo")))"#)?;
1440 /// let instance = Instance::new(&mut store, &module, &[])?;
1441 /// let foo = instance.get_func(&mut store, "foo").expect("export wasn't a function");
1442 ///
1443 /// // Note that this call can fail due to the typecheck not passing, but
1444 /// // in our case we statically know the module so we know this should
1445 /// // pass.
1446 /// let typed = foo.typed::<(), ()>(&store)?;
1447 ///
1448 /// // Note that this can fail if the wasm traps at runtime.
1449 /// typed.call(&mut store, ())?;
1450 /// # Ok(())
1451 /// # }
1452 /// ```
1453 ///
1454 /// You can also pass in multiple parameters and get a result back
1455 ///
1456 /// ```
1457 /// # use wasmtime::*;
1458 /// # fn foo(add: &Func, mut store: Store<()>) -> anyhow::Result<()> {
1459 /// let typed = add.typed::<(i32, i64), f32>(&store)?;
1460 /// assert_eq!(typed.call(&mut store, (1, 2))?, 3.0);
1461 /// # Ok(())
1462 /// # }
1463 /// ```
1464 ///
1465 /// and similarly if a function has multiple results you can bind that too
1466 ///
1467 /// ```
1468 /// # use wasmtime::*;
1469 /// # fn foo(add_with_overflow: &Func, mut store: Store<()>) -> anyhow::Result<()> {
1470 /// let typed = add_with_overflow.typed::<(u32, u32), (u32, i32)>(&store)?;
1471 /// let (result, overflow) = typed.call(&mut store, (u32::max_value(), 2))?;
1472 /// assert_eq!(result, 1);
1473 /// assert_eq!(overflow, 1);
1474 /// # Ok(())
1475 /// # }
1476 /// ```
1477 pub fn typed<Params, Results>(
1478 &self,
1479 store: impl AsContext,
1480 ) -> Result<TypedFunc<Params, Results>>
1481 where
1482 Params: WasmParams,
1483 Results: WasmResults,
1484 {
1485 // Type-check that the params/results are all valid
1486 let store = store.as_context().0;
1487 let ty = self.load_ty(store);
1488 Params::typecheck(store.engine(), ty.params(), TypeCheckPosition::Param)
1489 .context("type mismatch with parameters")?;
1490 Results::typecheck(store.engine(), ty.results(), TypeCheckPosition::Result)
1491 .context("type mismatch with results")?;
1492
1493 // and then we can construct the typed version of this function
1494 // (unsafely), which should be safe since we just did the type check above.
1495 unsafe { Ok(TypedFunc::_new_unchecked(store, *self)) }
1496 }
1497
1498 /// Get a stable hash key for this function.
1499 ///
1500 /// Even if the same underlying function is added to the `StoreData`
1501 /// multiple times and becomes multiple `wasmtime::Func`s, this hash key
1502 /// will be consistent across all of these functions.
1503 #[allow(dead_code)] // Not used yet, but added for consistency.
1504 pub(crate) fn hash_key(&self, store: &mut StoreOpaque) -> impl core::hash::Hash + Eq + use<> {
1505 self.vm_func_ref(store).as_ptr().addr()
1506 }
1507}
1508
1509/// Prepares for entrance into WebAssembly.
1510///
1511/// This function will set up context such that `closure` is allowed to call a
1512/// raw trampoline or a raw WebAssembly function. This *must* be called to do
1513/// things like catch traps and set up GC properly.
1514///
1515/// The `closure` provided receives a default "caller" `VMContext` parameter it
1516/// can pass to the called wasm function, if desired.
1517pub(crate) fn invoke_wasm_and_catch_traps<T>(
1518 store: &mut StoreContextMut<'_, T>,
1519 closure: impl FnMut(NonNull<VMContext>, Option<InterpreterRef<'_>>) -> bool,
1520) -> Result<()> {
1521 unsafe {
1522 // The `enter_wasm` call below will reset the store context's
1523 // `stack_chain` to a new `InitialStack`, pointing to the
1524 // stack-allocated `initial_stack_csi`.
1525 let mut initial_stack_csi = VMCommonStackInformation::running_default();
1526 // Stores some state of the runtime just before entering Wasm. Will be
1527 // restored upon exiting Wasm. Note that the `CallThreadState` that is
1528 // created by the `catch_traps` call below will store a pointer to this
1529 // stack-allocated `previous_runtime_state`.
1530 let previous_runtime_state = EntryStoreContext::enter_wasm(store, &mut initial_stack_csi);
1531
1532 if let Err(trap) = store.0.call_hook(CallHook::CallingWasm) {
1533 // `previous_runtime_state` implicitly dropped here
1534 return Err(trap);
1535 }
1536 let result = crate::runtime::vm::catch_traps(store, &previous_runtime_state, closure);
1537 core::mem::drop(previous_runtime_state);
1538 store.0.call_hook(CallHook::ReturningFromWasm)?;
1539 result.map_err(|t| crate::trap::from_runtime_box(store.0, t))
1540 }
1541}
1542
1543/// This type helps managing the state of the runtime when entering and exiting
1544/// Wasm. To this end, it contains a subset of the data in `VMStoreContext`.
1545/// Upon entering Wasm, it updates various runtime fields and their
1546/// original values saved in this struct. Upon exiting Wasm, the previous values
1547/// are restored.
1548pub(crate) struct EntryStoreContext {
1549 /// If set, contains value of `stack_limit` field to restore in
1550 /// `VMStoreContext` when exiting Wasm.
1551 pub stack_limit: Option<usize>,
1552 /// Contains value of `last_wasm_exit_pc` field to restore in
1553 /// `VMStoreContext` when exiting Wasm.
1554 pub last_wasm_exit_pc: usize,
1555 /// Contains value of `last_wasm_exit_fp` field to restore in
1556 /// `VMStoreContext` when exiting Wasm.
1557 pub last_wasm_exit_fp: usize,
1558 /// Contains value of `last_wasm_entry_fp` field to restore in
1559 /// `VMStoreContext` when exiting Wasm.
1560 pub last_wasm_entry_fp: usize,
1561 /// Contains value of `stack_chain` field to restore in
1562 /// `VMStoreContext` when exiting Wasm.
1563 pub stack_chain: VMStackChain,
1564
1565 /// We need a pointer to the runtime limits, so we can update them from
1566 /// `drop`/`exit_wasm`.
1567 vm_store_context: *const VMStoreContext,
1568}
1569
1570impl EntryStoreContext {
1571 /// This function is called to update and save state when
1572 /// WebAssembly is entered within the `Store`.
1573 ///
1574 /// This updates various fields such as:
1575 ///
1576 /// * The stack limit. This is what ensures that we limit the stack space
1577 /// allocated by WebAssembly code and it's relative to the initial stack
1578 /// pointer that called into wasm.
1579 ///
1580 /// It also saves the different last_wasm_* values in the `VMStoreContext`.
1581 pub fn enter_wasm<T>(
1582 store: &mut StoreContextMut<'_, T>,
1583 initial_stack_information: *mut VMCommonStackInformation,
1584 ) -> Self {
1585 let stack_limit;
1586
1587 // If this is a recursive call, e.g. our stack limit is already set, then
1588 // we may be able to skip this function.
1589 //
1590 // For synchronous stores there's nothing else to do because all wasm calls
1591 // happen synchronously and on the same stack. This means that the previous
1592 // stack limit will suffice for the next recursive call.
1593 //
1594 // For asynchronous stores then each call happens on a separate native
1595 // stack. This means that the previous stack limit is no longer relevant
1596 // because we're on a separate stack.
1597 if unsafe { *store.0.vm_store_context().stack_limit.get() } != usize::MAX
1598 && !store.0.async_support()
1599 {
1600 stack_limit = None;
1601 }
1602 // Ignore this stack pointer business on miri since we can't execute wasm
1603 // anyway and the concept of a stack pointer on miri is a bit nebulous
1604 // regardless.
1605 else if cfg!(miri) {
1606 stack_limit = None;
1607 } else {
1608 // When Cranelift has support for the host then we might be running native
1609 // compiled code meaning we need to read the actual stack pointer. If
1610 // Cranelift can't be used though then we're guaranteed to be running pulley
1611 // in which case this stack pointer isn't actually used as Pulley has custom
1612 // mechanisms for stack overflow.
1613 #[cfg(has_host_compiler_backend)]
1614 let stack_pointer = crate::runtime::vm::get_stack_pointer();
1615 #[cfg(not(has_host_compiler_backend))]
1616 let stack_pointer = {
1617 use wasmtime_environ::TripleExt;
1618 debug_assert!(store.engine().target().is_pulley());
1619 usize::MAX
1620 };
1621
1622 // Determine the stack pointer where, after which, any wasm code will
1623 // immediately trap. This is checked on the entry to all wasm functions.
1624 //
1625 // Note that this isn't 100% precise. We are requested to give wasm
1626 // `max_wasm_stack` bytes, but what we're actually doing is giving wasm
1627 // probably a little less than `max_wasm_stack` because we're
1628 // calculating the limit relative to this function's approximate stack
1629 // pointer. Wasm will be executed on a frame beneath this one (or next
1630 // to it). In any case it's expected to be at most a few hundred bytes
1631 // of slop one way or another. When wasm is typically given a MB or so
1632 // (a million bytes) the slop shouldn't matter too much.
1633 //
1634 // After we've got the stack limit then we store it into the `stack_limit`
1635 // variable.
1636 let wasm_stack_limit = stack_pointer
1637 .checked_sub(store.engine().config().max_wasm_stack)
1638 .unwrap();
1639 let prev_stack = unsafe {
1640 mem::replace(
1641 &mut *store.0.vm_store_context().stack_limit.get(),
1642 wasm_stack_limit,
1643 )
1644 };
1645 stack_limit = Some(prev_stack);
1646 }
1647
1648 unsafe {
1649 let last_wasm_exit_pc = *store.0.vm_store_context().last_wasm_exit_pc.get();
1650 let last_wasm_exit_fp = *store.0.vm_store_context().last_wasm_exit_fp.get();
1651 let last_wasm_entry_fp = *store.0.vm_store_context().last_wasm_entry_fp.get();
1652
1653 let stack_chain = (*store.0.vm_store_context().stack_chain.get()).clone();
1654
1655 let new_stack_chain = VMStackChain::InitialStack(initial_stack_information);
1656 *store.0.vm_store_context().stack_chain.get() = new_stack_chain;
1657
1658 let vm_store_context = store.0.vm_store_context();
1659
1660 Self {
1661 stack_limit,
1662 last_wasm_exit_pc,
1663 last_wasm_exit_fp,
1664 last_wasm_entry_fp,
1665 stack_chain,
1666 vm_store_context,
1667 }
1668 }
1669 }
1670
1671 /// This function restores the values stored in this struct. We invoke this
1672 /// function through this type's `Drop` implementation. This ensures that we
1673 /// even restore the values if we unwind the stack (e.g., because we are
1674 /// panicing out of a Wasm execution).
1675 #[inline]
1676 fn exit_wasm(&mut self) {
1677 unsafe {
1678 if let Some(limit) = self.stack_limit {
1679 *(&*self.vm_store_context).stack_limit.get() = limit;
1680 }
1681
1682 *(*self.vm_store_context).last_wasm_exit_fp.get() = self.last_wasm_exit_fp;
1683 *(*self.vm_store_context).last_wasm_exit_pc.get() = self.last_wasm_exit_pc;
1684 *(*self.vm_store_context).last_wasm_entry_fp.get() = self.last_wasm_entry_fp;
1685 *(*self.vm_store_context).stack_chain.get() = self.stack_chain.clone();
1686 }
1687 }
1688}
1689
1690impl Drop for EntryStoreContext {
1691 #[inline]
1692 fn drop(&mut self) {
1693 self.exit_wasm();
1694 }
1695}
1696
1697/// A trait implemented for types which can be returned from closures passed to
1698/// [`Func::wrap`] and friends.
1699///
1700/// This trait should not be implemented by user types. This trait may change at
1701/// any time internally. The types which implement this trait, however, are
1702/// stable over time.
1703///
1704/// For more information see [`Func::wrap`]
1705pub unsafe trait WasmRet {
1706 // Same as `WasmTy::compatible_with_store`.
1707 #[doc(hidden)]
1708 fn compatible_with_store(&self, store: &StoreOpaque) -> bool;
1709
1710 /// Stores this return value into the `ptr` specified using the rooted
1711 /// `store`.
1712 ///
1713 /// Traps are communicated through the `Result<_>` return value.
1714 ///
1715 /// # Unsafety
1716 ///
1717 /// This method is unsafe as `ptr` must have the correct length to store
1718 /// this result. This property is only checked in debug mode, not in release
1719 /// mode.
1720 #[doc(hidden)]
1721 unsafe fn store(
1722 self,
1723 store: &mut AutoAssertNoGc<'_>,
1724 ptr: &mut [MaybeUninit<ValRaw>],
1725 ) -> Result<()>;
1726
1727 #[doc(hidden)]
1728 fn func_type(engine: &Engine, params: impl Iterator<Item = ValType>) -> FuncType;
1729 #[doc(hidden)]
1730 fn may_gc() -> bool;
1731
1732 // Utilities used to convert an instance of this type to a `Result`
1733 // explicitly, used when wrapping async functions which always bottom-out
1734 // in a function that returns a trap because futures can be cancelled.
1735 #[doc(hidden)]
1736 type Fallible: WasmRet;
1737 #[doc(hidden)]
1738 fn into_fallible(self) -> Self::Fallible;
1739 #[doc(hidden)]
1740 fn fallible_from_error(error: Error) -> Self::Fallible;
1741}
1742
1743unsafe impl<T> WasmRet for T
1744where
1745 T: WasmTy,
1746{
1747 type Fallible = Result<T>;
1748
1749 fn compatible_with_store(&self, store: &StoreOpaque) -> bool {
1750 <Self as WasmTy>::compatible_with_store(self, store)
1751 }
1752
1753 unsafe fn store(
1754 self,
1755 store: &mut AutoAssertNoGc<'_>,
1756 ptr: &mut [MaybeUninit<ValRaw>],
1757 ) -> Result<()> {
1758 debug_assert!(ptr.len() > 0);
1759 <Self as WasmTy>::store(self, store, ptr.get_unchecked_mut(0))
1760 }
1761
1762 fn may_gc() -> bool {
1763 T::may_gc()
1764 }
1765
1766 fn func_type(engine: &Engine, params: impl Iterator<Item = ValType>) -> FuncType {
1767 FuncType::new(engine, params, Some(<Self as WasmTy>::valtype()))
1768 }
1769
1770 fn into_fallible(self) -> Result<T> {
1771 Ok(self)
1772 }
1773
1774 fn fallible_from_error(error: Error) -> Result<T> {
1775 Err(error)
1776 }
1777}
1778
1779unsafe impl<T> WasmRet for Result<T>
1780where
1781 T: WasmRet,
1782{
1783 type Fallible = Self;
1784
1785 fn compatible_with_store(&self, store: &StoreOpaque) -> bool {
1786 match self {
1787 Ok(x) => <T as WasmRet>::compatible_with_store(x, store),
1788 Err(_) => true,
1789 }
1790 }
1791
1792 unsafe fn store(
1793 self,
1794 store: &mut AutoAssertNoGc<'_>,
1795 ptr: &mut [MaybeUninit<ValRaw>],
1796 ) -> Result<()> {
1797 self.and_then(|val| val.store(store, ptr))
1798 }
1799
1800 fn may_gc() -> bool {
1801 T::may_gc()
1802 }
1803
1804 fn func_type(engine: &Engine, params: impl Iterator<Item = ValType>) -> FuncType {
1805 T::func_type(engine, params)
1806 }
1807
1808 fn into_fallible(self) -> Result<T> {
1809 self
1810 }
1811
1812 fn fallible_from_error(error: Error) -> Result<T> {
1813 Err(error)
1814 }
1815}
1816
1817macro_rules! impl_wasm_host_results {
1818 ($n:tt $($t:ident)*) => (
1819 #[allow(non_snake_case)]
1820 unsafe impl<$($t),*> WasmRet for ($($t,)*)
1821 where
1822 $($t: WasmTy,)*
1823 {
1824 type Fallible = Result<Self>;
1825
1826 #[inline]
1827 fn compatible_with_store(&self, _store: &StoreOpaque) -> bool {
1828 let ($($t,)*) = self;
1829 $( $t.compatible_with_store(_store) && )* true
1830 }
1831
1832 #[inline]
1833 unsafe fn store(
1834 self,
1835 _store: &mut AutoAssertNoGc<'_>,
1836 _ptr: &mut [MaybeUninit<ValRaw>],
1837 ) -> Result<()> {
1838 let ($($t,)*) = self;
1839 let mut _cur = 0;
1840 $(
1841 debug_assert!(_cur < _ptr.len());
1842 let val = _ptr.get_unchecked_mut(_cur);
1843 _cur += 1;
1844 WasmTy::store($t, _store, val)?;
1845 )*
1846 Ok(())
1847 }
1848
1849 #[doc(hidden)]
1850 fn may_gc() -> bool {
1851 $( $t::may_gc() || )* false
1852 }
1853
1854 fn func_type(engine: &Engine, params: impl Iterator<Item = ValType>) -> FuncType {
1855 FuncType::new(
1856 engine,
1857 params,
1858 IntoIterator::into_iter([$($t::valtype(),)*]),
1859 )
1860 }
1861
1862 #[inline]
1863 fn into_fallible(self) -> Result<Self> {
1864 Ok(self)
1865 }
1866
1867 #[inline]
1868 fn fallible_from_error(error: Error) -> Result<Self> {
1869 Err(error)
1870 }
1871 }
1872 )
1873}
1874
1875for_each_function_signature!(impl_wasm_host_results);
1876
1877/// Internal trait implemented for all arguments that can be passed to
1878/// [`Func::wrap`] and [`Linker::func_wrap`](crate::Linker::func_wrap).
1879///
1880/// This trait should not be implemented by external users, it's only intended
1881/// as an implementation detail of this crate.
1882pub trait IntoFunc<T, Params, Results>: Send + Sync + 'static {
1883 /// Convert this function into a `VM{Array,Native}CallHostFuncContext` and
1884 /// internal `VMFuncRef`.
1885 #[doc(hidden)]
1886 fn into_func(self, engine: &Engine) -> HostContext;
1887}
1888
1889macro_rules! impl_into_func {
1890 ($num:tt $arg:ident) => {
1891 // Implement for functions without a leading `&Caller` parameter,
1892 // delegating to the implementation below which does have the leading
1893 // `Caller` parameter.
1894 #[allow(non_snake_case)]
1895 impl<T, F, $arg, R> IntoFunc<T, $arg, R> for F
1896 where
1897 F: Fn($arg) -> R + Send + Sync + 'static,
1898 $arg: WasmTy,
1899 R: WasmRet,
1900 T: 'static,
1901 {
1902 fn into_func(self, engine: &Engine) -> HostContext {
1903 let f = move |_: Caller<'_, T>, $arg: $arg| {
1904 self($arg)
1905 };
1906
1907 f.into_func(engine)
1908 }
1909 }
1910
1911 #[allow(non_snake_case)]
1912 impl<T, F, $arg, R> IntoFunc<T, (Caller<'_, T>, $arg), R> for F
1913 where
1914 F: Fn(Caller<'_, T>, $arg) -> R + Send + Sync + 'static,
1915 $arg: WasmTy,
1916 R: WasmRet,
1917 T: 'static,
1918 {
1919 fn into_func(self, engine: &Engine) -> HostContext {
1920 HostContext::from_closure(engine, move |caller: Caller<'_, T>, ($arg,)| {
1921 self(caller, $arg)
1922 })
1923 }
1924 }
1925 };
1926 ($num:tt $($args:ident)*) => {
1927 // Implement for functions without a leading `&Caller` parameter,
1928 // delegating to the implementation below which does have the leading
1929 // `Caller` parameter.
1930 #[allow(non_snake_case)]
1931 impl<T, F, $($args,)* R> IntoFunc<T, ($($args,)*), R> for F
1932 where
1933 F: Fn($($args),*) -> R + Send + Sync + 'static,
1934 $($args: WasmTy,)*
1935 R: WasmRet,
1936 T: 'static,
1937 {
1938 fn into_func(self, engine: &Engine) -> HostContext {
1939 let f = move |_: Caller<'_, T>, $($args:$args),*| {
1940 self($($args),*)
1941 };
1942
1943 f.into_func(engine)
1944 }
1945 }
1946
1947 #[allow(non_snake_case)]
1948 impl<T, F, $($args,)* R> IntoFunc<T, (Caller<'_, T>, $($args,)*), R> for F
1949 where
1950 F: Fn(Caller<'_, T>, $($args),*) -> R + Send + Sync + 'static,
1951 $($args: WasmTy,)*
1952 R: WasmRet,
1953 T: 'static,
1954 {
1955 fn into_func(self, engine: &Engine) -> HostContext {
1956 HostContext::from_closure(engine, move |caller: Caller<'_, T>, ( $( $args ),* )| {
1957 self(caller, $( $args ),* )
1958 })
1959 }
1960 }
1961 }
1962}
1963
1964for_each_function_signature!(impl_into_func);
1965
1966/// Trait implemented for various tuples made up of types which implement
1967/// [`WasmTy`] that can be passed to [`Func::wrap_inner`] and
1968/// [`HostContext::from_closure`].
1969pub unsafe trait WasmTyList {
1970 /// Get the value type that each Type in the list represents.
1971 fn valtypes() -> impl Iterator<Item = ValType>;
1972
1973 // Load a version of `Self` from the `values` provided.
1974 //
1975 // # Safety
1976 //
1977 // This function is unsafe as it's up to the caller to ensure that `values` are
1978 // valid for this given type.
1979 #[doc(hidden)]
1980 unsafe fn load(store: &mut AutoAssertNoGc<'_>, values: &mut [MaybeUninit<ValRaw>]) -> Self;
1981
1982 #[doc(hidden)]
1983 fn may_gc() -> bool;
1984}
1985
1986macro_rules! impl_wasm_ty_list {
1987 ($num:tt $($args:ident)*) => (
1988 #[allow(non_snake_case)]
1989 unsafe impl<$($args),*> WasmTyList for ($($args,)*)
1990 where
1991 $($args: WasmTy,)*
1992 {
1993 fn valtypes() -> impl Iterator<Item = ValType> {
1994 IntoIterator::into_iter([$($args::valtype(),)*])
1995 }
1996
1997 unsafe fn load(_store: &mut AutoAssertNoGc<'_>, _values: &mut [MaybeUninit<ValRaw>]) -> Self {
1998 let mut _cur = 0;
1999 ($({
2000 debug_assert!(_cur < _values.len());
2001 let ptr = _values.get_unchecked(_cur).assume_init_ref();
2002 _cur += 1;
2003 $args::load(_store, ptr)
2004 },)*)
2005 }
2006
2007 fn may_gc() -> bool {
2008 $( $args::may_gc() || )* false
2009 }
2010 }
2011 );
2012}
2013
2014for_each_function_signature!(impl_wasm_ty_list);
2015
2016/// A structure representing the caller's context when creating a function
2017/// via [`Func::wrap`].
2018///
2019/// This structure can be taken as the first parameter of a closure passed to
2020/// [`Func::wrap`] or other constructors, and serves two purposes:
2021///
2022/// * First consumers can use [`Caller<'_, T>`](crate::Caller) to get access to
2023/// [`StoreContextMut<'_, T>`](crate::StoreContextMut) and/or get access to
2024/// `T` itself. This means that the [`Caller`] type can serve as a proxy to
2025/// the original [`Store`](crate::Store) itself and is used to satisfy
2026/// [`AsContext`] and [`AsContextMut`] bounds.
2027///
2028/// * Second a [`Caller`] can be used as the name implies, learning about the
2029/// caller's context, namely it's exported memory and exported functions. This
2030/// allows functions which take pointers as arguments to easily read the
2031/// memory the pointers point into, or if a function is expected to call
2032/// malloc in the wasm module to reserve space for the output you can do that.
2033///
2034/// Host functions which want access to [`Store`](crate::Store)-level state are
2035/// recommended to use this type.
2036pub struct Caller<'a, T: 'static> {
2037 pub(crate) store: StoreContextMut<'a, T>,
2038 caller: Instance,
2039}
2040
2041impl<T> Caller<'_, T> {
2042 unsafe fn with<F, R>(caller: NonNull<VMContext>, f: F) -> R
2043 where
2044 // The closure must be valid for any `Caller` it is given; it doesn't
2045 // get to choose the `Caller`'s lifetime.
2046 F: for<'a> FnOnce(Caller<'a, T>) -> R,
2047 // And the return value must not borrow from the caller/store.
2048 R: 'static,
2049 {
2050 crate::runtime::vm::InstanceAndStore::from_vmctx(caller, |pair| {
2051 let (instance, mut store) = pair.unpack_context_mut::<T>();
2052 let caller = Instance::from_wasmtime(instance.id(), store.0);
2053
2054 let (gc_lifo_scope, ret) = {
2055 let gc_lifo_scope = store.0.gc_roots().enter_lifo_scope();
2056
2057 let ret = f(Caller {
2058 store: store.as_context_mut(),
2059 caller,
2060 });
2061
2062 (gc_lifo_scope, ret)
2063 };
2064
2065 // Safe to recreate a mutable borrow of the store because `ret`
2066 // cannot be borrowing from the store.
2067 store.0.exit_gc_lifo_scope(gc_lifo_scope);
2068
2069 ret
2070 })
2071 }
2072
2073 fn sub_caller(&mut self) -> Caller<'_, T> {
2074 Caller {
2075 store: self.store.as_context_mut(),
2076 caller: self.caller,
2077 }
2078 }
2079
2080 /// Looks up an export from the caller's module by the `name` given.
2081 ///
2082 /// This is a low-level function that's typically used to implement passing
2083 /// of pointers or indices between core Wasm instances, where the callee
2084 /// needs to consult the caller's exports to perform memory management and
2085 /// resolve the references.
2086 ///
2087 /// For comparison, in components, the component model handles translating
2088 /// arguments from one component instance to another and managing memory, so
2089 /// that callees don't need to be aware of their callers, which promotes
2090 /// virtualizability of APIs.
2091 ///
2092 /// # Return
2093 ///
2094 /// If an export with the `name` provided was found, then it is returned as an
2095 /// `Extern`. There are a number of situations, however, where the export may not
2096 /// be available:
2097 ///
2098 /// * The caller instance may not have an export named `name`
2099 /// * There may not be a caller available, for example if `Func` was called
2100 /// directly from host code.
2101 ///
2102 /// It's recommended to take care when calling this API and gracefully
2103 /// handling a `None` return value.
2104 pub fn get_export(&mut self, name: &str) -> Option<Extern> {
2105 // All instances created have a `host_state` with a pointer pointing
2106 // back to themselves. If this caller doesn't have that `host_state`
2107 // then it probably means it was a host-created object like `Func::new`
2108 // which doesn't have any exports we want to return anyway.
2109 self.caller.get_export(&mut self.store, name)
2110 }
2111
2112 /// Looks up an exported [`Extern`] value by a [`ModuleExport`] value.
2113 ///
2114 /// This is similar to [`Self::get_export`] but uses a [`ModuleExport`] value to avoid
2115 /// string lookups where possible. [`ModuleExport`]s can be obtained by calling
2116 /// [`Module::get_export_index`] on the [`Module`] that an instance was instantiated with.
2117 ///
2118 /// This method will search the module for an export with a matching entity index and return
2119 /// the value, if found.
2120 ///
2121 /// Returns `None` if there was no export with a matching entity index.
2122 /// # Panics
2123 ///
2124 /// Panics if `store` does not own this instance.
2125 ///
2126 /// # Usage
2127 /// ```
2128 /// use std::str;
2129 ///
2130 /// # use wasmtime::*;
2131 /// # fn main() -> anyhow::Result<()> {
2132 /// # let mut store = Store::default();
2133 ///
2134 /// let module = Module::new(
2135 /// store.engine(),
2136 /// r#"
2137 /// (module
2138 /// (import "" "" (func $log_str (param i32 i32)))
2139 /// (func (export "foo")
2140 /// i32.const 4 ;; ptr
2141 /// i32.const 13 ;; len
2142 /// call $log_str)
2143 /// (memory (export "memory") 1)
2144 /// (data (i32.const 4) "Hello, world!"))
2145 /// "#,
2146 /// )?;
2147 ///
2148 /// let Some(module_export) = module.get_export_index("memory") else {
2149 /// anyhow::bail!("failed to find `memory` export in module");
2150 /// };
2151 ///
2152 /// let log_str = Func::wrap(&mut store, move |mut caller: Caller<'_, ()>, ptr: i32, len: i32| {
2153 /// let mem = match caller.get_module_export(&module_export) {
2154 /// Some(Extern::Memory(mem)) => mem,
2155 /// _ => anyhow::bail!("failed to find host memory"),
2156 /// };
2157 /// let data = mem.data(&caller)
2158 /// .get(ptr as u32 as usize..)
2159 /// .and_then(|arr| arr.get(..len as u32 as usize));
2160 /// let string = match data {
2161 /// Some(data) => match str::from_utf8(data) {
2162 /// Ok(s) => s,
2163 /// Err(_) => anyhow::bail!("invalid utf-8"),
2164 /// },
2165 /// None => anyhow::bail!("pointer/length out of bounds"),
2166 /// };
2167 /// assert_eq!(string, "Hello, world!");
2168 /// println!("{}", string);
2169 /// Ok(())
2170 /// });
2171 /// let instance = Instance::new(&mut store, &module, &[log_str.into()])?;
2172 /// let foo = instance.get_typed_func::<(), ()>(&mut store, "foo")?;
2173 /// foo.call(&mut store, ())?;
2174 /// # Ok(())
2175 /// # }
2176 /// ```
2177 pub fn get_module_export(&mut self, export: &ModuleExport) -> Option<Extern> {
2178 self.caller.get_module_export(&mut self.store, export)
2179 }
2180
2181 /// Access the underlying data owned by this `Store`.
2182 ///
2183 /// Same as [`Store::data`](crate::Store::data)
2184 pub fn data(&self) -> &T {
2185 self.store.data()
2186 }
2187
2188 /// Access the underlying data owned by this `Store`.
2189 ///
2190 /// Same as [`Store::data_mut`](crate::Store::data_mut)
2191 pub fn data_mut(&mut self) -> &mut T {
2192 self.store.data_mut()
2193 }
2194
2195 /// Returns the underlying [`Engine`] this store is connected to.
2196 pub fn engine(&self) -> &Engine {
2197 self.store.engine()
2198 }
2199
2200 /// Perform garbage collection.
2201 ///
2202 /// Same as [`Store::gc`](crate::Store::gc).
2203 #[cfg(feature = "gc")]
2204 pub fn gc(&mut self, why: Option<&crate::GcHeapOutOfMemory<()>>) {
2205 self.store.gc(why);
2206 }
2207
2208 /// Perform garbage collection asynchronously.
2209 ///
2210 /// Same as [`Store::gc_async`](crate::Store::gc_async).
2211 #[cfg(all(feature = "async", feature = "gc"))]
2212 pub async fn gc_async(&mut self, why: Option<&crate::GcHeapOutOfMemory<()>>) -> Result<()>
2213 where
2214 T: Send + 'static,
2215 {
2216 self.store.gc_async(why).await
2217 }
2218
2219 /// Returns the remaining fuel in the store.
2220 ///
2221 /// For more information see [`Store::get_fuel`](crate::Store::get_fuel)
2222 pub fn get_fuel(&self) -> Result<u64> {
2223 self.store.get_fuel()
2224 }
2225
2226 /// Set the amount of fuel in this store to be consumed when executing wasm code.
2227 ///
2228 /// For more information see [`Store::set_fuel`](crate::Store::set_fuel)
2229 pub fn set_fuel(&mut self, fuel: u64) -> Result<()> {
2230 self.store.set_fuel(fuel)
2231 }
2232
2233 /// Configures this `Store` to yield while executing futures every N units of fuel.
2234 ///
2235 /// For more information see
2236 /// [`Store::fuel_async_yield_interval`](crate::Store::fuel_async_yield_interval)
2237 pub fn fuel_async_yield_interval(&mut self, interval: Option<u64>) -> Result<()> {
2238 self.store.fuel_async_yield_interval(interval)
2239 }
2240}
2241
2242impl<T: 'static> AsContext for Caller<'_, T> {
2243 type Data = T;
2244 fn as_context(&self) -> StoreContext<'_, T> {
2245 self.store.as_context()
2246 }
2247}
2248
2249impl<T: 'static> AsContextMut for Caller<'_, T> {
2250 fn as_context_mut(&mut self) -> StoreContextMut<'_, T> {
2251 self.store.as_context_mut()
2252 }
2253}
2254
2255// State stored inside a `VMArrayCallHostFuncContext`.
2256struct HostFuncState<F> {
2257 // The actual host function.
2258 func: F,
2259
2260 // NB: We have to keep our `VMSharedTypeIndex` registered in the engine for
2261 // as long as this function exists.
2262 #[allow(dead_code)]
2263 ty: RegisteredType,
2264}
2265
2266#[doc(hidden)]
2267pub enum HostContext {
2268 Array(StoreBox<VMArrayCallHostFuncContext>),
2269}
2270
2271impl From<StoreBox<VMArrayCallHostFuncContext>> for HostContext {
2272 fn from(ctx: StoreBox<VMArrayCallHostFuncContext>) -> Self {
2273 HostContext::Array(ctx)
2274 }
2275}
2276
2277impl HostContext {
2278 fn from_closure<F, T, P, R>(engine: &Engine, func: F) -> Self
2279 where
2280 F: Fn(Caller<'_, T>, P) -> R + Send + Sync + 'static,
2281 P: WasmTyList,
2282 R: WasmRet,
2283 T: 'static,
2284 {
2285 let ty = R::func_type(engine, None::<ValType>.into_iter().chain(P::valtypes()));
2286 let type_index = ty.type_index();
2287
2288 let array_call = Self::array_call_trampoline::<T, F, P, R>;
2289
2290 let ctx = unsafe {
2291 VMArrayCallHostFuncContext::new(
2292 array_call,
2293 type_index,
2294 Box::new(HostFuncState {
2295 func,
2296 ty: ty.into_registered_type(),
2297 }),
2298 )
2299 };
2300
2301 ctx.into()
2302 }
2303
2304 unsafe extern "C" fn array_call_trampoline<T, F, P, R>(
2305 callee_vmctx: NonNull<VMOpaqueContext>,
2306 caller_vmctx: NonNull<VMOpaqueContext>,
2307 args: NonNull<ValRaw>,
2308 args_len: usize,
2309 ) -> bool
2310 where
2311 F: Fn(Caller<'_, T>, P) -> R + 'static,
2312 P: WasmTyList,
2313 R: WasmRet,
2314 T: 'static,
2315 {
2316 // Note that this function is intentionally scoped into a
2317 // separate closure. Handling traps and panics will involve
2318 // longjmp-ing from this function which means we won't run
2319 // destructors. As a result anything requiring a destructor
2320 // should be part of this closure, and the long-jmp-ing
2321 // happens after the closure in handling the result.
2322 let run = move |mut caller: Caller<'_, T>| {
2323 let mut args =
2324 NonNull::slice_from_raw_parts(args.cast::<MaybeUninit<ValRaw>>(), args_len);
2325 let vmctx = VMArrayCallHostFuncContext::from_opaque(callee_vmctx);
2326 let state = vmctx.as_ref().host_state();
2327
2328 // Double-check ourselves in debug mode, but we control
2329 // the `Any` here so an unsafe downcast should also
2330 // work.
2331 debug_assert!(state.is::<HostFuncState<F>>());
2332 let state = &*(state as *const _ as *const HostFuncState<F>);
2333 let func = &state.func;
2334
2335 let ret = 'ret: {
2336 if let Err(trap) = caller.store.0.call_hook(CallHook::CallingHost) {
2337 break 'ret R::fallible_from_error(trap);
2338 }
2339
2340 let mut store = if P::may_gc() {
2341 AutoAssertNoGc::new(caller.store.0)
2342 } else {
2343 unsafe { AutoAssertNoGc::disabled(caller.store.0) }
2344 };
2345 let params = P::load(&mut store, args.as_mut());
2346 let _ = &mut store;
2347 drop(store);
2348
2349 let r = func(caller.sub_caller(), params);
2350 if let Err(trap) = caller.store.0.call_hook(CallHook::ReturningFromHost) {
2351 break 'ret R::fallible_from_error(trap);
2352 }
2353 r.into_fallible()
2354 };
2355
2356 if !ret.compatible_with_store(caller.store.0) {
2357 bail!("host function attempted to return cross-`Store` value to Wasm")
2358 } else {
2359 let mut store = if R::may_gc() {
2360 AutoAssertNoGc::new(caller.store.0)
2361 } else {
2362 unsafe { AutoAssertNoGc::disabled(caller.store.0) }
2363 };
2364 let ret = ret.store(&mut store, args.as_mut())?;
2365 Ok(ret)
2366 }
2367 };
2368
2369 // With nothing else on the stack move `run` into this
2370 // closure and then run it as part of `Caller::with`.
2371 crate::runtime::vm::catch_unwind_and_record_trap(move || {
2372 let caller_vmctx = VMContext::from_opaque(caller_vmctx);
2373 Caller::with(caller_vmctx, run)
2374 })
2375 }
2376}
2377
2378/// Representation of a host-defined function.
2379///
2380/// This is used for `Func::new` but also for `Linker`-defined functions. For
2381/// `Func::new` this is stored within a `Store`, and for `Linker`-defined
2382/// functions they wrap this up in `Arc` to enable shared ownership of this
2383/// across many stores.
2384///
2385/// Technically this structure needs a `<T>` type parameter to connect to the
2386/// `Store<T>` itself, but that's an unsafe contract of using this for now
2387/// rather than part of the struct type (to avoid `Func<T>` in the API).
2388pub(crate) struct HostFunc {
2389 ctx: HostContext,
2390
2391 // Stored to unregister this function's signature with the engine when this
2392 // is dropped.
2393 engine: Engine,
2394}
2395
2396impl core::fmt::Debug for HostFunc {
2397 fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
2398 f.debug_struct("HostFunc").finish_non_exhaustive()
2399 }
2400}
2401
2402impl HostFunc {
2403 /// Analog of [`Func::new`]
2404 ///
2405 /// # Panics
2406 ///
2407 /// Panics if the given function type is not associated with the given
2408 /// engine.
2409 pub fn new<T>(
2410 engine: &Engine,
2411 ty: FuncType,
2412 func: impl Fn(Caller<'_, T>, &[Val], &mut [Val]) -> Result<()> + Send + Sync + 'static,
2413 ) -> Self
2414 where
2415 T: 'static,
2416 {
2417 assert!(ty.comes_from_same_engine(engine));
2418 let ty_clone = ty.clone();
2419 unsafe {
2420 HostFunc::new_unchecked(engine, ty, move |caller, values| {
2421 Func::invoke_host_func_for_wasm(caller, &ty_clone, values, &func)
2422 })
2423 }
2424 }
2425
2426 /// Analog of [`Func::new_unchecked`]
2427 ///
2428 /// # Panics
2429 ///
2430 /// Panics if the given function type is not associated with the given
2431 /// engine.
2432 pub unsafe fn new_unchecked<T>(
2433 engine: &Engine,
2434 ty: FuncType,
2435 func: impl Fn(Caller<'_, T>, &mut [ValRaw]) -> Result<()> + Send + Sync + 'static,
2436 ) -> Self
2437 where
2438 T: 'static,
2439 {
2440 assert!(ty.comes_from_same_engine(engine));
2441 let func = move |caller_vmctx, values: &mut [ValRaw]| {
2442 Caller::<T>::with(caller_vmctx, |mut caller| {
2443 caller.store.0.call_hook(CallHook::CallingHost)?;
2444 let result = func(caller.sub_caller(), values)?;
2445 caller.store.0.call_hook(CallHook::ReturningFromHost)?;
2446 Ok(result)
2447 })
2448 };
2449 let ctx = crate::trampoline::create_array_call_function(&ty, func)
2450 .expect("failed to create function");
2451 HostFunc::_new(engine, ctx.into())
2452 }
2453
2454 /// Analog of [`Func::wrap_inner`]
2455 #[cfg(any(feature = "component-model", feature = "async"))]
2456 pub fn wrap_inner<F, T, Params, Results>(engine: &Engine, func: F) -> Self
2457 where
2458 F: Fn(Caller<'_, T>, Params) -> Results + Send + Sync + 'static,
2459 Params: WasmTyList,
2460 Results: WasmRet,
2461 T: 'static,
2462 {
2463 let ctx = HostContext::from_closure(engine, func);
2464 HostFunc::_new(engine, ctx)
2465 }
2466
2467 /// Analog of [`Func::wrap`]
2468 pub fn wrap<T, Params, Results>(
2469 engine: &Engine,
2470 func: impl IntoFunc<T, Params, Results>,
2471 ) -> Self
2472 where
2473 T: 'static,
2474 {
2475 let ctx = func.into_func(engine);
2476 HostFunc::_new(engine, ctx)
2477 }
2478
2479 /// Requires that this function's signature is already registered within
2480 /// `Engine`. This happens automatically during the above two constructors.
2481 fn _new(engine: &Engine, ctx: HostContext) -> Self {
2482 HostFunc {
2483 ctx,
2484 engine: engine.clone(),
2485 }
2486 }
2487
2488 /// Inserts this `HostFunc` into a `Store`, returning the `Func` pointing to
2489 /// it.
2490 ///
2491 /// # Unsafety
2492 ///
2493 /// Can only be inserted into stores with a matching `T` relative to when
2494 /// this `HostFunc` was first created.
2495 pub unsafe fn to_func(self: &Arc<Self>, store: &mut StoreOpaque) -> Func {
2496 self.validate_store(store);
2497 let (funcrefs, modules) = store.func_refs_and_modules();
2498 let funcref = funcrefs.push_arc_host(self.clone(), modules);
2499 Func::from_vm_func_ref(store, funcref)
2500 }
2501
2502 /// Inserts this `HostFunc` into a `Store`, returning the `Func` pointing to
2503 /// it.
2504 ///
2505 /// This function is similar to, but not equivalent, to `HostFunc::to_func`.
2506 /// Notably this function requires that the `Arc<Self>` pointer is otherwise
2507 /// rooted within the `StoreOpaque` via another means. When in doubt use
2508 /// `to_func` above as it's safer.
2509 ///
2510 /// # Unsafety
2511 ///
2512 /// Can only be inserted into stores with a matching `T` relative to when
2513 /// this `HostFunc` was first created.
2514 ///
2515 /// Additionally the `&Arc<Self>` is not cloned in this function. Instead a
2516 /// raw pointer to `Self` is stored within the `Store` for this function.
2517 /// The caller must arrange for the `Arc<Self>` to be "rooted" in the store
2518 /// provided via another means, probably by pushing to
2519 /// `StoreOpaque::rooted_host_funcs`.
2520 ///
2521 /// Similarly, the caller must arrange for `rooted_func_ref` to be rooted in
2522 /// the same store.
2523 pub unsafe fn to_func_store_rooted(
2524 self: &Arc<Self>,
2525 store: &mut StoreOpaque,
2526 rooted_func_ref: Option<NonNull<VMFuncRef>>,
2527 ) -> Func {
2528 self.validate_store(store);
2529
2530 match rooted_func_ref {
2531 Some(funcref) => {
2532 debug_assert!(funcref.as_ref().wasm_call.is_some());
2533 Func::from_vm_func_ref(store, funcref)
2534 }
2535 None => {
2536 debug_assert!(self.func_ref().wasm_call.is_some());
2537 Func::from_vm_func_ref(store, self.func_ref().into())
2538 }
2539 }
2540 }
2541
2542 /// Same as [`HostFunc::to_func`], different ownership.
2543 unsafe fn into_func(self, store: &mut StoreOpaque) -> Func {
2544 self.validate_store(store);
2545 let (funcrefs, modules) = store.func_refs_and_modules();
2546 let funcref = funcrefs.push_box_host(Box::new(self), modules);
2547 Func::from_vm_func_ref(store, funcref)
2548 }
2549
2550 fn validate_store(&self, store: &mut StoreOpaque) {
2551 // This assert is required to ensure that we can indeed safely insert
2552 // `self` into the `store` provided, otherwise the type information we
2553 // have listed won't be correct. This is possible to hit with the public
2554 // API of Wasmtime, and should be documented in relevant functions.
2555 assert!(
2556 Engine::same(&self.engine, store.engine()),
2557 "cannot use a store with a different engine than a linker was created with",
2558 );
2559 }
2560
2561 pub(crate) fn sig_index(&self) -> VMSharedTypeIndex {
2562 self.func_ref().type_index
2563 }
2564
2565 pub(crate) fn func_ref(&self) -> &VMFuncRef {
2566 match &self.ctx {
2567 HostContext::Array(ctx) => unsafe { ctx.get().as_ref().func_ref() },
2568 }
2569 }
2570
2571 pub(crate) fn host_ctx(&self) -> &HostContext {
2572 &self.ctx
2573 }
2574}
2575
2576#[cfg(test)]
2577mod tests {
2578 use super::*;
2579 use crate::{Module, Store};
2580
2581 #[test]
2582 fn hash_key_is_stable_across_duplicate_store_data_entries() -> Result<()> {
2583 let mut store = Store::<()>::default();
2584 let module = Module::new(
2585 store.engine(),
2586 r#"
2587 (module
2588 (func (export "f")
2589 nop
2590 )
2591 )
2592 "#,
2593 )?;
2594 let instance = Instance::new(&mut store, &module, &[])?;
2595
2596 // Each time we `get_func`, we call `Func::from_wasmtime` which adds a
2597 // new entry to `StoreData`, so `f1` and `f2` will have different
2598 // indices into `StoreData`.
2599 let f1 = instance.get_func(&mut store, "f").unwrap();
2600 let f2 = instance.get_func(&mut store, "f").unwrap();
2601
2602 // But their hash keys are the same.
2603 assert!(
2604 f1.hash_key(&mut store.as_context_mut().0)
2605 == f2.hash_key(&mut store.as_context_mut().0)
2606 );
2607
2608 // But the hash keys are different from different funcs.
2609 let instance2 = Instance::new(&mut store, &module, &[])?;
2610 let f3 = instance2.get_func(&mut store, "f").unwrap();
2611 assert!(
2612 f1.hash_key(&mut store.as_context_mut().0)
2613 != f3.hash_key(&mut store.as_context_mut().0)
2614 );
2615
2616 Ok(())
2617 }
2618}