wasmtime/runtime/component/func.rs
1use crate::component::instance::Instance;
2use crate::component::matching::InstanceType;
3use crate::component::storage::storage_as_slice;
4use crate::component::types::Type;
5use crate::component::values::Val;
6use crate::prelude::*;
7use crate::runtime::vm::component::{ComponentInstance, InstanceFlags, ResourceTables};
8use crate::runtime::vm::{Export, VMFuncRef};
9use crate::store::StoreOpaque;
10use crate::{AsContext, AsContextMut, StoreContextMut, ValRaw};
11use anyhow::Context as _;
12use core::mem::{self, MaybeUninit};
13use core::ptr::NonNull;
14use wasmtime_environ::component::{
15 CanonicalOptions, ExportIndex, InterfaceType, MAX_FLAT_PARAMS, MAX_FLAT_RESULTS, TypeFuncIndex,
16 TypeTuple,
17};
18
19#[cfg(feature = "component-model-async")]
20use crate::component::concurrent::{self, AsAccessor, PreparedCall};
21
22mod host;
23mod options;
24mod typed;
25pub use self::host::*;
26pub use self::options::*;
27pub use self::typed::*;
28
29/// A WebAssembly component function which can be called.
30///
31/// This type is the dual of [`wasmtime::Func`](crate::Func) for component
32/// functions. An instance of [`Func`] represents a component function from a
33/// component [`Instance`](crate::component::Instance). Like with
34/// [`wasmtime::Func`](crate::Func) it's possible to call functions either
35/// synchronously or asynchronously and either typed or untyped.
36#[derive(Copy, Clone, Debug)]
37#[repr(C)] // here for the C API.
38pub struct Func {
39 instance: Instance,
40 index: ExportIndex,
41}
42
43// Double-check that the C representation in `component/instance.h` matches our
44// in-Rust representation here in terms of size/alignment/etc.
45const _: () = {
46 #[repr(C)]
47 struct T(u64, u32);
48 #[repr(C)]
49 struct C(T, u32);
50 assert!(core::mem::size_of::<C>() == core::mem::size_of::<Func>());
51 assert!(core::mem::align_of::<C>() == core::mem::align_of::<Func>());
52 assert!(core::mem::offset_of!(Func, instance) == 0);
53};
54
55impl Func {
56 pub(crate) fn from_lifted_func(instance: Instance, index: ExportIndex) -> Func {
57 Func { instance, index }
58 }
59
60 /// Attempt to cast this [`Func`] to a statically typed [`TypedFunc`] with
61 /// the provided `Params` and `Return`.
62 ///
63 /// This function will perform a type-check at runtime that the [`Func`]
64 /// takes `Params` as parameters and returns `Return`. If the type-check
65 /// passes then a [`TypedFunc`] will be returned which can be used to
66 /// invoke the function in an efficient, statically-typed, and ergonomic
67 /// manner.
68 ///
69 /// The `Params` type parameter here is a tuple of the parameters to the
70 /// function. A function which takes no arguments should use `()`, a
71 /// function with one argument should use `(T,)`, etc. Note that all
72 /// `Params` must also implement the [`Lower`] trait since they're going
73 /// into wasm.
74 ///
75 /// The `Return` type parameter is the return value of this function. A
76 /// return value of `()` means that there's no return (similar to a Rust
77 /// unit return) and otherwise a type `T` can be specified. Note that the
78 /// `Return` must also implement the [`Lift`] trait since it's coming from
79 /// wasm.
80 ///
81 /// Types specified here must implement the [`ComponentType`] trait. This
82 /// trait is implemented for built-in types to Rust such as integer
83 /// primitives, floats, `Option<T>`, `Result<T, E>`, strings, `Vec<T>`, and
84 /// more. As parameters you'll be passing native Rust types.
85 ///
86 /// See the documentation for [`ComponentType`] for more information about
87 /// supported types.
88 ///
89 /// # Errors
90 ///
91 /// If the function does not actually take `Params` as its parameters or
92 /// return `Return` then an error will be returned.
93 ///
94 /// # Panics
95 ///
96 /// This function will panic if `self` is not owned by the `store`
97 /// specified.
98 ///
99 /// # Examples
100 ///
101 /// Calling a function which takes no parameters and has no return value:
102 ///
103 /// ```
104 /// # use wasmtime::component::Func;
105 /// # use wasmtime::Store;
106 /// # fn foo(func: &Func, store: &mut Store<()>) -> anyhow::Result<()> {
107 /// let typed = func.typed::<(), ()>(&store)?;
108 /// typed.call(store, ())?;
109 /// # Ok(())
110 /// # }
111 /// ```
112 ///
113 /// Calling a function which takes one string parameter and returns a
114 /// string:
115 ///
116 /// ```
117 /// # use wasmtime::component::Func;
118 /// # use wasmtime::Store;
119 /// # fn foo(func: &Func, mut store: Store<()>) -> anyhow::Result<()> {
120 /// let typed = func.typed::<(&str,), (String,)>(&store)?;
121 /// let ret = typed.call(&mut store, ("Hello, ",))?.0;
122 /// println!("returned string was: {}", ret);
123 /// # Ok(())
124 /// # }
125 /// ```
126 ///
127 /// Calling a function which takes multiple parameters and returns a boolean:
128 ///
129 /// ```
130 /// # use wasmtime::component::Func;
131 /// # use wasmtime::Store;
132 /// # fn foo(func: &Func, mut store: Store<()>) -> anyhow::Result<()> {
133 /// let typed = func.typed::<(u32, Option<&str>, &[u8]), (bool,)>(&store)?;
134 /// let ok: bool = typed.call(&mut store, (1, Some("hello"), b"bytes!"))?.0;
135 /// println!("return value was: {ok}");
136 /// # Ok(())
137 /// # }
138 /// ```
139 pub fn typed<Params, Return>(&self, store: impl AsContext) -> Result<TypedFunc<Params, Return>>
140 where
141 Params: ComponentNamedList + Lower,
142 Return: ComponentNamedList + Lift,
143 {
144 self._typed(store.as_context().0, None)
145 }
146
147 pub(crate) fn _typed<Params, Return>(
148 &self,
149 store: &StoreOpaque,
150 instance: Option<&ComponentInstance>,
151 ) -> Result<TypedFunc<Params, Return>>
152 where
153 Params: ComponentNamedList + Lower,
154 Return: ComponentNamedList + Lift,
155 {
156 self.typecheck::<Params, Return>(store, instance)?;
157 unsafe { Ok(TypedFunc::new_unchecked(*self)) }
158 }
159
160 fn typecheck<Params, Return>(
161 &self,
162 store: &StoreOpaque,
163 instance: Option<&ComponentInstance>,
164 ) -> Result<()>
165 where
166 Params: ComponentNamedList + Lower,
167 Return: ComponentNamedList + Lift,
168 {
169 let cx = InstanceType::new(instance.unwrap_or_else(|| self.instance.id().get(store)));
170 let ty = &cx.types[self.ty(store)];
171
172 Params::typecheck(&InterfaceType::Tuple(ty.params), &cx)
173 .context("type mismatch with parameters")?;
174 Return::typecheck(&InterfaceType::Tuple(ty.results), &cx)
175 .context("type mismatch with results")?;
176
177 Ok(())
178 }
179
180 /// Get the parameter names and types for this function.
181 pub fn params(&self, store: impl AsContext) -> Box<[(String, Type)]> {
182 let store = store.as_context();
183 let instance = self.instance.id().get(store.0);
184 let types = instance.component().types();
185 let func_ty = &types[self.ty(store.0)];
186 types[func_ty.params]
187 .types
188 .iter()
189 .zip(&func_ty.param_names)
190 .map(|(ty, name)| (name.clone(), Type::from(ty, &InstanceType::new(instance))))
191 .collect()
192 }
193
194 /// Get the result types for this function.
195 pub fn results(&self, store: impl AsContext) -> Box<[Type]> {
196 let store = store.as_context();
197 let instance = self.instance.id().get(store.0);
198 let types = instance.component().types();
199 let ty = self.ty(store.0);
200 types[types[ty].results]
201 .types
202 .iter()
203 .map(|ty| Type::from(ty, &InstanceType::new(instance)))
204 .collect()
205 }
206
207 fn ty(&self, store: &StoreOpaque) -> TypeFuncIndex {
208 let instance = self.instance.id().get(store);
209 let (ty, _, _) = instance.component().export_lifted_function(self.index);
210 ty
211 }
212
213 /// Invokes this function with the `params` given and returns the result.
214 ///
215 /// The `params` provided must match the parameters that this function takes
216 /// in terms of their types and the number of parameters. Results will be
217 /// written to the `results` slice provided if the call completes
218 /// successfully. The initial types of the values in `results` are ignored
219 /// and values are overwritten to write the result. It's required that the
220 /// size of `results` exactly matches the number of results that this
221 /// function produces.
222 ///
223 /// Note that after a function is invoked the embedder needs to invoke
224 /// [`Func::post_return`] to execute any final cleanup required by the
225 /// guest. This function call is required to either call the function again
226 /// or to call another function.
227 ///
228 /// For more detailed information see the documentation of
229 /// [`TypedFunc::call`].
230 ///
231 /// # Errors
232 ///
233 /// Returns an error in situations including but not limited to:
234 ///
235 /// * `params` is not the right size or if the values have the wrong type
236 /// * `results` is not the right size
237 /// * A trap occurs while executing the function
238 /// * The function calls a host function which returns an error
239 ///
240 /// See [`TypedFunc::call`] for more information in addition to
241 /// [`wasmtime::Func::call`](crate::Func::call).
242 ///
243 /// # Panics
244 ///
245 /// Panics if this is called on a function in an asynchronous store. This
246 /// only works with functions defined within a synchronous store. Also
247 /// panics if `store` does not own this function.
248 pub fn call(
249 &self,
250 mut store: impl AsContextMut,
251 params: &[Val],
252 results: &mut [Val],
253 ) -> Result<()> {
254 let mut store = store.as_context_mut();
255 assert!(
256 !store.0.async_support(),
257 "must use `call_async` when async support is enabled on the config"
258 );
259 self.call_impl(&mut store.as_context_mut(), params, results)
260 }
261
262 /// Exactly like [`Self::call`] except for use on async stores.
263 ///
264 /// Note that after this [`Func::post_return_async`] will be used instead of
265 /// the synchronous version at [`Func::post_return`].
266 ///
267 /// # Panics
268 ///
269 /// Panics if this is called on a function in a synchronous store. This
270 /// only works with functions defined within an asynchronous store. Also
271 /// panics if `store` does not own this function.
272 #[cfg(feature = "async")]
273 pub async fn call_async(
274 &self,
275 mut store: impl AsContextMut<Data: Send>,
276 params: &[Val],
277 results: &mut [Val],
278 ) -> Result<()> {
279 let store = store.as_context_mut();
280
281 #[cfg(feature = "component-model-async")]
282 {
283 store
284 .run_concurrent_trap_on_idle(async |store| {
285 self.call_concurrent_dynamic(store, params, results, false)
286 .await
287 .map(drop)
288 })
289 .await?
290 }
291 #[cfg(not(feature = "component-model-async"))]
292 {
293 assert!(
294 store.0.async_support(),
295 "cannot use `call_async` without enabling async support in the config"
296 );
297 let mut store = store;
298 store
299 .on_fiber(|store| self.call_impl(store, params, results))
300 .await?
301 }
302 }
303
304 fn check_params_results<T>(
305 &self,
306 store: StoreContextMut<T>,
307 params: &[Val],
308 results: &mut [Val],
309 ) -> Result<()> {
310 let param_tys = self.params(&store);
311 if param_tys.len() != params.len() {
312 bail!(
313 "expected {} argument(s), got {}",
314 param_tys.len(),
315 params.len(),
316 );
317 }
318
319 let result_tys = self.results(&store);
320
321 if result_tys.len() != results.len() {
322 bail!(
323 "expected {} result(s), got {}",
324 result_tys.len(),
325 results.len(),
326 );
327 }
328
329 Ok(())
330 }
331
332 /// Start a concurrent call to this function.
333 ///
334 /// Unlike [`Self::call`] and [`Self::call_async`] (both of which require
335 /// exclusive access to the store until the completion of the call), calls
336 /// made using this method may run concurrently with other calls to the same
337 /// instance. In addition, the runtime will call the `post-return` function
338 /// (if any) automatically when the guest task completes -- no need to
339 /// explicitly call `Func::post_return` afterward.
340 ///
341 /// This returns a [`TaskExit`] representing the completion of the guest
342 /// task and any transitive subtasks it might create.
343 ///
344 /// # Panics
345 ///
346 /// Panics if the store that the [`Accessor`] is derived from does not own
347 /// this function.
348 #[cfg(feature = "component-model-async")]
349 pub async fn call_concurrent(
350 self,
351 accessor: impl AsAccessor<Data: Send>,
352 params: &[Val],
353 results: &mut [Val],
354 ) -> Result<TaskExit> {
355 self.call_concurrent_dynamic(accessor, params, results, true)
356 .await
357 }
358
359 /// Internal helper function for `call_async` and `call_concurrent`.
360 #[cfg(feature = "component-model-async")]
361 async fn call_concurrent_dynamic(
362 self,
363 accessor: impl AsAccessor<Data: Send>,
364 params: &[Val],
365 results: &mut [Val],
366 call_post_return_automatically: bool,
367 ) -> Result<TaskExit> {
368 let result = accessor.as_accessor().with(|mut store| {
369 assert!(
370 store.as_context_mut().0.async_support(),
371 "cannot use `call_concurrent` when async support is not enabled on the config"
372 );
373 self.check_params_results(store.as_context_mut(), params, results)?;
374 let prepared = self.prepare_call_dynamic(
375 store.as_context_mut(),
376 params.to_vec(),
377 call_post_return_automatically,
378 )?;
379 concurrent::queue_call(store.as_context_mut(), prepared)
380 })?;
381
382 let (run_results, rx) = result.await?;
383 assert_eq!(run_results.len(), results.len());
384 for (result, slot) in run_results.into_iter().zip(results) {
385 *slot = result;
386 }
387 Ok(TaskExit(rx))
388 }
389
390 /// Calls `concurrent::prepare_call` with monomorphized functions for
391 /// lowering the parameters and lifting the result.
392 #[cfg(feature = "component-model-async")]
393 fn prepare_call_dynamic<'a, T: Send + 'static>(
394 self,
395 mut store: StoreContextMut<'a, T>,
396 params: Vec<Val>,
397 call_post_return_automatically: bool,
398 ) -> Result<PreparedCall<Vec<Val>>> {
399 let store = store.as_context_mut();
400
401 concurrent::prepare_call(
402 store,
403 self,
404 MAX_FLAT_PARAMS,
405 true,
406 call_post_return_automatically,
407 move |func, store, params_out| {
408 func.with_lower_context(store, call_post_return_automatically, |cx, ty| {
409 Self::lower_args(cx, ¶ms, ty, params_out)
410 })
411 },
412 move |func, store, results| {
413 let max_flat = if func.abi_async(store) {
414 MAX_FLAT_PARAMS
415 } else {
416 MAX_FLAT_RESULTS
417 };
418 let results = func.with_lift_context(store, |cx, ty| {
419 Self::lift_results(cx, ty, results, max_flat)?.collect::<Result<Vec<_>>>()
420 })?;
421 Ok(Box::new(results))
422 },
423 )
424 }
425
426 fn call_impl(
427 &self,
428 mut store: impl AsContextMut,
429 params: &[Val],
430 results: &mut [Val],
431 ) -> Result<()> {
432 let mut store = store.as_context_mut();
433
434 self.check_params_results(store.as_context_mut(), params, results)?;
435
436 if self.abi_async(store.0) {
437 unreachable!(
438 "async-lifted exports should have failed validation \
439 when `component-model-async` feature disabled"
440 );
441 }
442
443 // SAFETY: the chosen representations of type parameters to `call_raw`
444 // here should be generally safe to work with:
445 //
446 // * parameters use `MaybeUninit<[MaybeUninit<ValRaw>; MAX_FLAT_PARAMS]>`
447 // which represents the maximal possible number of parameters that can
448 // be passed to lifted component functions. This is modeled with
449 // `MaybeUninit` to represent how it all starts as uninitialized and
450 // thus can't be safely read during lowering.
451 //
452 // * results are modeled as `[ValRaw; MAX_FLAT_RESULTS]` which
453 // represents the maximal size of values that can be returned. Note
454 // that if the function doesn't actually have a return value then the
455 // `ValRaw` inside the array will have undefined contents. That is
456 // safe in Rust, however, due to `ValRaw` being a `union`. The
457 // contents should dynamically not be read due to the type of the
458 // function used here matching the actual lift.
459 unsafe {
460 self.call_raw(
461 store,
462 |cx, ty, dst: &mut MaybeUninit<[MaybeUninit<ValRaw>; MAX_FLAT_PARAMS]>| {
463 // SAFETY: it's safe to assume that
464 // `MaybeUninit<array-of-maybe-uninit>` is initialized because
465 // each individual element is still considered uninitialized.
466 let dst: &mut [MaybeUninit<ValRaw>] = dst.assume_init_mut();
467 Self::lower_args(cx, params, ty, dst)
468 },
469 |cx, results_ty, src: &[ValRaw; MAX_FLAT_RESULTS]| {
470 let max_flat = MAX_FLAT_RESULTS;
471 for (result, slot) in
472 Self::lift_results(cx, results_ty, src, max_flat)?.zip(results)
473 {
474 *slot = result?;
475 }
476 Ok(())
477 },
478 )
479 }
480 }
481
482 pub(crate) fn lifted_core_func(&self, store: &mut StoreOpaque) -> NonNull<VMFuncRef> {
483 let def = {
484 let instance = self.instance.id().get(store);
485 let (_ty, def, _options) = instance.component().export_lifted_function(self.index);
486 def.clone()
487 };
488 match self.instance.lookup_vmdef(store, &def) {
489 Export::Function(f) => f.vm_func_ref(store),
490 _ => unreachable!(),
491 }
492 }
493
494 pub(crate) fn post_return_core_func(&self, store: &StoreOpaque) -> Option<NonNull<VMFuncRef>> {
495 let instance = self.instance.id().get(store);
496 let component = instance.component();
497 let (_ty, _def, options) = component.export_lifted_function(self.index);
498 let post_return = component.env_component().options[options].post_return;
499 post_return.map(|i| instance.runtime_post_return(i))
500 }
501
502 pub(crate) fn abi_async(&self, store: &StoreOpaque) -> bool {
503 let instance = self.instance.id().get(store);
504 let component = instance.component();
505 let (_ty, _def, options) = component.export_lifted_function(self.index);
506 component.env_component().options[options].async_
507 }
508
509 pub(crate) fn abi_info<'a>(
510 &self,
511 store: &'a StoreOpaque,
512 ) -> (Options, InstanceFlags, TypeFuncIndex, &'a CanonicalOptions) {
513 let vminstance = self.instance.id().get(store);
514 let component = vminstance.component();
515 let (ty, _def, options_index) = component.export_lifted_function(self.index);
516 let raw_options = &component.env_component().options[options_index];
517 let options = Options::new_index(store, self.instance, options_index);
518 (
519 options,
520 vminstance.instance_flags(raw_options.instance),
521 ty,
522 raw_options,
523 )
524 }
525
526 /// Invokes the underlying wasm function, lowering arguments and lifting the
527 /// result.
528 ///
529 /// The `lower` function and `lift` function provided here are what actually
530 /// do the lowering and lifting. The `LowerParams` and `LowerReturn` types
531 /// are what will be allocated on the stack for this function call. They
532 /// should be appropriately sized for the lowering/lifting operation
533 /// happening.
534 ///
535 /// # Safety
536 ///
537 /// The safety of this function relies on the correct definitions of the
538 /// `LowerParams` and `LowerReturn` type. They must match the type of `self`
539 /// for the params/results that are going to be produced. Additionally
540 /// these types must be representable with a sequence of `ValRaw` values.
541 unsafe fn call_raw<T, Return, LowerParams, LowerReturn>(
542 &self,
543 mut store: StoreContextMut<'_, T>,
544 lower: impl FnOnce(
545 &mut LowerContext<'_, T>,
546 InterfaceType,
547 &mut MaybeUninit<LowerParams>,
548 ) -> Result<()>,
549 lift: impl FnOnce(&mut LiftContext<'_>, InterfaceType, &LowerReturn) -> Result<Return>,
550 ) -> Result<Return>
551 where
552 LowerParams: Copy,
553 LowerReturn: Copy,
554 {
555 let export = self.lifted_core_func(store.0);
556
557 #[repr(C)]
558 union Union<Params: Copy, Return: Copy> {
559 params: Params,
560 ret: Return,
561 }
562
563 let space = &mut MaybeUninit::<Union<LowerParams, LowerReturn>>::uninit();
564
565 // Double-check the size/alignment of `space`, just in case.
566 //
567 // Note that this alone is not enough to guarantee the validity of the
568 // `unsafe` block below, but it's definitely required. In any case LLVM
569 // should be able to trivially see through these assertions and remove
570 // them in release mode.
571 let val_size = mem::size_of::<ValRaw>();
572 let val_align = mem::align_of::<ValRaw>();
573 assert!(mem::size_of_val(space) % val_size == 0);
574 assert!(mem::size_of_val(map_maybe_uninit!(space.params)) % val_size == 0);
575 assert!(mem::size_of_val(map_maybe_uninit!(space.ret)) % val_size == 0);
576 assert!(mem::align_of_val(space) == val_align);
577 assert!(mem::align_of_val(map_maybe_uninit!(space.params)) == val_align);
578 assert!(mem::align_of_val(map_maybe_uninit!(space.ret)) == val_align);
579
580 self.with_lower_context(store.as_context_mut(), false, |cx, ty| {
581 cx.enter_call();
582 lower(cx, ty, map_maybe_uninit!(space.params))
583 })?;
584
585 // SAFETY: We are providing the guarantee that all the inputs are valid.
586 // The various pointers passed in for the function are all valid since
587 // they're coming from our store, and the `params_and_results` should
588 // have the correct layout for the core wasm function we're calling.
589 // Note that this latter point relies on the correctness of this module
590 // and `ComponentType` implementations, hence `ComponentType` being an
591 // `unsafe` trait.
592 unsafe {
593 crate::Func::call_unchecked_raw(
594 &mut store,
595 export,
596 NonNull::new(core::ptr::slice_from_raw_parts_mut(
597 space.as_mut_ptr().cast(),
598 mem::size_of_val(space) / mem::size_of::<ValRaw>(),
599 ))
600 .unwrap(),
601 )?;
602 }
603
604 // SAFETY: We're relying on the correctness of the structure of
605 // `LowerReturn` and the type-checking performed to acquire the
606 // `TypedFunc` to make this safe. It should be the case that
607 // `LowerReturn` is the exact representation of the return value when
608 // interpreted as `[ValRaw]`, and additionally they should have the
609 // correct types for the function we just called (which filled in the
610 // return values).
611 let ret: &LowerReturn = unsafe { map_maybe_uninit!(space.ret).assume_init_ref() };
612
613 // Lift the result into the host while managing post-return state
614 // here as well.
615 //
616 // After a successful lift the return value of the function, which
617 // is currently required to be 0 or 1 values according to the
618 // canonical ABI, is saved within the `Store`'s `FuncData`. This'll
619 // later get used in post-return.
620 // flags.set_needs_post_return(true);
621 let val = self.with_lift_context(store.0, |cx, ty| lift(cx, ty, ret))?;
622
623 // SAFETY: it's a contract of this function that `LowerReturn` is an
624 // appropriate representation of the result of this function.
625 let ret_slice = unsafe { storage_as_slice(ret) };
626
627 self.instance.id().get_mut(store.0).post_return_arg_set(
628 self.index,
629 match ret_slice.len() {
630 0 => ValRaw::i32(0),
631 1 => ret_slice[0],
632 _ => unreachable!(),
633 },
634 );
635 return Ok(val);
636 }
637
638 /// Invokes the `post-return` canonical ABI option, if specified, after a
639 /// [`Func::call`] has finished.
640 ///
641 /// This function is a required method call after a [`Func::call`] completes
642 /// successfully. After the embedder has finished processing the return
643 /// value then this function must be invoked.
644 ///
645 /// # Errors
646 ///
647 /// This function will return an error in the case of a WebAssembly trap
648 /// happening during the execution of the `post-return` function, if
649 /// specified.
650 ///
651 /// # Panics
652 ///
653 /// This function will panic if it's not called under the correct
654 /// conditions. This can only be called after a previous invocation of
655 /// [`Func::call`] completes successfully, and this function can only
656 /// be called for the same [`Func`] that was `call`'d.
657 ///
658 /// If this function is called when [`Func::call`] was not previously
659 /// called, then it will panic. If a different [`Func`] for the same
660 /// component instance was invoked then this function will also panic
661 /// because the `post-return` needs to happen for the other function.
662 ///
663 /// Panics if this is called on a function in an asynchronous store.
664 /// This only works with functions defined within a synchronous store.
665 #[inline]
666 pub fn post_return(&self, mut store: impl AsContextMut) -> Result<()> {
667 let store = store.as_context_mut();
668 assert!(
669 !store.0.async_support(),
670 "must use `post_return_async` when async support is enabled on the config"
671 );
672 self.post_return_impl(store)
673 }
674
675 /// Exactly like [`Self::post_return`] except for use on async stores.
676 ///
677 /// # Panics
678 ///
679 /// Panics if this is called on a function in a synchronous store. This
680 /// only works with functions defined within an asynchronous store.
681 #[cfg(feature = "async")]
682 pub async fn post_return_async(&self, mut store: impl AsContextMut<Data: Send>) -> Result<()> {
683 let mut store = store.as_context_mut();
684 assert!(
685 store.0.async_support(),
686 "cannot use `post_return_async` without enabling async support in the config"
687 );
688 // Future optimization opportunity: conditionally use a fiber here since
689 // some func's post_return will not need the async context (i.e. end up
690 // calling async host functionality)
691 store.on_fiber(|store| self.post_return_impl(store)).await?
692 }
693
694 fn post_return_impl(&self, mut store: impl AsContextMut) -> Result<()> {
695 let mut store = store.as_context_mut();
696
697 let index = self.index;
698 let vminstance = self.instance.id().get(store.0);
699 let component = vminstance.component();
700 let (_ty, _def, options) = component.export_lifted_function(index);
701 let post_return = self.post_return_core_func(store.0);
702 let mut flags =
703 vminstance.instance_flags(component.env_component().options[options].instance);
704 let mut instance = self.instance.id().get_mut(store.0);
705 let post_return_arg = instance.as_mut().post_return_arg_take(index);
706
707 unsafe {
708 // First assert that the instance is in a "needs post return" state.
709 // This will ensure that the previous action on the instance was a
710 // function call above. This flag is only set after a component
711 // function returns so this also can't be called (as expected)
712 // during a host import for example.
713 //
714 // Note, though, that this assert is not sufficient because it just
715 // means some function on this instance needs its post-return
716 // called. We need a precise post-return for a particular function
717 // which is the second assert here (the `.expect`). That will assert
718 // that this function itself needs to have its post-return called.
719 //
720 // The theory at least is that these two asserts ensure component
721 // model semantics are upheld where the host properly calls
722 // `post_return` on the right function despite the call being a
723 // separate step in the API.
724 assert!(
725 flags.needs_post_return(),
726 "post_return can only be called after a function has previously been called",
727 );
728 let post_return_arg = post_return_arg.expect("calling post_return on wrong function");
729
730 // This is a sanity-check assert which shouldn't ever trip.
731 assert!(!flags.may_enter());
732
733 // Unset the "needs post return" flag now that post-return is being
734 // processed. This will cause future invocations of this method to
735 // panic, even if the function call below traps.
736 flags.set_needs_post_return(false);
737
738 // Post return functions are forbidden from calling imports or
739 // intrinsics.
740 flags.set_may_leave(false);
741
742 // If the function actually had a `post-return` configured in its
743 // canonical options that's executed here.
744 //
745 // Note that if this traps (returns an error) this function
746 // intentionally leaves the instance in a "poisoned" state where it
747 // can no longer be entered because `may_enter` is `false`.
748 if let Some(func) = post_return {
749 crate::Func::call_unchecked_raw(
750 &mut store,
751 func,
752 NonNull::new(core::ptr::slice_from_raw_parts(&post_return_arg, 1).cast_mut())
753 .unwrap(),
754 )?;
755 }
756
757 // And finally if everything completed successfully then the "may
758 // enter" and "may leave" flags are set to `true` again here which
759 // enables further use of the component.
760 flags.set_may_enter(true);
761 flags.set_may_leave(true);
762
763 let (calls, host_table, _, instance) = store
764 .0
765 .component_resource_state_with_instance(self.instance);
766 ResourceTables {
767 host_table: Some(host_table),
768 calls,
769 guest: Some(instance.guest_tables()),
770 }
771 .exit_call()?;
772 }
773 Ok(())
774 }
775
776 fn lower_args<T>(
777 cx: &mut LowerContext<'_, T>,
778 params: &[Val],
779 params_ty: InterfaceType,
780 dst: &mut [MaybeUninit<ValRaw>],
781 ) -> Result<()> {
782 let params_ty = match params_ty {
783 InterfaceType::Tuple(i) => &cx.types[i],
784 _ => unreachable!(),
785 };
786 if params_ty.abi.flat_count(MAX_FLAT_PARAMS).is_some() {
787 let dst = &mut dst.iter_mut();
788
789 params
790 .iter()
791 .zip(params_ty.types.iter())
792 .try_for_each(|(param, ty)| param.lower(cx, *ty, dst))
793 } else {
794 Self::store_args(cx, ¶ms_ty, params, dst)
795 }
796 }
797
798 fn store_args<T>(
799 cx: &mut LowerContext<'_, T>,
800 params_ty: &TypeTuple,
801 args: &[Val],
802 dst: &mut [MaybeUninit<ValRaw>],
803 ) -> Result<()> {
804 let size = usize::try_from(params_ty.abi.size32).unwrap();
805 let ptr = cx.realloc(0, 0, params_ty.abi.align32, size)?;
806 let mut offset = ptr;
807 for (ty, arg) in params_ty.types.iter().zip(args) {
808 let abi = cx.types.canonical_abi(ty);
809 arg.store(cx, *ty, abi.next_field32_size(&mut offset))?;
810 }
811
812 dst[0].write(ValRaw::i64(ptr as i64));
813
814 Ok(())
815 }
816
817 fn lift_results<'a, 'b>(
818 cx: &'a mut LiftContext<'b>,
819 results_ty: InterfaceType,
820 src: &'a [ValRaw],
821 max_flat: usize,
822 ) -> Result<Box<dyn Iterator<Item = Result<Val>> + 'a>> {
823 let results_ty = match results_ty {
824 InterfaceType::Tuple(i) => &cx.types[i],
825 _ => unreachable!(),
826 };
827 if results_ty.abi.flat_count(max_flat).is_some() {
828 let mut flat = src.iter();
829 Ok(Box::new(
830 results_ty
831 .types
832 .iter()
833 .map(move |ty| Val::lift(cx, *ty, &mut flat)),
834 ))
835 } else {
836 let iter = Self::load_results(cx, results_ty, &mut src.iter())?;
837 Ok(Box::new(iter))
838 }
839 }
840
841 fn load_results<'a, 'b>(
842 cx: &'a mut LiftContext<'b>,
843 results_ty: &'a TypeTuple,
844 src: &mut core::slice::Iter<'_, ValRaw>,
845 ) -> Result<impl Iterator<Item = Result<Val>> + use<'a, 'b>> {
846 // FIXME(#4311): needs to read an i64 for memory64
847 let ptr = usize::try_from(src.next().unwrap().get_u32())?;
848 if ptr % usize::try_from(results_ty.abi.align32)? != 0 {
849 bail!("return pointer not aligned");
850 }
851
852 let bytes = cx
853 .memory()
854 .get(ptr..)
855 .and_then(|b| b.get(..usize::try_from(results_ty.abi.size32).unwrap()))
856 .ok_or_else(|| anyhow::anyhow!("pointer out of bounds of memory"))?;
857
858 let mut offset = 0;
859 Ok(results_ty.types.iter().map(move |ty| {
860 let abi = cx.types.canonical_abi(ty);
861 let offset = abi.next_field32_size(&mut offset);
862 Val::load(cx, *ty, &bytes[offset..][..abi.size32 as usize])
863 }))
864 }
865
866 #[cfg(feature = "component-model-async")]
867 pub(crate) fn instance(self) -> Instance {
868 self.instance
869 }
870
871 #[cfg(feature = "component-model-async")]
872 pub(crate) fn index(self) -> ExportIndex {
873 self.index
874 }
875
876 /// Creates a `LowerContext` using the configuration values of this lifted
877 /// function.
878 ///
879 /// The `lower` closure provided should perform the actual lowering and
880 /// return the result of the lowering operation which is then returned from
881 /// this function as well.
882 fn with_lower_context<T>(
883 self,
884 mut store: StoreContextMut<T>,
885 may_enter: bool,
886 lower: impl FnOnce(&mut LowerContext<T>, InterfaceType) -> Result<()>,
887 ) -> Result<()> {
888 let types = self.instance.id().get(store.0).component().types().clone();
889 let (options, mut flags, ty, _) = self.abi_info(store.0);
890
891 // Test the "may enter" flag which is a "lock" on this instance.
892 // This is immediately set to `false` afterwards and note that
893 // there's no on-cleanup setting this flag back to true. That's an
894 // intentional design aspect where if anything goes wrong internally
895 // from this point on the instance is considered "poisoned" and can
896 // never be entered again. The only time this flag is set to `true`
897 // again is after post-return logic has completed successfully.
898 unsafe {
899 if !flags.may_enter() {
900 bail!(crate::Trap::CannotEnterComponent);
901 }
902 flags.set_may_enter(false);
903 }
904
905 // Perform the actual lowering, where while this is running the
906 // component is forbidden from calling imports.
907 unsafe {
908 debug_assert!(flags.may_leave());
909 flags.set_may_leave(false);
910 }
911 let mut cx = LowerContext::new(store.as_context_mut(), &options, &types, self.instance);
912 let result = lower(&mut cx, InterfaceType::Tuple(types[ty].params));
913 unsafe { flags.set_may_leave(true) };
914 result?;
915
916 // If this is an async function and `may_enter == true` then we're
917 // allowed to reenter the component at this point, and otherwise flag a
918 // post-return call being required as we're about to enter wasm and
919 // afterwards need a post-return.
920 unsafe {
921 if may_enter && options.async_() {
922 flags.set_may_enter(true);
923 } else {
924 flags.set_needs_post_return(true);
925 }
926 }
927
928 Ok(())
929 }
930
931 /// Creates a `LiftContext` using the configuration values with this lifted
932 /// function.
933 ///
934 /// The closure `lift` provided should actually perform the lift itself and
935 /// the result of that closure is returned from this function call as well.
936 fn with_lift_context<R>(
937 self,
938 store: &mut StoreOpaque,
939 lift: impl FnOnce(&mut LiftContext, InterfaceType) -> Result<R>,
940 ) -> Result<R> {
941 let (options, _flags, ty, _) = self.abi_info(store);
942 let mut cx = LiftContext::new(store, &options, self.instance);
943 let ty = InterfaceType::Tuple(cx.types[ty].results);
944 lift(&mut cx, ty)
945 }
946}
947
948/// Represents the completion of a task created using
949/// `[Typed]Func::call_concurrent`.
950///
951/// In general, a guest task may continue running after returning a value.
952/// Moreover, any given guest task may create its own subtasks before or after
953/// returning and may exit before some or all of those subtasks have finished
954/// running. In that case, the still-running subtasks will be "reparented" to
955/// the nearest surviving caller, which may be the original host call. The
956/// future returned by `TaskExit::block` will resolve once all transitive
957/// subtasks created directly or indirectly by the original call to
958/// `Instance::call_concurrent` have exited.
959#[cfg(feature = "component-model-async")]
960pub struct TaskExit(futures::channel::oneshot::Receiver<()>);
961
962#[cfg(feature = "component-model-async")]
963impl TaskExit {
964 /// Returns a future which will resolve once all transitive subtasks created
965 /// directly or indirectly by the original call to
966 /// `Instance::call_concurrent` have exited.
967 pub async fn block(self, accessor: impl AsAccessor<Data: Send>) {
968 // The current implementation makes no use of `accessor`, but future
969 // implementations might (e.g. by using a more efficient mechanism than
970 // a oneshot channel).
971 _ = accessor;
972
973 // We don't care whether the sender sent us a value or was dropped
974 // first; either one counts as a notification, so we ignore the result
975 // once the future resolves:
976 _ = self.0.await;
977 }
978}