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use super::invoke_wasm_and_catch_traps;
use crate::prelude::*;
use crate::runtime::vm::{VMFuncRef, VMOpaqueContext};
use crate::store::{AutoAssertNoGc, StoreOpaque};
use crate::{
AsContext, AsContextMut, Engine, Func, FuncType, HeapType, NoFunc, RefType, StoreContextMut,
ValRaw, ValType,
};
use core::ffi::c_void;
use core::marker;
use core::mem::{self, MaybeUninit};
use core::num::NonZeroUsize;
use core::ptr::{self};
use wasmtime_environ::VMSharedTypeIndex;
/// A statically typed WebAssembly function.
///
/// Values of this type represent statically type-checked WebAssembly functions.
/// The function within a [`TypedFunc`] is statically known to have `Params` as its
/// parameters and `Results` as its results.
///
/// This structure is created via [`Func::typed`] or [`TypedFunc::new_unchecked`].
/// For more documentation about this see those methods.
pub struct TypedFunc<Params, Results> {
_a: marker::PhantomData<fn(Params) -> Results>,
ty: FuncType,
func: Func,
}
impl<Params, Results> Clone for TypedFunc<Params, Results> {
fn clone(&self) -> TypedFunc<Params, Results> {
Self {
_a: marker::PhantomData,
ty: self.ty.clone(),
func: self.func,
}
}
}
impl<Params, Results> TypedFunc<Params, Results>
where
Params: WasmParams,
Results: WasmResults,
{
/// An unchecked version of [`Func::typed`] which does not perform a
/// typecheck and simply assumes that the type declared here matches the
/// type of this function.
///
/// The semantics of this function are the same as [`Func::typed`] except
/// that no error is returned because no typechecking is done.
///
/// # Unsafety
///
/// This function only safe to call if `typed` would otherwise return `Ok`
/// for the same `Params` and `Results` specified. If `typed` would return
/// an error then the returned `TypedFunc` is memory unsafe to invoke.
pub unsafe fn new_unchecked(store: impl AsContext, func: Func) -> TypedFunc<Params, Results> {
let store = store.as_context().0;
Self::_new_unchecked(store, func)
}
pub(crate) unsafe fn _new_unchecked(
store: &StoreOpaque,
func: Func,
) -> TypedFunc<Params, Results> {
let ty = func.load_ty(store);
TypedFunc {
_a: marker::PhantomData,
ty,
func,
}
}
/// Returns the underlying [`Func`] that this is wrapping, losing the static
/// type information in the process.
pub fn func(&self) -> &Func {
&self.func
}
/// Invokes this WebAssembly function with the specified parameters.
///
/// Returns either the results of the call, or a [`Trap`] if one happened.
///
/// For more information, see the [`Func::typed`] and [`Func::call`]
/// documentation.
///
/// # Errors
///
/// For more information on errors see the documentation on [`Func::call`].
///
/// # Panics
///
/// This function will panic if it is called when the underlying [`Func`] is
/// connected to an asynchronous store.
///
/// [`Trap`]: crate::Trap
pub fn call(&self, mut store: impl AsContextMut, params: Params) -> Result<Results> {
let mut store = store.as_context_mut();
assert!(
!store.0.async_support(),
"must use `call_async` with async stores"
);
if Self::need_gc_before_call_raw(store.0, ¶ms) {
store.0.gc();
}
let func = self.func.vm_func_ref(store.0);
unsafe { Self::call_raw(&mut store, &self.ty, func, params) }
}
/// Invokes this WebAssembly function with the specified parameters.
///
/// Returns either the results of the call, or a [`Trap`] if one happened.
///
/// For more information, see the [`Func::typed`] and [`Func::call_async`]
/// documentation.
///
/// # Errors
///
/// For more information on errors see the documentation on [`Func::call`].
///
/// # Panics
///
/// This function will panic if it is called when the underlying [`Func`] is
/// connected to a synchronous store.
///
/// [`Trap`]: crate::Trap
#[cfg(feature = "async")]
pub async fn call_async<T>(
&self,
mut store: impl AsContextMut<Data = T>,
params: Params,
) -> Result<Results>
where
T: Send,
{
let mut store = store.as_context_mut();
assert!(
store.0.async_support(),
"must use `call` with non-async stores"
);
if Self::need_gc_before_call_raw(store.0, ¶ms) {
store.0.gc_async().await;
}
store
.on_fiber(|store| {
let func = self.func.vm_func_ref(store.0);
unsafe { Self::call_raw(store, &self.ty, func, params) }
})
.await?
}
#[inline]
pub(crate) fn need_gc_before_call_raw(_store: &StoreOpaque, _params: &Params) -> bool {
#[cfg(feature = "gc")]
{
// See the comment in `Func::call_impl_check_args`.
let num_gc_refs = _params.vmgcref_pointing_to_object_count();
if let Some(num_gc_refs) = NonZeroUsize::new(num_gc_refs) {
return _store
.unwrap_gc_store()
.gc_heap
.need_gc_before_entering_wasm(num_gc_refs);
}
}
false
}
/// Do a raw call of a typed function.
///
/// # Safety
///
/// `func` must be of the given type.
///
/// If `Self::need_gc_before_call_raw`, then the caller must have done a GC
/// just before calling this method.
pub(crate) unsafe fn call_raw<T>(
store: &mut StoreContextMut<'_, T>,
ty: &FuncType,
func: ptr::NonNull<VMFuncRef>,
params: Params,
) -> Result<Results> {
// double-check that params/results match for this function's type in
// debug mode.
if cfg!(debug_assertions) {
Self::debug_typecheck(store.0, func.as_ref().type_index);
}
// Validate that all runtime values flowing into this store indeed
// belong within this store, otherwise it would be unsafe for store
// values to cross each other.
union Storage<T: Copy, U: Copy> {
params: MaybeUninit<T>,
results: U,
}
let mut storage = Storage::<Params::ValRawStorage, Results::ValRawStorage> {
params: MaybeUninit::uninit(),
};
{
let mut store = AutoAssertNoGc::new(store.0);
params.store(&mut store, ty, &mut storage.params)?;
}
// Try to capture only a single variable (a tuple) in the closure below.
// This means the size of the closure is one pointer and is much more
// efficient to move in memory. This closure is actually invoked on the
// other side of a C++ shim, so it can never be inlined enough to make
// the memory go away, so the size matters here for performance.
let mut captures = (func, storage);
let result = invoke_wasm_and_catch_traps(store, |caller| {
let (func_ref, storage) = &mut captures;
let func_ref = func_ref.as_ref();
(func_ref.array_call)(
func_ref.vmctx,
VMOpaqueContext::from_vmcontext(caller),
(storage as *mut Storage<_, _>) as *mut ValRaw,
mem::size_of_val::<Storage<_, _>>(storage) / mem::size_of::<ValRaw>(),
);
});
let (_, storage) = captures;
result?;
let mut store = AutoAssertNoGc::new(store.0);
Ok(Results::load(&mut store, &storage.results))
}
/// Purely a debug-mode assertion, not actually used in release builds.
fn debug_typecheck(store: &StoreOpaque, func: VMSharedTypeIndex) {
let ty = FuncType::from_shared_type_index(store.engine(), func);
Params::typecheck(store.engine(), ty.params(), TypeCheckPosition::Param)
.expect("params should match");
Results::typecheck(store.engine(), ty.results(), TypeCheckPosition::Result)
.expect("results should match");
}
}
#[doc(hidden)]
#[derive(Copy, Clone)]
pub enum TypeCheckPosition {
Param,
Result,
}
/// A trait implemented for types which can be arguments and results for
/// closures passed to [`Func::wrap`] as well as parameters to [`Func::typed`].
///
/// This trait should not be implemented by user types. This trait may change at
/// any time internally. The types which implement this trait, however, are
/// stable over time.
///
/// For more information see [`Func::wrap`] and [`Func::typed`]
pub unsafe trait WasmTy: Send {
// Do a "static" (aka at time of `func.typed::<P, R>()`) ahead-of-time type
// check for this type at the given position. You probably don't need to
// override this trait method.
#[doc(hidden)]
#[inline]
fn typecheck(engine: &Engine, actual: ValType, position: TypeCheckPosition) -> Result<()> {
let expected = Self::valtype();
debug_assert!(expected.comes_from_same_engine(engine));
debug_assert!(actual.comes_from_same_engine(engine));
match position {
// The caller is expecting to receive a `T` and the callee is
// actually returning a `U`, so ensure that `U <: T`.
TypeCheckPosition::Result => actual.ensure_matches(engine, &expected),
// The caller is expecting to pass a `T` and the callee is expecting
// to receive a `U`, so ensure that `T <: U`.
TypeCheckPosition::Param => match (expected.as_ref(), actual.as_ref()) {
// ... except that this technically-correct check would overly
// restrict the usefulness of our typed function APIs for the
// specific case of concrete reference types. Let's work through
// an example.
//
// Consider functions that take a `(ref param $some_func_type)`
// parameter:
//
// * We cannot have a static `wasmtime::SomeFuncTypeRef` type
// that implements `WasmTy` specifically for `(ref null
// $some_func_type)` because Wasm modules, and their types,
// are loaded dynamically at runtime.
//
// * Therefore the embedder's only option for `T <: (ref null
// $some_func_type)` is `T = (ref null nofunc)` aka
// `Option<wasmtime::NoFunc>`.
//
// * But that static type means they can *only* pass in the null
// function reference as an argument to the typed function.
// This is way too restrictive! For ergonomics, we want them
// to be able to pass in a `wasmtime::Func` whose type is
// `$some_func_type`!
//
// To lift this constraint and enable better ergonomics for
// embedders, we allow `top(T) <: top(U)` -- i.e. they are part
// of the same type hierarchy and a dynamic cast could possibly
// succeed -- for the specific case of concrete heap type
// parameters, and fall back to dynamic type checks on the
// arguments passed to each invocation, as necessary.
(Some(expected_ref), Some(actual_ref)) if actual_ref.heap_type().is_concrete() => {
expected_ref
.heap_type()
.top()
.ensure_matches(engine, &actual_ref.heap_type().top())
}
_ => expected.ensure_matches(engine, &actual),
},
}
}
// The value type that this Type represents.
#[doc(hidden)]
fn valtype() -> ValType;
#[doc(hidden)]
fn may_gc() -> bool {
match Self::valtype() {
ValType::Ref(_) => true,
ValType::I32 | ValType::I64 | ValType::F32 | ValType::F64 | ValType::V128 => false,
}
}
// Dynamic checks that this value is being used with the correct store
// context.
#[doc(hidden)]
fn compatible_with_store(&self, store: &StoreOpaque) -> bool;
// Dynamic checks that `self <: actual` for concrete type arguments. See the
// comment above in `WasmTy::typecheck`.
//
// Only ever called for concrete reference type arguments, so any type which
// is not in a type hierarchy with concrete reference types can implement
// this with `unreachable!()`.
#[doc(hidden)]
fn dynamic_concrete_type_check(
&self,
store: &StoreOpaque,
nullable: bool,
actual: &HeapType,
) -> Result<()>;
// Is this a GC-managed reference that actually points to a GC object? That
// is, `self` is *not* an `i31`, null reference, or uninhabited type.
//
// Note that it is okay if this returns false positives (i.e. `true` for
// `Rooted<AnyRef>` without actually looking up the rooted `anyref` in the
// store and reflecting on it to determine whether it is actually an
// `i31`). However, it is not okay if this returns false negatives.
#[doc(hidden)]
#[inline]
fn is_vmgcref_and_points_to_object(&self) -> bool {
Self::valtype().is_vmgcref_type_and_points_to_object()
}
// Store `self` into `ptr`.
//
// NB: We _must not_ trigger a GC when passing refs from host code into Wasm
// (e.g. returned from a host function or passed as arguments to a Wasm
// function). After insertion into the activations table, the reference is
// no longer rooted. If multiple references are being sent from the host
// into Wasm and we allowed GCs during insertion, then the following events
// could happen:
//
// * Reference A is inserted into the activations table. This does not
// trigger a GC, but does fill the table to capacity.
//
// * The caller's reference to A is removed. Now the only reference to A is
// from the activations table.
//
// * Reference B is inserted into the activations table. Because the table
// is at capacity, a GC is triggered.
//
// * A is reclaimed because the only reference keeping it alive was the
// activation table's reference (it isn't inside any Wasm frames on the
// stack yet, so stack scanning and stack maps don't increment its
// reference count).
//
// * We transfer control to Wasm, giving it A and B. Wasm uses A. That's a
// use-after-free bug.
//
// In conclusion, to prevent uses-after-free bugs, we cannot GC while
// converting types into their raw ABI forms.
#[doc(hidden)]
fn store(self, store: &mut AutoAssertNoGc<'_>, ptr: &mut MaybeUninit<ValRaw>) -> Result<()>;
// Load a version of `Self` from the `ptr` provided.
//
// # Safety
//
// This function is unsafe as it's up to the caller to ensure that `ptr` is
// valid for this given type.
#[doc(hidden)]
unsafe fn load(store: &mut AutoAssertNoGc<'_>, ptr: &ValRaw) -> Self;
}
macro_rules! integers {
($($primitive:ident/$get_primitive:ident => $ty:ident)*) => ($(
unsafe impl WasmTy for $primitive {
#[inline]
fn valtype() -> ValType {
ValType::$ty
}
#[inline]
fn compatible_with_store(&self, _: &StoreOpaque) -> bool {
true
}
#[inline]
fn dynamic_concrete_type_check(&self, _: &StoreOpaque, _: bool, _: &HeapType) -> Result<()> {
unreachable!()
}
#[inline]
fn store(self, _store: &mut AutoAssertNoGc<'_>, ptr: &mut MaybeUninit<ValRaw>) -> Result<()> {
ptr.write(ValRaw::$primitive(self));
Ok(())
}
#[inline]
unsafe fn load(_store: &mut AutoAssertNoGc<'_>, ptr: &ValRaw) -> Self {
ptr.$get_primitive()
}
}
)*)
}
integers! {
i32/get_i32 => I32
i64/get_i64 => I64
u32/get_u32 => I32
u64/get_u64 => I64
}
macro_rules! floats {
($($float:ident/$int:ident/$get_float:ident => $ty:ident)*) => ($(
unsafe impl WasmTy for $float {
#[inline]
fn valtype() -> ValType {
ValType::$ty
}
#[inline]
fn compatible_with_store(&self, _: &StoreOpaque) -> bool {
true
}
#[inline]
fn dynamic_concrete_type_check(&self, _: &StoreOpaque, _: bool, _: &HeapType) -> Result<()> {
unreachable!()
}
#[inline]
fn store(self, _store: &mut AutoAssertNoGc<'_>, ptr: &mut MaybeUninit<ValRaw>) -> Result<()> {
ptr.write(ValRaw::$float(self.to_bits()));
Ok(())
}
#[inline]
unsafe fn load(_store: &mut AutoAssertNoGc<'_>, ptr: &ValRaw) -> Self {
$float::from_bits(ptr.$get_float())
}
}
)*)
}
floats! {
f32/u32/get_f32 => F32
f64/u64/get_f64 => F64
}
unsafe impl WasmTy for NoFunc {
#[inline]
fn valtype() -> ValType {
ValType::Ref(RefType::new(false, HeapType::NoFunc))
}
#[inline]
fn compatible_with_store(&self, _store: &StoreOpaque) -> bool {
match self._inner {}
}
#[inline]
fn dynamic_concrete_type_check(&self, _: &StoreOpaque, _: bool, _: &HeapType) -> Result<()> {
match self._inner {}
}
#[inline]
fn is_vmgcref_and_points_to_object(&self) -> bool {
match self._inner {}
}
#[inline]
fn store(self, _store: &mut AutoAssertNoGc<'_>, _ptr: &mut MaybeUninit<ValRaw>) -> Result<()> {
match self._inner {}
}
#[inline]
unsafe fn load(_store: &mut AutoAssertNoGc<'_>, _ptr: &ValRaw) -> Self {
unreachable!("NoFunc is uninhabited")
}
}
unsafe impl WasmTy for Option<NoFunc> {
#[inline]
fn valtype() -> ValType {
ValType::Ref(RefType::new(true, HeapType::NoFunc))
}
#[inline]
fn compatible_with_store(&self, _store: &StoreOpaque) -> bool {
true
}
#[inline]
fn dynamic_concrete_type_check(
&self,
_: &StoreOpaque,
nullable: bool,
ty: &HeapType,
) -> Result<()> {
if nullable {
// `(ref null nofunc) <: (ref null $f)` for all function types `$f`.
Ok(())
} else {
bail!("argument type mismatch: expected non-nullable (ref {ty}), found null reference")
}
}
#[inline]
fn store(self, _store: &mut AutoAssertNoGc<'_>, ptr: &mut MaybeUninit<ValRaw>) -> Result<()> {
ptr.write(ValRaw::funcref(ptr::null_mut()));
Ok(())
}
#[inline]
unsafe fn load(_store: &mut AutoAssertNoGc<'_>, _ptr: &ValRaw) -> Self {
None
}
}
unsafe impl WasmTy for Func {
#[inline]
fn valtype() -> ValType {
ValType::Ref(RefType::new(false, HeapType::Func))
}
#[inline]
fn compatible_with_store(&self, store: &StoreOpaque) -> bool {
store.store_data().contains(self.0)
}
#[inline]
fn dynamic_concrete_type_check(
&self,
store: &StoreOpaque,
_nullable: bool,
expected: &HeapType,
) -> Result<()> {
let expected = expected.unwrap_concrete_func();
self.ensure_matches_ty(store, expected)
.context("argument type mismatch for reference to concrete type")
}
#[inline]
fn store(self, store: &mut AutoAssertNoGc<'_>, ptr: &mut MaybeUninit<ValRaw>) -> Result<()> {
let abi = self.vm_func_ref(store);
ptr.write(ValRaw::funcref(abi.cast::<c_void>().as_ptr()));
Ok(())
}
#[inline]
unsafe fn load(store: &mut AutoAssertNoGc<'_>, ptr: &ValRaw) -> Self {
let p = ptr.get_funcref();
debug_assert!(!p.is_null());
Func::from_vm_func_ref(store, p.cast()).unwrap()
}
}
unsafe impl WasmTy for Option<Func> {
#[inline]
fn valtype() -> ValType {
ValType::FUNCREF
}
#[inline]
fn compatible_with_store(&self, store: &StoreOpaque) -> bool {
if let Some(f) = self {
store.store_data().contains(f.0)
} else {
true
}
}
fn dynamic_concrete_type_check(
&self,
store: &StoreOpaque,
nullable: bool,
expected: &HeapType,
) -> Result<()> {
if let Some(f) = self {
let expected = expected.unwrap_concrete_func();
f.ensure_matches_ty(store, expected)
.context("argument type mismatch for reference to concrete type")
} else if nullable {
Ok(())
} else {
bail!("argument type mismatch: expected non-nullable (ref {expected}), found null reference")
}
}
#[inline]
fn store(self, store: &mut AutoAssertNoGc<'_>, ptr: &mut MaybeUninit<ValRaw>) -> Result<()> {
let raw = if let Some(f) = self {
f.vm_func_ref(store).as_ptr()
} else {
ptr::null_mut()
};
ptr.write(ValRaw::funcref(raw.cast::<c_void>()));
Ok(())
}
#[inline]
unsafe fn load(store: &mut AutoAssertNoGc<'_>, ptr: &ValRaw) -> Self {
Func::from_vm_func_ref(store, ptr.get_funcref().cast())
}
}
/// A trait used for [`Func::typed`] and with [`TypedFunc`] to represent the set of
/// parameters for wasm functions.
///
/// This is implemented for bare types that can be passed to wasm as well as
/// tuples of those types.
pub unsafe trait WasmParams: Send {
#[doc(hidden)]
type ValRawStorage: Copy;
#[doc(hidden)]
fn typecheck(
engine: &Engine,
params: impl ExactSizeIterator<Item = crate::ValType>,
position: TypeCheckPosition,
) -> Result<()>;
#[doc(hidden)]
fn vmgcref_pointing_to_object_count(&self) -> usize;
#[doc(hidden)]
fn store(
self,
store: &mut AutoAssertNoGc<'_>,
func_ty: &FuncType,
dst: &mut MaybeUninit<Self::ValRawStorage>,
) -> Result<()>;
}
// Forward an impl from `T` to `(T,)` for convenience if there's only one
// parameter.
unsafe impl<T> WasmParams for T
where
T: WasmTy,
{
type ValRawStorage = <(T,) as WasmParams>::ValRawStorage;
fn typecheck(
engine: &Engine,
params: impl ExactSizeIterator<Item = crate::ValType>,
position: TypeCheckPosition,
) -> Result<()> {
<(T,) as WasmParams>::typecheck(engine, params, position)
}
#[inline]
fn vmgcref_pointing_to_object_count(&self) -> usize {
T::is_vmgcref_and_points_to_object(self) as usize
}
#[inline]
fn store(
self,
store: &mut AutoAssertNoGc<'_>,
func_ty: &FuncType,
dst: &mut MaybeUninit<Self::ValRawStorage>,
) -> Result<()> {
<(T,) as WasmParams>::store((self,), store, func_ty, dst)
}
}
macro_rules! impl_wasm_params {
($n:tt $($t:ident)*) => {
#[allow(non_snake_case)]
unsafe impl<$($t: WasmTy,)*> WasmParams for ($($t,)*) {
type ValRawStorage = [ValRaw; $n];
fn typecheck(
_engine: &Engine,
mut params: impl ExactSizeIterator<Item = crate::ValType>,
_position: TypeCheckPosition,
) -> Result<()> {
let mut _n = 0;
$(
match params.next() {
Some(t) => {
_n += 1;
$t::typecheck(_engine, t, _position)?
},
None => bail!("expected {} types, found {}", $n, params.len() + _n),
}
)*
match params.next() {
None => Ok(()),
Some(_) => {
_n += 1;
bail!("expected {} types, found {}", $n, params.len() + _n)
},
}
}
#[inline]
fn vmgcref_pointing_to_object_count(&self) -> usize {
let ($(ref $t,)*) = self;
0 $(
+ $t.is_vmgcref_and_points_to_object() as usize
)*
}
#[inline]
fn store(
self,
_store: &mut AutoAssertNoGc<'_>,
_func_ty: &FuncType,
_ptr: &mut MaybeUninit<Self::ValRawStorage>,
) -> Result<()> {
let ($($t,)*) = self;
let mut _i = 0;
$(
if !$t.compatible_with_store(_store) {
bail!("attempt to pass cross-`Store` value to Wasm as function argument");
}
if $t::valtype().is_ref() {
let param_ty = _func_ty.param(_i).unwrap();
let ref_ty = param_ty.unwrap_ref();
let heap_ty = ref_ty.heap_type();
if heap_ty.is_concrete() {
$t.dynamic_concrete_type_check(_store, ref_ty.is_nullable(), heap_ty)?;
}
}
let dst = map_maybe_uninit!(_ptr[_i]);
$t.store(_store, dst)?;
_i += 1;
)*
Ok(())
}
}
};
}
for_each_function_signature!(impl_wasm_params);
/// A trait used for [`Func::typed`] and with [`TypedFunc`] to represent the set of
/// results for wasm functions.
pub unsafe trait WasmResults: WasmParams {
#[doc(hidden)]
unsafe fn load(store: &mut AutoAssertNoGc<'_>, abi: &Self::ValRawStorage) -> Self;
}
// Forwards from a bare type `T` to the 1-tuple type `(T,)`
unsafe impl<T: WasmTy> WasmResults for T {
unsafe fn load(store: &mut AutoAssertNoGc<'_>, abi: &Self::ValRawStorage) -> Self {
<(T,) as WasmResults>::load(store, abi).0
}
}
macro_rules! impl_wasm_results {
($n:tt $($t:ident)*) => {
#[allow(non_snake_case, unused_variables)]
unsafe impl<$($t: WasmTy,)*> WasmResults for ($($t,)*) {
unsafe fn load(store: &mut AutoAssertNoGc<'_>, abi: &Self::ValRawStorage) -> Self {
let [$($t,)*] = abi;
($($t::load(store, $t),)*)
}
}
};
}
for_each_function_signature!(impl_wasm_results);