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use crate::trampoline::StoreInstanceHandle; use crate::{Engine, Export, Extern, Func, Global, Memory, Module, Store, Table, Trap}; use anyhow::{bail, Error, Result}; use std::any::Any; use std::mem; use wasmtime_environ::EntityIndex; use wasmtime_jit::{CompiledModule, Resolver}; use wasmtime_runtime::{ InstantiationError, StackMapRegistry, VMContext, VMExternRefActivationsTable, VMFunctionBody, }; struct SimpleResolver<'a> { imports: &'a [Extern], } impl Resolver for SimpleResolver<'_> { fn resolve(&mut self, idx: u32, _name: &str, _field: &str) -> Option<wasmtime_runtime::Export> { self.imports .get(idx as usize) .map(|i| i.get_wasmtime_export()) } } fn instantiate( store: &Store, compiled_module: &CompiledModule, imports: &[Extern], host: Box<dyn Any>, ) -> Result<StoreInstanceHandle, Error> { // For now we have a restriction that the `Store` that we're working // with is the same for everything involved here. for import in imports { if !import.comes_from_same_store(store) { bail!("cross-`Store` instantiation is not currently supported"); } } if imports.len() != compiled_module.module().imports.len() { bail!( "wrong number of imports provided, {} != {}", imports.len(), compiled_module.module().imports.len() ); } let mut resolver = SimpleResolver { imports }; let config = store.engine().config(); let instance = unsafe { let instance = compiled_module.instantiate( &mut resolver, &mut store.signatures_mut(), config.memory_creator.as_ref().map(|a| a as _), store.interrupts().clone(), host, store.externref_activations_table() as *const VMExternRefActivationsTable as *mut _, store.stack_map_registry() as *const StackMapRegistry as *mut _, )?; // After we've created the `InstanceHandle` we still need to run // initialization to set up data/elements/etc. We do this after adding // the `InstanceHandle` to the store though. This is required for safety // because the start function (for example) may trap, but element // initializers may have run which placed elements into other instance's // tables. This means that from this point on, regardless of whether // initialization is successful, we need to keep the instance alive. let instance = store.add_instance(instance); instance .initialize( config.wasm_bulk_memory, &compiled_module.data_initializers(), ) .map_err(|e| -> Error { match e { InstantiationError::Trap(trap) => Trap::from_runtime(trap).into(), other => other.into(), } })?; instance }; let start_func = instance.handle.module().start_func; // If a start function is present, invoke it. Make sure we use all the // trap-handling configuration in `store` as well. if let Some(start) = start_func { let f = match instance .handle .lookup_by_declaration(&EntityIndex::Function(start)) { wasmtime_runtime::Export::Function(f) => f, _ => unreachable!(), // valid modules shouldn't hit this }; let vmctx_ptr = instance.handle.vmctx_ptr(); unsafe { super::func::invoke_wasm_and_catch_traps(vmctx_ptr, store, || { mem::transmute::< *const VMFunctionBody, unsafe extern "C" fn(*mut VMContext, *mut VMContext), >(f.anyfunc.as_ref().func_ptr.as_ptr())( f.anyfunc.as_ref().vmctx, vmctx_ptr ) })?; } } Ok(instance) } /// An instantiated WebAssembly module. /// /// This type represents the instantiation of a [`Module`]. Once instantiated /// you can access the [`exports`](Instance::exports) which are of type /// [`Extern`] and provide the ability to call functions, set globals, read /// memory, etc. This is where all the fun stuff happens! /// /// An [`Instance`] is created from two inputs, a [`Module`] and a list of /// imports, provided as a list of [`Extern`] values. The [`Module`] is the wasm /// code that was compiled and we're instantiating, and the [`Extern`] imports /// are how we're satisfying the imports of the module provided. On successful /// instantiation an [`Instance`] will automatically invoke the wasm `start` /// function. /// /// When interacting with any wasm code you'll want to make an [`Instance`] to /// call any code or execute anything! #[derive(Clone)] pub struct Instance { pub(crate) handle: StoreInstanceHandle, store: Store, module: Module, } impl Instance { /// Creates a new [`Instance`] from the previously compiled [`Module`] and /// list of `imports` specified. /// /// This method instantiates the `module` provided with the `imports`, /// following the procedure in the [core specification][inst] to /// instantiate. Instantiation can fail for a number of reasons (many /// specified below), but if successful the `start` function will be /// automatically run (if provided) and then the [`Instance`] will be /// returned. /// /// Per the WebAssembly spec, instantiation includes running the module's /// start function, if it has one (not to be confused with the `_start` /// function, which is not run). /// /// Note that this is a low-level function that just performance an /// instantiation. See the `Linker` struct for an API which provides a /// convenient way to link imports and provides automatic Command and Reactor /// behavior. /// /// ## Providing Imports /// /// The `imports` array here is a bit tricky. The entries in the list of /// `imports` are intended to correspond 1:1 with the list of imports /// returned by [`Module::imports`]. Before calling [`Instance::new`] you'll /// want to inspect the return value of [`Module::imports`] and, for each /// import type, create an [`Extern`] which corresponds to that type. /// These [`Extern`] values are all then collected into a list and passed to /// this function. /// /// Note that this function is intentionally relatively low level. It is the /// intention that we'll soon provide a [higher level API][issue] which will /// be much more ergonomic for instantiating modules. If you need the full /// power of customization of imports, though, this is the method for you! /// /// ## Errors /// /// This function can fail for a number of reasons, including, but not /// limited to: /// /// * The number of `imports` provided doesn't match the number of imports /// returned by the `module`'s [`Module::imports`] method. /// * The type of any [`Extern`] doesn't match the corresponding /// [`ExternType`] entry that it maps to. /// * The `start` function in the instance, if present, traps. /// * Module/instance resource limits are exceeded. /// /// When instantiation fails it's recommended to inspect the return value to /// see why it failed, or bubble it upwards. If you'd like to specifically /// check for trap errors, you can use `error.downcast::<Trap>()`. /// /// [inst]: https://webassembly.github.io/spec/core/exec/modules.html#exec-instantiation /// [issue]: https://github.com/bytecodealliance/wasmtime/issues/727 /// [`ExternType`]: crate::ExternType pub fn new(store: &Store, module: &Module, imports: &[Extern]) -> Result<Instance, Error> { if !Engine::same(store.engine(), module.engine()) { bail!("cross-`Engine` instantiation is not currently supported"); } let host_info = Box::new({ let frame_info_registration = module.register_frame_info(); store.register_jit_code(module.compiled_module().jit_code_ranges()); store.register_stack_maps(&module); frame_info_registration }); let handle = instantiate(store, module.compiled_module(), imports, host_info)?; Ok(Instance { handle, store: store.clone(), module: module.clone(), }) } /// Returns the associated [`Store`] that this `Instance` is compiled into. /// /// This is the [`Store`] that generally serves as a sort of global cache /// for various instance-related things. pub fn store(&self) -> &Store { &self.store } /// Returns the list of exported items from this [`Instance`]. pub fn exports<'instance>( &'instance self, ) -> impl ExactSizeIterator<Item = Export<'instance>> + 'instance { self.handle.exports().map(move |(name, entity_index)| { let export = self.handle.lookup_by_declaration(entity_index); let extern_ = Extern::from_wasmtime_export(export, self.handle.clone()); Export::new(name, extern_) }) } /// Looks up an exported [`Extern`] value by name. /// /// This method will search the module for an export named `name` and return /// the value, if found. /// /// Returns `None` if there was no export named `name`. pub fn get_export(&self, name: &str) -> Option<Extern> { let export = self.handle.lookup(&name)?; Some(Extern::from_wasmtime_export(export, self.handle.clone())) } /// Looks up an exported [`Func`] value by name. /// /// Returns `None` if there was no export named `name`, or if there was but /// it wasn't a function. pub fn get_func(&self, name: &str) -> Option<Func> { self.get_export(name)?.into_func() } /// Looks up an exported [`Table`] value by name. /// /// Returns `None` if there was no export named `name`, or if there was but /// it wasn't a table. pub fn get_table(&self, name: &str) -> Option<Table> { self.get_export(name)?.into_table() } /// Looks up an exported [`Memory`] value by name. /// /// Returns `None` if there was no export named `name`, or if there was but /// it wasn't a memory. pub fn get_memory(&self, name: &str) -> Option<Memory> { self.get_export(name)?.into_memory() } /// Looks up an exported [`Global`] value by name. /// /// Returns `None` if there was no export named `name`, or if there was but /// it wasn't a global. pub fn get_global(&self, name: &str) -> Option<Global> { self.get_export(name)?.into_global() } }