wasmer/lib/runtime/src/instance.rs

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use crate::recovery::call_protected;
use crate::{
backing::{ImportBacking, LocalBacking},
memory::LinearMemory,
module::{Export, Module},
table::TableBacking,
types::{FuncIndex, FuncSig, Memory, Table, Type, Value},
vm,
};
use hashbrown::HashMap;
use libffi::high::{arg as libffi_arg, call as libffi_call, CodePtr};
use std::iter;
use std::sync::Arc;
pub struct Instance {
pub(crate) backing: LocalBacking,
import_backing: ImportBacking,
pub module: Module,
}
impl Instance {
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pub(crate) fn new(
module: Module,
imports: &dyn ImportResolver,
) -> Result<Box<Instance>, String> {
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let import_backing = ImportBacking::new(&module, imports)?;
let backing = LocalBacking::new(&module, &import_backing);
let start_func = module.start_func;
let mut instance = Box::new(Instance {
backing,
import_backing,
module,
});
if let Some(start_index) = start_func {
instance.call_with_index(start_index, &[])?;
}
Ok(instance)
}
/// Call an exported webassembly function given the export name.
/// Pass arguments by wrapping each one in the `Value` enum.
/// The returned value is also returned in a `Value`.
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///
/// This will eventually return `Result<Option<Vec<Value>>, String>` in
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/// order to support multi-value returns.
pub fn call(&mut self, name: &str, args: &[Value]) -> Result<Option<Value>, String> {
let func_index = *self
.module
.exports
.get(name)
.ok_or_else(|| "there is no export with that name".to_string())
.and_then(|export| match export {
Export::Func(func_index) => Ok(func_index),
_ => Err("that export is not a function".to_string()),
})?;
self.call_with_index(func_index, args)
}
fn call_with_index(
&mut self,
func_index: FuncIndex,
args: &[Value],
) -> Result<Option<Value>, String> {
// Check the function signature.
let sig_index = *self
.module
.func_assoc
.get(func_index)
.expect("broken invariant, incorrect func index");
{
let signature = self.module.sig_registry.lookup_func_sig(sig_index);
assert!(
signature.returns.len() <= 1,
"multi-value returns not yet supported"
);
if !signature.check_sig(args) {
return Err("incorrect signature".to_string());
}
}
// the vmctx will be located at the same place on the stack the entire time that this
// wasm function is running.
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let mut vmctx = vm::Ctx::new(&mut self.backing, &mut self.import_backing);
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let vmctx_ptr = &mut vmctx as *mut vm::Ctx;
let libffi_args: Vec<_> = args
.iter()
.map(|val| match val {
Value::I32(ref x) => libffi_arg(x),
Value::I64(ref x) => libffi_arg(x),
Value::F32(ref x) => libffi_arg(x),
Value::F64(ref x) => libffi_arg(x),
})
.chain(iter::once(libffi_arg(&vmctx_ptr)))
.collect();
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let func_ptr = CodePtr::from_ptr(
self.module
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.func_resolver
.get(&self.module, func_index)
.expect("broken invariant, func resolver not synced with module.exports")
.cast()
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.as_ptr(),
);
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call_protected(|| {
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self.module
.sig_registry
.lookup_func_sig(sig_index)
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.returns
.first()
.map(|ty| match ty {
Type::I32 => Value::I32(unsafe { libffi_call(func_ptr, &libffi_args) }),
Type::I64 => Value::I64(unsafe { libffi_call(func_ptr, &libffi_args) }),
Type::F32 => Value::F32(unsafe { libffi_call(func_ptr, &libffi_args) }),
Type::F64 => Value::F64(unsafe { libffi_call(func_ptr, &libffi_args) }),
})
.or_else(|| {
// call with no returns
unsafe {
libffi_call::<()>(func_ptr, &libffi_args);
}
None
})
})
}
}
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#[derive(Debug)]
pub struct FuncRef(*const vm::Func);
impl FuncRef {
/// This needs to be unsafe because there is
/// no way to check whether the passed function
/// is valid and has the right signature.
pub unsafe fn new(f: *const vm::Func) -> Self {
FuncRef(f)
}
pub(crate) fn inner(&self) -> *const vm::Func {
self.0
}
}
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#[derive(Debug)]
pub enum Import {
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Func(FuncRef, FuncSig),
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Table(Arc<TableBacking>, Table),
Memory(Arc<LinearMemory>, Memory),
Global(Value),
}
pub struct Imports {
map: HashMap<String, HashMap<String, Import>>,
}
impl Imports {
pub fn new() -> Self {
Self {
map: HashMap::new(),
}
}
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pub fn add(&mut self, module: impl Into<String>, name: impl Into<String>, import: Import) {
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self.map
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.entry(module.into())
.or_insert_with(|| HashMap::new())
.insert(name.into(), import);
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}
pub fn get(&self, module: &str, name: &str) -> Option<&Import> {
self.map.get(module).and_then(|m| m.get(name))
}
}
impl ImportResolver for Imports {
fn get(&self, module: &str, name: &str) -> Option<&Import> {
self.get(module, name)
}
}
pub trait ImportResolver {
fn get(&self, module: &str, name: &str) -> Option<&Import>;
}
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// TODO Remove this later, only needed for compilation till emscripten is updated
impl Instance {
pub fn memory_offset_addr(&self, index: usize, offset: usize) -> *const usize {
unimplemented!("TODO replace this emscripten stub")
}
}