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//! An `Instance` contains all the runtime state used by execution of a
//! wasm module (except its callstack and register state). An
//! `InstanceHandle` is a reference-counting handle for an `Instance`.
use crate::export::Export;
use crate::externref::VMExternRefActivationsTable;
use crate::memory::{Memory, RuntimeMemoryCreator};
use crate::table::{Table, TableElement, TableElementType};
use crate::vmcontext::{
VMBuiltinFunctionsArray, VMCallerCheckedAnyfunc, VMContext, VMFunctionImport,
VMGlobalDefinition, VMGlobalImport, VMMemoryDefinition, VMMemoryImport, VMOpaqueContext,
VMRuntimeLimits, VMTableDefinition, VMTableImport, VMCONTEXT_MAGIC,
};
use crate::{
ExportFunction, ExportGlobal, ExportMemory, ExportTable, Imports, ModuleRuntimeInfo, Store,
VMFunctionBody,
};
use anyhow::Error;
use memoffset::offset_of;
use std::alloc::Layout;
use std::any::Any;
use std::convert::TryFrom;
use std::hash::Hash;
use std::ops::Range;
use std::ptr::NonNull;
use std::sync::atomic::AtomicU64;
use std::sync::Arc;
use std::{mem, ptr};
use wasmtime_environ::{
packed_option::ReservedValue, DataIndex, DefinedGlobalIndex, DefinedMemoryIndex,
DefinedTableIndex, ElemIndex, EntityIndex, EntityRef, EntitySet, FuncIndex, GlobalIndex,
GlobalInit, HostPtr, MemoryIndex, Module, PrimaryMap, SignatureIndex, TableIndex,
TableInitialization, TrapCode, VMOffsets, WasmType,
};
mod allocator;
pub use allocator::*;
/// A type that roughly corresponds to a WebAssembly instance, but is also used
/// for host-defined objects.
///
/// This structure is is never allocated directly but is instead managed through
/// an `InstanceHandle`. This structure ends with a `VMContext` which has a
/// dynamic size corresponding to the `module` configured within. Memory
/// management of this structure is always externalized.
///
/// Instances here can correspond to actual instantiated modules, but it's also
/// used ubiquitously for host-defined objects. For example creating a
/// host-defined memory will have a `module` that looks like it exports a single
/// memory (and similar for other constructs).
///
/// This `Instance` type is used as a ubiquitous representation for WebAssembly
/// values, whether or not they were created on the host or through a module.
#[repr(C)] // ensure that the vmctx field is last.
pub(crate) struct Instance {
/// The runtime info (corresponding to the "compiled module"
/// abstraction in higher layers) that is retained and needed for
/// lazy initialization. This provides access to the underlying
/// Wasm module entities, the compiled JIT code, metadata about
/// functions, lazy initialization state, etc.
runtime_info: Arc<dyn ModuleRuntimeInfo>,
/// Offsets in the `vmctx` region, precomputed from the `module` above.
offsets: VMOffsets<HostPtr>,
/// WebAssembly linear memory data.
///
/// This is where all runtime information about defined linear memories in
/// this module lives.
memories: PrimaryMap<DefinedMemoryIndex, Memory>,
/// WebAssembly table data.
///
/// Like memories, this is only for defined tables in the module and
/// contains all of their runtime state.
tables: PrimaryMap<DefinedTableIndex, Table>,
/// Stores the dropped passive element segments in this instantiation by index.
/// If the index is present in the set, the segment has been dropped.
dropped_elements: EntitySet<ElemIndex>,
/// Stores the dropped passive data segments in this instantiation by index.
/// If the index is present in the set, the segment has been dropped.
dropped_data: EntitySet<DataIndex>,
/// Hosts can store arbitrary per-instance information here.
///
/// Most of the time from Wasmtime this is `Box::new(())`, a noop
/// allocation, but some host-defined objects will store their state here.
host_state: Box<dyn Any + Send + Sync>,
/// Additional context used by compiled wasm code. This field is last, and
/// represents a dynamically-sized array that extends beyond the nominal
/// end of the struct (similar to a flexible array member).
vmctx: VMContext,
}
#[allow(clippy::cast_ptr_alignment)]
impl Instance {
/// Create an instance at the given memory address.
///
/// It is assumed the memory was properly aligned and the
/// allocation was `alloc_size` in bytes.
unsafe fn new_at(
ptr: *mut Instance,
alloc_size: usize,
offsets: VMOffsets<HostPtr>,
req: InstanceAllocationRequest,
memories: PrimaryMap<DefinedMemoryIndex, Memory>,
tables: PrimaryMap<DefinedTableIndex, Table>,
) {
// The allocation must be *at least* the size required of `Instance`.
assert!(alloc_size >= Self::alloc_layout(&offsets).size());
let module = req.runtime_info.module();
let dropped_elements = EntitySet::with_capacity(module.passive_elements.len());
let dropped_data = EntitySet::with_capacity(module.passive_data_map.len());
ptr::write(
ptr,
Instance {
runtime_info: req.runtime_info.clone(),
offsets,
memories,
tables,
dropped_elements,
dropped_data,
host_state: req.host_state,
vmctx: VMContext {
_marker: std::marker::PhantomPinned,
},
},
);
(*ptr).initialize_vmctx(module, req.store, req.imports);
}
/// Helper function to access various locations offset from our `*mut
/// VMContext` object.
unsafe fn vmctx_plus_offset<T>(&self, offset: u32) -> *mut T {
(self.vmctx_ptr().cast::<u8>())
.add(usize::try_from(offset).unwrap())
.cast()
}
pub(crate) fn module(&self) -> &Arc<Module> {
self.runtime_info.module()
}
/// Return the indexed `VMFunctionImport`.
fn imported_function(&self, index: FuncIndex) -> &VMFunctionImport {
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmfunction_import(index)) }
}
/// Return the index `VMTableImport`.
fn imported_table(&self, index: TableIndex) -> &VMTableImport {
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmtable_import(index)) }
}
/// Return the indexed `VMMemoryImport`.
fn imported_memory(&self, index: MemoryIndex) -> &VMMemoryImport {
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmmemory_import(index)) }
}
/// Return the indexed `VMGlobalImport`.
fn imported_global(&self, index: GlobalIndex) -> &VMGlobalImport {
unsafe { &*self.vmctx_plus_offset(self.offsets.vmctx_vmglobal_import(index)) }
}
/// Return the indexed `VMTableDefinition`.
#[allow(dead_code)]
fn table(&self, index: DefinedTableIndex) -> VMTableDefinition {
unsafe { *self.table_ptr(index) }
}
/// Updates the value for a defined table to `VMTableDefinition`.
fn set_table(&self, index: DefinedTableIndex, table: VMTableDefinition) {
unsafe {
*self.table_ptr(index) = table;
}
}
/// Return the indexed `VMTableDefinition`.
fn table_ptr(&self, index: DefinedTableIndex) -> *mut VMTableDefinition {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_vmtable_definition(index)) }
}
/// Get a locally defined or imported memory.
pub(crate) fn get_memory(&self, index: MemoryIndex) -> VMMemoryDefinition {
if let Some(defined_index) = self.module().defined_memory_index(index) {
self.memory(defined_index)
} else {
let import = self.imported_memory(index);
unsafe { VMMemoryDefinition::load(import.from) }
}
}
/// Return the indexed `VMMemoryDefinition`.
fn memory(&self, index: DefinedMemoryIndex) -> VMMemoryDefinition {
unsafe { VMMemoryDefinition::load(self.memory_ptr(index)) }
}
/// Set the indexed memory to `VMMemoryDefinition`.
fn set_memory(&self, index: DefinedMemoryIndex, mem: VMMemoryDefinition) {
unsafe {
*self.memory_ptr(index) = mem;
}
}
/// Return the indexed `VMMemoryDefinition`.
fn memory_ptr(&self, index: DefinedMemoryIndex) -> *mut VMMemoryDefinition {
unsafe { *self.vmctx_plus_offset(self.offsets.vmctx_vmmemory_pointer(index)) }
}
/// Return the indexed `VMGlobalDefinition`.
fn global(&self, index: DefinedGlobalIndex) -> &VMGlobalDefinition {
unsafe { &*self.global_ptr(index) }
}
/// Return the indexed `VMGlobalDefinition`.
fn global_ptr(&self, index: DefinedGlobalIndex) -> *mut VMGlobalDefinition {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_vmglobal_definition(index)) }
}
/// Get a raw pointer to the global at the given index regardless whether it
/// is defined locally or imported from another module.
///
/// Panics if the index is out of bound or is the reserved value.
pub(crate) fn defined_or_imported_global_ptr(
&self,
index: GlobalIndex,
) -> *mut VMGlobalDefinition {
if let Some(index) = self.module().defined_global_index(index) {
self.global_ptr(index)
} else {
self.imported_global(index).from
}
}
/// Return a pointer to the interrupts structure
pub fn runtime_limits(&self) -> *mut *const VMRuntimeLimits {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_runtime_limits()) }
}
/// Return a pointer to the global epoch counter used by this instance.
pub fn epoch_ptr(&self) -> *mut *const AtomicU64 {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_epoch_ptr()) }
}
/// Return a pointer to the `VMExternRefActivationsTable`.
pub fn externref_activations_table(&self) -> *mut *mut VMExternRefActivationsTable {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_externref_activations_table()) }
}
/// Gets a pointer to this instance's `Store` which was originally
/// configured on creation.
///
/// # Panics
///
/// This will panic if the originally configured store was `None`. That can
/// happen for host functions so host functions can't be queried what their
/// original `Store` was since it's just retained as null (since host
/// functions are shared amongst threads and don't all share the same
/// store).
#[inline]
pub fn store(&self) -> *mut dyn Store {
let ptr = unsafe { *self.vmctx_plus_offset::<*mut dyn Store>(self.offsets.vmctx_store()) };
assert!(!ptr.is_null());
ptr
}
pub unsafe fn set_store(&mut self, store: Option<*mut dyn Store>) {
if let Some(store) = store {
*self.vmctx_plus_offset(self.offsets.vmctx_store()) = store;
*self.runtime_limits() = (*store).vmruntime_limits();
*self.epoch_ptr() = (*store).epoch_ptr();
*self.externref_activations_table() = (*store).externref_activations_table().0;
} else {
assert_eq!(
mem::size_of::<*mut dyn Store>(),
mem::size_of::<[*mut (); 2]>()
);
*self.vmctx_plus_offset::<[*mut (); 2]>(self.offsets.vmctx_store()) =
[ptr::null_mut(), ptr::null_mut()];
*self.runtime_limits() = ptr::null_mut();
*self.epoch_ptr() = ptr::null_mut();
*self.externref_activations_table() = ptr::null_mut();
}
}
pub(crate) unsafe fn set_callee(&mut self, callee: Option<NonNull<VMFunctionBody>>) {
*self.vmctx_plus_offset(self.offsets.vmctx_callee()) =
callee.map_or(ptr::null_mut(), |c| c.as_ptr());
}
/// Return a reference to the vmctx used by compiled wasm code.
#[inline]
pub fn vmctx(&self) -> &VMContext {
&self.vmctx
}
/// Return a raw pointer to the vmctx used by compiled wasm code.
#[inline]
pub fn vmctx_ptr(&self) -> *mut VMContext {
self.vmctx() as *const VMContext as *mut VMContext
}
fn get_exported_func(&mut self, index: FuncIndex) -> ExportFunction {
let anyfunc = self.get_caller_checked_anyfunc(index).unwrap();
let anyfunc = NonNull::new(anyfunc as *const VMCallerCheckedAnyfunc as *mut _).unwrap();
ExportFunction { anyfunc }
}
fn get_exported_table(&mut self, index: TableIndex) -> ExportTable {
let (definition, vmctx) = if let Some(def_index) = self.module().defined_table_index(index)
{
(self.table_ptr(def_index), self.vmctx_ptr())
} else {
let import = self.imported_table(index);
(import.from, import.vmctx)
};
ExportTable {
definition,
vmctx,
table: self.module().table_plans[index].clone(),
}
}
fn get_exported_memory(&mut self, index: MemoryIndex) -> ExportMemory {
let (definition, vmctx, def_index) =
if let Some(def_index) = self.module().defined_memory_index(index) {
(self.memory_ptr(def_index), self.vmctx_ptr(), def_index)
} else {
let import = self.imported_memory(index);
(import.from, import.vmctx, import.index)
};
ExportMemory {
definition,
vmctx,
memory: self.module().memory_plans[index].clone(),
index: def_index,
}
}
fn get_exported_global(&mut self, index: GlobalIndex) -> ExportGlobal {
ExportGlobal {
definition: if let Some(def_index) = self.module().defined_global_index(index) {
self.global_ptr(def_index)
} else {
self.imported_global(index).from
},
global: self.module().globals[index],
}
}
/// Return an iterator over the exports of this instance.
///
/// Specifically, it provides access to the key-value pairs, where the keys
/// are export names, and the values are export declarations which can be
/// resolved `lookup_by_declaration`.
pub fn exports(&self) -> indexmap::map::Iter<String, EntityIndex> {
self.module().exports.iter()
}
/// Return a reference to the custom state attached to this instance.
#[inline]
pub fn host_state(&self) -> &dyn Any {
&*self.host_state
}
/// Return the offset from the vmctx pointer to its containing Instance.
#[inline]
pub(crate) fn vmctx_offset() -> isize {
offset_of!(Self, vmctx) as isize
}
/// Return the table index for the given `VMTableDefinition`.
unsafe fn table_index(&self, table: &VMTableDefinition) -> DefinedTableIndex {
let index = DefinedTableIndex::new(
usize::try_from(
(table as *const VMTableDefinition)
.offset_from(self.table_ptr(DefinedTableIndex::new(0))),
)
.unwrap(),
);
assert!(index.index() < self.tables.len());
index
}
/// Grow memory by the specified amount of pages.
///
/// Returns `None` if memory can't be grown by the specified amount
/// of pages. Returns `Some` with the old size in bytes if growth was
/// successful.
pub(crate) fn memory_grow(
&mut self,
index: MemoryIndex,
delta: u64,
) -> Result<Option<usize>, Error> {
let (idx, instance) = if let Some(idx) = self.module().defined_memory_index(index) {
(idx, self)
} else {
let import = self.imported_memory(index);
unsafe {
let foreign_instance = (*import.vmctx).instance_mut();
(import.index, foreign_instance)
}
};
let store = unsafe { &mut *instance.store() };
let memory = &mut instance.memories[idx];
let result = unsafe { memory.grow(delta, Some(store)) };
// Update the state used by a non-shared Wasm memory in case the base
// pointer and/or the length changed.
if memory.as_shared_memory().is_none() {
let vmmemory = memory.vmmemory();
instance.set_memory(idx, vmmemory);
}
result
}
pub(crate) fn table_element_type(&mut self, table_index: TableIndex) -> TableElementType {
unsafe { (*self.get_table(table_index)).element_type() }
}
/// Grow table by the specified amount of elements, filling them with
/// `init_value`.
///
/// Returns `None` if table can't be grown by the specified amount of
/// elements, or if `init_value` is the wrong type of table element.
pub(crate) fn table_grow(
&mut self,
table_index: TableIndex,
delta: u32,
init_value: TableElement,
) -> Result<Option<u32>, Error> {
let (defined_table_index, instance) =
self.get_defined_table_index_and_instance(table_index);
instance.defined_table_grow(defined_table_index, delta, init_value)
}
fn defined_table_grow(
&mut self,
table_index: DefinedTableIndex,
delta: u32,
init_value: TableElement,
) -> Result<Option<u32>, Error> {
let store = unsafe { &mut *self.store() };
let table = self
.tables
.get_mut(table_index)
.unwrap_or_else(|| panic!("no table for index {}", table_index.index()));
let result = unsafe { table.grow(delta, init_value, store) };
// Keep the `VMContext` pointers used by compiled Wasm code up to
// date.
let element = self.tables[table_index].vmtable();
self.set_table(table_index, element);
result
}
fn alloc_layout(offsets: &VMOffsets<HostPtr>) -> Layout {
let size = mem::size_of::<Self>()
.checked_add(usize::try_from(offsets.size_of_vmctx()).unwrap())
.unwrap();
let align = mem::align_of::<Self>();
Layout::from_size_align(size, align).unwrap()
}
/// Construct a new VMCallerCheckedAnyfunc for the given function
/// (imported or defined in this module) and store into the given
/// location. Used during lazy initialization.
///
/// Note that our current lazy-init scheme actually calls this every
/// time the anyfunc pointer is fetched; this turns out to be better
/// than tracking state related to whether it's been initialized
/// before, because resetting that state on (re)instantiation is
/// very expensive if there are many anyfuncs.
fn construct_anyfunc(
&mut self,
index: FuncIndex,
sig: SignatureIndex,
into: *mut VMCallerCheckedAnyfunc,
) {
let type_index = self.runtime_info.signature(sig);
let (func_ptr, vmctx) = if let Some(def_index) = self.module().defined_func_index(index) {
(
(self.runtime_info.image_base()
+ self.runtime_info.function_info(def_index).start as usize)
as *mut _,
VMOpaqueContext::from_vmcontext(self.vmctx_ptr()),
)
} else {
let import = self.imported_function(index);
(import.body.as_ptr(), import.vmctx)
};
// Safety: we have a `&mut self`, so we have exclusive access
// to this Instance.
unsafe {
*into = VMCallerCheckedAnyfunc {
vmctx,
type_index,
func_ptr: NonNull::new(func_ptr).expect("Non-null function pointer"),
};
}
}
/// Get a `&VMCallerCheckedAnyfunc` for the given `FuncIndex`.
///
/// Returns `None` if the index is the reserved index value.
///
/// The returned reference is a stable reference that won't be moved and can
/// be passed into JIT code.
pub(crate) fn get_caller_checked_anyfunc(
&mut self,
index: FuncIndex,
) -> Option<*mut VMCallerCheckedAnyfunc> {
if index == FuncIndex::reserved_value() {
return None;
}
// Safety: we have a `&mut self`, so we have exclusive access
// to this Instance.
unsafe {
// For now, we eagerly initialize an anyfunc struct in-place
// whenever asked for a reference to it. This is mostly
// fine, because in practice each anyfunc is unlikely to be
// requested more than a few times: once-ish for funcref
// tables used for call_indirect (the usual compilation
// strategy places each function in the table at most once),
// and once or a few times when fetching exports via API.
// Note that for any case driven by table accesses, the lazy
// table init behaves like a higher-level cache layer that
// protects this initialization from happening multiple
// times, via that particular table at least.
//
// When `ref.func` becomes more commonly used or if we
// otherwise see a use-case where this becomes a hotpath,
// we can reconsider by using some state to track
// "uninitialized" explicitly, for example by zeroing the
// anyfuncs (perhaps together with other
// zeroed-at-instantiate-time state) or using a separate
// is-initialized bitmap.
//
// We arrived at this design because zeroing memory is
// expensive, so it's better for instantiation performance
// if we don't have to track "is-initialized" state at
// all!
let func = &self.module().functions[index];
let sig = func.signature;
let anyfunc: *mut VMCallerCheckedAnyfunc = self
.vmctx_plus_offset::<VMCallerCheckedAnyfunc>(
self.offsets.vmctx_anyfunc(func.anyfunc),
);
self.construct_anyfunc(index, sig, anyfunc);
Some(anyfunc)
}
}
/// The `table.init` operation: initializes a portion of a table with a
/// passive element.
///
/// # Errors
///
/// Returns a `Trap` error when the range within the table is out of bounds
/// or the range within the passive element is out of bounds.
pub(crate) fn table_init(
&mut self,
table_index: TableIndex,
elem_index: ElemIndex,
dst: u32,
src: u32,
len: u32,
) -> Result<(), TrapCode> {
// TODO: this `clone()` shouldn't be necessary but is used for now to
// inform `rustc` that the lifetime of the elements here are
// disconnected from the lifetime of `self`.
let module = self.module().clone();
let elements = match module.passive_elements_map.get(&elem_index) {
Some(index) if !self.dropped_elements.contains(elem_index) => {
module.passive_elements[*index].as_ref()
}
_ => &[],
};
self.table_init_segment(table_index, elements, dst, src, len)
}
pub(crate) fn table_init_segment(
&mut self,
table_index: TableIndex,
elements: &[FuncIndex],
dst: u32,
src: u32,
len: u32,
) -> Result<(), TrapCode> {
// https://webassembly.github.io/bulk-memory-operations/core/exec/instructions.html#exec-table-init
let table = unsafe { &mut *self.get_table(table_index) };
let elements = match elements
.get(usize::try_from(src).unwrap()..)
.and_then(|s| s.get(..usize::try_from(len).unwrap()))
{
Some(elements) => elements,
None => return Err(TrapCode::TableOutOfBounds),
};
match table.element_type() {
TableElementType::Func => {
table.init_funcs(
dst,
elements.iter().map(|idx| {
self.get_caller_checked_anyfunc(*idx)
.unwrap_or(std::ptr::null_mut())
}),
)?;
}
TableElementType::Extern => {
debug_assert!(elements.iter().all(|e| *e == FuncIndex::reserved_value()));
table.fill(dst, TableElement::ExternRef(None), len)?;
}
}
Ok(())
}
/// Drop an element.
pub(crate) fn elem_drop(&mut self, elem_index: ElemIndex) {
// https://webassembly.github.io/reference-types/core/exec/instructions.html#exec-elem-drop
self.dropped_elements.insert(elem_index);
// Note that we don't check that we actually removed a segment because
// dropping a non-passive segment is a no-op (not a trap).
}
/// Get a locally-defined memory.
pub(crate) fn get_defined_memory(&mut self, index: DefinedMemoryIndex) -> *mut Memory {
ptr::addr_of_mut!(self.memories[index])
}
/// Do a `memory.copy`
///
/// # Errors
///
/// Returns a `Trap` error when the source or destination ranges are out of
/// bounds.
pub(crate) fn memory_copy(
&mut self,
dst_index: MemoryIndex,
dst: u64,
src_index: MemoryIndex,
src: u64,
len: u64,
) -> Result<(), TrapCode> {
// https://webassembly.github.io/reference-types/core/exec/instructions.html#exec-memory-copy
let src_mem = self.get_memory(src_index);
let dst_mem = self.get_memory(dst_index);
let src = self.validate_inbounds(src_mem.current_length(), src, len)?;
let dst = self.validate_inbounds(dst_mem.current_length(), dst, len)?;
// Bounds and casts are checked above, by this point we know that
// everything is safe.
unsafe {
let dst = dst_mem.base.add(dst);
let src = src_mem.base.add(src);
// FIXME audit whether this is safe in the presence of shared memory
// (https://github.com/bytecodealliance/wasmtime/issues/4203).
ptr::copy(src, dst, len as usize);
}
Ok(())
}
fn validate_inbounds(&self, max: usize, ptr: u64, len: u64) -> Result<usize, TrapCode> {
let oob = || TrapCode::HeapOutOfBounds;
let end = ptr
.checked_add(len)
.and_then(|i| usize::try_from(i).ok())
.ok_or_else(oob)?;
if end > max {
Err(oob())
} else {
Ok(ptr as usize)
}
}
/// Perform the `memory.fill` operation on a locally defined memory.
///
/// # Errors
///
/// Returns a `Trap` error if the memory range is out of bounds.
pub(crate) fn memory_fill(
&mut self,
memory_index: MemoryIndex,
dst: u64,
val: u8,
len: u64,
) -> Result<(), TrapCode> {
let memory = self.get_memory(memory_index);
let dst = self.validate_inbounds(memory.current_length(), dst, len)?;
// Bounds and casts are checked above, by this point we know that
// everything is safe.
unsafe {
let dst = memory.base.add(dst);
// FIXME audit whether this is safe in the presence of shared memory
// (https://github.com/bytecodealliance/wasmtime/issues/4203).
ptr::write_bytes(dst, val, len as usize);
}
Ok(())
}
/// Performs the `memory.init` operation.
///
/// # Errors
///
/// Returns a `Trap` error if the destination range is out of this module's
/// memory's bounds or if the source range is outside the data segment's
/// bounds.
pub(crate) fn memory_init(
&mut self,
memory_index: MemoryIndex,
data_index: DataIndex,
dst: u64,
src: u32,
len: u32,
) -> Result<(), TrapCode> {
let range = match self.module().passive_data_map.get(&data_index).cloned() {
Some(range) if !self.dropped_data.contains(data_index) => range,
_ => 0..0,
};
self.memory_init_segment(memory_index, range, dst, src, len)
}
pub(crate) fn wasm_data(&self, range: Range<u32>) -> &[u8] {
&self.runtime_info.wasm_data()[range.start as usize..range.end as usize]
}
pub(crate) fn memory_init_segment(
&mut self,
memory_index: MemoryIndex,
range: Range<u32>,
dst: u64,
src: u32,
len: u32,
) -> Result<(), TrapCode> {
// https://webassembly.github.io/bulk-memory-operations/core/exec/instructions.html#exec-memory-init
let memory = self.get_memory(memory_index);
let data = self.wasm_data(range);
let dst = self.validate_inbounds(memory.current_length(), dst, len.into())?;
let src = self.validate_inbounds(data.len(), src.into(), len.into())?;
let len = len as usize;
unsafe {
let src_start = data.as_ptr().add(src);
let dst_start = memory.base.add(dst);
// FIXME audit whether this is safe in the presence of shared memory
// (https://github.com/bytecodealliance/wasmtime/issues/4203).
ptr::copy_nonoverlapping(src_start, dst_start, len);
}
Ok(())
}
/// Drop the given data segment, truncating its length to zero.
pub(crate) fn data_drop(&mut self, data_index: DataIndex) {
self.dropped_data.insert(data_index);
// Note that we don't check that we actually removed a segment because
// dropping a non-passive segment is a no-op (not a trap).
}
/// Get a table by index regardless of whether it is locally-defined
/// or an imported, foreign table. Ensure that the given range of
/// elements in the table is lazily initialized. We define this
/// operation all-in-one for safety, to ensure the lazy-init
/// happens.
///
/// Takes an `Iterator` for the index-range to lazy-initialize,
/// for flexibility. This can be a range, single item, or empty
/// sequence, for example. The iterator should return indices in
/// increasing order, so that the break-at-out-of-bounds behavior
/// works correctly.
pub(crate) fn get_table_with_lazy_init(
&mut self,
table_index: TableIndex,
range: impl Iterator<Item = u32>,
) -> *mut Table {
let (idx, instance) = self.get_defined_table_index_and_instance(table_index);
let elt_ty = instance.tables[idx].element_type();
if elt_ty == TableElementType::Func {
for i in range {
let value = match instance.tables[idx].get(i) {
Some(value) => value,
None => {
// Out-of-bounds; caller will handle by likely
// throwing a trap. No work to do to lazy-init
// beyond the end.
break;
}
};
if value.is_uninit() {
let table_init = match &instance.module().table_initialization {
// We unfortunately can't borrow `tables`
// outside the loop because we need to call
// `get_caller_checked_anyfunc` (a `&mut`
// method) below; so unwrap it dynamically
// here.
TableInitialization::FuncTable { tables, .. } => tables,
_ => break,
}
.get(table_index);
// The TableInitialization::FuncTable elements table may
// be smaller than the current size of the table: it
// always matches the initial table size, if present. We
// want to iterate up through the end of the accessed
// index range so that we set an "initialized null" even
// if there is no initializer. We do a checked `get()` on
// the initializer table below and unwrap to a null if
// we're past its end.
let func_index =
table_init.and_then(|indices| indices.get(i as usize).cloned());
let anyfunc = func_index
.and_then(|func_index| instance.get_caller_checked_anyfunc(func_index))
.unwrap_or(std::ptr::null_mut());
let value = TableElement::FuncRef(anyfunc);
instance.tables[idx]
.set(i, value)
.expect("Table type should match and index should be in-bounds");
}
}
}
ptr::addr_of_mut!(instance.tables[idx])
}
/// Get a table by index regardless of whether it is locally-defined or an
/// imported, foreign table.
pub(crate) fn get_table(&mut self, table_index: TableIndex) -> *mut Table {
let (idx, instance) = self.get_defined_table_index_and_instance(table_index);
ptr::addr_of_mut!(instance.tables[idx])
}
/// Get a locally-defined table.
pub(crate) fn get_defined_table(&mut self, index: DefinedTableIndex) -> *mut Table {
ptr::addr_of_mut!(self.tables[index])
}
pub(crate) fn get_defined_table_index_and_instance(
&mut self,
index: TableIndex,
) -> (DefinedTableIndex, &mut Instance) {
if let Some(defined_table_index) = self.module().defined_table_index(index) {
(defined_table_index, self)
} else {
let import = self.imported_table(index);
unsafe {
let foreign_instance = (*import.vmctx).instance_mut();
let foreign_table_def = &*import.from;
let foreign_table_index = foreign_instance.table_index(foreign_table_def);
(foreign_table_index, foreign_instance)
}
}
}
/// Initialize the VMContext data associated with this Instance.
///
/// The `VMContext` memory is assumed to be uninitialized; any field
/// that we need in a certain state will be explicitly written by this
/// function.
unsafe fn initialize_vmctx(&mut self, module: &Module, store: StorePtr, imports: Imports) {
assert!(std::ptr::eq(module, self.module().as_ref()));
*self.vmctx_plus_offset(self.offsets.vmctx_magic()) = VMCONTEXT_MAGIC;
self.set_callee(None);
self.set_store(store.as_raw());
// Initialize shared signatures
let signatures = self.runtime_info.signature_ids();
*self.vmctx_plus_offset(self.offsets.vmctx_signature_ids_array()) = signatures.as_ptr();
// Initialize the built-in functions
*self.vmctx_plus_offset(self.offsets.vmctx_builtin_functions()) =
&VMBuiltinFunctionsArray::INIT;
// Initialize the imports
debug_assert_eq!(imports.functions.len(), module.num_imported_funcs);
ptr::copy_nonoverlapping(
imports.functions.as_ptr(),
self.vmctx_plus_offset(self.offsets.vmctx_imported_functions_begin()),
imports.functions.len(),
);
debug_assert_eq!(imports.tables.len(), module.num_imported_tables);
ptr::copy_nonoverlapping(
imports.tables.as_ptr(),
self.vmctx_plus_offset(self.offsets.vmctx_imported_tables_begin()),
imports.tables.len(),
);
debug_assert_eq!(imports.memories.len(), module.num_imported_memories);
ptr::copy_nonoverlapping(
imports.memories.as_ptr(),
self.vmctx_plus_offset(self.offsets.vmctx_imported_memories_begin()),
imports.memories.len(),
);
debug_assert_eq!(imports.globals.len(), module.num_imported_globals);
ptr::copy_nonoverlapping(
imports.globals.as_ptr(),
self.vmctx_plus_offset(self.offsets.vmctx_imported_globals_begin()),
imports.globals.len(),
);
// N.B.: there is no need to initialize the anyfuncs array because
// we eagerly construct each element in it whenever asked for a
// reference to that element. In other words, there is no state
// needed to track the lazy-init, so we don't need to initialize
// any state now.
// Initialize the defined tables
let mut ptr = self.vmctx_plus_offset(self.offsets.vmctx_tables_begin());
for i in 0..module.table_plans.len() - module.num_imported_tables {
ptr::write(ptr, self.tables[DefinedTableIndex::new(i)].vmtable());
ptr = ptr.add(1);
}
// Initialize the defined memories. This fills in both the
// `defined_memories` table and the `owned_memories` table at the same
// time. Entries in `defined_memories` hold a pointer to a definition
// (all memories) whereas the `owned_memories` hold the actual
// definitions of memories owned (not shared) in the module.
let mut ptr = self.vmctx_plus_offset(self.offsets.vmctx_memories_begin());
let mut owned_ptr = self.vmctx_plus_offset(self.offsets.vmctx_owned_memories_begin());
for i in 0..module.memory_plans.len() - module.num_imported_memories {
let defined_memory_index = DefinedMemoryIndex::new(i);
let memory_index = module.memory_index(defined_memory_index);
if module.memory_plans[memory_index].memory.shared {
let def_ptr = self.memories[defined_memory_index]
.as_shared_memory()
.unwrap()
.vmmemory_ptr_mut();
ptr::write(ptr, def_ptr);
} else {
ptr::write(owned_ptr, self.memories[defined_memory_index].vmmemory());
ptr::write(ptr, owned_ptr);
owned_ptr = owned_ptr.add(1);
}
ptr = ptr.add(1);
}
// Initialize the defined globals
self.initialize_vmctx_globals(module);
}
unsafe fn initialize_vmctx_globals(&mut self, module: &Module) {
let num_imports = module.num_imported_globals;
for (index, global) in module.globals.iter().skip(num_imports) {
let def_index = module.defined_global_index(index).unwrap();
let to = self.global_ptr(def_index);
// Initialize the global before writing to it
ptr::write(to, VMGlobalDefinition::new());
match global.initializer {
GlobalInit::I32Const(x) => *(*to).as_i32_mut() = x,
GlobalInit::I64Const(x) => *(*to).as_i64_mut() = x,
GlobalInit::F32Const(x) => *(*to).as_f32_bits_mut() = x,
GlobalInit::F64Const(x) => *(*to).as_f64_bits_mut() = x,
GlobalInit::V128Const(x) => *(*to).as_u128_mut() = x,
GlobalInit::GetGlobal(x) => {
let from = if let Some(def_x) = module.defined_global_index(x) {
self.global(def_x)
} else {
&*self.imported_global(x).from
};
// Globals of type `externref` need to manage the reference
// count as values move between globals, everything else is just
// copy-able bits.
match global.wasm_ty {
WasmType::ExternRef => {
*(*to).as_externref_mut() = from.as_externref().clone()
}
_ => ptr::copy_nonoverlapping(from, to, 1),
}
}
GlobalInit::RefFunc(f) => {
*(*to).as_anyfunc_mut() = self.get_caller_checked_anyfunc(f).unwrap()
as *const VMCallerCheckedAnyfunc;
}
GlobalInit::RefNullConst => match global.wasm_ty {
// `VMGlobalDefinition::new()` already zeroed out the bits
WasmType::FuncRef => {}
WasmType::ExternRef => {}
ty => panic!("unsupported reference type for global: {:?}", ty),
},
GlobalInit::Import => panic!("locally-defined global initialized as import"),
}
}
}
}
impl Drop for Instance {
fn drop(&mut self) {
// Drop any defined globals
for (idx, global) in self.module().globals.iter() {
let idx = match self.module().defined_global_index(idx) {
Some(idx) => idx,
None => continue,
};
match global.wasm_ty {
// For now only externref globals need to get destroyed
WasmType::ExternRef => {}
_ => continue,
}
unsafe {
drop((*self.global_ptr(idx)).as_externref_mut().take());
}
}
}
}
/// A handle holding an `Instance` of a WebAssembly module.
#[derive(Hash, PartialEq, Eq)]
pub struct InstanceHandle {
instance: *mut Instance,
}
// These are only valid if the `Instance` type is send/sync, hence the
// assertion below.
unsafe impl Send for InstanceHandle {}
unsafe impl Sync for InstanceHandle {}
fn _assert_send_sync() {
fn _assert<T: Send + Sync>() {}
_assert::<Instance>();
}
impl InstanceHandle {
/// Create a new `InstanceHandle` pointing at the instance
/// pointed to by the given `VMContext` pointer.
///
/// # Safety
/// This is unsafe because it doesn't work on just any `VMContext`, it must
/// be a `VMContext` allocated as part of an `Instance`.
#[inline]
pub unsafe fn from_vmctx(vmctx: *mut VMContext) -> Self {
let instance = (&mut *vmctx).instance();
Self {
instance: instance as *const Instance as *mut Instance,
}
}
/// Return a reference to the vmctx used by compiled wasm code.
pub fn vmctx(&self) -> &VMContext {
self.instance().vmctx()
}
/// Return a raw pointer to the vmctx used by compiled wasm code.
#[inline]
pub fn vmctx_ptr(&self) -> *mut VMContext {
self.instance().vmctx_ptr()
}
/// Return a reference to a module.
pub fn module(&self) -> &Arc<Module> {
self.instance().module()
}
/// Lookup a function by index.
pub fn get_exported_func(&mut self, export: FuncIndex) -> ExportFunction {
self.instance_mut().get_exported_func(export)
}
/// Lookup a global by index.
pub fn get_exported_global(&mut self, export: GlobalIndex) -> ExportGlobal {
self.instance_mut().get_exported_global(export)
}
/// Lookup a memory by index.
pub fn get_exported_memory(&mut self, export: MemoryIndex) -> ExportMemory {
self.instance_mut().get_exported_memory(export)
}
/// Lookup a table by index.
pub fn get_exported_table(&mut self, export: TableIndex) -> ExportTable {
self.instance_mut().get_exported_table(export)
}
/// Lookup an item with the given index.
pub fn get_export_by_index(&mut self, export: EntityIndex) -> Export {
match export {
EntityIndex::Function(i) => Export::Function(self.get_exported_func(i)),
EntityIndex::Global(i) => Export::Global(self.get_exported_global(i)),
EntityIndex::Table(i) => Export::Table(self.get_exported_table(i)),
EntityIndex::Memory(i) => Export::Memory(self.get_exported_memory(i)),
}
}
/// Return an iterator over the exports of this instance.
///
/// Specifically, it provides access to the key-value pairs, where the keys
/// are export names, and the values are export declarations which can be
/// resolved `lookup_by_declaration`.
pub fn exports(&self) -> indexmap::map::Iter<String, EntityIndex> {
self.instance().exports()
}
/// Return a reference to the custom state attached to this instance.
pub fn host_state(&self) -> &dyn Any {
self.instance().host_state()
}
/// Get a memory defined locally within this module.
pub fn get_defined_memory(&mut self, index: DefinedMemoryIndex) -> *mut Memory {
self.instance_mut().get_defined_memory(index)
}
/// Return the table index for the given `VMTableDefinition` in this instance.
pub unsafe fn table_index(&self, table: &VMTableDefinition) -> DefinedTableIndex {
self.instance().table_index(table)
}
/// Get a table defined locally within this module.
pub fn get_defined_table(&mut self, index: DefinedTableIndex) -> *mut Table {
self.instance_mut().get_defined_table(index)
}
/// Get a table defined locally within this module, lazily
/// initializing the given range first.
pub fn get_defined_table_with_lazy_init(
&mut self,
index: DefinedTableIndex,
range: impl Iterator<Item = u32>,
) -> *mut Table {
let index = self.instance().module().table_index(index);
self.instance_mut().get_table_with_lazy_init(index, range)
}
/// Return a reference to the contained `Instance`.
#[inline]
pub(crate) fn instance(&self) -> &Instance {
unsafe { &*(self.instance as *const Instance) }
}
pub(crate) fn instance_mut(&mut self) -> &mut Instance {
unsafe { &mut *self.instance }
}
/// Returns the `Store` pointer that was stored on creation
#[inline]
pub fn store(&self) -> *mut dyn Store {
self.instance().store()
}
/// Configure the `*mut dyn Store` internal pointer after-the-fact.
///
/// This is provided for the original `Store` itself to configure the first
/// self-pointer after the original `Box` has been initialized.
pub unsafe fn set_store(&mut self, store: *mut dyn Store) {
self.instance_mut().set_store(Some(store));
}
/// Returns a clone of this instance.
///
/// This is unsafe because the returned handle here is just a cheap clone
/// of the internals, there's no lifetime tracking around its validity.
/// You'll need to ensure that the returned handles all go out of scope at
/// the same time.
#[inline]
pub unsafe fn clone(&self) -> InstanceHandle {
InstanceHandle {
instance: self.instance,
}
}
}