Enum wasmtime_runtime::Table
source · pub enum Table {
Static {
data: &'static mut [usize],
size: u32,
ty: TableElementType,
},
Dynamic {
elements: Vec<usize>,
ty: TableElementType,
maximum: Option<u32>,
},
}Expand description
Represents an instance’s table.
Variants§
Static
Fields
§
data: &'static mut [usize]Where data for this table is stored. The length of this list is the maximum size of the table.
§
ty: TableElementTypeThe type of this table.
A “static” table where storage space is managed externally, currently used with the pooling allocator.
Dynamic
Fields
§
elements: Vec<usize>Dynamically managed storage space for this table. The length of this vector is the current size of the table.
§
ty: TableElementTypeThe type of this table.
A “dynamic” table where table storage space is dynamically allocated via
malloc (aka Rust’s Vec).
Implementations§
source§impl Table
impl Table
sourcepub fn new_dynamic(plan: &TablePlan, store: &mut dyn Store) -> Result<Self>
pub fn new_dynamic(plan: &TablePlan, store: &mut dyn Store) -> Result<Self>
Create a new dynamic (movable) table instance for the specified table plan.
Examples found in repository?
src/instance/allocator.rs (lines 394-398)
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fn create_tables(
store: &mut StorePtr,
runtime_info: &Arc<dyn ModuleRuntimeInfo>,
) -> Result<PrimaryMap<DefinedTableIndex, Table>> {
let module = runtime_info.module();
let num_imports = module.num_imported_tables;
let mut tables: PrimaryMap<DefinedTableIndex, _> =
PrimaryMap::with_capacity(module.table_plans.len() - num_imports);
for (_, table) in module.table_plans.iter().skip(num_imports) {
tables.push(Table::new_dynamic(table, unsafe {
store
.get()
.expect("if module has table plans, store is not empty")
})?);
}
Ok(tables)
}sourcepub fn new_static(
plan: &TablePlan,
data: &'static mut [usize],
store: &mut dyn Store
) -> Result<Self>
pub fn new_static(
plan: &TablePlan,
data: &'static mut [usize],
store: &mut dyn Store
) -> Result<Self>
Create a new static (immovable) table instance for the specified table plan.
sourcepub fn element_type(&self) -> TableElementType
pub fn element_type(&self) -> TableElementType
Returns the type of the elements in this table.
Examples found in repository?
src/instance.rs (line 438)
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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 = unsafe {
let base: *const VMSharedSignatureIndex =
*self.vmctx_plus_offset(self.offsets().vmctx_signature_ids_array());
*base.add(sig.index())
};
let (func_ptr, vmctx) = if let Some(def_index) = self.module().defined_func_index(index) {
(
self.runtime_info.function(def_index),
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<(), Trap> {
// 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<(), Trap> {
// 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(Trap::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<(), Trap> {
// 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, Trap> {
let oob = || Trap::MemoryOutOfBounds;
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<(), Trap> {
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<(), Trap> {
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<(), Trap> {
// 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])
}More examples
src/table.rs (line 271)
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pub fn init_funcs(
&mut self,
dst: u32,
items: impl ExactSizeIterator<Item = *mut VMCallerCheckedAnyfunc>,
) -> Result<(), Trap> {
assert!(self.element_type() == TableElementType::Func);
let elements = match self
.elements_mut()
.get_mut(usize::try_from(dst).unwrap()..)
.and_then(|s| s.get_mut(..items.len()))
{
Some(elements) => elements,
None => return Err(Trap::TableOutOfBounds),
};
for (item, slot) in items.zip(elements) {
unsafe {
*slot = TableElement::FuncRef(item).into_table_value();
}
}
Ok(())
}
/// Fill `table[dst..dst + len]` with `val`.
///
/// Returns a trap error on out-of-bounds accesses.
pub fn fill(&mut self, dst: u32, val: TableElement, len: u32) -> Result<(), Trap> {
let start = dst as usize;
let end = start
.checked_add(len as usize)
.ok_or_else(|| Trap::TableOutOfBounds)?;
if end > self.size() as usize {
return Err(Trap::TableOutOfBounds);
}
debug_assert!(self.type_matches(&val));
let ty = self.element_type();
if let Some((last, elements)) = self.elements_mut()[start..end].split_last_mut() {
for e in elements {
Self::set_raw(ty, e, val.clone());
}
Self::set_raw(ty, last, val);
}
Ok(())
}
/// Grow table by the specified amount of elements.
///
/// Returns the previous size of the table if growth is successful.
///
/// Returns `None` if table can't be grown by the specified amount of
/// elements, or if the `init_value` is the wrong kind of table element.
///
/// # Unsafety
///
/// Resizing the table can reallocate its internal elements buffer. This
/// table's instance's `VMContext` has raw pointers to the elements buffer
/// that are used by Wasm, and they need to be fixed up before we call into
/// Wasm again. Failure to do so will result in use-after-free inside Wasm.
///
/// Generally, prefer using `InstanceHandle::table_grow`, which encapsulates
/// this unsafety.
pub unsafe fn grow(
&mut self,
delta: u32,
init_value: TableElement,
store: &mut dyn Store,
) -> Result<Option<u32>, Error> {
let old_size = self.size();
let new_size = match old_size.checked_add(delta) {
Some(s) => s,
None => return Ok(None),
};
if !store.table_growing(old_size, new_size, self.maximum())? {
return Ok(None);
}
if let Some(max) = self.maximum() {
if new_size > max {
store.table_grow_failed(&format_err!("Table maximum size exceeded"));
return Ok(None);
}
}
debug_assert!(self.type_matches(&init_value));
// First resize the storage and then fill with the init value
match self {
Table::Static { size, data, .. } => {
debug_assert!(data[*size as usize..new_size as usize]
.iter()
.all(|x| *x == 0));
*size = new_size;
}
Table::Dynamic { elements, .. } => {
elements.resize(new_size as usize, 0);
}
}
self.fill(old_size, init_value, delta)
.expect("table should not be out of bounds");
Ok(Some(old_size))
}
/// Get reference to the specified element.
///
/// Returns `None` if the index is out of bounds.
pub fn get(&self, index: u32) -> Option<TableElement> {
self.elements()
.get(index as usize)
.map(|p| unsafe { TableElement::clone_from_table_value(self.element_type(), *p) })
}
/// Set reference to the specified element.
///
/// # Errors
///
/// Returns an error if `index` is out of bounds or if this table type does
/// not match the element type.
pub fn set(&mut self, index: u32, elem: TableElement) -> Result<(), ()> {
if !self.type_matches(&elem) {
return Err(());
}
let ty = self.element_type();
let e = self.elements_mut().get_mut(index as usize).ok_or(())?;
Self::set_raw(ty, e, elem);
Ok(())
}
/// Copy `len` elements from `src_table[src_index..]` into `dst_table[dst_index..]`.
///
/// # Errors
///
/// Returns an error if the range is out of bounds of either the source or
/// destination tables.
pub unsafe fn copy(
dst_table: *mut Self,
src_table: *mut Self,
dst_index: u32,
src_index: u32,
len: u32,
) -> Result<(), Trap> {
// https://webassembly.github.io/bulk-memory-operations/core/exec/instructions.html#exec-table-copy
if src_index
.checked_add(len)
.map_or(true, |n| n > (*src_table).size())
|| dst_index
.checked_add(len)
.map_or(true, |m| m > (*dst_table).size())
{
return Err(Trap::TableOutOfBounds);
}
debug_assert!(
(*dst_table).element_type() == (*src_table).element_type(),
"table element type mismatch"
);
let src_range = src_index as usize..src_index as usize + len as usize;
let dst_range = dst_index as usize..dst_index as usize + len as usize;
// Check if the tables are the same as we cannot mutably borrow and also borrow the same `RefCell`
if ptr::eq(dst_table, src_table) {
(*dst_table).copy_elements_within(dst_range, src_range);
} else {
Self::copy_elements(&mut *dst_table, &*src_table, dst_range, src_range);
}
Ok(())
}
/// Return a `VMTableDefinition` for exposing the table to compiled wasm code.
pub fn vmtable(&mut self) -> VMTableDefinition {
match self {
Table::Static { data, size, .. } => VMTableDefinition {
base: data.as_mut_ptr().cast(),
current_elements: *size,
},
Table::Dynamic { elements, .. } => VMTableDefinition {
base: elements.as_mut_ptr().cast(),
current_elements: elements.len().try_into().unwrap(),
},
}
}
fn type_matches(&self, val: &TableElement) -> bool {
match (&val, self.element_type()) {
(TableElement::FuncRef(_), TableElementType::Func) => true,
(TableElement::ExternRef(_), TableElementType::Extern) => true,
_ => false,
}
}
fn elements(&self) -> &[usize] {
match self {
Table::Static { data, size, .. } => &data[..*size as usize],
Table::Dynamic { elements, .. } => &elements[..],
}
}
fn elements_mut(&mut self) -> &mut [usize] {
match self {
Table::Static { data, size, .. } => &mut data[..*size as usize],
Table::Dynamic { elements, .. } => &mut elements[..],
}
}
fn set_raw(ty: TableElementType, elem: &mut usize, val: TableElement) {
unsafe {
let old = *elem;
*elem = val.into_table_value();
// Drop the old element
let _ = TableElement::from_table_value(ty, old);
}
}
fn copy_elements(
dst_table: &mut Self,
src_table: &Self,
dst_range: Range<usize>,
src_range: Range<usize>,
) {
// This can only be used when copying between different tables
debug_assert!(!ptr::eq(dst_table, src_table));
let ty = dst_table.element_type();
match ty {
TableElementType::Func => {
// `funcref` are `Copy`, so just do a mempcy
dst_table.elements_mut()[dst_range]
.copy_from_slice(&src_table.elements()[src_range]);
}
TableElementType::Extern => {
// We need to clone each `externref`
let dst = dst_table.elements_mut();
let src = src_table.elements();
for (s, d) in src_range.zip(dst_range) {
let elem = unsafe { TableElement::clone_from_table_value(ty, src[s]) };
Self::set_raw(ty, &mut dst[d], elem);
}
}
}
}
fn copy_elements_within(&mut self, dst_range: Range<usize>, src_range: Range<usize>) {
let ty = self.element_type();
let dst = self.elements_mut();
match ty {
TableElementType::Func => {
// `funcref` are `Copy`, so just do a memmove
dst.copy_within(src_range, dst_range.start);
}
TableElementType::Extern => {
// We need to clone each `externref` while handling overlapping
// ranges
if dst_range.start <= src_range.start {
for (s, d) in src_range.zip(dst_range) {
let elem = unsafe { TableElement::clone_from_table_value(ty, dst[s]) };
Self::set_raw(ty, &mut dst[d], elem);
}
} else {
for (s, d) in src_range.rev().zip(dst_range.rev()) {
let elem = unsafe { TableElement::clone_from_table_value(ty, dst[s]) };
Self::set_raw(ty, &mut dst[d], elem);
}
}
}
}
}
}
impl Drop for Table {
fn drop(&mut self) {
let ty = self.element_type();
// funcref tables can skip this
if let TableElementType::Func = ty {
return;
}
// Properly drop any table elements stored in the table
for element in self.elements() {
drop(unsafe { TableElement::from_table_value(ty, *element) });
}
}src/libcalls.rs (line 235)
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unsafe fn table_fill(
vmctx: *mut VMContext,
table_index: u32,
dst: u32,
// NB: we don't know whether this is a `VMExternRef` or a pointer to a
// `VMCallerCheckedAnyfunc` until we look at the table's element type.
val: *mut u8,
len: u32,
) -> Result<(), Trap> {
let instance = (*vmctx).instance_mut();
let table_index = TableIndex::from_u32(table_index);
let table = &mut *instance.get_table(table_index);
match table.element_type() {
TableElementType::Func => {
let val = val as *mut VMCallerCheckedAnyfunc;
table.fill(dst, val.into(), len)
}
TableElementType::Extern => {
let val = if val.is_null() {
None
} else {
Some(VMExternRef::clone_from_raw(val))
};
table.fill(dst, val.into(), len)
}
}
}sourcepub fn size(&self) -> u32
pub fn size(&self) -> u32
Returns the number of allocated elements.
Examples found in repository?
src/table.rs (line 299)
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pub fn fill(&mut self, dst: u32, val: TableElement, len: u32) -> Result<(), Trap> {
let start = dst as usize;
let end = start
.checked_add(len as usize)
.ok_or_else(|| Trap::TableOutOfBounds)?;
if end > self.size() as usize {
return Err(Trap::TableOutOfBounds);
}
debug_assert!(self.type_matches(&val));
let ty = self.element_type();
if let Some((last, elements)) = self.elements_mut()[start..end].split_last_mut() {
for e in elements {
Self::set_raw(ty, e, val.clone());
}
Self::set_raw(ty, last, val);
}
Ok(())
}
/// Grow table by the specified amount of elements.
///
/// Returns the previous size of the table if growth is successful.
///
/// Returns `None` if table can't be grown by the specified amount of
/// elements, or if the `init_value` is the wrong kind of table element.
///
/// # Unsafety
///
/// Resizing the table can reallocate its internal elements buffer. This
/// table's instance's `VMContext` has raw pointers to the elements buffer
/// that are used by Wasm, and they need to be fixed up before we call into
/// Wasm again. Failure to do so will result in use-after-free inside Wasm.
///
/// Generally, prefer using `InstanceHandle::table_grow`, which encapsulates
/// this unsafety.
pub unsafe fn grow(
&mut self,
delta: u32,
init_value: TableElement,
store: &mut dyn Store,
) -> Result<Option<u32>, Error> {
let old_size = self.size();
let new_size = match old_size.checked_add(delta) {
Some(s) => s,
None => return Ok(None),
};
if !store.table_growing(old_size, new_size, self.maximum())? {
return Ok(None);
}
if let Some(max) = self.maximum() {
if new_size > max {
store.table_grow_failed(&format_err!("Table maximum size exceeded"));
return Ok(None);
}
}
debug_assert!(self.type_matches(&init_value));
// First resize the storage and then fill with the init value
match self {
Table::Static { size, data, .. } => {
debug_assert!(data[*size as usize..new_size as usize]
.iter()
.all(|x| *x == 0));
*size = new_size;
}
Table::Dynamic { elements, .. } => {
elements.resize(new_size as usize, 0);
}
}
self.fill(old_size, init_value, delta)
.expect("table should not be out of bounds");
Ok(Some(old_size))
}
/// Get reference to the specified element.
///
/// Returns `None` if the index is out of bounds.
pub fn get(&self, index: u32) -> Option<TableElement> {
self.elements()
.get(index as usize)
.map(|p| unsafe { TableElement::clone_from_table_value(self.element_type(), *p) })
}
/// Set reference to the specified element.
///
/// # Errors
///
/// Returns an error if `index` is out of bounds or if this table type does
/// not match the element type.
pub fn set(&mut self, index: u32, elem: TableElement) -> Result<(), ()> {
if !self.type_matches(&elem) {
return Err(());
}
let ty = self.element_type();
let e = self.elements_mut().get_mut(index as usize).ok_or(())?;
Self::set_raw(ty, e, elem);
Ok(())
}
/// Copy `len` elements from `src_table[src_index..]` into `dst_table[dst_index..]`.
///
/// # Errors
///
/// Returns an error if the range is out of bounds of either the source or
/// destination tables.
pub unsafe fn copy(
dst_table: *mut Self,
src_table: *mut Self,
dst_index: u32,
src_index: u32,
len: u32,
) -> Result<(), Trap> {
// https://webassembly.github.io/bulk-memory-operations/core/exec/instructions.html#exec-table-copy
if src_index
.checked_add(len)
.map_or(true, |n| n > (*src_table).size())
|| dst_index
.checked_add(len)
.map_or(true, |m| m > (*dst_table).size())
{
return Err(Trap::TableOutOfBounds);
}
debug_assert!(
(*dst_table).element_type() == (*src_table).element_type(),
"table element type mismatch"
);
let src_range = src_index as usize..src_index as usize + len as usize;
let dst_range = dst_index as usize..dst_index as usize + len as usize;
// Check if the tables are the same as we cannot mutably borrow and also borrow the same `RefCell`
if ptr::eq(dst_table, src_table) {
(*dst_table).copy_elements_within(dst_range, src_range);
} else {
Self::copy_elements(&mut *dst_table, &*src_table, dst_range, src_range);
}
Ok(())
}More examples
src/instance/allocator.rs (line 180)
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fn check_table_init_bounds(instance: &mut Instance, module: &Module) -> Result<()> {
match &module.table_initialization {
TableInitialization::FuncTable { segments, .. }
| TableInitialization::Segments { segments } => {
for segment in segments {
let table = unsafe { &*instance.get_table(segment.table_index) };
let start = get_table_init_start(segment, instance)?;
let start = usize::try_from(start).unwrap();
let end = start.checked_add(segment.elements.len());
match end {
Some(end) if end <= table.size() as usize => {
// Initializer is in bounds
}
_ => {
bail!("table out of bounds: elements segment does not fit")
}
}
}
}
}
Ok(())
}sourcepub fn maximum(&self) -> Option<u32>
pub fn maximum(&self) -> Option<u32>
Returns the maximum number of elements at runtime.
Returns None if the table is unbounded.
The runtime maximum may not be equal to the maximum from the table’s Wasm type when it is being constrained by an instance allocator.
Examples found in repository?
src/table.rs (line 345)
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pub unsafe fn grow(
&mut self,
delta: u32,
init_value: TableElement,
store: &mut dyn Store,
) -> Result<Option<u32>, Error> {
let old_size = self.size();
let new_size = match old_size.checked_add(delta) {
Some(s) => s,
None => return Ok(None),
};
if !store.table_growing(old_size, new_size, self.maximum())? {
return Ok(None);
}
if let Some(max) = self.maximum() {
if new_size > max {
store.table_grow_failed(&format_err!("Table maximum size exceeded"));
return Ok(None);
}
}
debug_assert!(self.type_matches(&init_value));
// First resize the storage and then fill with the init value
match self {
Table::Static { size, data, .. } => {
debug_assert!(data[*size as usize..new_size as usize]
.iter()
.all(|x| *x == 0));
*size = new_size;
}
Table::Dynamic { elements, .. } => {
elements.resize(new_size as usize, 0);
}
}
self.fill(old_size, init_value, delta)
.expect("table should not be out of bounds");
Ok(Some(old_size))
}sourcepub fn init_funcs(
&mut self,
dst: u32,
items: impl ExactSizeIterator<Item = *mut VMCallerCheckedAnyfunc>
) -> Result<(), Trap>
pub fn init_funcs(
&mut self,
dst: u32,
items: impl ExactSizeIterator<Item = *mut VMCallerCheckedAnyfunc>
) -> Result<(), Trap>
Fill table[dst..] with values from items
Returns a trap error on out-of-bounds accesses.
Examples found in repository?
src/instance.rs (lines 633-639)
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pub(crate) fn table_init_segment(
&mut self,
table_index: TableIndex,
elements: &[FuncIndex],
dst: u32,
src: u32,
len: u32,
) -> Result<(), Trap> {
// 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(Trap::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(())
}sourcepub fn fill(&mut self, dst: u32, val: TableElement, len: u32) -> Result<(), Trap>
pub fn fill(&mut self, dst: u32, val: TableElement, len: u32) -> Result<(), Trap>
Fill table[dst..dst + len] with val.
Returns a trap error on out-of-bounds accesses.
Examples found in repository?
src/libcalls.rs (line 238)
223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249
unsafe fn table_fill(
vmctx: *mut VMContext,
table_index: u32,
dst: u32,
// NB: we don't know whether this is a `VMExternRef` or a pointer to a
// `VMCallerCheckedAnyfunc` until we look at the table's element type.
val: *mut u8,
len: u32,
) -> Result<(), Trap> {
let instance = (*vmctx).instance_mut();
let table_index = TableIndex::from_u32(table_index);
let table = &mut *instance.get_table(table_index);
match table.element_type() {
TableElementType::Func => {
let val = val as *mut VMCallerCheckedAnyfunc;
table.fill(dst, val.into(), len)
}
TableElementType::Extern => {
let val = if val.is_null() {
None
} else {
Some(VMExternRef::clone_from_raw(val))
};
table.fill(dst, val.into(), len)
}
}
}More examples
src/instance.rs (line 644)
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pub(crate) fn table_init_segment(
&mut self,
table_index: TableIndex,
elements: &[FuncIndex],
dst: u32,
src: u32,
len: u32,
) -> Result<(), Trap> {
// 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(Trap::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(())
}src/table.rs (line 371)
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pub unsafe fn grow(
&mut self,
delta: u32,
init_value: TableElement,
store: &mut dyn Store,
) -> Result<Option<u32>, Error> {
let old_size = self.size();
let new_size = match old_size.checked_add(delta) {
Some(s) => s,
None => return Ok(None),
};
if !store.table_growing(old_size, new_size, self.maximum())? {
return Ok(None);
}
if let Some(max) = self.maximum() {
if new_size > max {
store.table_grow_failed(&format_err!("Table maximum size exceeded"));
return Ok(None);
}
}
debug_assert!(self.type_matches(&init_value));
// First resize the storage and then fill with the init value
match self {
Table::Static { size, data, .. } => {
debug_assert!(data[*size as usize..new_size as usize]
.iter()
.all(|x| *x == 0));
*size = new_size;
}
Table::Dynamic { elements, .. } => {
elements.resize(new_size as usize, 0);
}
}
self.fill(old_size, init_value, delta)
.expect("table should not be out of bounds");
Ok(Some(old_size))
}sourcepub unsafe fn grow(
&mut self,
delta: u32,
init_value: TableElement,
store: &mut dyn Store
) -> Result<Option<u32>, Error>
pub unsafe fn grow(
&mut self,
delta: u32,
init_value: TableElement,
store: &mut dyn Store
) -> Result<Option<u32>, Error>
Grow table by the specified amount of elements.
Returns the previous size of the table if growth is successful.
Returns None if table can’t be grown by the specified amount of
elements, or if the init_value is the wrong kind of table element.
Unsafety
Resizing the table can reallocate its internal elements buffer. This
table’s instance’s VMContext has raw pointers to the elements buffer
that are used by Wasm, and they need to be fixed up before we call into
Wasm again. Failure to do so will result in use-after-free inside Wasm.
Generally, prefer using InstanceHandle::table_grow, which encapsulates
this unsafety.
Examples found in repository?
src/instance.rs (line 469)
457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477
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
}sourcepub fn get(&self, index: u32) -> Option<TableElement>
pub fn get(&self, index: u32) -> Option<TableElement>
Get reference to the specified element.
Returns None if the index is out of bounds.
Examples found in repository?
src/libcalls.rs (line 364)
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unsafe fn table_get_lazy_init_funcref(
vmctx: *mut VMContext,
table_index: u32,
index: u32,
) -> *mut u8 {
let instance = (*vmctx).instance_mut();
let table_index = TableIndex::from_u32(table_index);
let table = instance.get_table_with_lazy_init(table_index, std::iter::once(index));
let elem = (*table)
.get(index)
.expect("table access already bounds-checked");
elem.into_ref_asserting_initialized() as *mut _
}More examples
src/instance.rs (line 822)
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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])
}sourcepub fn set(&mut self, index: u32, elem: TableElement) -> Result<(), ()>
pub fn set(&mut self, index: u32, elem: TableElement) -> Result<(), ()>
Set reference to the specified element.
Errors
Returns an error if index is out of bounds or if this table type does
not match the element type.
Examples found in repository?
src/instance.rs (line 860)
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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])
}sourcepub unsafe fn copy(
dst_table: *mut Self,
src_table: *mut Self,
dst_index: u32,
src_index: u32,
len: u32
) -> Result<(), Trap>
pub unsafe fn copy(
dst_table: *mut Self,
src_table: *mut Self,
dst_index: u32,
src_index: u32,
len: u32
) -> Result<(), Trap>
Copy len elements from src_table[src_index..] into dst_table[dst_index..].
Errors
Returns an error if the range is out of bounds of either the source or destination tables.
Examples found in repository?
src/libcalls.rs (line 270)
255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271
unsafe fn table_copy(
vmctx: *mut VMContext,
dst_table_index: u32,
src_table_index: u32,
dst: u32,
src: u32,
len: u32,
) -> Result<(), Trap> {
let dst_table_index = TableIndex::from_u32(dst_table_index);
let src_table_index = TableIndex::from_u32(src_table_index);
let instance = (*vmctx).instance_mut();
let dst_table = instance.get_table(dst_table_index);
// Lazy-initialize the whole range in the source table first.
let src_range = src..(src.checked_add(len).unwrap_or(u32::MAX));
let src_table = instance.get_table_with_lazy_init(src_table_index, src_range);
Table::copy(dst_table, src_table, dst, src, len)
}sourcepub fn vmtable(&mut self) -> VMTableDefinition
pub fn vmtable(&mut self) -> VMTableDefinition
Return a VMTableDefinition for exposing the table to compiled wasm code.
Examples found in repository?
src/instance.rs (line 473)
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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 = unsafe {
let base: *const VMSharedSignatureIndex =
*self.vmctx_plus_offset(self.offsets().vmctx_signature_ids_array());
*base.add(sig.index())
};
let (func_ptr, vmctx) = if let Some(def_index) = self.module().defined_func_index(index) {
(
self.runtime_info.function(def_index),
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<(), Trap> {
// 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<(), Trap> {
// 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(Trap::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<(), Trap> {
// 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, Trap> {
let oob = || Trap::MemoryOutOfBounds;
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<(), Trap> {
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<(), Trap> {
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<(), Trap> {
// 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,
offsets: &VMOffsets<HostPtr>,
store: StorePtr,
imports: Imports,
) {
assert!(std::ptr::eq(module, self.module().as_ref()));
*self.vmctx_plus_offset(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(offsets.vmctx_signature_ids_array()) = signatures.as_ptr();
// Initialize the built-in functions
*self.vmctx_plus_offset(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(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(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(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(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(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(offsets.vmctx_memories_begin());
let mut owned_ptr = self.vmctx_plus_offset(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();
ptr::write(ptr, def_ptr.cast_mut());
} 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);
}