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//! Memory management for linear memories.
//!
//! `RuntimeLinearMemory` is to WebAssembly linear memories what `Table` is to WebAssembly tables.
use crate::mmap::Mmap;
use crate::vmcontext::VMMemoryDefinition;
use crate::MemoryImage;
use crate::MemoryImageSlot;
use crate::Store;
use anyhow::Error;
use anyhow::{bail, format_err, Result};
use std::convert::TryFrom;
use std::sync::atomic::Ordering;
use std::sync::{Arc, RwLock};
use wasmtime_environ::{MemoryPlan, MemoryStyle, WASM32_MAX_PAGES, WASM64_MAX_PAGES};
const WASM_PAGE_SIZE: usize = wasmtime_environ::WASM_PAGE_SIZE as usize;
const WASM_PAGE_SIZE_U64: u64 = wasmtime_environ::WASM_PAGE_SIZE as u64;
/// A memory allocator
pub trait RuntimeMemoryCreator: Send + Sync {
/// Create new RuntimeLinearMemory
fn new_memory(
&self,
plan: &MemoryPlan,
minimum: usize,
maximum: Option<usize>,
// Optionally, a memory image for CoW backing.
memory_image: Option<&Arc<MemoryImage>>,
) -> Result<Box<dyn RuntimeLinearMemory>>;
}
/// A default memory allocator used by Wasmtime
pub struct DefaultMemoryCreator;
impl RuntimeMemoryCreator for DefaultMemoryCreator {
/// Create new MmapMemory
fn new_memory(
&self,
plan: &MemoryPlan,
minimum: usize,
maximum: Option<usize>,
memory_image: Option<&Arc<MemoryImage>>,
) -> Result<Box<dyn RuntimeLinearMemory>> {
Ok(Box::new(MmapMemory::new(
plan,
minimum,
maximum,
memory_image,
)?))
}
}
/// A linear memory
pub trait RuntimeLinearMemory: Send + Sync {
/// Returns the number of allocated bytes.
fn byte_size(&self) -> usize;
/// Returns the maximum number of bytes the memory can grow to.
/// Returns `None` if the memory is unbounded.
fn maximum_byte_size(&self) -> Option<usize>;
/// Grows a memory by `delta_pages`.
///
/// This performs the necessary checks on the growth before delegating to
/// the underlying `grow_to` implementation. A default implementation of
/// this memory is provided here since this is assumed to be the same for
/// most kinds of memory; one exception is shared memory, which must perform
/// all the steps of the default implementation *plus* the required locking.
///
/// The `store` is used only for error reporting.
fn grow(
&mut self,
delta_pages: u64,
mut store: Option<&mut dyn Store>,
) -> Result<Option<(usize, usize)>, Error> {
let old_byte_size = self.byte_size();
// Wasm spec: when growing by 0 pages, always return the current size.
if delta_pages == 0 {
return Ok(Some((old_byte_size, old_byte_size)));
}
// The largest wasm-page-aligned region of memory is possible to
// represent in a `usize`. This will be impossible for the system to
// actually allocate.
let absolute_max = 0usize.wrapping_sub(WASM_PAGE_SIZE);
// Calculate the byte size of the new allocation. Let it overflow up to
// `usize::MAX`, then clamp it down to `absolute_max`.
let new_byte_size = usize::try_from(delta_pages)
.unwrap_or(usize::MAX)
.saturating_mul(WASM_PAGE_SIZE)
.saturating_add(old_byte_size);
let new_byte_size = if new_byte_size > absolute_max {
absolute_max
} else {
new_byte_size
};
let maximum = self.maximum_byte_size();
// Store limiter gets first chance to reject memory_growing.
if let Some(store) = &mut store {
if !store.memory_growing(old_byte_size, new_byte_size, maximum)? {
return Ok(None);
}
}
// Never exceed maximum, even if limiter permitted it.
if let Some(max) = maximum {
if new_byte_size > max {
if let Some(store) = store {
// FIXME: shared memories may not have an associated store
// to report the growth failure to but the error should not
// be dropped
// (https://github.com/bytecodealliance/wasmtime/issues/4240).
store.memory_grow_failed(&format_err!("Memory maximum size exceeded"));
}
return Ok(None);
}
}
match self.grow_to(new_byte_size) {
Ok(_) => Ok(Some((old_byte_size, new_byte_size))),
Err(e) => {
// FIXME: shared memories may not have an associated store to
// report the growth failure to but the error should not be
// dropped
// (https://github.com/bytecodealliance/wasmtime/issues/4240).
if let Some(store) = store {
store.memory_grow_failed(&e);
}
Ok(None)
}
}
}
/// Grow memory to the specified amount of bytes.
///
/// Returns an error if memory can't be grown by the specified amount
/// of bytes.
fn grow_to(&mut self, size: usize) -> Result<()>;
/// Return a `VMMemoryDefinition` for exposing the memory to compiled wasm
/// code.
fn vmmemory(&mut self) -> VMMemoryDefinition;
/// Does this memory need initialization? It may not if it already
/// has initial contents courtesy of the `MemoryImage` passed to
/// `RuntimeMemoryCreator::new_memory()`.
fn needs_init(&self) -> bool;
/// For the pooling allocator, we must be able to downcast this trait to its
/// underlying structure.
fn as_any_mut(&mut self) -> &mut dyn std::any::Any;
}
/// A linear memory instance.
#[derive(Debug)]
pub struct MmapMemory {
// The underlying allocation.
mmap: Mmap,
// The number of bytes that are accessible in `mmap` and available for
// reading and writing.
//
// This region starts at `pre_guard_size` offset from the base of `mmap`.
accessible: usize,
// The optional maximum accessible size, in bytes, for this linear memory.
//
// Note that this maximum does not factor in guard pages, so this isn't the
// maximum size of the linear address space reservation for this memory.
maximum: Option<usize>,
// The amount of extra bytes to reserve whenever memory grows. This is
// specified so that the cost of repeated growth is amortized.
extra_to_reserve_on_growth: usize,
// Size in bytes of extra guard pages before the start and after the end to
// optimize loads and stores with constant offsets.
pre_guard_size: usize,
offset_guard_size: usize,
// An optional CoW mapping that provides the initial content of this
// MmapMemory, if mapped.
memory_image: Option<MemoryImageSlot>,
}
impl MmapMemory {
/// Create a new linear memory instance with specified minimum and maximum
/// number of wasm pages.
pub fn new(
plan: &MemoryPlan,
minimum: usize,
mut maximum: Option<usize>,
memory_image: Option<&Arc<MemoryImage>>,
) -> Result<Self> {
// It's a programmer error for these two configuration values to exceed
// the host available address space, so panic if such a configuration is
// found (mostly an issue for hypothetical 32-bit hosts).
let offset_guard_bytes = usize::try_from(plan.offset_guard_size).unwrap();
let pre_guard_bytes = usize::try_from(plan.pre_guard_size).unwrap();
let (alloc_bytes, extra_to_reserve_on_growth) = match plan.style {
// Dynamic memories start with the minimum size plus the `reserve`
// amount specified to grow into.
MemoryStyle::Dynamic { reserve } => (minimum, usize::try_from(reserve).unwrap()),
// Static memories will never move in memory and consequently get
// their entire allocation up-front with no extra room to grow into.
// Note that the `maximum` is adjusted here to whatever the smaller
// of the two is, the `maximum` given or the `bound` specified for
// this memory.
MemoryStyle::Static { bound } => {
assert!(bound >= plan.memory.minimum);
let bound_bytes =
usize::try_from(bound.checked_mul(WASM_PAGE_SIZE_U64).unwrap()).unwrap();
maximum = Some(bound_bytes.min(maximum.unwrap_or(usize::MAX)));
(bound_bytes, 0)
}
};
let request_bytes = pre_guard_bytes
.checked_add(alloc_bytes)
.and_then(|i| i.checked_add(extra_to_reserve_on_growth))
.and_then(|i| i.checked_add(offset_guard_bytes))
.ok_or_else(|| format_err!("cannot allocate {} with guard regions", minimum))?;
let mut mmap = Mmap::accessible_reserved(0, request_bytes)?;
if minimum > 0 {
mmap.make_accessible(pre_guard_bytes, minimum)?;
}
// If a memory image was specified, try to create the MemoryImageSlot on
// top of our mmap.
let memory_image = match memory_image {
Some(image) => {
let base = unsafe { mmap.as_mut_ptr().add(pre_guard_bytes) };
let mut slot = MemoryImageSlot::create(
base.cast(),
minimum,
alloc_bytes + extra_to_reserve_on_growth,
);
slot.instantiate(minimum, Some(image))?;
// On drop, we will unmap our mmap'd range that this slot was
// mapped on top of, so there is no need for the slot to wipe
// it with an anonymous mapping first.
slot.no_clear_on_drop();
Some(slot)
}
None => None,
};
Ok(Self {
mmap,
accessible: minimum,
maximum,
pre_guard_size: pre_guard_bytes,
offset_guard_size: offset_guard_bytes,
extra_to_reserve_on_growth,
memory_image,
})
}
}
impl RuntimeLinearMemory for MmapMemory {
fn byte_size(&self) -> usize {
self.accessible
}
fn maximum_byte_size(&self) -> Option<usize> {
self.maximum
}
fn grow_to(&mut self, new_size: usize) -> Result<()> {
if new_size > self.mmap.len() - self.offset_guard_size - self.pre_guard_size {
// If the new size of this heap exceeds the current size of the
// allocation we have, then this must be a dynamic heap. Use
// `new_size` to calculate a new size of an allocation, allocate it,
// and then copy over the memory from before.
let request_bytes = self
.pre_guard_size
.checked_add(new_size)
.and_then(|s| s.checked_add(self.extra_to_reserve_on_growth))
.and_then(|s| s.checked_add(self.offset_guard_size))
.ok_or_else(|| format_err!("overflow calculating size of memory allocation"))?;
let mut new_mmap = Mmap::accessible_reserved(0, request_bytes)?;
new_mmap.make_accessible(self.pre_guard_size, new_size)?;
new_mmap.as_mut_slice()[self.pre_guard_size..][..self.accessible]
.copy_from_slice(&self.mmap.as_slice()[self.pre_guard_size..][..self.accessible]);
// Now drop the MemoryImageSlot, if any. We've lost the CoW
// advantages by explicitly copying all data, but we have
// preserved all of its content; so we no longer need the
// mapping. We need to do this before we (implicitly) drop the
// `mmap` field by overwriting it below.
drop(self.memory_image.take());
self.mmap = new_mmap;
} else if let Some(image) = self.memory_image.as_mut() {
// MemoryImageSlot has its own growth mechanisms; defer to its
// implementation.
image.set_heap_limit(new_size)?;
} else {
// If the new size of this heap fits within the existing allocation
// then all we need to do is to make the new pages accessible. This
// can happen either for "static" heaps which always hit this case,
// or "dynamic" heaps which have some space reserved after the
// initial allocation to grow into before the heap is moved in
// memory.
assert!(new_size > self.accessible);
self.mmap.make_accessible(
self.pre_guard_size + self.accessible,
new_size - self.accessible,
)?;
}
self.accessible = new_size;
Ok(())
}
fn vmmemory(&mut self) -> VMMemoryDefinition {
VMMemoryDefinition {
base: unsafe { self.mmap.as_mut_ptr().add(self.pre_guard_size) },
current_length: self.accessible.into(),
}
}
fn needs_init(&self) -> bool {
// If we're using a CoW mapping, then no initialization
// is needed.
self.memory_image.is_none()
}
fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
self
}
}
/// A "static" memory where the lifetime of the backing memory is managed
/// elsewhere. Currently used with the pooling allocator.
struct StaticMemory {
/// The memory in the host for this wasm memory. The length of this
/// slice is the maximum size of the memory that can be grown to.
base: &'static mut [u8],
/// The current size, in bytes, of this memory.
size: usize,
/// A callback which makes portions of `base` accessible for when memory
/// is grown. Otherwise it's expected that accesses to `base` will
/// fault.
make_accessible: Option<fn(*mut u8, usize) -> Result<()>>,
/// The image management, if any, for this memory. Owned here and
/// returned to the pooling allocator when termination occurs.
memory_image: Option<MemoryImageSlot>,
}
impl StaticMemory {
fn new(
base: &'static mut [u8],
initial_size: usize,
maximum_size: Option<usize>,
make_accessible: Option<fn(*mut u8, usize) -> Result<()>>,
memory_image: Option<MemoryImageSlot>,
) -> Result<Self> {
if base.len() < initial_size {
bail!(
"initial memory size of {} exceeds the pooling allocator's \
configured maximum memory size of {} bytes",
initial_size,
base.len(),
);
}
// Only use the part of the slice that is necessary.
let base = match maximum_size {
Some(max) if max < base.len() => &mut base[..max],
_ => base,
};
if let Some(make_accessible) = make_accessible {
if initial_size > 0 {
make_accessible(base.as_mut_ptr(), initial_size)?;
}
}
Ok(Self {
base,
size: initial_size,
make_accessible,
memory_image,
})
}
}
impl RuntimeLinearMemory for StaticMemory {
fn byte_size(&self) -> usize {
self.size
}
fn maximum_byte_size(&self) -> Option<usize> {
Some(self.base.len())
}
fn grow_to(&mut self, new_byte_size: usize) -> Result<()> {
// Never exceed the static memory size; this check should have been made
// prior to arriving here.
assert!(new_byte_size <= self.base.len());
// Actually grow the memory.
if let Some(image) = &mut self.memory_image {
image.set_heap_limit(new_byte_size)?;
} else {
let make_accessible = self
.make_accessible
.expect("make_accessible must be Some if this is not a CoW memory");
// Operating system can fail to make memory accessible.
let old_byte_size = self.byte_size();
make_accessible(
unsafe { self.base.as_mut_ptr().add(old_byte_size) },
new_byte_size - old_byte_size,
)?;
}
// Update our accounting of the available size.
self.size = new_byte_size;
Ok(())
}
fn vmmemory(&mut self) -> VMMemoryDefinition {
VMMemoryDefinition {
base: self.base.as_mut_ptr().cast(),
current_length: self.size.into(),
}
}
fn needs_init(&self) -> bool {
if let Some(slot) = &self.memory_image {
!slot.has_image()
} else {
true
}
}
fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
self
}
}
/// For shared memory (and only for shared memory), this lock-version restricts
/// access when growing the memory or checking its size. This is to conform with
/// the [thread proposal]: "When `IsSharedArrayBuffer(...)` is true, the return
/// value should be the result of an atomic read-modify-write of the new size to
/// the internal `length` slot."
///
/// [thread proposal]:
/// https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md#webassemblymemoryprototypegrow
#[derive(Clone)]
pub struct SharedMemory(Arc<RwLock<SharedMemoryInner>>);
impl SharedMemory {
/// Construct a new [`SharedMemory`].
pub fn new(plan: MemoryPlan) -> Result<Self> {
let (minimum_bytes, maximum_bytes) = Memory::limit_new(&plan, None)?;
let mmap_memory = MmapMemory::new(&plan, minimum_bytes, maximum_bytes, None)?;
Self::wrap(&plan, Box::new(mmap_memory), plan.memory)
}
/// Wrap an existing [Memory] with the locking provided by a [SharedMemory].
pub fn wrap(
plan: &MemoryPlan,
mut memory: Box<dyn RuntimeLinearMemory>,
ty: wasmtime_environ::Memory,
) -> Result<Self> {
if !ty.shared {
bail!("shared memory must have a `shared` memory type");
}
if !matches!(plan.style, MemoryStyle::Static { .. }) {
bail!("shared memory can only be built from a static memory allocation")
}
assert!(
memory.as_any_mut().type_id() != std::any::TypeId::of::<SharedMemory>(),
"cannot re-wrap a shared memory"
);
let def = LongTermVMMemoryDefinition(memory.vmmemory());
Ok(Self(Arc::new(RwLock::new(SharedMemoryInner {
memory: memory,
ty,
def,
}))))
}
/// Return the memory type for this [`SharedMemory`].
pub fn ty(&self) -> wasmtime_environ::Memory {
self.0.read().unwrap().ty
}
/// Convert this shared memory into a [`Memory`].
pub fn as_memory(self) -> Memory {
Memory(Box::new(self))
}
/// Return a mutable pointer to the shared memory's [VMMemoryDefinition].
pub fn vmmemory_ptr_mut(&mut self) -> *mut VMMemoryDefinition {
&self.0.read().unwrap().def.0 as *const _ as *mut _
}
/// Return a pointer to the shared memory's [VMMemoryDefinition].
pub fn vmmemory_ptr(&self) -> *const VMMemoryDefinition {
&self.0.read().unwrap().def.0 as *const _
}
}
struct SharedMemoryInner {
memory: Box<dyn RuntimeLinearMemory>,
ty: wasmtime_environ::Memory,
def: LongTermVMMemoryDefinition,
}
/// Shared memory needs some representation of a `VMMemoryDefinition` for
/// JIT-generated code to access. This structure owns the base pointer and
/// length to the actual memory and we share this definition across threads by:
/// - never changing the base pointer; according to the specification, shared
/// memory must be created with a known maximum size so it can be allocated
/// once and never moved
/// - carefully changing the length, using atomic accesses in both the runtime
/// and JIT-generated code.
struct LongTermVMMemoryDefinition(VMMemoryDefinition);
unsafe impl Send for LongTermVMMemoryDefinition {}
unsafe impl Sync for LongTermVMMemoryDefinition {}
/// Proxy all calls through the [`RwLock`].
impl RuntimeLinearMemory for SharedMemory {
fn byte_size(&self) -> usize {
self.0.read().unwrap().memory.byte_size()
}
fn maximum_byte_size(&self) -> Option<usize> {
self.0.read().unwrap().memory.maximum_byte_size()
}
fn grow(
&mut self,
delta_pages: u64,
store: Option<&mut dyn Store>,
) -> Result<Option<(usize, usize)>, Error> {
let mut inner = self.0.write().unwrap();
let result = inner.memory.grow(delta_pages, store)?;
if let Some((_old_size_in_bytes, new_size_in_bytes)) = result {
// Store the new size to the `VMMemoryDefinition` for JIT-generated
// code (and runtime functions) to access. No other code can be
// growing this memory due to the write lock, but code in other
// threads could have access to this shared memory and we want them
// to see the most consistent version of the `current_length`; a
// weaker consistency is possible if we accept them seeing an older,
// smaller memory size (assumption: memory only grows) but presently
// we are aiming for accuracy.
//
// Note that it could be possible to access a memory address that is
// now-valid due to changes to the page flags in `grow` above but
// beyond the `memory.size` that we are about to assign to. In these
// and similar cases, discussion in the thread proposal concluded
// that: "multiple accesses in one thread racing with another
// thread's `memory.grow` that are in-bounds only after the grow
// commits may independently succeed or trap" (see
// https://github.com/WebAssembly/threads/issues/26#issuecomment-433930711).
// In other words, some non-determinism is acceptable when using
// `memory.size` on work being done by `memory.grow`.
inner
.def
.0
.current_length
.store(new_size_in_bytes, Ordering::SeqCst);
}
Ok(result)
}
fn grow_to(&mut self, size: usize) -> Result<()> {
self.0.write().unwrap().memory.grow_to(size)
}
fn vmmemory(&mut self) -> VMMemoryDefinition {
// `vmmemory()` is used for writing the `VMMemoryDefinition` of a memory
// into its `VMContext`; this should never be possible for a shared
// memory because the only `VMMemoryDefinition` for it should be stored
// in its own `def` field.
unreachable!()
}
fn needs_init(&self) -> bool {
self.0.read().unwrap().memory.needs_init()
}
fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
self
}
}
/// Representation of a runtime wasm linear memory.
pub struct Memory(Box<dyn RuntimeLinearMemory>);
impl Memory {
/// Create a new dynamic (movable) memory instance for the specified plan.
pub fn new_dynamic(
plan: &MemoryPlan,
creator: &dyn RuntimeMemoryCreator,
store: &mut dyn Store,
memory_image: Option<&Arc<MemoryImage>>,
) -> Result<Self> {
let (minimum, maximum) = Self::limit_new(plan, Some(store))?;
let allocation = creator.new_memory(plan, minimum, maximum, memory_image)?;
let allocation = if plan.memory.shared {
Box::new(SharedMemory::wrap(plan, allocation, plan.memory)?)
} else {
allocation
};
Ok(Memory(allocation))
}
/// Create a new static (immovable) memory instance for the specified plan.
pub fn new_static(
plan: &MemoryPlan,
base: &'static mut [u8],
make_accessible: Option<fn(*mut u8, usize) -> Result<()>>,
memory_image: Option<MemoryImageSlot>,
store: &mut dyn Store,
) -> Result<Self> {
let (minimum, maximum) = Self::limit_new(plan, Some(store))?;
let pooled_memory =
StaticMemory::new(base, minimum, maximum, make_accessible, memory_image)?;
let allocation = Box::new(pooled_memory);
let allocation: Box<dyn RuntimeLinearMemory> = if plan.memory.shared {
// FIXME: since the pooling allocator owns the memory allocation
// (which is torn down with the instance), the current shared memory
// implementation will cause problems; see
// https://github.com/bytecodealliance/wasmtime/issues/4244.
todo!("using shared memory with the pooling allocator is a work in progress");
} else {
allocation
};
Ok(Memory(allocation))
}
/// Calls the `store`'s limiter to optionally prevent a memory from being allocated.
///
/// Returns the minimum size and optional maximum size of the memory, in
/// bytes.
fn limit_new(
plan: &MemoryPlan,
store: Option<&mut dyn Store>,
) -> Result<(usize, Option<usize>)> {
// Sanity-check what should already be true from wasm module validation.
let absolute_max = if plan.memory.memory64 {
WASM64_MAX_PAGES
} else {
WASM32_MAX_PAGES
};
assert!(plan.memory.minimum <= absolute_max);
assert!(plan.memory.maximum.is_none() || plan.memory.maximum.unwrap() <= absolute_max);
// This is the absolute possible maximum that the module can try to
// allocate, which is our entire address space minus a wasm page. That
// shouldn't ever actually work in terms of an allocation because
// presumably the kernel wants *something* for itself, but this is used
// to pass to the `store`'s limiter for a requested size
// to approximate the scale of the request that the wasm module is
// making. This is necessary because the limiter works on `usize` bytes
// whereas we're working with possibly-overflowing `u64` calculations
// here. To actually faithfully represent the byte requests of modules
// we'd have to represent things as `u128`, but that's kinda
// overkill for this purpose.
let absolute_max = 0usize.wrapping_sub(WASM_PAGE_SIZE);
// If the minimum memory size overflows the size of our own address
// space, then we can't satisfy this request, but defer the error to
// later so the `store` can be informed that an effective oom is
// happening.
let minimum = plan
.memory
.minimum
.checked_mul(WASM_PAGE_SIZE_U64)
.and_then(|m| usize::try_from(m).ok());
// The plan stores the maximum size in units of wasm pages, but we
// use units of bytes. Unlike for the `minimum` size we silently clamp
// the effective maximum size to `absolute_max` above if the maximum is
// too large. This should be ok since as a wasm runtime we get to
// arbitrarily decide the actual maximum size of memory, regardless of
// what's actually listed on the memory itself.
let mut maximum = plan.memory.maximum.map(|max| {
usize::try_from(max)
.ok()
.and_then(|m| m.checked_mul(WASM_PAGE_SIZE))
.unwrap_or(absolute_max)
});
// If this is a 32-bit memory and no maximum is otherwise listed then we
// need to still specify a maximum size of 4GB. If the host platform is
// 32-bit then there's no need to limit the maximum this way since no
// allocation of 4GB can succeed, but for 64-bit platforms this is
// required to limit memories to 4GB.
if !plan.memory.memory64 && maximum.is_none() {
maximum = usize::try_from(1u64 << 32).ok();
}
// Inform the store's limiter what's about to happen. This will let the
// limiter reject anything if necessary, and this also guarantees that
// we should call the limiter for all requested memories, even if our
// `minimum` calculation overflowed. This means that the `minimum` we're
// informing the limiter is lossy and may not be 100% accurate, but for
// now the expected uses of limiter means that's ok.
if let Some(store) = store {
// We ignore the store limits for shared memories since they are
// technically not created within a store (though, trickily, they
// may be associated with one in order to get a `vmctx`).
if !plan.memory.shared {
if !store.memory_growing(0, minimum.unwrap_or(absolute_max), maximum)? {
bail!(
"memory minimum size of {} pages exceeds memory limits",
plan.memory.minimum
);
}
}
}
// At this point we need to actually handle overflows, so bail out with
// an error if we made it this far.
let minimum = minimum.ok_or_else(|| {
format_err!(
"memory minimum size of {} pages exceeds memory limits",
plan.memory.minimum
)
})?;
Ok((minimum, maximum))
}
/// Returns the number of allocated wasm pages.
pub fn byte_size(&self) -> usize {
self.0.byte_size()
}
/// Returns the maximum number of pages the memory can grow to at runtime.
///
/// Returns `None` if the memory is unbounded.
///
/// The runtime maximum may not be equal to the maximum from the linear memory's
/// Wasm type when it is being constrained by an instance allocator.
pub fn maximum_byte_size(&self) -> Option<usize> {
self.0.maximum_byte_size()
}
/// Returns whether or not this memory needs initialization. It
/// may not if it already has initial content thanks to a CoW
/// mechanism.
pub(crate) fn needs_init(&self) -> bool {
self.0.needs_init()
}
/// Grow memory by the specified amount of wasm pages.
///
/// Returns `None` if memory can't be grown by the specified amount
/// of wasm pages. Returns `Some` with the old size of memory, in bytes, on
/// successful growth.
///
/// # Safety
///
/// Resizing the memory can reallocate the memory buffer for dynamic memories.
/// An instance's `VMContext` may have pointers to the memory's base and will
/// need to be fixed up after growing the memory.
///
/// Generally, prefer using `InstanceHandle::memory_grow`, which encapsulates
/// this unsafety.
///
/// Ensure that the provided Store is not used to get access any Memory
/// which lives inside it.
pub unsafe fn grow(
&mut self,
delta_pages: u64,
store: Option<&mut dyn Store>,
) -> Result<Option<usize>, Error> {
self.0
.grow(delta_pages, store)
.map(|opt| opt.map(|(old, _new)| old))
}
/// Return a `VMMemoryDefinition` for exposing the memory to compiled wasm code.
pub fn vmmemory(&mut self) -> VMMemoryDefinition {
self.0.vmmemory()
}
/// Check if the inner implementation of [`Memory`] is a memory created with
/// [`Memory::new_static()`].
#[cfg(feature = "pooling-allocator")]
pub fn is_static(&mut self) -> bool {
let as_any = self.0.as_any_mut();
as_any.downcast_ref::<StaticMemory>().is_some()
}
/// Consume the memory, returning its [`MemoryImageSlot`] if any is present.
/// The image should only be present for a subset of memories created with
/// [`Memory::new_static()`].
#[cfg(feature = "pooling-allocator")]
pub fn unwrap_static_image(mut self) -> Option<MemoryImageSlot> {
let as_any = self.0.as_any_mut();
if let Some(m) = as_any.downcast_mut::<StaticMemory>() {
std::mem::take(&mut m.memory_image)
} else {
None
}
}
/// If the [Memory] is a [SharedMemory], unwrap it and return a clone to
/// that shared memory.
pub fn as_shared_memory(&mut self) -> Option<SharedMemory> {
let as_any = self.0.as_any_mut();
if let Some(m) = as_any.downcast_mut::<SharedMemory>() {
Some(m.clone())
} else {
None
}
}
}