b2e03ae873
Previously, @alexcrichton had mentioned that some of these assertions should be bubbled up as errors. This change re-factors two such assertions, leaving others in this file as assertions since they represent code paths that we should avoid internally (not by external users).
830 lines
32 KiB
Rust
830 lines
32 KiB
Rust
//! Memory management for linear memories.
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//!
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//! `RuntimeLinearMemory` is to WebAssembly linear memories what `Table` is to WebAssembly tables.
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use crate::mmap::Mmap;
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use crate::vmcontext::VMMemoryDefinition;
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use crate::MemoryImage;
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use crate::MemoryImageSlot;
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use crate::Store;
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use anyhow::Error;
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use anyhow::{bail, format_err, Result};
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use more_asserts::{assert_ge, assert_le};
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use std::convert::TryFrom;
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use std::sync::atomic::Ordering;
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use std::sync::{Arc, RwLock};
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use wasmtime_environ::{MemoryPlan, MemoryStyle, WASM32_MAX_PAGES, WASM64_MAX_PAGES};
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const WASM_PAGE_SIZE: usize = wasmtime_environ::WASM_PAGE_SIZE as usize;
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const WASM_PAGE_SIZE_U64: u64 = wasmtime_environ::WASM_PAGE_SIZE as u64;
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/// A memory allocator
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pub trait RuntimeMemoryCreator: Send + Sync {
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/// Create new RuntimeLinearMemory
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fn new_memory(
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&self,
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plan: &MemoryPlan,
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minimum: usize,
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maximum: Option<usize>,
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// Optionally, a memory image for CoW backing.
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memory_image: Option<&Arc<MemoryImage>>,
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) -> Result<Box<dyn RuntimeLinearMemory>>;
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}
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/// A default memory allocator used by Wasmtime
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pub struct DefaultMemoryCreator;
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impl RuntimeMemoryCreator for DefaultMemoryCreator {
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/// Create new MmapMemory
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fn new_memory(
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&self,
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plan: &MemoryPlan,
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minimum: usize,
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maximum: Option<usize>,
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memory_image: Option<&Arc<MemoryImage>>,
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) -> Result<Box<dyn RuntimeLinearMemory>> {
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Ok(Box::new(MmapMemory::new(
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plan,
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minimum,
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maximum,
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memory_image,
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)?))
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}
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}
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/// A linear memory
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pub trait RuntimeLinearMemory: Send + Sync {
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/// Returns the number of allocated bytes.
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fn byte_size(&self) -> usize;
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/// Returns the maximum number of bytes the memory can grow to.
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/// Returns `None` if the memory is unbounded.
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fn maximum_byte_size(&self) -> Option<usize>;
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/// Grows a memory by `delta_pages`.
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///
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/// This performs the necessary checks on the growth before delegating to
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/// the underlying `grow_to` implementation. A default implementation of
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/// this memory is provided here since this is assumed to be the same for
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/// most kinds of memory; one exception is shared memory, which must perform
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/// all the steps of the default implementation *plus* the required locking.
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///
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/// The `store` is used only for error reporting.
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fn grow(
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&mut self,
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delta_pages: u64,
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mut store: Option<&mut dyn Store>,
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) -> Result<Option<(usize, usize)>, Error> {
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let old_byte_size = self.byte_size();
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// Wasm spec: when growing by 0 pages, always return the current size.
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if delta_pages == 0 {
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return Ok(Some((old_byte_size, old_byte_size)));
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}
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// The largest wasm-page-aligned region of memory is possible to
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// represent in a `usize`. This will be impossible for the system to
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// actually allocate.
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let absolute_max = 0usize.wrapping_sub(WASM_PAGE_SIZE);
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// Calculate the byte size of the new allocation. Let it overflow up to
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// `usize::MAX`, then clamp it down to `absolute_max`.
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let new_byte_size = usize::try_from(delta_pages)
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.unwrap_or(usize::MAX)
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.saturating_mul(WASM_PAGE_SIZE)
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.saturating_add(old_byte_size);
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let new_byte_size = if new_byte_size > absolute_max {
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absolute_max
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} else {
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new_byte_size
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};
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let maximum = self.maximum_byte_size();
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// Store limiter gets first chance to reject memory_growing.
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if let Some(store) = &mut store {
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if !store.memory_growing(old_byte_size, new_byte_size, maximum)? {
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return Ok(None);
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}
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}
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// Never exceed maximum, even if limiter permitted it.
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if let Some(max) = maximum {
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if new_byte_size > max {
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if let Some(store) = store {
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// FIXME: shared memories may not have an associated store
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// to report the growth failure to but the error should not
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// be dropped
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// (https://github.com/bytecodealliance/wasmtime/issues/4240).
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store.memory_grow_failed(&format_err!("Memory maximum size exceeded"));
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}
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return Ok(None);
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}
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}
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match self.grow_to(new_byte_size) {
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Ok(_) => Ok(Some((old_byte_size, new_byte_size))),
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Err(e) => {
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// FIXME: shared memories may not have an associated store to
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// report the growth failure to but the error should not be
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// dropped
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// (https://github.com/bytecodealliance/wasmtime/issues/4240).
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if let Some(store) = store {
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store.memory_grow_failed(&e);
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}
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Ok(None)
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}
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}
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}
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/// Grow memory to the specified amount of bytes.
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///
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/// Returns an error if memory can't be grown by the specified amount
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/// of bytes.
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fn grow_to(&mut self, size: usize) -> Result<()>;
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/// Return a `VMMemoryDefinition` for exposing the memory to compiled wasm
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/// code.
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fn vmmemory(&mut self) -> VMMemoryDefinition;
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/// Does this memory need initialization? It may not if it already
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/// has initial contents courtesy of the `MemoryImage` passed to
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/// `RuntimeMemoryCreator::new_memory()`.
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fn needs_init(&self) -> bool;
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/// For the pooling allocator, we must be able to downcast this trait to its
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/// underlying structure.
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fn as_any_mut(&mut self) -> &mut dyn std::any::Any;
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}
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/// A linear memory instance.
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#[derive(Debug)]
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pub struct MmapMemory {
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// The underlying allocation.
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mmap: Mmap,
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// The number of bytes that are accessible in `mmap` and available for
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// reading and writing.
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//
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// This region starts at `pre_guard_size` offset from the base of `mmap`.
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accessible: usize,
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// The optional maximum accessible size, in bytes, for this linear memory.
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//
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// Note that this maximum does not factor in guard pages, so this isn't the
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// maximum size of the linear address space reservation for this memory.
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maximum: Option<usize>,
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// The amount of extra bytes to reserve whenever memory grows. This is
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// specified so that the cost of repeated growth is amortized.
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extra_to_reserve_on_growth: usize,
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// Size in bytes of extra guard pages before the start and after the end to
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// optimize loads and stores with constant offsets.
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pre_guard_size: usize,
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offset_guard_size: usize,
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// An optional CoW mapping that provides the initial content of this
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// MmapMemory, if mapped.
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memory_image: Option<MemoryImageSlot>,
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}
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impl MmapMemory {
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/// Create a new linear memory instance with specified minimum and maximum
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/// number of wasm pages.
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pub fn new(
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plan: &MemoryPlan,
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minimum: usize,
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mut maximum: Option<usize>,
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memory_image: Option<&Arc<MemoryImage>>,
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) -> Result<Self> {
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// It's a programmer error for these two configuration values to exceed
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// the host available address space, so panic if such a configuration is
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// found (mostly an issue for hypothetical 32-bit hosts).
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let offset_guard_bytes = usize::try_from(plan.offset_guard_size).unwrap();
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let pre_guard_bytes = usize::try_from(plan.pre_guard_size).unwrap();
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let (alloc_bytes, extra_to_reserve_on_growth) = match plan.style {
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// Dynamic memories start with the minimum size plus the `reserve`
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// amount specified to grow into.
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MemoryStyle::Dynamic { reserve } => (minimum, usize::try_from(reserve).unwrap()),
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// Static memories will never move in memory and consequently get
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// their entire allocation up-front with no extra room to grow into.
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// Note that the `maximum` is adjusted here to whatever the smaller
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// of the two is, the `maximum` given or the `bound` specified for
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// this memory.
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MemoryStyle::Static { bound } => {
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assert_ge!(bound, plan.memory.minimum);
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let bound_bytes =
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usize::try_from(bound.checked_mul(WASM_PAGE_SIZE_U64).unwrap()).unwrap();
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maximum = Some(bound_bytes.min(maximum.unwrap_or(usize::MAX)));
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(bound_bytes, 0)
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}
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};
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let request_bytes = pre_guard_bytes
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.checked_add(alloc_bytes)
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.and_then(|i| i.checked_add(extra_to_reserve_on_growth))
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.and_then(|i| i.checked_add(offset_guard_bytes))
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.ok_or_else(|| format_err!("cannot allocate {} with guard regions", minimum))?;
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let mut mmap = Mmap::accessible_reserved(0, request_bytes)?;
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if minimum > 0 {
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mmap.make_accessible(pre_guard_bytes, minimum)?;
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}
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// If a memory image was specified, try to create the MemoryImageSlot on
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// top of our mmap.
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let memory_image = match memory_image {
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Some(image) => {
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let base = unsafe { mmap.as_mut_ptr().add(pre_guard_bytes) };
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let mut slot = MemoryImageSlot::create(
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base.cast(),
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minimum,
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alloc_bytes + extra_to_reserve_on_growth,
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);
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slot.instantiate(minimum, Some(image))?;
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// On drop, we will unmap our mmap'd range that this slot was
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// mapped on top of, so there is no need for the slot to wipe
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// it with an anonymous mapping first.
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slot.no_clear_on_drop();
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Some(slot)
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}
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None => None,
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};
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Ok(Self {
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mmap,
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accessible: minimum,
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maximum,
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pre_guard_size: pre_guard_bytes,
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offset_guard_size: offset_guard_bytes,
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extra_to_reserve_on_growth,
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memory_image,
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})
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}
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}
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impl RuntimeLinearMemory for MmapMemory {
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fn byte_size(&self) -> usize {
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self.accessible
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}
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fn maximum_byte_size(&self) -> Option<usize> {
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self.maximum
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}
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fn grow_to(&mut self, new_size: usize) -> Result<()> {
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if new_size > self.mmap.len() - self.offset_guard_size - self.pre_guard_size {
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// If the new size of this heap exceeds the current size of the
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// allocation we have, then this must be a dynamic heap. Use
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// `new_size` to calculate a new size of an allocation, allocate it,
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// and then copy over the memory from before.
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let request_bytes = self
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.pre_guard_size
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.checked_add(new_size)
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.and_then(|s| s.checked_add(self.extra_to_reserve_on_growth))
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.and_then(|s| s.checked_add(self.offset_guard_size))
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.ok_or_else(|| format_err!("overflow calculating size of memory allocation"))?;
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let mut new_mmap = Mmap::accessible_reserved(0, request_bytes)?;
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new_mmap.make_accessible(self.pre_guard_size, new_size)?;
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new_mmap.as_mut_slice()[self.pre_guard_size..][..self.accessible]
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.copy_from_slice(&self.mmap.as_slice()[self.pre_guard_size..][..self.accessible]);
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// Now drop the MemoryImageSlot, if any. We've lost the CoW
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// advantages by explicitly copying all data, but we have
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// preserved all of its content; so we no longer need the
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// mapping. We need to do this before we (implicitly) drop the
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// `mmap` field by overwriting it below.
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drop(self.memory_image.take());
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self.mmap = new_mmap;
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} else if let Some(image) = self.memory_image.as_mut() {
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// MemoryImageSlot has its own growth mechanisms; defer to its
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// implementation.
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image.set_heap_limit(new_size)?;
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} else {
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// If the new size of this heap fits within the existing allocation
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// then all we need to do is to make the new pages accessible. This
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// can happen either for "static" heaps which always hit this case,
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// or "dynamic" heaps which have some space reserved after the
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// initial allocation to grow into before the heap is moved in
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// memory.
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assert!(new_size > self.accessible);
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self.mmap.make_accessible(
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self.pre_guard_size + self.accessible,
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new_size - self.accessible,
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)?;
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}
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self.accessible = new_size;
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Ok(())
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}
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fn vmmemory(&mut self) -> VMMemoryDefinition {
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VMMemoryDefinition {
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base: unsafe { self.mmap.as_mut_ptr().add(self.pre_guard_size) },
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current_length: self.accessible.into(),
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}
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}
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fn needs_init(&self) -> bool {
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// If we're using a CoW mapping, then no initialization
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// is needed.
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self.memory_image.is_none()
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}
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fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
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self
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}
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}
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/// A "static" memory where the lifetime of the backing memory is managed
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/// elsewhere. Currently used with the pooling allocator.
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struct StaticMemory {
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/// The memory in the host for this wasm memory. The length of this
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/// slice is the maximum size of the memory that can be grown to.
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base: &'static mut [u8],
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/// The current size, in bytes, of this memory.
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size: usize,
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/// A callback which makes portions of `base` accessible for when memory
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/// is grown. Otherwise it's expected that accesses to `base` will
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/// fault.
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make_accessible: Option<fn(*mut u8, usize) -> Result<()>>,
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/// The image management, if any, for this memory. Owned here and
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/// returned to the pooling allocator when termination occurs.
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memory_image: Option<MemoryImageSlot>,
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}
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impl StaticMemory {
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fn new(
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base: &'static mut [u8],
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initial_size: usize,
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maximum_size: Option<usize>,
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make_accessible: Option<fn(*mut u8, usize) -> Result<()>>,
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memory_image: Option<MemoryImageSlot>,
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) -> Result<Self> {
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if base.len() < initial_size {
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bail!(
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"initial memory size of {} exceeds the pooling allocator's \
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configured maximum memory size of {} bytes",
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initial_size,
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base.len(),
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);
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}
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// Only use the part of the slice that is necessary.
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let base = match maximum_size {
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Some(max) if max < base.len() => &mut base[..max],
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_ => base,
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};
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if let Some(make_accessible) = make_accessible {
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if initial_size > 0 {
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make_accessible(base.as_mut_ptr(), initial_size)?;
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}
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}
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Ok(Self {
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base,
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size: initial_size,
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make_accessible,
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memory_image,
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})
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}
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}
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impl RuntimeLinearMemory for StaticMemory {
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fn byte_size(&self) -> usize {
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self.size
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}
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fn maximum_byte_size(&self) -> Option<usize> {
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Some(self.base.len())
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}
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fn grow_to(&mut self, new_byte_size: usize) -> Result<()> {
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// Never exceed the static memory size; this check should have been made
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// prior to arriving here.
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assert!(new_byte_size <= self.base.len());
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// Actually grow the memory.
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if let Some(image) = &mut self.memory_image {
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image.set_heap_limit(new_byte_size)?;
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} else {
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let make_accessible = self
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.make_accessible
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.expect("make_accessible must be Some if this is not a CoW memory");
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// Operating system can fail to make memory accessible.
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let old_byte_size = self.byte_size();
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make_accessible(
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unsafe { self.base.as_mut_ptr().add(old_byte_size) },
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new_byte_size - old_byte_size,
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)?;
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}
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// Update our accounting of the available size.
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self.size = new_byte_size;
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Ok(())
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}
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fn vmmemory(&mut self) -> VMMemoryDefinition {
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VMMemoryDefinition {
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base: self.base.as_mut_ptr().cast(),
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current_length: self.size.into(),
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}
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}
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fn needs_init(&self) -> bool {
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if let Some(slot) = &self.memory_image {
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!slot.has_image()
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} else {
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true
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}
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}
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fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
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self
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}
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}
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/// For shared memory (and only for shared memory), this lock-version restricts
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/// access when growing the memory or checking its size. This is to conform with
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/// the [thread proposal]: "When `IsSharedArrayBuffer(...)` is true, the return
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/// value should be the result of an atomic read-modify-write of the new size to
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/// the internal `length` slot."
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///
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/// [thread proposal]:
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/// https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md#webassemblymemoryprototypegrow
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#[derive(Clone)]
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pub struct SharedMemory(Arc<RwLock<SharedMemoryInner>>);
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impl SharedMemory {
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/// Construct a new [`SharedMemory`].
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pub fn new(plan: MemoryPlan) -> Result<Self> {
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let (minimum_bytes, maximum_bytes) = Memory::limit_new(&plan, None)?;
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let mmap_memory = MmapMemory::new(&plan, minimum_bytes, maximum_bytes, None)?;
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Self::wrap(&plan, Box::new(mmap_memory), plan.memory)
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}
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/// Wrap an existing [Memory] with the locking provided by a [SharedMemory].
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pub fn wrap(
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plan: &MemoryPlan,
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mut memory: Box<dyn RuntimeLinearMemory>,
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ty: wasmtime_environ::Memory,
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) -> Result<Self> {
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if !ty.shared {
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bail!("shared memory must have a `shared` memory type");
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}
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if !matches!(plan.style, MemoryStyle::Static { .. }) {
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bail!("shared memory can only be built from a static memory allocation")
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}
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assert!(
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memory.as_any_mut().type_id() != std::any::TypeId::of::<SharedMemory>(),
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"cannot re-wrap a shared memory"
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);
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let def = LongTermVMMemoryDefinition(memory.vmmemory());
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Ok(Self(Arc::new(RwLock::new(SharedMemoryInner {
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memory: memory,
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ty,
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def,
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}))))
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}
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|
|
|
/// 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_le!(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
|
|
}
|
|
}
|
|
}
|