wasmtime/runtime/vm.rs
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//! Runtime library support for Wasmtime.
#![deny(missing_docs)]
// See documentation in crates/wasmtime/src/runtime.rs for why this is
// selectively enabled here.
#![warn(clippy::cast_sign_loss)]
use crate::prelude::*;
use crate::store::StoreOpaque;
use alloc::sync::Arc;
use core::fmt;
use core::ops::Deref;
use core::ops::DerefMut;
use core::ptr::NonNull;
use core::sync::atomic::{AtomicUsize, Ordering};
use wasmtime_environ::{
DefinedFuncIndex, DefinedMemoryIndex, HostPtr, ModuleInternedTypeIndex, VMOffsets,
VMSharedTypeIndex,
};
mod arch;
mod async_yield;
#[cfg(feature = "component-model")]
pub mod component;
mod const_expr;
mod export;
mod gc;
mod imports;
mod instance;
mod memory;
mod mmap_vec;
mod send_sync_ptr;
mod send_sync_unsafe_cell;
mod store_box;
mod sys;
mod table;
mod traphandlers;
mod vmcontext;
#[cfg(feature = "threads")]
mod parking_spot;
#[cfg(feature = "debug-builtins")]
pub mod debug_builtins;
pub mod libcalls;
pub mod mpk;
#[cfg(feature = "debug-builtins")]
pub use wasmtime_jit_debug::gdb_jit_int::GdbJitImageRegistration;
pub use crate::runtime::vm::arch::get_stack_pointer;
pub use crate::runtime::vm::async_yield::*;
pub use crate::runtime::vm::export::*;
pub use crate::runtime::vm::gc::*;
pub use crate::runtime::vm::imports::Imports;
pub use crate::runtime::vm::instance::{
GcHeapAllocationIndex, Instance, InstanceAllocationRequest, InstanceAllocator,
InstanceAllocatorImpl, InstanceAndStore, InstanceHandle, MemoryAllocationIndex,
OnDemandInstanceAllocator, StorePtr, TableAllocationIndex,
};
#[cfg(feature = "pooling-allocator")]
pub use crate::runtime::vm::instance::{
InstanceLimits, PoolConcurrencyLimitError, PoolingInstanceAllocator,
PoolingInstanceAllocatorConfig,
};
pub use crate::runtime::vm::memory::{
Memory, RuntimeLinearMemory, RuntimeMemoryCreator, SharedMemory,
};
pub use crate::runtime::vm::mmap_vec::MmapVec;
pub use crate::runtime::vm::mpk::MpkEnabled;
pub use crate::runtime::vm::store_box::*;
#[cfg(feature = "std")]
pub use crate::runtime::vm::sys::mmap::open_file_for_mmap;
pub use crate::runtime::vm::sys::unwind::UnwindRegistration;
pub use crate::runtime::vm::table::{Table, TableElement};
pub use crate::runtime::vm::traphandlers::*;
pub use crate::runtime::vm::vmcontext::{
VMArrayCallFunction, VMArrayCallHostFuncContext, VMContext, VMFuncRef, VMFunctionBody,
VMFunctionImport, VMGlobalDefinition, VMGlobalImport, VMMemoryDefinition, VMMemoryImport,
VMOpaqueContext, VMRuntimeLimits, VMTableImport, VMWasmCallFunction, ValRaw,
};
pub use send_sync_ptr::SendSyncPtr;
pub use send_sync_unsafe_cell::SendSyncUnsafeCell;
mod module_id;
pub use module_id::CompiledModuleId;
#[cfg(feature = "signals-based-traps")]
mod byte_count;
#[cfg(feature = "signals-based-traps")]
mod cow;
#[cfg(not(feature = "signals-based-traps"))]
mod cow_disabled;
#[cfg(feature = "signals-based-traps")]
mod mmap;
cfg_if::cfg_if! {
if #[cfg(feature = "signals-based-traps")] {
pub use crate::runtime::vm::byte_count::*;
pub use crate::runtime::vm::mmap::Mmap;
pub use self::cow::{MemoryImage, MemoryImageSlot, ModuleMemoryImages};
} else {
pub use self::cow_disabled::{MemoryImage, MemoryImageSlot, ModuleMemoryImages};
}
}
/// Dynamic runtime functionality needed by this crate throughout the execution
/// of a wasm instance.
///
/// This trait is used to store a raw pointer trait object within each
/// `VMContext`. This raw pointer trait object points back to the
/// `wasmtime::Store` internally but is type-erased so this `wasmtime-runtime`
/// crate doesn't need the entire `wasmtime` crate to build.
///
/// Note that this is an extra-unsafe trait because no heed is paid to the
/// lifetime of this store or the Send/Sync-ness of this store. All of that must
/// be respected by embedders (e.g. the `wasmtime::Store` structure). The theory
/// is that `wasmtime::Store` handles all this correctly.
pub unsafe trait VMStore {
/// Get a shared borrow of this store's `StoreOpaque`.
fn store_opaque(&self) -> &StoreOpaque;
/// Get an exclusive borrow of this store's `StoreOpaque`.
fn store_opaque_mut(&mut self) -> &mut StoreOpaque;
/// Callback invoked to allow the store's resource limiter to reject a
/// memory grow operation.
fn memory_growing(
&mut self,
current: usize,
desired: usize,
maximum: Option<usize>,
) -> Result<bool, Error>;
/// Callback invoked to notify the store's resource limiter that a memory
/// grow operation has failed.
///
/// Note that this is not invoked if `memory_growing` returns an error.
fn memory_grow_failed(&mut self, error: Error) -> Result<()>;
/// Callback invoked to allow the store's resource limiter to reject a
/// table grow operation.
fn table_growing(
&mut self,
current: usize,
desired: usize,
maximum: Option<usize>,
) -> Result<bool, Error>;
/// Callback invoked to notify the store's resource limiter that a table
/// grow operation has failed.
///
/// Note that this is not invoked if `table_growing` returns an error.
fn table_grow_failed(&mut self, error: Error) -> Result<()>;
/// Callback invoked whenever fuel runs out by a wasm instance. If an error
/// is returned that's raised as a trap. Otherwise wasm execution will
/// continue as normal.
fn out_of_gas(&mut self) -> Result<(), Error>;
/// Callback invoked whenever an instance observes a new epoch
/// number. Cannot fail; cooperative epoch-based yielding is
/// completely semantically transparent. Returns the new deadline.
fn new_epoch(&mut self) -> Result<u64, Error>;
/// Callback invoked whenever an instance needs to trigger a GC.
///
/// Optionally given a GC reference that is rooted for the collection, and
/// then whose updated GC reference is returned.
///
/// Cooperative, async-yielding (if configured) is completely transparent.
///
/// If the async GC was cancelled, returns an error. This should be raised
/// as a trap to clean up Wasm execution.
fn maybe_async_gc(&mut self, root: Option<VMGcRef>) -> Result<Option<VMGcRef>>;
/// Metadata required for resources for the component model.
#[cfg(feature = "component-model")]
fn component_calls(&mut self) -> &mut component::CallContexts;
}
impl Deref for dyn VMStore + '_ {
type Target = StoreOpaque;
fn deref(&self) -> &Self::Target {
self.store_opaque()
}
}
impl DerefMut for dyn VMStore + '_ {
fn deref_mut(&mut self) -> &mut Self::Target {
self.store_opaque_mut()
}
}
/// Functionality required by this crate for a particular module. This
/// is chiefly needed for lazy initialization of various bits of
/// instance state.
///
/// When an instance is created, it holds an `Arc<dyn ModuleRuntimeInfo>`
/// so that it can get to signatures, metadata on functions, memory and
/// funcref-table images, etc. All of these things are ordinarily known
/// by the higher-level layers of Wasmtime. Specifically, the main
/// implementation of this trait is provided by
/// `wasmtime::module::ModuleInner`. Since the runtime crate sits at
/// the bottom of the dependence DAG though, we don't know or care about
/// that; we just need some implementor of this trait for each
/// allocation request.
#[derive(Clone)]
pub enum ModuleRuntimeInfo {
Module(crate::Module),
Bare(Box<BareModuleInfo>),
}
/// A barebones implementation of ModuleRuntimeInfo that is useful for
/// cases where a purpose-built environ::Module is used and a full
/// CompiledModule does not exist (for example, for tests or for the
/// default-callee instance).
#[derive(Clone)]
pub struct BareModuleInfo {
module: Arc<wasmtime_environ::Module>,
one_signature: Option<VMSharedTypeIndex>,
offsets: VMOffsets<HostPtr>,
}
impl ModuleRuntimeInfo {
pub(crate) fn bare(module: Arc<wasmtime_environ::Module>) -> Self {
ModuleRuntimeInfo::bare_maybe_imported_func(module, None)
}
pub(crate) fn bare_maybe_imported_func(
module: Arc<wasmtime_environ::Module>,
one_signature: Option<VMSharedTypeIndex>,
) -> Self {
ModuleRuntimeInfo::Bare(Box::new(BareModuleInfo {
offsets: VMOffsets::new(HostPtr, &module),
module,
one_signature,
}))
}
/// The underlying Module.
pub(crate) fn env_module(&self) -> &Arc<wasmtime_environ::Module> {
match self {
ModuleRuntimeInfo::Module(m) => m.env_module(),
ModuleRuntimeInfo::Bare(b) => &b.module,
}
}
/// Translate a module-level interned type index into an engine-level
/// interned type index.
fn engine_type_index(&self, module_index: ModuleInternedTypeIndex) -> VMSharedTypeIndex {
match self {
ModuleRuntimeInfo::Module(m) => m
.code_object()
.signatures()
.shared_type(module_index)
.expect("bad module-level interned type index"),
ModuleRuntimeInfo::Bare(_) => unreachable!(),
}
}
/// Returns the address, in memory, that the function `index` resides at.
fn function(&self, index: DefinedFuncIndex) -> NonNull<VMWasmCallFunction> {
let module = match self {
ModuleRuntimeInfo::Module(m) => m,
ModuleRuntimeInfo::Bare(_) => unreachable!(),
};
let ptr = module
.compiled_module()
.finished_function(index)
.as_ptr()
.cast::<VMWasmCallFunction>()
.cast_mut();
NonNull::new(ptr).unwrap()
}
/// Returns the address, in memory, of the trampoline that allows the given
/// defined Wasm function to be called by the array calling convention.
///
/// Returns `None` for Wasm functions which do not escape, and therefore are
/// not callable from outside the Wasm module itself.
fn array_to_wasm_trampoline(
&self,
index: DefinedFuncIndex,
) -> Option<NonNull<VMArrayCallFunction>> {
let m = match self {
ModuleRuntimeInfo::Module(m) => m,
ModuleRuntimeInfo::Bare(_) => unreachable!(),
};
let ptr = NonNull::from(m.compiled_module().array_to_wasm_trampoline(index)?);
Some(ptr.cast())
}
/// Returns the `MemoryImage` structure used for copy-on-write
/// initialization of the memory, if it's applicable.
fn memory_image(
&self,
memory: DefinedMemoryIndex,
) -> anyhow::Result<Option<&Arc<MemoryImage>>> {
match self {
ModuleRuntimeInfo::Module(m) => {
let images = m.memory_images()?;
Ok(images.and_then(|images| images.get_memory_image(memory)))
}
ModuleRuntimeInfo::Bare(_) => Ok(None),
}
}
/// A unique ID for this particular module. This can be used to
/// allow for fastpaths to optimize a "re-instantiate the same
/// module again" case.
fn unique_id(&self) -> Option<CompiledModuleId> {
match self {
ModuleRuntimeInfo::Module(m) => Some(m.id()),
ModuleRuntimeInfo::Bare(_) => None,
}
}
/// A slice pointing to all data that is referenced by this instance.
fn wasm_data(&self) -> &[u8] {
match self {
ModuleRuntimeInfo::Module(m) => m.compiled_module().code_memory().wasm_data(),
ModuleRuntimeInfo::Bare(_) => &[],
}
}
/// Returns an array, indexed by `ModuleInternedTypeIndex` of all
/// `VMSharedSignatureIndex` entries corresponding to the `SignatureIndex`.
fn type_ids(&self) -> &[VMSharedTypeIndex] {
match self {
ModuleRuntimeInfo::Module(m) => m
.code_object()
.signatures()
.as_module_map()
.values()
.as_slice(),
ModuleRuntimeInfo::Bare(b) => match &b.one_signature {
Some(s) => core::slice::from_ref(s),
None => &[],
},
}
}
/// Offset information for the current host.
pub(crate) fn offsets(&self) -> &VMOffsets<HostPtr> {
match self {
ModuleRuntimeInfo::Module(m) => m.offsets(),
ModuleRuntimeInfo::Bare(b) => &b.offsets,
}
}
}
/// Returns the host OS page size, in bytes.
#[cfg(feature = "signals-based-traps")]
pub fn host_page_size() -> usize {
static PAGE_SIZE: AtomicUsize = AtomicUsize::new(0);
return match PAGE_SIZE.load(Ordering::Relaxed) {
0 => {
let size = sys::vm::get_page_size();
assert!(size != 0);
PAGE_SIZE.store(size, Ordering::Relaxed);
size
}
n => n,
};
}
/// Is `bytes` a multiple of the host page size?
///
/// (Deprecated: consider switching to `HostAlignedByteCount`.)
#[cfg(feature = "signals-based-traps")]
pub fn usize_is_multiple_of_host_page_size(bytes: usize) -> bool {
bytes % host_page_size() == 0
}
/// Round the given byte size up to a multiple of the host OS page size.
///
/// Returns an error if rounding up overflows.
///
/// (Deprecated: consider switching to `HostAlignedByteCount`.)
#[cfg(feature = "signals-based-traps")]
pub fn round_u64_up_to_host_pages(bytes: u64) -> Result<u64> {
let page_size = u64::try_from(crate::runtime::vm::host_page_size()).err2anyhow()?;
debug_assert!(page_size.is_power_of_two());
bytes
.checked_add(page_size - 1)
.ok_or_else(|| anyhow!(
"{bytes} is too large to be rounded up to a multiple of the host page size of {page_size}"
))
.map(|val| val & !(page_size - 1))
}
/// Same as `round_u64_up_to_host_pages` but for `usize`s.
///
/// (Deprecated: consider switching to `HostAlignedByteCount`.)
#[cfg(feature = "signals-based-traps")]
pub fn round_usize_up_to_host_pages(bytes: usize) -> Result<usize> {
let bytes = u64::try_from(bytes).err2anyhow()?;
let rounded = round_u64_up_to_host_pages(bytes)?;
Ok(usize::try_from(rounded).err2anyhow()?)
}
/// Result of `Memory::atomic_wait32` and `Memory::atomic_wait64`
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum WaitResult {
/// Indicates that a `wait` completed by being awoken by a different thread.
/// This means the thread went to sleep and didn't time out.
Ok = 0,
/// Indicates that `wait` did not complete and instead returned due to the
/// value in memory not matching the expected value.
Mismatch = 1,
/// Indicates that `wait` completed with a timeout, meaning that the
/// original value matched as expected but nothing ever called `notify`.
TimedOut = 2,
}
/// Description about a fault that occurred in WebAssembly.
#[derive(Debug)]
pub struct WasmFault {
/// The size of memory, in bytes, at the time of the fault.
pub memory_size: usize,
/// The WebAssembly address at which the fault occurred.
pub wasm_address: u64,
}
impl fmt::Display for WasmFault {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(
f,
"memory fault at wasm address 0x{:x} in linear memory of size 0x{:x}",
self.wasm_address, self.memory_size,
)
}
}