be85242a3f
* Consolidate trap/frame information This commit removes `TrapRegistry` in favor of consolidating this information in the `FRAME_INFO` we already have in the `wasmtime` crate. This allows us to keep information generally in one place and have one canonical location for "map this PC to some original wasm stuff". The intent for this is to next update with enough information to go from a program counter to a position in the original wasm file. * Expose module offset information in `FrameInfo` This commit implements functionality for `FrameInfo`, the wasm stack trace of a `Trap`, to return the module/function offset. This allows knowing the precise wasm location of each stack frame, instead of only the main trap itself. The intention here is to provide more visibility into the wasm source when something traps, so you know precisely where calls were and where traps were, in order to assist in debugging. Eventually we might use this information for mapping back to native source languages as well (given sufficient debug information). This change makes a previously-optional artifact of compilation always computed on the cranelift side of things. This `ModuleAddressMap` is then propagated to the same store of information other frame information is stored within. This also removes the need for passing a `SourceLoc` with wasm traps or to wasm trap creation, since the backtrace's wasm frames will be able to infer their own `SourceLoc` from the relevant program counters.
893 lines
34 KiB
Rust
893 lines
34 KiB
Rust
use crate::trampoline::{generate_global_export, generate_memory_export, generate_table_export};
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use crate::values::{from_checked_anyfunc, into_checked_anyfunc, Val};
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use crate::Mutability;
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use crate::{ExternType, GlobalType, MemoryType, TableType, ValType};
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use crate::{Func, Store, Trap};
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use anyhow::{anyhow, bail, Result};
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use std::slice;
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use wasmtime_environ::wasm;
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use wasmtime_runtime::{self as runtime, InstanceHandle};
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// Externals
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/// An external item to a WebAssembly module, or a list of what can possibly be
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/// exported from a wasm module.
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///
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/// This is both returned from [`Instance::exports`](crate::Instance::exports)
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/// as well as required by [`Instance::new`](crate::Instance::new). In other
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/// words, this is the type of extracted values from an instantiated module, and
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/// it's also used to provide imported values when instantiating a module.
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#[derive(Clone)]
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pub enum Extern {
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/// A WebAssembly `func` which can be called.
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Func(Func),
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/// A WebAssembly `global` which acts like a `Cell<T>` of sorts, supporting
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/// `get` and `set` operations.
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Global(Global),
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/// A WebAssembly `table` which is an array of `Val` types.
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Table(Table),
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/// A WebAssembly linear memory.
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Memory(Memory),
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}
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impl Extern {
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/// Returns the underlying `Func`, if this external is a function.
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///
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/// Returns `None` if this is not a function.
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pub fn func(&self) -> Option<&Func> {
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match self {
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Extern::Func(func) => Some(func),
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_ => None,
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}
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}
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/// Returns the underlying `Global`, if this external is a global.
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///
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/// Returns `None` if this is not a global.
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pub fn global(&self) -> Option<&Global> {
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match self {
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Extern::Global(global) => Some(global),
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_ => None,
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}
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}
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/// Returns the underlying `Table`, if this external is a table.
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///
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/// Returns `None` if this is not a table.
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pub fn table(&self) -> Option<&Table> {
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match self {
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Extern::Table(table) => Some(table),
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_ => None,
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}
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}
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/// Returns the underlying `Memory`, if this external is a memory.
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///
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/// Returns `None` if this is not a memory.
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pub fn memory(&self) -> Option<&Memory> {
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match self {
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Extern::Memory(memory) => Some(memory),
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_ => None,
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}
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}
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/// Returns the type associated with this `Extern`.
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pub fn ty(&self) -> ExternType {
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match self {
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Extern::Func(ft) => ExternType::Func(ft.ty().clone()),
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Extern::Memory(ft) => ExternType::Memory(ft.ty().clone()),
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Extern::Table(tt) => ExternType::Table(tt.ty().clone()),
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Extern::Global(gt) => ExternType::Global(gt.ty().clone()),
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}
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}
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pub(crate) fn get_wasmtime_export(&self) -> wasmtime_runtime::Export {
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match self {
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Extern::Func(f) => f.wasmtime_function().clone().into(),
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Extern::Global(g) => g.wasmtime_export.clone().into(),
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Extern::Memory(m) => m.wasmtime_export.clone().into(),
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Extern::Table(t) => t.wasmtime_export.clone().into(),
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}
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}
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pub(crate) fn from_wasmtime_export(
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store: &Store,
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instance_handle: InstanceHandle,
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export: wasmtime_runtime::Export,
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) -> Extern {
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match export {
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wasmtime_runtime::Export::Function(f) => {
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Extern::Func(Func::from_wasmtime_function(f, store, instance_handle))
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}
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wasmtime_runtime::Export::Memory(m) => {
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Extern::Memory(Memory::from_wasmtime_memory(m, store, instance_handle))
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}
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wasmtime_runtime::Export::Global(g) => {
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Extern::Global(Global::from_wasmtime_global(g, store, instance_handle))
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}
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wasmtime_runtime::Export::Table(t) => {
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Extern::Table(Table::from_wasmtime_table(t, store, instance_handle))
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}
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}
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}
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pub(crate) fn comes_from_same_store(&self, store: &Store) -> bool {
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let my_store = match self {
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Extern::Func(f) => f.store(),
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Extern::Global(g) => &g.store,
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Extern::Memory(m) => &m.store,
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Extern::Table(t) => &t.store,
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};
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Store::same(my_store, store)
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}
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}
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impl From<Func> for Extern {
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fn from(r: Func) -> Self {
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Extern::Func(r)
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}
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}
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impl From<Global> for Extern {
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fn from(r: Global) -> Self {
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Extern::Global(r)
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}
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}
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impl From<Memory> for Extern {
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fn from(r: Memory) -> Self {
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Extern::Memory(r)
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}
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}
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impl From<Table> for Extern {
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fn from(r: Table) -> Self {
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Extern::Table(r)
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}
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}
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/// A WebAssembly `global` value which can be read and written to.
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///
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/// A `global` in WebAssembly is sort of like a global variable within an
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/// [`Instance`](crate::Instance). The `global.get` and `global.set`
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/// instructions will modify and read global values in a wasm module. Globals
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/// can either be imported or exported from wasm modules.
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///
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/// If you're familiar with Rust already you can think of a `Global` as a sort
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/// of `Rc<Cell<Val>>`, more or less.
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///
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/// # `Global` and `Clone`
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///
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/// Globals are internally reference counted so you can `clone` a `Global`. The
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/// cloning process only performs a shallow clone, so two cloned `Global`
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/// instances are equivalent in their functionality.
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#[derive(Clone)]
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pub struct Global {
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store: Store,
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ty: GlobalType,
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wasmtime_export: wasmtime_runtime::ExportGlobal,
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wasmtime_handle: InstanceHandle,
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}
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impl Global {
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/// Creates a new WebAssembly `global` value with the provide type `ty` and
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/// initial value `val`.
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///
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/// The `store` argument provided is used as a general global cache for
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/// information, and otherwise the `ty` and `val` arguments are used to
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/// initialize the global.
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///
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/// # Errors
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///
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/// Returns an error if the `ty` provided does not match the type of the
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/// value `val`.
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pub fn new(store: &Store, ty: GlobalType, val: Val) -> Result<Global> {
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if !val.comes_from_same_store(store) {
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bail!("cross-`Store` globals are not supported");
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}
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if val.ty() != *ty.content() {
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bail!("value provided does not match the type of this global");
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}
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let (wasmtime_handle, wasmtime_export) = generate_global_export(store, &ty, val)?;
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Ok(Global {
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store: store.clone(),
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ty,
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wasmtime_export,
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wasmtime_handle,
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})
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}
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/// Returns the underlying type of this `global`.
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pub fn ty(&self) -> &GlobalType {
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&self.ty
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}
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/// Returns the current [`Val`] of this global.
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pub fn get(&self) -> Val {
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unsafe {
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let definition = &mut *self.wasmtime_export.definition;
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match self.ty().content() {
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ValType::I32 => Val::from(*definition.as_i32()),
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ValType::I64 => Val::from(*definition.as_i64()),
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ValType::F32 => Val::F32(*definition.as_u32()),
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ValType::F64 => Val::F64(*definition.as_u64()),
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_ => unimplemented!("Global::get for {:?}", self.ty().content()),
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}
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}
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}
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/// Attempts to set the current value of this global to [`Val`].
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///
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/// # Errors
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///
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/// Returns an error if this global has a different type than `Val`, or if
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/// it's not a mutable global.
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pub fn set(&self, val: Val) -> Result<()> {
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if self.ty().mutability() != Mutability::Var {
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bail!("immutable global cannot be set");
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}
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if val.ty() != *self.ty().content() {
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bail!(
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"global of type {:?} cannot be set to {:?}",
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self.ty().content(),
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val.ty()
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);
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}
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if !val.comes_from_same_store(&self.store) {
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bail!("cross-`Store` values are not supported");
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}
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unsafe {
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let definition = &mut *self.wasmtime_export.definition;
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match val {
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Val::I32(i) => *definition.as_i32_mut() = i,
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Val::I64(i) => *definition.as_i64_mut() = i,
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Val::F32(f) => *definition.as_u32_mut() = f,
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Val::F64(f) => *definition.as_u64_mut() = f,
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_ => unimplemented!("Global::set for {:?}", val.ty()),
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}
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}
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Ok(())
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}
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pub(crate) fn from_wasmtime_global(
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wasmtime_export: wasmtime_runtime::ExportGlobal,
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store: &Store,
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wasmtime_handle: InstanceHandle,
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) -> Global {
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// The original export is coming from wasmtime_runtime itself we should
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// support all the types coming out of it, so assert such here.
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let ty = GlobalType::from_wasmtime_global(&wasmtime_export.global)
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.expect("core wasm global type should be supported");
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Global {
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store: store.clone(),
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ty: ty,
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wasmtime_export,
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wasmtime_handle,
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}
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}
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}
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/// A WebAssembly `table`, or an array of values.
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///
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/// Like [`Memory`] a table is an indexed array of values, but unlike [`Memory`]
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/// it's an array of WebAssembly values rather than bytes. One of the most
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/// common usages of a table is a function table for wasm modules, where each
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/// element has the `Func` type.
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///
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/// Tables, like globals, are not threadsafe and can only be used on one thread.
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/// Tables can be grown in size and each element can be read/written.
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///
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/// # `Table` and `Clone`
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///
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/// Tables are internally reference counted so you can `clone` a `Table`. The
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/// cloning process only performs a shallow clone, so two cloned `Table`
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/// instances are equivalent in their functionality.
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#[derive(Clone)]
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pub struct Table {
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store: Store,
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ty: TableType,
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wasmtime_handle: InstanceHandle,
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wasmtime_export: wasmtime_runtime::ExportTable,
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}
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fn set_table_item(
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handle: &InstanceHandle,
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table_index: wasm::DefinedTableIndex,
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item_index: u32,
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item: wasmtime_runtime::VMCallerCheckedAnyfunc,
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) -> Result<()> {
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handle
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.table_set(table_index, item_index, item)
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.map_err(|()| anyhow!("table element index out of bounds"))
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}
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impl Table {
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/// Creates a new `Table` with the given parameters.
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///
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/// * `store` - a global cache to store information in
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/// * `ty` - the type of this table, containing both the element type as
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/// well as the initial size and maximum size, if any.
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/// * `init` - the initial value to fill all table entries with, if the
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/// table starts with an initial size.
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///
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/// # Errors
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///
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/// Returns an error if `init` does not match the element type of the table.
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pub fn new(store: &Store, ty: TableType, init: Val) -> Result<Table> {
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let item = into_checked_anyfunc(init, store)?;
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let (wasmtime_handle, wasmtime_export) = generate_table_export(store, &ty)?;
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// Initialize entries with the init value.
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let definition = unsafe { &*wasmtime_export.definition };
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let index = wasmtime_handle.table_index(definition);
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for i in 0..definition.current_elements {
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set_table_item(&wasmtime_handle, index, i, item.clone())?;
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}
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Ok(Table {
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store: store.clone(),
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ty,
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wasmtime_handle,
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wasmtime_export,
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})
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}
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/// Returns the underlying type of this table, including its element type as
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/// well as the maximum/minimum lower bounds.
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pub fn ty(&self) -> &TableType {
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&self.ty
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}
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fn wasmtime_table_index(&self) -> wasm::DefinedTableIndex {
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unsafe {
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self.wasmtime_handle
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.table_index(&*self.wasmtime_export.definition)
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}
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}
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/// Returns the table element value at `index`.
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///
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/// Returns `None` if `index` is out of bounds.
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pub fn get(&self, index: u32) -> Option<Val> {
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let table_index = self.wasmtime_table_index();
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let item = self.wasmtime_handle.table_get(table_index, index)?;
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Some(from_checked_anyfunc(item, &self.store))
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}
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/// Writes the `val` provided into `index` within this table.
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///
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/// # Errors
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///
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/// Returns an error if `index` is out of bounds or if `val` does not have
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/// the right type to be stored in this table.
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pub fn set(&self, index: u32, val: Val) -> Result<()> {
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let table_index = self.wasmtime_table_index();
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let item = into_checked_anyfunc(val, &self.store)?;
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set_table_item(&self.wasmtime_handle, table_index, index, item)
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}
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/// Returns the current size of this table.
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pub fn size(&self) -> u32 {
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unsafe { (&*self.wasmtime_export.definition).current_elements }
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}
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/// Grows the size of this table by `delta` more elements, initialization
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/// all new elements to `init`.
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///
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/// # Errors
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///
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/// Returns an error if the table cannot be grown by `delta`, for example
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/// if it would cause the table to exceed its maximum size. Also returns an
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/// error if `init` is not of the right type.
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pub fn grow(&self, delta: u32, init: Val) -> Result<u32> {
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let index = self.wasmtime_table_index();
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let item = into_checked_anyfunc(init, &self.store)?;
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if let Some(len) = self.wasmtime_handle.clone().table_grow(index, delta) {
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let mut wasmtime_handle = self.wasmtime_handle.clone();
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for i in 0..delta {
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let i = len - (delta - i);
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set_table_item(&mut wasmtime_handle, index, i, item.clone())?;
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}
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Ok(len)
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} else {
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bail!("failed to grow table by `{}`", delta)
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}
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}
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/// Copy `len` elements from `src_table[src_index..]` into
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/// `dst_table[dst_index..]`.
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///
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/// # Errors
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///
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/// Returns an error if the range is out of bounds of either the source or
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/// destination tables.
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pub fn copy(
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dst_table: &Table,
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dst_index: u32,
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src_table: &Table,
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src_index: u32,
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len: u32,
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) -> Result<()> {
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if !Store::same(&dst_table.store, &src_table.store) {
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bail!("cross-`Store` table copies are not supported");
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}
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// NB: We must use the `dst_table`'s `wasmtime_handle` for the
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// `dst_table_index` and vice versa for `src_table` since each table can
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// come from different modules.
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let dst_table_index = dst_table.wasmtime_table_index();
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let dst_table = dst_table.wasmtime_handle.get_defined_table(dst_table_index);
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let src_table_index = src_table.wasmtime_table_index();
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let src_table = src_table.wasmtime_handle.get_defined_table(src_table_index);
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runtime::Table::copy(dst_table, src_table, dst_index, src_index, len)
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.map_err(Trap::from_jit)?;
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Ok(())
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}
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pub(crate) fn from_wasmtime_table(
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wasmtime_export: wasmtime_runtime::ExportTable,
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store: &Store,
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wasmtime_handle: wasmtime_runtime::InstanceHandle,
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) -> Table {
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let ty = TableType::from_wasmtime_table(&wasmtime_export.table.table);
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Table {
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store: store.clone(),
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ty,
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wasmtime_handle,
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wasmtime_export,
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}
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}
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}
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/// A WebAssembly linear memory.
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///
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/// WebAssembly memories represent a contiguous array of bytes that have a size
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/// that is always a multiple of the WebAssembly page size, currently 64
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/// kilobytes.
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///
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|
/// WebAssembly memory is used for global data, statics in C/C++/Rust, shadow
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|
/// stack memory, etc. Accessing wasm memory is generally quite fast!
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///
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|
/// # `Memory` and `Clone`
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|
///
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|
/// Memories are internally reference counted so you can `clone` a `Memory`. The
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/// cloning process only performs a shallow clone, so two cloned `Memory`
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|
/// instances are equivalent in their functionality.
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///
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/// # `Memory` and threads
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///
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/// It is intended that `Memory` is safe to share between threads. At this time
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/// this is not implemented in `wasmtime`, however. This is planned to be
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/// implemented though!
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///
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/// # `Memory` and Safety
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///
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|
/// Linear memory is a lynchpin of safety for WebAssembly, but it turns out
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/// there are very few ways to safely inspect the contents of a memory from the
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|
/// host (Rust). This is because memory safety is quite tricky when working with
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/// a `Memory` and we're still working out the best idioms to encapsulate
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|
/// everything safely where it's efficient and ergonomic. This section of
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|
/// documentation, however, is intended to help educate a bit what is and isn't
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|
/// safe when working with `Memory`.
|
|
///
|
|
/// For safety purposes you can think of a `Memory` as a glorified
|
|
/// `Rc<UnsafeCell<Vec<u8>>>`. There are a few consequences of this
|
|
/// interpretation:
|
|
///
|
|
/// * At any time someone else may have access to the memory (hence the `Rc`).
|
|
/// This could be a wasm instance, other host code, or a set of wasm instances
|
|
/// which all reference a `Memory`. When in doubt assume someone else has a
|
|
/// handle to your `Memory`.
|
|
///
|
|
/// * At any time, memory can be read from or written to (hence the
|
|
/// `UnsafeCell`). Anyone with a handle to a wasm memory can read/write to it.
|
|
/// Primarily other instances can execute the `load` and `store` family of
|
|
/// instructions, as well as any other which modifies or reads memory.
|
|
///
|
|
/// * At any time memory may grow (hence the `Vec<..>`). Growth may relocate the
|
|
/// base memory pointer (similar to how `vec.push(...)` can change the result
|
|
/// of `.as_ptr()`)
|
|
///
|
|
/// So given that we're working roughly with `Rc<UnsafeCell<Vec<u8>>>` that's a
|
|
/// lot to keep in mind! It's hopefully though sort of setting the stage as to
|
|
/// what you can safely do with memories.
|
|
///
|
|
/// Let's run through a few safe examples first of how you can use a `Memory`.
|
|
///
|
|
/// ```rust
|
|
/// use wasmtime::Memory;
|
|
///
|
|
/// fn safe_examples(mem: &Memory) {
|
|
/// // Just like wasm, it's safe to read memory almost at any time. The
|
|
/// // gotcha here is that we need to be sure to load from the correct base
|
|
/// // pointer and perform the bounds check correctly. So long as this is
|
|
/// // all self contained here (e.g. not arbitrary code in the middle) we're
|
|
/// // good to go.
|
|
/// let byte = unsafe { mem.data_unchecked()[0x123] };
|
|
///
|
|
/// // Short-lived borrows of memory are safe, but they must be scoped and
|
|
/// // not have code which modifies/etc `Memory` while the borrow is active.
|
|
/// // For example if you want to read a string from memory it is safe to do
|
|
/// // so:
|
|
/// let string_base = 0xdead;
|
|
/// let string_len = 0xbeef;
|
|
/// let string = unsafe {
|
|
/// let bytes = &mem.data_unchecked()[string_base..][..string_len];
|
|
/// match std::str::from_utf8(bytes) {
|
|
/// Ok(s) => s.to_string(), // copy out of wasm memory
|
|
/// Err(_) => panic!("not valid utf-8"),
|
|
/// }
|
|
/// };
|
|
///
|
|
/// // Additionally like wasm you can write to memory at any point in time,
|
|
/// // again making sure that after you get the unchecked slice you don't
|
|
/// // execute code which could read/write/modify `Memory`:
|
|
/// unsafe {
|
|
/// mem.data_unchecked_mut()[0x123] = 3;
|
|
/// }
|
|
///
|
|
/// // When working with *borrows* that point directly into wasm memory you
|
|
/// // need to be extremely careful. Any functionality that operates on a
|
|
/// // borrow into wasm memory needs to be thoroughly audited to effectively
|
|
/// // not touch the `Memory` at all
|
|
/// let data_base = 0xfeed;
|
|
/// let data_len = 0xface;
|
|
/// unsafe {
|
|
/// let data = &mem.data_unchecked()[data_base..][..data_len];
|
|
/// host_function_that_doesnt_touch_memory(data);
|
|
///
|
|
/// // effectively the same rules apply to mutable borrows
|
|
/// let data_mut = &mut mem.data_unchecked_mut()[data_base..][..data_len];
|
|
/// host_function_that_doesnt_touch_memory(data);
|
|
/// }
|
|
/// }
|
|
/// # fn host_function_that_doesnt_touch_memory(_: &[u8]){}
|
|
/// ```
|
|
///
|
|
/// It's worth also, however, covering some examples of **incorrect**,
|
|
/// **unsafe** usages of `Memory`. Do not do these things!
|
|
///
|
|
/// ```rust
|
|
/// # use anyhow::Result;
|
|
/// use wasmtime::Memory;
|
|
///
|
|
/// // NOTE: All code in this function is not safe to execute and may cause
|
|
/// // segfaults/undefined behavior at runtime. Do not copy/paste these examples
|
|
/// // into production code!
|
|
/// unsafe fn unsafe_examples(mem: &Memory) -> Result<()> {
|
|
/// // First and foremost, any borrow can be invalidated at any time via the
|
|
/// // `Memory::grow` function. This can relocate memory which causes any
|
|
/// // previous pointer to be possibly invalid now.
|
|
/// let pointer: &u8 = &mem.data_unchecked()[0x100];
|
|
/// mem.grow(1)?; // invalidates `pointer`!
|
|
/// // println!("{}", *pointer); // FATAL: use-after-free
|
|
///
|
|
/// // Note that the use-after-free also applies to slices, whether they're
|
|
/// // slices of bytes or strings.
|
|
/// let slice: &[u8] = &mem.data_unchecked()[0x100..0x102];
|
|
/// mem.grow(1)?; // invalidates `slice`!
|
|
/// // println!("{:?}", slice); // FATAL: use-after-free
|
|
///
|
|
/// // Due to the reference-counted nature of `Memory` note that literal
|
|
/// // calls to `Memory::grow` are not sufficient to audit for. You'll need
|
|
/// // to be careful that any mutation of `Memory` doesn't happen while
|
|
/// // you're holding an active borrow.
|
|
/// let slice: &[u8] = &mem.data_unchecked()[0x100..0x102];
|
|
/// some_other_function(); // may invalidate `slice` through another `mem` reference
|
|
/// // println!("{:?}", slice); // FATAL: maybe a use-after-free
|
|
///
|
|
/// // An especially subtle aspect of accessing a wasm instance's memory is
|
|
/// // that you need to be extremely careful about aliasing. Anyone at any
|
|
/// // time can call `data_unchecked()` or `data_unchecked_mut()`, which
|
|
/// // means you can easily have aliasing mutable references:
|
|
/// let ref1: &u8 = &mem.data_unchecked()[0x100];
|
|
/// let ref2: &mut u8 = &mut mem.data_unchecked_mut()[0x100];
|
|
/// // *ref2 = *ref1; // FATAL: violates Rust's aliasing rules
|
|
///
|
|
/// // Note that aliasing applies to strings as well, for example this is
|
|
/// // not valid because the slices overlap.
|
|
/// let slice1: &mut [u8] = &mut mem.data_unchecked_mut()[0x100..][..3];
|
|
/// let slice2: &mut [u8] = &mut mem.data_unchecked_mut()[0x102..][..4];
|
|
/// // println!("{:?} {:?}", slice1, slice2); // FATAL: aliasing mutable pointers
|
|
///
|
|
/// Ok(())
|
|
/// }
|
|
/// # fn some_other_function() {}
|
|
/// ```
|
|
///
|
|
/// Overall there's some general rules of thumb when working with `Memory` and
|
|
/// getting raw pointers inside of it:
|
|
///
|
|
/// * If you never have a "long lived" pointer into memory, you're likely in the
|
|
/// clear. Care still needs to be taken in threaded scenarios or when/where
|
|
/// data is read, but you'll be shielded from many classes of issues.
|
|
/// * Long-lived pointers must always respect Rust'a aliasing rules. It's ok for
|
|
/// shared borrows to overlap with each other, but mutable borrows must
|
|
/// overlap with nothing.
|
|
/// * Long-lived pointers are only valid if `Memory` isn't used in an unsafe way
|
|
/// while the pointer is valid. This includes both aliasing and growth.
|
|
///
|
|
/// At this point it's worth reiterating again that working with `Memory` is
|
|
/// pretty tricky and that's not great! Proposals such as [interface types] are
|
|
/// intended to prevent wasm modules from even needing to import/export memory
|
|
/// in the first place, which obviates the need for all of these safety caveats!
|
|
/// Additionally over time we're still working out the best idioms to expose in
|
|
/// `wasmtime`, so if you've got ideas or questions please feel free to [open an
|
|
/// issue]!
|
|
///
|
|
/// ## `Memory` Safety and Threads
|
|
///
|
|
/// Currently the `wasmtime` crate does not implement the wasm threads proposal,
|
|
/// but it is planned to do so. It's additionally worthwhile discussing how this
|
|
/// affects memory safety and what was previously just discussed as well.
|
|
///
|
|
/// Once threads are added into the mix, all of the above rules still apply.
|
|
/// There's an additional, rule, however, that all reads and writes can
|
|
/// happen *concurrently*. This effectively means that long-lived borrows into
|
|
/// wasm memory are virtually never safe to have.
|
|
///
|
|
/// Mutable pointers are fundamentally unsafe to have in a concurrent scenario
|
|
/// in the face of arbitrary wasm code. Only if you dynamically know for sure
|
|
/// that wasm won't access a region would it be safe to construct a mutable
|
|
/// pointer. Additionally even shared pointers are largely unsafe because their
|
|
/// underlying contents may change, so unless `UnsafeCell` in one form or
|
|
/// another is used everywhere there's no safety.
|
|
///
|
|
/// One important point about concurrency is that `Memory::grow` can indeed
|
|
/// happen concurrently. This, however, will never relocate the base pointer.
|
|
/// Shared memories must always have a maximum size and they will be
|
|
/// preallocated such that growth will never relocate the base pointer. The
|
|
/// maximum length of the memory, however, will change over time.
|
|
///
|
|
/// Overall the general rule of thumb for shared memories is that you must
|
|
/// atomically read and write everything. Nothing can be borrowed and everything
|
|
/// must be eagerly copied out.
|
|
///
|
|
/// [interface types]: https://github.com/webassembly/interface-types
|
|
/// [open an issue]: https://github.com/bytecodealliance/wasmtime/issues/new
|
|
#[derive(Clone)]
|
|
pub struct Memory {
|
|
store: Store,
|
|
ty: MemoryType,
|
|
wasmtime_handle: InstanceHandle,
|
|
wasmtime_export: wasmtime_runtime::ExportMemory,
|
|
}
|
|
|
|
impl Memory {
|
|
/// Creates a new WebAssembly memory given the configuration of `ty`.
|
|
///
|
|
/// The `store` argument is a general location for cache information, and
|
|
/// otherwise the memory will immediately be allocated according to the
|
|
/// type's configuration. All WebAssembly memory is initialized to zero.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// # use wasmtime::*;
|
|
/// # fn main() -> anyhow::Result<()> {
|
|
/// let store = Store::default();
|
|
///
|
|
/// let memory_ty = MemoryType::new(Limits::new(1, None));
|
|
/// let memory = Memory::new(&store, memory_ty);
|
|
///
|
|
/// let module = Module::new(&store, "(module (memory (import \"\" \"\") 1))")?;
|
|
/// let instance = Instance::new(&module, &[memory.into()])?;
|
|
/// // ...
|
|
/// # Ok(())
|
|
/// # }
|
|
/// ```
|
|
pub fn new(store: &Store, ty: MemoryType) -> Memory {
|
|
let (wasmtime_handle, wasmtime_export) =
|
|
generate_memory_export(store, &ty).expect("generated memory");
|
|
Memory {
|
|
store: store.clone(),
|
|
ty,
|
|
wasmtime_handle,
|
|
wasmtime_export,
|
|
}
|
|
}
|
|
|
|
/// Returns the underlying type of this memory.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// # use wasmtime::*;
|
|
/// # fn main() -> anyhow::Result<()> {
|
|
/// let store = Store::default();
|
|
/// let module = Module::new(&store, "(module (memory (export \"mem\") 1))")?;
|
|
/// let instance = Instance::new(&module, &[])?;
|
|
/// let memory = instance.get_export("mem").unwrap().memory().unwrap();
|
|
/// let ty = memory.ty();
|
|
/// assert_eq!(ty.limits().min(), 1);
|
|
/// # Ok(())
|
|
/// # }
|
|
/// ```
|
|
pub fn ty(&self) -> &MemoryType {
|
|
&self.ty
|
|
}
|
|
|
|
/// Returns this memory as a slice view that can be read natively in Rust.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// This is an unsafe operation because there is no guarantee that the
|
|
/// following operations do not happen concurrently while the slice is in
|
|
/// use:
|
|
///
|
|
/// * Data could be modified by calling into a wasm module.
|
|
/// * Memory could be relocated through growth by calling into a wasm
|
|
/// module.
|
|
/// * When threads are supported, non-atomic reads will race with other
|
|
/// writes.
|
|
///
|
|
/// Extreme care need be taken when the data of a `Memory` is read. The
|
|
/// above invariants all need to be upheld at a bare minimum, and in
|
|
/// general you'll need to ensure that while you're looking at slice you're
|
|
/// the only one who can possibly look at the slice and read/write it.
|
|
///
|
|
/// Be sure to keep in mind that `Memory` is reference counted, meaning
|
|
/// that there may be other users of this `Memory` instance elsewhere in
|
|
/// your program. Additionally `Memory` can be shared and used in any number
|
|
/// of wasm instances, so calling any wasm code should be considered
|
|
/// dangerous while you're holding a slice of memory.
|
|
///
|
|
/// For more information and examples see the documentation on the
|
|
/// [`Memory`] type.
|
|
pub unsafe fn data_unchecked(&self) -> &[u8] {
|
|
self.data_unchecked_mut()
|
|
}
|
|
|
|
/// Returns this memory as a slice view that can be read and written
|
|
/// natively in Rust.
|
|
///
|
|
/// # Safety
|
|
///
|
|
/// All of the same safety caveats of [`Memory::data_unchecked`] apply
|
|
/// here, doubly so because this is returning a mutable slice! As a
|
|
/// double-extra reminder, remember that `Memory` is reference counted, so
|
|
/// you can very easily acquire two mutable slices by simply calling this
|
|
/// function twice. Extreme caution should be used when using this method,
|
|
/// and in general you probably want to result to unsafe accessors and the
|
|
/// `data` methods below.
|
|
///
|
|
/// For more information and examples see the documentation on the
|
|
/// [`Memory`] type.
|
|
pub unsafe fn data_unchecked_mut(&self) -> &mut [u8] {
|
|
let definition = &*self.wasmtime_export.definition;
|
|
slice::from_raw_parts_mut(definition.base, definition.current_length)
|
|
}
|
|
|
|
/// Returns the base pointer, in the host's address space, that the memory
|
|
/// is located at.
|
|
///
|
|
/// When reading and manipulating memory be sure to read up on the caveats
|
|
/// of [`Memory::data_unchecked`] to make sure that you can safely
|
|
/// read/write the memory.
|
|
///
|
|
/// For more information and examples see the documentation on the
|
|
/// [`Memory`] type.
|
|
pub fn data_ptr(&self) -> *mut u8 {
|
|
unsafe { (*self.wasmtime_export.definition).base }
|
|
}
|
|
|
|
/// Returns the byte length of this memory.
|
|
///
|
|
/// The returned value will be a multiple of the wasm page size, 64k.
|
|
///
|
|
/// For more information and examples see the documentation on the
|
|
/// [`Memory`] type.
|
|
pub fn data_size(&self) -> usize {
|
|
unsafe { (*self.wasmtime_export.definition).current_length }
|
|
}
|
|
|
|
/// Returns the size, in pages, of this wasm memory.
|
|
pub fn size(&self) -> u32 {
|
|
(self.data_size() / wasmtime_environ::WASM_PAGE_SIZE as usize) as u32
|
|
}
|
|
|
|
/// Grows this WebAssembly memory by `delta` pages.
|
|
///
|
|
/// This will attempt to add `delta` more pages of memory on to the end of
|
|
/// this `Memory` instance. If successful this may relocate the memory and
|
|
/// cause [`Memory::data_ptr`] to return a new value. Additionally previous
|
|
/// slices into this memory may no longer be valid.
|
|
///
|
|
/// On success returns the number of pages this memory previously had
|
|
/// before the growth succeeded.
|
|
///
|
|
/// # Errors
|
|
///
|
|
/// Returns an error if memory could not be grown, for example if it exceeds
|
|
/// the maximum limits of this memory.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```
|
|
/// # use wasmtime::*;
|
|
/// # fn main() -> anyhow::Result<()> {
|
|
/// let store = Store::default();
|
|
/// let module = Module::new(&store, "(module (memory (export \"mem\") 1 2))")?;
|
|
/// let instance = Instance::new(&module, &[])?;
|
|
/// let memory = instance.get_export("mem").unwrap().memory().unwrap();
|
|
///
|
|
/// assert_eq!(memory.size(), 1);
|
|
/// assert_eq!(memory.grow(1)?, 1);
|
|
/// assert_eq!(memory.size(), 2);
|
|
/// assert!(memory.grow(1).is_err());
|
|
/// assert_eq!(memory.size(), 2);
|
|
/// assert_eq!(memory.grow(0)?, 2);
|
|
/// # Ok(())
|
|
/// # }
|
|
/// ```
|
|
pub fn grow(&self, delta: u32) -> Result<u32> {
|
|
let index = self
|
|
.wasmtime_handle
|
|
.memory_index(unsafe { &*self.wasmtime_export.definition });
|
|
self.wasmtime_handle
|
|
.clone()
|
|
.memory_grow(index, delta)
|
|
.ok_or_else(|| anyhow!("failed to grow memory"))
|
|
}
|
|
|
|
pub(crate) fn from_wasmtime_memory(
|
|
wasmtime_export: wasmtime_runtime::ExportMemory,
|
|
store: &Store,
|
|
wasmtime_handle: wasmtime_runtime::InstanceHandle,
|
|
) -> Memory {
|
|
let ty = MemoryType::from_wasmtime_memory(&wasmtime_export.memory.memory);
|
|
Memory {
|
|
store: store.clone(),
|
|
ty: ty,
|
|
wasmtime_handle,
|
|
wasmtime_export,
|
|
}
|
|
}
|
|
}
|
|
|
|
/// A linear memory. This trait provides an interface for raw memory buffers which are used
|
|
/// by wasmtime, e.g. inside ['Memory']. Such buffers are in principle not thread safe.
|
|
/// By implementing this trait together with MemoryCreator,
|
|
/// one can supply wasmtime with custom allocated host managed memory.
|
|
///
|
|
/// # Safety
|
|
/// The memory should be page aligned and a multiple of page size.
|
|
/// To prevent possible silent overflows, the memory should be protected by a guard page.
|
|
/// Additionally the safety concerns explained in ['Memory'], for accessing the memory
|
|
/// apply here as well.
|
|
///
|
|
/// Note that this is a relatively new and experimental feature and it is recommended
|
|
/// to be familiar with wasmtime runtime code to use it.
|
|
pub unsafe trait LinearMemory {
|
|
/// Returns the number of allocated wasm pages.
|
|
fn size(&self) -> u32;
|
|
|
|
/// Grow memory by the specified amount of wasm pages.
|
|
///
|
|
/// Returns `None` if memory can't be grown by the specified amount
|
|
/// of wasm pages.
|
|
fn grow(&self, delta: u32) -> Option<u32>;
|
|
|
|
/// Return the allocated memory as a mutable pointer to u8.
|
|
fn as_ptr(&self) -> *mut u8;
|
|
}
|
|
|
|
/// A memory creator. Can be used to provide a memory creator
|
|
/// to wasmtime which supplies host managed memory.
|
|
///
|
|
/// # Safety
|
|
/// This trait is unsafe, as the memory safety depends on proper implementation of
|
|
/// memory management. Memories created by the MemoryCreator should always be treated
|
|
/// as owned by wasmtime instance, and any modification of them outside of wasmtime
|
|
/// invoked routines is unsafe and may lead to corruption.
|
|
///
|
|
/// Note that this is a relatively new and experimental feature and it is recommended
|
|
/// to be familiar with wasmtime runtime code to use it.
|
|
pub unsafe trait MemoryCreator: Send + Sync {
|
|
/// Create new LinearMemory
|
|
fn new_memory(&self, ty: MemoryType) -> Result<Box<dyn LinearMemory>, String>;
|
|
}
|