654e953fbf
* Revamp memory management of `InstanceHandle` This commit fixes a known but in Wasmtime where an instance could still be used after it was freed. Unfortunately the fix here is a bit of a hammer, but it's the best that we can do for now. The changes made in this commit are: * A `Store` now stores all `InstanceHandle` objects it ever creates. This keeps all instances alive unconditionally (along with all host functions and such) until the `Store` is itself dropped. Note that a `Store` is reference counted so basically everything has to be dropped to drop anything, there's no longer any partial deallocation of instances. * The `InstanceHandle` type's own reference counting has been removed. This is largely redundant with what's already happening in `Store`, so there's no need to manage two reference counts. * Each `InstanceHandle` no longer tracks its dependencies in terms of instance handles. This set was actually inaccurate due to dynamic updates to tables and such, so we needed to revamp it anyway. * Initialization of an `InstanceHandle` is now deferred until after `InstanceHandle::new`. This allows storing the `InstanceHandle` before side-effectful initialization, such as copying element segments or running the start function, to ensure that regardless of the result of instantiation the underlying `InstanceHandle` is still available to persist in storage. Overall this should fix a known possible way to safely segfault Wasmtime today (yay!) and it should also fix some flaikness I've seen on CI. Turns out one of the spec tests (bulk-memory-operations/partial-init-table-segment.wast) exercises this functionality and we were hitting sporating use-after-free, but only on Windows. * Shuffle some APIs around * Comment weak cycle
36 lines
1.1 KiB
Rust
36 lines
1.1 KiB
Rust
use super::create_handle::create_handle;
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use crate::trampoline::StoreInstanceHandle;
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use crate::Store;
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use crate::{TableType, ValType};
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use anyhow::{bail, Result};
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use wasmtime_environ::entity::PrimaryMap;
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use wasmtime_environ::{wasm, EntityIndex, Module};
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pub fn create_handle_with_table(store: &Store, table: &TableType) -> Result<StoreInstanceHandle> {
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let mut module = Module::new();
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let table = wasm::Table {
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minimum: table.limits().min(),
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maximum: table.limits().max(),
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ty: match table.element() {
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ValType::FuncRef => wasm::TableElementType::Func,
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_ => bail!("cannot support {:?} as a table element", table.element()),
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},
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};
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let tunable = Default::default();
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let table_plan = wasmtime_environ::TablePlan::for_table(table, &tunable);
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let table_id = module.local.table_plans.push(table_plan);
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module
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.exports
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.insert("table".to_string(), EntityIndex::Table(table_id));
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create_handle(
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module,
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store,
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PrimaryMap::new(),
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Default::default(),
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Box::new(()),
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)
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}
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