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Add resource limiting to the Wasmtime API. (#2736)

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* Add resource limiting to the Wasmtime API.

This commit adds a `ResourceLimiter` trait to the Wasmtime API.

When used in conjunction with `Store::new_with_limiter`, this can be used to
monitor and prevent WebAssembly code from growing linear memories and tables.

This is particularly useful when hosts need to take into account host resource
usage to determine if WebAssembly code can consume more resources.

A simple `StaticResourceLimiter` is also included with these changes that will
simply limit the size of linear memories or tables for all instances created in
the store based on static values.

* Code review feedback.

* Implemented `StoreLimits` and `StoreLimitsBuilder`.
* Moved `max_instances`, `max_memories`, `max_tables` out of `Config` and into
  `StoreLimits`.
* Moved storage of the limiter in the runtime into `Memory` and `Table`.
* Made `InstanceAllocationRequest` use a reference to the limiter.
* Updated docs.
* Made `ResourceLimiterProxy` generic to remove a level of indirection.
* Fixed the limiter not being used for `wasmtime::Memory` and
  `wasmtime::Table`.

* Code review feedback and bug fix.

* `Memory::new` now returns `Result<Self>` so that an error can be returned if
  the initial requested memory exceeds any limits placed on the store.

* Changed an `Arc` to `Rc` as the `Arc` wasn't necessary.

* Removed `Store` from the `ResourceLimiter` callbacks. Custom resource limiter
  implementations are free to capture any context they want, so no need to
  unnecessarily store a weak reference to `Store` from the proxy type.

* Fixed a bug in the pooling instance allocator where an instance would be
  leaked from the pool. Previously, this would only have happened if the OS was
  unable to make the necessary linear memory available for the instance. With
  these changes, however, the instance might not be created due to limits
  placed on the store. We now properly deallocate the instance on error.

* Added more tests, including one that covers the fix mentioned above.

* Code review feedback.

* Add another memory to `test_pooling_allocator_initial_limits_exceeded` to
  ensure a partially created instance is successfully deallocated.
* Update some doc comments for better documentation of `Store` and
  `ResourceLimiter`.
This commit is contained in:
Peter Huene
2021-04-19 07:19:20 -07:00
committed by GitHub
parent 52b1166918
commit f12b4c467c
30 changed files with 1063 additions and 218 deletions
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78
crates/runtime/src/instance.rs
View File

@@ -37,6 +37,52 @@ mod allocator;
pub use allocator::*;
/// Used by hosts to limit resource consumption of instances.
///
/// An instance can be created with a resource limiter so that hosts can take into account
/// non-WebAssembly resource usage to determine if a linear memory or table should grow.
pub trait ResourceLimiter {
/// Notifies the resource limiter that an instance's linear memory has been requested to grow.
///
/// * `current` is the current size of the linear memory in WebAssembly page units.
/// * `desired` is the desired size of the linear memory in WebAssembly page units.
/// * `maximum` is either the linear memory's maximum or a maximum from an instance allocator,
/// also in WebAssembly page units. A value of `None` indicates that the linear memory is
/// unbounded.
///
/// This function should return `true` to indicate that the growing operation is permitted or
/// `false` if not permitted. Returning `true` when a maximum has been exceeded will have no
/// effect as the linear memory will not grow.
fn memory_growing(&self, current: u32, desired: u32, maximum: Option<u32>) -> bool;
/// Notifies the resource limiter that an instance's table has been requested to grow.
///
/// * `current` is the current number of elements in the table.
/// * `desired` is the desired number of elements in the table.
/// * `maximum` is either the table's maximum or a maximum from an instance allocator.
/// A value of `None` indicates that the table is unbounded.
///
/// This function should return `true` to indicate that the growing operation is permitted or
/// `false` if not permitted. Returning `true` when a maximum has been exceeded will have no
/// effect as the table will not grow.
fn table_growing(&self, current: u32, desired: u32, maximum: Option<u32>) -> bool;
/// The maximum number of instances that can be created for a `Store`.
///
/// Module instantiation will fail if this limit is exceeded.
fn instances(&self) -> usize;
/// The maximum number of tables that can be created for a `Store`.
///
/// Module instantiation will fail if this limit is exceeded.
fn tables(&self) -> usize;
/// The maximum number of tables that can be created for a `Store`.
///
/// Module instantiation will fail if this limit is exceeded.
fn memories(&self) -> usize;
}
/// Runtime representation of an instance value, which erases all `Instance`
/// information since instances are just a collection of values.
pub type RuntimeInstance = Rc<IndexMap<String, Export>>;
@@ -378,11 +424,12 @@ impl Instance {
/// Returns `None` if memory can't be grown by the specified amount
/// of pages.
pub(crate) fn memory_grow(&self, memory_index: DefinedMemoryIndex, delta: u32) -> Option<u32> {
let result = self
let memory = self
.memories
.get(memory_index)
.unwrap_or_else(|| panic!("no memory for index {}", memory_index.index()))
.grow(delta);
.unwrap_or_else(|| panic!("no memory for index {}", memory_index.index()));
let result = unsafe { memory.grow(delta) };
// Keep current the VMContext pointers used by compiled wasm code.
self.set_memory(memory_index, self.memories[memory_index].vmmemory());
@@ -460,19 +507,18 @@ impl Instance {
delta: u32,
init_value: TableElement,
) -> Option<u32> {
unsafe {
let orig_size = self
.tables
.get(table_index)
.unwrap_or_else(|| panic!("no table for index {}", table_index.index()))
.grow(delta, init_value)?;
let table = self
.tables
.get(table_index)
.unwrap_or_else(|| panic!("no table for index {}", table_index.index()));
// Keep the `VMContext` pointers used by compiled Wasm code up to
// date.
self.set_table(table_index, self.tables[table_index].vmtable());
let result = unsafe { table.grow(delta, init_value) };
Some(orig_size)
}
// Keep the `VMContext` pointers used by compiled Wasm code up to
// date.
self.set_table(table_index, self.tables[table_index].vmtable());
result
}
pub(crate) fn defined_table_fill(
@@ -818,10 +864,6 @@ pub struct InstanceHandle {
}
impl InstanceHandle {
pub(crate) unsafe fn new(instance: *mut Instance) -> Self {
Self { instance }
}
/// Create a new `InstanceHandle` pointing at the instance
/// pointed to by the given `VMContext` pointer.
///