sc_executor/

executor.rs

// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

use crate::{
	error::{Error, Result},
	wasm_runtime::{RuntimeCache, WasmExecutionMethod},
	RuntimeVersionOf,
};

use std::{
	marker::PhantomData,
	panic::{AssertUnwindSafe, UnwindSafe},
	path::PathBuf,
	sync::Arc,
};

use codec::Encode;
use sc_executor_common::{
	runtime_blob::RuntimeBlob,
	wasm_runtime::{
		AllocationStats, HeapAllocStrategy, WasmInstance, WasmModule, DEFAULT_HEAP_ALLOC_STRATEGY,
	},
};
use sp_core::traits::{CallContext, CodeExecutor, Externalities, RuntimeCode};
use sp_version::RuntimeVersion;
use sp_wasm_interface::HostFunctions;

/// Set up the externalities and safe calling environment to execute runtime calls.
///
/// If the inner closure panics, it will be caught and return an error.
pub fn with_externalities_safe<F, U>(ext: &mut dyn Externalities, f: F) -> Result<U>
where
	F: UnwindSafe + FnOnce() -> U,
{
	sp_externalities::set_and_run_with_externalities(ext, move || {
		// Substrate uses custom panic hook that terminates process on panic. Disable
		// termination for the native call.
		let _guard = sp_panic_handler::AbortGuard::force_unwind();
		std::panic::catch_unwind(f).map_err(|e| {
			if let Some(err) = e.downcast_ref::<String>() {
				Error::RuntimePanicked(err.clone())
			} else if let Some(err) = e.downcast_ref::<&'static str>() {
				Error::RuntimePanicked(err.to_string())
			} else {
				Error::RuntimePanicked("Unknown panic".into())
			}
		})
	})
}

fn unwrap_heap_pages(pages: Option<HeapAllocStrategy>) -> HeapAllocStrategy {
	pages.unwrap_or_else(|| DEFAULT_HEAP_ALLOC_STRATEGY)
}

/// Builder for creating a [`WasmExecutor`] instance.
pub struct WasmExecutorBuilder<H = sp_io::SubstrateHostFunctions> {
	_phantom: PhantomData<H>,
	method: WasmExecutionMethod,
	onchain_heap_alloc_strategy: Option<HeapAllocStrategy>,
	offchain_heap_alloc_strategy: Option<HeapAllocStrategy>,
	ignore_onchain_heap_pages: bool,
	max_runtime_instances: usize,
	cache_path: Option<PathBuf>,
	allow_missing_host_functions: bool,
	runtime_cache_size: u8,
}

impl<H> WasmExecutorBuilder<H> {
	/// Create a new instance of `Self`
	///
	/// - `method`: The wasm execution method that should be used by the executor.
	pub fn new() -> Self {
		Self {
			_phantom: PhantomData,
			method: WasmExecutionMethod::default(),
			onchain_heap_alloc_strategy: None,
			offchain_heap_alloc_strategy: None,
			ignore_onchain_heap_pages: false,
			max_runtime_instances: 2,
			runtime_cache_size: 4,
			allow_missing_host_functions: false,
			cache_path: None,
		}
	}

	/// Create the wasm executor with execution method that should be used by the executor.
	pub fn with_execution_method(mut self, method: WasmExecutionMethod) -> Self {
		self.method = method;
		self
	}

	/// Create the wasm executor with the given number of `heap_alloc_strategy` for onchain runtime
	/// calls.
	pub fn with_onchain_heap_alloc_strategy(
		mut self,
		heap_alloc_strategy: HeapAllocStrategy,
	) -> Self {
		self.onchain_heap_alloc_strategy = Some(heap_alloc_strategy);
		self
	}

	/// Create the wasm executor with the given number of `heap_alloc_strategy` for offchain runtime
	/// calls.
	pub fn with_offchain_heap_alloc_strategy(
		mut self,
		heap_alloc_strategy: HeapAllocStrategy,
	) -> Self {
		self.offchain_heap_alloc_strategy = Some(heap_alloc_strategy);
		self
	}

	/// Create the wasm executor and follow/ignore onchain heap pages value.
	///
	/// By default this the onchain heap pages value is followed.
	pub fn with_ignore_onchain_heap_pages(mut self, ignore_onchain_heap_pages: bool) -> Self {
		self.ignore_onchain_heap_pages = ignore_onchain_heap_pages;
		self
	}

	/// Create the wasm executor with the given maximum number of `instances`.
	///
	/// The number of `instances` defines how many different instances of a runtime the cache is
	/// storing.
	///
	/// By default the maximum number of `instances` is `2`.
	pub fn with_max_runtime_instances(mut self, instances: usize) -> Self {
		self.max_runtime_instances = instances;
		self
	}

	/// Create the wasm executor with the given `cache_path`.
	///
	/// The `cache_path` is A path to a directory where the executor can place its files for
	/// purposes of caching. This may be important in cases when there are many different modules
	/// with the compiled execution method is used.
	///
	/// By default there is no `cache_path` given.
	pub fn with_cache_path(mut self, cache_path: impl Into<PathBuf>) -> Self {
		self.cache_path = Some(cache_path.into());
		self
	}

	/// Create the wasm executor and allow/forbid missing host functions.
	///
	/// If missing host functions are forbidden, the instantiation of a wasm blob will fail
	/// for imported host functions that the executor is not aware of. If they are allowed,
	/// a stub is generated that will return an error when being called while executing the wasm.
	///
	/// By default missing host functions are forbidden.
	pub fn with_allow_missing_host_functions(mut self, allow: bool) -> Self {
		self.allow_missing_host_functions = allow;
		self
	}

	/// Create the wasm executor with the given `runtime_cache_size`.
	///
	/// Defines the number of different runtimes/instantiated wasm blobs the cache stores.
	/// Runtimes/wasm blobs are differentiated based on the hash and the number of heap pages.
	///
	/// By default this value is set to `4`.
	pub fn with_runtime_cache_size(mut self, runtime_cache_size: u8) -> Self {
		self.runtime_cache_size = runtime_cache_size;
		self
	}

	/// Build the configured [`WasmExecutor`].
	pub fn build(self) -> WasmExecutor<H> {
		WasmExecutor {
			method: self.method,
			default_offchain_heap_alloc_strategy: unwrap_heap_pages(
				self.offchain_heap_alloc_strategy,
			),
			default_onchain_heap_alloc_strategy: unwrap_heap_pages(
				self.onchain_heap_alloc_strategy,
			),
			ignore_onchain_heap_pages: self.ignore_onchain_heap_pages,
			cache: Arc::new(RuntimeCache::new(
				self.max_runtime_instances,
				self.cache_path.clone(),
				self.runtime_cache_size,
			)),
			cache_path: self.cache_path,
			allow_missing_host_functions: self.allow_missing_host_functions,
			phantom: PhantomData,
		}
	}
}

/// An abstraction over Wasm code executor. Supports selecting execution backend and
/// manages runtime cache.
pub struct WasmExecutor<H = sp_io::SubstrateHostFunctions> {
	/// Method used to execute fallback Wasm code.
	method: WasmExecutionMethod,
	/// The heap allocation strategy for onchain Wasm calls.
	default_onchain_heap_alloc_strategy: HeapAllocStrategy,
	/// The heap allocation strategy for offchain Wasm calls.
	default_offchain_heap_alloc_strategy: HeapAllocStrategy,
	/// Ignore onchain heap pages value.
	ignore_onchain_heap_pages: bool,
	/// WASM runtime cache.
	cache: Arc<RuntimeCache>,
	/// The path to a directory which the executor can leverage for a file cache, e.g. put there
	/// compiled artifacts.
	cache_path: Option<PathBuf>,
	/// Ignore missing function imports.
	allow_missing_host_functions: bool,
	phantom: PhantomData<H>,
}

impl<H> Clone for WasmExecutor<H> {
	fn clone(&self) -> Self {
		Self {
			method: self.method,
			default_onchain_heap_alloc_strategy: self.default_onchain_heap_alloc_strategy,
			default_offchain_heap_alloc_strategy: self.default_offchain_heap_alloc_strategy,
			ignore_onchain_heap_pages: self.ignore_onchain_heap_pages,
			cache: self.cache.clone(),
			cache_path: self.cache_path.clone(),
			allow_missing_host_functions: self.allow_missing_host_functions,
			phantom: self.phantom,
		}
	}
}

impl Default for WasmExecutor<sp_io::SubstrateHostFunctions> {
	fn default() -> Self {
		WasmExecutorBuilder::new().build()
	}
}

impl<H> WasmExecutor<H> {
	/// Create new instance.
	///
	/// # Parameters
	///
	/// `method` - Method used to execute Wasm code.
	///
	/// `default_heap_pages` - Number of 64KB pages to allocate for Wasm execution. Internally this
	/// will be mapped as [`HeapAllocStrategy::Static`] where `default_heap_pages` represent the
	/// static number of heap pages to allocate. Defaults to `DEFAULT_HEAP_ALLOC_STRATEGY` if `None`
	/// is provided.
	///
	/// `max_runtime_instances` - The number of runtime instances to keep in memory ready for reuse.
	///
	/// `cache_path` - A path to a directory where the executor can place its files for purposes of
	///   caching. This may be important in cases when there are many different modules with the
	///   compiled execution method is used.
	///
	/// `runtime_cache_size` - The capacity of runtime cache.
	#[deprecated(note = "use `Self::builder` method instead of it")]
	pub fn new(
		method: WasmExecutionMethod,
		default_heap_pages: Option<u64>,
		max_runtime_instances: usize,
		cache_path: Option<PathBuf>,
		runtime_cache_size: u8,
	) -> Self {
		WasmExecutor {
			method,
			default_onchain_heap_alloc_strategy: unwrap_heap_pages(
				default_heap_pages.map(|h| HeapAllocStrategy::Static { extra_pages: h as _ }),
			),
			default_offchain_heap_alloc_strategy: unwrap_heap_pages(
				default_heap_pages.map(|h| HeapAllocStrategy::Static { extra_pages: h as _ }),
			),
			ignore_onchain_heap_pages: false,
			cache: Arc::new(RuntimeCache::new(
				max_runtime_instances,
				cache_path.clone(),
				runtime_cache_size,
			)),
			cache_path,
			allow_missing_host_functions: false,
			phantom: PhantomData,
		}
	}

	/// Instantiate a builder for creating an instance of `Self`.
	pub fn builder() -> WasmExecutorBuilder<H> {
		WasmExecutorBuilder::new()
	}

	/// Ignore missing function imports if set true.
	#[deprecated(note = "use `Self::builder` method instead of it")]
	pub fn allow_missing_host_functions(&mut self, allow_missing_host_functions: bool) {
		self.allow_missing_host_functions = allow_missing_host_functions
	}
}

impl<H> WasmExecutor<H>
where
	H: HostFunctions,
{
	/// Execute the given closure `f` with the latest runtime (based on `runtime_code`).
	///
	/// The closure `f` is expected to return `Err(_)` when there happened a `panic!` in native code
	/// while executing the runtime in Wasm. If a `panic!` occurred, the runtime is invalidated to
	/// prevent any poisoned state. Native runtime execution does not need to report back
	/// any `panic!`.
	///
	/// # Safety
	///
	/// `runtime` and `ext` are given as `AssertUnwindSafe` to the closure. As described above, the
	/// runtime is invalidated on any `panic!` to prevent a poisoned state. `ext` is already
	/// implicitly handled as unwind safe, as we store it in a global variable while executing the
	/// native runtime.
	pub fn with_instance<R, F>(
		&self,
		runtime_code: &RuntimeCode,
		ext: &mut dyn Externalities,
		heap_alloc_strategy: HeapAllocStrategy,
		f: F,
	) -> Result<R>
	where
		F: FnOnce(
			AssertUnwindSafe<&dyn WasmModule>,
			AssertUnwindSafe<&mut dyn WasmInstance>,
			Option<&RuntimeVersion>,
			AssertUnwindSafe<&mut dyn Externalities>,
		) -> Result<Result<R>>,
	{
		match self.cache.with_instance::<H, _, _>(
			runtime_code,
			ext,
			self.method,
			heap_alloc_strategy,
			self.allow_missing_host_functions,
			|module, instance, version, ext| {
				let module = AssertUnwindSafe(module);
				let instance = AssertUnwindSafe(instance);
				let ext = AssertUnwindSafe(ext);
				f(module, instance, version, ext)
			},
		)? {
			Ok(r) => r,
			Err(e) => Err(e),
		}
	}

	/// Perform a call into the given runtime.
	///
	/// The runtime is passed as a [`RuntimeBlob`]. The runtime will be instantiated with the
	/// parameters this `WasmExecutor` was initialized with.
	///
	/// In case of problems with during creation of the runtime or instantiation, a `Err` is
	/// returned. that describes the message.
	#[doc(hidden)] // We use this function for tests across multiple crates.
	pub fn uncached_call(
		&self,
		runtime_blob: RuntimeBlob,
		ext: &mut dyn Externalities,
		allow_missing_host_functions: bool,
		export_name: &str,
		call_data: &[u8],
	) -> std::result::Result<Vec<u8>, Error> {
		self.uncached_call_impl(
			runtime_blob,
			ext,
			allow_missing_host_functions,
			export_name,
			call_data,
			&mut None,
		)
	}

	/// Same as `uncached_call`, except it also returns allocation statistics.
	#[doc(hidden)] // We use this function in tests.
	pub fn uncached_call_with_allocation_stats(
		&self,
		runtime_blob: RuntimeBlob,
		ext: &mut dyn Externalities,
		allow_missing_host_functions: bool,
		export_name: &str,
		call_data: &[u8],
	) -> (std::result::Result<Vec<u8>, Error>, Option<AllocationStats>) {
		let mut allocation_stats = None;
		let result = self.uncached_call_impl(
			runtime_blob,
			ext,
			allow_missing_host_functions,
			export_name,
			call_data,
			&mut allocation_stats,
		);
		(result, allocation_stats)
	}

	fn uncached_call_impl(
		&self,
		runtime_blob: RuntimeBlob,
		ext: &mut dyn Externalities,
		allow_missing_host_functions: bool,
		export_name: &str,
		call_data: &[u8],
		allocation_stats_out: &mut Option<AllocationStats>,
	) -> std::result::Result<Vec<u8>, Error> {
		let module = crate::wasm_runtime::create_wasm_runtime_with_code::<H>(
			self.method,
			self.default_onchain_heap_alloc_strategy,
			runtime_blob,
			allow_missing_host_functions,
			self.cache_path.as_deref(),
		)
		.map_err(|e| format!("Failed to create module: {}", e))?;

		let instance = module
			.new_instance(self.default_onchain_heap_alloc_strategy)
			.map_err(|e| format!("Failed to create instance: {}", e))?;

		let mut instance = AssertUnwindSafe(instance);
		let mut ext = AssertUnwindSafe(ext);
		let mut allocation_stats_out = AssertUnwindSafe(allocation_stats_out);

		with_externalities_safe(&mut **ext, move || {
			let (result, allocation_stats) =
				instance.call_with_allocation_stats(export_name.into(), call_data);
			**allocation_stats_out = allocation_stats;
			result
		})
		.and_then(|r| r)
	}
}

impl<H> sp_core::traits::ReadRuntimeVersion for WasmExecutor<H>
where
	H: HostFunctions,
{
	fn read_runtime_version(
		&self,
		wasm_code: &[u8],
		ext: &mut dyn Externalities,
	) -> std::result::Result<Vec<u8>, String> {
		let runtime_blob = RuntimeBlob::uncompress_if_needed(wasm_code)
			.map_err(|e| format!("Failed to create runtime blob: {:?}", e))?;

		if let Some(version) = crate::wasm_runtime::read_embedded_version(&runtime_blob)
			.map_err(|e| format!("Failed to read the static section: {:?}", e))
			.map(|v| v.map(|v| v.encode()))?
		{
			return Ok(version);
		}

		// If the blob didn't have embedded runtime version section, we fallback to the legacy
		// way of fetching the version: i.e. instantiating the given instance and calling
		// `Core_version` on it.

		self.uncached_call(
			runtime_blob,
			ext,
			// If a runtime upgrade introduces new host functions that are not provided by
			// the node, we should not fail at instantiation. Otherwise nodes that are
			// updated could run this successfully and it could lead to a storage root
			// mismatch when importing this block.
			true,
			"Core_version",
			&[],
		)
		.map_err(|e| e.to_string())
	}
}

impl<H> CodeExecutor for WasmExecutor<H>
where
	H: HostFunctions,
{
	type Error = Error;

	fn call(
		&self,
		ext: &mut dyn Externalities,
		runtime_code: &RuntimeCode,
		method: &str,
		data: &[u8],
		context: CallContext,
	) -> (Result<Vec<u8>>, bool) {
		tracing::trace!(
			target: "executor",
			%method,
			"Executing function",
		);

		let on_chain_heap_alloc_strategy = if self.ignore_onchain_heap_pages {
			self.default_onchain_heap_alloc_strategy
		} else {
			runtime_code
				.heap_pages
				.map(|h| HeapAllocStrategy::Static { extra_pages: h as _ })
				.unwrap_or_else(|| self.default_onchain_heap_alloc_strategy)
		};

		let heap_alloc_strategy = match context {
			CallContext::Offchain => self.default_offchain_heap_alloc_strategy,
			CallContext::Onchain { import: false } => on_chain_heap_alloc_strategy,
			CallContext::Onchain { import: true } => on_chain_heap_alloc_strategy.double(),
		};

		let result = self.with_instance(
			runtime_code,
			ext,
			heap_alloc_strategy,
			|_, mut instance, _on_chain_version, mut ext| {
				with_externalities_safe(&mut **ext, move || instance.call_export(method, data))
			},
		);

		(result, false)
	}
}

impl<H> RuntimeVersionOf for WasmExecutor<H>
where
	H: HostFunctions,
{
	fn runtime_version(
		&self,
		ext: &mut dyn Externalities,
		runtime_code: &RuntimeCode,
	) -> Result<RuntimeVersion> {
		let on_chain_heap_pages = if self.ignore_onchain_heap_pages {
			self.default_onchain_heap_alloc_strategy
		} else {
			runtime_code
				.heap_pages
				.map(|h| HeapAllocStrategy::Static { extra_pages: h as _ })
				.unwrap_or_else(|| self.default_onchain_heap_alloc_strategy)
		};

		self.with_instance(
			runtime_code,
			ext,
			on_chain_heap_pages,
			|_module, _instance, version, _ext| {
				Ok(version.cloned().ok_or_else(|| Error::ApiError("Unknown version".into())))
			},
		)
	}
}

#[cfg(test)]
mod tests {
	use super::*;
	use sp_runtime_interface::{pass_by::PassFatPointerAndRead, runtime_interface};
	use sp_wasm_interface::ExtendedHostFunctions;

	#[runtime_interface]
	trait MyInterface {
		fn say_hello_world(data: PassFatPointerAndRead<&str>) {
			println!("Hello world from: {}", data);
		}
	}

	#[test]
	fn wasm_executor_registers_custom_interface() {
		type Hosts = ExtendedHostFunctions<
			sp_io::SubstrateHostFunctions,
			(my_interface::HostFunctions, my_interface::HostFunctions),
		>;

		let executor = WasmExecutor::<Hosts>::builder().build();

		fn extract_host_functions<H>(
			_: &WasmExecutor<H>,
		) -> Vec<&'static dyn sp_wasm_interface::Function>
		where
			H: HostFunctions,
		{
			H::host_functions()
		}

		my_interface::HostFunctions::host_functions().iter().for_each(|function| {
			assert_eq!(
				extract_host_functions(&executor).iter().filter(|f| f == &function).count(),
				2
			);
		});

		my_interface::say_hello_world("hey");
	}
}