Expose validation specific host function.

node/core/candidate-validation/src/lib.rs

@@ -178,7 +178,7 @@ async fn runtime_api_request<T>(
 
 #[derive(Debug)]
 enum AssumptionCheckOutcome {
-	Matches(PersistedValidationData, ValidationCode),
+	Matches(PersistedValidationData, Arc<ValidationCode>),
 	DoesNotMatch,
 	BadRequest,
 }
@@ -227,7 +227,7 @@ async fn check_assumption_validation_data(
 
 		match validation_code {
 			Ok(None) | Err(_) => AssumptionCheckOutcome::BadRequest,
-			Ok(Some(v)) => AssumptionCheckOutcome::Matches(validation_data, v),
+			Ok(Some(v)) => AssumptionCheckOutcome::Matches(validation_data, Arc::new(v)),
 		}
 	} else {
 		AssumptionCheckOutcome::DoesNotMatch
@@ -333,7 +333,7 @@ async fn spawn_validate_exhaustive(
 	ctx: &mut impl SubsystemContext<Message = CandidateValidationMessage>,
 	isolation_strategy: IsolationStrategy,
 	persisted_validation_data: PersistedValidationData,
-	validation_code: ValidationCode,
+	validation_code: Arc<ValidationCode>,
 	descriptor: CandidateDescriptor,
 	pov: Arc<PoV>,
 	spawn: impl SpawnNamed + 'static,
@@ -390,7 +390,7 @@ trait ValidationBackend {
 
 	fn validate<S: SpawnNamed + 'static>(
 		arg: Self::Arg,
-		validation_code: &ValidationCode,
+		validation_code: Arc<ValidationCode>,
 		params: ValidationParams,
 		spawn: S,
 	) -> Result<WasmValidationResult, ValidationError>;
@@ -403,12 +403,14 @@ impl ValidationBackend for RealValidationBackend {
 
 	fn validate<S: SpawnNamed + 'static>(
 		isolation_strategy: IsolationStrategy,
-		validation_code: &ValidationCode,
+		validation_code: Arc<ValidationCode>,
 		params: ValidationParams,
 		spawn: S,
 	) -> Result<WasmValidationResult, ValidationError> {
+		let ext = validation_code.clone();
 		wasm_executor::validate_candidate(
-			&validation_code.0,
+			validation_code.0.as_slice(),
+			ext,
 			params,
 			&isolation_strategy,
 			spawn,
@@ -423,7 +425,7 @@ impl ValidationBackend for RealValidationBackend {
 fn validate_candidate_exhaustive<B: ValidationBackend, S: SpawnNamed + 'static>(
 	backend_arg: B::Arg,
 	persisted_validation_data: PersistedValidationData,
-	validation_code: ValidationCode,
+	validation_code: Arc<ValidationCode>,
 	descriptor: CandidateDescriptor,
 	pov: Arc<PoV>,
 	spawn: S,
@@ -442,7 +444,7 @@ fn validate_candidate_exhaustive<B: ValidationBackend, S: SpawnNamed + 'static>(
 		relay_parent_storage_root: persisted_validation_data.relay_parent_storage_root,
 	};
 
-	match B::validate(backend_arg, &validation_code, params, spawn) {
+	match B::validate(backend_arg, validation_code, params, spawn) {
 		Err(ValidationError::InvalidCandidate(WasmInvalidCandidate::Timeout)) =>
 			Ok(ValidationResult::Invalid(InvalidCandidate::Timeout)),
 		Err(ValidationError::InvalidCandidate(WasmInvalidCandidate::ParamsTooLarge(l))) =>
@@ -573,6 +575,7 @@ mod tests {
 	use futures::executor;
 	use assert_matches::assert_matches;
 	use sp_keyring::Sr25519Keyring;
+	use std::sync::Arc;
 
 	struct MockValidationBackend;
 
@@ -585,7 +588,7 @@ mod tests {
 
 		fn validate<S: SpawnNamed + 'static>(
 			arg: Self::Arg,
-			_validation_code: &ValidationCode,
+			_validation_code: Arc<ValidationCode>,
 			_params: ValidationParams,
 			_spawn: S,
 		) -> Result<WasmValidationResult, ValidationError> {
@@ -662,7 +665,7 @@ mod tests {
 
 			assert_matches!(check_result.await.unwrap(), AssumptionCheckOutcome::Matches(o, v) => {
 				assert_eq!(o, validation_data);
-				assert_eq!(v, validation_code);
+				assert_eq!(v.as_ref(), &validation_code);
 			});
 		};
 
@@ -726,7 +729,7 @@ mod tests {
 
 			assert_matches!(check_result.await.unwrap(), AssumptionCheckOutcome::Matches(o, v) => {
 				assert_eq!(o, validation_data);
-				assert_eq!(v, validation_code);
+				assert_eq!(v.as_ref(), &validation_code);
 			});
 		};
 
@@ -910,7 +913,7 @@ mod tests {
 		let v = validate_candidate_exhaustive::<MockValidationBackend, _>(
 			MockValidationArg { result: Ok(validation_result) },
 			validation_data.clone(),
-			vec![1, 2, 3].into(),
+			Arc::new(vec![1, 2, 3].into()),
 			descriptor,
 			Arc::new(pov),
 			TaskExecutor::new(),
@@ -946,7 +949,7 @@ mod tests {
 				))
 			},
 			validation_data,
-			vec![1, 2, 3].into(),
+			Arc::new(vec![1, 2, 3].into()),
 			descriptor,
 			Arc::new(pov),
 			TaskExecutor::new(),
@@ -975,7 +978,7 @@ mod tests {
 				))
 			},
 			validation_data,
-			vec![1, 2, 3].into(),
+			Arc::new(vec![1, 2, 3].into()),
 			descriptor,
 			Arc::new(pov),
 			TaskExecutor::new(),

node/service/src/lib.rs

@@ -78,28 +78,40 @@ native_executor_instance!(
 	pub PolkadotExecutor,
 	polkadot_runtime::api::dispatch,
 	polkadot_runtime::native_version,
-	frame_benchmarking::benchmarking::HostFunctions,
+	(
+		frame_benchmarking::benchmarking::HostFunctions,
+		polkadot_parachain::validation::HostFunctions,
+	),
 );
 
 native_executor_instance!(
 	pub KusamaExecutor,
 	kusama_runtime::api::dispatch,
 	kusama_runtime::native_version,
-	frame_benchmarking::benchmarking::HostFunctions,
+	(
+		frame_benchmarking::benchmarking::HostFunctions,
+		polkadot_parachain::validation::HostFunctions,
+	),
 );
 
 native_executor_instance!(
 	pub WestendExecutor,
 	westend_runtime::api::dispatch,
 	westend_runtime::native_version,
-	frame_benchmarking::benchmarking::HostFunctions,
+	(
+		frame_benchmarking::benchmarking::HostFunctions,
+		polkadot_parachain::validation::HostFunctions,
+	),
 );
 
 native_executor_instance!(
 	pub RococoExecutor,
 	rococo_runtime::api::dispatch,
 	rococo_runtime::native_version,
-	frame_benchmarking::benchmarking::HostFunctions,
+	(
+		frame_benchmarking::benchmarking::HostFunctions,
+		polkadot_parachain::validation::HostFunctions,
+	),
 );
 
 #[derive(thiserror::Error, Debug)]

node/subsystem/src/messages.rs

@@ -139,7 +139,7 @@ pub enum CandidateValidationMessage {
 	/// performed by the relay-chain.
 	ValidateFromExhaustive(
 		PersistedValidationData,
-		ValidationCode,
+		Arc<ValidationCode>,
 		CandidateDescriptor,
 		Arc<PoV>,
 		oneshot::Sender<Result<ValidationResult, ValidationFailed>>,

node/test/service/src/lib.rs

@@ -60,7 +60,10 @@ native_executor_instance!(
 	pub PolkadotTestExecutor,
 	polkadot_test_runtime::api::dispatch,
 	polkadot_test_runtime::native_version,
-	frame_benchmarking::benchmarking::HostFunctions,
+	(
+		frame_benchmarking::benchmarking::HostFunctions,
+		polkadot_parachain::validation::HostFunctions,
+	),
 );
 
 /// The client type being used by the test service.

parachain/Cargo.toml

@@ -15,13 +15,14 @@ sp-std = { git = "https://github.com/paritytech/substrate", branch = "master", d
 sp-runtime = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-core = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 sp-wasm-interface = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
+sp-runtime-interface = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 polkadot-core-primitives = { path = "../core-primitives", default-features = false }
 derive_more = "0.99.11"
+sp-externalities = { git = "https://github.com/paritytech/substrate", branch = "master", default-features = false }
 
 # all optional crates.
 thiserror = { version = "1.0.22", optional = true }
 serde = { version = "1.0.117", default-features = false, features = [ "derive" ], optional = true }
-sp-externalities = { git = "https://github.com/paritytech/substrate", branch = "master", optional = true }
 sc-executor = { git = "https://github.com/paritytech/substrate", branch = "master", optional = true }
 sp-io = { git = "https://github.com/paritytech/substrate", branch = "master", optional = true }
 parking_lot = { version = "0.11.1", optional = true }
@@ -46,7 +47,7 @@ std = [
 	"parking_lot",
 	"log",
 	"parity-util-mem",
-	"sp-externalities",
+	"sp-externalities/std",
 	"sc-executor",
 	"sp-io",
 	"polkadot-core-primitives/std",

parachain/src/lib.rs

@@ -51,3 +51,55 @@ mod wasm_api;
 
 #[cfg(all(not(feature = "std"), feature = "wasm-api"))]
 pub use wasm_api::*;
+
+use sp_std::{vec::Vec, boxed::Box};
+use crate::primitives::ValidationCode;
+
+use sp_runtime_interface::runtime_interface;
+
+/// Validation specific host functions.
+#[runtime_interface]
+pub trait Validation {
+	/// Get validation wasm bytecode.
+	fn validation_code(&mut self) -> Vec<u8> {
+		use sp_externalities::ExternalitiesExt;
+		let extension = self.extension::<ValidationExt>()
+			.expect("Cannot get validation code without dynamic runtime dispatcher (ValidationExt)");
+		extension.validation_code()
+	}
+}
+
+#[cfg(feature = "std")]
+sp_externalities::decl_extension! {
+	///  executor extension.
+	pub struct ValidationExt(Box<dyn Validation>);
+}
+
+#[cfg(feature = "std")]
+impl ValidationExt {
+	/// New instance of task executor extension.
+	pub fn new(validation_ext: impl Validation) -> Self {
+		Self(Box::new(validation_ext))
+	}
+}
+
+/// Base methods to implement validation extension.
+pub trait Validation: Send + 'static {
+	/// Get the validation code currently running.
+	/// This can be use to check validity or to complete
+	/// proofs.
+	fn validation_code(&self) -> Vec<u8>;
+}
+
+#[cfg(feature = "std")]
+impl Validation for std::sync::Arc<ValidationCode> {
+	fn validation_code(&self) -> Vec<u8> {
+		self.0.clone()
+	}
+}
+
+impl<'a> Validation for &'static [u8] {
+	fn validation_code(&self) -> Vec<u8> {
+		self.to_vec()
+	}
+}

parachain/src/wasm_executor/mod.rs

@@ -26,6 +26,7 @@ use parity_scale_codec::{Decode, Encode};
 use sp_core::{storage::{ChildInfo, TrackedStorageKey}, traits::{CallInWasm, SpawnNamed}};
 use sp_externalities::Extensions;
 use sp_wasm_interface::HostFunctions as _;
+use crate::{Validation, ValidationExt};
 
 #[cfg(not(any(target_os = "android", target_os = "unknown")))]
 pub use validation_host::{run_worker, ValidationPool, EXECUTION_TIMEOUT_SEC, WORKER_ARGS};
@@ -167,14 +168,16 @@ pub struct ExecutorCache(sc_executor::WasmExecutor);
 
 impl Default for ExecutorCache {
 	fn default() -> Self {
+		let mut host_functions = HostFunctions::host_functions();
+		host_functions.extend(crate::validation::HostFunctions::host_functions().into_iter());
 		ExecutorCache(sc_executor::WasmExecutor::new(
 			#[cfg(all(feature = "wasmtime", not(any(target_os = "android", target_os = "unknown"))))]
 			sc_executor::WasmExecutionMethod::Compiled,
 			#[cfg(any(not(feature = "wasmtime"), target_os = "android", target_os = "unknown"))]
 			sc_executor::WasmExecutionMethod::Interpreted,
 			// TODO: Make sure we don't use more than 1GB: https://github.com/paritytech/polkadot/issues/699
 			Some(1024),
-			HostFunctions::host_functions(),
+			host_functions,
 			8
 		))
 	}
@@ -185,6 +188,7 @@ impl Default for ExecutorCache {
 /// This will fail if the validation code is not a proper parachain validation module.
 pub fn validate_candidate(
 	validation_code: &[u8],
+	validation_ext: impl Validation,
 	params: ValidationParams,
 	isolation_strategy: &IsolationStrategy,
 	spawner: impl SpawnNamed + 'static,
@@ -196,6 +200,7 @@ pub fn validate_candidate(
 				validation_code,
 				&params.encode(),
 				spawner,
+				validation_ext,
 			)
 		},
 		#[cfg(not(any(target_os = "android", target_os = "unknown")))]
@@ -221,10 +226,12 @@ pub fn validate_candidate_internal(
 	validation_code: &[u8],
 	encoded_call_data: &[u8],
 	spawner: impl SpawnNamed + 'static,
+	validation_ext: impl Validation,
 ) -> Result<ValidationResult, ValidationError> {
 	let executor = &executor.0;
 
 	let mut extensions = Extensions::new();
+	extensions.register(ValidationExt::new(validation_ext));
 	extensions.register(sp_core::traits::TaskExecutorExt::new(spawner));
 	extensions.register(sp_core::traits::CallInWasmExt::new(executor.clone()));