contracts: Allow stack height metering to be disabled

frame/contracts/src/benchmarking/code.rs

@@ -566,6 +566,9 @@ fn inject_gas_metering<T: Config>(module: Module) -> Module {
 }
 
 fn inject_stack_metering<T: Config>(module: Module) -> Module {
-	let height = T::Schedule::get().limits.stack_height;
-	wasm_instrument::inject_stack_limiter(module, height).unwrap()
+	if let Some(height) = T::Schedule::get().limits.stack_height {
+		wasm_instrument::inject_stack_limiter(module, height).unwrap()
+	} else {
+		module
+	}
 }

frame/contracts/src/benchmarking/mod.rs

@@ -2250,7 +2250,7 @@ benchmarks! {
 	// w_local_get = w_bench - 1 * w_param
 	instr_local_get {
 		let r in 0 .. INSTR_BENCHMARK_BATCHES;
-		let max_locals = T::Schedule::get().limits.stack_height;
+		let max_locals = T::Schedule::get().limits.stack_height.unwrap_or(512);
 		let mut call_body = body::repeated_dyn(r * INSTR_BENCHMARK_BATCH_SIZE, vec![
 			RandomGetLocal(0, max_locals),
 			Regular(Instruction::Drop),
@@ -2267,7 +2267,7 @@ benchmarks! {
 	// w_local_set = w_bench - 1 * w_param
 	instr_local_set {
 		let r in 0 .. INSTR_BENCHMARK_BATCHES;
-		let max_locals = T::Schedule::get().limits.stack_height;
+		let max_locals = T::Schedule::get().limits.stack_height.unwrap_or(512);
 		let mut call_body = body::repeated_dyn(r * INSTR_BENCHMARK_BATCH_SIZE, vec![
 			RandomI64Repeated(1),
 			RandomSetLocal(0, max_locals),
@@ -2284,7 +2284,7 @@ benchmarks! {
 	// w_local_tee = w_bench - 2 * w_param
 	instr_local_tee {
 		let r in 0 .. INSTR_BENCHMARK_BATCHES;
-		let max_locals = T::Schedule::get().limits.stack_height;
+		let max_locals = T::Schedule::get().limits.stack_height.unwrap_or(512);
 		let mut call_body = body::repeated_dyn(r * INSTR_BENCHMARK_BATCH_SIZE, vec![
 			RandomI64Repeated(1),
 			RandomTeeLocal(0, max_locals),

frame/contracts/src/schedule.rs

@@ -104,7 +104,13 @@ pub struct Limits {
 	/// See <https://wiki.parity.io/WebAssembly-StackHeight> to find out
 	/// how the stack frame cost is calculated. Each element can be of one of the
 	/// wasm value types. This means the maximum size per element is 64bit.
-	pub stack_height: u32,
+	///
+	/// # Note
+	///
+	/// It is safe to disable (pass `None`) the `stack_height` when the execution engine
+	/// is part of the runtime and hence there can be no indeterminism between different
+	/// client resident execution engines.
+	pub stack_height: Option<u32>,
 
 	/// Maximum number of globals a module is allowed to declare.
 	///
@@ -496,8 +502,8 @@ impl Default for Limits {
 	fn default() -> Self {
 		Self {
 			event_topics: 4,
-			// 512 * sizeof(i64) will give us a 4k stack.
-			stack_height: 512,
+			// No stack limit required because we use a runtime resident execution engine.
+			stack_height: None,
 			globals: 256,
 			parameters: 128,
 			memory_pages: 16,

frame/contracts/src/tests.rs

@@ -239,7 +239,13 @@ parameter_types! {
 	pub const MaxValueSize: u32 = 16_384;
 	pub const DeletionWeightLimit: Weight = 500_000_000_000;
 	pub const MaxCodeSize: u32 = 2 * 1024;
-	pub MySchedule: Schedule<Test> = <Schedule<Test>>::default();
+	pub MySchedule: Schedule<Test> = {
+		let mut schedule = <Schedule<Test>>::default();
+		// We want stack height to be always enabled for tests so that this
+		// instrumentation path is always tested implicitly.
+		schedule.limits.stack_height = Some(512);
+		schedule
+	};
 	pub const TransactionByteFee: u64 = 0;
 	pub static DepositPerByte: BalanceOf<Test> = 1;
 	pub const DepositPerItem: BalanceOf<Test> = 2;

frame/contracts/src/wasm/prepare.rs

@@ -191,10 +191,13 @@ impl<'a, T: Config> ContractModule<'a, T> {
 	}
 
 	fn inject_stack_height_metering(self) -> Result<Self, &'static str> {
-		let contract_module =
-			wasm_instrument::inject_stack_limiter(self.module, self.schedule.limits.stack_height)
+		if let Some(limit) = self.schedule.limits.stack_height {
+			let contract_module = wasm_instrument::inject_stack_limiter(self.module, limit)
 				.map_err(|_| "stack height instrumentation failed")?;
-		Ok(ContractModule { module: contract_module, schedule: self.schedule })
+			Ok(ContractModule { module: contract_module, schedule: self.schedule })
+		} else {
+			Ok(ContractModule { module: self.module, schedule: self.schedule })
+		}
 	}
 
 	/// Check that the module has required exported functions. For now