Hybrid call stack (#202)

gasometer/src/lib.rs

@@ -32,7 +32,6 @@ impl Gas for U256 {}
 pub enum GasometerMergeStrategy {
 	Commit,
 	Revert,
-	Discard,
 }
 
 pub trait Gasometer<S, H>: Sized {
@@ -54,8 +53,8 @@ pub trait Gasometer<S, H>: Sized {
 pub fn run_with_gasometer<S, H, Tr, G, F>(
 	machine: &mut Machine<S>,
 	gasometer: &mut G,
-	handler: &mut H,
 	is_static: bool,
+	handler: &mut H,
 	etable: &Etable<S, H, Tr, F>,
 ) -> Capture<ExitResult, Tr>
 where

gasometer/src/standard.rs

@@ -131,7 +131,6 @@ impl<'config, H: Handler> Gasometer<RuntimeState, H> for StandardGasometer<'conf
 			GasometerMergeStrategy::Revert => {
 				self.used_gas -= Gasometer::<RuntimeState, H>::gas(&other);
 			}
-			GasometerMergeStrategy::Discard => (),
 		}
 	}
 }

src/executor.rs

@@ -3,8 +3,10 @@ use crate::{
 	Capture, Control, Etable, ExitError, ExitResult, Machine, Opcode, TransactionalBackend,
 	TransactionalMergeStrategy,
 };
+use core::convert::Infallible;
 
 pub trait Invoker<S, H, Tr, G> {
+	type Interrupt;
 	type TrapData;
 
 	fn feedback_trap_data(
@@ -20,14 +22,15 @@ pub trait Invoker<S, H, Tr, G> {
 	fn prepare_trap_data(
 		&self,
 		trap: Tr,
+		depth: usize,
 		machine: &mut Machine<S>,
 		gasometer: &mut G,
 		handler: &mut H,
-	) -> Capture<Result<Self::TrapData, ExitError>, Tr>;
+	) -> Capture<Result<Self::TrapData, ExitError>, Self::Interrupt>;
 
 	fn build_child_stack(
 		&self,
-		trap_data: Self::TrapData,
+		trap_data: &Self::TrapData,
 		handler: &mut H,
 	) -> Result<(Machine<S>, G, bool), ExitError>;
 }
@@ -61,6 +64,7 @@ enum LastCallStackData<S, Tr, G> {
 pub struct CallStack<'backend, 'invoker, S, H, Tr, G, I: Invoker<S, H, Tr, G>> {
 	stack: Vec<TrappedCallStackData<S, G, I::TrapData>>,
 	last: LastCallStackData<S, Tr, G>,
+	initial_depth: usize,
 	backend: &'backend mut H,
 	invoker: &'invoker I,
 }
@@ -75,6 +79,7 @@ where
 		machine: Machine<S>,
 		gasometer: G,
 		is_static: bool,
+		initial_depth: usize,
 		backend: &'backend mut H,
 		invoker: &'invoker I,
 	) -> Self {
@@ -87,14 +92,52 @@ where
 		let call_stack = Self {
 			stack: Vec::new(),
 			last,
+			initial_depth,
 			backend,
 			invoker,
 		};
 
 		call_stack
 	}
 
-	pub fn run<F>(mut self, etable: &Etable<S, H, Tr, F>) -> (Self, Capture<(), Tr>)
+	/// Calling `expect_exit` after `execute` returns `Capture::Exit` is safe.
+	pub fn expect_exit(self) -> (Machine<S>, G, ExitResult) {
+		match self.last {
+			LastCallStackData::Exited {
+				machine,
+				gasometer,
+				result: Capture::Exit(exit),
+				..
+			} => (machine, gasometer, exit),
+			_ => panic!("expected exit"),
+		}
+	}
+
+	pub fn execute<F>(
+		machine: Machine<S>,
+		gasometer: G,
+		is_static: bool,
+		initial_depth: usize,
+		backend: &'backend mut H,
+		invoker: &'invoker I,
+		etable: &Etable<S, H, Tr, F>,
+	) -> (Self, Capture<(), I::Interrupt>)
+	where
+		F: Fn(&mut Machine<S>, &mut H, Opcode, usize) -> Control<Tr>,
+	{
+		let call_stack = Self::new(
+			machine,
+			gasometer,
+			is_static,
+			initial_depth,
+			backend,
+			invoker,
+		);
+
+		call_stack.run(etable)
+	}
+
+	pub fn run<F>(mut self, etable: &Etable<S, H, Tr, F>) -> (Self, Capture<(), I::Interrupt>)
 	where
 		F: Fn(&mut Machine<S>, &mut H, Opcode, usize) -> Control<Tr>,
 	{
@@ -108,11 +151,11 @@ where
 		}
 	}
 
-	fn step<F>(mut self, etable: &Etable<S, H, Tr, F>) -> (Self, Option<Capture<(), Tr>>)
+	fn step<F>(mut self, etable: &Etable<S, H, Tr, F>) -> (Self, Option<Capture<(), I::Interrupt>>)
 	where
 		F: Fn(&mut Machine<S>, &mut H, Opcode, usize) -> Control<Tr>,
 	{
-		let mut step_ret: Option<Capture<(), Tr>> = None;
+		let mut step_ret: Option<Capture<(), I::Interrupt>> = None;
 
 		self.last = match self.last {
 			LastCallStackData::ExternalTrapped {
@@ -132,8 +175,8 @@ where
 				let result = run_with_gasometer(
 					&mut machine,
 					&mut gasometer,
-					self.backend,
 					is_static,
+					self.backend,
 					etable,
 				);
 				LastCallStackData::Exited {
@@ -183,9 +226,6 @@ where
 							Err(_) => {
 								self.backend
 									.pop_substate(TransactionalMergeStrategy::Discard);
-								upward
-									.gasometer
-									.merge(gasometer, GasometerMergeStrategy::Discard);
 							}
 						};
 
@@ -216,25 +256,40 @@ where
 				Capture::Trap(trap) => {
 					match self.invoker.prepare_trap_data(
 						trap,
+						self.initial_depth + self.stack.len() + 1,
 						&mut machine,
 						&mut gasometer,
 						self.backend,
 					) {
 						Capture::Exit(Ok(trap_data)) => {
 							self.backend.push_substate();
 
-							match self.invoker.build_child_stack(trap_data, self.backend) {
-								Ok((machine, gasometer, is_static)) => LastCallStackData::Running {
-									machine,
-									gasometer,
-									is_static,
-								},
-								Err(err) => LastCallStackData::Exited {
-									machine,
-									gasometer,
-									is_static,
-									result: Capture::Exit(Err(err)),
-								},
+							match self.invoker.build_child_stack(&trap_data, self.backend) {
+								Ok((sub_machine, sub_gasometer, sub_is_static)) => {
+									self.stack.push(TrappedCallStackData {
+										trap_data,
+										machine,
+										gasometer,
+										is_static,
+									});
+
+									LastCallStackData::Running {
+										machine: sub_machine,
+										gasometer: sub_gasometer,
+										is_static: sub_is_static,
+									}
+								}
+								Err(err) => {
+									self.backend
+										.pop_substate(TransactionalMergeStrategy::Discard);
+
+									LastCallStackData::Exited {
+										machine,
+										gasometer,
+										is_static,
+										result: Capture::Exit(Err(err)),
+									}
+								}
 							}
 						}
 						Capture::Exit(Err(err)) => LastCallStackData::Exited {
@@ -260,3 +315,119 @@ where
 		(self, step_ret)
 	}
 }
+
+pub fn execute<S, H, Tr, G, I, F>(
+	mut machine: Machine<S>,
+	mut gasometer: G,
+	is_static: bool,
+	initial_depth: usize,
+	heap_depth: Option<usize>,
+	backend: &mut H,
+	invoker: &I,
+	etable: &Etable<S, H, Tr, F>,
+) -> (Machine<S>, G, ExitResult)
+where
+	G: Gasometer<S, H>,
+	H: TransactionalBackend,
+	I: Invoker<S, H, Tr, G, Interrupt = Infallible>,
+	F: Fn(&mut Machine<S>, &mut H, Opcode, usize) -> Control<Tr>,
+{
+	let mut result = run_with_gasometer(&mut machine, &mut gasometer, is_static, backend, etable);
+
+	loop {
+		match result {
+			Capture::Exit(exit) => return (machine, gasometer, exit),
+			Capture::Trap(trap) => {
+				let prepared_trap_data: Capture<Result<I::TrapData, ExitError>, Infallible> =
+					invoker.prepare_trap_data(
+						trap,
+						initial_depth + 1,
+						&mut machine,
+						&mut gasometer,
+						backend,
+					);
+
+				match prepared_trap_data {
+					Capture::Exit(Ok(trap_data)) => {
+						backend.push_substate();
+
+						match invoker.build_child_stack(&trap_data, backend) {
+							Ok((sub_machine, sub_gasometer, sub_is_static)) => {
+								let (sub_machine, sub_gasometer, sub_result) = if heap_depth
+									.map(|hd| initial_depth + 1 >= hd)
+									.unwrap_or(false)
+								{
+									let (call_stack, _infallible) = CallStack::execute(
+										sub_machine,
+										sub_gasometer,
+										sub_is_static,
+										initial_depth + 1,
+										backend,
+										invoker,
+										etable,
+									);
+
+									call_stack.expect_exit()
+								} else {
+									execute(
+										sub_machine,
+										sub_gasometer,
+										sub_is_static,
+										initial_depth + 1,
+										heap_depth,
+										backend,
+										invoker,
+										etable,
+									)
+								};
+
+								match sub_result {
+									Ok(_) => {
+										backend.pop_substate(TransactionalMergeStrategy::Commit);
+										gasometer
+											.merge(sub_gasometer, GasometerMergeStrategy::Commit);
+									}
+									Err(ExitError::Reverted) => {
+										backend.pop_substate(TransactionalMergeStrategy::Discard);
+										gasometer
+											.merge(sub_gasometer, GasometerMergeStrategy::Revert);
+									}
+									Err(_) => {
+										backend.pop_substate(TransactionalMergeStrategy::Discard);
+									}
+								}
+
+								match invoker.feedback_trap_data(
+									sub_result,
+									sub_machine,
+									trap_data,
+									&mut machine,
+									&mut gasometer,
+									backend,
+								) {
+									Ok(()) => {
+										result = run_with_gasometer(
+											&mut machine,
+											&mut gasometer,
+											is_static,
+											backend,
+											etable,
+										);
+									}
+									Err(err) => return (machine, gasometer, Err(err)),
+								}
+							}
+							Err(err) => {
+								backend.pop_substate(TransactionalMergeStrategy::Discard);
+
+								return (machine, gasometer, Err(err));
+							}
+						}
+					}
+					Capture::Exit(Err(err)) => return (machine, gasometer, Err(err)),
+					Capture::Trap(infallible) => match infallible {},
+				}
+			}
+		}
+	}
+}

src/lib.rs

@@ -7,11 +7,10 @@
 extern crate alloc;
 
 mod backend;
-mod executor;
+pub mod executor;
 
 pub use evm_gasometer as gasometer;
 pub use evm_interpreter::*;
 
 pub use crate::backend::{TransactionalBackend, TransactionalMergeStrategy};
-pub use crate::executor::{CallStack, Invoker};
 pub use crate::gasometer::Config;