VM tracing and JSON RPC endpoint for it. (#1169)

* Groundwork for basic VM tracing.

* RPC endpoint for VM tracing and ser/de types ready.

* Create VMTracer trait.

* Rearchitected VM tracing to reflect existing tracing.

Should more or less work now.

* Integrated VM tracing into JSONRPC.

* Fix ethcore module tests.

* Add tests for VM tracing.

* Fix consensus test code.

* Fix mock tests.

* Added VM trace information for post-execution stuff.

* Fix max-value calls and add "creates" field to getTransaction.

* Tests for VM tracing.

* Don't implement the trait with unimplemented.

* Remove invlaid comment.

* Fix tests.

ethcore/src/evm/ext.rs

@@ -105,4 +105,10 @@ pub trait Ext {
 
 	/// Increments sstore refunds count by 1.
 	fn inc_sstore_clears(&mut self);
+
+	/// Prepare to trace an operation. Passthrough for the VM trace.
+	fn trace_prepare_execute(&mut self, _pc: usize, _instruction: u8, _gas_cost: &U256) -> bool { false }
+
+	/// Trace the finalised execution of a single instruction.
+	fn trace_executed(&mut self, _gas_used: U256, _stack_push: &[U256], _mem_diff: Option<(usize, &[u8])>, _store_diff: Option<(U256, U256)>) {}
 }

ethcore/src/evm/instructions.rs

@@ -124,6 +124,7 @@ pub struct InstructionInfo {
 	pub side_effects: bool,
 	pub tier: GasPriceTier
 }
+
 impl InstructionInfo {
 	pub fn new(name: &'static str, additional: usize, args: usize, ret: usize, side_effects: bool, tier: GasPriceTier) -> InstructionInfo {
 		InstructionInfo {
@@ -139,7 +140,7 @@ impl InstructionInfo {
 
 #[cfg_attr(rustfmt, rustfmt_skip)]
 /// Return details about specific instruction
-pub fn get_info (instruction: Instruction) -> InstructionInfo {
+pub fn get_info(instruction: Instruction) -> InstructionInfo {
 	match instruction {
 		STOP => 		InstructionInfo::new("STOP",			0, 0, 0, true, GasPriceTier::Zero),
 		ADD => 			InstructionInfo::new("ADD",				0, 2, 1, false, GasPriceTier::VeryLow),

ethcore/src/evm/interpreter.rs

@@ -17,8 +17,9 @@
 ///! Rust VM implementation
 
 use common::*;
+use trace::VMTracer;
 use super::instructions as instructions;
-use super::instructions::Instruction;
+use super::instructions::{Instruction, get_info};
 use std::marker::Copy;
 use evm::{self, MessageCallResult, ContractCreateResult};
 
@@ -69,6 +70,8 @@ trait Stack<T> {
 	fn push(&mut self, elem: T);
 	/// Get number of elements on Stack
 	fn size(&self) -> usize;
+	/// Returns all data on stack.
+	fn peek_top(&mut self, no_of_elems: usize) -> &[T];
 }
 
 struct VecStack<S> {
@@ -131,6 +134,11 @@ impl<S : fmt::Display> Stack<S> for VecStack<S> {
 	fn size(&self) -> usize {
 		self.stack.len()
 	}
+
+	fn peek_top(&mut self, no_from_top: usize) -> &[S] {
+		assert!(self.stack.len() >= no_from_top, "peek_top asked for more items than exist.");
+		&self.stack[self.stack.len() - no_from_top .. self.stack.len()]
+	}
 }
 
 trait Memory {
@@ -293,10 +301,15 @@ impl evm::Evm for Interpreter {
 
 		while reader.position < code.len() {
 			let instruction = code[reader.position];
-			reader.position += 1;
 
 			// Calculate gas cost
 			let (gas_cost, mem_size) = try!(self.get_gas_cost_mem(ext, instruction, &mut mem, &stack));
+
+			// TODO: make compile-time removable if too much of a performance hit.
+			let trace_executed = ext.trace_prepare_execute(reader.position, instruction, &gas_cost);
+
+			reader.position += 1;
+
 			try!(self.verify_gas(&current_gas, &gas_cost));
 			mem.expand(mem_size);
 			current_gas = current_gas - gas_cost; //TODO: use operator -=
@@ -311,10 +324,19 @@ impl evm::Evm for Interpreter {
 				);
 			});
 
+			let (mem_written, store_written) = match trace_executed {
+				true => (Self::mem_written(instruction, &stack), Self::store_written(instruction, &stack)),
+				false => (None, None),
+			};
+
 			// Execute instruction
 			let result = try!(self.exec_instruction(
 					current_gas, &params, ext, instruction, &mut reader, &mut mem, &mut stack
-					));
+			));
+
+			if trace_executed {
+				ext.trace_executed(current_gas, stack.peek_top(get_info(instruction).ret), mem_written.map(|(o, s)| (o, &(mem[o..(o + s)]))), store_written);
+			}
 
 			// Advance
 			match result {
@@ -485,6 +507,31 @@ impl Interpreter {
 		}
 	}
 
+	fn mem_written(
+		instruction: Instruction,
+		stack: &Stack<U256>
+	) -> Option<(usize, usize)> {
+		match instruction {
+			instructions::MSTORE | instructions::MLOAD => Some((stack.peek(0).low_u64() as usize, 32)),
+			instructions::MSTORE8 => Some((stack.peek(0).low_u64() as usize, 1)),
+			instructions::CALLDATACOPY | instructions::CODECOPY => Some((stack.peek(0).low_u64() as usize, stack.peek(2).low_u64() as usize)),
+			instructions::EXTCODECOPY => Some((stack.peek(1).low_u64() as usize, stack.peek(3).low_u64() as usize)),
+			instructions::CALL | instructions::CALLCODE => Some((stack.peek(5).low_u64() as usize, stack.peek(6).low_u64() as usize)),
+			instructions::DELEGATECALL => Some((stack.peek(4).low_u64() as usize, stack.peek(5).low_u64() as usize)),
+			_ => None,
+		}
+	}
+
+	fn store_written(
+		instruction: Instruction,
+		stack: &Stack<U256>
+	) -> Option<(U256, U256)> {
+		match instruction {
+			instructions::SSTORE => Some((stack.peek(0).clone(), stack.peek(1).clone())),
+			_ => None,
+		}
+	}
+
 	fn mem_gas_cost(&self, schedule: &evm::Schedule, current_mem_size: usize, mem_size: &U256) -> Result<(U256, usize), evm::Error> {
 		let gas_for_mem = |mem_size: U256| {
 			let s = mem_size >> 5;
@@ -833,10 +880,12 @@ impl Interpreter {
 		}
 	}
 
-	fn verify_instructions_requirements(&self,
-										info: &instructions::InstructionInfo,
-										stack_limit: usize,
-										stack: &Stack<U256>) -> Result<(), evm::Error> {
+	fn verify_instructions_requirements(
+		&self,
+		info: &instructions::InstructionInfo,
+		stack_limit: usize,
+		stack: &Stack<U256>
+	) -> Result<(), evm::Error> {
 		if !stack.has(info.args) {
 			Err(evm::Error::StackUnderflow {
 				instruction: info.name,

ethcore/src/evm/jit.rs

@@ -16,6 +16,7 @@
 
 //! Just in time compiler execution environment.
 use common::*;
+use trace::VMTracer;
 use evmjit;
 use evm;
 

ethcore/src/evm/mod.rs

@@ -33,3 +33,4 @@ pub use self::evm::{Evm, Error, Result};
 pub use self::ext::{Ext, ContractCreateResult, MessageCallResult};
 pub use self::factory::{Factory, VMType};
 pub use self::schedule::Schedule;
+pub use self::instructions::get_info;