core/vm: implement RETURNDATA metropolis opcodes

core/vm/gas_table.go

@@ -91,6 +91,32 @@ func gasCalldataCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *St
 	return gas, nil
 }
 
+func gasReturnDataCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
+	gas, err := memoryGasCost(mem, memorySize)
+	if err != nil {
+		return 0, err
+	}
+
+	var overflow bool
+	if gas, overflow = math.SafeAdd(gas, GasFastestStep); overflow {
+		return 0, errGasUintOverflow
+	}
+
+	words, overflow := bigUint64(stack.Back(2))
+	if overflow {
+		return 0, errGasUintOverflow
+	}
+
+	if words, overflow = math.SafeMul(toWordSize(words), params.CopyGas); overflow {
+		return 0, errGasUintOverflow
+	}
+
+	if gas, overflow = math.SafeAdd(gas, words); overflow {
+		return 0, errGasUintOverflow
+	}
+	return gas, nil
+}
+
 func gasSStore(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
 	var (
 		y, x = stack.Back(1), stack.Back(0)

core/vm/instructions.go

@@ -31,6 +31,7 @@ import (
 var (
 	bigZero            = new(big.Int)
 	errWriteProtection = errors.New("evm: write protection")
+	errReadOutOfBound  = errors.New("evm: read out of bound")
 )
 
 func opAdd(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
@@ -360,6 +361,28 @@ func opCalldataCopy(pc *uint64, evm *EVM, contract *Contract, memory *Memory, st
 	return nil, nil
 }
 
+func opReturnDataSize(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
+	stack.push(evm.interpreter.intPool.get().SetUint64(uint64(len(evm.interpreter.returnData))))
+	return nil, nil
+}
+
+func opReturnDataCopy(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
+	var (
+		mOff = stack.pop()
+		cOff = stack.pop()
+		l    = stack.pop()
+	)
+	defer evm.interpreter.intPool.put(mOff, cOff, l)
+
+	cEnd := new(big.Int).Add(cOff, l)
+	if cEnd.BitLen() > 64 || uint64(len(evm.interpreter.returnData)) < cEnd.Uint64() {
+		return nil, errReadOutOfBound
+	}
+	memory.Set(mOff.Uint64(), l.Uint64(), evm.interpreter.returnData[cOff.Uint64():cEnd.Uint64()])
+
+	return nil, nil
+}
+
 func opExtCodeSize(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
 	a := stack.pop()
 

core/vm/interpreter.go

@@ -60,6 +60,8 @@ type Interpreter struct {
 	intPool  *intPool
 
 	readonly bool
+	// returnData contains the last call's return data
+	returnData []byte
 }
 
 // NewInterpreter returns a new instance of the Interpreter.
@@ -113,6 +115,10 @@ func (in *Interpreter) Run(snapshot int, contract *Contract, input []byte) (ret
 	in.evm.depth++
 	defer func() { in.evm.depth-- }()
 
+	// Reset the previous call's return data. It's unimportant to preserve the old buffer
+	// as every returning call will return new data anyway.
+	in.returnData = nil
+
 	// Don't bother with the execution if there's no code.
 	if len(contract.Code) == 0 {
 		return nil, nil
@@ -213,10 +219,10 @@ func (in *Interpreter) Run(snapshot int, contract *Contract, input []byte) (ret
 		case !operation.jumps:
 			pc++
 		}
-		// if the operation returned a value make sure that is also set
-		// the last return data.
-		if res != nil {
-			mem.lastReturn = ret
+		// if the operation clears the return data (e.g. it has returning data)
+		// set the last return to the result of the operation.
+		if operation.clearsReturndata {
+			in.returnData = res
 		}
 	}
 	return nil, nil

core/vm/jump_table.go

@@ -53,6 +53,8 @@ type operation struct {
 	valid bool
 	// reverts determined whether the operation reverts state
 	reverts bool
+	// clearsReturndata determines whether the opertions clears the return data
+	clearsReturndata bool
 }
 
 var (
@@ -73,6 +75,19 @@ func NewMetropolisInstructionSet() [256]operation {
 		memorySize:    memoryStaticCall,
 		valid:         true,
 	}
+	instructionSet[RETURNDATASIZE] = operation{
+		execute:       opReturnDataSize,
+		gasCost:       constGasFunc(GasQuickStep),
+		validateStack: makeStackFunc(0, 1),
+		valid:         true,
+	}
+	instructionSet[RETURNDATACOPY] = operation{
+		execute:       opReturnDataCopy,
+		gasCost:       gasReturnDataCopy,
+		validateStack: makeStackFunc(3, 0),
+		memorySize:    memoryReturnDataCopy,
+		valid:         true,
+	}
 	return instructionSet
 }
 
@@ -861,26 +876,29 @@ func NewFrontierInstructionSet() [256]operation {
 			writes:        true,
 		},
 		CREATE: {
-			execute:       opCreate,
-			gasCost:       gasCreate,
-			validateStack: makeStackFunc(3, 1),
-			memorySize:    memoryCreate,
-			valid:         true,
-			writes:        true,
+			execute:          opCreate,
+			gasCost:          gasCreate,
+			validateStack:    makeStackFunc(3, 1),
+			memorySize:       memoryCreate,
+			valid:            true,
+			writes:           true,
+			clearsReturndata: true,
 		},
 		CALL: {
-			execute:       opCall,
-			gasCost:       gasCall,
-			validateStack: makeStackFunc(7, 1),
-			memorySize:    memoryCall,
-			valid:         true,
+			execute:          opCall,
+			gasCost:          gasCall,
+			validateStack:    makeStackFunc(7, 1),
+			memorySize:       memoryCall,
+			valid:            true,
+			clearsReturndata: true,
 		},
 		CALLCODE: {
-			execute:       opCallCode,
-			gasCost:       gasCallCode,
-			validateStack: makeStackFunc(7, 1),
-			memorySize:    memoryCall,
-			valid:         true,
+			execute:          opCallCode,
+			gasCost:          gasCallCode,
+			validateStack:    makeStackFunc(7, 1),
+			memorySize:       memoryCall,
+			valid:            true,
+			clearsReturndata: true,
 		},
 		RETURN: {
 			execute:       opReturn,

core/vm/memory_table.go

@@ -30,6 +30,10 @@ func memoryCalldataCopy(stack *Stack) *big.Int {
 	return calcMemSize(stack.Back(0), stack.Back(2))
 }
 
+func memoryReturnDataCopy(stack *Stack) *big.Int {
+	return calcMemSize(stack.Back(0), stack.Back(2))
+}
+
 func memoryCodeCopy(stack *Stack) *big.Int {
 	return calcMemSize(stack.Back(0), stack.Back(2))
 }