core/vm: Move interpreter.ReadOnly check into the opcode implementations

Also remove the same check from the interpreter inner loop.

core/vm/instructions.go

@@ -514,6 +514,10 @@ func opSload(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]by
 }
 
 func opSstore(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
+	if interpreter.readOnly {
+		return nil, ErrWriteProtection
+	}
+
 	loc := scope.Stack.pop()
 	val := scope.Stack.pop()
 	interpreter.evm.StateDB.SetState(scope.Contract.Address(),
@@ -563,12 +567,17 @@ func opGas(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte
 }
 
 func opCreate(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
+	if interpreter.readOnly {
+		return nil, ErrWriteProtection
+	}
+
 	var (
 		value        = scope.Stack.pop()
 		offset, size = scope.Stack.pop(), scope.Stack.pop()
 		input        = scope.Memory.GetCopy(int64(offset.Uint64()), int64(size.Uint64()))
 		gas          = scope.Contract.Gas
 	)
+
 	if interpreter.evm.chainRules.IsEIP150 {
 		gas -= gas / 64
 	}
@@ -604,6 +613,10 @@ func opCreate(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]b
 }
 
 func opCreate2(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
+	if interpreter.readOnly {
+		return nil, ErrWriteProtection
+	}
+
 	var (
 		endowment    = scope.Stack.pop()
 		offset, size = scope.Stack.pop(), scope.Stack.pop()
@@ -640,6 +653,10 @@ func opCreate2(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]
 }
 
 func opCall(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
+	if interpreter.readOnly && !value.IsZero() {
+		return nil, ErrWriteProtection
+	}
+
 	stack := scope.Stack
 	// Pop gas. The actual gas in interpreter.evm.callGasTemp.
 	// We can use this as a temporary value
@@ -787,6 +804,10 @@ func opStop(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byt
 }
 
 func opSuicide(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
+	if interpreter.readOnly {
+		return nil, ErrWriteProtection
+	}
+
 	beneficiary := scope.Stack.pop()
 	balance := interpreter.evm.StateDB.GetBalance(scope.Contract.Address())
 	interpreter.evm.StateDB.AddBalance(beneficiary.Bytes20(), balance)
@@ -803,6 +824,10 @@ func opSuicide(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]
 // make log instruction function
 func makeLog(size int) executionFunc {
 	return func(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
+		if interpreter.readOnly {
+			return nil, ErrWriteProtection
+		}
+
 		topics := make([]common.Hash, size)
 		stack := scope.Stack
 		mStart, mSize := stack.pop(), stack.pop()

core/vm/interpreter.go

@@ -124,6 +124,9 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 	// Make sure the readOnly is only set if we aren't in readOnly yet.
 	// This also makes sure that the readOnly flag isn't removed for child calls.
 	if readOnly && !in.readOnly {
+		if !in.evm.chainRules.IsByzantium {
+			panic("readOnly execution requested on wrong chainRules")
+		}
 		in.readOnly = true
 		defer func() { in.readOnly = false }()
 	}
@@ -204,17 +207,6 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 		} else if sLen > operation.maxStack {
 			return nil, &ErrStackOverflow{stackLen: sLen, limit: operation.maxStack}
 		}
-		// If the operation is valid, enforce write restrictions
-		if in.readOnly && in.evm.chainRules.IsByzantium {
-			// If the interpreter is operating in readonly mode, make sure no
-			// state-modifying operation is performed. The 3rd stack item
-			// for a call operation is the value. Transferring value from one
-			// account to the others means the state is modified and should also
-			// return with an error.
-			if operation.writes || (op == CALL && stack.Back(2).Sign() != 0) {
-				return nil, ErrWriteProtection
-			}
-		}
 		// Static portion of gas
 		cost = operation.constantGas // For tracing
 		if !contract.UseGas(operation.constantGas) {