fix opcode xtuck panic

vm/neovm/func_flowcontrol.go

@@ -78,7 +78,7 @@ func opDCALL(e *ExecutionEngine) (VMState, error) {
 		return FAULT, errors.ERR_DCALL_OFFSET_ERROR
 	}
 
-	if dest.Sign() < 0 || dest.Cmp(big.NewInt(int64(len(e.Context.Code)))) > 0 {
+	if dest.Sign() < 0 || dest.Cmp(big.NewInt(int64(len(e.Context.Code)))) >= 0 {
 		return FAULT, errors.ERR_DCALL_OFFSET_ERROR
 	}
 

vm/neovm/func_stack_test.go

@@ -141,10 +141,10 @@ func TestOpXTuck(t *testing.T) {
 	stack.Push(types.NewInteger(big.NewInt(8888)))
 	stack.Push(types.NewInteger(big.NewInt(7777)))
 
-	stack.Push(NewStackItem(types.NewInteger(big.NewInt(2))))
+	stack.Push(NewStackItem(types.NewInteger(big.NewInt(0))))
 	e.EvaluationStack = stack
 
-	opXSwap(&e)
+	opXTuck(&e)
 	v1, err := stack.Peek(0).GetBigInteger()
 	if err != nil {
 		t.Fatal("NeoVM OpXTuck test failed.")
@@ -156,7 +156,7 @@ func TestOpXTuck(t *testing.T) {
 	e1 := v1.Int64()
 	e2 := v2.Int64()
 
-	if stack.Count() != 3 || e1 != 9999 || e2 != 7777 {
+	if stack.Count() != 4 || e1 != 7777 || e2 != 8888 {
 		t.Fatal("NeoVM OpXTuck test failed.")
 	}
 }

vm/neovm/func_validate.go

@@ -157,7 +157,20 @@ func validateXSwap(e *ExecutionEngine) error {
 }
 
 func validateXTuck(e *ExecutionEngine) error {
-	return validateOpStack(e, "[validateXTuck]")
+	total := EvaluationStackCount(e)
+	if total < 1 {
+		return errors.ERR_UNDER_STACK_LEN
+	}
+	index, err := PeekBigInteger(e)
+	if err != nil {
+		return err
+	}
+	count := big.NewInt(0)
+	if index.Sign() < 0 || count.Add(index, big.NewInt(1)).Cmp(big.NewInt(int64(total))) > 0 {
+		return errors.ERR_BAD_VALUE
+	}
+
+	return nil
 }
 
 func validatePick(e *ExecutionEngine) error {

vm/neovm/stack.go

@@ -47,8 +47,8 @@ func (r *RandomAccessStack) Insert(index int, t types.StackItems) {
 		return
 	}
 	index = l - index
-	r.e = append(r.e, r.e[l-1])
-	copy(r.e[index+1:l], r.e[index:])
+	r.e = append(r.e, t)
+	copy(r.e[index+1:], r.e[index:])
 	r.e[index] = t
 }