Transcribe vm changes from vm_fixes by Ethan

vm/test/fake_app_state.go

@@ -1,8 +1,6 @@
 package vm
 
 import (
-	"fmt"
-
 	. "github.com/tendermint/tendermint/common"
 	. "github.com/tendermint/tendermint/vm"
 	"github.com/tendermint/tendermint/vm/sha3"
@@ -85,33 +83,6 @@ func (fas *FakeAppState) AddLog(log *Log) {
 	fas.logs = append(fas.logs, log)
 }
 
-func main() {
-	appState := &FakeAppState{
-		accounts: make(map[string]*Account),
-		storage:  make(map[string]Word256),
-		logs:     nil,
-	}
-	params := Params{
-		BlockHeight: 0,
-		BlockHash:   Zero256,
-		BlockTime:   0,
-		GasLimit:    0,
-	}
-	ourVm := NewVM(appState, params, Zero256)
-
-	// Create accounts
-	account1 := &Account{
-		Address: Uint64ToWord256(100),
-	}
-	account2 := &Account{
-		Address: Uint64ToWord256(101),
-	}
-
-	var gas uint64 = 1000
-	output, err := ourVm.Call(account1, account2, []byte{0x5B, 0x60, 0x00, 0x56}, []byte{}, 0, &gas)
-	fmt.Printf("Output: %v Error: %v\n", output, err)
-}
-
 // Creates a 20 byte address and bumps the nonce.
 func createAddress(creator *Account) Word256 {
 	nonce := creator.Nonce

vm/test/vm_test.go

@@ -0,0 +1,99 @@
+package vm
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"fmt"
+	"strings"
+	"testing"
+	"time"
+
+	. "github.com/tendermint/tendermint/common"
+	. "github.com/tendermint/tendermint/vm"
+)
+
+func newAppState() *FakeAppState {
+	return &FakeAppState{
+		accounts: make(map[string]*Account),
+		storage:  make(map[string]Word256),
+		logs:     nil,
+	}
+}
+
+func newParams() Params {
+	return Params{
+		BlockHeight: 0,
+		BlockHash:   Zero256,
+		BlockTime:   0,
+		GasLimit:    0,
+	}
+}
+
+func makeBytes(n int) []byte {
+	b := make([]byte, n)
+	rand.Read(b)
+	return b
+}
+
+func TestVM(t *testing.T) {
+	ourVm := NewVM(newAppState(), newParams(), Zero256)
+
+	// Create accounts
+	account1 := &Account{
+		Address: Uint64ToWord256(100),
+	}
+	account2 := &Account{
+		Address: Uint64ToWord256(101),
+	}
+
+	var gas uint64 = 1000
+	N := []byte{0xff, 0xff}
+	// Loop N times
+	code := []byte{0x60, 0x00, 0x60, 0x20, 0x52, 0x5B, byte(0x60 + len(N) - 1)}
+	for i := 0; i < len(N); i++ {
+		code = append(code, N[i])
+	}
+	code = append(code, []byte{0x60, 0x20, 0x51, 0x12, 0x15, 0x60, byte(0x1b + len(N)), 0x57, 0x60, 0x01, 0x60, 0x20, 0x51, 0x01, 0x60, 0x20, 0x52, 0x60, 0x05, 0x56, 0x5B}...)
+	start := time.Now()
+	output, err := ourVm.Call(account1, account2, code, []byte{}, 0, &gas)
+	fmt.Printf("Output: %v Error: %v\n", output, err)
+	fmt.Println("Call took:", time.Since(start))
+}
+
+func TestSubcurrency(t *testing.T) {
+	st := newAppState()
+	// Create accounts
+	account1 := &Account{
+		Address: RightPadWord256(makeBytes(20)),
+	}
+	account2 := &Account{
+		Address: RightPadWord256(makeBytes(20)),
+	}
+	st.accounts[account1.Address.String()] = account1
+	st.accounts[account2.Address.String()] = account2
+
+	ourVm := NewVM(st, newParams(), Zero256)
+
+	var gas uint64 = 1000
+	code_parts := []string{"620f42403355",
+		"7c0100000000000000000000000000000000000000000000000000000000",
+		"600035046315cf268481141561004657",
+		"6004356040526040515460605260206060f35b63693200ce81141561008757",
+		"60043560805260243560a052335460c0523360e05260a05160c05112151561008657",
+		"60a05160c0510360e0515560a0516080515401608051555b5b505b6000f3"}
+	code, _ := hex.DecodeString(strings.Join(code_parts, ""))
+	fmt.Printf("Code: %x\n", code)
+	data, _ := hex.DecodeString("693200CE0000000000000000000000004B4363CDE27C2EB05E66357DB05BC5C88F850C1A0000000000000000000000000000000000000000000000000000000000000005")
+	output, err := ourVm.Call(account1, account2, code, data, 0, &gas)
+	fmt.Printf("Output: %v Error: %v\n", output, err)
+
+}
+
+/*
+	// infinite loop
+	code := []byte{0x5B, 0x60, 0x00, 0x56}
+	// mstore
+	code := []byte{0x60, 0x00, 0x60, 0x20}
+	// mstore, mload
+	code := []byte{0x60, 0x01, 0x60, 0x20, 0x52, 0x60, 0x20, 0x51}
+*/

vm/vm.go

@@ -3,7 +3,7 @@ package vm
 import (
 	"errors"
 	"fmt"
-	"math"
+	"math/big"
 
 	. "github.com/tendermint/tendermint/common"
 	"github.com/tendermint/tendermint/vm/sha3"
@@ -24,12 +24,21 @@ var (
 	ErrInvalidContract     = errors.New("Invalid contract")
 )
 
+type Debug bool
+
 const (
-	dataStackCapacity = 1024
+	dataStackCapacity       = 1024
-	callStackCapacity = 100         // TODO ensure usage.
+	callStackCapacity       = 100         // TODO ensure usage.
-	memoryCapacity    = 1024 * 1024 // 1 MB
+	memoryCapacity          = 1024 * 1024 // 1 MB
+	dbg               Debug = true
 )
 
+func (d Debug) Printf(s string, a ...interface{}) {
+	if d {
+		fmt.Printf(s, a...)
+	}
+}
+
 type VM struct {
 	appState AppState
 	params   Params
@@ -74,7 +83,7 @@ func (vm *VM) Call(caller, callee *Account, code, input []byte, value uint64, ga
 
 // Just like Call() but does not transfer 'value' or modify the callDepth.
 func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, gas *uint64) (output []byte, err error) {
-	fmt.Printf("(%d) (%X) %X (code=%d) gas: %v (d) %X\n", vm.callDepth, caller.Address[:4], callee.Address, len(callee.Code), *gas, input)
+	dbg.Printf("(%d) (%X) %X (code=%d) gas: %v (d) %X\n", vm.callDepth, caller.Address[:4], callee.Address, len(callee.Code), *gas, input)
 
 	var (
 		pc     uint64 = 0
@@ -90,7 +99,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 		}
 
 		var op = codeGetOp(code, pc)
-		fmt.Printf("(pc) %-3d (op) %-14s (st) %-4d ", pc, op.String(), stack.Len())
+		dbg.Printf("(pc) %-3d (op) %-14s (st) %-4d ", pc, op.String(), stack.Len())
 
 		switch op {
 
@@ -98,90 +107,123 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			return nil, nil
 
 		case ADD: // 0x01
-			x, y := stack.Pop64(), stack.Pop64()
+			//x, y := stack.Pop64(), stack.Pop64()
-			stack.Push64(x + y)
+			//stack.Push64(x + y)
-			fmt.Printf(" %v + %v = %v\n", x, y, x+y)
+			x, y := stack.Pop(), stack.Pop()
+			xb := new(big.Int).SetBytes(flip(x[:]))
+			yb := new(big.Int).SetBytes(flip(y[:]))
+			sum := new(big.Int).Add(xb, yb)
+			stack.Push(RightPadWord256(flip(sum.Bytes())))
+			dbg.Printf(" %v + %v = %v\n", xb, yb, sum)
 
 		case MUL: // 0x02
-			x, y := stack.Pop64(), stack.Pop64()
+			//x, y := stack.Pop64(), stack.Pop64()
-			stack.Push64(x * y)
+			//stack.Push64(x * y)
-			fmt.Printf(" %v * %v = %v\n", x, y, x*y)
+			x, y := stack.Pop(), stack.Pop()
+			xb := new(big.Int).SetBytes(flip(x[:]))
+			yb := new(big.Int).SetBytes(flip(y[:]))
+			prod := new(big.Int).Mul(xb, yb)
+			stack.Push(RightPadWord256(flip(prod.Bytes())))
+			dbg.Printf(" %v * %v = %v\n", xb, yb, prod)
 
 		case SUB: // 0x03
-			x, y := stack.Pop64(), stack.Pop64()
+			//x, y := stack.Pop64(), stack.Pop64()
-			stack.Push64(x - y)
+			//stack.Push64(x - y)
-			fmt.Printf(" %v - %v = %v\n", x, y, x-y)
+			x, y := stack.Pop(), stack.Pop()
+			xb := new(big.Int).SetBytes(flip(x[:]))
+			yb := new(big.Int).SetBytes(flip(y[:]))
+			diff := new(big.Int).Sub(xb, yb)
+			stack.Push(RightPadWord256(flip(diff.Bytes())))
+			dbg.Printf(" %v - %v = %v\n", xb, yb, diff)
 
 		case DIV: // 0x04
-			x, y := stack.Pop64(), stack.Pop64()
+			//x, y := stack.Pop64(), stack.Pop64()
-			if y == 0 { // TODO
+			//stack.Push64(x / y)
+			x, y := stack.Pop(), stack.Pop()
+			if y.IsZero() { // TODO
 				stack.Push(Zero256)
-				fmt.Printf(" %v / %v = %v (TODO)\n", x, y, 0)
+				dbg.Printf(" %x / %x = %v (TODO)\n", x, y, 0)
 			} else {
-				stack.Push64(x / y)
+				xb := new(big.Int).SetBytes(flip(x[:]))
-				fmt.Printf(" %v / %v = %v\n", x, y, x/y)
+				yb := new(big.Int).SetBytes(flip(y[:]))
+				div := new(big.Int).Div(xb, yb)
+				stack.Push(RightPadWord256(flip(div.Bytes())))
+				dbg.Printf(" %v / %v = %v\n", xb, yb, div)
 			}
 
 		case SDIV: // 0x05
+			// TODO ... big?
 			x, y := int64(stack.Pop64()), int64(stack.Pop64())
 			if y == 0 { // TODO
 				stack.Push(Zero256)
-				fmt.Printf(" %v / %v = %v (TODO)\n", x, y, 0)
+				dbg.Printf(" %v / %v = %v (TODO)\n", x, y, 0)
 			} else {
 				stack.Push64(uint64(x / y))
-				fmt.Printf(" %v / %v = %v\n", x, y, x/y)
+				dbg.Printf(" %v / %v = %v\n", x, y, x/y)
 			}
 
 		case MOD: // 0x06
-			x, y := stack.Pop64(), stack.Pop64()
+			//x, y := stack.Pop64(), stack.Pop64()
-			if y == 0 { // TODO
+			x, y := stack.Pop(), stack.Pop()
+			if y.IsZero() { // TODO
 				stack.Push(Zero256)
-				fmt.Printf(" %v %% %v = %v (TODO)\n", x, y, 0)
+				dbg.Printf(" %v %% %v = %v (TODO)\n", x, y, 0)
 			} else {
-				stack.Push64(x % y)
+				xb := new(big.Int).SetBytes(flip(x[:]))
-				fmt.Printf(" %v %% %v = %v\n", x, y, x%y)
+				yb := new(big.Int).SetBytes(flip(y[:]))
+				mod := new(big.Int).Mod(xb, yb)
+				stack.Push(RightPadWord256(flip(mod.Bytes())))
+				dbg.Printf(" %v %% %v = %v\n", xb, yb, mod)
 			}
 
 		case SMOD: // 0x07
+			// TODO ... big?
 			x, y := int64(stack.Pop64()), int64(stack.Pop64())
 			if y == 0 { // TODO
 				stack.Push(Zero256)
-				fmt.Printf(" %v %% %v = %v (TODO)\n", x, y, 0)
+				dbg.Printf(" %v %% %v = %v (TODO)\n", x, y, 0)
 			} else {
 				stack.Push64(uint64(x % y))
-				fmt.Printf(" %v %% %v = %v\n", x, y, x%y)
+				dbg.Printf(" %v %% %v = %v\n", x, y, x%y)
 			}
 
 		case ADDMOD: // 0x08
+			// TODO ... big?
 			x, y, z := stack.Pop64(), stack.Pop64(), stack.Pop64()
 			if z == 0 { // TODO
 				stack.Push(Zero256)
-				fmt.Printf(" (%v + %v) %% %v = %v (TODO)\n", x, y, z, 0)
+				dbg.Printf(" (%v + %v) %% %v = %v (TODO)\n", x, y, z, 0)
 			} else {
-				stack.Push64(x % y)
+				stack.Push64((x + y) % z)
-				fmt.Printf(" (%v + %v) %% %v = %v\n", x, y, z, (x+y)%z)
+				dbg.Printf(" (%v + %v) %% %v = %v\n", x, y, z, (x+y)%z)
 			}
 
 		case MULMOD: // 0x09
+			// TODO ... big?
 			x, y, z := stack.Pop64(), stack.Pop64(), stack.Pop64()
 			if z == 0 { // TODO
 				stack.Push(Zero256)
-				fmt.Printf(" (%v + %v) %% %v = %v (TODO)\n", x, y, z, 0)
+				dbg.Printf(" (%v + %v) %% %v = %v (TODO)\n", x, y, z, 0)
 			} else {
-				stack.Push64(x % y)
+				stack.Push64((x * y) % z)
-				fmt.Printf(" (%v + %v) %% %v = %v\n", x, y, z, (x*y)%z)
+				dbg.Printf(" (%v + %v) %% %v = %v\n", x, y, z, (x*y)%z)
 			}
 
 		case EXP: // 0x0A
-			x, y := stack.Pop64(), stack.Pop64()
+			//x, y := stack.Pop64(), stack.Pop64()
-			stack.Push64(ExpUint64(x, y))
+			//stack.Push64(ExpUint64(x, y))
-			fmt.Printf(" %v ** %v = %v\n", x, y, uint64(math.Pow(float64(x), float64(y))))
+			x, y := stack.Pop(), stack.Pop()
+			xb := new(big.Int).SetBytes(flip(x[:]))
+			yb := new(big.Int).SetBytes(flip(y[:]))
+			pow := new(big.Int).Exp(xb, yb, big.NewInt(0))
+			stack.Push(RightPadWord256(flip(pow.Bytes())))
+			dbg.Printf(" %v ** %v = %v\n", xb, yb, pow)
 
 		case SIGNEXTEND: // 0x0B
 			x, y := stack.Pop64(), stack.Pop64()
 			res := (y << uint(x)) >> x
 			stack.Push64(res)
-			fmt.Printf(" (%v << %v) >> %v = %v\n", y, x, x, res)
+			dbg.Printf(" (%v << %v) >> %v = %v\n", y, x, x, res)
 
 		case LT: // 0x10
 			x, y := stack.Pop64(), stack.Pop64()
@@ -190,7 +232,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			} else {
 				stack.Push(Zero256)
 			}
-			fmt.Printf(" %v < %v = %v\n", x, y, x < y)
+			dbg.Printf(" %v < %v = %v\n", x, y, x < y)
 
 		case GT: // 0x11
 			x, y := stack.Pop64(), stack.Pop64()
@@ -199,7 +241,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			} else {
 				stack.Push(Zero256)
 			}
-			fmt.Printf(" %v > %v = %v\n", x, y, x > y)
+			dbg.Printf(" %v > %v = %v\n", x, y, x > y)
 
 		case SLT: // 0x12
 			x, y := int64(stack.Pop64()), int64(stack.Pop64())
@@ -208,7 +250,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			} else {
 				stack.Push(Zero256)
 			}
-			fmt.Printf(" %v < %v = %v\n", x, y, x < y)
+			dbg.Printf(" %v < %v = %v\n", x, y, x < y)
 
 		case SGT: // 0x13
 			x, y := int64(stack.Pop64()), int64(stack.Pop64())
@@ -217,16 +259,16 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			} else {
 				stack.Push(Zero256)
 			}
-			fmt.Printf(" %v > %v = %v\n", x, y, x > y)
+			dbg.Printf(" %v > %v = %v\n", x, y, x > y)
 
 		case EQ: // 0x14
 			x, y := stack.Pop64(), stack.Pop64()
-			if x > y {
+			if x == y {
 				stack.Push64(1)
 			} else {
 				stack.Push(Zero256)
 			}
-			fmt.Printf(" %v == %v = %v\n", x, y, x == y)
+			dbg.Printf(" %v == %v = %v\n", x, y, x == y)
 
 		case ISZERO: // 0x15
 			x := stack.Pop64()
@@ -235,27 +277,27 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			} else {
 				stack.Push(Zero256)
 			}
-			fmt.Printf(" %v == 0 = %v\n", x, x == 0)
+			dbg.Printf(" %v == 0 = %v\n", x, x == 0)
 
 		case AND: // 0x16
 			x, y := stack.Pop64(), stack.Pop64()
 			stack.Push64(x & y)
-			fmt.Printf(" %v & %v = %v\n", x, y, x&y)
+			dbg.Printf(" %v & %v = %v\n", x, y, x&y)
 
 		case OR: // 0x17
 			x, y := stack.Pop64(), stack.Pop64()
 			stack.Push64(x | y)
-			fmt.Printf(" %v | %v = %v\n", x, y, x|y)
+			dbg.Printf(" %v | %v = %v\n", x, y, x|y)
 
 		case XOR: // 0x18
 			x, y := stack.Pop64(), stack.Pop64()
 			stack.Push64(x ^ y)
-			fmt.Printf(" %v ^ %v = %v\n", x, y, x^y)
+			dbg.Printf(" %v ^ %v = %v\n", x, y, x^y)
 
 		case NOT: // 0x19
 			x := stack.Pop64()
 			stack.Push64(^x)
-			fmt.Printf(" !%v = %v\n", x, ^x)
+			dbg.Printf(" !%v = %v\n", x, ^x)
 
 		case BYTE: // 0x1A
 			idx, val := stack.Pop64(), stack.Pop()
@@ -264,7 +306,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				res = val[idx]
 			}
 			stack.Push64(uint64(res))
-			fmt.Printf(" => 0x%X\n", res)
+			dbg.Printf(" => 0x%X\n", res)
 
 		case SHA3: // 0x20
 			if ok = useGas(gas, GasSha3); !ok {
@@ -277,11 +319,11 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			}
 			data = sha3.Sha3(data)
 			stack.PushBytes(data)
-			fmt.Printf(" => (%v) %X\n", size, data)
+			dbg.Printf(" => (%v) %X\n", size, data)
 
 		case ADDRESS: // 0x30
 			stack.Push(callee.Address)
-			fmt.Printf(" => %X\n", callee.Address)
+			dbg.Printf(" => %X\n", callee.Address)
 
 		case BALANCE: // 0x31
 			addr := stack.Pop()
@@ -294,19 +336,19 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			}
 			balance := acc.Balance
 			stack.Push64(balance)
-			fmt.Printf(" => %v (%X)\n", balance, addr)
+			dbg.Printf(" => %v (%X)\n", balance, addr)
 
 		case ORIGIN: // 0x32
 			stack.Push(vm.origin)
-			fmt.Printf(" => %X\n", vm.origin)
+			dbg.Printf(" => %X\n", vm.origin)
 
 		case CALLER: // 0x33
 			stack.Push(caller.Address)
-			fmt.Printf(" => %X\n", caller.Address)
+			dbg.Printf(" => %X\n", caller.Address)
 
 		case CALLVALUE: // 0x34
 			stack.Push64(value)
-			fmt.Printf(" => %v\n", value)
+			dbg.Printf(" => %v\n", value)
 
 		case CALLDATALOAD: // 0x35
 			offset := stack.Pop64()
@@ -315,11 +357,11 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				return nil, firstErr(err, ErrInputOutOfBounds)
 			}
 			stack.Push(RightPadWord256(data))
-			fmt.Printf(" => 0x%X\n", data)
+			dbg.Printf(" => 0x%X\n", data)
 
 		case CALLDATASIZE: // 0x36
 			stack.Push64(uint64(len(input)))
-			fmt.Printf(" => %d\n", len(input))
+			dbg.Printf(" => %d\n", len(input))
 
 		case CALLDATACOPY: // 0x37
 			memOff := stack.Pop64()
@@ -334,18 +376,17 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
 			copy(dest, data)
-			fmt.Printf(" => [%v, %v, %v] %X\n", memOff, inputOff, length, data)
+			dbg.Printf(" => [%v, %v, %v] %X\n", memOff, inputOff, length, data)
 
 		case CODESIZE: // 0x38
 			l := uint64(len(code))
 			stack.Push64(l)
-			fmt.Printf(" => %d\n", l)
+			dbg.Printf(" => %d\n", l)
 
 		case CODECOPY: // 0x39
 			memOff := stack.Pop64()
 			codeOff := stack.Pop64()
 			length := stack.Pop64()
-			fmt.Println("CODECOPY: codeOff, length, codelength", codeOff, length, len(code))
 			data, ok := subslice(code, codeOff, length, false)
 			if !ok {
 				return nil, firstErr(err, ErrCodeOutOfBounds)
@@ -355,11 +396,11 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
 			copy(dest, data)
-			fmt.Printf(" => [%v, %v, %v] %X\n", memOff, codeOff, length, data)
+			dbg.Printf(" => [%v, %v, %v] %X\n", memOff, codeOff, length, data)
 
 		case GASPRICE_DEPRECATED: // 0x3A
 			stack.Push(Zero256)
-			fmt.Printf(" => %X (GASPRICE IS DEPRECATED)\n")
+			dbg.Printf(" => %X (GASPRICE IS DEPRECATED)\n")
 
 		case EXTCODESIZE: // 0x3B
 			addr := stack.Pop()
@@ -373,7 +414,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			code := acc.Code
 			l := uint64(len(code))
 			stack.Push64(l)
-			fmt.Printf(" => %d\n", l)
+			dbg.Printf(" => %d\n", l)
 
 		case EXTCODECOPY: // 0x3C
 			addr := stack.Pop()
@@ -397,33 +438,33 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
 			copy(dest, data)
-			fmt.Printf(" => [%v, %v, %v] %X\n", memOff, codeOff, length, data)
+			dbg.Printf(" => [%v, %v, %v] %X\n", memOff, codeOff, length, data)
 
 		case BLOCKHASH: // 0x40
 			stack.Push(Zero256)
-			fmt.Printf(" => 0x%X (NOT SUPPORTED)\n", stack.Peek().Bytes())
+			dbg.Printf(" => 0x%X (NOT SUPPORTED)\n", stack.Peek().Bytes())
 
 		case COINBASE: // 0x41
 			stack.Push(Zero256)
-			fmt.Printf(" => 0x%X (NOT SUPPORTED)\n", stack.Peek().Bytes())
+			dbg.Printf(" => 0x%X (NOT SUPPORTED)\n", stack.Peek().Bytes())
 
 		case TIMESTAMP: // 0x42
 			time := vm.params.BlockTime
 			stack.Push64(uint64(time))
-			fmt.Printf(" => 0x%X\n", time)
+			dbg.Printf(" => 0x%X\n", time)
 
 		case BLOCKHEIGHT: // 0x43
 			number := uint64(vm.params.BlockHeight)
 			stack.Push64(number)
-			fmt.Printf(" => 0x%X\n", number)
+			dbg.Printf(" => 0x%X\n", number)
 
 		case GASLIMIT: // 0x45
 			stack.Push64(vm.params.GasLimit)
-			fmt.Printf(" => %v\n", vm.params.GasLimit)
+			dbg.Printf(" => %v\n", vm.params.GasLimit)
 
 		case POP: // 0x50
 			stack.Pop()
-			fmt.Printf(" => %v\n", vm.params.GasLimit)
+			dbg.Printf(" => %v\n", vm.params.GasLimit)
 
 		case MLOAD: // 0x51
 			offset := stack.Pop64()
@@ -432,16 +473,16 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
 			stack.Push(RightPadWord256(data))
-			fmt.Printf(" => 0x%X\n", data)
+			dbg.Printf(" => 0x%X\n", data)
 
 		case MSTORE: // 0x52
 			offset, data := stack.Pop64(), stack.Pop()
-			dest, ok := subslice(memory, offset, 32, true)
+			dest, ok := subslice(memory, offset, 32, false)
 			if !ok {
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
-			copy(dest, data[:])
+			copy(dest, flip(data[:]))
-			fmt.Printf(" => 0x%X\n", data)
+			dbg.Printf(" => 0x%X\n", data)
 
 		case MSTORE8: // 0x53
 			offset, val := stack.Pop64(), byte(stack.Pop64()&0xFF)
@@ -449,19 +490,21 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
 			memory[offset] = val
-			fmt.Printf(" => [%v] 0x%X\n", offset, val)
+			dbg.Printf(" => [%v] 0x%X\n", offset, val)
 
 		case SLOAD: // 0x54
 			loc := stack.Pop()
 			data := vm.appState.GetStorage(callee.Address, loc)
-			stack.Push(data)
+			stack.Push(flipWord(data))
-			fmt.Printf(" {0x%X : 0x%X}\n", loc, data)
+			dbg.Printf(" {0x%X : 0x%X}\n", loc, data)
 
 		case SSTORE: // 0x55
 			loc, data := stack.Pop(), stack.Pop()
+			loc = flipWord(loc)
+			data = flipWord(data)
 			vm.appState.SetStorage(callee.Address, loc, data)
 			useGas(gas, GasStorageUpdate)
-			fmt.Printf(" {0x%X : 0x%X}\n", loc, data)
+			dbg.Printf(" {0x%X : 0x%X}\n", loc, data)
 
 		case JUMP: // 0x56
 			err = jump(code, stack.Pop64(), &pc)
@@ -473,7 +516,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				err = jump(code, pos, &pc)
 				continue
 			}
-			fmt.Printf(" ~> false\n")
+			dbg.Printf(" ~> false\n")
 
 		case PC: // 0x58
 			stack.Push64(pc)
@@ -483,10 +526,10 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 
 		case GAS: // 0x5A
 			stack.Push64(*gas)
-			fmt.Printf(" => %X\n", *gas)
+			dbg.Printf(" => %X\n", *gas)
 
 		case JUMPDEST: // 0x5B
-			fmt.Printf("\n")
+			dbg.Printf("\n")
 			// Do nothing
 
 		case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32:
@@ -498,17 +541,17 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			res := RightPadWord256(codeSegment)
 			stack.Push(res)
 			pc += a
-			fmt.Printf(" => 0x%X\n", res)
+			dbg.Printf(" => 0x%X\n", res)
 
 		case DUP1, DUP2, DUP3, DUP4, DUP5, DUP6, DUP7, DUP8, DUP9, DUP10, DUP11, DUP12, DUP13, DUP14, DUP15, DUP16:
 			n := int(op - DUP1 + 1)
 			stack.Dup(n)
-			fmt.Printf(" => [%d] 0x%X\n", n, stack.Peek().Bytes())
+			dbg.Printf(" => [%d] 0x%X\n", n, stack.Peek().Bytes())
 
 		case SWAP1, SWAP2, SWAP3, SWAP4, SWAP5, SWAP6, SWAP7, SWAP8, SWAP9, SWAP10, SWAP11, SWAP12, SWAP13, SWAP14, SWAP15, SWAP16:
 			n := int(op - SWAP1 + 2)
 			stack.Swap(n)
-			fmt.Printf(" => [%d]\n", n)
+			dbg.Printf(" => [%d]\n", n)
 
 		case LOG0, LOG1, LOG2, LOG3, LOG4:
 			n := int(op - LOG0)
@@ -528,7 +571,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 				vm.params.BlockHeight,
 			}
 			vm.appState.AddLog(log)
-			fmt.Printf(" => %v\n", log)
+			dbg.Printf(" => %v\n", log)
 
 		case CREATE: // 0xF0
 			contractValue := stack.Pop64()
@@ -560,7 +603,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			addr, value := stack.Pop(), stack.Pop64()
 			inOffset, inSize := stack.Pop64(), stack.Pop64()   // inputs
 			retOffset, retSize := stack.Pop64(), stack.Pop64() // outputs
-			fmt.Printf(" => %X\n", addr)
+			dbg.Printf(" => %X\n", addr)
 
 			// Get the arguments from the memory
 			args, ok := subslice(memory, inOffset, inSize, false)
@@ -613,7 +656,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			// Handle remaining gas.
 			*gas += gasLimit
 
-			fmt.Printf("resume %X (%v)\n", callee.Address, gas)
+			dbg.Printf("resume %X (%v)\n", callee.Address, gas)
 
 		case RETURN: // 0xF3
 			offset, size := stack.Pop64(), stack.Pop64()
@@ -621,7 +664,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			if !ok {
 				return nil, firstErr(err, ErrMemoryOutOfBounds)
 			}
-			fmt.Printf(" => [%v, %v] (%d) 0x%X\n", offset, size, len(ret), ret)
+			dbg.Printf(" => [%v, %v] (%d) 0x%X\n", offset, size, len(ret), ret)
 			return ret, nil
 
 		case SUICIDE: // 0xFF
@@ -629,7 +672,7 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			if ok = useGas(gas, GasGetAccount); !ok {
 				return nil, firstErr(err, ErrInsufficientGas)
 			}
-			// TODO if the receiver is Zero256, then make it the fee.
+			// TODO if the receiver is , then make it the fee.
 			receiver := vm.appState.GetAccount(addr)
 			if receiver == nil {
 				return nil, firstErr(err, ErrUnknownAddress)
@@ -638,11 +681,11 @@ func (vm *VM) call(caller, callee *Account, code, input []byte, value uint64, ga
 			receiver.Balance += balance
 			vm.appState.UpdateAccount(receiver)
 			vm.appState.RemoveAccount(callee)
-			fmt.Printf(" => (%X) %v\n", addr[:4], balance)
+			dbg.Printf(" => (%X) %v\n", addr[:4], balance)
 			fallthrough
 
 		default:
-			fmt.Printf("(pc) %-3v Invalid opcode %X\n", pc, op)
+			dbg.Printf("(pc) %-3v Invalid opcode %X\n", pc, op)
 			panic(fmt.Errorf("Invalid opcode %X", op))
 		}
 
@@ -677,10 +720,10 @@ func codeGetOp(code []byte, n uint64) OpCode {
 func jump(code []byte, to uint64, pc *uint64) (err error) {
 	dest := codeGetOp(code, to)
 	if dest != JUMPDEST {
-		fmt.Printf(" ~> %v invalid jump dest %v\n", to, dest)
+		dbg.Printf(" ~> %v invalid jump dest %v\n", to, dest)
 		return ErrInvalidJumpDest
 	}
-	fmt.Printf(" ~> %v\n", to)
+	dbg.Printf(" ~> %v\n", to)
 	*pc = to
 	return nil
 }
@@ -713,10 +756,25 @@ func transfer(from, to *Account, amount uint64) error {
 }
 
 func flip(in []byte) []byte {
+	l2 := len(in) / 2
 	flipped := make([]byte, len(in))
-	for i := 0; i < len(flipped)/2; i++ {
+	// copy the middle bit (if its even it will get overwritten)
+	if len(in) != 0 {
+		flipped[l2] = in[l2]
+	}
+	for i := 0; i < l2; i++ {
 		flipped[i] = in[len(in)-1-i]
 		flipped[len(in)-1-i] = in[i]
 	}
 	return flipped
 }
+
+func flipWord(in Word256) Word256 {
+	word := Word256{}
+	// copy the middle bit (if its even it will get overwritten)
+	for i := 0; i < 16; i++ {
+		word[i] = in[len(in)-1-i]
+		word[len(in)-1-i] = in[i]
+	}
+	return word
+}