Merge pull request #2116 from obscuren/homestead

core, core/vm: consensus changes necessary for the homestead release

27 files changed, 484 insertions, 180 deletions

diff --git a/core/bench_test.go b/core/bench_test.go
index 6fa7659b9..f991e5e7f 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -82,7 +82,7 @@ func genValueTx(nbytes int) func(int, *BlockGen) {
 	return func(i int, gen *BlockGen) {
 		toaddr := common.Address{}
 		data := make([]byte, nbytes)
-		gas := IntrinsicGas(data)
+		gas := IntrinsicGas(data, false, false)
 		tx, _ := types.NewTransaction(gen.TxNonce(benchRootAddr), toaddr, big.NewInt(1), gas, nil, data).SignECDSA(benchRootKey)
 		gen.AddTx(tx)
 	}
diff --git a/core/block_validator.go b/core/block_validator.go
index 62d096d02..73c33d8dd 100644
--- a/core/block_validator.go
+++ b/core/block_validator.go
@@ -30,6 +30,12 @@ import (
 	"gopkg.in/fatih/set.v0"
 )
 
+var (
+	ExpDiffPeriod = big.NewInt(100000)
+	big10         = big.NewInt(10)
+	bigMinus99    = big.NewInt(-99)
+)
+
 // BlockValidator is responsible for validating block headers, uncles and
 // processed state.
 //
@@ -111,7 +117,7 @@ func (v *BlockValidator) ValidateState(block, parent *types.Block, statedb *stat
 	// For valid blocks this should always validate to true.
 	rbloom := types.CreateBloom(receipts)
 	if rbloom != header.Bloom {
-		return fmt.Errorf("unable to replicate block's bloom=%x", rbloom)
+		return fmt.Errorf("unable to replicate block's bloom=%x vs calculated bloom=%x", header.Bloom, rbloom)
 	}
 	// Tre receipt Trie's root (R = (Tr [[H1, R1], ... [Hn, R1]]))
 	receiptSha := types.DeriveSha(receipts)
@@ -241,3 +247,127 @@ func ValidateHeader(pow pow.PoW, header *types.Header, parent *types.Header, che
 	}
 	return nil
 }
+
+// CalcDifficulty is the difficulty adjustment algorithm. It returns
+// the difficulty that a new block should have when created at time
+// given the parent block's time and difficulty.
+func CalcDifficulty(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
+	if params.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
+		return calcDifficultyHomestead(time, parentTime, parentNumber, parentDiff)
+	} else {
+		return calcDifficultyFrontier(time, parentTime, parentNumber, parentDiff)
+	}
+}
+
+func calcDifficultyHomestead(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
+	// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
+	// algorithm:
+	// diff = (parent_diff +
+	//         (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
+	//        ) + 2^(periodCount - 2)
+
+	bigTime := new(big.Int).SetUint64(time)
+	bigParentTime := new(big.Int).SetUint64(parentTime)
+
+	// holds intermediate values to make the algo easier to read & audit
+	x := new(big.Int)
+	y := new(big.Int)
+
+	// 1 - (block_timestamp -parent_timestamp) // 10
+	x.Sub(bigTime, bigParentTime)
+	x.Div(x, big10)
+	x.Sub(common.Big1, x)
+
+	// max(1 - (block_timestamp - parent_timestamp) // 10, -99)))
+	if x.Cmp(bigMinus99) < 0 {
+		x.Set(bigMinus99)
+	}
+
+	// (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99))
+	y.Div(parentDiff, params.DifficultyBoundDivisor)
+	x.Mul(y, x)
+	x.Add(parentDiff, x)
+
+	// minimum difficulty can ever be (before exponential factor)
+	if x.Cmp(params.MinimumDifficulty) < 0 {
+		x = params.MinimumDifficulty
+	}
+
+	// for the exponential factor
+	periodCount := new(big.Int).Add(parentNumber, common.Big1)
+	periodCount.Div(periodCount, ExpDiffPeriod)
+
+	// the exponential factor, commonly refered to as "the bomb"
+	// diff = diff + 2^(periodCount - 2)
+	if periodCount.Cmp(common.Big1) > 0 {
+		y.Sub(periodCount, common.Big2)
+		y.Exp(common.Big2, y, nil)
+		x.Add(x, y)
+	}
+
+	return x
+}
+
+func calcDifficultyFrontier(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
+	diff := new(big.Int)
+	adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
+	bigTime := new(big.Int)
+	bigParentTime := new(big.Int)
+
+	bigTime.SetUint64(time)
+	bigParentTime.SetUint64(parentTime)
+
+	if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 {
+		diff.Add(parentDiff, adjust)
+	} else {
+		diff.Sub(parentDiff, adjust)
+	}
+	if diff.Cmp(params.MinimumDifficulty) < 0 {
+		diff = params.MinimumDifficulty
+	}
+
+	periodCount := new(big.Int).Add(parentNumber, common.Big1)
+	periodCount.Div(periodCount, ExpDiffPeriod)
+	if periodCount.Cmp(common.Big1) > 0 {
+		// diff = diff + 2^(periodCount - 2)
+		expDiff := periodCount.Sub(periodCount, common.Big2)
+		expDiff.Exp(common.Big2, expDiff, nil)
+		diff.Add(diff, expDiff)
+		diff = common.BigMax(diff, params.MinimumDifficulty)
+	}
+
+	return diff
+}
+
+// CalcGasLimit computes the gas limit of the next block after parent.
+// The result may be modified by the caller.
+// This is miner strategy, not consensus protocol.
+func CalcGasLimit(parent *types.Block) *big.Int {
+	// contrib = (parentGasUsed * 3 / 2) / 1024
+	contrib := new(big.Int).Mul(parent.GasUsed(), big.NewInt(3))
+	contrib = contrib.Div(contrib, big.NewInt(2))
+	contrib = contrib.Div(contrib, params.GasLimitBoundDivisor)
+
+	// decay = parentGasLimit / 1024 -1
+	decay := new(big.Int).Div(parent.GasLimit(), params.GasLimitBoundDivisor)
+	decay.Sub(decay, big.NewInt(1))
+
+	/*
+		strategy: gasLimit of block-to-mine is set based on parent's
+		gasUsed value.  if parentGasUsed > parentGasLimit * (2/3) then we
+		increase it, otherwise lower it (or leave it unchanged if it's right
+		at that usage) the amount increased/decreased depends on how far away
+		from parentGasLimit * (2/3) parentGasUsed is.
+	*/
+	gl := new(big.Int).Sub(parent.GasLimit(), decay)
+	gl = gl.Add(gl, contrib)
+	gl.Set(common.BigMax(gl, params.MinGasLimit))
+
+	// however, if we're now below the target (GenesisGasLimit) we increase the
+	// limit as much as we can (parentGasLimit / 1024 -1)
+	if gl.Cmp(params.GenesisGasLimit) < 0 {
+		gl.Add(parent.GasLimit(), decay)
+		gl.Set(common.BigMin(gl, params.GenesisGasLimit))
+	}
+	return gl
+}
diff --git a/core/blockchain.go b/core/blockchain.go
index 22dd617ad..2c6ff24f9 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -725,14 +725,18 @@ func (self *BlockChain) writeHeader(header *types.Header) error {
 	if ptd == nil {
 		return ParentError(header.ParentHash)
 	}
-	td := new(big.Int).Add(header.Difficulty, ptd)
+
+	localTd := self.GetTd(self.currentHeader.Hash())
+	externTd := new(big.Int).Add(header.Difficulty, ptd)
 
 	// Make sure no inconsistent state is leaked during insertion
 	self.mu.Lock()
 	defer self.mu.Unlock()
 
 	// If the total difficulty is higher than our known, add it to the canonical chain
-	if td.Cmp(self.GetTd(self.currentHeader.Hash())) > 0 {
+	// Second clause in the if statement reduces the vulnerability to selfish mining.
+	// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
+	if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
 		// Delete any canonical number assignments above the new head
 		for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
 			DeleteCanonicalHash(self.chainDb, i)
@@ -753,7 +757,7 @@ func (self *BlockChain) writeHeader(header *types.Header) error {
 		self.currentHeader = types.CopyHeader(header)
 	}
 	// Irrelevant of the canonical status, write the header itself to the database
-	if err := WriteTd(self.chainDb, header.Hash(), td); err != nil {
+	if err := WriteTd(self.chainDb, header.Hash(), externTd); err != nil {
 		glog.Fatalf("failed to write header total difficulty: %v", err)
 	}
 	if err := WriteHeader(self.chainDb, header); err != nil {
@@ -1060,14 +1064,18 @@ func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err
 	if ptd == nil {
 		return NonStatTy, ParentError(block.ParentHash())
 	}
-	td := new(big.Int).Add(block.Difficulty(), ptd)
+
+	localTd := self.GetTd(self.currentBlock.Hash())
+	externTd := new(big.Int).Add(block.Difficulty(), ptd)
 
 	// Make sure no inconsistent state is leaked during insertion
 	self.mu.Lock()
 	defer self.mu.Unlock()
 
 	// If the total difficulty is higher than our known, add it to the canonical chain
-	if td.Cmp(self.GetTd(self.currentBlock.Hash())) > 0 {
+	// Second clause in the if statement reduces the vulnerability to selfish mining.
+	// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
+	if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
 		// Reorganize the chain if the parent is not the head block
 		if block.ParentHash() != self.currentBlock.Hash() {
 			if err := self.reorg(self.currentBlock, block); err != nil {
@@ -1081,7 +1089,7 @@ func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err
 		status = SideStatTy
 	}
 	// Irrelevant of the canonical status, write the block itself to the database
-	if err := WriteTd(self.chainDb, block.Hash(), td); err != nil {
+	if err := WriteTd(self.chainDb, block.Hash(), externTd); err != nil {
 		glog.Fatalf("failed to write block total difficulty: %v", err)
 	}
 	if err := WriteBlock(self.chainDb, block); err != nil {
diff --git a/core/database_util.go b/core/database_util.go
index 2dc113e29..fd2b4c312 100644
--- a/core/database_util.go
+++ b/core/database_util.go
@@ -27,7 +27,6 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
-	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
@@ -50,77 +49,9 @@ var (
 	mipmapPre    = []byte("mipmap-log-bloom-")
 	MIPMapLevels = []uint64{1000000, 500000, 100000, 50000, 1000}
 
-	ExpDiffPeriod   = big.NewInt(100000)
 	blockHashPrefix = []byte("block-hash-") // [deprecated by the header/block split, remove eventually]
 )
 
-// CalcDifficulty is the difficulty adjustment algorithm. It returns
-// the difficulty that a new block b should have when created at time
-// given the parent block's time and difficulty.
-func CalcDifficulty(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
-	diff := new(big.Int)
-	adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
-	bigTime := new(big.Int)
-	bigParentTime := new(big.Int)
-
-	bigTime.SetUint64(time)
-	bigParentTime.SetUint64(parentTime)
-
-	if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 {
-		diff.Add(parentDiff, adjust)
-	} else {
-		diff.Sub(parentDiff, adjust)
-	}
-	if diff.Cmp(params.MinimumDifficulty) < 0 {
-		diff = params.MinimumDifficulty
-	}
-
-	periodCount := new(big.Int).Add(parentNumber, common.Big1)
-	periodCount.Div(periodCount, ExpDiffPeriod)
-	if periodCount.Cmp(common.Big1) > 0 {
-		// diff = diff + 2^(periodCount - 2)
-		expDiff := periodCount.Sub(periodCount, common.Big2)
-		expDiff.Exp(common.Big2, expDiff, nil)
-		diff.Add(diff, expDiff)
-		diff = common.BigMax(diff, params.MinimumDifficulty)
-	}
-
-	return diff
-}
-
-// CalcGasLimit computes the gas limit of the next block after parent.
-// The result may be modified by the caller.
-// This is miner strategy, not consensus protocol.
-func CalcGasLimit(parent *types.Block) *big.Int {
-	// contrib = (parentGasUsed * 3 / 2) / 1024
-	contrib := new(big.Int).Mul(parent.GasUsed(), big.NewInt(3))
-	contrib = contrib.Div(contrib, big.NewInt(2))
-	contrib = contrib.Div(contrib, params.GasLimitBoundDivisor)
-
-	// decay = parentGasLimit / 1024 -1
-	decay := new(big.Int).Div(parent.GasLimit(), params.GasLimitBoundDivisor)
-	decay.Sub(decay, big.NewInt(1))
-
-	/*
-		strategy: gasLimit of block-to-mine is set based on parent's
-		gasUsed value.  if parentGasUsed > parentGasLimit * (2/3) then we
-		increase it, otherwise lower it (or leave it unchanged if it's right
-		at that usage) the amount increased/decreased depends on how far away
-		from parentGasLimit * (2/3) parentGasUsed is.
-	*/
-	gl := new(big.Int).Sub(parent.GasLimit(), decay)
-	gl = gl.Add(gl, contrib)
-	gl.Set(common.BigMax(gl, params.MinGasLimit))
-
-	// however, if we're now below the target (GenesisGasLimit) we increase the
-	// limit as much as we can (parentGasLimit / 1024 -1)
-	if gl.Cmp(params.GenesisGasLimit) < 0 {
-		gl.Add(parent.GasLimit(), decay)
-		gl.Set(common.BigMin(gl, params.GenesisGasLimit))
-	}
-	return gl
-}
-
 // GetCanonicalHash retrieves a hash assigned to a canonical block number.
 func GetCanonicalHash(db ethdb.Database, number uint64) common.Hash {
 	data, _ := db.Get(append(blockNumPrefix, big.NewInt(int64(number)).Bytes()...))
diff --git a/core/database_util_test.go b/core/database_util_test.go
index 059f1ae9f..6b3793635 100644
--- a/core/database_util_test.go
+++ b/core/database_util_test.go
@@ -62,7 +62,7 @@ func (d *diffTest) UnmarshalJSON(b []byte) (err error) {
 	return nil
 }
 
-func TestDifficulty(t *testing.T) {
+func TestDifficultyFrontier(t *testing.T) {
 	file, err := os.Open("../tests/files/BasicTests/difficulty.json")
 	if err != nil {
 		t.Fatal(err)
@@ -77,7 +77,7 @@ func TestDifficulty(t *testing.T) {
 
 	for name, test := range tests {
 		number := new(big.Int).Sub(test.CurrentBlocknumber, big.NewInt(1))
-		diff := CalcDifficulty(test.CurrentTimestamp, test.ParentTimestamp, number, test.ParentDifficulty)
+		diff := calcDifficultyFrontier(test.CurrentTimestamp, test.ParentTimestamp, number, test.ParentDifficulty)
 		if diff.Cmp(test.CurrentDifficulty) != 0 {
 			t.Error(name, "failed. Expected", test.CurrentDifficulty, "and calculated", diff)
 		}
diff --git a/core/execution.go b/core/execution.go
index fd8464f6e..24c0c93ae 100644
--- a/core/execution.go
+++ b/core/execution.go
@@ -33,8 +33,17 @@ func Call(env vm.Environment, caller vm.ContractRef, addr common.Address, input
 
 // CallCode executes the given address' code as the given contract address
 func CallCode(env vm.Environment, caller vm.ContractRef, addr common.Address, input []byte, gas, gasPrice, value *big.Int) (ret []byte, err error) {
-	prev := caller.Address()
-	ret, _, err = exec(env, caller, &prev, &addr, input, env.Db().GetCode(addr), gas, gasPrice, value)
+	callerAddr := caller.Address()
+	ret, _, err = exec(env, caller, &callerAddr, &addr, input, env.Db().GetCode(addr), gas, gasPrice, value)
+	return ret, err
+}
+
+// DelegateCall is equivalent to CallCode except that sender and value propagates from parent scope to child scope
+func DelegateCall(env vm.Environment, caller vm.ContractRef, addr common.Address, input []byte, gas, gasPrice *big.Int) (ret []byte, err error) {
+	callerAddr := caller.Address()
+	originAddr := env.Origin()
+	callerValue := caller.Value()
+	ret, _, err = execDelegateCall(env, caller, &originAddr, &callerAddr, &addr, input, env.Db().GetCode(addr), gas, gasPrice, callerValue)
 	return ret, err
 }
 
@@ -52,7 +61,6 @@ func Create(env vm.Environment, caller vm.ContractRef, code []byte, gas, gasPric
 
 func exec(env vm.Environment, caller vm.ContractRef, address, codeAddr *common.Address, input, code []byte, gas, gasPrice, value *big.Int) (ret []byte, addr common.Address, err error) {
 	evm := vm.NewVm(env)
-
 	// Depth check execution. Fail if we're trying to execute above the
 	// limit.
 	if env.Depth() > int(params.CallCreateDepth.Int64()) {
@@ -69,17 +77,15 @@ func exec(env vm.Environment, caller vm.ContractRef, address, codeAddr *common.A
 
 	var createAccount bool
 	if address == nil {
-		// Generate a new address
+		// Create a new account on the state
 		nonce := env.Db().GetNonce(caller.Address())
 		env.Db().SetNonce(caller.Address(), nonce+1)
-
 		addr = crypto.CreateAddress(caller.Address(), nonce)
-
 		address = &addr
 		createAccount = true
 	}
-	snapshot := env.MakeSnapshot()
 
+	snapshotPreTransfer := env.MakeSnapshot()
 	var (
 		from = env.Db().GetAccount(caller.Address())
 		to   vm.Account
@@ -95,12 +101,68 @@ func exec(env vm.Environment, caller vm.ContractRef, address, codeAddr *common.A
 	}
 	env.Transfer(from, to, value)
 
+	// initialise a new contract and set the code that is to be used by the
+	// EVM. The contract is a scoped environment for this execution context
+	// only.
 	contract := vm.NewContract(caller, to, value, gas, gasPrice)
 	contract.SetCallCode(codeAddr, code)
+	defer contract.Finalise()
+
+	ret, err = evm.Run(contract, input)
+	// if the contract creation ran successfully and no errors were returned
+	// calculate the gas required to store the code. If the code could not
+	// be stored due to not enough gas set an error and let it be handled
+	// by the error checking condition below.
+	if err == nil && createAccount {
+		dataGas := big.NewInt(int64(len(ret)))
+		dataGas.Mul(dataGas, params.CreateDataGas)
+		if contract.UseGas(dataGas) {
+			env.Db().SetCode(*address, ret)
+		} else {
+			err = vm.CodeStoreOutOfGasError
+		}
+	}
+
+	// When an error was returned by the EVM or when setting the creation code
+	// above we revert to the snapshot and consume any gas remaining. Additionally
+	// when we're in homestead this also counts for code storage gas errors.
+	if err != nil && (params.IsHomestead(env.BlockNumber()) || err != vm.CodeStoreOutOfGasError) {
+		contract.UseGas(contract.Gas)
+
+		env.SetSnapshot(snapshotPreTransfer)
+	}
+
+	return ret, addr, err
+}
+
+func execDelegateCall(env vm.Environment, caller vm.ContractRef, originAddr, toAddr, codeAddr *common.Address, input, code []byte, gas, gasPrice, value *big.Int) (ret []byte, addr common.Address, err error) {
+	evm := vm.NewVm(env)
+	// Depth check execution. Fail if we're trying to execute above the
+	// limit.
+	if env.Depth() > int(params.CallCreateDepth.Int64()) {
+		caller.ReturnGas(gas, gasPrice)
+		return nil, common.Address{}, vm.DepthError
+	}
+
+	snapshot := env.MakeSnapshot()
+
+	var to vm.Account
+	if !env.Db().Exist(*toAddr) {
+		to = env.Db().CreateAccount(*toAddr)
+	} else {
+		to = env.Db().GetAccount(*toAddr)
+	}
+
+	// Iinitialise a new contract and make initialise the delegate values
+	contract := vm.NewContract(caller, to, value, gas, gasPrice).AsDelegate()
+	contract.SetCallCode(codeAddr, code)
+	defer contract.Finalise()
 
 	ret, err = evm.Run(contract, input)
 	if err != nil {
-		env.SetSnapshot(snapshot) //env.Db().Set(snapshot)
+		contract.UseGas(contract.Gas)
+
+		env.SetSnapshot(snapshot)
 	}
 
 	return ret, addr, err
diff --git a/core/state/dump.go b/core/state/dump.go
index cff9c50aa..8eb03e8e4 100644
--- a/core/state/dump.go
+++ b/core/state/dump.go
@@ -28,6 +28,7 @@ type Account struct {
 	Nonce    uint64            `json:"nonce"`
 	Root     string            `json:"root"`
 	CodeHash string            `json:"codeHash"`
+	Code     string            `json:"code"`
 	Storage  map[string]string `json:"storage"`
 }
 
@@ -47,7 +48,7 @@ func (self *StateDB) RawDump() World {
 		addr := self.trie.GetKey(it.Key)
 		stateObject, _ := DecodeObject(common.BytesToAddress(addr), self.db, it.Value)
 
-		account := Account{Balance: stateObject.balance.String(), Nonce: stateObject.nonce, Root: common.Bytes2Hex(stateObject.Root()), CodeHash: common.Bytes2Hex(stateObject.codeHash)}
+		account := Account{Balance: stateObject.balance.String(), Nonce: stateObject.nonce, Root: common.Bytes2Hex(stateObject.Root()), CodeHash: common.Bytes2Hex(stateObject.codeHash), Code: common.Bytes2Hex(stateObject.Code())}
 		account.Storage = make(map[string]string)
 
 		storageIt := stateObject.trie.Iterator()
diff --git a/core/state/state_object.go b/core/state/state_object.go
index 47546112f..6095fc96a 100644
--- a/core/state/state_object.go
+++ b/core/state/state_object.go
@@ -238,6 +238,13 @@ func (self *StateObject) Nonce() uint64 {
 	return self.nonce
 }
 
+// Never called, but must be present to allow StateObject to be used
+// as a vm.Account interface that also satisfies the vm.ContractRef
+// interface. Interfaces are awesome.
+func (self *StateObject) Value() *big.Int {
+	panic("Value on StateObject should never be called")
+}
+
 func (self *StateObject) EachStorage(cb func(key, value []byte)) {
 	// When iterating over the storage check the cache first
 	for h, v := range self.storage {
diff --git a/core/state_processor.go b/core/state_processor.go
index d9c24935d..b9793b157 100644
--- a/core/state_processor.go
+++ b/core/state_processor.go
@@ -43,7 +43,6 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB) (ty
 
 	for i, tx := range block.Transactions() {
 		statedb.StartRecord(tx.Hash(), block.Hash(), i)
-
 		receipt, logs, _, err := ApplyTransaction(p.bc, gp, statedb, header, tx, totalUsedGas)
 		if err != nil {
 			return nil, nil, totalUsedGas, err
diff --git a/core/state_transition.go b/core/state_transition.go
index 7ecc01d4c..52a46c63d 100644
--- a/core/state_transition.go
+++ b/core/state_transition.go
@@ -27,6 +27,10 @@ import (
 	"github.com/ethereum/go-ethereum/params"
 )
 
+var (
+	Big0 = big.NewInt(0)
+)
+
 /*
 The State Transitioning Model
 
@@ -59,6 +63,7 @@ type StateTransition struct {
 // Message represents a message sent to a contract.
 type Message interface {
 	From() (common.Address, error)
+	FromFrontier() (common.Address, error)
 	To() *common.Address
 
 	GasPrice() *big.Int
@@ -75,8 +80,13 @@ func MessageCreatesContract(msg Message) bool {
 
 // IntrinsicGas computes the 'intrisic gas' for a message
 // with the given data.
-func IntrinsicGas(data []byte) *big.Int {
-	igas := new(big.Int).Set(params.TxGas)
+func IntrinsicGas(data []byte, contractCreation, homestead bool) *big.Int {
+	igas := new(big.Int)
+	if contractCreation && homestead {
+		igas.Set(params.TxGasContractCreation)
+	} else {
+		igas.Set(params.TxGas)
+	}
 	if len(data) > 0 {
 		var nz int64
 		for _, byt := range data {
@@ -110,7 +120,15 @@ func ApplyMessage(env vm.Environment, msg Message, gp *GasPool) ([]byte, *big.In
 }
 
 func (self *StateTransition) from() (vm.Account, error) {
-	f, err := self.msg.From()
+	var (
+		f   common.Address
+		err error
+	)
+	if params.IsHomestead(self.env.BlockNumber()) {
+		f, err = self.msg.From()
+	} else {
+		f, err = self.msg.FromFrontier()
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -195,35 +213,35 @@ func (self *StateTransition) transitionDb() (ret []byte, usedGas *big.Int, err e
 	if err = self.preCheck(); err != nil {
 		return
 	}
-
 	msg := self.msg
 	sender, _ := self.from() // err checked in preCheck
 
+	homestead := params.IsHomestead(self.env.BlockNumber())
+	contractCreation := MessageCreatesContract(msg)
 	// Pay intrinsic gas
-	if err = self.useGas(IntrinsicGas(self.data)); err != nil {
+	if err = self.useGas(IntrinsicGas(self.data, contractCreation, homestead)); err != nil {
 		return nil, nil, InvalidTxError(err)
 	}
 
 	vmenv := self.env
-	var addr common.Address
-	if MessageCreatesContract(msg) {
-		ret, addr, err = vmenv.Create(sender, self.data, self.gas, self.gasPrice, self.value)
-		if err == nil {
-			dataGas := big.NewInt(int64(len(ret)))
-			dataGas.Mul(dataGas, params.CreateDataGas)
-			if err := self.useGas(dataGas); err == nil {
-				self.state.SetCode(addr, ret)
-			} else {
-				ret = nil // does not affect consensus but useful for StateTests validations
-				glog.V(logger.Core).Infoln("Insufficient gas for creating code. Require", dataGas, "and have", self.gas)
-			}
+	//var addr common.Address
+	if contractCreation {
+		ret, _, err = vmenv.Create(sender, self.data, self.gas, self.gasPrice, self.value)
+		if homestead && err == vm.CodeStoreOutOfGasError {
+			self.gas = Big0
+		}
+
+		if err != nil {
+			ret = nil
+			glog.V(logger.Core).Infoln("VM create err:", err)
 		}
-		glog.V(logger.Core).Infoln("VM create err:", err)
 	} else {
 		// Increment the nonce for the next transaction
 		self.state.SetNonce(sender.Address(), self.state.GetNonce(sender.Address())+1)
 		ret, err = vmenv.Call(sender, self.to().Address(), self.data, self.gas, self.gasPrice, self.value)
-		glog.V(logger.Core).Infoln("VM call err:", err)
+		if err != nil {
+			glog.V(logger.Core).Infoln("VM call err:", err)
+		}
 	}
 
 	if err != nil && IsValueTransferErr(err) {
diff --git a/core/transaction_pool.go b/core/tx_pool.go
index 456de3cb6..b8fb4cd35 100644
--- a/core/transaction_pool.go
+++ b/core/tx_pool.go
@@ -30,6 +30,7 @@ import (
 	"github.com/ethereum/go-ethereum/event"
 	"github.com/ethereum/go-ethereum/logger"
 	"github.com/ethereum/go-ethereum/logger/glog"
+	"github.com/ethereum/go-ethereum/params"
 )
 
 var (
@@ -70,6 +71,8 @@ type TxPool struct {
 	mu           sync.RWMutex
 	pending      map[common.Hash]*types.Transaction // processable transactions
 	queue        map[common.Address]map[common.Hash]*types.Transaction
+
+	homestead bool
 }
 
 func NewTxPool(eventMux *event.TypeMux, currentStateFn stateFn, gasLimitFn func() *big.Int) *TxPool {
@@ -85,6 +88,7 @@ func NewTxPool(eventMux *event.TypeMux, currentStateFn stateFn, gasLimitFn func(
 		localTx:      newTxSet(),
 		events:       eventMux.Subscribe(ChainHeadEvent{}, GasPriceChanged{}, RemovedTransactionEvent{}),
 	}
+
 	go pool.eventLoop()
 
 	return pool
@@ -98,6 +102,10 @@ func (pool *TxPool) eventLoop() {
 		switch ev := ev.Data.(type) {
 		case ChainHeadEvent:
 			pool.mu.Lock()
+			if ev.Block != nil && params.IsHomestead(ev.Block.Number()) {
+				pool.homestead = true
+			}
+
 			pool.resetState()
 			pool.mu.Unlock()
 		case GasPriceChanged:
@@ -210,30 +218,24 @@ func (pool *TxPool) SetLocal(tx *types.Transaction) {
 // validateTx checks whether a transaction is valid according
 // to the consensus rules.
 func (pool *TxPool) validateTx(tx *types.Transaction) error {
-	// Validate sender
-	var (
-		from common.Address
-		err  error
-	)
-
 	local := pool.localTx.contains(tx.Hash())
 	// Drop transactions under our own minimal accepted gas price
 	if !local && pool.minGasPrice.Cmp(tx.GasPrice()) > 0 {
 		return ErrCheap
 	}
 
-	// Validate the transaction sender and it's sig. Throw
-	// if the from fields is invalid.
-	if from, err = tx.From(); err != nil {
+	currentState, err := pool.currentState()
+	if err != nil {
+		return err
+	}
+
+	from, err := tx.From()
+	if err != nil {
 		return ErrInvalidSender
 	}
 
 	// Make sure the account exist. Non existent accounts
 	// haven't got funds and well therefor never pass.
-	currentState, err := pool.currentState()
-	if err != nil {
-		return err
-	}
 	if !currentState.HasAccount(from) {
 		return ErrNonExistentAccount
 	}
@@ -262,8 +264,8 @@ func (pool *TxPool) validateTx(tx *types.Transaction) error {
 		return ErrInsufficientFunds
 	}
 
-	// Should supply enough intrinsic gas
-	if tx.Gas().Cmp(IntrinsicGas(tx.Data())) < 0 {
+	intrGas := IntrinsicGas(tx.Data(), MessageCreatesContract(tx), pool.homestead)
+	if tx.Gas().Cmp(intrGas) < 0 {
 		return ErrIntrinsicGas
 	}
 
diff --git a/core/transaction_pool_test.go b/core/tx_pool_test.go
index 811e40111..811e40111 100644
--- a/core/transaction_pool_test.go
+++ b/core/tx_pool_test.go
diff --git a/core/types/transaction.go b/core/types/transaction.go
index 4049ae888..0c9c1ce18 100644
--- a/core/types/transaction.go
+++ b/core/types/transaction.go
@@ -157,11 +157,47 @@ func (tx *Transaction) Size() common.StorageSize {
 	return common.StorageSize(c)
 }
 
+// From returns the address derived from the signature (V, R, S) using secp256k1
+// eliptic curve and an error if it failed deriving or upon an incorrect
+// signature.
+//
+// From Uses the homestead consensus rules to determine whether the signature is
+// valid.
+//
+// From caches the address, allowing it to be used regardless of
+// Frontier / Homestead. however, the first time called it runs
+// signature validations, so we need two versions. This makes it
+// easier to ensure backwards compatibility of things like package rpc
+// where eth_getblockbynumber uses tx.From() and needs to work for
+// both txs before and after the first homestead block. Signatures
+// valid in homestead are a subset of valid ones in Frontier)
 func (tx *Transaction) From() (common.Address, error) {
+	return doFrom(tx, true)
+}
+
+// FromFrontier returns the address derived from the signature (V, R, S) using
+// secp256k1 eliptic curve and an error if it failed deriving or upon an
+// incorrect signature.
+//
+// FromFrantier uses the frontier consensus rules to determine whether the
+// signature is valid.
+//
+// FromFrontier caches the address, allowing it to be used regardless of
+// Frontier / Homestead. however, the first time called it runs
+// signature validations, so we need two versions. This makes it
+// easier to ensure backwards compatibility of things like package rpc
+// where eth_getblockbynumber uses tx.From() and needs to work for
+// both txs before and after the first homestead block. Signatures
+// valid in homestead are a subset of valid ones in Frontier)
+func (tx *Transaction) FromFrontier() (common.Address, error) {
+	return doFrom(tx, false)
+}
+
+func doFrom(tx *Transaction, homestead bool) (common.Address, error) {
 	if from := tx.from.Load(); from != nil {
 		return from.(common.Address), nil
 	}
-	pubkey, err := tx.publicKey()
+	pubkey, err := tx.publicKey(homestead)
 	if err != nil {
 		return common.Address{}, err
 	}
@@ -182,8 +218,8 @@ func (tx *Transaction) SignatureValues() (v byte, r *big.Int, s *big.Int) {
 	return tx.data.V, new(big.Int).Set(tx.data.R), new(big.Int).Set(tx.data.S)
 }
 
-func (tx *Transaction) publicKey() ([]byte, error) {
-	if !crypto.ValidateSignatureValues(tx.data.V, tx.data.R, tx.data.S) {
+func (tx *Transaction) publicKey(homestead bool) ([]byte, error) {
+	if !crypto.ValidateSignatureValues(tx.data.V, tx.data.R, tx.data.S, homestead) {
 		return nil, ErrInvalidSig
 	}
 
diff --git a/core/vm/contract.go b/core/vm/contract.go
index 5981dcca0..d23995218 100644
--- a/core/vm/contract.go
+++ b/core/vm/contract.go
@@ -26,15 +26,20 @@ import (
 type ContractRef interface {
 	ReturnGas(*big.Int, *big.Int)
 	Address() common.Address
+	Value() *big.Int
 	SetCode([]byte)
 	EachStorage(cb func(key, value []byte))
 }
 
 // Contract represents an ethereum contract in the state database. It contains
-// the the contract code, calling arguments. Contract implements ContractReg
+// the the contract code, calling arguments. Contract implements ContractRef
 type Contract struct {
-	caller ContractRef
-	self   ContractRef
+	// CallerAddress is the result of the caller which initialised this
+	// contract. However when the "call method" is delegated this value
+	// needs to be initialised to that of the caller's caller.
+	CallerAddress common.Address
+	caller        ContractRef
+	self          ContractRef
 
 	jumpdests destinations // result of JUMPDEST analysis.
 
@@ -45,11 +50,13 @@ type Contract struct {
 	value, Gas, UsedGas, Price *big.Int
 
 	Args []byte
+
+	DelegateCall bool
 }
 
-// Create a new context for the given data items.
+// NewContract returns a new contract environment for the execution of EVM.
 func NewContract(caller ContractRef, object ContractRef, value, gas, price *big.Int) *Contract {
-	c := &Contract{caller: caller, self: object, Args: nil}
+	c := &Contract{CallerAddress: caller.Address(), caller: caller, self: object, Args: nil}
 
 	if parent, ok := caller.(*Contract); ok {
 		// Reuse JUMPDEST analysis from parent context if available.
@@ -70,6 +77,16 @@ func NewContract(caller ContractRef, object ContractRef, value, gas, price *big.
 	return c
 }
 
+// AsDelegate sets the contract to be a delegate call and returns the current
+// contract (for chaining calls)
+func (c *Contract) AsDelegate() *Contract {
+	c.DelegateCall = true
+	// NOTE: caller must, at all times be a contract. It should never happen
+	// that caller is something other than a Contract.
+	c.CallerAddress = c.caller.(*Contract).CallerAddress
+	return c
+}
+
 // GetOp returns the n'th element in the contract's byte array
 func (c *Contract) GetOp(n uint64) OpCode {
 	return OpCode(c.GetByte(n))
@@ -84,13 +101,19 @@ func (c *Contract) GetByte(n uint64) byte {
 	return 0
 }
 
-// Return returns the given ret argument and returns any remaining gas to the
-// caller
-func (c *Contract) Return(ret []byte) []byte {
+// Caller returns the caller of the contract.
+//
+// Caller will recursively call caller when the contract is a delegate
+// call, including that of caller's caller.
+func (c *Contract) Caller() common.Address {
+	return c.CallerAddress
+}
+
+// Finalise finalises the contract and returning any remaining gas to the original
+// caller.
+func (c *Contract) Finalise() {
 	// Return the remaining gas to the caller
 	c.caller.ReturnGas(c.Gas, c.Price)
-
-	return ret
 }
 
 // UseGas attempts the use gas and subtracts it and returns true on success
@@ -114,6 +137,11 @@ func (c *Contract) Address() common.Address {
 	return c.self.Address()
 }
 
+// Value returns the contracts value (sent to it from it's caller)
+func (c *Contract) Value() *big.Int {
+	return c.value
+}
+
 // SetCode sets the code to the contract
 func (self *Contract) SetCode(code []byte) {
 	self.Code = code
diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index 22cb9eab2..f204432a2 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -93,7 +93,8 @@ func ecrecoverFunc(in []byte) []byte {
 	vbig := common.Bytes2Big(in[32:64])
 	v := byte(vbig.Uint64())
 
-	if !crypto.ValidateSignatureValues(v, r, s) {
+	// tighter sig s values in homestead only apply to tx sigs
+	if !crypto.ValidateSignatureValues(v, r, s, false) {
 		glog.V(logger.Debug).Infof("EC RECOVER FAIL: v, r or s value invalid")
 		return nil
 	}
diff --git a/core/vm/environment.go b/core/vm/environment.go
index 4fee583bf..a58e3ba2b 100644
--- a/core/vm/environment.go
+++ b/core/vm/environment.go
@@ -70,6 +70,8 @@ type Environment interface {
 	Call(me ContractRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
 	// Take another's contract code and execute within our own context
 	CallCode(me ContractRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
+	// Same as CallCode except sender and value is propagated from parent to child scope
+	DelegateCall(me ContractRef, addr common.Address, data []byte, gas, price *big.Int) ([]byte, error)
 	// Create a new contract
 	Create(me ContractRef, data []byte, gas, price, value *big.Int) ([]byte, common.Address, error)
 }
@@ -122,4 +124,5 @@ type Account interface {
 	ReturnGas(*big.Int, *big.Int)
 	SetCode([]byte)
 	EachStorage(cb func(key, value []byte))
+	Value() *big.Int
 }
diff --git a/core/vm/errors.go b/core/vm/errors.go
index e2fc84065..116fbe456 100644
--- a/core/vm/errors.go
+++ b/core/vm/errors.go
@@ -24,4 +24,5 @@ import (
 )
 
 var OutOfGasError = errors.New("Out of gas")
+var CodeStoreOutOfGasError = errors.New("Contract creation code storage out of gas")
 var DepthError = fmt.Errorf("Max call depth exceeded (%d)", params.CallCreateDepth)
diff --git a/core/vm/gas.go b/core/vm/gas.go
index bff0ac91b..09feddd7d 100644
--- a/core/vm/gas.go
+++ b/core/vm/gas.go
@@ -136,6 +136,7 @@ var _baseCheck = map[OpCode]req{
 	CREATE:       {3, params.CreateGas, 1},
 	CALL:         {7, params.CallGas, 1},
 	CALLCODE:     {7, params.CallGas, 1},
+	DELEGATECALL: {6, params.CallGas, 1},
 	JUMPDEST:     {0, params.JumpdestGas, 0},
 	SUICIDE:      {1, Zero, 0},
 	RETURN:       {2, Zero, 0},
diff --git a/core/vm/instructions.go b/core/vm/instructions.go
index 2e868521e..26f7671ff 100644
--- a/core/vm/instructions.go
+++ b/core/vm/instructions.go
@@ -337,7 +337,7 @@ func opOrigin(instr instruction, pc *uint64, env Environment, contract *Contract
 }
 
 func opCaller(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *stack) {
-	stack.push(common.Bytes2Big(contract.caller.Address().Bytes()))
+	stack.push(contract.Caller().Big())
 }
 
 func opCallValue(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *stack) {
@@ -485,7 +485,6 @@ func opSload(instr instruction, pc *uint64, env Environment, contract *Contract,
 func opSstore(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *stack) {
 	loc := common.BigToHash(stack.pop())
 	val := stack.pop()
-
 	env.Db().SetState(contract.Address(), loc, common.BigToHash(val))
 }
 
@@ -514,25 +513,19 @@ func opCreate(instr instruction, pc *uint64, env Environment, contract *Contract
 		offset, size = stack.pop(), stack.pop()
 		input        = memory.Get(offset.Int64(), size.Int64())
 		gas          = new(big.Int).Set(contract.Gas)
-		addr         common.Address
-		ret          []byte
-		suberr       error
 	)
-
 	contract.UseGas(contract.Gas)
-	ret, addr, suberr = env.Create(contract, input, gas, contract.Price, value)
-	if suberr != nil {
+	_, addr, suberr := env.Create(contract, input, gas, contract.Price, value)
+	// Push item on the stack based on the returned error. If the ruleset is
+	// homestead we must check for CodeStoreOutOfGasError (homestead only
+	// rule) and treat as an error, if the ruleset is frontier we must
+	// ignore this error and pretend the operation was successful.
+	if params.IsHomestead(env.BlockNumber()) && suberr == CodeStoreOutOfGasError {
+		stack.push(new(big.Int))
+	} else if suberr != nil && suberr != CodeStoreOutOfGasError {
 		stack.push(new(big.Int))
 	} else {
-		// gas < len(ret) * Createinstr.dataGas == NO_CODE
-		dataGas := big.NewInt(int64(len(ret)))
-		dataGas.Mul(dataGas, params.CreateDataGas)
-		if contract.UseGas(dataGas) {
-			env.Db().SetCode(addr, ret)
-		}
-
 		stack.push(addr.Big())
-
 	}
 }
 
@@ -598,6 +591,21 @@ func opCallCode(instr instruction, pc *uint64, env Environment, contract *Contra
 	}
 }
 
+func opDelegateCall(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *stack) {
+	gas, to, inOffset, inSize, outOffset, outSize := stack.pop(), stack.pop(), stack.pop(), stack.pop(), stack.pop(), stack.pop()
+
+	toAddr := common.BigToAddress(to)
+	args := memory.Get(inOffset.Int64(), inSize.Int64())
+	ret, err := env.DelegateCall(contract, toAddr, args, gas, contract.Price)
+
+	if err != nil {
+		stack.push(new(big.Int))
+	} else {
+		stack.push(big.NewInt(1))
+		memory.Set(outOffset.Uint64(), outSize.Uint64(), ret)
+	}
+}
+
 func opReturn(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *stack) {
 }
 func opStop(instr instruction, pc *uint64, env Environment, contract *Contract, memory *Memory, stack *stack) {
diff --git a/core/vm/jit.go b/core/vm/jit.go
index 1aa7d7ef2..504aab523 100644
--- a/core/vm/jit.go
+++ b/core/vm/jit.go
@@ -275,6 +275,11 @@ func CompileProgram(program *Program) (err error) {
 			program.addInstr(op, pc, opGas, nil)
 		case CREATE:
 			program.addInstr(op, pc, opCreate, nil)
+		case DELEGATECALL:
+			// Instruction added regardless of homestead phase.
+			// Homestead (and execution of the opcode) is checked during
+			// runtime.
+			program.addInstr(op, pc, opDelegateCall, nil)
 		case CALL:
 			program.addInstr(op, pc, opCall, nil)
 		case CALLCODE:
@@ -317,10 +322,14 @@ func runProgram(program *Program, pcstart uint64, mem *Memory, stack *stack, env
 		}()
 	}
 
+	homestead := params.IsHomestead(env.BlockNumber())
 	for pc < uint64(len(program.instructions)) {
 		instrCount++
 
 		instr := program.instructions[pc]
+		if instr.Op() == DELEGATECALL && !homestead {
+			return nil, fmt.Errorf("Invalid opcode 0x%x", instr.Op())
+		}
 
 		ret, err := instr.do(program, &pc, env, contract, mem, stack)
 		if err != nil {
@@ -328,13 +337,13 @@ func runProgram(program *Program, pcstart uint64, mem *Memory, stack *stack, env
 		}
 
 		if instr.halts() {
-			return contract.Return(ret), nil
+			return ret, nil
 		}
 	}
 
 	contract.Input = nil
 
-	return contract.Return(nil), nil
+	return nil, nil
 }
 
 // validDest checks if the given distination is a valid one given the
@@ -457,7 +466,6 @@ func jitCalculateGasAndSize(env Environment, contract *Contract, instr instructi
 		gas.Add(gas, stack.data[stack.len()-1])
 
 		if op == CALL {
-			//if env.Db().GetStateObject(common.BigToAddress(stack.data[stack.len()-2])) == nil {
 			if !env.Db().Exist(common.BigToAddress(stack.data[stack.len()-2])) {
 				gas.Add(gas, params.CallNewAccountGas)
 			}
@@ -471,6 +479,13 @@ func jitCalculateGasAndSize(env Environment, contract *Contract, instr instructi
 		y := calcMemSize(stack.data[stack.len()-4], stack.data[stack.len()-5])
 
 		newMemSize = common.BigMax(x, y)
+	case DELEGATECALL:
+		gas.Add(gas, stack.data[stack.len()-1])
+
+		x := calcMemSize(stack.data[stack.len()-5], stack.data[stack.len()-6])
+		y := calcMemSize(stack.data[stack.len()-3], stack.data[stack.len()-4])
+
+		newMemSize = common.BigMax(x, y)
 	}
 	quadMemGas(mem, newMemSize, gas)
 
diff --git a/core/vm/jit_test.go b/core/vm/jit_test.go
index 8c50ed0f5..e8e078a46 100644
--- a/core/vm/jit_test.go
+++ b/core/vm/jit_test.go
@@ -127,6 +127,8 @@ type account struct{}
 
 func (account) SubBalance(amount *big.Int)             {}
 func (account) AddBalance(amount *big.Int)             {}
+func (account) SetAddress(common.Address)              {}
+func (account) Value() *big.Int                        { return nil }
 func (account) SetBalance(*big.Int)                    {}
 func (account) SetNonce(uint64)                        {}
 func (account) Balance() *big.Int                      { return nil }
@@ -206,3 +208,6 @@ func (self *Env) CallCode(caller ContractRef, addr common.Address, data []byte,
 func (self *Env) Create(caller ContractRef, data []byte, gas, price, value *big.Int) ([]byte, common.Address, error) {
 	return nil, common.Address{}, nil
 }
+func (self *Env) DelegateCall(me ContractRef, addr common.Address, data []byte, gas, price *big.Int) ([]byte, error) {
+	return nil, nil
+}
diff --git a/core/vm/jump_table.go b/core/vm/jump_table.go
index ab899647f..37d7bb160 100644
--- a/core/vm/jump_table.go
+++ b/core/vm/jump_table.go
@@ -1,13 +1,29 @@
 package vm
 
-import "math/big"
+import (
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/params"
+)
 
 type jumpPtr struct {
 	fn    instrFn
 	valid bool
 }
 
-var jumpTable [256]jumpPtr
+type vmJumpTable [256]jumpPtr
+
+func (jt vmJumpTable) init(blockNumber *big.Int) {
+	// when initialising a new VM execution we must first check the homestead
+	// changes.
+	if params.IsHomestead(blockNumber) {
+		jumpTable[DELEGATECALL] = jumpPtr{opDelegateCall, true}
+	} else {
+		jumpTable[DELEGATECALL] = jumpPtr{nil, false}
+	}
+}
+
+var jumpTable vmJumpTable
 
 func init() {
 	jumpTable[ADD] = jumpPtr{opAdd, true}
diff --git a/core/vm/jump_table_test.go b/core/vm/jump_table_test.go
new file mode 100644
index 000000000..98d34bef2
--- /dev/null
+++ b/core/vm/jump_table_test.go
@@ -0,0 +1,24 @@
+package vm
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/params"
+)
+
+func TestInit(t *testing.T) {
+	params.HomesteadBlock = big.NewInt(1)
+
+	jumpTable.init(big.NewInt(0))
+	if jumpTable[DELEGATECALL].valid {
+		t.Error("Expected DELEGATECALL not to be present")
+	}
+
+	for _, n := range []int64{1, 2, 100} {
+		jumpTable.init(big.NewInt(n))
+		if !jumpTable[DELEGATECALL].valid {
+			t.Error("Expected DELEGATECALL to be present for block", n)
+		}
+	}
+}
diff --git a/core/vm/opcodes.go b/core/vm/opcodes.go
index dc4139092..7d861f1de 100644
--- a/core/vm/opcodes.go
+++ b/core/vm/opcodes.go
@@ -200,6 +200,7 @@ const (
 	CALL
 	CALLCODE
 	RETURN
+	DELEGATECALL
 
 	SUICIDE = 0xff
 )
@@ -349,11 +350,12 @@ var opCodeToString = map[OpCode]string{
 	LOG4:   "LOG4",
 
 	// 0xf0 range
-	CREATE:   "CREATE",
-	CALL:     "CALL",
-	RETURN:   "RETURN",
-	CALLCODE: "CALLCODE",
-	SUICIDE:  "SUICIDE",
+	CREATE:       "CREATE",
+	CALL:         "CALL",
+	RETURN:       "RETURN",
+	CALLCODE:     "CALLCODE",
+	DELEGATECALL: "DELEGATECALL",
+	SUICIDE:      "SUICIDE",
 
 	PUSH: "PUSH",
 	DUP:  "DUP",
@@ -402,6 +404,7 @@ var stringToOp = map[string]OpCode{
 	"CALLDATALOAD": CALLDATALOAD,
 	"CALLDATASIZE": CALLDATASIZE,
 	"CALLDATACOPY": CALLDATACOPY,
+	"DELEGATECALL": DELEGATECALL,
 	"CODESIZE":     CODESIZE,
 	"CODECOPY":     CODECOPY,
 	"GASPRICE":     GASPRICE,
diff --git a/core/vm/runtime/env.go b/core/vm/runtime/env.go
index 22f9ea14d..77519df81 100644
--- a/core/vm/runtime/env.go
+++ b/core/vm/runtime/env.go
@@ -101,6 +101,10 @@ func (self *Env) CallCode(caller vm.ContractRef, addr common.Address, data []byt
 	return core.CallCode(self, caller, addr, data, gas, price, value)
 }
 
+func (self *Env) DelegateCall(me vm.ContractRef, addr common.Address, data []byte, gas, price *big.Int) ([]byte, error) {
+	return core.DelegateCall(self, me, addr, data, gas, price)
+}
+
 func (self *Env) Create(caller vm.ContractRef, data []byte, gas, price, value *big.Int) ([]byte, common.Address, error) {
 	return core.Create(self, caller, data, gas, price, value)
 }
diff --git a/core/vm/vm.go b/core/vm/vm.go
index 0c6bbcd42..320135ff2 100644
--- a/core/vm/vm.go
+++ b/core/vm/vm.go
@@ -35,6 +35,9 @@ type Vm struct {
 
 // New returns a new Vm
 func New(env Environment) *Vm {
+	// init the jump table. Also prepares the homestead changes
+	jumpTable.init(env.BlockNumber())
+
 	return &Vm{env: env}
 }
 
@@ -43,16 +46,6 @@ func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
 	self.env.SetDepth(self.env.Depth() + 1)
 	defer self.env.SetDepth(self.env.Depth() - 1)
 
-	// User defer pattern to check for an error and, based on the error being nil or not, use all gas and return.
-	defer func() {
-		if err != nil {
-			// In case of a VM exception (known exceptions) all gas consumed (panics NOT included).
-			contract.UseGas(contract.Gas)
-
-			ret = contract.Return(nil)
-		}
-	}()
-
 	if contract.CodeAddr != nil {
 		if p := Precompiled[contract.CodeAddr.Str()]; p != nil {
 			return self.RunPrecompiled(p, input, contract)
@@ -61,7 +54,7 @@ func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
 
 	// Don't bother with the execution if there's no code.
 	if len(contract.Code) == 0 {
-		return contract.Return(nil), nil
+		return nil, nil
 	}
 
 	var (
@@ -160,7 +153,6 @@ func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
 
 		// Get the memory location of pc
 		op = contract.GetOp(pc)
-
 		// calculate the new memory size and gas price for the current executing opcode
 		newMemSize, cost, err = calculateGasAndSize(self.env, contract, caller, op, statedb, mem, stack)
 		if err != nil {
@@ -177,7 +169,6 @@ func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
 		mem.Resize(newMemSize.Uint64())
 		// Add a log message
 		self.log(pc, op, contract.Gas, cost, mem, stack, contract, nil)
-
 		if opPtr := jumpTable[op]; opPtr.valid {
 			if opPtr.fn != nil {
 				opPtr.fn(instruction{}, &pc, self.env, contract, mem, stack)
@@ -205,13 +196,13 @@ func (self *Vm) Run(contract *Contract, input []byte) (ret []byte, err error) {
 					offset, size := stack.pop(), stack.pop()
 					ret := mem.GetPtr(offset.Int64(), size.Int64())
 
-					return contract.Return(ret), nil
+					return ret, nil
 				case SUICIDE:
 					opSuicide(instruction{}, nil, self.env, contract, mem, stack)
 
 					fallthrough
 				case STOP: // Stop the contract
-					return contract.Return(nil), nil
+					return nil, nil
 				}
 			}
 		} else {
@@ -332,7 +323,6 @@ func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef
 		gas.Add(gas, stack.data[stack.len()-1])
 
 		if op == CALL {
-			//if env.Db().GetStateObject(common.BigToAddress(stack.data[stack.len()-2])) == nil {
 			if !env.Db().Exist(common.BigToAddress(stack.data[stack.len()-2])) {
 				gas.Add(gas, params.CallNewAccountGas)
 			}
@@ -346,6 +336,13 @@ func calculateGasAndSize(env Environment, contract *Contract, caller ContractRef
 		y := calcMemSize(stack.data[stack.len()-4], stack.data[stack.len()-5])
 
 		newMemSize = common.BigMax(x, y)
+	case DELEGATECALL:
+		gas.Add(gas, stack.data[stack.len()-1])
+
+		x := calcMemSize(stack.data[stack.len()-5], stack.data[stack.len()-6])
+		y := calcMemSize(stack.data[stack.len()-3], stack.data[stack.len()-4])
+
+		newMemSize = common.BigMax(x, y)
 	}
 	quadMemGas(mem, newMemSize, gas)
 
@@ -358,7 +355,7 @@ func (self *Vm) RunPrecompiled(p *PrecompiledAccount, input []byte, contract *Co
 	if contract.UseGas(gas) {
 		ret = p.Call(input)
 
-		return contract.Return(ret), nil
+		return ret, nil
 	} else {
 		return nil, OutOfGasError
 	}
diff --git a/core/vm_env.go b/core/vm_env.go
index 1c787e982..db29cc32c 100644
--- a/core/vm_env.go
+++ b/core/vm_env.go
@@ -106,6 +106,10 @@ func (self *VMEnv) CallCode(me vm.ContractRef, addr common.Address, data []byte,
 	return CallCode(self, me, addr, data, gas, price, value)
 }
 
+func (self *VMEnv) DelegateCall(me vm.ContractRef, addr common.Address, data []byte, gas, price *big.Int) ([]byte, error) {
+	return DelegateCall(self, me, addr, data, gas, price)
+}
+
 func (self *VMEnv) Create(me vm.ContractRef, data []byte, gas, price, value *big.Int) ([]byte, common.Address, error) {
 	return Create(self, me, data, gas, price, value)
 }