core: add basic chain history support in GenerateChain

This change improves GenerateChain to support internal chain history access (ChainReader)
for the consensus engine and EVM.

GenerateChain takes a `parent` block and the number of blocks to create. With my changes,
the consensus engine and EVM can now access blocks from `parent` up to the block currently
being generated. This is required to make the BLOCKHASH instruction work, and also needed
to create real clique chains. Clique uses the chain history to create its 'snapshot'.

I've also added some more accessors to BlockGen. These are helpful when creating
transactions:

- g.Signer returns a signer instance for the current block
- g.Difficulty returns the current block difficulty
- g.Gas returns the remaining gas amount

core/bench_test.go

@@ -84,7 +84,7 @@ func genValueTx(nbytes int) func(int, *BlockGen) {
 		toaddr := common.Address{}
 		data := make([]byte, nbytes)
 		gas, _ := IntrinsicGas(data, nil, false, false, false, false)
-		signer := types.MakeSigner(gen.config, big.NewInt(int64(i)), gen.header.Time)
+		signer := gen.Signer()
 		gasPrice := big.NewInt(0)
 		if gen.header.BaseFee != nil {
 			gasPrice = gen.header.BaseFee
@@ -128,7 +128,7 @@ func genTxRing(naccounts int) func(int, *BlockGen) {
 		if gen.header.BaseFee != nil {
 			gasPrice = gen.header.BaseFee
 		}
-		signer := types.MakeSigner(gen.config, big.NewInt(int64(i)), gen.header.Time)
+		signer := gen.Signer()
 		for {
 			gas -= params.TxGas
 			if gas < params.TxGas {

core/chain_makers.go

@@ -38,8 +38,8 @@ import (
 // See GenerateChain for a detailed explanation.
 type BlockGen struct {
 	i       int
+	cm      *chainMaker
 	parent  *types.Block
-	chain   []*types.Block
 	header  *types.Header
 	statedb *state.StateDB
 
@@ -49,7 +49,6 @@ type BlockGen struct {
 	uncles      []*types.Header
 	withdrawals []*types.Withdrawal
 
-	config *params.ChainConfig
 	engine consensus.Engine
 }
 
@@ -88,13 +87,18 @@ func (b *BlockGen) SetPoS() {
 	b.header.Difficulty = new(big.Int)
 }
 
+// Difficulty returns the currently calculated difficulty of the block.
+func (b *BlockGen) Difficulty() *big.Int {
+	return new(big.Int).Set(b.header.Difficulty)
+}
+
 // SetParentBeaconRoot sets the parent beacon root field of the generated
 // block.
 func (b *BlockGen) SetParentBeaconRoot(root common.Hash) {
 	b.header.ParentBeaconRoot = &root
 	var (
 		blockContext = NewEVMBlockContext(b.header, nil, &b.header.Coinbase)
-		vmenv        = vm.NewEVM(blockContext, vm.TxContext{}, b.statedb, b.config, vm.Config{})
+		vmenv        = vm.NewEVM(blockContext, vm.TxContext{}, b.statedb, b.cm.config, vm.Config{})
 	)
 	ProcessBeaconBlockRoot(root, vmenv, b.statedb)
 }
@@ -111,7 +115,7 @@ func (b *BlockGen) addTx(bc *BlockChain, vmConfig vm.Config, tx *types.Transacti
 		b.SetCoinbase(common.Address{})
 	}
 	b.statedb.SetTxContext(tx.Hash(), len(b.txs))
-	receipt, err := ApplyTransaction(b.config, bc, &b.header.Coinbase, b.gasPool, b.statedb, b.header, tx, &b.header.GasUsed, vmConfig)
+	receipt, err := ApplyTransaction(b.cm.config, bc, &b.header.Coinbase, b.gasPool, b.statedb, b.header, tx, &b.header.GasUsed, vmConfig)
 	if err != nil {
 		panic(err)
 	}
@@ -125,11 +129,11 @@ func (b *BlockGen) addTx(bc *BlockChain, vmConfig vm.Config, tx *types.Transacti
 // AddTx adds a transaction to the generated block. If no coinbase has
 // been set, the block's coinbase is set to the zero address.
 //
-// AddTx panics if the transaction cannot be executed. In addition to
-// the protocol-imposed limitations (gas limit, etc.), there are some
-// further limitations on the content of transactions that can be
-// added. Notably, contract code relying on the BLOCKHASH instruction
-// will panic during execution.
+// AddTx panics if the transaction cannot be executed. In addition to the protocol-imposed
+// limitations (gas limit, etc.), there are some further limitations on the content of
+// transactions that can be added. Notably, contract code relying on the BLOCKHASH
+// instruction will panic during execution if it attempts to access a block number outside
+// of the range created by GenerateChain.
 func (b *BlockGen) AddTx(tx *types.Transaction) {
 	b.addTx(nil, vm.Config{}, tx)
 }
@@ -137,11 +141,10 @@ func (b *BlockGen) AddTx(tx *types.Transaction) {
 // AddTxWithChain adds a transaction to the generated block. If no coinbase has
 // been set, the block's coinbase is set to the zero address.
 //
-// AddTxWithChain panics if the transaction cannot be executed. In addition to
-// the protocol-imposed limitations (gas limit, etc.), there are some
-// further limitations on the content of transactions that can be
-// added. If contract code relies on the BLOCKHASH instruction,
-// the block in chain will be returned.
+// AddTxWithChain panics if the transaction cannot be executed. In addition to the
+// protocol-imposed limitations (gas limit, etc.), there are some further limitations on
+// the content of transactions that can be added. If contract code relies on the BLOCKHASH
+// instruction, the block in chain will be returned.
 func (b *BlockGen) AddTxWithChain(bc *BlockChain, tx *types.Transaction) {
 	b.addTx(bc, vm.Config{}, tx)
 }
@@ -158,8 +161,7 @@ func (b *BlockGen) GetBalance(addr common.Address) *big.Int {
 	return b.statedb.GetBalance(addr)
 }
 
-// AddUncheckedTx forcefully adds a transaction to the block without any
-// validation.
+// AddUncheckedTx forcefully adds a transaction to the block without any validation.
 //
 // AddUncheckedTx will cause consensus failures when used during real
 // chain processing. This is best used in conjunction with raw block insertion.
@@ -182,6 +184,16 @@ func (b *BlockGen) BaseFee() *big.Int {
 	return new(big.Int).Set(b.header.BaseFee)
 }
 
+// Gas returns the amount of gas left in the current block.
+func (b *BlockGen) Gas() uint64 {
+	return b.header.GasLimit - b.header.GasUsed
+}
+
+// Signer returns a valid signer instance for the current block.
+func (b *BlockGen) Signer() types.Signer {
+	return types.MakeSigner(b.cm.config, b.header.Number, b.header.Time)
+}
+
 // AddUncheckedReceipt forcefully adds a receipts to the block without a
 // backing transaction.
 //
@@ -207,20 +219,19 @@ func (b *BlockGen) AddUncle(h *types.Header) {
 
 	var parent *types.Header
 	for i := b.i - 1; i >= 0; i-- {
-		if b.chain[i].Hash() == h.ParentHash {
-			parent = b.chain[i].Header()
+		if b.cm.chain[i].Hash() == h.ParentHash {
+			parent = b.cm.chain[i].Header()
 			break
 		}
 	}
-	chainreader := &fakeChainReader{config: b.config}
-	h.Difficulty = b.engine.CalcDifficulty(chainreader, b.header.Time, parent)
+	h.Difficulty = b.engine.CalcDifficulty(b.cm, b.header.Time, parent)
 
 	// The gas limit and price should be derived from the parent
 	h.GasLimit = parent.GasLimit
-	if b.config.IsLondon(h.Number) {
-		h.BaseFee = eip1559.CalcBaseFee(b.config, parent)
-		if !b.config.IsLondon(parent.Number) {
-			parentGasLimit := parent.GasLimit * b.config.ElasticityMultiplier()
+	if b.cm.config.IsLondon(h.Number) {
+		h.BaseFee = eip1559.CalcBaseFee(b.cm.config, parent)
+		if !b.cm.config.IsLondon(parent.Number) {
+			parentGasLimit := parent.GasLimit * b.cm.config.ElasticityMultiplier()
 			h.GasLimit = CalcGasLimit(parentGasLimit, parentGasLimit)
 		}
 	}
@@ -242,12 +253,12 @@ func (b *BlockGen) nextWithdrawalIndex() uint64 {
 		return b.withdrawals[len(b.withdrawals)-1].Index + 1
 	}
 	for i := b.i - 1; i >= 0; i-- {
-		if wd := b.chain[i].Withdrawals(); len(wd) != 0 {
+		if wd := b.cm.chain[i].Withdrawals(); len(wd) != 0 {
 			return wd[len(wd)-1].Index + 1
 		}
 		if i == 0 {
 			// Correctly set the index if no parent had withdrawals.
-			if wd := b.parent.Withdrawals(); len(wd) != 0 {
+			if wd := b.cm.bottom.Withdrawals(); len(wd) != 0 {
 				return wd[len(wd)-1].Index + 1
 			}
 		}
@@ -263,9 +274,9 @@ func (b *BlockGen) PrevBlock(index int) *types.Block {
 		panic(fmt.Errorf("block index %d out of range (%d,%d)", index, -1, b.i))
 	}
 	if index == -1 {
-		return b.parent
+		return b.cm.bottom
 	}
-	return b.chain[index]
+	return b.cm.chain[index]
 }
 
 // OffsetTime modifies the time instance of a block, implicitly changing its
@@ -273,11 +284,10 @@ func (b *BlockGen) PrevBlock(index int) *types.Block {
 // tied to chain length directly.
 func (b *BlockGen) OffsetTime(seconds int64) {
 	b.header.Time += uint64(seconds)
-	if b.header.Time <= b.parent.Header().Time {
+	if b.header.Time <= b.cm.bottom.Header().Time {
 		panic("block time out of range")
 	}
-	chainreader := &fakeChainReader{config: b.config}
-	b.header.Difficulty = b.engine.CalcDifficulty(chainreader, b.header.Time, b.parent.Header())
+	b.header.Difficulty = b.engine.CalcDifficulty(b.cm, b.header.Time, b.parent.Header())
 }
 
 // GenerateChain creates a chain of n blocks. The first block's
@@ -296,11 +306,11 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 	if config == nil {
 		config = params.TestChainConfig
 	}
-	blocks, receipts := make(types.Blocks, n), make([]types.Receipts, n)
-	chainreader := &fakeChainReader{config: config}
+	cm := newChainMaker(parent, config)
+
 	genblock := func(i int, parent *types.Block, triedb *trie.Database, statedb *state.StateDB) (*types.Block, types.Receipts) {
-		b := &BlockGen{i: i, chain: blocks, parent: parent, statedb: statedb, config: config, engine: engine}
-		b.header = makeHeader(chainreader, parent, statedb, b.engine)
+		b := &BlockGen{i: i, cm: cm, parent: parent, statedb: statedb, engine: engine}
+		b.header = cm.makeHeader(parent, statedb, b.engine)
 
 		// Set the difficulty for clique block. The chain maker doesn't have access
 		// to a chain, so the difficulty will be left unset (nil). Set it here to the
@@ -331,7 +341,7 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 			gen(i, b)
 		}
 		if b.engine != nil {
-			block, err := b.engine.FinalizeAndAssemble(chainreader, b.header, statedb, b.txs, b.uncles, b.receipts, b.withdrawals)
+			block, err := b.engine.FinalizeAndAssemble(cm, b.header, statedb, b.txs, b.uncles, b.receipts, b.withdrawals)
 			if err != nil {
 				panic(err)
 			}
@@ -348,6 +358,7 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 		}
 		return nil, nil
 	}
+
 	// Forcibly use hash-based state scheme for retaining all nodes in disk.
 	triedb := trie.NewDatabase(db, trie.HashDefaults)
 	defer triedb.Close()
@@ -358,11 +369,10 @@ func GenerateChain(config *params.ChainConfig, parent *types.Block, engine conse
 			panic(err)
 		}
 		block, receipt := genblock(i, parent, triedb, statedb)
-		blocks[i] = block
-		receipts[i] = receipt
+		cm.add(block, receipt)
 		parent = block
 	}
-	return blocks, receipts
+	return cm.chain, cm.receipts
 }
 
 // GenerateChainWithGenesis is a wrapper of GenerateChain which will initialize
@@ -380,35 +390,32 @@ func GenerateChainWithGenesis(genesis *Genesis, engine consensus.Engine, n int,
 	return db, blocks, receipts
 }
 
-func makeHeader(chain consensus.ChainReader, parent *types.Block, state *state.StateDB, engine consensus.Engine) *types.Header {
+func (cm *chainMaker) makeHeader(parent *types.Block, state *state.StateDB, engine consensus.Engine) *types.Header {
 	var time uint64
 	if parent.Time() == 0 {
 		time = 10
 	} else {
 		time = parent.Time() + 10 // block time is fixed at 10 seconds
 	}
+
 	header := &types.Header{
-		Root:       state.IntermediateRoot(chain.Config().IsEIP158(parent.Number())),
+		Root:       state.IntermediateRoot(cm.config.IsEIP158(parent.Number())),
 		ParentHash: parent.Hash(),
 		Coinbase:   parent.Coinbase(),
-		Difficulty: engine.CalcDifficulty(chain, time, &types.Header{
-			Number:     parent.Number(),
-			Time:       time - 10,
-			Difficulty: parent.Difficulty(),
-			UncleHash:  parent.UncleHash(),
-		}),
+		Difficulty: engine.CalcDifficulty(cm, time, parent.Header()),
 		GasLimit:   parent.GasLimit(),
 		Number:     new(big.Int).Add(parent.Number(), common.Big1),
 		Time:       time,
 	}
-	if chain.Config().IsLondon(header.Number) {
-		header.BaseFee = eip1559.CalcBaseFee(chain.Config(), parent.Header())
-		if !chain.Config().IsLondon(parent.Number()) {
-			parentGasLimit := parent.GasLimit() * chain.Config().ElasticityMultiplier()
+
+	if cm.config.IsLondon(header.Number) {
+		header.BaseFee = eip1559.CalcBaseFee(cm.config, parent.Header())
+		if !cm.config.IsLondon(parent.Number()) {
+			parentGasLimit := parent.GasLimit() * cm.config.ElasticityMultiplier()
 			header.GasLimit = CalcGasLimit(parentGasLimit, parentGasLimit)
 		}
 	}
-	if chain.Config().IsCancun(header.Number, header.Time) {
+	if cm.config.IsCancun(header.Number, header.Time) {
 		var (
 			parentExcessBlobGas uint64
 			parentBlobGasUsed   uint64
@@ -461,18 +468,79 @@ func makeBlockChainWithGenesis(genesis *Genesis, n int, engine consensus.Engine,
 	return db, blocks
 }
 
-type fakeChainReader struct {
+// chainMaker contains the state of chain generation.
+type chainMaker struct {
+	bottom      *types.Block
 	config      *params.ChainConfig
+	chain       []*types.Block
+	chainByHash map[common.Hash]*types.Block
+	receipts    []types.Receipts
 }
 
+func newChainMaker(bottom *types.Block, config *params.ChainConfig) *chainMaker {
+	return &chainMaker{
+		bottom:      bottom,
+		config:      config,
+		chainByHash: make(map[common.Hash]*types.Block),
+	}
+}
+
+func (cm *chainMaker) add(b *types.Block, r []*types.Receipt) {
+	cm.chain = append(cm.chain, b)
+	cm.chainByHash[b.Hash()] = b
+	cm.receipts = append(cm.receipts, r)
+}
+
+func (cm *chainMaker) blockByNumber(number uint64) *types.Block {
+	if number == cm.bottom.NumberU64() {
+		return cm.bottom
+	}
+	cur := cm.CurrentHeader().Number.Uint64()
+	lowest := cm.bottom.NumberU64() + 1
+	if number < lowest || number > cur {
+		return nil
+	}
+	return cm.chain[number-lowest]
+}
+
+// ChainReader implementation
+
 // Config returns the chain configuration.
-func (cr *fakeChainReader) Config() *params.ChainConfig {
-	return cr.config
+func (cm *chainMaker) Config() *params.ChainConfig {
+	return cm.config
 }
 
-func (cr *fakeChainReader) CurrentHeader() *types.Header                            { return nil }
-func (cr *fakeChainReader) GetHeaderByNumber(number uint64) *types.Header           { return nil }
-func (cr *fakeChainReader) GetHeaderByHash(hash common.Hash) *types.Header          { return nil }
-func (cr *fakeChainReader) GetHeader(hash common.Hash, number uint64) *types.Header { return nil }
-func (cr *fakeChainReader) GetBlock(hash common.Hash, number uint64) *types.Block   { return nil }
-func (cr *fakeChainReader) GetTd(hash common.Hash, number uint64) *big.Int          { return nil }
+func (cm *chainMaker) CurrentHeader() *types.Header {
+	if len(cm.chain) == 0 {
+		return cm.bottom.Header()
+	}
+	return cm.chain[len(cm.chain)-1].Header()
+}
+
+func (cm *chainMaker) GetHeaderByNumber(number uint64) *types.Header {
+	b := cm.blockByNumber(number)
+	if b == nil {
+		return nil
+	}
+	return b.Header()
+}
+
+func (cm *chainMaker) GetHeaderByHash(hash common.Hash) *types.Header {
+	b := cm.chainByHash[hash]
+	if b == nil {
+		return nil
+	}
+	return b.Header()
+}
+
+func (cm *chainMaker) GetHeader(hash common.Hash, number uint64) *types.Header {
+	return cm.GetHeaderByNumber(number)
+}
+
+func (cm *chainMaker) GetBlock(hash common.Hash, number uint64) *types.Block {
+	return cm.blockByNumber(number)
+}
+
+func (cm *chainMaker) GetTd(hash common.Hash, number uint64) *big.Int {
+	return nil // not supported
+}

core/state_processor_test.go

@@ -359,7 +359,8 @@ func TestStateProcessorErrors(t *testing.T) {
 func GenerateBadBlock(parent *types.Block, engine consensus.Engine, txs types.Transactions, config *params.ChainConfig) *types.Block {
 	difficulty := big.NewInt(0)
 	if !config.TerminalTotalDifficultyPassed {
-		difficulty = engine.CalcDifficulty(&fakeChainReader{config}, parent.Time()+10, &types.Header{
+		fakeChainReader := newChainMaker(nil, config)
+		difficulty = engine.CalcDifficulty(fakeChainReader, parent.Time()+10, &types.Header{
 			Number:     parent.Number(),
 			Time:       parent.Time(),
 			Difficulty: parent.Difficulty(),