implement hash reads from smart contract

core/evm.go

@@ -17,6 +17,7 @@
 package core
 
 import (
+	"encoding/binary"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -24,6 +25,7 @@ import (
 	"github.com/ethereum/go-ethereum/consensus/misc/eip4844"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
+	"github.com/ethereum/go-ethereum/params"
 )
 
 // ChainContext supports retrieving headers and consensus parameters from the
@@ -89,40 +91,51 @@ func NewEVMTxContext(msg *Message) vm.TxContext {
 }
 
 // GetHashFn returns a GetHashFunc which retrieves header hashes by number
-func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
+func GetHashFn(ref *types.Header, chain ChainContext) vm.GetHashFunc {
 	// Cache will initially contain [refHash.parent],
 	// Then fill up with [refHash.p, refHash.pp, refHash.ppp, ...]
 	var cache []common.Hash
 
-	return func(n uint64) common.Hash {
+	return func(n uint64, statedb vm.StateDB, eip2935 bool) common.Hash {
 		if ref.Number.Uint64() <= n {
 			// This situation can happen if we're doing tracing and using
 			// block overrides.
 			return common.Hash{}
 		}
-		// If there's no hash cache yet, make one
-		if len(cache) == 0 {
-			cache = append(cache, ref.ParentHash)
-		}
-		if idx := ref.Number.Uint64() - n - 1; idx < uint64(len(cache)) {
-			return cache[idx]
-		}
-		// No luck in the cache, but we can start iterating from the last element we already know
-		lastKnownHash := cache[len(cache)-1]
-		lastKnownNumber := ref.Number.Uint64() - uint64(len(cache))
 
-		for {
-			header := chain.GetHeader(lastKnownHash, lastKnownNumber)
-			if header == nil {
-				break
+		// Use the cache if it is within 256 blocks from the head.
+		if n >= ref.Number.Uint64()-256 {
+			// If there's no hash cache yet, make one
+			if len(cache) == 0 {
+				cache = append(cache, ref.ParentHash)
 			}
-			cache = append(cache, header.ParentHash)
-			lastKnownHash = header.ParentHash
-			lastKnownNumber = header.Number.Uint64() - 1
-			if n == lastKnownNumber {
-				return lastKnownHash
+			if idx := ref.Number.Uint64() - n - 1; idx < uint64(len(cache)) {
+				return cache[idx]
+			}
+			// No luck in the cache, but we can start iterating from the last element we already know
+			lastKnownHash := cache[len(cache)-1]
+			lastKnownNumber := ref.Number.Uint64() - uint64(len(cache))
+
+			for {
+				header := chain.GetHeader(lastKnownHash, lastKnownNumber)
+				if header == nil {
+					break
+				}
+				cache = append(cache, header.ParentHash)
+				lastKnownHash = header.ParentHash
+				lastKnownNumber = header.Number.Uint64() - 1
+				if n == lastKnownNumber {
+					return lastKnownHash
+				}
+			}
+		} else {
+			if eip2935 {
+				var key common.Hash
+				binary.BigEndian.PutUint64(key[24:], n)
+				return statedb.GetState(params.HistoryStorageAddress, key)
 			}
 		}
+
 		return common.Hash{}
 	}
 }

core/vm/evm.go

@@ -34,7 +34,7 @@ type (
 	TransferFunc func(StateDB, common.Address, common.Address, *big.Int)
 	// GetHashFunc returns the n'th block hash in the blockchain
 	// and is used by the BLOCKHASH EVM op code.
-	GetHashFunc func(uint64) common.Hash
+	GetHashFunc func(uint64, StateDB, bool) common.Hash
 )
 
 func (evm *EVM) precompile(addr common.Address) (PrecompiledContract, bool) {

core/vm/instructions.go

@@ -441,13 +441,17 @@ func opBlockhash(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) (
 	}
 	var upper, lower uint64
 	upper = interpreter.evm.Context.BlockNumber.Uint64()
-	if upper < 257 {
-		lower = 0
-	} else {
+	evm := interpreter.evm
+
+	// After Prague, the values preceding FORKNUM will be 0,
+	// as requested in EIP-2935. So it's fine to allow 0 as
+	// the lower bound.
+	if !evm.chainRules.IsPrague && upper >= 257 {
 		lower = upper - 256
 	}
+
 	if num64 >= lower && num64 < upper {
-		num.SetBytes(interpreter.evm.Context.GetHash(num64).Bytes())
+		num.SetBytes(evm.Context.GetHash(num64, evm.StateDB, evm.chainRules.IsPrague).Bytes())
 	} else {
 		num.Clear()
 	}

core/vm/runtime/runtime.go

@@ -50,7 +50,7 @@ type Config struct {
 	Random      *common.Hash
 
 	State     *state.StateDB
-	GetHashFn func(n uint64) common.Hash
+	GetHashFn vm.GetHashFunc
 }
 
 // sets defaults on the config
@@ -90,7 +90,7 @@ func setDefaults(cfg *Config) {
 		cfg.BlockNumber = new(big.Int)
 	}
 	if cfg.GetHashFn == nil {
-		cfg.GetHashFn = func(n uint64) common.Hash {
+		cfg.GetHashFn = func(n uint64, _ vm.StateDB, _ bool) common.Hash {
 			return common.BytesToHash(crypto.Keccak256([]byte(new(big.Int).SetUint64(n).String())))
 		}
 	}