From b4460a8f74ae5b82309e44c391d70faeb4c747d9 Mon Sep 17 00:00:00 2001
From: Guillaume Ballet <3272758+gballet@users.noreply.github.com>
Date: Fri, 19 Jan 2024 17:55:21 +0100
Subject: [PATCH] write parent block hash to system contract

---
 cmd/evm/internal/t8ntool/execution.go |  4 ++++
 cmd/evm/internal/t8ntool/gen_stenv.go |  6 ++++++
 core/state_processor.go               | 10 ++++++++++
 miner/worker.go                       |  3 +++
 params/protocol_params.go             |  2 ++
 5 files changed, 25 insertions(+)

diff --git a/cmd/evm/internal/t8ntool/execution.go b/cmd/evm/internal/t8ntool/execution.go
index b654cb2196..5f39794a18 100644
--- a/cmd/evm/internal/t8ntool/execution.go
+++ b/cmd/evm/internal/t8ntool/execution.go
@@ -89,6 +89,7 @@ type stEnv struct {
 	ParentExcessBlobGas   *uint64                             `json:"parentExcessBlobGas,omitempty"`
 	ParentBlobGasUsed     *uint64                             `json:"parentBlobGasUsed,omitempty"`
 	ParentBeaconBlockRoot *common.Hash                        `json:"parentBeaconBlockRoot"`
+	ParentHash            *common.Hash                        `json:"parentHash,omitempty"`
 }
 
 type stEnvMarshaling struct {
@@ -190,6 +191,9 @@ func (pre *Prestate) Apply(vmConfig vm.Config, chainConfig *params.ChainConfig,
 		evm := vm.NewEVM(vmContext, vm.TxContext{}, statedb, chainConfig, vmConfig)
 		core.ProcessBeaconBlockRoot(*beaconRoot, evm, statedb)
 	}
+	if chainConfig.IsPrague(big.NewInt(int64(pre.Env.Number)), pre.Env.Timestamp) {
+		core.ProcessParentBlockHash(statedb, pre.Env.Number-1, *pre.Env.ParentHash)
+	}
 
 	for i := 0; txIt.Next(); i++ {
 		tx, err := txIt.Tx()
diff --git a/cmd/evm/internal/t8ntool/gen_stenv.go b/cmd/evm/internal/t8ntool/gen_stenv.go
index d47db4a876..0c296395e2 100644
--- a/cmd/evm/internal/t8ntool/gen_stenv.go
+++ b/cmd/evm/internal/t8ntool/gen_stenv.go
@@ -37,6 +37,7 @@ func (s stEnv) MarshalJSON() ([]byte, error) {
 		ParentExcessBlobGas   *math.HexOrDecimal64                `json:"parentExcessBlobGas,omitempty"`
 		ParentBlobGasUsed     *math.HexOrDecimal64                `json:"parentBlobGasUsed,omitempty"`
 		ParentBeaconBlockRoot *common.Hash                        `json:"parentBeaconBlockRoot"`
+		ParentHash            *common.Hash                        `json:"parentHash,omitempty"`
 	}
 	var enc stEnv
 	enc.Coinbase = common.UnprefixedAddress(s.Coinbase)
@@ -59,6 +60,7 @@ func (s stEnv) MarshalJSON() ([]byte, error) {
 	enc.ParentExcessBlobGas = (*math.HexOrDecimal64)(s.ParentExcessBlobGas)
 	enc.ParentBlobGasUsed = (*math.HexOrDecimal64)(s.ParentBlobGasUsed)
 	enc.ParentBeaconBlockRoot = s.ParentBeaconBlockRoot
+	enc.ParentHash = s.ParentHash
 	return json.Marshal(&enc)
 }
 
@@ -85,6 +87,7 @@ func (s *stEnv) UnmarshalJSON(input []byte) error {
 		ParentExcessBlobGas   *math.HexOrDecimal64                `json:"parentExcessBlobGas,omitempty"`
 		ParentBlobGasUsed     *math.HexOrDecimal64                `json:"parentBlobGasUsed,omitempty"`
 		ParentBeaconBlockRoot *common.Hash                        `json:"parentBeaconBlockRoot"`
+		ParentHash            *common.Hash                        `json:"parentHash,omitempty"`
 	}
 	var dec stEnv
 	if err := json.Unmarshal(input, &dec); err != nil {
@@ -154,5 +157,8 @@ func (s *stEnv) UnmarshalJSON(input []byte) error {
 	if dec.ParentBeaconBlockRoot != nil {
 		s.ParentBeaconBlockRoot = dec.ParentBeaconBlockRoot
 	}
+	if dec.ParentHash != nil {
+		s.ParentHash = dec.ParentHash
+	}
 	return nil
 }
diff --git a/core/state_processor.go b/core/state_processor.go
index 9a4333f723..0bcdcc4260 100644
--- a/core/state_processor.go
+++ b/core/state_processor.go
@@ -17,6 +17,7 @@
 package core
 
 import (
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"math/big"
@@ -79,6 +80,9 @@ func (p *StateProcessor) Process(block *types.Block, statedb *state.StateDB, cfg
 	if beaconRoot := block.BeaconRoot(); beaconRoot != nil {
 		ProcessBeaconBlockRoot(*beaconRoot, vmenv, statedb)
 	}
+	if p.config.IsPrague(block.Number(), block.Time()) {
+		ProcessParentBlockHash(statedb, block.NumberU64()-1, block.ParentHash())
+	}
 	// Iterate over and process the individual transactions
 	for i, tx := range block.Transactions() {
 		msg, err := TransactionToMessage(tx, signer, header.BaseFee)
@@ -189,3 +193,9 @@ func ProcessBeaconBlockRoot(beaconRoot common.Hash, vmenv *vm.EVM, statedb *stat
 	_, _, _ = vmenv.Call(vm.AccountRef(msg.From), *msg.To, msg.Data, 30_000_000, common.Big0)
 	statedb.Finalise(true)
 }
+
+func ProcessParentBlockHash(statedb *state.StateDB, prevNumber uint64, prevHash common.Hash) {
+	var key common.Hash
+	binary.BigEndian.PutUint64(key[24:], prevNumber)
+	statedb.SetState(params.HistoryStorageAddress, key, prevHash)
+}
diff --git a/miner/worker.go b/miner/worker.go
index 2ed91cc187..7053d65d62 100644
--- a/miner/worker.go
+++ b/miner/worker.go
@@ -978,6 +978,9 @@ func (w *worker) prepareWork(genParams *generateParams) (*environment, error) {
 		vmenv := vm.NewEVM(context, vm.TxContext{}, env.state, w.chainConfig, vm.Config{})
 		core.ProcessBeaconBlockRoot(*header.ParentBeaconRoot, vmenv, env.state)
 	}
+	if w.chainConfig.IsPrague(header.Number, header.Time) {
+		core.ProcessParentBlockHash(env.state, header.Number.Uint64()-1, header.ParentHash)
+	}
 	return env, nil
 }
 
diff --git a/params/protocol_params.go b/params/protocol_params.go
index 7eb63e89ac..748351b694 100644
--- a/params/protocol_params.go
+++ b/params/protocol_params.go
@@ -188,4 +188,6 @@ var (
 	BeaconRootsStorageAddress = common.HexToAddress("0x000F3df6D732807Ef1319fB7B8bB8522d0Beac02")
 	// SystemAddress is where the system-transaction is sent from as per EIP-4788
 	SystemAddress common.Address = common.HexToAddress("0xfffffffffffffffffffffffffffffffffffffffe")
+	// HistoryStorageAddress is where the historical block hashes are stored.
+	HistoryStorageAddress common.Address = common.HexToAddress("0xfffffffffffffffffffffffffffffffffffffffe")
 )