make extradata configurable for the genesis block generator

op-chain-ops/genesis/config.go

@@ -72,6 +72,9 @@ type DeployConfig struct {
 	// Seconds after genesis block that Regolith hard fork activates. 0 to activate at genesis. Nil to disable regolith
 	L2GenesisRegolithTimeOffset *hexutil.Uint64 `json:"l2GenesisRegolithTimeOffset,omitempty"`
 
+	// Configurable extradata. Will default to []byte("BEDROCK") if left unspecified.
+	L2GenesisBlockExtraData []byte `json:"l2GenesisBlockExtraData"`
+
 	// Owner of the ProxyAdmin predeploy
 	ProxyAdminOwner common.Address `json:"proxyAdminOwner"`
 	// Owner of the system on L1

op-chain-ops/genesis/config_test.go

@@ -14,14 +14,16 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestConfigMarshalUnmarshal(t *testing.T) {
+func TestConfigDataMarshalUnmarshal(t *testing.T) {
 	b, err := os.ReadFile("testdata/test-deploy-config-full.json")
 	require.NoError(t, err)
+
 	dec := json.NewDecoder(bytes.NewReader(b))
 	decoded := new(DeployConfig)
 	require.NoError(t, dec.Decode(decoded))
-	encoded, err := json.MarshalIndent(decoded, "", "  ")
+	require.EqualValues(t, "non-default value", string(decoded.L2GenesisBlockExtraData))
 
+	encoded, err := json.MarshalIndent(decoded, "", "  ")
 	require.NoError(t, err)
 	require.JSONEq(t, string(b), string(encoded))
 }

op-chain-ops/genesis/genesis.go

@@ -74,8 +74,13 @@ func NewL2Genesis(config *DeployConfig, block *types.Block) (*core.Genesis, erro
 		difficulty = newHexBig(0)
 	}
 
+	extraData := config.L2GenesisBlockExtraData
+	if extraData == nil {
+		// L2GenesisBlockExtraData is optional, so use a default value when nil
+		extraData = BedrockTransitionBlockExtraData
+	}
 	// Ensure that the extradata is valid
-	if size := len(BedrockTransitionBlockExtraData); size > 32 {
+	if size := len(extraData); size > 32 {
 		return nil, fmt.Errorf("transition block extradata too long: %d", size)
 	}
 
@@ -83,7 +88,7 @@ func NewL2Genesis(config *DeployConfig, block *types.Block) (*core.Genesis, erro
 		Config:     &optimismChainConfig,
 		Nonce:      uint64(config.L2GenesisBlockNonce),
 		Timestamp:  block.Time(),
-		ExtraData:  BedrockTransitionBlockExtraData,
+		ExtraData:  extraData,
 		GasLimit:   uint64(gasLimit),
 		Difficulty: difficulty.ToInt(),
 		Mixhash:    config.L2GenesisBlockMixHash,

op-chain-ops/genesis/testdata/test-deploy-config-full.json

@@ -36,6 +36,7 @@
   "l2GenesisBlockGasUsed": "0x0",
   "l2GenesisBlockParentHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
   "l2GenesisBlockBaseFeePerGas": "0x3b9aca00",
+  "l2GenesisBlockExtraData": "bm9uLWRlZmF1bHQgdmFsdWU=",
   "baseFeeVaultRecipient": "0x42000000000000000000000000000000000000f5",
   "l1FeeVaultRecipient": "0x42000000000000000000000000000000000000f6",
   "sequencerFeeVaultRecipient": "0x42000000000000000000000000000000000000f7",