Standard L2 Genesis

Table of Contents

• Overview
• Chain Constants on L1
  • ConfigType
• SystemConfig
  • ConfigUpdate
  • Initialization
  • Interface
    • Fee Vault Config
      • setBaseFeeVaultConfig
      • setL1FeeVaultConfig
      • setSequencerFeeVaultConfig
• OptimismPortal
  • Interface
    • setConfig
    • upgrade
• SuperchainConfig
  • SuperchainConfig Constants
  • Interface
  • Initialization
• Deterministic genesis state
• Chain Constants on L2
• Predeploys
  • ProxyAdmin
    • Rationale
  • L1Block
    • Storage
    • Interface
      • setIsthmus
      • setConfig
      • getConfig
  • FeeVault
    • Interface
      • config
  • L2CrossDomainMessenger
    • Interface
  • L2ERC721Bridge
    • Interface
  • L2StandardBridge
    • Interface
  • OptimismMintableERC721Factory
• Security Considerations
  • GovernanceToken

Overview

The SystemConfig and OptimismPortal are updated with a new flow for chain configurability.

Chain Constants on L1

ConfigType

The ConfigType enum represents configuration that can be modified.

SystemConfig

ConfigUpdate

The following ConfigUpdate event is defined where the CONFIG_VERSION is uint256(0):

Initialization

The following actions should happen during the initialization of the SystemConfig:

• emit ConfigUpdate.BATCHER
• emit ConfigUpdate.FEE_SCALARS
• emit ConfigUpdate.GAS_LIMIT
• emit ConfigUpdate.UNSAFE_BLOCK_SIGNER
• emit ConfigUpdate.EIP_1559_PARAMS
• setConfig(SET_GAS_PAYING_TOKEN)
• setConfig(SET_BASE_FEE_VAULT_CONFIG)
• setConfig(SET_L1_FEE_VAULT_CONFIG)
• setConfig(SET_SEQUENCER_FEE_VAULT_CONFIG)
• setConfig(SET_L1_CROSS_DOMAIN_MESSENGER_ADDRESS)
• setConfig(SET_L1_ERC_721_BRIDGE_ADDRESS)
• setConfig(SET_L1_STANDARD_BRIDGE_ADDRESS)
• setConfig(SET_REMOTE_CHAIN_ID)

These actions MAY only be triggered if there is a diff to the value.

Interface

Fee Vault Config

For each FeeVault, there is a setter for its config. The arguments to the setter include the RECIPIENT, the MIN_WITHDRAWAL_AMOUNT and the WithdrawalNetwork. Each of these functions should be public and only callable by the chain governor.

Each function calls OptimismPortal.setConfig(ConfigType,bytes) with its corresponding ConfigType.

setBaseFeeVaultConfig

function setBaseFeeVaultConfig(address,uint256,WithdrawalNetwork)

setL1FeeVaultConfig

function setL1FeeVaultConfig(address,uint256,WithdrawalNetwork)

setSequencerFeeVaultConfig

function setSequencerFeeVaultConfig(address,uint256,WithdrawalNetwork)

OptimismPortal

The OptimismPortal is updated to emit a special system TransactionDeposited event.

Interface

setConfig

The setConfig function MUST only be callable by the SystemConfig. This ensures that the SystemConfig is the single source of truth for chain operator ownership.

function setConfig(ConfigType,bytes)

This function emits a TransactionDeposited event.

event TransactionDeposited(address indexed from, address indexed to, uint256 indexed version, bytes opaqueData);

The following fields are included:

• from is the DEPOSITOR_ACCOUNT
• to is Predeploys.L1Block
• version is uint256(0)
• opaqueData is the tightly packed transaction data where mint is 0, value is 0, the gasLimit is 200_000, isCreation is false and the data is abi.encodeCall(L1Block.setConfig, (_type, _value))

upgrade

The upgrade function MUST only be callable by the UPGRADER role as defined in the SuperchainConfig.

function upgrade(bytes memory _data) external

This function emits a TransactionDeposited event.

event TransactionDeposited(address indexed from, address indexed to, uint256 indexed version, bytes opaqueData);

The following fields are included:

• from is the DEPOSITOR_ACCOUNT
• to is Predeploys.ProxyAdmin
• version is uint256(0)
• opaqueData is the tightly packed transaction data where mint is 0, value is 0, the gasLimit is 200_000, isCreation is false and the data is the data passed into upgrade.

SuperchainConfig

The SuperchainConfig contract is updated with a new role that has the ability to issue deposit transactions from the identity of the DEPOSITOR_ACCOUNT that call the L2 ProxyAdmin.

SuperchainConfig Constants

Interface

function upgrader() public view returns (address)

Initialization

The upgrader can only be set during initialization.

Deterministic genesis state

This upgrade enables a deterministic L2 genesis state by moving all network specific configuration out of the initial L2 genesis state. All network specific configuration is sourced from deposit transactions during the initialization of the SystemConfig.

Chain Constants on L2

Predeploys

All network specific configuration is moved to a single contract, the L1Block predeploy. All predeploys make calls to the L1Block contract to fetch network specific configuration rather than reading it from local state.

graph LR
  subgraph L1
  SystemConfig -- "setConfig(uint8,bytes)" --> OptimismPortal
  end
  subgraph L2
  L1Block
  BaseFeeVault -- "getConfig(ConfigType.GAS_PAYING_TOKEN)(address,uint256,uint8)" --> L1Block
  SequencerFeeVault -- "getConfig(ConfigType.SEQUENCER_FEE_VAULT_CONFIG)(address,uint256,uint8)" --> L1Block
  L1FeeVault -- "getConfig(ConfigType.L1_FEE_VAULT_CONFIG)(address,uint256,uint8)" --> L1Block
  L2CrossDomainMessenger -- "getConfig(ConfigType.L1_CROSS_DOMAIN_MESSENGER_ADDRESS)(address)" --> L1Block
  L2StandardBridge -- "getConfig(ConfigType.L1_STANDARD_BRIDGE_ADDRESS)(address)" --> L1Block
  L2ERC721Bridge -- "getConfig(ConfigType.L1_ERC721_BRIDGE_ADDRESS)(address)" --> L1Block
  OptimismMintableERC721Factory -- "getConfig(ConfigType.REMOTE_CHAIN_ID)(uint256)" --> L1Block
  end
  OptimismPortal -- "setConfig(uint8,bytes)" --> L1Block

ProxyAdmin

The ProxyAdmin is updated to have its owner be the DEPOSITOR_ACCOUNT. This means that it can be deterministically called by network upgrade transactions or by special deposit transactions emitted by the OptimismPortal that assume the identity of the DEPOSITOR_ACCOUNT.

Rationale

It is much easier to manage the overall roles of the full system under this model. The owner of the ProxyAdmin can upgrade any of the predeploys, meaning it can write storage slots that correspond to withdrawals. This ensures that only the system or a chain governor can issue upgrades to the predeploys.

L1Block

Storage

The following storage slots are defined:

• BASE_FEE_VAULT_CONFIG
• L1_FEE_VAULT_CONFIG
• SEQUENCER_FEE_VAULT_CONFIG
• L1_CROSS_DOMAIN_MESSENGER_ADDRESS
• L1_ERC_721_BRIDGE_ADDRESS
• L1_STANDARD_BRIDGE_ADDRESS
• REMOTE_CHAIN_ID

Each slot MUST have a defined ConfigType that authorizes the setting of the storage slot via a deposit transaction from the DEPOSITOR_ACCOUNT.

Interface

setIsthmus

This function is meant to be called once on the activation block of the holocene network upgrade. It MUST only be callable by the DEPOSITOR_ACCOUNT once. When it is called, it MUST call call each getter for the network specific config and set the returndata into storage.

setConfig

This function MUST only be callable by the DEPOSITOR_ACCOUNT. It modifies the storage directly of the L1Block contract. It MUST handle all defined ConfigTypes. To ensure a simple ABI, the bytes value MUST be abi decoded based on the ConfigType.

function setConfig(ConfigType,bytes)

Note that ConfigType is an enum which is an alias for a uint8.

getConfig

This function is called by each contract with the appropriate ConfigType to fetch the network specific configuration. Using this pattern reduces the ABI of the L1Block contract by removing the need for special getters for each piece of config.

function getConfig(ConfigType)(bytes)

The caller needs to ABI decode the data into the desired type.

FeeVault

The following changes apply to each of the BaseFeeVault, the L1FeeVault and the SequencerFeeVault.

Interface

The following functions are updated to read from the L1Block contract:

• recipient()(address)
• withdrawalNetwork()(WithdrawalNetwork)
• minWithdrawalAmount()(uint256)
• withdraw()

config

A new function is added to fetch the full Fee Vault Config.

function config()(address,uint256,WithdrawalNetwork)

L2CrossDomainMessenger

Interface

The following functions are updated to read from the L1Block contract by calling L1Block.getConfig(ConfigType.L1_CROSS_DOMAIN_MESSENGER_ADDRESS):

• otherMessenger()(address)
• OTHER_MESSENGER()(address)

L2ERC721Bridge

Interface

The following functions are updated to read from the L1Block contract by calling L1Block.getConfig(ConfigType.L1_ERC721_BRIDGE_ADDRESS):

• otherBridge()(address)
• OTHER_BRIDGE()(address)

L2StandardBridge

Interface

The following functions are updated to read from the L1Block contract by calling L1Block.getConfig(ConfigType.L1_STANDARD_BRIDGE_ADDRESS):

• otherBridge()(address)
• OTHER_BRIDGE()(address)

OptimismMintableERC721Factory

The chain id is no longer read from storage but instead is read from the L1Block contract by calling L1Block.getConfig(ConfigType.REMOTE_CHAIN_ID)

Security Considerations

GovernanceToken

The predeploy defined by GovernanceToken should be an empty account until it is defined by a future hardfork.