diff --git a/docs/architecture/README.md b/docs/architecture/README.md index f12322b321..fe93d214eb 100644 --- a/docs/architecture/README.md +++ b/docs/architecture/README.md @@ -25,14 +25,15 @@ To suggest an ADR, please make use of the [ADR template](./adr-template.md) prov ## Table of Contents -| ADR \# | Description | Status | -|---------------------|----------------------------------------------------------------------------|----------| -| [001](./adr-001.md) | Disable Gravity Bridge at Genesis | Accepted | -| [002](./adr-002.md) | Use a custom fork of ibc-go | Accepted | -| [003](./adr-003.md) | Add Fee Market Module | Accepted | -| [004](./adr-004.md) | Tokens conversion in Cronos | Accepted | -| [005](./adr-005.md) | Cross-chain Validation for Gravity Bridge | Rejected | -| [006](./adr-006.md) | Migrating CRC20 contract to CRC21 standard | Rejected | -| [007](./adr-007.md) | Generic event format for evm-hook actions | Accepted | -| [008](./adr-008.md) | Denom and Contract Mapping Enhancement for Bi-Directional Token Conversion | Accepted | -| [009](./adr-009.md) | Permissioned addresses in Cronos | Accepted | +| ADR \# | Description | Status | +|----------------------|----------------------------------------------------------------------------|----------| +| [001](./adr-001.md) | Disable Gravity Bridge at Genesis | Accepted | +| [002](./adr-002.md) | Use a custom fork of ibc-go | Accepted | +| [003](./adr-003.md) | Add Fee Market Module | Accepted | +| [004](./adr-004.md) | Tokens conversion in Cronos | Accepted | +| [005](./adr-005.md) | Cross-chain Validation for Gravity Bridge | Rejected | +| [006](./adr-006.md) | Migrating CRC20 contract to CRC21 standard | Rejected | +| [007](./adr-007.md) | Generic event format for evm-hook actions | Accepted | +| [008](./adr-008.md) | Denom and Contract Mapping Enhancement for Bi-Directional Token Conversion | Accepted | +| [009](./adr-009.md) | Permissioned addresses in Cronos | Accepted | +| [0010](./adr-010.md) | Precompiled for app-chain | Accepted | diff --git a/docs/architecture/adr-010.md b/docs/architecture/adr-010.md new file mode 100644 index 0000000000..dd63fd8b1a --- /dev/null +++ b/docs/architecture/adr-010.md @@ -0,0 +1,133 @@ +# ADR 01-: Precompiled for app-chain + +## Changelog +* 2023-10-02: first draft + +## Context + +Cronos is an EVM-compatible built on Cosmos SDK. The "ethermint" module allows a full compatibility and interoperability with Ethereum. However, it comes with the sacrifice of cosmos native features or cosmos interchain features (IBC) +as end-users are not able to access them through an ethereum transaction format. The solution is to provide precompile, allowing users to access to cosmos features through smart contract. +A precompiled behave like smart contracts, it is designed by an addressed and can be invoked by other smart contracts. The difference is that its execution is not inside a smart contract. +App-chain logic can be embedded to the pre-compiled so that it could be used to expose cosmos native feature to the EVM layer. + + +## Decision + +### Fork go-ethereum for stateful precompiled support + +One of the major difficulties in supporting pre-compiled is the lack of flexibility in geth for defining custom precompiled and its non-ability to modify the state. +We made the choice of forking geth and implement additional interfaces and logic so that app-chain can define its own precompiled. + +The PR [#7](https://github.com/evmos/go-ethereum/pull/7) implements the ability to set custom precompiled to the EVM. +while this PR [#10](https://github.com/evmos/go-ethereum/pull/10) allows the precompiled to modify the state (for stateful precompiled) + +### Implement pre-compiled for cosmos native module + +We provide pre-compile for cosmos native module such as bank or staking. + +The input and output of methods are mapped with those defined cosmos native transactions + +```solidity + +interface IBankModule { + function mint(address,uint256) external payable returns (bool); + function balanceOf(address,address) external view returns (uint256); + function burn(address,uint256) external payable returns (bool); + function transfer(address,address,uint256) external payable returns (bool); +} + + + +interface IStakingModule { + # to be completed +} +``` + +To call a precompiled, create an instance of the module interface with the precompiled address. +The methods are ABI encoded, and can be called directly as calling the function through the interface: + + +```solidity + +address constant bankContract = 0x0000000000000000000000000000000000000064; +IBankModule bank = IBankModule(bankContract); +bank.transfer(msg.sender, recipient, amount); + +``` + + +### Implement pre-compiled for cosmos interchain communication + +One of the benefits of supporting precompiled for IBC is that it would be possible to track the change of state triggered by the ibc transaction with ethereum receipts. + +For that reason we are exposing all relayer related actions to the evm layer. An action is defined by a 4 bytes prefix. + +```go + +const ( + prefixSize4Bytes = 4 + // Client + prefixCreateClient = iota + 1 + prefixUpdateClient + prefixUpgradeClient + prefixSubmitMisbehaviour + // Connection + prefixConnectionOpenInit + prefixConnectionOpenTry + prefixConnectionOpenAck + prefixConnectionOpenConfirm + // Channel + prefixChannelOpenInit + prefixChannelOpenTry + prefixChannelOpenAck + prefixChannelOpenConfirm + prefixChannelCloseInit + prefixChannelCloseConfirm + prefixRecvPacket + prefixAcknowledgement + prefixTimeout + prefixTimeoutOnClose +) + +``` + +-> go relayer changes + +For ICA, we are following the same standard as for the cosmos module + +The ICA precompiled interface is defined by: + +```solidity +interface IICAModule { + event SubmitMsgsResult(uint64 seq); + function registerAccount(string calldata connectionID, string calldata version) external payable returns (bool); + function queryAccount(string calldata connectionID, address addr) external view returns (string memory); + function submitMsgs(string calldata connectionID, bytes calldata data, uint256 timeout) external payable returns (uint64); +} +``` + +In case of ICA, it is important to receives the result of the transaction `submitMsgs` for the user or the smart contract to respond accordingly. +The function `submitMsgs` return a sequence number that can be used by the user or smart contract to track the state of the msg using the ICA callback precompiled. + + +```solidity +interface IICACallback { + function onPacketResultCallback(uint64 seq, bool ack) external payable returns (bool); +} + +``` + + +### Precompiled gas cost + +A precompiled acts as an op-code in the evm layer and has a constant cost. Because a stateful precompiled can change the state, it is much harder to define a specific cost for an action. +To be fair, we are evaluating the cost of a pre-compile based on the past history and we are planning to tune the cost further in the future. + +## Further discussions + + +## References + +* https://github.com/crypto-org-chain/cronos/pull/837 +* https://github.com/crypto-org-chain/cronos/pull/1163 +* https://github.com/crypto-org-chain/cronos/pull/1014 \ No newline at end of file