-
Notifications
You must be signed in to change notification settings - Fork 234
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
1 parent
79c911c
commit 40c222b
Showing
2 changed files
with
150 additions
and
11 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,138 @@ | ||
# ADR 010: Custom 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. The solution is to provide precompile, allowing users to access to cosmos features through smart contracts. | ||
A precompiled behave like a smart contract, it is designed by an address and can be invoked by other smart contracts. The difference is that its execution is not inside a smart contract. | ||
App-chain specific logics can be embedded to the pre-compiled so that it could be used to expose cosmos native features at 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 logics 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) | ||
|
||
In the future, we are planning to maintain the following fork permanently | ||
`github.com/evmos/go-ethereum` | ||
|
||
### 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 | ||
|
||
#### Relayer | ||
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 | ||
) | ||
|
||
``` | ||
|
||
-> TODO describe the change in go-relayer | ||
|
||
#### ICA | ||
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 be able to track the result of the transaction `submitMsgs` so that the user or the smart contract can respond accordingly. | ||
The function `submitMsgs` returns a sequence number that can be used by the user or smart contract to track the state of the msg using the precompiled `ICACallback`. | ||
|
||
|
||
```solidity | ||
interface IICACallback { | ||
function onPacketResultCallback(uint64 seq, bool ack) external payable returns (bool); | ||
} | ||
``` | ||
|
||
|
||
### Precompiled gas cost | ||
|
||
A precompiled is basically an op-code at the evm layer thus, it has a constant cost. Because a stateful precompiled can change the state, it is much harder to define a specific cost it. | ||
To be fair, we are evaluating the cost of a pre-compile based on the past history. | ||
We are planning to tune the costs 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 |