GM Price Oracle

GM Lending/Looping asset prices are obtained via a combination of the USDC Chainlink Oracle and previously deployed GMI Price Oracle contracts. As such, this current Oracle version behaves more like a Price Router in practice, but for simplicity's and posterity's sakes, it is labeled as a Price Oracle here.

At deployment, the Oracle contract stores addresses (the GMX GM token addresses and the USDC token address) for use in getUnderlyingPrice().

constructor

Sets msg.sender as the owner and _authorityContract as the Authority (both hereafter referred to as Admin). It then stores the addresses for the arbSequencerUptimeFeed and usdcUSD_ARBPriceFeed.

Parameters:

Name	Type	Description
_authorityContract	Authority	The Authority contract for the Oracle

updateChainlinkFeeds

function updateChainlinkFeeds(address _sequencerUptimeFeed, address _usdcPriceFeed, uint256 _usdcFeedHeartbeat) external requiresAuth

Updates/stores the Chainlink Arbitrum Sequencer Uptime Feed and the USDC Price Feed, along with its heartbeat. Only the Admin can call this function. The Sequencer Uptime Feed address is typecast to the AggregatorV3Interface type. Upon success, the call emits an OracleFeedsUpdated event with all three arguments as parameters.

Parameters:

Name	Type	Description
_sequencerUptimeFeed	address	The address for the Chainlink Arbitrum Sequencer Uptime Feed
usdcUSD_ARBPriceFeed	address	The address of the Chainlink USDC Price Feed for Arbitrum Mainnet
usdcFeedHeartbeat	uint256	Time interval for Chainlink Price Feeds

getUnderlyingPrice

function getUnderlyingPrice(ERC20 asset) public view returns (uint256)

Retrieves the current price of asset. If the asset is USDC, then the function calls the internal function _getPriceFromChainlink() and relays the USDC price returned by that function call (see the section below for details). Since the Chainlink USDC Price Feed returns 8 decimals, the answer is scaled up by 1e10 to 18 decimals. If the asset is a valid GM token (gmBTC, gmETH, or gmSOL), then the respective GMI price oracle contract is stored in the oracle variable. getPrice() is then called on the oracle instance, and the final price is returned. If the asset is not a valid GM token, then the call reverts.

To see how getPrice() interacts with GMX architecture to retrieve current asset prices, please head to the GMI Token Oracles section.

Parameters:

Name	Type	Description
asset	ERC20	Retrieves the price for this asset

Returns:

Name	Type	Description
x	uint256	If a GM token, the is determined by the GMX reader contract. If USDC, the price is returned by the Chainlink Arbitrum Mainnet USDC Price Feed. The price will have 18 decimals.

_getPriceFromChainlink

function _getPriceFromChainlink(address feedId) internal view returns (uint256)

Retrieves the current price of Chainlink's Arbitrum Mainnet USDC Price Feed. The function first calls latestRoundData() on the Sequencer Uptime Feed instance to retrieve the latest uptimeAnswer and startedAt. If uptimeAnswer does not equal 0, the Arbitrum Sequencer is down, and the function call reverts. If uptimeAnswer equals 0, then the Arb Sequencer is up. If the sequencer has just gone down, but was started back up, calls made within the GRACE_PERIOD of 1 hour will revert. Once the sequencer has been up for longer than an hour, calls will function normally.

The function then calls latestRoundData() on the price feed instance to retrieve the latest answer and updatedAt time. If updatedAt is less than block.timestamp - usdcFeedHeartbeat, the returned price is considered "stale," and the function will revert.

If the Arbitrum Sequencer is up and the Price Feed price is not stale, the price is returned by the function.

Parameters:

Name	Type	Description
asset	ERC20	The token to retrieve the price for

Returns:

Name	Type	Description
answer	uint256	The Oracle-returned price of the token. (USDC price uses 8 decimals.)