Merge pull request #120 from aave/feat/isolation-mode

Feat/isolation mode

contracts/interfaces/IPoolConfigurator.sol

@@ -215,6 +215,13 @@ interface IPoolConfigurator {
     address indexed implementation
   );
 
+  /**
+   * @notice Emitted when the debt ceiling of an asset is set
+   * @param asset The address of the underlying asset of the reserve
+   * @param ceiling The new debt ceiling
+   **/
+  event DebtCeilingChanged(address indexed asset, uint256 ceiling);
+
   /**
    * @notice Emitted when a new risk admin is registered
    * @param admin The newly registered admin
@@ -439,4 +446,10 @@ interface IPoolConfigurator {
    * @param flashloanPremiumToProtocol The part of the premium sent to protocol
    */
   function updateFlashloanPremiumToProtocol(uint256 flashloanPremiumToProtocol) external;
+
+  /**
+   * @notice Sets the debt ceiling for an asset
+   * @param ceiling The new debt ceiling
+   */
+  function setDebtCeiling(address asset, uint256 ceiling) external;
 }

contracts/protocol/libraries/configuration/ReserveConfiguration.sol

@@ -25,6 +25,7 @@ library ReserveConfiguration {
   uint256 constant LIQUIDATION_PROTOCOL_FEE_MASK =  0xFFFFFFFFFFFFFFFFFFFFFF0000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF; // prettier-ignore
   uint256 constant EMODE_CATEGORY_MASK =            0xFFFFFFFFFFFFFFFFFFFF00FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF; // prettier-ignore
   uint256 constant UNBACKED_MINT_CAP_MASK =         0xFFFFFFFFFFF000000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF; // prettier-ignore
+  uint256 constant DEBT_CEILING_MASK =              0xFFF00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF; // prettier-ignore
 
   /// @dev For the LTV, the start bit is 0 (up to 15), hence no bitshifting is needed
   uint256 constant LIQUIDATION_THRESHOLD_START_BIT_POSITION = 16;
@@ -42,6 +43,7 @@ library ReserveConfiguration {
   uint256 constant LIQUIDATION_PROTOCOL_FEE_START_BIT_POSITION = 152;
   uint256 constant EMODE_CATEGORY_START_BIT_POSITION = 168;
   uint256 constant UNBACKED_MINT_CAP_START_BIT_POSITION = 176;
+  uint256 constant DEBT_CEILING_START_BIT_POSITION = 212;
 
   uint256 constant MAX_VALID_LTV = 65535;
   uint256 constant MAX_VALID_LIQUIDATION_THRESHOLD = 65535;
@@ -53,6 +55,7 @@ library ReserveConfiguration {
   uint256 constant MAX_VALID_LIQUIDATION_PROTOCOL_FEE = 10000;
   uint256 constant MAX_VALID_EMODE_CATEGORY = 255;
   uint256 constant MAX_VALID_UNBACKED_MINT_CAP = 68719476735;
+  uint256 constant MAX_VALID_DEBT_CEILING = 4294967296;
 
   /**
    * @notice Sets the Loan to Value of the reserve
@@ -356,6 +359,33 @@ library ReserveConfiguration {
     return (self.data & ~SUPPLY_CAP_MASK) >> SUPPLY_CAP_START_BIT_POSITION;
   }
 
+  /**
+   * @notice Sets the debt ceiling in isolation mode for the asset
+   * @param self The reserve configuration
+   * @param ceiling The maximum debt ceiling for the asset
+   **/
+  function setDebtCeiling(DataTypes.ReserveConfigurationMap memory self, uint256 ceiling)
+    internal
+    pure
+  {
+    require(ceiling <= MAX_VALID_DEBT_CEILING, Errors.RC_INVALID_DEBT_CEILING);
+
+    self.data = (self.data & DEBT_CEILING_MASK) | (ceiling << DEBT_CEILING_START_BIT_POSITION);
+  }
+
+  /**
+   * @notice Gets the debt ceiling for the asset if the asset is in isolation mode
+   * @param self The reserve configuration
+   * @return The debt ceiling (0 = isolation mode disabled)
+   **/
+  function getDebtCeiling(DataTypes.ReserveConfigurationMap memory self)
+    internal
+    pure
+    returns (uint256)
+  {
+    return (self.data & ~DEBT_CEILING_MASK) >> DEBT_CEILING_START_BIT_POSITION;
+  }
+
   /**
    * @notice Sets the liquidation protocol fee of the reserve
    * @param self The reserve configuration

contracts/protocol/libraries/configuration/UserConfiguration.sol

@@ -3,15 +3,20 @@ pragma solidity 0.8.7;
 
 import {Errors} from '../helpers/Errors.sol';
 import {DataTypes} from '../types/DataTypes.sol';
+import {ReserveConfiguration} from './ReserveConfiguration.sol';
 
 /**
  * @title UserConfiguration library
  * @author Aave
  * @notice Implements the bitmap logic to handle the user configuration
  */
 library UserConfiguration {
+  using ReserveConfiguration for DataTypes.ReserveConfigurationMap;
+
   uint256 internal constant BORROWING_MASK =
     0x5555555555555555555555555555555555555555555555555555555555555555;
+  uint256 internal constant COLLATERAL_MASK =
+    0xAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA;
 
   /**
    * @notice Sets if the user is borrowing the reserve identified by reserveIndex
@@ -102,7 +107,35 @@ library UserConfiguration {
   }
 
   /**
-   * @notice Validate a user has been borrowing from any reserve
+   * @notice Checks if a user has been supplying only one reserve as collateral
+   * @dev this uses a simple trick - if a number is a power of two (only one bit set) then n & (n - 1) == 0
+   * @param self The configuration object
+   * @return True if the user has been supplying as collateral one reserve, false otherwise
+   **/
+  function isUsingAsCollateralOne(DataTypes.UserConfigurationMap memory self)
+    internal
+    pure
+    returns (bool)
+  {
+    uint256 collateralData = self.data & COLLATERAL_MASK;
+    return collateralData & (collateralData - 1) == 0;
+  }
+
+  /**
+   * @notice Checks if a user has been supplying any reserve as collateral
+   * @param self The configuration object
+   * @return True if the user has been supplying as collateral any reserve, false otherwise
+   **/
+  function isUsingAsCollateralAny(DataTypes.UserConfigurationMap memory self)
+    internal
+    pure
+    returns (bool)
+  {
+    return self.data & COLLATERAL_MASK != 0;
+  }
+
+  /**
+   * @notice Checks if a user has been borrowing from any reserve
    * @param self The configuration object
    * @return True if the user has been borrowing any reserve, false otherwise
    **/
@@ -111,11 +144,56 @@ library UserConfiguration {
   }
 
   /**
-   * @notice Validate a user has not been using any reserve
+   * @notice Checks if a user has not been using any reserve for borrowing or supply
    * @param self The configuration object
    * @return True if the user has been borrowing any reserve, false otherwise
    **/
   function isEmpty(DataTypes.UserConfigurationMap memory self) internal pure returns (bool) {
     return self.data == 0;
   }
+
+  function getIsolationModeState(
+    DataTypes.UserConfigurationMap memory self,
+    mapping(address => DataTypes.ReserveData) storage reservesData,
+    mapping(uint256 => address) storage reservesList
+  )
+    internal
+    view
+    returns (
+      bool,
+      address,
+      uint256
+    )
+  {
+    if (!isUsingAsCollateralAny(self)) {
+      return (false, address(0), 0);
+    }
+    if (isUsingAsCollateralOne(self)) {
+      uint256 assetId = _getFirstAssetAsCollateralId(self);
+
+      address assetAddress = reservesList[assetId];
+      uint256 ceiling = reservesData[assetAddress].configuration.getDebtCeiling();
+      if (ceiling > 0) {
+        return (true, assetAddress, ceiling);
+      }
+    }
+    return (false, address(0), 0);
+  }
+
+  function _getFirstAssetAsCollateralId(DataTypes.UserConfigurationMap memory self)
+    internal
+    pure
+    returns (uint256)
+  {
+    unchecked {
+      uint256 collateralData = self.data & COLLATERAL_MASK;
+      uint256 firstCollateralPosition = collateralData & ~(collateralData - 1);
+      uint256 id;
+
+      while ((firstCollateralPosition >>= 2) > 0) {
+        id += 2;
+      }
+      return id / 2;
+    }
+  }
 }

contracts/protocol/libraries/helpers/Errors.sol

@@ -114,4 +114,9 @@ library Errors {
   string public constant RC_INVALID_UNBACKED_MINT_CAP = '103';
   string public constant VL_UNBACKED_MINT_CAP_EXCEEDED = '104';
   string public constant VL_PRICE_ORACLE_SENTINEL_CHECK_FAILED = '105';
+  string public constant RC_INVALID_DEBT_CEILING = '106';
+  string public constant PC_INVALID_DEBT_CEILING_ASSET_ALREADY_SUPPLIED = '107';
+  string public constant VL_INVALID_ISOLATION_MODE_BORROW_CATEGORY = '108';
+  string public constant VL_DEBT_CEILING_CROSSED = '109';
+  string public constant SL_USER_IN_ISOLATION_MODE = '110';
 }

contracts/protocol/libraries/logic/BorrowLogic.sol

@@ -8,6 +8,7 @@ import {IVariableDebtToken} from '../../../interfaces/IVariableDebtToken.sol';
 import {IAToken} from '../../../interfaces/IAToken.sol';
 import {IFlashLoanReceiver} from '../../../flashloan/interfaces/IFlashLoanReceiver.sol';
 import {UserConfiguration} from '../configuration/UserConfiguration.sol';
+import {ReserveConfiguration} from '../configuration/ReserveConfiguration.sol';
 import {Helpers} from '../helpers/Helpers.sol';
 import {Errors} from '../helpers/Errors.sol';
 import {WadRayMath} from '../math/WadRayMath.sol';
@@ -26,6 +27,7 @@ library BorrowLogic {
   using ReserveLogic for DataTypes.ReserveData;
   using SafeERC20 for IERC20;
   using UserConfiguration for DataTypes.UserConfigurationMap;
+  using ReserveConfiguration for DataTypes.ReserveConfigurationMap;
   using WadRayMath for uint256;
   using PercentageMath for uint256;
 
@@ -69,6 +71,12 @@ library BorrowLogic {
 
     reserve.updateState(reserveCache);
 
+    (
+      bool isolationModeActive,
+      address isolationModeCollateralAddress,
+      uint256 isolationModeDebtCeiling
+    ) = userConfig.getIsolationModeState(reserves, reservesList);
+
     ValidationLogic.validateBorrow(
       reserves,
       reservesList,
@@ -84,7 +92,10 @@ library BorrowLogic {
         params.reservesCount,
         params.oracle,
         params.userEModeCategory,
-        params.priceOracleSentinel
+        params.priceOracleSentinel,
+        isolationModeActive,
+        isolationModeCollateralAddress,
+        isolationModeDebtCeiling
       )
     );
 
@@ -114,6 +125,12 @@ library BorrowLogic {
       userConfig.setBorrowing(reserve.id, true);
     }
 
+    if (isolationModeActive) {
+      reserves[isolationModeCollateralAddress].isolationModeTotalDebt += Helpers.castUint128(
+        params.amount / 10**reserveCache.reserveConfiguration.getDecimals()
+      );
+    }
+
     reserve.updateInterestRates(
       reserveCache,
       params.asset,
@@ -139,6 +156,8 @@ library BorrowLogic {
   }
 
   function executeRepay(
+    mapping(address => DataTypes.ReserveData) storage reserves,
+    mapping(uint256 => address) storage reservesList,
     DataTypes.ReserveData storage reserve,
     DataTypes.UserConfigurationMap storage userConfig,
     DataTypes.ExecuteRepayParams memory params
@@ -185,6 +204,22 @@ library BorrowLogic {
       userConfig.setBorrowing(reserve.id, false);
     }
 
+    (bool isolationModeActive, address isolationModeCollateralAddress, ) = userConfig
+      .getIsolationModeState(reserves, reservesList);
+
+    if (isolationModeActive) {
+      uint128 isolationModeTotalDebt = reserves[isolationModeCollateralAddress]
+        .isolationModeTotalDebt;
+      // since the debt ceiling does not take into account the interest accrued, it might happen that amount repaid > debt in isolation mode
+      if (isolationModeTotalDebt < paybackAmount) {
+        reserves[isolationModeCollateralAddress].isolationModeTotalDebt = 0;
+      } else {
+        reserves[isolationModeCollateralAddress].isolationModeTotalDebt =
+          isolationModeTotalDebt -
+          Helpers.castUint128(paybackAmount / 10**reserveCache.reserveConfiguration.getDecimals());
+      }
+    }
+
     if (params.useATokens) {
       IAToken(reserveCache.aTokenAddress).burn(
         msg.sender,

contracts/protocol/libraries/logic/SupplyLogic.sol

@@ -45,6 +45,7 @@ library SupplyLogic {
 
   function executeSupply(
     mapping(address => DataTypes.ReserveData) storage reserves,
+    mapping(uint256 => address) storage reservesList,
     DataTypes.UserConfigurationMap storage userConfig,
     DataTypes.ExecuteSupplyParams memory params
   ) external {
@@ -66,8 +67,11 @@ library SupplyLogic {
     );
 
     if (isFirstSupply) {
-      userConfig.setUsingAsCollateral(reserve.id, true);
-      emit ReserveUsedAsCollateralEnabled(params.asset, params.onBehalfOf);
+      (bool isolationModeActive, , ) = userConfig.getIsolationModeState(reserves, reservesList);
+      if (!isolationModeActive) {
+        userConfig.setUsingAsCollateral(reserve.id, true);
+        emit ReserveUsedAsCollateralEnabled(params.asset, params.onBehalfOf);
+      }
     }
 
     emit Supply(params.asset, msg.sender, params.onBehalfOf, params.amount, params.referralCode);
@@ -168,8 +172,11 @@ library SupplyLogic {
 
       if (params.balanceToBefore == 0 && params.amount != 0) {
         DataTypes.UserConfigurationMap storage toConfig = usersConfig[params.to];
-        toConfig.setUsingAsCollateral(reserveId, true);
-        emit ReserveUsedAsCollateralEnabled(params.asset, params.to);
+        (bool isolationModeActive, , ) = toConfig.getIsolationModeState(reserves, reservesList);
+        if (!isolationModeActive) {
+          toConfig.setUsingAsCollateral(reserveId, true);
+          emit ReserveUsedAsCollateralEnabled(params.asset, params.to);
+        }
       }
     }
   }
@@ -192,11 +199,14 @@ library SupplyLogic {
 
     ValidationLogic.validateSetUseReserveAsCollateral(reserveCache, userBalance);
 
-    userConfig.setUsingAsCollateral(reserve.id, useAsCollateral);
-
     if (useAsCollateral) {
+      (bool isolationModeActive, , ) = userConfig.getIsolationModeState(reserves, reservesList);
+      require(!isolationModeActive, Errors.SL_USER_IN_ISOLATION_MODE);
+
+      userConfig.setUsingAsCollateral(reserve.id, true);
       emit ReserveUsedAsCollateralEnabled(asset, msg.sender);
     } else {
+      userConfig.setUsingAsCollateral(reserve.id, false);
       ValidationLogic.validateHFAndLtv(
         reserves,
         reservesList,

contracts/protocol/libraries/logic/ValidationLogic.sol

@@ -39,6 +39,11 @@ library ValidationLogic {
   uint256 public constant REBALANCE_UP_USAGE_RATIO_THRESHOLD = 0.95 * 1e27; //usage ratio of 95%
   uint256 public constant MINIMUM_HEALTH_FACTOR_LIQUIDATION_THRESHOLD = 0.95 * 1e18;
 
+  // for borrowings in isolation mode, we give for granted that the eMode category for stablecoins is the category with id 1.
+  // this MUST be kept into account when configuring the stablecoins eMode category, otherwise users depositing asset in isolation
+  // mode will NOT be able to borrow.
+  uint256 public constant DEFAULT_ISOLATION_MODE_BORROW_CATEGORY = 1;
+
   /**
    * @notice Validates a supply action
    * @param reserveCache The cached data of the reserve
@@ -176,6 +181,23 @@ library ValidationLogic {
       }
     }
 
+    if (params.isolationModeActive) {
+      // check that the asset being borrowed belongs to the stablecoin category AND
+      // the total exposure is no bigger than the collateral debt ceiling
+      require(
+        params.reserveCache.reserveConfiguration.getEModeCategory() ==
+          DEFAULT_ISOLATION_MODE_BORROW_CATEGORY,
+        Errors.VL_INVALID_ISOLATION_MODE_BORROW_CATEGORY
+      );
+
+      require(
+        reservesData[params.isolationModeCollateralAddress].isolationModeTotalDebt +
+          params.amount <=
+          params.isolationModeDebtCeiling,
+        Errors.VL_DEBT_CEILING_CROSSED
+      );
+    }
+
     if (params.userEModeCategory != 0) {
       require(
         params.reserveCache.reserveConfiguration.getEModeCategory() == params.userEModeCategory,