Track state of read-only mode in stakingProxy

contracts/staking/contracts/src/StakingProxy.sol

@@ -20,6 +20,7 @@ pragma solidity ^0.5.9;
 pragma experimental ABIEncoderV2;
 
 import "./libs/LibProxy.sol";
+import "./libs/LibSafeDowncast.sol";
 import "./immutable/MixinStorage.sol";
 import "./interfaces/IStorageInit.sol";
 import "./interfaces/IStakingProxy.sol";
@@ -30,6 +31,7 @@ contract StakingProxy is
     MixinStorage
 {
     using LibProxy for address;
+    using LibSafeDowncast for uint256;
 
     /// @dev Constructor.
     /// @param _stakingContract Staking contract to delegate calls to.
@@ -86,16 +88,25 @@ contract StakingProxy is
     }
 
     /// @dev Set read-only mode (state cannot be changed).
-    function setReadOnlyMode(bool readOnlyMode)
+    function setReadOnlyMode(bool shouldSetReadOnlyMode)
         external
         onlyAuthorized
     {
-        if (readOnlyMode) {
+        uint96 timestamp = block.timestamp.downcastToUint96();
+        if (shouldSetReadOnlyMode) {
             stakingContract = readOnlyProxy;
+            readOnlyState = IStructs.ReadOnlyState({
+                isReadOnlyModeSet: true,
+                lastSetTimestamp: timestamp
+            });
         } else {
             stakingContract = readOnlyProxyCallee;
+            readOnlyState.isReadOnlyModeSet = false;
         }
-        emit ReadOnlyModeSet(readOnlyMode);
+        emit ReadOnlyModeSet(
+            shouldSetReadOnlyMode,
+            timestamp
+        );
     }
 
     /// @dev Batch executes a series of calls to the staking contract.
@@ -108,9 +119,9 @@ contract StakingProxy is
         // Initialize commonly used variables.
         bool success;
         bytes memory returnData;
-        batchReturnData = new bytes[](data.length);
-        address staking = stakingContract;
         uint256 dataLength = data.length;
+        batchReturnData = new bytes[](dataLength);
+        address staking = stakingContract;
 
         // Ensure that a staking contract has been attached to the proxy.
         if (staking == address(0)) {

contracts/staking/contracts/src/ZrxVault.sol

@@ -105,6 +105,7 @@ contract ZrxVault is
     function enterCatastrophicFailure()
         external
         onlyAuthorized
+        onlyNotInCatastrophicFailure
     {
         isInCatastrophicFailure = true;
         emit InCatastrophicFailureMode(msg.sender);

contracts/staking/contracts/src/immutable/MixinStorage.sol

@@ -41,7 +41,10 @@ contract MixinStorage is
     // address for read-only proxy to call
     address public readOnlyProxyCallee;
 
-    // mapping from StakeStatus to gloabl stored balance
+    // state of read-only mode in stakingProxy
+    IStructs.ReadOnlyState public readOnlyState;
+
+    // mapping from StakeStatus to global stored balance
     // (access using _loadSyncedBalance or _loadUnsyncedBalance)
     // NOTE: only Status.DELEGATED is used to access this mapping, but this format
     // is used for extensibility

contracts/staking/contracts/src/interfaces/IStakingProxy.sol

@@ -17,9 +17,12 @@
 */
 
 pragma solidity ^0.5.9;
+pragma experimental ABIEncoderV2;
+
+import "./IStructs.sol";
 
 
-interface IStakingProxy /* is IStaking */
+contract IStakingProxy /* is IStaking */
 {
 
     /// @dev Emitted by StakingProxy when a staking contract is attached.
@@ -33,7 +36,8 @@ interface IStakingProxy /* is IStaking */
 
     /// @dev Emitted by StakingProxy when read-only mode is set.
     event ReadOnlyModeSet(
-        bool readOnlyMode
+        bool readOnlyMode,
+        uint96 timestamp
     );
 
     /// @dev Delegates calls to the staking contract, if it is set.
@@ -52,4 +56,10 @@ interface IStakingProxy /* is IStaking */
     /// Note that this is callable only by an authorized address.
     function detachStakingContract()
         external;
+
+    /// @dev Gets state of stakingProxy read-only mode.
+    function readOnlyState()
+        external
+        view
+        returns (IStructs.ReadOnlyState memory);
 }

contracts/staking/contracts/src/interfaces/IStructs.sol

@@ -21,6 +21,14 @@ pragma solidity ^0.5.9;
 
 interface IStructs {
 
+    /// @dev State of stakingProxy read-only mode.
+    /// @param isReadOnlyModeSet True if in read-only mode.
+    /// @param lastSetTimestamp Timestamp at which read-only mode was last set.
+    struct ReadOnlyState {
+        bool isReadOnlyModeSet;
+        uint96 lastSetTimestamp;
+    }
+
     /// @dev Status for a pool that actively traded during the current epoch.
     /// (see MixinExchangeFees).
     /// @param feesCollected Fees collected in ETH by this pool.

contracts/staking/contracts/test/TestStorageLayoutAndConstants.sol

@@ -118,6 +118,14 @@ contract TestStorageLayoutAndConstants is
             )
             slot := add(slot, 0x1)
 
+            assertSlotAndOffset(
+                readOnlyState_slot,
+                readOnlyState_offset,
+                slot,
+                offset
+            )
+            slot := add(slot, 0x1)
+
             assertSlotAndOffset(
                 _globalStakeByStatus_slot,
                 _globalStakeByStatus_offset,