Add missing 63/64 rule documentation and a test (#462)

- Prominently point out the important differences of the `pallet-revive`
runtime.
- Add a test case illustrating the problem.

See also: https://github.com/paritytech/contract-issues/issues/257

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/integration/contracts/RevertDataOob.sol

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.8.0;
+
+/* runner.json
+{
+    "differential": true,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "RevertDataOob"
+                    }
+                }
+            }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "eb8ac921000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000ffffffff"
+            }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "eb8ac92100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000100000000"
+            }
+        }
+    ]
+}
+*/
+
+contract RevertDataOob {
+    function test(uint256 offset, uint256 len) external {
+        assembly {
+            mstore(0, 0xcc572cf9)
+            mstore(32, offset)
+            mstore(64, len)
+            let stipend := mul(div(gas(), 64), 63) // On EVM this isn't necessary
+            let success := call(stipend, address(), 0, 28, 68, 0, 0)
+            mstore(0, 0xdeadbeef)
+            return(0, 32)
+        }
+    }
+
+    function main(uint256 offset, uint256 len) external pure {
+        assembly {
+            mstore(0x40, 0)
+            revert(offset, len)
+        }
+    }
+}

crates/integration/src/tests.rs

@@ -44,6 +44,7 @@ test_spec!(create, "CreateB", "Create.sol");
 test_spec!(call, "Caller", "Call.sol");
 test_spec!(balance, "Balance", "Balance.sol");
 test_spec!(return_data_oob, "ReturnDataOob", "ReturnDataOob.sol");
+test_spec!(revert_data_oob, "RevertDataOob", "RevertDataOob.sol");
 test_spec!(immutables, "Immutables", "Immutables.sol");
 test_spec!(transaction, "Transaction", "Transaction.sol");
 test_spec!(block_hash, "BlockHash", "BlockHash.sol");