Improve checks for invalid values

We determine address_masks using log/ln2, which cannot accept 0.
Therefore we don't support address spaces with a maximum_address of 0.
This can affect registry hives, so we've added a check in registry hives
to prevent creating layers with invalid maximum_addresses.

volatility/framework/exceptions.py

@@ -52,3 +52,7 @@ class SymbolSpaceError(VolatilityException):
 
 class LayerException(VolatilityException):
     """Thrown when an error occurs dealing with memory and layers"""
+
+
+class StructureException(VolatilityException):
+    """Thrown when an error occurs dealing with an expected structure type"""

volatility/framework/layers/registry.py

@@ -46,7 +46,9 @@ class RegistryHive(interfaces.layers.TranslationLayerInterface):
         self._minaddr = 0
         self._maxaddr = self._base_block.Length
 
-        # print("MAPPING", self.mapping(self._base_block.RootCell, length = 2))
+        if self._base_block.Length <= 0:
+            raise exceptions.StructureException(
+                "Invalid registry base_block length: {}".format(self._base_block.Length))
 
     @property
     def address_mask(self):