Roughed in ProtectedAddressSpace class

Ghidra/Framework/SoftwareModeling/data/languages/processor_spec.rxg

@@ -43,6 +43,9 @@
         <optional>
           <element name="segmented_address">
             <attribute name="space"/>
+            <optional>
+              <attribute name="type"/>
+            </optional>
           </element>
         </optional>
 

Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/processors/sleigh/SleighLanguage.java

@@ -79,6 +79,7 @@ public class SleighLanguage implements Language {
 	 * Non-null if a space should yes segmented addressing
 	 */
 	String segmentedspace = "";
+	String segmentType = "";
 	AddressSet volatileAddresses;
 	private ContextCache contextcache = null;
 	/**
@@ -508,6 +509,10 @@ public class SleighLanguage implements Language {
 		if (nextElement != null) {
 			XmlElement element = parser.start(); // segmented_address element
 			segmentedspace = element.getAttribute("space");
+			segmentType = element.getAttribute("type");
+			if (segmentType == null) {
+				segmentType = "";
+			}
 		}
 		parser.dispose();
 	}
@@ -896,8 +901,13 @@ public class SleighLanguage implements Language {
 					throw new SleighException(
 						"Segmented space does not support truncation: " + name);
 				}
+				if (segmentType.equals("protected")) {
+					spc = new ProtectedAddressSpace(name, index);
+				}
+				else {
 					spc = new SegmentedAddressSpace(name, index);
 				}
+			}
 			else {
 				if (truncateSpace) {
 					int truncatedSize = description.getTruncatedSpaceSize(name);

Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/address/ProtectedAddressSpace.java

@@ -0,0 +1,67 @@
+/* ###
+ * IP: GHIDRA
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package ghidra.program.model.address;
+
+/**
+ * Address Space for (intel) 16-bit protected mode programs. This space produces
+ * SegmentedAddress objects whose underlying (flat) offset encodes both the
+ * segment and the segment offset without losing information. There is no possibility
+ * of alternate encodings for a single address as with real-mode.
+ */
+public class ProtectedAddressSpace extends SegmentedAddressSpace {
+
+	private final static int PROTECTEDMODE_SIZE = 32;
+	private final static int PROTECTEDMODE_OFFSETSIZE = 16;
+
+	private int offsetSize;		// Number of bits in the segment offset
+	private long offsetMask;	// Mask for retrieving the segment offset
+
+	public ProtectedAddressSpace(String name, int unique) {
+		super(name, PROTECTEDMODE_SIZE, unique);
+		offsetSize = PROTECTEDMODE_OFFSETSIZE;
+		offsetMask = 1;
+		offsetMask <<= offsetSize;
+		offsetMask -= 1;
+	}
+
+	@Override
+	protected long getFlatOffset(int segment, long offset) {
+		long res = segment;
+		res <<= offsetSize;
+		res += offset;
+		return res;
+	}
+
+	@Override
+	protected int getDefaultSegmentFromFlat(long flat) {
+		return (int) (flat >>> offsetSize);
+	}
+
+	@Override
+	protected long getDefaultOffsetFromFlat(long flat) {
+		return (flat & offsetMask);
+	}
+
+	@Override
+	protected long getOffsetFromFlat(long flat, int segment) {
+		return (flat & offsetMask);		// segment does not affect the offset
+	}
+
+	@Override
+	protected SegmentedAddress getAddressInSegment(long flat, int preferredSegment) {
+		return null;	// The segment cannot be changed as the flat explicitly encodes it
+	}
+}

Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/address/SegmentedAddress.java

@@ -17,11 +17,15 @@ package ghidra.program.model.address;
 
 
 /**
- * Address class for dealing with intel 20 bit segmented addresses.
+ * Address class for dealing with (intel) segmented addresses.  The class itself is agnostic
+ * about the mapping from segmented encoding to flat address offset, it uses the
+ * SegmentedAddressSpace to perform this mapping. So the same class can be used to represent
+ * either a real-mode address or a protected-mode address.  The class uses the underlying
+ * offset field to hold the flat encoding.
  */
 public class SegmentedAddress extends GenericAddress {
 
-	private final int segment;
+	private final int segment;		// The specific segment value associated with this address
 
 	/**
 	 * Constructor for SegmentedAddress.

Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/address/SegmentedAddressSpace.java

@@ -20,20 +20,46 @@ import org.apache.commons.lang3.StringUtils;
 import ghidra.util.NumericUtilities;
 
 /**
- * Address Space for dealing with Intel 20 bit segmented addresses.
+ * Address Space for dealing with (intel) segmented address spaces.
+ * It understands the mapping between the segmented encoding (seg:offset) and
+ * the flat address encoding necessary to produce an Address object that can be
+ * used by other analyses.  This mapping is inherent in protected methods:
+ *   - getDefaultOffsetFromFlat
+ *   - getDefaultSegmentFromFlat
+ *   - getFlatOffset
+ *   - getOffsetFromFlat
+ *   - getAddressInSegment
+ * 
+ * These 5 methods can be overridden to get a different mapping. This base class is
+ * set up to map as for x86 16-bit real-mode.
  */
 public class SegmentedAddressSpace extends GenericAddressSpace {
 
-	private final static int SIZE = 21;
+	private final static int REALMODE_SIZE = 21;
+	private final static long REALMODE_MAXOFFSET = 0x10FFEF;
 
 	/**
-	 * Constructs a new Segmented AddressSpace.
+	 * Constructor for larger size address spaces (than the real-mode space)
+	 * @param name is the name of the space
+	 * @param size is the number of bits in a (flat) address
+	 * @param unique is the unique id for the space
+	 */
+	protected SegmentedAddressSpace(String name, int size, int unique) {
+		super(name, size, TYPE_RAM, unique);
+		spaceSize = 1;
+		spaceSize <<= size;
+		maxOffset = spaceSize - 1;
+		maxAddress = getUncheckedAddress(maxOffset);
+	}
+
+	/**
+	 * Constructs a new Segmented AddressSpace for x86 real-mode, with 21-bit addresses.
 	 * @param name is the name of the space
 	 * @param unique is the unique id for the space.
 	 */
 	public SegmentedAddressSpace(String name, int unique) {
-		super(name, SIZE, TYPE_RAM, unique);
+		super(name, REALMODE_SIZE, TYPE_RAM, unique);
-		maxOffset = 0x10FFEF;
+		maxOffset = REALMODE_MAXOFFSET;
 		spaceSize = maxOffset + 1;
 		maxAddress = getUncheckedAddress(maxOffset);
 	}