GP-7123: SomLoader parsing improvement

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/som/SomException.java

@@ -0,0 +1,42 @@
+/* ###
+ * 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.app.util.bin.format.som;
+
+/**
+ * An exception class to handle encountering invalid SOM headers
+ */
+public class SomException extends Exception {
+
+	/**
+	 * Constructs a new exception with the specified detail message
+	 * 
+	 * @param message the detail message
+	 */
+	public SomException(String message) {
+		super(message);
+	}
+
+	/**
+	 * Constructs a new exception with the specified cause and a detail message
+	 * 
+	 * @param cause the cause (which is saved for later retrieval by the {@link #getCause()}
+	 *   method (a {@code null} value is permitted, and indicates that the cause is nonexistent
+	 *   or unknown).
+	 */
+	public SomException(Exception cause) {
+		super(cause);
+	}
+}

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/som/SomHeader.java

@@ -84,12 +84,18 @@ public class SomHeader implements StructConverter {
 	 * Creates a new {@link SomHeader}
 	 * 
 	 * @param reader A {@link BinaryReader} positioned at the start of the header
+	 * @throws SomException if the header is invalid
 	 * @throws IOException if there was an IO-related error
 	 */
-	public SomHeader(BinaryReader reader) throws IOException {
+	public SomHeader(BinaryReader reader) throws SomException, IOException {
 		systemId = reader.readNextUnsignedShort();
 		magic = reader.readNextUnsignedShort();
 		versionId = reader.readNextUnsignedInt();
+
+		if (!hasValidMagic() || !hasValidVersionId()) {
+			throw new SomException("Invalid SOM header");
+		}
+
 		fileTime = new SomSysClock(reader);
 		entrySpace = reader.readNextUnsignedInt();
 		entrySubspace = reader.readNextUnsignedInt();
@@ -173,25 +179,6 @@ public class SomHeader implements StructConverter {
 		return magic;
 	}
 
-	/**
-	 * {@return true if this {@link SomHeader} has a valid magic number; otherwise false}
-	 */
-	public boolean hasValidMagic() {
-		return switch (magic) {
-			case MAGIC_LIBRARY:
-			case MAGIC_RELOCATABLE:
-			case MAGIC_NON_SHAREABLE_EXE:
-			case MAGIC_SHAREABLE_EXE:
-			case MAGIC_SHARABLE_DEMAND_LOADABLE_EXE:
-			case MAGIC_DYNAMIC_LOAD_LIBRARY:
-			case MAGIC_SHARED_LIBRARY:
-			case MAGIC_RELOCATABLE_LIBRARY:
-				yield true;
-			default:
-				yield false;
-		};
-	}
-
 	/**
 	 * {@return the version ID}
 	 */
@@ -199,13 +186,6 @@ public class SomHeader implements StructConverter {
 		return versionId;
 	}
 
-	/**
-	 * {@return true if this {@link SomHeader} has a valid version ID; otherwise false}
-	 */
-	public boolean hasValidVersionId() {
-		return versionId == 85082112 || versionId == 87102412;
-	}
-
 	/**
 	 * {@return the file time}
 	 */
@@ -558,6 +538,32 @@ public class SomHeader implements StructConverter {
 		}
 	}
 
+	/**
+	 * {@return true if this {@link SomHeader} has a valid magic number; otherwise false}
+	 */
+	private boolean hasValidMagic() {
+		return switch (magic) {
+			case MAGIC_LIBRARY:
+			case MAGIC_RELOCATABLE:
+			case MAGIC_NON_SHAREABLE_EXE:
+			case MAGIC_SHAREABLE_EXE:
+			case MAGIC_SHARABLE_DEMAND_LOADABLE_EXE:
+			case MAGIC_DYNAMIC_LOAD_LIBRARY:
+			case MAGIC_SHARED_LIBRARY:
+			case MAGIC_RELOCATABLE_LIBRARY:
+				yield true;
+			default:
+				yield false;
+		};
+	}
+
+	/**
+	 * {@return true if this {@link SomHeader} has a valid version ID; otherwise false}
+	 */
+	private boolean hasValidVersionId() {
+		return versionId == 85082112 || versionId == 87102412;
+	}
+
 	@Override
 	public DataType toDataType() throws DuplicateNameException, IOException {
 		StructureDataType struct = new StructureDataType("header", SIZE);

Ghidra/Features/Base/src/main/java/ghidra/app/util/opinion/SomLoader.java

@@ -50,18 +50,16 @@ public class SomLoader extends AbstractProgramWrapperLoader {
 
 		try {
 			SomHeader header = new SomHeader(new BinaryReader(provider, false));
-			if (header.hasValidMagic() && header.hasValidVersionId()) {
+			List<QueryResult> results = QueryOpinionService.query(getName(),
-				List<QueryResult> results = QueryOpinionService.query(getName(),
+				Integer.toString(header.getSystemId()), null);
-					Integer.toString(header.getSystemId()), null);
+			for (QueryResult result : results) {
-				for (QueryResult result : results) {
+				loadSpecs.add(new LoadSpec(this, 0, result));
-					loadSpecs.add(new LoadSpec(this, 0, result));
+			}
-				}
+			if (loadSpecs.isEmpty()) {
-				if (loadSpecs.isEmpty()) {
+				loadSpecs.add(new LoadSpec(this, 0, true));
-					loadSpecs.add(new LoadSpec(this, 0, true));
-				}
 			}
 		}
-		catch (IOException e) {
+		catch (SomException | IOException e) {
 			// that's ok, not a System Object Model
 		}
 		return loadSpecs;