GT-2884_GT-3583 fix for patterns and function signatures starting at 0x0

address, also after=function in function start patterns

Ghidra/Features/Base/src/main/java/ghidra/app/cmd/function/ApplyFunctionDataTypesCmd.java

@@ -21,8 +21,7 @@ import ghidra.app.cmd.disassemble.DisassembleCommand;
 import ghidra.app.util.PseudoDisassembler;
 import ghidra.framework.cmd.BackgroundCommand;
 import ghidra.framework.model.DomainObject;
-import ghidra.program.model.address.Address;
-import ghidra.program.model.address.AddressSetView;
+import ghidra.program.model.address.*;
 import ghidra.program.model.data.*;
 import ghidra.program.model.listing.*;
 import ghidra.program.model.mem.MemoryBlock;
@@ -266,12 +265,15 @@ public class ApplyFunctionDataTypesCmd extends BackgroundCommand {
 	boolean isValidFunctionStart(TaskMonitor monitor, Address address) {
 		// instruction above falls into this one
 		//   could be non-returning function, but we can't tell now
-		Instruction instructionBefore =
-			program.getListing().getInstructionContaining(address.subtract(1));
-		if (instructionBefore != null && address.equals(instructionBefore.getFallThrough())) {
-			return false;
+		Address addrBefore = address.previous();
+		if (addrBefore != null) {
+			Instruction instrBefore;
+			instrBefore = program.getListing().getInstructionContaining(addrBefore);
+			if (instrBefore != null && address.equals(instrBefore.getFallThrough())) {
+				return false;
+			}
 		}
-
+		
 		// check if part of a larger code-block
 		ReferenceIterator referencesTo = program.getReferenceManager().getReferencesTo(address);
 		for (Reference reference : referencesTo) {

Ghidra/Features/Base/src/main/java/ghidra/app/plugin/exceptionhandlers/gcc/structures/ehFrame/FrameDescriptionEntry.java

@@ -304,7 +304,13 @@ public class FrameDescriptionEntry extends GccAnalysisClass {
 		String comment = "(FDE) PcRange";
 
 		intPcRange = (int) GccAnalysisUtils.readDWord(program, addr);
+		if (intPcRange < 0) {
+			return null;
+		}
 
+		if (intPcRange == 0) {
+			intPcRange = 1;
+		}
 		pcEndAddr = pcBeginAddr.add(intPcRange - 1);
 
 		DataType dataType = getAddressSizeDataType();

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/dwarf4/DIEAggregate.java

@@ -871,9 +871,14 @@ public class DIEAggregate {
 			// else it was a DW_FORM_data value and is relative to the lowPC value
 			DWARFNumericAttribute low =
 				getAttribute(DWARFAttribute.DW_AT_low_pc, DWARFNumericAttribute.class);
-			if (low != null && highVal.getUnsignedValue() > 0) {
+			
+			long lhighVal = highVal.getUnsignedValue();
+			if (lhighVal == 0) {
+				lhighVal = 1;
+			}
+			if (low != null && lhighVal > 0) {
 				return low.getUnsignedValue() + getProgram().getProgramBaseAddressFixup() +
-					highVal.getUnsignedValue() - 1;
+						lhighVal - 1;
 			}
 		}
 		throw new IOException("Bad/unsupported DW_AT_high_pc attribute value or type");

Ghidra/Features/BytePatterns/src/main/java/ghidra/app/analyzers/FunctionStartAnalyzer.java

@@ -368,6 +368,9 @@ public class FunctionStartAnalyzer extends AbstractAnalyzer implements PatternFa
 					if (checkAlreadyInFunctionAbove(program, addr)) {
 						return false;
 					}
+					if (!checkForFunctionAbove(program, addr)) {
+						return false;
+					}
 				}
 				else if (name.startsWith("inst")) {
 					// make sure there is an end of function at location to check
@@ -402,10 +405,35 @@ public class FunctionStartAnalyzer extends AbstractAnalyzer implements PatternFa
 			return true;
 		}
 
+		/**
+		 * Check for an existing function above the addr.  Addr should not be in the function.
+		 * @param program prpgram to check in
+		 * @param addr address to check
+		 * @return true if there is an existing function above addr that doesn't contain addr
+		 */
+		private boolean checkForFunctionAbove(Program program, Address addr) {
+			// make sure there is an end of function before this one, and addr is not in the function
+			Function func = null;
+			Address addrBefore = addr.previous();
+			func = program.getFunctionManager().getFunctionContaining(addrBefore);
+			// no function above
+			if (func == null) {
+				return false;
+			}
+			// addr is in function above
+			if (func.getBody().contains(addr)) {
+				return false;
+			}
+			return true;
+		}
+		
 		private boolean checkAlreadyInFunctionAbove(Program program, Address addr) {
 			// make sure there is an end of function before this one, and if just an instruction, doesn't fall into this one.
 			Function func = null;
 			Address addrBefore = addr.previous();
+			if (addrBefore == null) {
+				return false;
+			}
 			func = program.getFunctionManager().getFunctionContaining(addrBefore);
 			if (func == null) {
 				Instruction instr = program.getListing().getInstructionContaining(addrBefore);