GP-6905 skip DWARF source file info elements based on addr 0

Some toolchains leave information about dead/removed code in the
sourcefile data.  The sourcefile elements are based off an absolute
address value of '0', which typically is not valid in fully linked
binaries.

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

@@ -743,10 +743,14 @@ public class DIEAggregate {
 		DWARFAttribute lowPc = findAttribute(DW_AT_low_pc);
 		if (lowPc != null && lowPc.getValue() instanceof DWARFNumericAttribute lowPcAttrVal) {
 			try {
-				// TODO: previous code excluded lowPc values that were == 0 as invalid.
 				long rawLowPc = lowPcAttrVal.getUnsignedValue();
 				long lowPcOffset = getDIEContainer().getAddress(lowPc.getAttributeForm(), rawLowPc,
 					getCompilationUnit());
+
+				if (lowPcOffset == 0 && getProgram().isAddr0Tombstone()) {
+					return DWARFRange.EMPTY;
+				}
+
 				long highPcOffset = lowPcOffset;
 
 				DWARFAttribute highPc = findAttribute(DW_AT_high_pc);

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/dwarf/DWARFImportSummary.java

@@ -41,6 +41,7 @@ public class DWARFImportSummary {
 	int paramZeroLenDataType;
 	public int badSourceFileCount;
 	public int numEnumsCreated;
+	public int tombstonedSourceLineEntrySkippedCount;
 
 	Set<Integer> dwarfVers = new HashSet<>();
 	int compUnitCount;

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/dwarf/DWARFProgram.java

@@ -121,6 +121,7 @@ public class DWARFProgram implements Closeable {
 	private DWARFImportSummary importSummary = new DWARFImportSummary();
 	private DWARFSectionProvider sectionProvider;
 	protected long programBaseAddressFixup;
+	protected boolean addr0IsTombstone;
 	private Charset charset;
 
 	private int maxDNICacheSize = 50;
@@ -594,6 +595,9 @@ public class DWARFProgram implements Closeable {
 
 	public void setProgramBaseAddressFixup(long programBaseAddressFixup) {
 		this.programBaseAddressFixup = programBaseAddressFixup;
+		this.addr0IsTombstone = !program.getMemory()
+				.getExecuteSet()
+				.contains(getCodeAddress(0 + programBaseAddressFixup));
 	}
 
 	public AddressRange getAddressRange(DWARFRange range, boolean isCode) {
@@ -622,6 +626,10 @@ public class DWARFProgram implements Closeable {
 		return realZero.equals(addr);
 	}
 
+	public boolean isAddr0Tombstone() {
+		return addr0IsTombstone;
+	}
+
 	public boolean stackGrowsNegative() {
 		return stackGrowsNegative;
 	}

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/dwarf/line/DWARFLine.java

@@ -268,7 +268,7 @@ public class DWARFLine {
 		DWARFLineProgramExecutor lpe = new DWARFLineProgramExecutor(
 			cu.getDIEContainer().getDebugLineReader().clone(opcodes_start), endOffset,
 			cu.getPointerSize(), opcode_base, line_base, line_range, minimum_instruction_length,
-			default_is_stmt);
+			default_is_stmt, cu.getProgram().isAddr0Tombstone());
 
 		return lpe;
 	}
@@ -286,6 +286,12 @@ public class DWARFLine {
 		try (DWARFLineProgramExecutor lpe = getLineProgramExecutor(cu)) {
 			List<SourceFileAddr> results = new ArrayList<>();
 			for (DWARFLineProgramState row : lpe.allRows()) {
+				if (row.tombstone) {
+					// skips elements that were based on tombstoned/dead code that wasn't included
+					// in final binary
+					cu.getProgram().getImportSummary().tombstonedSourceLineEntrySkippedCount++;
+					continue;
+				}
 				try {
 					DWARFFile file = getFile(row.file);
 					results.add(new SourceFileAddr(row.address, file.getPathName(this),

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/dwarf/line/DWARFLineProgramExecutor.java

@@ -40,10 +40,11 @@ public final class DWARFLineProgramExecutor implements Closeable {
 	private final int lineBase;
 	private final int minInstrLen;
 	private final boolean defaultIsStatement;
+	private final boolean addr0IsTombstone;
 
 	public DWARFLineProgramExecutor(BinaryReader reader, long streamEnd, int pointerSize,
 			int opcodeBase, int lineBase, int lineRange, int minInstrLen,
-			boolean defaultIsStatement) {
+			boolean defaultIsStatement, boolean addr0IsTombstone) {
 		this.reader = reader;
 		this.streamEnd = streamEnd;
 		this.pointerSize = pointerSize;
@@ -52,6 +53,7 @@ public final class DWARFLineProgramExecutor implements Closeable {
 		this.lineRange = lineRange;
 		this.minInstrLen = minInstrLen;
 		this.defaultIsStatement = defaultIsStatement;
+		this.addr0IsTombstone = addr0IsTombstone;
 	}
 
 	@Override
@@ -161,6 +163,13 @@ public final class DWARFLineProgramExecutor implements Closeable {
 				break;
 			case DW_LNE_set_address:
 				state.address = reader.readNextUnsignedValue(pointerSize);
+
+				// set tombstone flag when an absolute 0 is set for the address.  (will not catch
+				// relative offsets that evaluate to 0, but that is not a pattern that has been seen)
+				// Following instructions that have relative offset changes to the address value
+				// will inherit this value in each row object that is cloned
+				state.tombstone = addr0IsTombstone && (state.address == 0);
+
 				operands = List.of(state.address);
 				break;
 			case DW_LNE_define_file: {

Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/dwarf/line/DWARFLineProgramState.java

@@ -4,9 +4,9 @@
  * 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.
@@ -63,6 +63,12 @@ public class DWARFLineProgramState {
 
 	public long discriminator;
 
+	/**
+	 * A boolean indicating that the row is based on instructions that are likely attached to a
+	 * dead / tombstoned location.
+	 */
+	public boolean tombstone;
+
 	public DWARFLineProgramState(boolean defaultIsStatement) {
 		this.isStatement = defaultIsStatement;
 	}
@@ -79,6 +85,7 @@ public class DWARFLineProgramState {
 		this.epilogueBegin = other.epilogueBegin;
 		this.isa = other.isa;
 		this.discriminator = other.discriminator;
+		this.tombstone = other.tombstone;
 	}
 
 	public boolean isSameFileLine(DWARFLineProgramState other) {
@@ -88,9 +95,9 @@ public class DWARFLineProgramState {
 	@Override
 	public String toString() {
 		return String.format(
-			"DWARFLineProgramState [address=%s, file=%s, line=%s, column=%s, isStatement=%s, isBasicBlock=%s, isEndSequence=%s, prologueEnd=%s, epilogueBegin=%s, isa=%s, discriminator=%s]",
+			"DWARFLineProgramState [address=%s, file=%s, line=%s, column=%s, isStatement=%s, isBasicBlock=%s, isEndSequence=%s, prologueEnd=%s, epilogueBegin=%s, isa=%s, discriminator=%s, tombstone=%s]",
 			address, file, line, column, isStatement, isBasicBlock, isEndSequence, prologueEnd,
-			epilogueBegin, isa, discriminator);
+			epilogueBegin, isa, discriminator, tombstone);
 	}
 
 }