Merge remote-tracking branch 'origin/GP-4145_dev747368_external_symbol_resolver--SQUASHED'

Author: ryanmkurtz

Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/analysis/ExternalSymbolResolverAnalyzer.java

@@ -15,21 +15,16 @@
  */
 package ghidra.app.plugin.core.analysis;
 
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.List;
-
 import ghidra.app.services.*;
 import ghidra.app.util.importer.MessageLog;
-import ghidra.app.util.opinion.*;
-import ghidra.framework.model.*;
+import ghidra.app.util.opinion.ElfLoader;
+import ghidra.app.util.opinion.MachoLoader;
 import ghidra.framework.options.Options;
 import ghidra.program.model.address.AddressSetView;
-import ghidra.program.model.listing.Library;
 import ghidra.program.model.listing.Program;
 import ghidra.program.util.ExternalSymbolResolver;
+import ghidra.util.Msg;
 import ghidra.util.exception.CancelledException;
-import ghidra.util.exception.VersionException;
 import ghidra.util.task.TaskMonitor;
 
 /**
@@ -61,7 +56,7 @@ public boolean canAnalyze(Program program) {
 		if (program.getDomainFile().getParent() == null) {
 			return false;
 		}
-		
+
 		Options options = program.getOptions(Program.PROGRAM_INFO);
 		String format = options.getString("Executable Format", null);
 		return ElfLoader.ELF_NAME.equals(format) || MachoLoader.MACH_O_NAME.equals(format);
@@ -71,65 +66,16 @@ public boolean canAnalyze(Program program) {
 	public boolean added(Program program, AddressSetView set, TaskMonitor monitor, MessageLog log)
 			throws CancelledException {
 
-		Object consumer = new Object();
-		log = new MessageLog(); // For now, we don't want the analysis log spammed
-		ProjectData projectData = program.getDomainFile().getParent().getProjectData();
-		List<Loaded<Program>> loadedPrograms = new ArrayList<>();
-
-		// Add program to list
-		loadedPrograms.add(new Loaded<>(program, program.getName(),
-			program.getDomainFile().getParent().getPathname()));
-
-		// Add external libraries to list
-		for (Library extLibrary : ExternalSymbolResolver.getLibrarySearchList(program)) {
-			monitor.checkCancelled();
-			String libPath = extLibrary.getAssociatedProgramPath();
-			if (libPath == null) {
-				continue;
-			}
-
-			DomainFile libDomainFile = projectData.getFile(libPath);
-			if (libDomainFile == null) {
-				log.appendMsg("Referenced external program not found: " + libPath);
-				continue;
-			}
-
-			try {
-				DomainObject libDomainObject =
-					libDomainFile.getDomainObject(consumer, false, false, monitor);
-				if (libDomainObject instanceof Program p) {
-					loadedPrograms.add(new Loaded<>(p, libDomainFile.getName(),
-						libDomainFile.getParent().getPathname()));
-				}
-				else {
-					libDomainObject.release(consumer);
-					log.appendMsg("Referenced external program is not a program: " + libPath);
-				}
+		try (ExternalSymbolResolver esr = new ExternalSymbolResolver(
+			program.getDomainFile().getParent().getProjectData(), monitor)) {
+			esr.addProgramToFixup(program);
+			esr.fixUnresolvedExternalSymbols();
+			esr.logInfo(s -> Msg.info(this, s), false);
+			if (esr.hasProblemLibraries()) {
+				// causes a popup message at end of analysis session
+				esr.logInfo(log::appendMsg, true);
 			}
-			catch (IOException e) {
-				log.appendMsg("Failed to open library dependency project file: " +
-					libDomainFile.getPathname());
-			}
-			catch (VersionException e) {
-				log.appendMsg(
-					"Referenced external program requires updgrade, unable to consider symbols: " +
-						libPath);
-			}
-		}
-
-		// Resolve symbols
-		try {
-			ExternalSymbolResolver.fixUnresolvedExternalSymbols(loadedPrograms, false, log,
-				monitor);
 			return true;
 		}
-		catch (IOException e) {
-			return false;
-		}
-		finally {
-			for (int i = 1; i < loadedPrograms.size(); i++) {
-				loadedPrograms.get(i).release(consumer);
-			}
-		}
 	}
 }

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

@@ -158,8 +158,16 @@ protected void postLoadProgramFixups(List<Loaded<Program>> loadedPrograms, Proje
 			throws CancelledException, IOException {
 		super.postLoadProgramFixups(loadedPrograms, project, options, messageLog, monitor);
 
-		ExternalSymbolResolver.fixUnresolvedExternalSymbols(loadedPrograms, true, messageLog,
-			monitor);
+		try (ExternalSymbolResolver esr =
+			new ExternalSymbolResolver(project.getProjectData(), monitor)) {
+			for (Loaded<Program> loadedProgram : loadedPrograms) {
+				esr.addProgramToFixup(
+					loadedProgram.getProjectFolderPath() + loadedProgram.getName(),
+					loadedProgram.getDomainObject());
+			}
+			esr.fixUnresolvedExternalSymbols();
+			esr.logInfo(messageLog::appendMsg, true);
+		}
 	}
 
 	@Override

Ghidra/Features/Base/src/main/java/ghidra/program/util/ExternalSymbolResolver.java

@@ -15,13 +15,13 @@
  */
 package ghidra.program.util;
 
+import java.io.Closeable;
 import java.io.IOException;
 import java.util.*;
-import java.util.stream.Collectors;
+import java.util.function.Consumer;
 
 import db.Transaction;
-import ghidra.app.util.importer.MessageLog;
-import ghidra.app.util.opinion.Loaded;
+import ghidra.framework.model.*;
 import ghidra.framework.options.Options;
 import ghidra.program.model.listing.*;
 import ghidra.program.model.symbol.*;
@@ -30,8 +30,15 @@
 import ghidra.util.exception.*;
 import ghidra.util.task.TaskMonitor;
 
-public class ExternalSymbolResolver {
-
+/**
+ * Moves dangling external function symbols found in the {@link Library#UNKNOWN EXTERNAL/UNKNOWN}
+ * namespace into the namespace of the external library that publishes a matching symbol.
+ * <p>
+ * This uses an ordered list of external library names that was attached to the program during
+ * import by the Elf or Macho loader (see {@link #REQUIRED_LIBRARY_PROPERTY_PREFIX}).
+ * 
+ */
+public class ExternalSymbolResolver implements Closeable {
 	private final static String REQUIRED_LIBRARY_PROPERTY_PREFIX = "Required Library [";
 
 	/**
@@ -45,189 +52,420 @@ public static String getRequiredLibraryProperty(int libraryIndex) {
 			StringUtilities.pad("" + libraryIndex, ' ', 4));
 	}
 
+	private final ProjectData projectData;
+	private final TaskMonitor monitor;
+	private final List<ProgramSymbolResolver> programsToFix = new ArrayList<>();
+	private final Map<String, Program> loadedPrograms = new HashMap<>();
+	private final Map<String, Throwable> problemLibraries = new HashMap<>();
+
+	public ExternalSymbolResolver(ProjectData projectData, TaskMonitor monitor) {
+		this.projectData = projectData;
+		this.monitor = monitor;
+	}
+
+	/**
+	 * Queues a program into this session that will be fixed when {@link #fixUnresolvedExternalSymbols()}
+	 * is called.
+	 * <p>
+	 * The program should be fully persisted to the project if using this method, otherwise use
+	 * {@link #addProgramToFixup(String, Program)} and specify the pathname the program will 
+	 * be saved to.
+	 *  
+	 * @param program {@link Program} to fix
+	 */
+	public void addProgramToFixup(Program program) {
+		addProgramToFixup(program.getDomainFile().getPathname(), program);
+	}
+
+	/**
+	 * Queues a program into this session that will be fixed when {@link #fixUnresolvedExternalSymbols()}
+	 * is called.
+	 *  
+	 * @param programPath string project path to the program
+	 * @param program {@link Program} to fix
+	 */
+	public void addProgramToFixup(String programPath, Program program) {
+		programsToFix.add(new ProgramSymbolResolver(program, programPath));
+		addLoadedProgram(programPath, program);
+	}
+
+	/**
+	 * Adds an already opened program to this session, allowing it to be used as an external
+	 * library without needing to look it up in the current project.
+	 * 
+	 * @param programPath project path to already opened program
+	 * @param program {@link Program}
+	 */
+	public void addLoadedProgram(String programPath, Program program) {
+		if (loadedPrograms.put(programPath, program) == null) {
+			program.addConsumer(this);
+		}
+	}
+
+	/**
+	 * Returns true if there was an error encountered when trying to open an external library.
+	 * 
+	 * @return boolean flag, true if there was a problem opening an external library
+	 */
+	public boolean hasProblemLibraries() {
+		return !problemLibraries.isEmpty();
+	}
+
+	@Override
+	public void close() {
+		for (Program prog : loadedPrograms.values()) {
+			prog.release(this);
+		}
+		programsToFix.clear();
+		loadedPrograms.clear();
+	}
+
+	/**
+	 * Resolves any unresolved external symbols in each program that has been queued up via
+	 * {@link #addProgramToFixup(String, Program)}.
+	 * 
+	 * @throws CancelledException if cancelled
+	 */
+	public void fixUnresolvedExternalSymbols() throws CancelledException {
+		for (ProgramSymbolResolver psr : programsToFix) {
+			psr.resolveExternalSymbols();
+		}
+	}
+
 	/**
-	 * Links unresolved symbols to the first symbol found in the (ordered) linked
-	 * libraries (saved in the program's properties as {@value #REQUIRED_LIBRARY_PROPERTY_PREFIX}).
+	 * Logs information about the libraries and symbols that were found during the fixup.
+	 * 
+	 * @param logger consumer that will log a string
+	 * @param shortSummary boolean flag, if true individual symbol names will be omitted
+	 */
+	public void logInfo(Consumer<String> logger, boolean shortSummary) {
+		for (ProgramSymbolResolver psr : programsToFix) {
+			psr.log(logger, shortSummary);
+		}
+	}
+
+	/**
+	 * Fetches a program from a cache of Program instances.  If the requested program
+	 * isn't currently in the cache, it will be opened (if possible).
 	 * <p>
-	 * The ordering and precedence logic is loader specific though no particular binary formats
-	 * are parsed or required.
+	 * This cache of programs are pinned by registering a consumer on the program, and will be
+	 * released during {@link #close()} of this ExternalSymbolServer instance.
 	 * <p>
-	 * The program's external libraries need to already be populated with paths to
-	 * already existing / imported libraries.
-	 *
-	 * @param loadedPrograms The {@link Loaded} {@link Program}s to fix.  The first entry is the
-	 *   "primary" {@link Loaded} {@link Program}.
-	 * @param fixAll True if all of the {@link Loaded} {@link Program}s should be fixed;
-	 *   false if just the "primary" {@link Loaded} {@link Program} should be fixed.
-	 * @param messageLog {@link MessageLog} to write info message to.
-	 * @param monitor {@link TaskMonitor} to watch for cancel and update with progress.
-	 * @throws CancelledException if user cancels
-	 * @throws IOException if error reading
+	 * This cache is shared between all ProgramSymbolResolver instances (that were created
+	 * by calling {@link #addProgramToFixup(String, Program)}).
+	 * 
+	 * @param libPath project path to a library program
+	 * @return {@link Program}, or null if not found or other error during opening
+	 * @throws CancelledException if cancelled
 	 */
-	public static void fixUnresolvedExternalSymbols(List<Loaded<Program>> loadedPrograms,
-			boolean fixAll, MessageLog messageLog, TaskMonitor monitor)
-			throws CancelledException, IOException {
-		Map<String, Loaded<Program>> loadedByPath = loadedPrograms.stream()
-				.collect(Collectors.toMap(
-					loaded -> loaded.getProjectFolderPath() + loaded.getName(), loaded -> loaded));
+	protected Program getLibraryProgram(String libPath) throws CancelledException {
+		Program result = loadedPrograms.get(libPath);
+		if (result == null && !problemLibraries.containsKey(libPath)) {
+			result = openLibraryFile(projectData.getFile(libPath), libPath);
+
+			if (result != null) {
+				loadedPrograms.put(libPath, result);
+			}
+		}
+		return result;
+	}
 
-		List<Loaded<Program>> fixupList =
-			loadedPrograms.subList(0, fixAll ? loadedPrograms.size() : 1);
+	/**
+	 * Opens a library binary.
+	 * 
+	 * @param libDf optional, reference to a the DomainFile that was found in a project.  If null
+	 * (meaning a lookup in the project failed to find a matching file), libPath will be used when
+	 * creating error strings that reference the problematic file
+	 * @param libPath project path for the DomainFile
+	 * @return a opened {@link Program}
+	 * @throws CancelledException if cancelled
+	 */
+	protected Program openLibraryFile(DomainFile libDf, String libPath) throws CancelledException {
+		try {
+			if (libDf == null) {
+				throw new IOException("Dangling external path: " + libPath);
+			}
+			DomainObject libDo = libDf.getDomainObject(this, false, false, monitor);
+			if (libDo instanceof Program p) {
+				return p;
+			}
+			libDo.release(this);
+			throw new IOException("Referenced external program is not a program: " + libPath);
+		}
+		catch (IOException | VersionException e) {
+			problemLibraries.put(libPath, e);
+		}
+		return null;
+	}
 
-		monitor.initialize(fixupList.size());
-		for (Loaded<Program> loadedProgram : fixupList) {
-			Program program = loadedProgram.getDomainObject();
+	/**
+	 * Represents a program that needs its external symbols to be fixed.
+	 */
+	private class ProgramSymbolResolver {
+		record ExtLibInfo(String name, Library lib, String programPath, Program program,
+				List<String> resolvedSymbols, Throwable problem) {
+			String getProblemMessage() {
+				if (problem instanceof VersionException ve) {
+					return getVersionError(ve);
+				}
+				return problem != null ? problem.getMessage() : "";
+			}
 
-			Collection<Long> unresolvedExternalFunctionIds =
-				getUnresolvedExternalFunctionIds(program);
-			if (unresolvedExternalFunctionIds.size() == 0) {
-				continue;
+			String getLibPath() {
+				return programPath != null ? programPath : "missing";
 			}
 
-			List<Library> libSearchList = getLibrarySearchList(program);
-			if (libSearchList.isEmpty()) {
-				continue;
+			String getVersionError(VersionException ve) {
+				String versionType = switch (ve.getVersionIndicator()) {
+					case VersionException.NEWER_VERSION -> " newer";
+					case VersionException.OLDER_VERSION -> "n older";
+					default -> "n unknown";
+				};
+
+				String upgradeMsg = ve.isUpgradable() ? " (upgrade is possible)" : "";
+
+				return "skipped: file was created with a%s version of Ghidra%s"
+						.formatted(versionType, upgradeMsg);
 			}
 
-			try (Transaction tx = program.openTransaction("Resolve External Symbols")) {
+		}
+
+		Program program;
+		String programPath;
+		int externalSymbolCount;
+		List<Long> unresolvedExternalFunctionIds;
+		List<ExtLibInfo> extLibs = new ArrayList<>();
+
+		private ProgramSymbolResolver(Program program, String programPath) {
+			this.program = program;
+			this.programPath = programPath;
+		}
 
-				messageLog.appendMsg("----- [" + program.getName() + "] Resolve " +
-					unresolvedExternalFunctionIds.size() + " external symbols -----");
+		private int getResolvedSymbolCount() {
+			return externalSymbolCount - unresolvedExternalFunctionIds.size();
+		}
 
-				for (Library extLibrary : libSearchList) {
-					monitor.checkCancelled();
-					String libName = extLibrary.getName();
-					String libPath = extLibrary.getAssociatedProgramPath();
-					if (libPath == null) {
-						continue;
+		private void log(Consumer<String> logger, boolean shortSummary) {
+			boolean changed = unresolvedExternalFunctionIds.size() != externalSymbolCount;
+			if (extLibs.isEmpty() && externalSymbolCount == 0) {
+				return;
+			}
+			else if (!changed && !hasSomeLibrariesConfigured()) {
+				logger.accept(
+					"Resolving External Symbols of [%s] - %d unresolved symbols, no external libraries configured - skipping"
+							.formatted(programPath, externalSymbolCount));
+				return;
+			}
+
+			logger.accept("Resolving External Symbols of [%s]%s".formatted(programPath,
+				shortSummary ? " - Summary" : ""));
+			logger.accept("\t%d external symbols resolved, %d remain unresolved"
+					.formatted(getResolvedSymbolCount(), unresolvedExternalFunctionIds.size()));
+			for (ExtLibInfo extLib : extLibs) {
+				if (extLib.problem != null) {
+					logger.accept("\t[%s] -> %s, %s".formatted(extLib.name, extLib.getLibPath(),
+						extLib.getProblemMessage()));
+				}
+				else if (extLib.programPath != null) {
+					logger.accept("\t[%s] -> %s, %d new symbols resolved".formatted(extLib.name,
+						extLib.getLibPath(), extLib.resolvedSymbols.size()));
+				}
+				else {
+					logger.accept("\t[%s] -> %s".formatted(extLib.name, extLib.getLibPath()));
+				}
+				if (!shortSummary) {
+					for (String symbolName : extLib.resolvedSymbols) {
+						logger.accept("\t\t[%s]".formatted(symbolName));
 					}
-					
-					Loaded<Program> loadedLib = loadedByPath.get(libPath);
-					if (loadedLib == null) {
-						messageLog.appendMsg("Referenced external program not found: " + libName);
-						continue;
+				}
+			}
+			if (!shortSummary && changed) {
+				if (!unresolvedExternalFunctionIds.isEmpty()) {
+					logger.accept("\tUnresolved remaining %d:"
+							.formatted(unresolvedExternalFunctionIds.size()));
+					SymbolTable symbolTable = program.getSymbolTable();
+					for (Long symId : unresolvedExternalFunctionIds) {
+						Symbol s = symbolTable.getSymbol(symId);
+						logger.accept("\t\t[%s]".formatted(s.getName()));
 					}
-
-					Program libProgram = loadedLib.getDomainObject();
-					monitor.setMessage("Resolving symbols published by library " + libName);
-					resolveSymbolsToLibrary(program, unresolvedExternalFunctionIds, extLibrary,
-						libProgram, messageLog, monitor);
 				}
-				messageLog.appendMsg("Unresolved external symbols which remain: " +
-					unresolvedExternalFunctionIds.size());
 			}
 		}
-	}
 
-	private static void resolveSymbolsToLibrary(Program program,
-			Collection<Long> unresolvedExternalFunctionIds, Library extLibrary, Program libProgram,
-			MessageLog messageLog, TaskMonitor monitor) throws CancelledException {
-		int libResolvedCount = 0;
-		ExternalManager externalManager = program.getExternalManager();
-		SymbolTable symbolTable = program.getSymbolTable();
-
-		Iterator<Long> idIterator = unresolvedExternalFunctionIds.iterator();
-		while (idIterator.hasNext()) {
-			monitor.checkCancelled();
-			Symbol s = symbolTable.getSymbol(idIterator.next());
-			if (s == null || !s.isExternal() || s.getSymbolType() != SymbolType.FUNCTION) {
-				Msg.error(ExternalSymbolResolver.class,
-					"Concurrent modification of symbol table while resolving external symbols");
-				idIterator.remove();
-				continue;
-			}
-
-			ExternalLocation extLoc = externalManager.getExternalLocation(s);
-			if (s.getSource() == SourceType.DEFAULT ||
-				!isLocationContainedInLibrary(libProgram, extLoc)) {
-				continue;
-			}
-			try {
-				s.setNamespace(extLibrary);
-				idIterator.remove();
-				libResolvedCount++;
-				Msg.debug(ExternalSymbolResolver.class, "External symbol " + extLoc.getLabel() +
-					" resolved to " + extLibrary.getName());
-			}
-			catch (DuplicateNameException | InvalidInputException | CircularDependencyException e) {
-				Msg.error(ExternalSymbolResolver.class,
-					"Error setting external symbol namespace for " + extLoc.getLabel(), e);
-			}
-		}
-		messageLog.appendMsg(
-			"Resolved " + libResolvedCount + " symbols to library " + extLibrary.getName());
-	}
+		private boolean hasSomeLibrariesConfigured() {
+			for (ExtLibInfo extLib : extLibs) {
+				if (extLib.program != null || extLib.problem != null ||
+					extLib.programPath != null) {
+					return true;
+				}
+			}
+			return false;
+		}
 
-	private static boolean isLocationContainedInLibrary(Program libProgram,
-			ExternalLocation extLoc) {
+		private void resolveExternalSymbols() throws CancelledException {
+			unresolvedExternalFunctionIds = getUnresolvedExternalFunctionIds();
+			externalSymbolCount = unresolvedExternalFunctionIds.size();
 
-		String name = extLoc.getOriginalImportedName();
-		if (name == null) {
-			name = extLoc.getLabel();
-		}
-		for (Symbol s : libProgram.getSymbolTable().getLabelOrFunctionSymbols(name, null)) {
-			if (s.isExternalEntryPoint()) {
-				return true;
+			if (unresolvedExternalFunctionIds.isEmpty()) {
+				return;
 			}
-		}
-		return false;
-	}
 
-	private static Collection<Long> getUnresolvedExternalFunctionIds(Program program) {
-		List<Long> symbolIds = new ArrayList<>();
-		ExternalManager externalManager = program.getExternalManager();
-		Library library = externalManager.getExternalLibrary(Library.UNKNOWN);
-		if (library != null) {
-			for (Symbol s : program.getSymbolTable().getSymbols(library)) {
-				if (s.getSymbolType() == SymbolType.FUNCTION) {
-					symbolIds.add(s.getID());
+			extLibs = getLibsToSearch();
+
+			if (!extLibs.isEmpty()) {
+				try (Transaction tx = program.openTransaction("Resolve External Symbols")) {
+					for (ExtLibInfo extLib : extLibs) {
+						monitor.checkCancelled();
+						resolveSymbolsToLibrary(extLib);
+					}
 				}
 			}
+
 		}
-		return symbolIds;
-	}
 
-	private static Collection<String> getOrderedLibraryNamesNeeded(Program program) {
-		TreeMap<Integer, String> orderLibraryMap = new TreeMap<>();
-		Options options = program.getOptions(Program.PROGRAM_INFO);
-		for (String optionName : options.getOptionNames()) {
+		/**
+		 * Returns an ordered list of external libraries that need to be searched.
+		 * 
+		 * @return list of ExtLibInfo elements, each representing an external library dependency
+		 * found in the {@link #program}
+		 * @throws CancelledException if cancelled
+		 */
+		private List<ExtLibInfo> getLibsToSearch() throws CancelledException {
+			List<ExtLibInfo> result = new ArrayList<>();
+			ExternalManager externalManager = program.getExternalManager();
+			for (String libName : getOrderedRequiredLibraryNames()) {
+				Library lib = externalManager.getExternalLibrary(libName);
+				String libPath = lib != null ? lib.getAssociatedProgramPath() : null;
+				Program libProg = libPath != null ? getLibraryProgram(libPath) : null;
+				Throwable problem =
+					libProg == null && libPath != null ? problemLibraries.get(libPath) : null;
 
-			// Legacy programs may have the old "ELF Required Library [" program property, so 
-			// we should not assume that the option name starts exactly with 
-			// REQUIRED_LIBRARY_PROPERTY_PREFIX.  We must deal with a potential substring at the
-			// start of the option name.
-			int prefixIndex = optionName.indexOf(REQUIRED_LIBRARY_PROPERTY_PREFIX);
-			if (prefixIndex == -1 || !optionName.endsWith("]")) {
-				continue;
+				result.add(
+					new ExtLibInfo(libName, lib, libPath, libProg, new ArrayList<>(), problem));
 			}
-			String libName = options.getString(optionName, null);
-			if (libName == null) {
-				continue;
+			return result;
+		}
+
+		/**
+		 * Moves unresolved functions from the EXTERNAL/UNKNOWN namespace to the namespace of the 
+		 * external library if the extLib publishes a symbol with a matching name.
+		 * 
+		 * @param extLib  {@link ExtLibInfo} representing an external library
+		 * @throws CancelledException if cancelled
+		 */
+		private void resolveSymbolsToLibrary(ExtLibInfo extLib) throws CancelledException {
+			if (extLib.program == null) {
+				// can't do anything if the external library doesn't have a valid program associated 
+				return;
 			}
-			String indexStr = optionName
-					.substring(prefixIndex + REQUIRED_LIBRARY_PROPERTY_PREFIX.length(),
-						optionName.length() - 1)
-					.trim();
-			try {
-				orderLibraryMap.put(Integer.parseInt(indexStr), libName.trim());
+			ExternalManager externalManager = program.getExternalManager();
+			SymbolTable symbolTable = program.getSymbolTable();
+
+			for (Iterator<Long> idIterator = unresolvedExternalFunctionIds.iterator(); idIterator
+					.hasNext();) {
+				monitor.checkCancelled();
+				Symbol s = symbolTable.getSymbol(idIterator.next());
+				if (s == null || !s.isExternal() || s.getSymbolType() != SymbolType.FUNCTION) {
+					Msg.error(ExternalSymbolResolver.class,
+						"Concurrent modification of symbol table while resolving external symbols");
+					idIterator.remove();
+					continue;
+				}
+
+				ExternalLocation extLoc = externalManager.getExternalLocation(s);
+				String extLocName =
+					Objects.requireNonNullElse(extLoc.getOriginalImportedName(), extLoc.getLabel());
+				if (isExportedSymbol(extLib.program, extLocName)) {
+					try {
+						s.setNamespace(extLib.lib);
+						idIterator.remove();
+						extLib.resolvedSymbols.add(s.getName());
+					}
+					catch (DuplicateNameException | InvalidInputException
+							| CircularDependencyException e) {
+						Msg.error(ExternalSymbolResolver.class,
+							"Error setting external symbol namespace for " + extLoc.getLabel(), e);
+					}
+				}
 			}
-			catch (NumberFormatException e) {
-				Msg.error(ExternalSymbolResolver.class,
-					"Program contains invalid property: " + optionName);
+		}
+
+		/**
+		 * Returns a list of all external functions under the EXTERNAL/UNKNOWN library.
+		 * 
+		 * @return list of func ids that need to be fixed
+		 */
+		private List<Long> getUnresolvedExternalFunctionIds() {
+			List<Long> symbolIds = new ArrayList<>();
+			ExternalManager externalManager = program.getExternalManager();
+			Library library = externalManager.getExternalLibrary(Library.UNKNOWN);
+			if (library != null) {
+				for (Symbol s : program.getSymbolTable().getSymbols(library)) {
+					if (s.getSymbolType() == SymbolType.FUNCTION &&
+						s.getSource() != SourceType.DEFAULT) {
+						symbolIds.add(s.getID());
+					}
+				}
+			}
+			return symbolIds;
+		}
+
+		/**
+		 * Returns an ordered list of library names, as specified by the logic/rules of the original
+		 * operating system's loader (eg. Elf / MachO dynamic library loading / symbol resolving
+		 * rules)
+		 *  
+		 * @return list of library names, in original order
+		 */
+		private Collection<String> getOrderedRequiredLibraryNames() {
+			TreeMap<Integer, String> orderLibraryMap = new TreeMap<>();
+			Options options = program.getOptions(Program.PROGRAM_INFO);
+			for (String optionName : options.getOptionNames()) {
+
+				// Legacy programs may have the old "ELF Required Library [" program property, so 
+				// we should not assume that the option name starts exactly with 
+				// REQUIRED_LIBRARY_PROPERTY_PREFIX.  We must deal with a potential substring at the
+				// start of the option name.
+				int prefixIndex = optionName.indexOf(REQUIRED_LIBRARY_PROPERTY_PREFIX);
+				if (prefixIndex == -1 || !optionName.endsWith("]")) {
+					continue;
+				}
+				String libName = options.getString(optionName, null);
+				if (libName == null) {
+					continue;
+				}
+				String indexStr = optionName
+						.substring(prefixIndex + REQUIRED_LIBRARY_PROPERTY_PREFIX.length(),
+							optionName.length() - 1)
+						.trim();
+				try {
+					orderLibraryMap.put(Integer.parseInt(indexStr), libName.trim());
+				}
+				catch (NumberFormatException e) {
+					Msg.error(ExternalSymbolResolver.class,
+						"Program contains invalid property: " + optionName);
+				}
 			}
+			return orderLibraryMap.values();
 		}
-		return orderLibraryMap.values();
+
 	}
 
-	public static List<Library> getLibrarySearchList(Program program) {
-		List<Library> result = new ArrayList<>();
-		ExternalManager externalManager = program.getExternalManager();
-		for (String libName : getOrderedLibraryNamesNeeded(program)) {
-			Library lib = externalManager.getExternalLibrary(libName);
-			if (lib != null) {
-				result.add(lib);
+	/**
+	 * Returns true if the specified program publishes a symbol with the specified name.
+	 * 
+	 * @param program {@link Program}
+	 * @param name symbol name
+	 * @return true if program publishes a symbol the specified name
+	 */
+	private static boolean isExportedSymbol(Program program, String name) {
+
+		for (Symbol s : program.getSymbolTable().getLabelOrFunctionSymbols(name, null)) {
+			if (s.isExternalEntryPoint()) {
+				return true;
 			}
 		}
-		return result;
+		return false;
 	}
+
 }