Loader Development

What is a Loader?

Loaders enable Ghidra to import and parse binary file formats. They:

Identify supported file formats
Parse file headers and structures
Create memory blocks and segments
Define entry points and exports
Apply relocations and imports
Set up initial program metadata

Loader Interface

All loaders must implement the Loader interface:

Critical: Loader class names must end with Loader for automatic discovery.

package ghidra.app.util.opinion;

public interface Loader extends ExtensionPoint, Comparable<Loader> {
    Collection<LoadSpec> findSupportedLoadSpecs(ByteProvider provider) 
        throws IOException;
    
    LoadResults load(LoadConfig config, MessageLog log) 
        throws IOException, CancelledException;
    
    String getName();
    
    List<Option> getDefaultOptions(ByteProvider provider, 
        LoadSpec loadSpec, DomainObject domainObject, 
        boolean loadIntoProgram, boolean mirrorFsLayout);
    
    String validateOptions(ByteProvider provider, LoadSpec loadSpec, 
        List<Option> options, Program program);
}

Loader Base Classes

Ghidra provides several base classes:

AbstractProgramLoader

For format-specific loaders:

import ghidra.app.util.opinion.AbstractProgramLoader;

public class MyFormatLoader extends AbstractProgramLoader {
    // Implement abstract methods
}

AbstractProgramWrapperLoader

For wrapper formats (compression, containers):

import ghidra.app.util.opinion.AbstractProgramWrapperLoader;

public class MyWrapperLoader extends AbstractProgramWrapperLoader {
    // Implement abstract methods
}

AbstractLibrarySupportLoader

For formats with library/import support:

import ghidra.app.util.opinion.AbstractLibrarySupportLoader;

public class MyLibraryLoader extends AbstractLibrarySupportLoader {
    // Implement abstract methods
}

Creating a Basic Loader

package com.example.loaders;

import ghidra.app.util.Option;
import ghidra.app.util.bin.ByteProvider;
import ghidra.app.util.importer.MessageLog;
import ghidra.app.util.opinion.*;
import ghidra.framework.model.DomainObject;
import ghidra.program.model.listing.Program;
import ghidra.util.exception.CancelledException;
import ghidra.util.task.TaskMonitor;

import java.io.IOException;
import java.util.*;

public class MyFormatLoader extends AbstractProgramWrapperLoader {
    
    public static final String MY_FORMAT_NAME = "My Binary Format";
    
    @Override
    public String getName() {
        return MY_FORMAT_NAME;
    }
    
    @Override
    public Collection<LoadSpec> findSupportedLoadSpecs(ByteProvider provider) 
            throws IOException {
        List<LoadSpec> loadSpecs = new ArrayList<>();
        
        // Check file signature/magic bytes
        if (isMyFormat(provider)) {
            // Add supported architectures
            loadSpecs.add(new LoadSpec(this, 0, 
                new LanguageCompilerSpecPair("x86:LE:32:default", "gcc"), 
                true));
        }
        
        return loadSpecs;
    }
    
    private boolean isMyFormat(ByteProvider provider) throws IOException {
        // Check magic bytes or other format identifiers
        byte[] magic = provider.readBytes(0, 4);
        return (magic[0] == 0x4D && magic[1] == 0x59 && 
                magic[2] == 0x46 && magic[3] == 0x4D);  // "MYFM"
    }
    
    @Override
    protected void load(Program program, ImporterSettings settings)
            throws IOException, CancelledException {
        
        ByteProvider provider = settings.provider();
        TaskMonitor monitor = settings.monitor();
        MessageLog log = settings.log();
        
        monitor.setMessage("Loading " + MY_FORMAT_NAME + "...");
        
        // Parse format and create program structure
        parseHeader(program, provider, log);
        createMemoryBlocks(program, provider, monitor, log);
        defineEntryPoint(program, log);
    }
    
    private void parseHeader(Program program, ByteProvider provider, 
                            MessageLog log) throws IOException {
        // Read and parse file header
    }
    
    private void createMemoryBlocks(Program program, ByteProvider provider,
                                   TaskMonitor monitor, MessageLog log) {
        // Create memory segments
    }
    
    private void defineEntryPoint(Program program, MessageLog log) {
        // Set program entry point
    }
}

Format Detection

Magic Bytes

@Override
public Collection<LoadSpec> findSupportedLoadSpecs(ByteProvider provider)
        throws IOException {
    List<LoadSpec> loadSpecs = new ArrayList<>();
    
    // Check file size
    if (provider.length() < 16) {
        return loadSpecs;
    }
    
    // Read magic bytes
    byte[] magic = provider.readBytes(0, 4);
    if (!isMagicValid(magic)) {
        return loadSpecs;
    }
    
    // Read architecture indicator
    int archType = provider.readInt(4);
    
    // Determine language spec
    LanguageCompilerSpecPair langSpec = getLanguageSpec(archType);
    if (langSpec != null) {
        loadSpecs.add(new LoadSpec(this, 0, langSpec, true));
    }
    
    return loadSpecs;
}

private boolean isMagicValid(byte[] magic) {
    return magic[0] == (byte) 0x7F && 
           magic[1] == 'E' && 
           magic[2] == 'L' && 
           magic[3] == 'F';  // ELF format
}

private LanguageCompilerSpecPair getLanguageSpec(int archType) {
    switch (archType) {
        case 0x03:  // x86
            return new LanguageCompilerSpecPair("x86:LE:32:default", "gcc");
        case 0x3E:  // x86-64
            return new LanguageCompilerSpecPair("x86:LE:64:default", "gcc");
        case 0x28:  // ARM
            return new LanguageCompilerSpecPair("ARM:LE:32:v7", "default");
        default:
            return null;
    }
}

Creating Memory Blocks

import ghidra.program.model.address.*;
import ghidra.program.model.mem.*;

private void createMemoryBlocks(Program program, ByteProvider provider,
                               TaskMonitor monitor, MessageLog log) 
                               throws IOException {
    Memory memory = program.getMemory();
    AddressFactory addrFactory = program.getAddressFactory();
    AddressSpace space = addrFactory.getDefaultAddressSpace();
    
    int transactionID = program.startTransaction("Create Memory");
    try {
        // Create code segment
        Address codeStart = space.getAddress(0x00401000);
        MemoryBlock codeBlock = memory.createInitializedBlock(
            ".text",               // Block name
            codeStart,             // Start address
            provider.getInputStream(0x1000),  // Data source
            0x10000,               // Length
            monitor,
            false                  // Don't overlay
        );
        codeBlock.setRead(true);
        codeBlock.setWrite(false);
        codeBlock.setExecute(true);
        
        // Create data segment
        Address dataStart = space.getAddress(0x00411000);
        MemoryBlock dataBlock = memory.createInitializedBlock(
            ".data",
            dataStart,
            provider.getInputStream(0x11000),
            0x1000,
            monitor,
            false
        );
        dataBlock.setRead(true);
        dataBlock.setWrite(true);
        dataBlock.setExecute(false);
        
        // Create BSS (uninitialized data)
        Address bssStart = space.getAddress(0x00412000);
        MemoryBlock bssBlock = memory.createUninitializedBlock(
            ".bss",
            bssStart,
            0x1000,
            false
        );
        bssBlock.setRead(true);
        bssBlock.setWrite(true);
        bssBlock.setExecute(false);
        
        program.endTransaction(transactionID, true);
    }
    catch (Exception e) {
        program.endTransaction(transactionID, false);
        log.appendException(e);
    }
}

Setting Entry Point

import ghidra.program.model.symbol.*;

private void defineEntryPoint(Program program, MessageLog log) {
    try {
        AddressSpace space = program.getAddressFactory().getDefaultAddressSpace();
        Address entry = space.getAddress(0x00401000);
        
        int transactionID = program.startTransaction("Set Entry Point");
        try {
            // Add entry point symbol
            SymbolTable symbolTable = program.getSymbolTable();
            symbolTable.addExternalEntryPoint(entry);
            symbolTable.createLabel(entry, "entry", SourceType.IMPORTED);
            
            // Set image base
            program.setImageBase(space.getAddress(0x00400000), true);
            
            program.endTransaction(transactionID, true);
        }
        catch (Exception e) {
            program.endTransaction(transactionID, false);
            log.appendException(e);
        }
    }
    catch (Exception e) {
        log.appendException(e);
    }
}

Adding Relocations

import ghidra.program.model.reloc.*;

private void processRelocations(Program program, ByteProvider provider,
                               MessageLog log) throws IOException {
    RelocationTable relocTable = program.getRelocationTable();
    
    int transactionID = program.startTransaction("Add Relocations");
    try {
        // Read relocation entries from file
        long relocOffset = 0x2000;
        int relocCount = provider.readInt(relocOffset);
        
        for (int i = 0; i < relocCount; i++) {
            long offset = relocOffset + 4 + (i * 8);
            int relocAddr = provider.readInt(offset);
            int relocType = provider.readInt(offset + 4);
            
            Address addr = program.getAddressFactory()
                .getDefaultAddressSpace()
                .getAddress(relocAddr);
            
            relocTable.add(addr, relocType, null, null, null);
        }
        
        program.endTransaction(transactionID, true);
    }
    catch (Exception e) {
        program.endTransaction(transactionID, false);
        log.appendException(e);
    }
}

Import/Export Tables

import ghidra.program.model.listing.Function;
import ghidra.program.model.listing.FunctionManager;

private void processExports(Program program, ByteProvider provider,
                           MessageLog log) throws IOException {
    SymbolTable symbolTable = program.getSymbolTable();
    FunctionManager funcMgr = program.getFunctionManager();
    
    int transactionID = program.startTransaction("Add Exports");
    try {
        // Read export table from file
        long exportOffset = 0x3000;
        int exportCount = provider.readInt(exportOffset);
        
        for (int i = 0; i < exportCount; i++) {
            long offset = exportOffset + 4 + (i * 12);
            int address = provider.readInt(offset);
            int nameOffset = provider.readInt(offset + 4);
            
            // Read function name
            String name = readString(provider, nameOffset);
            
            Address addr = program.getAddressFactory()
                .getDefaultAddressSpace()
                .getAddress(address);
            
            // Create function and symbol
            Function func = funcMgr.createFunction(name, addr, 
                new AddressSet(addr), SourceType.IMPORTED);
            
            Symbol symbol = symbolTable.createLabel(addr, name, 
                SourceType.IMPORTED);
            symbol.setPrimary();
        }
        
        program.endTransaction(transactionID, true);
    }
    catch (Exception e) {
        program.endTransaction(transactionID, false);
        log.appendException(e);
    }
}

private String readString(ByteProvider provider, long offset) 
        throws IOException {
    StringBuilder sb = new StringBuilder();
    byte b;
    while ((b = provider.readByte(offset++)) != 0) {
        sb.append((char) b);
    }
    return sb.toString();
}

Loader Options

@Override
public List<Option> getDefaultOptions(ByteProvider provider, 
        LoadSpec loadSpec, DomainObject domainObject, 
        boolean loadIntoProgram, boolean mirrorFsLayout) {
    
    List<Option> options = super.getDefaultOptions(provider, loadSpec, 
        domainObject, loadIntoProgram, mirrorFsLayout);
    
    options.add(new Option("Load Debug Symbols", true));
    options.add(new Option("Apply Relocations", true));
    options.add(new Option("Base Address", 0x00400000));
    
    return options;
}

@Override
public String validateOptions(ByteProvider provider, LoadSpec loadSpec,
        List<Option> options, Program program) {
    
    // Validate custom options
    for (Option option : options) {
        String name = option.getName();
        if (name.equals("Base Address")) {
            long baseAddr = (Long) option.getValue();
            if (baseAddr < 0 || baseAddr > 0xFFFFFFFFL) {
                return "Base address must be between 0 and 0xFFFFFFFF";
            }
        }
    }
    
    return super.validateOptions(provider, loadSpec, options, program);
}

// Access options during load
@Override
protected void load(Program program, ImporterSettings settings)
        throws IOException, CancelledException {
    
    boolean loadDebugSymbols = settings.getBoolean("Load Debug Symbols");
    boolean applyRelocations = settings.getBoolean("Apply Relocations");
    long baseAddress = settings.getLong("Base Address");
    
    // Use options in load process
}

Binary Parsing Utilities

Ghidra provides utilities for reading binary structures:

import ghidra.app.util.bin.BinaryReader;
import ghidra.app.util.bin.ByteProvider;
import ghidra.app.util.bin.StructConverter;
import ghidra.program.model.data.*;

public class MyFormatHeader implements StructConverter {
    
    private int magic;
    private int version;
    private int archType;
    private int entryPoint;
    
    public MyFormatHeader(BinaryReader reader) throws IOException {
        magic = reader.readNextInt();
        version = reader.readNextInt();
        archType = reader.readNextInt();
        entryPoint = reader.readNextInt();
    }
    
    public boolean isValid() {
        return magic == 0x4D59464D;  // "MYFM"
    }
    
    @Override
    public DataType toDataType() {
        Structure struct = new StructureDataType("MyFormatHeader", 0);
        struct.add(DWordDataType.dataType, "magic", null);
        struct.add(DWordDataType.dataType, "version", null);
        struct.add(DWordDataType.dataType, "archType", null);
        struct.add(DWordDataType.dataType, "entryPoint", null);
        return struct;
    }
    
    public int getEntryPoint() {
        return entryPoint;
    }
}

// Usage in loader
private void parseHeader(Program program, ByteProvider provider,
                        MessageLog log) throws IOException {
    BinaryReader reader = new BinaryReader(provider, true);  // little-endian
    MyFormatHeader header = new MyFormatHeader(reader);
    
    if (!header.isValid()) {
        throw new IOException("Invalid file format");
    }
    
    // Apply header as data type
    int transactionID = program.startTransaction("Apply Header");
    try {
        Address headerAddr = program.getAddressFactory()
            .getDefaultAddressSpace()
            .getAddress(0);
        
        program.getListing().createData(headerAddr, header.toDataType());
        program.endTransaction(transactionID, true);
    }
    catch (Exception e) {
        program.endTransaction(transactionID, false);
        log.appendException(e);
    }
}

Real-World Example: ELF Loader

Based on Ghidra’s ElfLoader:

public class ElfLoader extends AbstractLibrarySupportLoader {
    
    public static final String ELF_NAME = "Executable and Linking Format (ELF)";
    
    @Override
    public String getName() {
        return ELF_NAME;
    }
    
    @Override
    public Collection<LoadSpec> findSupportedLoadSpecs(ByteProvider provider)
            throws IOException {
        List<LoadSpec> loadSpecs = new ArrayList<>();
        
        if (!ElfHeader.isElfHeader(provider)) {
            return loadSpecs;
        }
        
        try {
            ElfHeader elf = ElfHeader.createElfHeader(
                RethrowContinuesFactory.INSTANCE, provider);
            elf.parse();
            
            List<LanguageCompilerSpecPair> lcsList = 
                ElfLoaderOptionsFactory.getLanguageCompilerSpecPairs(elf);
            
            for (LanguageCompilerSpecPair lcs : lcsList) {
                loadSpecs.add(new LoadSpec(this, elf.getImageBase(), lcs, true));
            }
        }
        catch (Exception e) {
            // Not a valid ELF
        }
        
        return loadSpecs;
    }
    
    @Override
    protected void load(Program program, ImporterSettings settings)
            throws IOException, CancelledException {
        
        ByteProvider provider = settings.provider();
        TaskMonitor monitor = settings.monitor();
        MessageLog log = settings.log();
        
        monitor.setMessage("Loading ELF...");
        
        ElfHeader elf = ElfHeader.createElfHeader(
            RethrowContinuesFactory.INSTANCE, provider);
        elf.parse();
        
        ElfProgramBuilder.loadElf(elf, program, settings, log, monitor);
    }
}

Testing Loaders

From Ghidra GUI

Launch Ghidra with your loader extension
File → Import File…
Select test binary
Verify your loader appears in format list
Select loader and configure options
Click OK and verify results

Headless Testing

./analyzeHeadless <project_path> <project_name> \
  -import <binary> \
  -loader MyFormatLoader \
  -postScript VerifyImport.java

Complete Example

package com.example.loaders;

import ghidra.app.util.Option;
import ghidra.app.util.bin.*;
import ghidra.app.util.importer.MessageLog;
import ghidra.app.util.opinion.*;
import ghidra.framework.model.DomainObject;
import ghidra.program.model.address.*;
import ghidra.program.model.listing.Program;
import ghidra.program.model.mem.*;
import ghidra.program.model.symbol.*;
import ghidra.util.exception.CancelledException;
import ghidra.util.task.TaskMonitor;

import java.io.IOException;
import java.util.*;

public class SimpleFormatLoader extends AbstractProgramWrapperLoader {
    
    public static final String SIMPLE_FORMAT_NAME = "Simple Binary Format";
    private static final int MAGIC = 0x53494D50;  // "SIMP"
    
    @Override
    public String getName() {
        return SIMPLE_FORMAT_NAME;
    }
    
    @Override
    public Collection<LoadSpec> findSupportedLoadSpecs(ByteProvider provider)
            throws IOException {
        List<LoadSpec> loadSpecs = new ArrayList<>();
        
        if (provider.length() < 16) {
            return loadSpecs;
        }
        
        BinaryReader reader = new BinaryReader(provider, true);
        int magic = reader.readInt(0);
        
        if (magic == MAGIC) {
            loadSpecs.add(new LoadSpec(this, 0,
                new LanguageCompilerSpecPair("x86:LE:32:default", "gcc"),
                true));
        }
        
        return loadSpecs;
    }
    
    @Override
    protected void load(Program program, ImporterSettings settings)
            throws IOException, CancelledException {
        
        ByteProvider provider = settings.provider();
        TaskMonitor monitor = settings.monitor();
        MessageLog log = settings.log();
        
        monitor.setMessage("Loading Simple Binary Format...");
        
        BinaryReader reader = new BinaryReader(provider, true);
        
        // Read header
        int magic = reader.readInt(0);
        int codeOffset = reader.readInt(4);
        int codeSize = reader.readInt(8);
        int entryPoint = reader.readInt(12);
        
        log.appendMsg("Magic: 0x" + Integer.toHexString(magic));
        log.appendMsg("Code offset: 0x" + Integer.toHexString(codeOffset));
        log.appendMsg("Code size: 0x" + Integer.toHexString(codeSize));
        log.appendMsg("Entry point: 0x" + Integer.toHexString(entryPoint));
        
        // Create memory blocks
        Memory memory = program.getMemory();
        AddressSpace space = program.getAddressFactory().getDefaultAddressSpace();
        
        int transactionID = program.startTransaction("Load Binary");
        try {
            // Create code block
            Address codeAddr = space.getAddress(0x00401000);
            MemoryBlock codeBlock = memory.createInitializedBlock(
                ".text",
                codeAddr,
                provider.getInputStream(codeOffset),
                codeSize,
                monitor,
                false
            );
            codeBlock.setRead(true);
            codeBlock.setExecute(true);
            
            // Set entry point
            Address entry = codeAddr.add(entryPoint);
            SymbolTable symbolTable = program.getSymbolTable();
            symbolTable.addExternalEntryPoint(entry);
            symbolTable.createLabel(entry, "entry", SourceType.IMPORTED);
            
            // Set image base
            program.setImageBase(space.getAddress(0x00400000), true);
            
            program.endTransaction(transactionID, true);
            log.appendMsg("Load completed successfully");
        }
        catch (Exception e) {
            program.endTransaction(transactionID, false);
            log.appendException(e);
            throw new IOException("Load failed", e);
        }
    }
}

Best Practices

Do:

Validate file format thoroughly
Use transactions for all modifications
Log meaningful progress messages
Handle errors gracefully
Provide useful loader options
Document file format structure
Create appropriate memory block permissions

Don’t:

Assume file structure is valid
Create overlapping memory blocks
Forget to set entry points
Hardcode addresses (use options)
Ignore endianness

Resources

Loader examples: Ghidra/Features/Base/src/main/java/ghidra/app/util/opinion/
Skeleton template: GhidraBuild/Skeleton/src/main/java/skeleton/SkeletonLoader.java
Binary utilities: Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/
API docs: Loader

Get Started

Core Concepts

User Guide

Advanced Features

Scripting & Automation

Extension Development

Processors & Formats

Loader Development

What is a Loader?

Loader Interface

Loader Base Classes

AbstractProgramLoader

AbstractProgramWrapperLoader

AbstractLibrarySupportLoader

Creating a Basic Loader

Format Detection

Magic Bytes

Creating Memory Blocks

Setting Entry Point

Adding Relocations

Import/Export Tables

Loader Options

Binary Parsing Utilities

Real-World Example: ELF Loader

Testing Loaders

From Ghidra GUI

Headless Testing

Complete Example

Best Practices

Resources

Next Steps

Analyzer Development

Sleigh Language

Build docs developers (and LLMs) love

Get Started

Core Concepts

User Guide

Advanced Features

Scripting & Automation

Extension Development

Processors & Formats

​What is a Loader?

​Loader Interface

​Loader Base Classes

​AbstractProgramLoader

​AbstractProgramWrapperLoader

​AbstractLibrarySupportLoader

​Creating a Basic Loader

​Format Detection

​Magic Bytes

​Creating Memory Blocks

​Setting Entry Point

​Adding Relocations

​Import/Export Tables

​Loader Options

​Binary Parsing Utilities

​Real-World Example: ELF Loader

​Testing Loaders

​From Ghidra GUI

​Headless Testing

​Complete Example

​Best Practices

​Resources

​Next Steps

Analyzer Development

Sleigh Language

Build docs developers (and LLMs) love

What is a Loader?

Loader Interface

Loader Base Classes

AbstractProgramLoader

AbstractProgramWrapperLoader

AbstractLibrarySupportLoader

Creating a Basic Loader

Format Detection

Magic Bytes

Creating Memory Blocks

Setting Entry Point

Adding Relocations

Import/Export Tables

Loader Options

Binary Parsing Utilities

Real-World Example: ELF Loader

Testing Loaders

From Ghidra GUI

Headless Testing

Complete Example

Best Practices

Resources

Next Steps