GhidraRPXLoader/src/main/java/cafeloader/Cafe_ElfRelocationHandler.java

package cafeloader;

import ghidra.app.util.bin.format.elf.*;
import ghidra.app.util.bin.format.elf.relocation.ElfRelocationContext;
import ghidra.app.util.bin.format.elf.relocation.ElfRelocationHandler;
import ghidra.program.model.address.Address;
import ghidra.program.model.listing.Program;
import ghidra.program.model.mem.Memory;
import ghidra.program.model.mem.MemoryAccessException;
import ghidra.util.Msg;
import ghidra.util.exception.InvalidInputException;
import ghidra.util.exception.NotFoundException;
import ghidra.program.model.symbol.ExternalLocation;
import ghidra.program.model.symbol.RefType;
import ghidra.program.model.symbol.SourceType;
import ghidra.program.model.reloc.Relocation.Status;
import ghidra.program.model.reloc.RelocationResult;

public class Cafe_ElfRelocationHandler extends ElfRelocationHandler {
	@Override
	public boolean canRelocate(ElfHeader elf) {
		return elf instanceof RplHeader;
	}

	@Override
	public RelocationResult relocate(ElfRelocationContext elfRelocationContext, ElfRelocation relocation,
			Address relocationAddress) throws MemoryAccessException, NotFoundException {
		int type = relocation.getType();
		if (type == Cafe_ElfRelocationConstants.R_PPC_NONE) {
			return RelocationResult.SKIPPED;
		}

		ElfHeader elf = elfRelocationContext.getElfHeader();
		Program program = elfRelocationContext.getProgram();
		Memory memory = program.getMemory();
		int symbolIndex = relocation.getSymbolIndex();
		int addend = (int) relocation.getAddend();
		int offset = (int) relocationAddress.getOffset();
		ElfSymbol sym = elfRelocationContext.getSymbol(symbolIndex);
		int symbolValue = (int) elfRelocationContext.getSymbolValue(sym);
		int oldValue = memory.getInt(relocationAddress);
		int newValue = 0;

		int byteLength = 4; // most relocations affect 4-bytes (change if different)

		/*
		 * If the symbol is in a SHT_RPL_IMPORTS section then we must add a memory
		 * reference because it will be too far away for the actual relocation to
		 * be valid itself.
		 */
		
		if (sym.getSectionHeaderIndex() > 0) {	
    		ElfSectionHeader symbolSection = elf.getSections()[sym.getSectionHeaderIndex()];
    		if (symbolSection.getType() == Cafe_ElfExtension.SHT_RPL_IMPORTS.value) {
    			String symbolSectionName = symbolSection.getNameAsString();
    			boolean isDataImport = false;
    			if (symbolSectionName.startsWith(".dimport_")) {
    				program.getReferenceManager().addMemoryReference(relocationAddress,
    					elfRelocationContext.getSymbolAddress(sym), RefType.DATA, SourceType.IMPORTED, 0);
    				isDataImport = true;
    			} else if (symbolSectionName.startsWith(".fimport_")) {
    				program.getReferenceManager().addMemoryReference(relocationAddress,
    					elfRelocationContext.getSymbolAddress(sym), RefType.UNCONDITIONAL_CALL, SourceType.IMPORTED, 0);
    			}
    
    			String rplName = symbolSectionName.split("import_")[1];
    			if (!rplName.endsWith(".rpl")) {
    				 rplName += ".rpl";
    			}
    
    			ExternalLocation location = program.getExternalManager().getUniqueExternalLocation(rplName, sym.getNameAsString());
    			if (location != null) {
    				try {
    					if (isDataImport) {
    						program.getReferenceManager().addExternalReference(relocationAddress, 1,
    								  location, SourceType.IMPORTED, RefType.DATA);
    					} else {
    						program.getReferenceManager().addExternalReference(relocationAddress, 1,
    								  location, SourceType.IMPORTED, RefType.UNCONDITIONAL_CALL);
    					}
    				} catch (InvalidInputException e) {
    					Msg.warn(this, "addExternalReference failed with " + e);
    				}
    			} else {
    				Msg.warn(this, "Failed to find location for " + sym.getNameAsString());
    			}
    		}
		}

		switch (type) {
			case Cafe_ElfRelocationConstants.R_PPC_ADDR32:
				newValue = symbolValue + addend;
				memory.setInt(relocationAddress, newValue);
				break;
			case Cafe_ElfRelocationConstants.R_PPC_ADDR16_LO:
				newValue = symbolValue + addend;
				memory.setShort(relocationAddress, (short) newValue);
				byteLength = 2;
				break;
			case Cafe_ElfRelocationConstants.R_PPC_ADDR16_HI:
				newValue = (symbolValue + addend) >> 16;
				memory.setShort(relocationAddress, (short) newValue);
				byteLength = 2;
				break;
			case Cafe_ElfRelocationConstants.R_PPC_ADDR16_HA:
				newValue = (symbolValue + addend + 0x8000) >> 16;
				memory.setShort(relocationAddress, (short) newValue);
				byteLength = 2;
				break;
			case Cafe_ElfRelocationConstants.R_PPC_REL24:
				newValue = (symbolValue + addend - offset) >> 2;
				newValue = ((newValue << 2) & Cafe_ElfRelocationConstants.PPC_LOW24);
				newValue = (oldValue & ~Cafe_ElfRelocationConstants.PPC_LOW24) | newValue;
				memory.setInt(relocationAddress, newValue);
				break;
			case Cafe_ElfRelocationConstants.R_PPC_REL14:
				newValue = (symbolValue + addend - offset) >> 2;
				newValue = (oldValue & ~Cafe_ElfRelocationConstants.PPC_LOW14) |
					((newValue << 2) & Cafe_ElfRelocationConstants.PPC_LOW14);
				memory.setInt(relocationAddress, newValue);
				break;
			case Cafe_ElfRelocationConstants.R_PPC_GHS_REL16_HA:
				newValue = (symbolValue + addend - offset + 0x8000) >> 16;
				memory.setShort(relocationAddress, (short) newValue);
				byteLength = 2;
				break;
			case Cafe_ElfRelocationConstants.R_PPC_GHS_REL16_HI:
				newValue = (symbolValue + addend - offset) >> 16;
				memory.setShort(relocationAddress, (short) newValue);
				byteLength = 2;
				break;
			case Cafe_ElfRelocationConstants.R_PPC_GHS_REL16_LO:
				newValue = (symbolValue + addend - offset);
				memory.setShort(relocationAddress, (short) newValue);
				byteLength = 2;
				break;
			case Cafe_ElfRelocationConstants.R_PPC_DTPREL32:
				newValue = symbolValue + addend;
				memory.setInt(relocationAddress, newValue);
				break;
			case Cafe_ElfRelocationConstants.R_PPC_DTPMOD32:
				// TODO: Do we need a tlsModuleIndex?
				// *virt_cast<int32_t *>(target) = tlsModuleIndex;
				memory.setInt(relocationAddress, 0);
				break;
			case Cafe_ElfRelocationConstants.R_PPC_EMB_SDA21:
				// TODO: SDA relocations require sda / sda2 base from SHT_RPL_FILEINFO section
			case Cafe_ElfRelocationConstants.R_PPC_EMB_RELSDA:
			case Cafe_ElfRelocationConstants.R_PPC_DIAB_SDA21_LO:
			case Cafe_ElfRelocationConstants.R_PPC_DIAB_SDA21_HI:
			case Cafe_ElfRelocationConstants.R_PPC_DIAB_SDA21_HA:
			case Cafe_ElfRelocationConstants.R_PPC_DIAB_RELSDA_LO:
			case Cafe_ElfRelocationConstants.R_PPC_DIAB_RELSDA_HI:
			case Cafe_ElfRelocationConstants.R_PPC_DIAB_RELSDA_HA:
			default:
				return RelocationResult.UNSUPPORTED;
		}

		return new RelocationResult(Status.APPLIED, byteLength);
	}
}