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Move handling of HI16/LO16 relocs for non-relocatable reference sections into elf parsing by patching the output binary (fixes patch regeneration) (#127)

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Wiseguy 2025-01-30 02:54:27 -05:00 committed by GitHub
parent b18e0ca2dd
commit 198de1b5cf
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2 changed files with 32 additions and 11 deletions
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32
src/elf.cpp
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@ -104,10 +104,10 @@ bool read_symbols(N64Recomp::Context& context, const ELFIO::elfio& elf_file, ELF
if (section_index < context.sections.size()) {
auto section_offset = value - elf_file.sections[section_index]->get_address();
const uint32_t* words = reinterpret_cast<const uint32_t*>(elf_file.sections[section_index]->get_data() + section_offset);
uint32_t vram = static_cast<uint32_t>(value);
uint32_t num_instructions = type == ELFIO::STT_FUNC ? size / 4 : 0;
uint32_t rom_address = static_cast<uint32_t>(section_offset + section.rom_addr);
const uint32_t* words = reinterpret_cast<const uint32_t*>(context.rom.data() + rom_address);
section.function_addrs.push_back(vram);
context.functions_by_vram[vram].push_back(context.functions.size());
@ -551,6 +551,36 @@ ELFIO::section* read_sections(N64Recomp::Context& context, const N64Recomp::ElfP
return a.address < b.address;
}
);
// Patch the ROM word for HI16 and LO16 reference symbol relocs to non-relocatable sections.
for (size_t i = 0; i < section_out.relocs.size(); i++) {
auto& reloc = section_out.relocs[i];
if (reloc.reference_symbol && (reloc.type == N64Recomp::RelocType::R_MIPS_HI16 || reloc.type == N64Recomp::RelocType::R_MIPS_LO16)) {
bool target_section_relocatable = context.is_reference_section_relocatable(reloc.target_section);
if (!target_section_relocatable) {
uint32_t reloc_rom_addr = reloc.address - section_out.ram_addr + section_out.rom_addr;
uint32_t reloc_rom_word = byteswap(*reinterpret_cast<const uint32_t*>(context.rom.data() + reloc_rom_addr));
uint32_t ref_section_vram = context.get_reference_section_vram(reloc.target_section);
uint32_t full_immediate = reloc.target_section_offset + ref_section_vram;
uint32_t imm;
if (reloc.type == N64Recomp::RelocType::R_MIPS_HI16) {
imm = (full_immediate >> 16) + ((full_immediate >> 15) & 1);
}
else {
imm = full_immediate & 0xFFFF;
}
*reinterpret_cast<uint32_t*>(context.rom.data() + reloc_rom_addr) = byteswap(reloc_rom_word | imm);
// Remove the reloc by setting it to a type of NONE.
reloc.type = N64Recomp::RelocType::R_MIPS_NONE;
reloc.reference_symbol = false;
reloc.symbol_index = (uint32_t)-1;
}
}
}
}
}

11
src/recompilation.cpp
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@ -184,19 +184,10 @@ bool process_instruction(GeneratorType& generator, const N64Recomp::Context& con
reloc_reference_symbol = reloc.symbol_index;
// Don't try to relocate special section symbols.
if (context.is_regular_reference_section(reloc.target_section) || reloc_section == N64Recomp::SectionAbsolute) {
// TODO this may not be needed anymore as HI16/LO16 relocs to non-relocatable sections is handled directly in elf parsing.
bool ref_section_relocatable = context.is_reference_section_relocatable(reloc.target_section);
// Resolve HI16 and LO16 reference symbol relocs to non-relocatable sections by patching the instruction immediate.
if (!ref_section_relocatable && (reloc_type == N64Recomp::RelocType::R_MIPS_HI16 || reloc_type == N64Recomp::RelocType::R_MIPS_LO16)) {
uint32_t ref_section_vram = context.get_reference_section_vram(reloc.target_section);
uint32_t full_immediate = reloc.target_section_offset + ref_section_vram;
if (reloc_type == N64Recomp::RelocType::R_MIPS_HI16) {
imm = (full_immediate >> 16) + ((full_immediate >> 15) & 1);
}
else if (reloc_type == N64Recomp::RelocType::R_MIPS_LO16) {
imm = full_immediate & 0xFFFF;
}
// The reloc has been processed, so set it to none to prevent it getting processed a second time during instruction code generation.
reloc_type = N64Recomp::RelocType::R_MIPS_NONE;
reloc_reference_symbol = (size_t)-1;