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Implement reloc pairing GNU extension (#131)

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Wiseguy 2025-02-13 18:20:48 -05:00 • committed by GitHub
parent 8781eb44ac
commit d660733116
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1 changed files with 30 additions and 10 deletions
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src/elf.cpp
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@ -368,8 +368,8 @@ ELFIO::section* read_sections(N64Recomp::Context& context, const N64Recomp::ElfP
ELFIO::relocation_section_accessor rel_accessor{ elf_file, reloc_find->second };
// Allocate space for the relocs in this section
section_out.relocs.resize(rel_accessor.get_entries_num());
// Track whether the previous reloc was a HI16 and its previous full_immediate
bool prev_hi = false;
// Track consecutive identical HI16 relocs to handle the GNU extension to the o32 ABI.
int prev_hi_count = 0;
// Track whether the previous reloc was a LO16
bool prev_lo = false;
uint32_t prev_hi_immediate = 0;
@ -462,7 +462,7 @@ ELFIO::section* read_sections(N64Recomp::Context& context, const N64Recomp::ElfP
uint32_t rel_immediate = reloc_rom_word & 0xFFFF;
uint32_t full_immediate = (prev_hi_immediate << 16) + (int16_t)rel_immediate;
reloc_out.target_section_offset = full_immediate + rel_symbol_offset - rel_section_vram;
if (prev_hi) {
if (prev_hi_count != 0) {
if (prev_hi_symbol != rel_symbol) {
fmt::print(stderr, "Paired HI16 and LO16 relocations have different symbols\n"
" LO16 reloc index {} in section {} referencing symbol {} with offset 0x{:08X}\n",
@ -470,8 +470,12 @@ ELFIO::section* read_sections(N64Recomp::Context& context, const N64Recomp::ElfP
return nullptr;
}
// Set the previous HI16 relocs' relocated address.
section_out.relocs[i - 1].target_section_offset = reloc_out.target_section_offset;
// Set the previous HI16 relocs' relocated addresses.
for (size_t paired_index = i - prev_hi_count; paired_index < i; paired_index++) {
uint32_t hi_immediate = section_out.relocs[paired_index].target_section_offset;
uint32_t paired_full_immediate = hi_immediate + (int16_t)rel_immediate;
section_out.relocs[paired_index].target_section_offset = paired_full_immediate + rel_symbol_offset - rel_section_vram;
}
}
else {
// Orphaned LO16 reloc warnings.
@ -495,7 +499,8 @@ ELFIO::section* read_sections(N64Recomp::Context& context, const N64Recomp::ElfP
}
prev_lo = true;
} else {
if (prev_hi) {
// Allow a HI16 to follow another HI16 for the GNU ABI extension.
if (reloc_out.type != N64Recomp::RelocType::R_MIPS_HI16 && prev_hi_count != 0) {
// This is an invalid elf as the MIPS System V ABI documentation states:
// "Each relocation type of R_MIPS_HI16 must have an associated R_MIPS_LO16 entry
// immediately following it in the list of relocations."
@ -508,11 +513,26 @@ ELFIO::section* read_sections(N64Recomp::Context& context, const N64Recomp::ElfP
if (reloc_out.type == N64Recomp::RelocType::R_MIPS_HI16) {
uint32_t rel_immediate = reloc_rom_word & 0xFFFF;
prev_hi = true;
prev_hi_immediate = rel_immediate;
prev_hi_symbol = rel_symbol;
// First HI16, store its immediate.
if (prev_hi_count == 0) {
prev_hi_immediate = rel_immediate;
prev_hi_symbol = rel_symbol;
}
// HI16 that follows another HI16, ensure they reference the same symbol.
else {
if (prev_hi_symbol != rel_symbol) {
fmt::print(stderr, "HI16 reloc (index {} symbol {} offset 0x{:08X}) follows another HI16 reloc with a different symbol (index {} symbol {} offset 0x{:08X}) in section {}\n",
i, rel_symbol, section_out.relocs[i].address,
i - 1, prev_hi_symbol, section_out.relocs[i - 1].address,
section_out.name);
return nullptr;
}
}
// Populate the reloc temporarily, the full offset will be calculated upon pairing.
reloc_out.target_section_offset = rel_immediate << 16;
prev_hi_count++;
} else {
prev_hi = false;
prev_hi_count = 0;
}
if (reloc_out.type == N64Recomp::RelocType::R_MIPS_32) {