mirror of
https://github.com/rui314/mold.git
synced 2024-11-11 16:58:12 +03:00
466 lines
13 KiB
C++
466 lines
13 KiB
C++
#include "mold.h"
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#include "llvm/BinaryFormat/Magic.h"
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using namespace llvm;
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using namespace llvm::ELF;
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ObjectFile::ObjectFile(MemoryBufferRef mb, StringRef archive_name)
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: mb(mb), name(mb.getBufferIdentifier()), archive_name(archive_name),
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obj(check(ELFFile<ELF64LE>::create(mb.getBuffer()))) {}
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static const ELF64LE::Shdr
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*findSection(ArrayRef<ELF64LE::Shdr> sections, u32 type) {
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for (const ELF64LE::Shdr &sec : sections)
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if (sec.sh_type == type)
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return &sec;
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return nullptr;
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}
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void ObjectFile::initialize_sections() {
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StringRef section_strtab = CHECK(obj.getSectionStringTable(elf_sections), this);
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sections.resize(elf_sections.size());
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for (int i = 0; i < elf_sections.size(); i++) {
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const ELF64LE::Shdr &shdr = elf_sections[i];
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if ((shdr.sh_flags & SHF_EXCLUDE) && !(shdr.sh_flags & SHF_ALLOC))
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continue;
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switch (shdr.sh_type) {
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case SHT_GROUP: {
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// Get the signature of this section group.
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if (shdr.sh_info >= elf_syms.size())
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error(toString(this) + ": invalid symbol index");
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const ELF64LE::Sym &sym = elf_syms[shdr.sh_info];
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StringRef signature = CHECK(sym.getName(symbol_strtab), this);
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// Get comdat group members.
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ArrayRef<ELF64LE::Word> entries =
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CHECK(obj.template getSectionContentsAsArray<ELF64LE::Word>(shdr), this);
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if (entries.empty())
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error(toString(this) + ": empty SHT_GROUP");
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if (entries[0] == 0)
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continue;
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if (entries[0] != GRP_COMDAT)
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error(toString(this) + ": unsupported SHT_GROUP format");
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static ConcurrentMap<ComdatGroup> map;
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ComdatGroup *group = map.insert(signature, ComdatGroup(nullptr, 0));
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comdat_groups.push_back({group, i});
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static Counter counter("comdats");
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counter.inc();
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break;
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}
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case SHT_SYMTAB_SHNDX:
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error(toString(this) + ": SHT_SYMTAB_SHNDX section is not supported");
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break;
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case SHT_SYMTAB:
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case SHT_STRTAB:
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case SHT_REL:
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case SHT_RELA:
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case SHT_NULL:
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break;
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default: {
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static Counter counter("regular_sections");
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counter.inc();
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#if 0
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if ((shdr.sh_flags & SHF_STRINGS) && !(shdr.sh_flags & SHF_WRITE) &&
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shdr.sh_entsize == 1) {
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read_string_pieces(shdr);
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break;
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}
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#endif
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StringRef name = CHECK(obj.getSectionName(shdr, section_strtab), this);
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this->sections[i] = new InputSection(this, shdr, name);
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break;
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}
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}
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}
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for (const ELF64LE::Shdr &shdr : elf_sections) {
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if (shdr.sh_type != SHT_RELA)
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continue;
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if (shdr.sh_info >= sections.size())
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error(toString(this) + ": invalid relocated section index: " +
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Twine(shdr.sh_info));
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InputSection *target = sections[shdr.sh_info];
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if (target) {
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target->rels = CHECK(obj.relas(shdr), this);
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if (target->shdr.sh_flags & SHF_ALLOC) {
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static Counter counter("relocs_alloc");
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counter.inc(target->rels.size());
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}
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}
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}
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}
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void ObjectFile::initialize_symbols() {
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static Counter counter("all_syms");
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counter.inc(elf_syms.size());
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symbols.reserve(elf_syms.size());
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local_symbols.reserve(first_global);
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// First symbol entry is always null
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local_symbols.emplace_back("");
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symbols.push_back(&local_symbols.back());
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for (int i = 1; i < first_global; i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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StringRef name = CHECK(esym.getName(symbol_strtab), this);
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local_symbols.emplace_back(name);
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Symbol &sym = local_symbols.back();
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sym.file = this;
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sym.type = esym.getType();
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sym.addr = esym.st_value;
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if (!esym.isAbsolute()) {
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if (esym.isCommon())
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error("common local symbol?");
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sym.input_section = sections[esym.st_shndx];
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}
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symbols.push_back(&local_symbols.back());
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if (esym.getType() != STT_SECTION) {
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local_strtab_size += name.size() + 1;
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local_symtab_size += sizeof(ELF64LE::Sym);
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}
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}
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for (int i = first_global; i < elf_syms.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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StringRef name = CHECK(esym.getName(symbol_strtab), this);
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symbols.push_back(Symbol::intern(name));
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if (esym.isCommon())
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has_common_symbol = true;
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}
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}
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void ObjectFile::remove_comdat_members(u32 section_idx) {
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const ELF64LE::Shdr &shdr = elf_sections[section_idx];
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ArrayRef<ELF64LE::Word> entries =
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CHECK(obj.template getSectionContentsAsArray<ELF64LE::Word>(shdr), this);
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for (u32 i : entries)
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sections[i] = nullptr;
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}
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void ObjectFile::read_string_pieces(const ELF64LE::Shdr &shdr) {
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static ConcurrentMap<StringPiece> map1;
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static ConcurrentMap<StringPiece> map2;
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bool is_alloc = shdr.sh_type & SHF_ALLOC;
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ConcurrentMap<StringPiece> &map = is_alloc ? map1 : map2;
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ArrayRef<u8> arr = CHECK(obj.getSectionContents(shdr), this);
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StringRef data((const char *)&arr[0], arr.size());
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while (!data.empty()) {
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size_t end = data.find('\0');
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if (end == StringRef::npos)
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error(toString(this) + ": string is not null terminated");
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StringRef substr = data.substr(0, end + 1);
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StringPiece *piece = map.insert(substr, StringPiece(substr));
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if (is_alloc)
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merged_strings_alloc.push_back(piece);
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else
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merged_strings_noalloc.push_back(piece);
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data = data.substr(end + 1);
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// num_string_pieces++;
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}
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}
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void ObjectFile::parse() {
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is_dso = (identify_magic(mb.getBuffer()) == file_magic::elf_shared_object);
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elf_sections = CHECK(obj.sections(), this);
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symtab_sec = findSection(elf_sections, is_dso ? SHT_DYNSYM : SHT_SYMTAB);
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if (symtab_sec) {
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first_global = symtab_sec->sh_info;
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elf_syms = CHECK(obj.symbols(symtab_sec), this);
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symbol_strtab = CHECK(obj.getStringTableForSymtab(*symtab_sec, elf_sections), this);
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}
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initialize_sections();
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if (symtab_sec)
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initialize_symbols();
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}
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void ObjectFile::register_defined_symbols() {
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for (int i = first_global; i < symbols.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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Symbol &sym = *symbols[i];
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if (esym.isDefined()) {
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static Counter counter("defined_syms");
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counter.inc();
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InputSection *isec = nullptr;
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if (!esym.isAbsolute() && !esym.isCommon())
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isec = sections[esym.st_shndx];
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bool is_weak = (esym.getBinding() == STB_WEAK);
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std::lock_guard lock(sym.mu);
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bool is_new = !sym.file;
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bool win = sym.is_weak && !is_weak;
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bool tie_but_higher_priority =
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!is_new && !win && this->priority < sym.file->priority;
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if (is_new || win || tie_but_higher_priority) {
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sym.file = this;
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sym.input_section = isec;
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sym.addr = esym.st_value;
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sym.type = esym.getType();
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sym.visibility = esym.getVisibility();
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sym.is_weak = is_weak;
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}
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}
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}
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}
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void
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ObjectFile::register_undefined_symbols(tbb::parallel_do_feeder<ObjectFile *> &feeder) {
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if (is_alive.exchange(true))
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return;
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for (int i = first_global; i < symbols.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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Symbol &sym = *symbols[i];
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if (esym.isUndefined() && esym.getBinding() != STB_WEAK &&
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sym.file && sym.file->is_in_archive() && !sym.file->is_alive) {
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static Counter counter("undefined_syms");
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counter.inc();
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#if 0
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llvm::outs() << toString(this) << " loads " << toString(sym.file)
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<< " for " << sym.name << "\n";
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#endif
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feeder.add(sym.file);
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}
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}
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}
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void ObjectFile::hanlde_undefined_weak_symbols() {
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if (!is_alive)
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return;
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for (int i = first_global; i < symbols.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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Symbol &sym = *symbols[i];
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if (esym.isUndefined() && esym.getBinding() == STB_WEAK) {
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std::lock_guard lock(sym.mu);
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bool is_new = !sym.file || !sym.file->is_alive;
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bool tie_but_higher_priority =
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!is_new && sym.is_undef_weak && this->priority < sym.file->priority;
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if (is_new || tie_but_higher_priority) {
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sym.file = this;
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sym.input_section = nullptr;
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sym.addr = 0;
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sym.visibility = esym.getVisibility();
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sym.is_undef_weak = true;
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}
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}
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}
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}
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void ObjectFile::eliminate_duplicate_comdat_groups() {
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for (auto &pair : comdat_groups) {
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ComdatGroup *g = pair.first;
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u32 section_idx = pair.second;
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ObjectFile *other = g->file;
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if (other && other->priority < this->priority) {
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this->remove_comdat_members(section_idx);
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continue;
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}
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ObjectFile *file;
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u32 idx;
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{
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std::lock_guard lock(g->mu);
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if (g->file == nullptr) {
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g->file = this;
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g->section_idx = section_idx;
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continue;
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}
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if (g->file.load()->priority < this->priority) {
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file = this;
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idx = section_idx;
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} else {
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file = g->file;
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idx = g->section_idx;
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g->file = this;
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g->section_idx = section_idx;
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}
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}
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file->remove_comdat_members(idx);
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}
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}
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void ObjectFile::convert_common_symbols() {
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if (!has_common_symbol)
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return;
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static OutputSection *bss =
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OutputSection::get_instance(".bss", SHF_WRITE | SHF_ALLOC, SHT_NOBITS);
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for (int i = first_global; i < elf_syms.size(); i++) {
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if (!elf_syms[i].isCommon())
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continue;
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Symbol *sym = symbols[i];
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if (sym->file != this)
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continue;
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auto *shdr = new ELF64LE::Shdr;
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memset(shdr, 0, sizeof(*shdr));
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shdr->sh_flags = SHF_ALLOC;
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shdr->sh_type = SHT_NOBITS;
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shdr->sh_size = elf_syms[i].st_size;
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shdr->sh_addralign = 1;
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auto *isec = new InputSection(this, *shdr, ".bss");
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isec->output_section = bss;
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sections.push_back(isec);
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sym->input_section = isec;
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sym->addr = 0;
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}
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}
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void ObjectFile::fix_sym_addrs() {
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for (Symbol *sym : symbols) {
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if (sym->file != this)
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continue;
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if (InputSection *isec = sym->input_section) {
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OutputSection *osec = isec->output_section;
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sym->addr += osec->shdr.sh_addr + isec->offset;
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}
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}
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}
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void ObjectFile::compute_symtab() {
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for (int i = first_global; i < elf_syms.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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Symbol &sym = *symbols[i];
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if (esym.getType() != STT_SECTION && sym.file == this) {
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global_strtab_size += sym.name.size() + 1;
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global_symtab_size += sizeof(ELF64LE::Sym);
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}
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}
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}
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void ObjectFile::write_symtab(u8 *buf, u64 symtab_off, u64 strtab_off,
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u32 start, u32 end) {
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u8 *symtab = buf + out::symtab->shdr.sh_offset;
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u8 *strtab = buf + out::strtab->shdr.sh_offset;
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if (this->name == "<internal>")
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llvm::outs() << start << " " << end << "\n";
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for (int i = start; i < end; i++) {
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Symbol &sym = *symbols[i];
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if (sym.type == STT_SECTION || sym.file != this)
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continue;
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auto &esym = *(ELF64LE::Sym *)(symtab + symtab_off);
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esym.st_name = strtab_off;
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esym.st_value = sym.addr;
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esym.st_size = elf_syms[i].st_size;
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esym.st_info = elf_syms[i].st_info;
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esym.st_shndx = sym.input_section
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? sym.input_section->output_section->idx : SHN_ABS;
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symtab_off += sizeof(ELF64LE::Sym);
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memcpy(strtab + strtab_off, sym.name.data(), sym.name.size());
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strtab_off += sym.name.size() + 1;
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}
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}
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void ObjectFile::write_local_symtab(u8 *buf, u64 symtab_off, u64 strtab_off) {
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write_symtab(buf, symtab_off, strtab_off, 1, first_global);
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}
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void ObjectFile::write_global_symtab(u8 *buf, u64 symtab_off, u64 strtab_off) {
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write_symtab(buf, symtab_off, strtab_off, first_global, elf_syms.size());
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}
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bool ObjectFile::is_in_archive() {
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return !archive_name.empty();
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}
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ObjectFile *ObjectFile::create_internal_file() {
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// Create a dummy object file.
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constexpr int bufsz = 256;
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char *buf = new char[bufsz];
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std::unique_ptr<MemoryBuffer> mb =
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MemoryBuffer::getMemBuffer(StringRef(buf, bufsz));
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auto *obj = new ObjectFile(mb->getMemBufferRef(), "");
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obj->name = "<internal>";
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mb.release();
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// Create linker-synthesized symbols.
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auto *elf_syms = new std::vector<ELF64LE::Sym>(1);
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obj->symbols.push_back(new Symbol(""));
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obj->first_global = 1;
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auto add = [&](StringRef name, u8 binding) {
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Symbol *sym = Symbol::intern(name);
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sym->file = obj;
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obj->symbols.push_back(sym);
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ELF64LE::Sym esym = {};
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esym.setType(STT_NOTYPE);
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esym.setBinding(binding);
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elf_syms->push_back(esym);
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return sym;
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};
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out::__bss_start = add("__bss_start", STB_GLOBAL);
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out::__ehdr_start = add("__ehdr_start", STB_LOCAL);
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out::__rela_iplt_start = add("__rela_iplt_start", STB_LOCAL);
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out::__rela_iplt_end = add("__rela_iplt_end", STB_LOCAL);
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out::__init_array_start = add("__init_array_start", STB_LOCAL);
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out::__init_array_end = add("__init_array_end", STB_LOCAL);
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out::__fini_array_start = add("__fini_array_start", STB_LOCAL);
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out::__fini_array_end = add("__fini_array_end", STB_LOCAL);
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out::__preinit_array_start = add("__preinit_array_start", STB_LOCAL);
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out::__preinit_array_end = add("__preinit_array_end", STB_LOCAL);
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obj->elf_syms = *elf_syms;
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return obj;
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}
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std::string toString(ObjectFile *obj) {
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StringRef s = obj->name;
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if (obj->archive_name == "")
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return s.str();
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return (obj->archive_name + ":" + s).str();
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}
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