mirror of
https://github.com/rui314/mold.git
synced 2024-09-22 18:40:59 +03:00
414 lines
11 KiB
C++
414 lines
11 KiB
C++
#include "mold.h"
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using namespace llvm;
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using namespace llvm::ELF;
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std::atomic_int num_defined;
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std::atomic_int num_undefined;
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std::atomic_int num_all_syms;
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std::atomic_int num_comdats;
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std::atomic_int num_regular_sections;
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std::atomic_int num_files;
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std::atomic_int num_relocs_alloc;
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std::atomic_int num_string_pieces;
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ObjectFile::ObjectFile(MemoryBufferRef mb, StringRef archive_name)
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: mb(mb), archive_name(archive_name),
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obj(check(ELFFile<ELF64LE>::create(mb.getBuffer()))) {}
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MemoryBufferRef readFile(StringRef path) {
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auto mbOrErr = MemoryBuffer::getFile(path, -1, false);
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if (auto ec = mbOrErr.getError())
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error("cannot open " + path + ": " + ec.message());
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std::unique_ptr<MemoryBuffer> &mb = *mbOrErr;
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MemoryBufferRef mbref = mb->getMemBufferRef();
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mb.release();
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return mbref;
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}
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static const ELF64LE::Shdr
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*findSection(ArrayRef<ELF64LE::Shdr> sections, uint32_t 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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// num_comdats++;
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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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// num_regular_sections++;
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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 (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_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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// num_relocs_alloc += target->rels.size();
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}
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}
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}
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void ObjectFile::initialize_symbols() {
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local_symbols.reserve(first_global);
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for (int i = 0; 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.push_back(name);
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local_strtab_size += name.size() + 1;
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}
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symbols.reserve(elf_syms.size() - first_global);
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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.st_shndx == SHN_COMMON)
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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(uint32_t 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 (uint32_t 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<uint8_t> 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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num_files++;
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bool 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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// num_all_syms += elf_syms.size();
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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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class Spinlock {
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public:
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Spinlock(std::atomic_flag &lock) : lock(lock) {
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while (lock.test_and_set(std::memory_order_acquire));
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}
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~Spinlock() {
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lock.clear(std::memory_order_release);
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}
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private:
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std::atomic_flag &lock;
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};
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void ObjectFile::register_defined_symbols() {
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for (int i = 0; i < symbols.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[first_global + i];
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Symbol &sym = *symbols[i];
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if (!esym.isDefined())
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continue;
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// num_defined++;
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InputSection *isec = nullptr;
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uint32_t shndx = esym.st_shndx;
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if (shndx != SHN_ABS && shndx != SHN_COMMON)
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isec = sections[shndx];
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bool is_weak = (esym.getBinding() == STB_WEAK);
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Spinlock lock(sym.lock);
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if (!sym.file || this->priority < sym.file->priority ||
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(sym.is_weak && !is_weak)) {
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sym.file = this;
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sym.input_section = isec;
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sym.value = esym.st_value;
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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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void ObjectFile::register_undefined_symbols() {
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if (is_alive.exchange(true))
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return;
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for (int i = 0; i < symbols.size(); i++) {
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const ELF64LE::Sym &esym = elf_syms[first_global + i];
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Symbol &sym = *symbols[i];
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if (esym.isDefined())
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continue;
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// num_undefined++;
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if (sym.file && sym.file->is_in_archive() && !sym.file->is_alive)
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sym.file->register_undefined_symbols();
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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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uint32_t 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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uint32_t idx;
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{
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Spinlock lock(g->lock);
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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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static OutputSection bss(".bss", SHF_ALLOC, SHT_NOBITS);
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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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for (int i = first_global; i < elf_syms.size(); i++) {
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if (elf_syms[i].st_shndx != SHN_COMMON)
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continue;
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Symbol *sym = symbols[i - first_global];
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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_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->value = 0;
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}
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}
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void ObjectFile::scan_relocations() {
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for (InputSection *isec : sections)
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if (isec)
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isec->scan_relocations();
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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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InputSection *isec = sym->input_section;
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if (isec) {
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OutputSection *osec = isec->output_section;
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sym->addr = osec->shdr.sh_addr + isec->offset + sym->value;
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} else {
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// Absolute symbol
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sym->addr = sym->value;
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}
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}
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}
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void ObjectFile::compute_symtab() {
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local_symtab_size = sizeof(ELF64LE::Sym) * first_global;
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for (Symbol *sym : symbols) {
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if (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
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ObjectFile::write_local_symtab(uint8_t *buf, uint64_t symtab_off, uint64_t strtab_off) {
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uint8_t *symtab = buf + out::symtab->shdr.sh_offset;
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uint8_t *strtab = buf + out::strtab->shdr.sh_offset;
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for (int i = 0; i < first_global; i++) {
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const ELF64LE::Sym &esym = elf_syms[i];
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StringRef name = local_symbols[i];
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auto *ent = (ELF64LE::Sym *)(symtab + symtab_off);
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*ent = esym;
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ent->st_shndx = out::strtab->idx;
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ent->st_name = strtab_off;
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ent->st_value = get_symbol_value(i);
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symtab_off += sizeof(ELF64LE::Sym);
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memcpy(strtab + strtab_off, name.data(), name.size());
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strtab_off += name.size() + 1;
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}
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}
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void
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ObjectFile::write_global_symtab(uint8_t *buf, uint64_t symtab_off, uint64_t strtab_off) {
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uint8_t *symtab = buf + out::symtab->shdr.sh_offset;
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uint8_t *strtab = buf + out::strtab->shdr.sh_offset;
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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 - first_global];
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if (sym.file != this)
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continue;
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auto *ent = (ELF64LE::Sym *)(symtab + symtab_off);
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*ent = esym;
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ent->st_shndx = out::strtab->idx;
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ent->st_name = strtab_off;
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ent->st_value = sym.value;
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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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StringRef ObjectFile::get_filename() {
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return mb.getBufferIdentifier();
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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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std::string toString(ObjectFile *obj) {
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StringRef s = obj->get_filename();
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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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