// object.cc -- support for an object file for linking in gold #include "gold.h" #include #include #include #include "object.h" #include "target-select.h" #include "layout.h" #include "output.h" namespace gold { // Class Object. const unsigned char* Object::get_view(off_t start, off_t size) { return this->input_file_->file().get_view(start + this->offset_, size); } void Object::read(off_t start, off_t size, void* p) { this->input_file_->file().read(start + this->offset_, size, p); } File_view* Object::get_lasting_view(off_t start, off_t size) { return this->input_file_->file().get_lasting_view(start + this->offset_, size); } // Class Sized_object. template Sized_object::Sized_object( const std::string& name, Input_file* input_file, off_t offset, const elfcpp::Ehdr& ehdr) : Object(name, input_file, false, offset), flags_(ehdr.get_e_flags()), shoff_(ehdr.get_e_shoff()), shstrndx_(0), symtab_shnum_(0), local_symbol_count_(0), output_local_symbol_count_(0), symbols_(NULL), local_symbol_offset_(0), values_(NULL) { if (ehdr.get_e_ehsize() != This::ehdr_size) { fprintf(stderr, _("%s: %s: bad e_ehsize field (%d != %d)\n"), program_name, this->name().c_str(), ehdr.get_e_ehsize(), This::ehdr_size); gold_exit(false); } if (ehdr.get_e_shentsize() != This::shdr_size) { fprintf(stderr, _("%s: %s: bad e_shentsize field (%d != %d)\n"), program_name, this->name().c_str(), ehdr.get_e_shentsize(), This::shdr_size); gold_exit(false); } } template Sized_object::~Sized_object() { } // Read the section header for section SHNUM. template const unsigned char* Sized_object::section_header(unsigned int shnum) { assert(shnum < this->shnum()); off_t symtabshdroff = this->shoff_ + shnum * This::shdr_size; return this->get_view(symtabshdroff, This::shdr_size); } // Set up an object file bsaed on the file header. This sets up the // target and reads the section information. template void Sized_object::setup( const elfcpp::Ehdr& ehdr) { int machine = ehdr.get_e_machine(); Target* target = select_target(machine, size, big_endian, ehdr.get_e_ident()[elfcpp::EI_OSABI], ehdr.get_e_ident()[elfcpp::EI_ABIVERSION]); if (target == NULL) { fprintf(stderr, _("%s: %s: unsupported ELF machine number %d\n"), program_name, this->name().c_str(), machine); gold_exit(false); } this->set_target(target); unsigned int shnum = ehdr.get_e_shnum(); unsigned int shstrndx = ehdr.get_e_shstrndx(); if ((shnum == 0 || shstrndx == elfcpp::SHN_XINDEX) && this->shoff_ != 0) { typename This::Shdr shdr(this->section_header(0)); if (shnum == 0) shnum = shdr.get_sh_size(); if (shstrndx == elfcpp::SHN_XINDEX) shstrndx = shdr.get_sh_link(); } this->set_shnum(shnum); this->shstrndx_ = shstrndx; if (shnum == 0) return; // Find the SHT_SYMTAB section. const unsigned char* p = this->get_view (this->shoff_, shnum * This::shdr_size); // Skip the first section, which is always empty. p += This::shdr_size; for (unsigned int i = 1; i < shnum; ++i) { typename This::Shdr shdr(p); if (shdr.get_sh_type() == elfcpp::SHT_SYMTAB) { this->symtab_shnum_ = i; break; } p += This::shdr_size; } } // Read the symbols and relocations from an object file. template Read_symbols_data Sized_object::do_read_symbols() { if (this->symtab_shnum_ == 0) { // No symbol table. Weird but legal. Read_symbols_data ret; ret.symbols = NULL; ret.symbols_size = 0; ret.symbol_names = NULL; ret.symbol_names_size = 0; return ret; } // Read the symbol table section header. typename This::Shdr symtabshdr(this->section_header(this->symtab_shnum_)); assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB); // We only need the external symbols. const int sym_size = This::sym_size; off_t locsize = symtabshdr.get_sh_info() * sym_size; off_t extoff = symtabshdr.get_sh_offset() + locsize; off_t extsize = symtabshdr.get_sh_size() - locsize; // Read the symbol table. File_view* fvsymtab = this->get_lasting_view(extoff, extsize); // Read the section header for the symbol names. unsigned int strtab_shnum = symtabshdr.get_sh_link(); if (strtab_shnum == 0 || strtab_shnum >= this->shnum()) { fprintf(stderr, _("%s: %s: invalid symbol table name index: %u\n"), program_name, this->name().c_str(), strtab_shnum); gold_exit(false); } typename This::Shdr strtabshdr(this->section_header(strtab_shnum)); if (strtabshdr.get_sh_type() != elfcpp::SHT_STRTAB) { fprintf(stderr, _("%s: %s: symbol table name section has wrong type: %u\n"), program_name, this->name().c_str(), static_cast(strtabshdr.get_sh_type())); gold_exit(false); } // Read the symbol names. File_view* fvstrtab = this->get_lasting_view(strtabshdr.get_sh_offset(), strtabshdr.get_sh_size()); Read_symbols_data ret; ret.symbols = fvsymtab; ret.symbols_size = extsize; ret.symbol_names = fvstrtab; ret.symbol_names_size = strtabshdr.get_sh_size(); return ret; } // Add the symbols to the symbol table. template void Sized_object::do_add_symbols(Symbol_table* symtab, Read_symbols_data sd) { if (sd.symbols == NULL) { assert(sd.symbol_names == NULL); return; } const int sym_size = This::sym_size; size_t symcount = sd.symbols_size / sym_size; if (symcount * sym_size != sd.symbols_size) { fprintf(stderr, _("%s: %s: size of symbols is not multiple of symbol size\n"), program_name, this->name().c_str()); gold_exit(false); } this->symbols_ = new Symbol*[symcount]; const elfcpp::Sym* syms = reinterpret_cast*>(sd.symbols->data()); const char* sym_names = reinterpret_cast(sd.symbol_names->data()); symtab->add_from_object(this, syms, symcount, sym_names, sd.symbol_names_size, this->symbols_); delete sd.symbols; delete sd.symbol_names; } // Return whether to include a section group in the link. LAYOUT is // used to keep track of which section groups we have already seen. // INDEX is the index of the section group and SHDR is the section // header. If we do not want to include this group, we set bits in // OMIT for each section which should be discarded. template bool Sized_object::include_section_group( Layout* layout, unsigned int index, const elfcpp::Shdr& shdr, std::vector* omit) { // Read the section contents. const unsigned char* pcon = this->get_view(shdr.get_sh_offset(), shdr.get_sh_size()); const elfcpp::Elf_Word* pword = reinterpret_cast(pcon); // The first word contains flags. We only care about COMDAT section // groups. Other section groups are always included in the link // just like ordinary sections. elfcpp::Elf_Word flags = elfcpp::read_elf_word(pword); if ((flags & elfcpp::GRP_COMDAT) == 0) return true; // Look up the group signature, which is the name of a symbol. This // is a lot of effort to go to to read a string. Why didn't they // just use the name of the SHT_GROUP section as the group // signature? // Get the appropriate symbol table header (this will normally be // the single SHT_SYMTAB section, but in principle it need not be). if (shdr.get_sh_link() >= this->shnum()) { fprintf(stderr, _("%s: %s: section group %u link %u out of range\n"), program_name, this->name().c_str(), index, shdr.get_sh_link()); gold_exit(false); } typename This::Shdr symshdr(this->section_header(shdr.get_sh_link())); // Read the symbol table entry. if (shdr.get_sh_info() >= symshdr.get_sh_size() / This::sym_size) { fprintf(stderr, _("%s: %s: section group %u info %u out of range\n"), program_name, this->name().c_str(), index, shdr.get_sh_info()); gold_exit(false); } off_t symoff = symshdr.get_sh_offset() + shdr.get_sh_info() * This::sym_size; const unsigned char* psym = this->get_view(symoff, This::sym_size); elfcpp::Sym sym(psym); // Read the section header for the symbol table names. if (symshdr.get_sh_link() >= this->shnum()) { fprintf(stderr, _("%s; %s: symtab section %u link %u out of range\n"), program_name, this->name().c_str(), shdr.get_sh_link(), symshdr.get_sh_link()); gold_exit(false); } typename This::Shdr symnamehdr(this->section_header(symshdr.get_sh_link())); // Read the symbol table names. const unsigned char *psymnamesu = this->get_view(symnamehdr.get_sh_offset(), symnamehdr.get_sh_size()); const char* psymnames = reinterpret_cast(psymnamesu); // Get the section group signature. if (sym.get_st_name() >= symnamehdr.get_sh_size()) { fprintf(stderr, _("%s: %s: symbol %u name offset %u out of range\n"), program_name, this->name().c_str(), shdr.get_sh_info(), sym.get_st_name()); gold_exit(false); } const char* signature = psymnames + sym.get_st_name(); // Record this section group, and see whether we've already seen one // with the same signature. if (layout->add_comdat(signature, true)) return true; // This is a duplicate. We want to discard the sections in this // group. size_t count = shdr.get_sh_size() / sizeof(elfcpp::Elf_Word); for (size_t i = 1; i < count; ++i) { elfcpp::Elf_Word secnum = elfcpp::read_elf_word(pword + i); if (secnum >= this->shnum()) { fprintf(stderr, _("%s: %s: section %u in section group %u out of range"), program_name, this->name().c_str(), secnum, index); gold_exit(false); } (*omit)[secnum] = true; } return false; } // Whether to include a linkonce section in the link. NAME is the // name of the section and SHDR is the section header. // Linkonce sections are a GNU extension implemented in the original // GNU linker before section groups were defined. The semantics are // that we only include one linkonce section with a given name. The // name of a linkonce section is normally .gnu.linkonce.T.SYMNAME, // where T is the type of section and SYMNAME is the name of a symbol. // In an attempt to make linkonce sections interact well with section // groups, we try to identify SYMNAME and use it like a section group // signature. We want to block section groups with that signature, // but not other linkonce sections with that signature. We also use // the full name of the linkonce section as a normal section group // signature. template bool Sized_object::include_linkonce_section( Layout* layout, const char* name, const elfcpp::Shdr&) { const char* symname = strrchr(name, '.') + 1; bool omit1 = layout->add_comdat(symname, false); bool omit2 = layout->add_comdat(name, true); return omit1 || omit2; } // Lay out the input sections. We walk through the sections and check // whether they should be included in the link. If they should, we // pass them to the Layout object, which will return an output section // and an offset. template void Sized_object::do_layout(Layout* layout) { // This is always called from the main thread. Lock the file to // keep the error checks happy. Task_locker_obj frl(this->input_file()->file()); // Get the section headers. unsigned int shnum = this->shnum(); const unsigned char* pshdrs = this->get_view(this->shoff_, shnum * This::shdr_size); // Get the section names. const unsigned char* pshdrnames = pshdrs + this->shstrndx_ * This::shdr_size; typename This::Shdr shdrnames(pshdrnames); typename elfcpp::Elf_types::Elf_WXword names_size = shdrnames.get_sh_size(); const unsigned char* pnamesu = this->get_view(shdrnames.get_sh_offset(), shdrnames.get_sh_size()); const char* pnames = reinterpret_cast(pnamesu); std::vector& map_sections(this->map_to_output()); map_sections.resize(shnum); // Keep track of which sections to omit. std::vector omit(shnum, false); for (unsigned int i = 0; i < shnum; ++i) { typename This::Shdr shdr(pshdrs); if (shdr.get_sh_name() >= names_size) { fprintf(stderr, _("%s: %s: bad section name offset for section %u: %lu\n"), program_name, this->name().c_str(), i, static_cast(shdr.get_sh_name())); gold_exit(false); } const char* name = pnames + shdr.get_sh_name(); bool discard = omit[i]; if (!discard) { if (shdr.get_sh_type() == elfcpp::SHT_GROUP) { if (!this->include_section_group(layout, i, shdr, &omit)) discard = true; } else if (Layout::is_linkonce(name)) { if (!this->include_linkonce_section(layout, name, shdr)) discard = true; } } if (discard) { // Do not include this section in the link. map_sections[i].output_section = NULL; continue; } off_t offset; Output_section* os = layout->layout(this, name, shdr, &offset); map_sections[i].output_section = os; map_sections[i].offset = offset; pshdrs += This::shdr_size; } } // Finalize the local symbols. Here we record the file offset at // which they should be output, we add their names to *POOL, and we // add their values to THIS->VALUES_. Return the new file offset. // This function is always called from the main thread. The actual // output of the local symbols will occur in a separate task. template off_t Sized_object::do_finalize_local_symbols(off_t off, Stringpool* pool) { if (this->symtab_shnum_ == 0) { // This object has no symbols. Weird but legal. return off; } off = (off + (size >> 3) - 1) & ~ ((off_t) (size >> 3) - 1); this->local_symbol_offset_ = off; // Read the symbol table section header. typename This::Shdr symtabshdr(this->section_header(this->symtab_shnum_)); assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB); // Read the local symbols. unsigned int loccount = symtabshdr.get_sh_info(); const int sym_size = This::sym_size; off_t locsize = loccount * sym_size; const unsigned char* psyms = this->get_view(symtabshdr.get_sh_offset(), locsize); this->local_symbol_count_ = loccount; this->values_ = new typename elfcpp::Elf_types::Elf_Addr[loccount]; // Read the section header for the symbol names. typename This::Shdr strtabshdr( this->section_header(symtabshdr.get_sh_link())); assert(strtabshdr.get_sh_type() == elfcpp::SHT_STRTAB); // Read the symbol names. const unsigned char* pnamesu = this->get_view(strtabshdr.get_sh_offset(), strtabshdr.get_sh_size()); const char* pnames = reinterpret_cast(pnamesu); // Loop over the local symbols. std::vector& mo(this->map_to_output()); unsigned int shnum = this->shnum(); unsigned int count = 0; // Skip the first, dummy, symbol. psyms += sym_size; for (unsigned int i = 1; i < loccount; ++i, psyms += sym_size) { elfcpp::Sym sym(psyms); unsigned int shndx = sym.get_st_shndx(); if (shndx >= elfcpp::SHN_LORESERVE) { if (shndx == elfcpp::SHN_ABS) this->values_[i] = sym.get_st_value(); else { // FIXME: Handle SHN_XINDEX. fprintf(stderr, _("%s: %s: unknown section index %u " "for local symbol %u\n"), program_name, this->name().c_str(), shndx, i); gold_exit(false); } } else { if (shndx >= shnum) { fprintf(stderr, _("%s: %s: local symbol %u section index %u " "out of range\n"), program_name, this->name().c_str(), i, shndx); gold_exit(false); } if (mo[shndx].output_section == NULL) { this->values_[i] = 0; continue; } this->values_[i] = (mo[shndx].output_section->address() + sym.get_st_value()); } pool->add(pnames + sym.get_st_name()); off += sym_size; ++count; } this->output_local_symbol_count_ = count; return off; } // Write out the local symbols. template void Sized_object::write_local_symbols(Output_file* of, const Stringpool* sympool) { if (this->symtab_shnum_ == 0) { // This object has no symbols. Weird but legal. return; } // Read the symbol table section header. typename This::Shdr symtabshdr(this->section_header(this->symtab_shnum_)); assert(symtabshdr.get_sh_type() == elfcpp::SHT_SYMTAB); unsigned int local_symbol_count = this->local_symbol_count_; assert(local_symbol_count == symtabshdr.get_sh_info()); // Read the local symbols. const int sym_size = This::sym_size; off_t locsize = local_symbol_count * sym_size; const unsigned char* psyms = this->get_view(symtabshdr.get_sh_offset(), locsize); // Read the section header for the symbol names. typename This::Shdr strtabshdr( this->section_header(symtabshdr.get_sh_link())); assert(strtabshdr.get_sh_type() == elfcpp::SHT_STRTAB); // Read the symbol names. const unsigned char* pnamesu = this->get_view(strtabshdr.get_sh_offset(), strtabshdr.get_sh_size()); const char* pnames = reinterpret_cast(pnamesu); // Get a view into the output file. off_t output_size = this->output_local_symbol_count_ * sym_size; unsigned char* oview = of->get_output_view(this->local_symbol_offset_, output_size); std::vector& mo(this->map_to_output()); psyms += sym_size; unsigned char* ov = oview; for (unsigned int i = 1; i < local_symbol_count; ++i, psyms += sym_size) { elfcpp::Sym isym(psyms); elfcpp::Sym_write osym(ov); unsigned int st_shndx = isym.get_st_shndx(); if (st_shndx < elfcpp::SHN_LORESERVE) { assert(st_shndx < mo.size()); if (mo[st_shndx].output_section == NULL) continue; st_shndx = mo[st_shndx].output_section->shndx(); } osym.put_st_name(sympool->get_offset(pnames + isym.get_st_name())); osym.put_st_value(this->values_[i]); osym.put_st_size(isym.get_st_size()); osym.put_st_info(isym.get_st_info()); osym.put_st_other(isym.get_st_other()); osym.put_st_shndx(st_shndx); ov += sym_size; } assert(ov - oview == output_size); of->write_output_view(this->local_symbol_offset_, output_size, oview); } // Input_objects methods. void Input_objects::add_object(Object* obj) { this->object_list_.push_back(obj); Target* target = obj->target(); if (this->target_ == NULL) this->target_ = target; else if (this->target_ != target) { fprintf(stderr, "%s: %s: incompatible target\n", program_name, obj->name().c_str()); gold_exit(false); } if (obj->is_dynamic()) this->any_dynamic_ = true; } } // End namespace gold. namespace { using namespace gold; // Read an ELF file with the header and return the appropriate // instance of Object. template Object* make_elf_sized_object(const std::string& name, Input_file* input_file, off_t offset, const elfcpp::Ehdr& ehdr) { int et = ehdr.get_e_type(); if (et != elfcpp::ET_REL && et != elfcpp::ET_DYN) { fprintf(stderr, "%s: %s: unsupported ELF type %d\n", program_name, name.c_str(), static_cast(et)); gold_exit(false); } if (et == elfcpp::ET_REL) { Sized_object* obj = new Sized_object(name, input_file, offset, ehdr); obj->setup(ehdr); return obj; } else { // elfcpp::ET_DYN fprintf(stderr, _("%s: %s: dynamic objects are not yet supported\n"), program_name, name.c_str()); gold_exit(false); // Sized_dynobj* obj = // new Sized_dynobj(this->input_.name(), input_file, // offset, ehdr); // obj->setup(ehdr); // return obj; } } } // End anonymous namespace. namespace gold { // Read an ELF file and return the appropriate instance of Object. Object* make_elf_object(const std::string& name, Input_file* input_file, off_t offset, const unsigned char* p, off_t bytes) { if (bytes < elfcpp::EI_NIDENT) { fprintf(stderr, _("%s: %s: ELF file too short\n"), program_name, name.c_str()); gold_exit(false); } int v = p[elfcpp::EI_VERSION]; if (v != elfcpp::EV_CURRENT) { if (v == elfcpp::EV_NONE) fprintf(stderr, _("%s: %s: invalid ELF version 0\n"), program_name, name.c_str()); else fprintf(stderr, _("%s: %s: unsupported ELF version %d\n"), program_name, name.c_str(), v); gold_exit(false); } int c = p[elfcpp::EI_CLASS]; if (c == elfcpp::ELFCLASSNONE) { fprintf(stderr, _("%s: %s: invalid ELF class 0\n"), program_name, name.c_str()); gold_exit(false); } else if (c != elfcpp::ELFCLASS32 && c != elfcpp::ELFCLASS64) { fprintf(stderr, _("%s: %s: unsupported ELF class %d\n"), program_name, name.c_str(), c); gold_exit(false); } int d = p[elfcpp::EI_DATA]; if (d == elfcpp::ELFDATANONE) { fprintf(stderr, _("%s: %s: invalid ELF data encoding\n"), program_name, name.c_str()); gold_exit(false); } else if (d != elfcpp::ELFDATA2LSB && d != elfcpp::ELFDATA2MSB) { fprintf(stderr, _("%s: %s: unsupported ELF data encoding %d\n"), program_name, name.c_str(), d); gold_exit(false); } bool big_endian = d == elfcpp::ELFDATA2MSB; if (c == elfcpp::ELFCLASS32) { if (bytes < elfcpp::Elf_sizes<32>::ehdr_size) { fprintf(stderr, _("%s: %s: ELF file too short\n"), program_name, name.c_str()); gold_exit(false); } if (big_endian) { elfcpp::Ehdr<32, true> ehdr(p); return make_elf_sized_object<32, true>(name, input_file, offset, ehdr); } else { elfcpp::Ehdr<32, false> ehdr(p); return make_elf_sized_object<32, false>(name, input_file, offset, ehdr); } } else { if (bytes < elfcpp::Elf_sizes<32>::ehdr_size) { fprintf(stderr, _("%s: %s: ELF file too short\n"), program_name, name.c_str()); gold_exit(false); } if (big_endian) { elfcpp::Ehdr<64, true> ehdr(p); return make_elf_sized_object<64, true>(name, input_file, offset, ehdr); } else { elfcpp::Ehdr<64, false> ehdr(p); return make_elf_sized_object<64, false>(name, input_file, offset, ehdr); } } } // Instantiate the templates we need. We could use the configure // script to restrict this to only the ones for implemented targets. template class Sized_object<32, false>; template class Sized_object<32, true>; template class Sized_object<64, false>; template class Sized_object<64, true>; } // End namespace gold.