| // layout.cc -- lay out output file sections for gold |
| |
| #include "gold.h" |
| |
| #include <cassert> |
| #include <cstring> |
| #include <algorithm> |
| #include <iostream> |
| #include <utility> |
| |
| #include "output.h" |
| #include "symtab.h" |
| #include "layout.h" |
| |
| namespace gold |
| { |
| |
| // Layout_task_runner methods. |
| |
| // Lay out the sections. This is called after all the input objects |
| // have been read. |
| |
| void |
| Layout_task_runner::run(Workqueue* workqueue) |
| { |
| off_t file_size = this->layout_->finalize(this->input_objects_, |
| this->symtab_); |
| |
| // Now we know the final size of the output file and we know where |
| // each piece of information goes. |
| Output_file* of = new Output_file(this->options_); |
| of->open(file_size); |
| |
| // Queue up the final set of tasks. |
| gold::queue_final_tasks(this->options_, this->input_objects_, |
| this->symtab_, this->layout_, workqueue, of); |
| } |
| |
| // Layout methods. |
| |
| Layout::Layout(const General_options& options) |
| : options_(options), namepool_(), sympool_(), signatures_(), |
| section_name_map_(), segment_list_(), section_list_(), |
| special_output_list_(), tls_segment_(NULL) |
| { |
| // Make space for more than enough segments for a typical file. |
| // This is just for efficiency--it's OK if we wind up needing more. |
| segment_list_.reserve(12); |
| } |
| |
| // Hash a key we use to look up an output section mapping. |
| |
| size_t |
| Layout::Hash_key::operator()(const Layout::Key& k) const |
| { |
| return k.first + k.second.first + k.second.second; |
| } |
| |
| // Whether to include this section in the link. |
| |
| template<int size, bool big_endian> |
| bool |
| Layout::include_section(Object*, const char*, |
| const elfcpp::Shdr<size, big_endian>& shdr) |
| { |
| // Some section types are never linked. Some are only linked when |
| // doing a relocateable link. |
| switch (shdr.get_sh_type()) |
| { |
| case elfcpp::SHT_NULL: |
| case elfcpp::SHT_SYMTAB: |
| case elfcpp::SHT_DYNSYM: |
| case elfcpp::SHT_STRTAB: |
| case elfcpp::SHT_HASH: |
| case elfcpp::SHT_DYNAMIC: |
| case elfcpp::SHT_SYMTAB_SHNDX: |
| return false; |
| |
| case elfcpp::SHT_RELA: |
| case elfcpp::SHT_REL: |
| case elfcpp::SHT_GROUP: |
| return this->options_.is_relocatable(); |
| |
| default: |
| // FIXME: Handle stripping debug sections here. |
| return true; |
| } |
| } |
| |
| // Return an output section named NAME, or NULL if there is none. |
| |
| Output_section* |
| Layout::find_output_section(const char* name) const |
| { |
| for (Section_name_map::const_iterator p = this->section_name_map_.begin(); |
| p != this->section_name_map_.end(); |
| ++p) |
| if (strcmp(p->second->name(), name) == 0) |
| return p->second; |
| return NULL; |
| } |
| |
| // Return an output segment of type TYPE, with segment flags SET set |
| // and segment flags CLEAR clear. Return NULL if there is none. |
| |
| Output_segment* |
| Layout::find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set, |
| elfcpp::Elf_Word clear) const |
| { |
| for (Segment_list::const_iterator p = this->segment_list_.begin(); |
| p != this->segment_list_.end(); |
| ++p) |
| if (static_cast<elfcpp::PT>((*p)->type()) == type |
| && ((*p)->flags() & set) == set |
| && ((*p)->flags() & clear) == 0) |
| return *p; |
| return NULL; |
| } |
| |
| // Return the output section to use for section NAME with type TYPE |
| // and section flags FLAGS. |
| |
| Output_section* |
| Layout::get_output_section(const char* name, Stringpool::Key name_key, |
| elfcpp::Elf_Word type, elfcpp::Elf_Xword flags) |
| { |
| // We should ignore some flags. |
| flags &= ~ (elfcpp::SHF_INFO_LINK |
| | elfcpp::SHF_LINK_ORDER |
| | elfcpp::SHF_GROUP); |
| |
| const Key key(name_key, std::make_pair(type, flags)); |
| const std::pair<Key, Output_section*> v(key, NULL); |
| std::pair<Section_name_map::iterator, bool> ins( |
| this->section_name_map_.insert(v)); |
| |
| if (!ins.second) |
| return ins.first->second; |
| else |
| { |
| // This is the first time we've seen this name/type/flags |
| // combination. |
| Output_section* os = this->make_output_section(name, type, flags); |
| ins.first->second = os; |
| return os; |
| } |
| } |
| |
| // Return the output section to use for input section SHNDX, with name |
| // NAME, with header HEADER, from object OBJECT. Set *OFF to the |
| // offset of this input section without the output section. |
| |
| template<int size, bool big_endian> |
| Output_section* |
| Layout::layout(Relobj* object, unsigned int shndx, const char* name, |
| const elfcpp::Shdr<size, big_endian>& shdr, off_t* off) |
| { |
| if (!this->include_section(object, name, shdr)) |
| return NULL; |
| |
| // If we are not doing a relocateable link, choose the name to use |
| // for the output section. |
| size_t len = strlen(name); |
| if (!this->options_.is_relocatable()) |
| name = Layout::output_section_name(name, &len); |
| |
| // FIXME: Handle SHF_OS_NONCONFORMING here. |
| |
| // Canonicalize the section name. |
| Stringpool::Key name_key; |
| name = this->namepool_.add(name, len, &name_key); |
| |
| // Find the output section. The output section is selected based on |
| // the section name, type, and flags. |
| Output_section* os = this->get_output_section(name, name_key, |
| shdr.get_sh_type(), |
| shdr.get_sh_flags()); |
| |
| // FIXME: Handle SHF_LINK_ORDER somewhere. |
| |
| *off = os->add_input_section(object, shndx, name, shdr); |
| |
| return os; |
| } |
| |
| // Add POSD to an output section using NAME, TYPE, and FLAGS. |
| |
| void |
| Layout::add_output_section_data(const char* name, elfcpp::Elf_Word type, |
| elfcpp::Elf_Xword flags, |
| Output_section_data* posd) |
| { |
| // Canonicalize the name. |
| Stringpool::Key name_key; |
| name = this->namepool_.add(name, &name_key); |
| |
| Output_section* os = this->get_output_section(name, name_key, type, flags); |
| os->add_output_section_data(posd); |
| } |
| |
| // Map section flags to segment flags. |
| |
| elfcpp::Elf_Word |
| Layout::section_flags_to_segment(elfcpp::Elf_Xword flags) |
| { |
| elfcpp::Elf_Word ret = elfcpp::PF_R; |
| if ((flags & elfcpp::SHF_WRITE) != 0) |
| ret |= elfcpp::PF_W; |
| if ((flags & elfcpp::SHF_EXECINSTR) != 0) |
| ret |= elfcpp::PF_X; |
| return ret; |
| } |
| |
| // Make a new Output_section, and attach it to segments as |
| // appropriate. |
| |
| Output_section* |
| Layout::make_output_section(const char* name, elfcpp::Elf_Word type, |
| elfcpp::Elf_Xword flags) |
| { |
| Output_section* os = new Output_section(name, type, flags, true); |
| |
| if ((flags & elfcpp::SHF_ALLOC) == 0) |
| this->section_list_.push_back(os); |
| else |
| { |
| // This output section goes into a PT_LOAD segment. |
| |
| elfcpp::Elf_Word seg_flags = Layout::section_flags_to_segment(flags); |
| |
| // The only thing we really care about for PT_LOAD segments is |
| // whether or not they are writable, so that is how we search |
| // for them. People who need segments sorted on some other |
| // basis will have to wait until we implement a mechanism for |
| // them to describe the segments they want. |
| |
| Segment_list::const_iterator p; |
| for (p = this->segment_list_.begin(); |
| p != this->segment_list_.end(); |
| ++p) |
| { |
| if ((*p)->type() == elfcpp::PT_LOAD |
| && ((*p)->flags() & elfcpp::PF_W) == (seg_flags & elfcpp::PF_W)) |
| { |
| (*p)->add_output_section(os, seg_flags); |
| break; |
| } |
| } |
| |
| if (p == this->segment_list_.end()) |
| { |
| Output_segment* oseg = new Output_segment(elfcpp::PT_LOAD, |
| seg_flags); |
| this->segment_list_.push_back(oseg); |
| oseg->add_output_section(os, seg_flags); |
| } |
| |
| // If we see a loadable SHT_NOTE section, we create a PT_NOTE |
| // segment. |
| if (type == elfcpp::SHT_NOTE) |
| { |
| // See if we already have an equivalent PT_NOTE segment. |
| for (p = this->segment_list_.begin(); |
| p != segment_list_.end(); |
| ++p) |
| { |
| if ((*p)->type() == elfcpp::PT_NOTE |
| && (((*p)->flags() & elfcpp::PF_W) |
| == (seg_flags & elfcpp::PF_W))) |
| { |
| (*p)->add_output_section(os, seg_flags); |
| break; |
| } |
| } |
| |
| if (p == this->segment_list_.end()) |
| { |
| Output_segment* oseg = new Output_segment(elfcpp::PT_NOTE, |
| seg_flags); |
| this->segment_list_.push_back(oseg); |
| oseg->add_output_section(os, seg_flags); |
| } |
| } |
| |
| // If we see a loadable SHF_TLS section, we create a PT_TLS |
| // segment. There can only be one such segment. |
| if ((flags & elfcpp::SHF_TLS) != 0) |
| { |
| if (this->tls_segment_ == NULL) |
| { |
| this->tls_segment_ = new Output_segment(elfcpp::PT_TLS, |
| seg_flags); |
| this->segment_list_.push_back(this->tls_segment_); |
| } |
| this->tls_segment_->add_output_section(os, seg_flags); |
| } |
| } |
| |
| return os; |
| } |
| |
| // Find the first read-only PT_LOAD segment, creating one if |
| // necessary. |
| |
| Output_segment* |
| Layout::find_first_load_seg() |
| { |
| for (Segment_list::const_iterator p = this->segment_list_.begin(); |
| p != this->segment_list_.end(); |
| ++p) |
| { |
| if ((*p)->type() == elfcpp::PT_LOAD |
| && ((*p)->flags() & elfcpp::PF_R) != 0 |
| && ((*p)->flags() & elfcpp::PF_W) == 0) |
| return *p; |
| } |
| |
| Output_segment* load_seg = new Output_segment(elfcpp::PT_LOAD, elfcpp::PF_R); |
| this->segment_list_.push_back(load_seg); |
| return load_seg; |
| } |
| |
| // Finalize the layout. When this is called, we have created all the |
| // output sections and all the output segments which are based on |
| // input sections. We have several things to do, and we have to do |
| // them in the right order, so that we get the right results correctly |
| // and efficiently. |
| |
| // 1) Finalize the list of output segments and create the segment |
| // table header. |
| |
| // 2) Finalize the dynamic symbol table and associated sections. |
| |
| // 3) Determine the final file offset of all the output segments. |
| |
| // 4) Determine the final file offset of all the SHF_ALLOC output |
| // sections. |
| |
| // 5) Create the symbol table sections and the section name table |
| // section. |
| |
| // 6) Finalize the symbol table: set symbol values to their final |
| // value and make a final determination of which symbols are going |
| // into the output symbol table. |
| |
| // 7) Create the section table header. |
| |
| // 8) Determine the final file offset of all the output sections which |
| // are not SHF_ALLOC, including the section table header. |
| |
| // 9) Finalize the ELF file header. |
| |
| // This function returns the size of the output file. |
| |
| off_t |
| Layout::finalize(const Input_objects* input_objects, Symbol_table* symtab) |
| { |
| const int size = input_objects->target()->get_size(); |
| |
| Output_segment* phdr_seg = NULL; |
| if (input_objects->any_dynamic()) |
| { |
| // There was a dynamic object in the link. We need to create |
| // some information for the dynamic linker. |
| |
| // Create the PT_PHDR segment which will hold the program |
| // headers. |
| phdr_seg = new Output_segment(elfcpp::PT_PHDR, elfcpp::PF_R); |
| this->segment_list_.push_back(phdr_seg); |
| |
| // Create the dynamic symbol table, including the hash table, |
| // the dynamic relocations, and the version sections. |
| this->create_dynamic_symtab(size, symtab); |
| |
| // Create the .dynamic section to hold the dynamic data, and put |
| // it in a PT_DYNAMIC segment. |
| this->create_dynamic_section(); |
| |
| // Create the .interp section to hold the name of the |
| // interpreter, and put it in a PT_INTERP segment. |
| this->create_interp(input_objects->target()); |
| } |
| |
| // FIXME: Handle PT_GNU_STACK. |
| |
| Output_segment* load_seg = this->find_first_load_seg(); |
| |
| // Lay out the segment headers. |
| bool big_endian = input_objects->target()->is_big_endian(); |
| Output_segment_headers* segment_headers; |
| segment_headers = new Output_segment_headers(size, big_endian, |
| this->segment_list_); |
| load_seg->add_initial_output_data(segment_headers); |
| this->special_output_list_.push_back(segment_headers); |
| if (phdr_seg != NULL) |
| phdr_seg->add_initial_output_data(segment_headers); |
| |
| // Lay out the file header. |
| Output_file_header* file_header; |
| file_header = new Output_file_header(size, |
| big_endian, |
| this->options_, |
| input_objects->target(), |
| symtab, |
| segment_headers); |
| load_seg->add_initial_output_data(file_header); |
| this->special_output_list_.push_back(file_header); |
| |
| // We set the output section indexes in set_segment_offsets and |
| // set_section_offsets. |
| unsigned int shndx = 1; |
| |
| // Set the file offsets of all the segments, and all the sections |
| // they contain. |
| off_t off = this->set_segment_offsets(input_objects->target(), load_seg, |
| &shndx); |
| |
| // Create the symbol table sections. |
| // FIXME: We don't need to do this if we are stripping symbols. |
| Output_section* osymtab; |
| Output_section* ostrtab; |
| this->create_symtab_sections(size, input_objects, symtab, &off, |
| &osymtab, &ostrtab); |
| |
| // Create the .shstrtab section. |
| Output_section* shstrtab_section = this->create_shstrtab(); |
| |
| // Set the file offsets of all the sections not associated with |
| // segments. |
| off = this->set_section_offsets(off, &shndx); |
| |
| // Now the section index of OSTRTAB is set. |
| osymtab->set_link(ostrtab->out_shndx()); |
| |
| // Create the section table header. |
| Output_section_headers* oshdrs = this->create_shdrs(size, big_endian, &off); |
| |
| file_header->set_section_info(oshdrs, shstrtab_section); |
| |
| // Now we know exactly where everything goes in the output file. |
| |
| return off; |
| } |
| |
| // Return whether SEG1 should be before SEG2 in the output file. This |
| // is based entirely on the segment type and flags. When this is |
| // called the segment addresses has normally not yet been set. |
| |
| bool |
| Layout::segment_precedes(const Output_segment* seg1, |
| const Output_segment* seg2) |
| { |
| elfcpp::Elf_Word type1 = seg1->type(); |
| elfcpp::Elf_Word type2 = seg2->type(); |
| |
| // The single PT_PHDR segment is required to precede any loadable |
| // segment. We simply make it always first. |
| if (type1 == elfcpp::PT_PHDR) |
| { |
| assert(type2 != elfcpp::PT_PHDR); |
| return true; |
| } |
| if (type2 == elfcpp::PT_PHDR) |
| return false; |
| |
| // The single PT_INTERP segment is required to precede any loadable |
| // segment. We simply make it always second. |
| if (type1 == elfcpp::PT_INTERP) |
| { |
| assert(type2 != elfcpp::PT_INTERP); |
| return true; |
| } |
| if (type2 == elfcpp::PT_INTERP) |
| return false; |
| |
| // We then put PT_LOAD segments before any other segments. |
| if (type1 == elfcpp::PT_LOAD && type2 != elfcpp::PT_LOAD) |
| return true; |
| if (type2 == elfcpp::PT_LOAD && type1 != elfcpp::PT_LOAD) |
| return false; |
| |
| // We put the PT_TLS segment last, because that is where the dynamic |
| // linker expects to find it (this is just for efficiency; other |
| // positions would also work correctly). |
| if (type1 == elfcpp::PT_TLS && type2 != elfcpp::PT_TLS) |
| return false; |
| if (type2 == elfcpp::PT_TLS && type1 != elfcpp::PT_TLS) |
| return true; |
| |
| const elfcpp::Elf_Word flags1 = seg1->flags(); |
| const elfcpp::Elf_Word flags2 = seg2->flags(); |
| |
| // The order of non-PT_LOAD segments is unimportant. We simply sort |
| // by the numeric segment type and flags values. There should not |
| // be more than one segment with the same type and flags. |
| if (type1 != elfcpp::PT_LOAD) |
| { |
| if (type1 != type2) |
| return type1 < type2; |
| assert(flags1 != flags2); |
| return flags1 < flags2; |
| } |
| |
| // We sort PT_LOAD segments based on the flags. Readonly segments |
| // come before writable segments. Then executable segments come |
| // before non-executable segments. Then the unlikely case of a |
| // non-readable segment comes before the normal case of a readable |
| // segment. If there are multiple segments with the same type and |
| // flags, we require that the address be set, and we sort by |
| // virtual address and then physical address. |
| if ((flags1 & elfcpp::PF_W) != (flags2 & elfcpp::PF_W)) |
| return (flags1 & elfcpp::PF_W) == 0; |
| if ((flags1 & elfcpp::PF_X) != (flags2 & elfcpp::PF_X)) |
| return (flags1 & elfcpp::PF_X) != 0; |
| if ((flags1 & elfcpp::PF_R) != (flags2 & elfcpp::PF_R)) |
| return (flags1 & elfcpp::PF_R) == 0; |
| |
| uint64_t vaddr1 = seg1->vaddr(); |
| uint64_t vaddr2 = seg2->vaddr(); |
| if (vaddr1 != vaddr2) |
| return vaddr1 < vaddr2; |
| |
| uint64_t paddr1 = seg1->paddr(); |
| uint64_t paddr2 = seg2->paddr(); |
| assert(paddr1 != paddr2); |
| return paddr1 < paddr2; |
| } |
| |
| // Set the file offsets of all the segments, and all the sections they |
| // contain. They have all been created. LOAD_SEG must be be laid out |
| // first. Return the offset of the data to follow. |
| |
| off_t |
| Layout::set_segment_offsets(const Target* target, Output_segment* load_seg, |
| unsigned int *pshndx) |
| { |
| // Sort them into the final order. |
| std::sort(this->segment_list_.begin(), this->segment_list_.end(), |
| Layout::Compare_segments()); |
| |
| // Find the PT_LOAD segments, and set their addresses and offsets |
| // and their section's addresses and offsets. |
| uint64_t addr = target->text_segment_address(); |
| off_t off = 0; |
| bool was_readonly = false; |
| for (Segment_list::iterator p = this->segment_list_.begin(); |
| p != this->segment_list_.end(); |
| ++p) |
| { |
| if ((*p)->type() == elfcpp::PT_LOAD) |
| { |
| if (load_seg != NULL && load_seg != *p) |
| abort(); |
| load_seg = NULL; |
| |
| // If the last segment was readonly, and this one is not, |
| // then skip the address forward one page, maintaining the |
| // same position within the page. This lets us store both |
| // segments overlapping on a single page in the file, but |
| // the loader will put them on different pages in memory. |
| |
| uint64_t orig_addr = addr; |
| uint64_t orig_off = off; |
| |
| uint64_t aligned_addr = addr; |
| uint64_t abi_pagesize = target->abi_pagesize(); |
| if (was_readonly && ((*p)->flags() & elfcpp::PF_W) != 0) |
| { |
| uint64_t align = (*p)->addralign(); |
| |
| addr = align_address(addr, align); |
| aligned_addr = addr; |
| if ((addr & (abi_pagesize - 1)) != 0) |
| addr = addr + abi_pagesize; |
| } |
| |
| unsigned int shndx_hold = *pshndx; |
| off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1)); |
| uint64_t new_addr = (*p)->set_section_addresses(addr, &off, pshndx); |
| |
| // Now that we know the size of this segment, we may be able |
| // to save a page in memory, at the cost of wasting some |
| // file space, by instead aligning to the start of a new |
| // page. Here we use the real machine page size rather than |
| // the ABI mandated page size. |
| |
| if (aligned_addr != addr) |
| { |
| uint64_t common_pagesize = target->common_pagesize(); |
| uint64_t first_off = (common_pagesize |
| - (aligned_addr |
| & (common_pagesize - 1))); |
| uint64_t last_off = new_addr & (common_pagesize - 1); |
| if (first_off > 0 |
| && last_off > 0 |
| && ((aligned_addr & ~ (common_pagesize - 1)) |
| != (new_addr & ~ (common_pagesize - 1))) |
| && first_off + last_off <= common_pagesize) |
| { |
| *pshndx = shndx_hold; |
| addr = align_address(aligned_addr, common_pagesize); |
| off = orig_off + ((addr - orig_addr) & (abi_pagesize - 1)); |
| new_addr = (*p)->set_section_addresses(addr, &off, pshndx); |
| } |
| } |
| |
| addr = new_addr; |
| |
| if (((*p)->flags() & elfcpp::PF_W) == 0) |
| was_readonly = true; |
| } |
| } |
| |
| // Handle the non-PT_LOAD segments, setting their offsets from their |
| // section's offsets. |
| for (Segment_list::iterator p = this->segment_list_.begin(); |
| p != this->segment_list_.end(); |
| ++p) |
| { |
| if ((*p)->type() != elfcpp::PT_LOAD) |
| (*p)->set_offset(); |
| } |
| |
| return off; |
| } |
| |
| // Set the file offset of all the sections not associated with a |
| // segment. |
| |
| off_t |
| Layout::set_section_offsets(off_t off, unsigned int* pshndx) |
| { |
| for (Layout::Section_list::iterator p = this->section_list_.begin(); |
| p != this->section_list_.end(); |
| ++p) |
| { |
| (*p)->set_out_shndx(*pshndx); |
| ++*pshndx; |
| if ((*p)->offset() != -1) |
| continue; |
| off = align_address(off, (*p)->addralign()); |
| (*p)->set_address(0, off); |
| off += (*p)->data_size(); |
| } |
| return off; |
| } |
| |
| // Create the symbol table sections. |
| |
| void |
| Layout::create_symtab_sections(int size, const Input_objects* input_objects, |
| Symbol_table* symtab, |
| off_t* poff, |
| Output_section** posymtab, |
| Output_section** postrtab) |
| { |
| int symsize; |
| unsigned int align; |
| if (size == 32) |
| { |
| symsize = elfcpp::Elf_sizes<32>::sym_size; |
| align = 4; |
| } |
| else if (size == 64) |
| { |
| symsize = elfcpp::Elf_sizes<64>::sym_size; |
| align = 8; |
| } |
| else |
| abort(); |
| |
| off_t off = *poff; |
| off = align_address(off, align); |
| off_t startoff = off; |
| |
| // Save space for the dummy symbol at the start of the section. We |
| // never bother to write this out--it will just be left as zero. |
| off += symsize; |
| |
| for (Input_objects::Relobj_iterator p = input_objects->relobj_begin(); |
| p != input_objects->relobj_end(); |
| ++p) |
| { |
| Task_lock_obj<Object> tlo(**p); |
| off = (*p)->finalize_local_symbols(off, &this->sympool_); |
| } |
| |
| unsigned int local_symcount = (off - startoff) / symsize; |
| assert(local_symcount * symsize == off - startoff); |
| |
| off = symtab->finalize(off, &this->sympool_); |
| |
| this->sympool_.set_string_offsets(); |
| |
| const char* symtab_name = this->namepool_.add(".symtab", NULL); |
| Output_section* osymtab = new Output_section_symtab(symtab_name, |
| off - startoff); |
| this->section_list_.push_back(osymtab); |
| |
| const char* strtab_name = this->namepool_.add(".strtab", NULL); |
| Output_section *ostrtab = new Output_section_strtab(strtab_name, |
| &this->sympool_); |
| this->section_list_.push_back(ostrtab); |
| this->special_output_list_.push_back(ostrtab); |
| |
| osymtab->set_address(0, startoff); |
| osymtab->set_info(local_symcount); |
| osymtab->set_entsize(symsize); |
| osymtab->set_addralign(align); |
| |
| *poff = off; |
| *posymtab = osymtab; |
| *postrtab = ostrtab; |
| } |
| |
| // Create the .shstrtab section, which holds the names of the |
| // sections. At the time this is called, we have created all the |
| // output sections except .shstrtab itself. |
| |
| Output_section* |
| Layout::create_shstrtab() |
| { |
| // FIXME: We don't need to create a .shstrtab section if we are |
| // stripping everything. |
| |
| const char* name = this->namepool_.add(".shstrtab", NULL); |
| |
| this->namepool_.set_string_offsets(); |
| |
| Output_section* os = new Output_section_strtab(name, &this->namepool_); |
| |
| this->section_list_.push_back(os); |
| this->special_output_list_.push_back(os); |
| |
| return os; |
| } |
| |
| // Create the section headers. SIZE is 32 or 64. OFF is the file |
| // offset. |
| |
| Output_section_headers* |
| Layout::create_shdrs(int size, bool big_endian, off_t* poff) |
| { |
| Output_section_headers* oshdrs; |
| oshdrs = new Output_section_headers(size, big_endian, this->segment_list_, |
| this->section_list_, |
| &this->namepool_); |
| off_t off = align_address(*poff, oshdrs->addralign()); |
| oshdrs->set_address(0, off); |
| off += oshdrs->data_size(); |
| *poff = off; |
| this->special_output_list_.push_back(oshdrs); |
| return oshdrs; |
| } |
| |
| // Create the dynamic symbol table. |
| |
| void |
| Layout::create_dynamic_symtab(int, Symbol_table*) |
| { |
| abort(); |
| } |
| |
| // Create the .dynamic section and PT_DYNAMIC segment. |
| |
| void |
| Layout::create_dynamic_section() |
| { |
| abort(); |
| } |
| |
| // Create the .interp section and PT_INTERP segment. |
| |
| void |
| Layout::create_interp(const Target* target) |
| { |
| const char* interp = this->options_.dynamic_linker(); |
| if (interp == NULL) |
| { |
| interp = target->dynamic_linker(); |
| assert(interp != NULL); |
| } |
| |
| size_t len = strlen(interp) + 1; |
| |
| Output_section_data* odata = new Output_data_const(interp, len, 1); |
| |
| const char* interp_name = this->namepool_.add(".interp", NULL); |
| Output_section* osec = this->make_output_section(interp_name, |
| elfcpp::SHT_PROGBITS, |
| elfcpp::SHF_ALLOC); |
| osec->add_output_section_data(odata); |
| |
| Output_segment* oseg = new Output_segment(elfcpp::PT_INTERP, elfcpp::PF_R); |
| this->segment_list_.push_back(oseg); |
| oseg->add_initial_output_section(osec, elfcpp::PF_R); |
| } |
| |
| // The mapping of .gnu.linkonce section names to real section names. |
| |
| #define MAPPING_INIT(f, t) { f, sizeof(f) - 1, t, sizeof(t) - 1 } |
| const Layout::Linkonce_mapping Layout::linkonce_mapping[] = |
| { |
| MAPPING_INIT("d.rel.ro", ".data.rel.ro"), // Must be before "d". |
| MAPPING_INIT("t", ".text"), |
| MAPPING_INIT("r", ".rodata"), |
| MAPPING_INIT("d", ".data"), |
| MAPPING_INIT("b", ".bss"), |
| MAPPING_INIT("s", ".sdata"), |
| MAPPING_INIT("sb", ".sbss"), |
| MAPPING_INIT("s2", ".sdata2"), |
| MAPPING_INIT("sb2", ".sbss2"), |
| MAPPING_INIT("wi", ".debug_info"), |
| MAPPING_INIT("td", ".tdata"), |
| MAPPING_INIT("tb", ".tbss"), |
| MAPPING_INIT("lr", ".lrodata"), |
| MAPPING_INIT("l", ".ldata"), |
| MAPPING_INIT("lb", ".lbss"), |
| }; |
| #undef MAPPING_INIT |
| |
| const int Layout::linkonce_mapping_count = |
| sizeof(Layout::linkonce_mapping) / sizeof(Layout::linkonce_mapping[0]); |
| |
| // Return the name of the output section to use for a .gnu.linkonce |
| // section. This is based on the default ELF linker script of the old |
| // GNU linker. For example, we map a name like ".gnu.linkonce.t.foo" |
| // to ".text". Set *PLEN to the length of the name. *PLEN is |
| // initialized to the length of NAME. |
| |
| const char* |
| Layout::linkonce_output_name(const char* name, size_t *plen) |
| { |
| const char* s = name + sizeof(".gnu.linkonce") - 1; |
| if (*s != '.') |
| return name; |
| ++s; |
| const Linkonce_mapping* plm = linkonce_mapping; |
| for (int i = 0; i < linkonce_mapping_count; ++i, ++plm) |
| { |
| if (strncmp(s, plm->from, plm->fromlen) == 0 && s[plm->fromlen] == '.') |
| { |
| *plen = plm->tolen; |
| return plm->to; |
| } |
| } |
| return name; |
| } |
| |
| // Choose the output section name to use given an input section name. |
| // Set *PLEN to the length of the name. *PLEN is initialized to the |
| // length of NAME. |
| |
| const char* |
| Layout::output_section_name(const char* name, size_t* plen) |
| { |
| if (Layout::is_linkonce(name)) |
| { |
| // .gnu.linkonce sections are laid out as though they were named |
| // for the sections are placed into. |
| return Layout::linkonce_output_name(name, plen); |
| } |
| |
| // If the section name has no '.', or only an initial '.', we use |
| // the name unchanged (i.e., ".text" is unchanged). |
| |
| // Otherwise, if the section name does not include ".rel", we drop |
| // the last '.' and everything that follows (i.e., ".text.XXX" |
| // becomes ".text"). |
| |
| // Otherwise, if the section name has zero or one '.' after the |
| // ".rel", we use the name unchanged (i.e., ".rel.text" is |
| // unchanged). |
| |
| // Otherwise, we drop the last '.' and everything that follows |
| // (i.e., ".rel.text.XXX" becomes ".rel.text"). |
| |
| const char* s = name; |
| if (*s == '.') |
| ++s; |
| const char* sdot = strchr(s, '.'); |
| if (sdot == NULL) |
| return name; |
| |
| const char* srel = strstr(s, ".rel"); |
| if (srel == NULL) |
| { |
| *plen = sdot - name; |
| return name; |
| } |
| |
| sdot = strchr(srel + 1, '.'); |
| if (sdot == NULL) |
| return name; |
| sdot = strchr(sdot + 1, '.'); |
| if (sdot == NULL) |
| return name; |
| |
| *plen = sdot - name; |
| return name; |
| } |
| |
| // Record the signature of a comdat section, and return whether to |
| // include it in the link. If GROUP is true, this is a regular |
| // section group. If GROUP is false, this is a group signature |
| // derived from the name of a linkonce section. We want linkonce |
| // signatures and group signatures to block each other, but we don't |
| // want a linkonce signature to block another linkonce signature. |
| |
| bool |
| Layout::add_comdat(const char* signature, bool group) |
| { |
| std::string sig(signature); |
| std::pair<Signatures::iterator, bool> ins( |
| this->signatures_.insert(std::make_pair(sig, group))); |
| |
| if (ins.second) |
| { |
| // This is the first time we've seen this signature. |
| return true; |
| } |
| |
| if (ins.first->second) |
| { |
| // We've already seen a real section group with this signature. |
| return false; |
| } |
| else if (group) |
| { |
| // This is a real section group, and we've already seen a |
| // linkonce section with tihs signature. Record that we've seen |
| // a section group, and don't include this section group. |
| ins.first->second = true; |
| return false; |
| } |
| else |
| { |
| // We've already seen a linkonce section and this is a linkonce |
| // section. These don't block each other--this may be the same |
| // symbol name with different section types. |
| return true; |
| } |
| } |
| |
| // Write out data not associated with a section or the symbol table. |
| |
| void |
| Layout::write_data(Output_file* of) const |
| { |
| for (Data_list::const_iterator p = this->special_output_list_.begin(); |
| p != this->special_output_list_.end(); |
| ++p) |
| (*p)->write(of); |
| } |
| |
| // Write_data_task methods. |
| |
| // We can always run this task. |
| |
| Task::Is_runnable_type |
| Write_data_task::is_runnable(Workqueue*) |
| { |
| return IS_RUNNABLE; |
| } |
| |
| // We need to unlock FINAL_BLOCKER when finished. |
| |
| Task_locker* |
| Write_data_task::locks(Workqueue* workqueue) |
| { |
| return new Task_locker_block(*this->final_blocker_, workqueue); |
| } |
| |
| // Run the task--write out the data. |
| |
| void |
| Write_data_task::run(Workqueue*) |
| { |
| this->layout_->write_data(this->of_); |
| } |
| |
| // Write_symbols_task methods. |
| |
| // We can always run this task. |
| |
| Task::Is_runnable_type |
| Write_symbols_task::is_runnable(Workqueue*) |
| { |
| return IS_RUNNABLE; |
| } |
| |
| // We need to unlock FINAL_BLOCKER when finished. |
| |
| Task_locker* |
| Write_symbols_task::locks(Workqueue* workqueue) |
| { |
| return new Task_locker_block(*this->final_blocker_, workqueue); |
| } |
| |
| // Run the task--write out the symbols. |
| |
| void |
| Write_symbols_task::run(Workqueue*) |
| { |
| this->symtab_->write_globals(this->target_, this->sympool_, this->of_); |
| } |
| |
| // Close_task_runner methods. |
| |
| // Run the task--close the file. |
| |
| void |
| Close_task_runner::run(Workqueue*) |
| { |
| this->of_->close(); |
| } |
| |
| // Instantiate the templates we need. We could use the configure |
| // script to restrict this to only the ones for implemented targets. |
| |
| template |
| Output_section* |
| Layout::layout<32, false>(Relobj* object, unsigned int shndx, const char* name, |
| const elfcpp::Shdr<32, false>& shdr, off_t*); |
| |
| template |
| Output_section* |
| Layout::layout<32, true>(Relobj* object, unsigned int shndx, const char* name, |
| const elfcpp::Shdr<32, true>& shdr, off_t*); |
| |
| template |
| Output_section* |
| Layout::layout<64, false>(Relobj* object, unsigned int shndx, const char* name, |
| const elfcpp::Shdr<64, false>& shdr, off_t*); |
| |
| template |
| Output_section* |
| Layout::layout<64, true>(Relobj* object, unsigned int shndx, const char* name, |
| const elfcpp::Shdr<64, true>& shdr, off_t*); |
| |
| |
| } // End namespace gold. |