// merge.cc -- handle section merging for gold // Copyright (C) 2006-2018 Free Software Foundation, Inc. // Written by Ian Lance Taylor <iant@google.com>. // This file is part of gold. // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3 of the License, or // (at your option) any later version. // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, // MA 02110-1301, USA. #include "gold.h" #include <cstdlib> #include <algorithm> #include "merge.h" #include "compressed_output.h" namespace gold { // Class Object_merge_map. // Destructor. Object_merge_map::~Object_merge_map() { for (Section_merge_maps::iterator p = this->section_merge_maps_.begin(); p != this->section_merge_maps_.end(); ++p) delete p->second; } // Get the Input_merge_map to use for an input section, or NULL. const Object_merge_map::Input_merge_map* Object_merge_map::get_input_merge_map(unsigned int shndx) const { gold_assert(shndx != -1U); const Section_merge_maps &maps = this->section_merge_maps_; for (Section_merge_maps::const_iterator i = maps.begin(), e = maps.end(); i != e; ++i) { if (i->first == shndx) return i->second; } return NULL; } // Get or create the Input_merge_map to use for an input section. Object_merge_map::Input_merge_map* Object_merge_map::get_or_make_input_merge_map( const Output_section_data* output_data, unsigned int shndx) { Input_merge_map* map = this->get_input_merge_map(shndx); if (map != NULL) { // For a given input section in a given object, every mapping // must be done with the same Merge_map. gold_assert(map->output_data == output_data); return map; } Input_merge_map* new_map = new Input_merge_map; new_map->output_data = output_data; Section_merge_maps &maps = this->section_merge_maps_; maps.push_back(std::make_pair(shndx, new_map)); return new_map; } // Add a mapping. void Object_merge_map::add_mapping(const Output_section_data* output_data, unsigned int shndx, section_offset_type input_offset, section_size_type length, section_offset_type output_offset) { Input_merge_map* map = this->get_or_make_input_merge_map(output_data, shndx); map->add_mapping(input_offset, length, output_offset); } void Object_merge_map::Input_merge_map::add_mapping( section_offset_type input_offset, section_size_type length, section_offset_type output_offset) { // Try to merge the new entry in the last one we saw. if (!this->entries.empty()) { Input_merge_entry& entry(this->entries.back()); // Use section_size_type to avoid signed/unsigned warnings. section_size_type input_offset_u = input_offset; section_size_type output_offset_u = output_offset; // If this entry is not in order, we need to sort the vector // before looking anything up. if (input_offset_u < entry.input_offset + entry.length) { gold_assert(input_offset < entry.input_offset); gold_assert(input_offset_u + length <= static_cast<section_size_type>(entry.input_offset)); this->sorted = false; } else if (entry.input_offset + entry.length == input_offset_u && (output_offset == -1 ? entry.output_offset == -1 : entry.output_offset + entry.length == output_offset_u)) { entry.length += length; return; } } Input_merge_entry entry; entry.input_offset = input_offset; entry.length = length; entry.output_offset = output_offset; this->entries.push_back(entry); } // Get the output offset for an input address. bool Object_merge_map::get_output_offset(unsigned int shndx, section_offset_type input_offset, section_offset_type* output_offset) { Input_merge_map* map = this->get_input_merge_map(shndx); if (map == NULL) return false; if (!map->sorted) { std::sort(map->entries.begin(), map->entries.end(), Input_merge_compare()); map->sorted = true; } Input_merge_entry entry; entry.input_offset = input_offset; std::vector<Input_merge_entry>::const_iterator p = std::upper_bound(map->entries.begin(), map->entries.end(), entry, Input_merge_compare()); if (p == map->entries.begin()) return false; --p; gold_assert(p->input_offset <= input_offset); if (input_offset - p->input_offset >= static_cast<section_offset_type>(p->length)) return false; *output_offset = p->output_offset; if (*output_offset != -1) *output_offset += (input_offset - p->input_offset); return true; } // Return whether this is the merge map for section SHNDX. const Output_section_data* Object_merge_map::find_merge_section(unsigned int shndx) const { const Object_merge_map::Input_merge_map* map = this->get_input_merge_map(shndx); if (map == NULL) return NULL; return map->output_data; } // Initialize a mapping from input offsets to output addresses. template<int size> void Object_merge_map::initialize_input_to_output_map( unsigned int shndx, typename elfcpp::Elf_types<size>::Elf_Addr starting_address, Unordered_map<section_offset_type, typename elfcpp::Elf_types<size>::Elf_Addr>* initialize_map) { Input_merge_map* map = this->get_input_merge_map(shndx); gold_assert(map != NULL); gold_assert(initialize_map->empty()); // We know how many entries we are going to add. // reserve_unordered_map takes an expected count of buckets, not a // count of elements, so double it to try to reduce collisions. reserve_unordered_map(initialize_map, map->entries.size() * 2); for (Input_merge_map::Entries::const_iterator p = map->entries.begin(); p != map->entries.end(); ++p) { section_offset_type output_offset = p->output_offset; if (output_offset != -1) output_offset += starting_address; else { // If we see a relocation against an address we have chosen // to discard, we relocate to zero. FIXME: We could also // issue a warning in this case; that would require // reporting this somehow and checking it in the routines in // reloc.h. output_offset = 0; } initialize_map->insert(std::make_pair(p->input_offset, output_offset)); } } // Class Output_merge_base. // Return the output offset for an input offset. The input address is // at offset OFFSET in section SHNDX in OBJECT. If we know the // offset, set *POUTPUT and return true. Otherwise return false. bool Output_merge_base::do_output_offset(const Relobj* object, unsigned int shndx, section_offset_type offset, section_offset_type* poutput) const { return object->merge_output_offset(shndx, offset, poutput); } // Record a merged input section for script processing. void Output_merge_base::record_input_section(Relobj* relobj, unsigned int shndx) { gold_assert(this->keeps_input_sections_ && relobj != NULL); // If this is the first input section, record it. We need do this because // this->input_sections_ is unordered. if (this->first_relobj_ == NULL) { this->first_relobj_ = relobj; this->first_shndx_ = shndx; } std::pair<Input_sections::iterator, bool> result = this->input_sections_.insert(Section_id(relobj, shndx)); // We should insert a merge section once only. gold_assert(result.second); } // Class Output_merge_data. // Compute the hash code for a fixed-size constant. size_t Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const { const unsigned char* p = this->pomd_->constant(k); section_size_type entsize = convert_to_section_size_type(this->pomd_->entsize()); // Fowler/Noll/Vo (FNV) hash (type FNV-1a). if (sizeof(size_t) == 8) { size_t result = static_cast<size_t>(14695981039346656037ULL); for (section_size_type i = 0; i < entsize; ++i) { result &= (size_t) *p++; result *= 1099511628211ULL; } return result; } else { size_t result = 2166136261UL; for (section_size_type i = 0; i < entsize; ++i) { result ^= (size_t) *p++; result *= 16777619UL; } return result; } } // Return whether one hash table key equals another. bool Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1, Merge_data_key k2) const { const unsigned char* p1 = this->pomd_->constant(k1); const unsigned char* p2 = this->pomd_->constant(k2); return memcmp(p1, p2, this->pomd_->entsize()) == 0; } // Add a constant to the end of the section contents. void Output_merge_data::add_constant(const unsigned char* p) { section_size_type entsize = convert_to_section_size_type(this->entsize()); section_size_type addralign = convert_to_section_size_type(this->addralign()); section_size_type addsize = std::max(entsize, addralign); if (this->len_ + addsize > this->alc_) { if (this->alc_ == 0) this->alc_ = 128 * addsize; else this->alc_ *= 2; this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_)); if (this->p_ == NULL) gold_nomem(); } memcpy(this->p_ + this->len_, p, entsize); if (addsize > entsize) memset(this->p_ + this->len_ + entsize, 0, addsize - entsize); this->len_ += addsize; } // Add the input section SHNDX in OBJECT to a merged output section // which holds fixed length constants. Return whether we were able to // handle the section; if not, it will be linked as usual without // constant merging. bool Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx) { section_size_type len; bool is_new; const unsigned char* p = object->decompressed_section_contents(shndx, &len, &is_new); section_size_type entsize = convert_to_section_size_type(this->entsize()); if (len % entsize != 0) { if (is_new) delete[] p; return false; } this->input_count_ += len / entsize; Object_merge_map* merge_map = object->get_or_create_merge_map(); Object_merge_map::Input_merge_map* input_merge_map = merge_map->get_or_make_input_merge_map(this, shndx); for (section_size_type i = 0; i < len; i += entsize, p += entsize) { // Add the constant to the section contents. If we find that it // is already in the hash table, we will remove it again. Merge_data_key k = this->len_; this->add_constant(p); std::pair<Merge_data_hashtable::iterator, bool> ins = this->hashtable_.insert(k); if (!ins.second) { // Key was already present. Remove the copy we just added. this->len_ -= entsize; k = *ins.first; } // Record the offset of this constant in the output section. input_merge_map->add_mapping(i, entsize, k); } // For script processing, we keep the input sections. if (this->keeps_input_sections()) record_input_section(object, shndx); if (is_new) delete[] p; return true; } // Set the final data size in a merged output section with fixed size // constants. void Output_merge_data::set_final_data_size() { // Release the memory we don't need. this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_)); // An Output_merge_data object may be empty and realloc is allowed // to return a NULL pointer in this case. An Output_merge_data is empty // if all its input sections have sizes that are not multiples of entsize. gold_assert(this->p_ != NULL || this->len_ == 0); this->set_data_size(this->len_); } // Write the data of a merged output section with fixed size constants // to the file. void Output_merge_data::do_write(Output_file* of) { of->write(this->offset(), this->p_, this->len_); } // Write the data to a buffer. void Output_merge_data::do_write_to_buffer(unsigned char* buffer) { memcpy(buffer, this->p_, this->len_); } // Print merge stats to stderr. void Output_merge_data::do_print_merge_stats(const char* section_name) { fprintf(stderr, _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"), program_name, section_name, static_cast<unsigned long>(this->entsize()), this->input_count_, this->hashtable_.size()); } // Class Output_merge_string. // Add an input section to a merged string section. template<typename Char_type> bool Output_merge_string<Char_type>::do_add_input_section(Relobj* object, unsigned int shndx) { section_size_type sec_len; bool is_new; uint64_t addralign = this->addralign(); const unsigned char* pdata = object->decompressed_section_contents(shndx, &sec_len, &is_new, &addralign); const Char_type* p = reinterpret_cast<const Char_type*>(pdata); const Char_type* pend = p + sec_len / sizeof(Char_type); const Char_type* pend0 = pend; if (sec_len % sizeof(Char_type) != 0) { object->error(_("mergeable string section length not multiple of " "character size")); if (is_new) delete[] pdata; return false; } if (pend[-1] != 0) { gold_warning(_("%s: last entry in mergeable string section '%s' " "not null terminated"), object->name().c_str(), object->section_name(shndx).c_str()); // Find the end of the last NULL-terminated string in the buffer. while (pend0 > p && pend0[-1] != 0) --pend0; } Merged_strings_list* merged_strings_list = new Merged_strings_list(object, shndx); this->merged_strings_lists_.push_back(merged_strings_list); Merged_strings& merged_strings = merged_strings_list->merged_strings; // Count the number of non-null strings in the section and size the list. size_t count = 0; const Char_type* pt = p; while (pt < pend0) { size_t len = string_length(pt); if (len != 0) ++count; pt += len + 1; } if (pend0 < pend) ++count; merged_strings.reserve(count + 1); // The index I is in bytes, not characters. section_size_type i = 0; // We assume here that the beginning of the section is correctly // aligned, so each string within the section must retain the same // modulo. uintptr_t init_align_modulo = (reinterpret_cast<uintptr_t>(pdata) & (addralign - 1)); bool has_misaligned_strings = false; while (p < pend) { size_t len = p < pend0 ? string_length(p) : pend - p; // Within merge input section each string must be aligned. if (len != 0 && ((reinterpret_cast<uintptr_t>(p) & (addralign - 1)) != init_align_modulo)) has_misaligned_strings = true; Stringpool::Key key; this->stringpool_.add_with_length(p, len, true, &key); merged_strings.push_back(Merged_string(i, key)); p += len + 1; i += (len + 1) * sizeof(Char_type); } // Record the last offset in the input section so that we can // compute the length of the last string. merged_strings.push_back(Merged_string(i, 0)); this->input_count_ += count; this->input_size_ += i; if (has_misaligned_strings) gold_warning(_("%s: section %s contains incorrectly aligned strings;" " the alignment of those strings won't be preserved"), object->name().c_str(), object->section_name(shndx).c_str()); // For script processing, we keep the input sections. if (this->keeps_input_sections()) record_input_section(object, shndx); if (is_new) delete[] pdata; return true; } // Finalize the mappings from the input sections to the output // section, and return the final data size. template<typename Char_type> section_size_type Output_merge_string<Char_type>::finalize_merged_data() { this->stringpool_.set_string_offsets(); for (typename Merged_strings_lists::const_iterator l = this->merged_strings_lists_.begin(); l != this->merged_strings_lists_.end(); ++l) { section_offset_type last_input_offset = 0; section_offset_type last_output_offset = 0; Relobj *object = (*l)->object; Object_merge_map* merge_map = object->get_or_create_merge_map(); Object_merge_map::Input_merge_map* input_merge_map = merge_map->get_or_make_input_merge_map(this, (*l)->shndx); for (typename Merged_strings::const_iterator p = (*l)->merged_strings.begin(); p != (*l)->merged_strings.end(); ++p) { section_size_type length = p->offset - last_input_offset; if (length > 0) input_merge_map->add_mapping(last_input_offset, length, last_output_offset); last_input_offset = p->offset; if (p->stringpool_key != 0) last_output_offset = this->stringpool_.get_offset_from_key(p->stringpool_key); } delete *l; } // Save some memory. This also ensures that this function will work // if called twice, as may happen if Layout::set_segment_offsets // finds a better alignment. this->merged_strings_lists_.clear(); return this->stringpool_.get_strtab_size(); } template<typename Char_type> void Output_merge_string<Char_type>::set_final_data_size() { const off_t final_data_size = this->finalize_merged_data(); this->set_data_size(final_data_size); } // Write out a merged string section. template<typename Char_type> void Output_merge_string<Char_type>::do_write(Output_file* of) { this->stringpool_.write(of, this->offset()); } // Write a merged string section to a buffer. template<typename Char_type> void Output_merge_string<Char_type>::do_write_to_buffer(unsigned char* buffer) { this->stringpool_.write_to_buffer(buffer, this->data_size()); } // Return the name of the types of string to use with // do_print_merge_stats. template<typename Char_type> const char* Output_merge_string<Char_type>::string_name() { gold_unreachable(); return NULL; } template<> const char* Output_merge_string<char>::string_name() { return "strings"; } template<> const char* Output_merge_string<uint16_t>::string_name() { return "16-bit strings"; } template<> const char* Output_merge_string<uint32_t>::string_name() { return "32-bit strings"; } // Print merge stats to stderr. template<typename Char_type> void Output_merge_string<Char_type>::do_print_merge_stats(const char* section_name) { char buf[200]; snprintf(buf, sizeof buf, "%s merged %s", section_name, this->string_name()); fprintf(stderr, _("%s: %s input bytes: %zu\n"), program_name, buf, this->input_size_); fprintf(stderr, _("%s: %s input strings: %zu\n"), program_name, buf, this->input_count_); this->stringpool_.print_stats(buf); } // Instantiate the templates we need. template class Output_merge_string<char>; template class Output_merge_string<uint16_t>; template class Output_merge_string<uint32_t>; #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG) template void Object_merge_map::initialize_input_to_output_map<32>( unsigned int shndx, elfcpp::Elf_types<32>::Elf_Addr starting_address, Unordered_map<section_offset_type, elfcpp::Elf_types<32>::Elf_Addr>*); #endif #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG) template void Object_merge_map::initialize_input_to_output_map<64>( unsigned int shndx, elfcpp::Elf_types<64>::Elf_Addr starting_address, Unordered_map<section_offset_type, elfcpp::Elf_types<64>::Elf_Addr>*); #endif } // End namespace gold.