// merge.cc -- handle section merging for gold // Copyright 2006, 2007, 2008 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" 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. Object_merge_map::Input_merge_map* Object_merge_map::get_input_merge_map(unsigned int shndx) { gold_assert(shndx != -1U); if (shndx == this->first_shnum_) return &this->first_map_; if (shndx == this->second_shnum_) return &this->second_map_; Section_merge_maps::const_iterator p = this->section_merge_maps_.find(shndx); if (p != this->section_merge_maps_.end()) return p->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 Merge_map* merge_map, 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->merge_map == merge_map); return map; } // We need to create a new entry. if (this->first_shnum_ == -1U) { this->first_shnum_ = shndx; this->first_map_.merge_map = merge_map; return &this->first_map_; } if (this->second_shnum_ == -1U) { this->second_shnum_ = shndx; this->second_map_.merge_map = merge_map; return &this->second_map_; } Input_merge_map* new_map = new Input_merge_map; new_map->merge_map = merge_map; this->section_merge_maps_[shndx] = new_map; return new_map; } // Add a mapping. void Object_merge_map::add_mapping(const Merge_map* merge_map, 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(merge_map, shndx); // Try to merge the new entry in the last one we saw. if (!map->entries.empty()) { Input_merge_entry& entry(map->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)); map->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; map->entries.push_back(entry); } // Get the output offset for an input address. bool Object_merge_map::get_output_offset(const Merge_map* merge_map, 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 || (merge_map != NULL && map->merge_map != merge_map)) 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::lower_bound(map->entries.begin(), map->entries.end(), entry, Input_merge_compare()); if (p == map->entries.end() || p->input_offset > input_offset) { 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. inline bool Object_merge_map::is_merge_section_for(const Merge_map* merge_map, unsigned int shndx) { Input_merge_map* map = this->get_input_merge_map(shndx); return map != NULL && map->merge_map == merge_map; } // 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 Merge_map. // Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in input // section SHNDX in object OBJECT to an OUTPUT_OFFSET in merged data // in an output section. void Merge_map::add_mapping(Relobj* object, unsigned int shndx, section_offset_type offset, section_size_type length, section_offset_type output_offset) { Object_merge_map* object_merge_map = object->merge_map(); if (object_merge_map == NULL) { object_merge_map = new Object_merge_map(); object->set_merge_map(object_merge_map); } object_merge_map->add_mapping(this, shndx, offset, length, output_offset); } // Return the output offset for an input address. The input address // is at offset OFFSET in section SHNDX in OBJECT. This sets // *OUTPUT_OFFSET to the offset in the merged data in the output // section. This returns true if the mapping is known, false // otherwise. bool Merge_map::get_output_offset(const Relobj* object, unsigned int shndx, section_offset_type offset, section_offset_type* output_offset) const { Object_merge_map* object_merge_map = object->merge_map(); if (object_merge_map == NULL) return false; return object_merge_map->get_output_offset(this, shndx, offset, output_offset); } // Return whether this is the merge section for SHNDX in OBJECT. bool Merge_map::is_merge_section_for(const Relobj* object, unsigned int shndx) const { Object_merge_map* object_merge_map = object->merge_map(); if (object_merge_map == NULL) return false; return object_merge_map->is_merge_section_for(this, shndx); } // 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 this->merge_map_.get_output_offset(object, shndx, offset, poutput); } // Return whether this is the merge section for SHNDX in OBJECT. bool Output_merge_base::do_is_merge_section_for(const Relobj* object, unsigned int shndx) const { return this->merge_map_.is_merge_section_for(object, shndx); } // 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; const unsigned char* p = object->section_contents(shndx, &len, false); section_size_type entsize = convert_to_section_size_type(this->entsize()); if (len % entsize != 0) return false; this->input_count_ += len / entsize; 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. this->add_mapping(object, shndx, i, entsize, k); } 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_)); gold_assert(this->p_ != NULL); 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 len; const unsigned char* pdata = object->section_contents(shndx, &len, false); const Char_type* p = reinterpret_cast<const Char_type*>(pdata); const Char_type* pend = p + len / sizeof(Char_type); if (len % sizeof(Char_type) != 0) { object->error(_("mergeable string section length not multiple of " "character size")); return false; } size_t count = 0; // The index I is in bytes, not characters. section_size_type i = 0; while (i < len) { const Char_type* pl; for (pl = p; *pl != 0; ++pl) { if (pl >= pend) { gold_warning(_("%s: last entry in mergeable string section '%s' " "not null terminated"), object->name().c_str(), object->section_name(shndx).c_str()); break; } } Stringpool::Key key; const Char_type* str = this->stringpool_.add_with_length(p, pl - p, true, &key); section_size_type bytelen_with_null = ((pl - p) + 1) * sizeof(Char_type); this->merged_strings_.push_back(Merged_string(object, shndx, i, str, bytelen_with_null, key)); p = pl + 1; i += bytelen_with_null; ++count; } this->input_count_ += count; 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::const_iterator p = this->merged_strings_.begin(); p != this->merged_strings_.end(); ++p) { section_offset_type offset = this->stringpool_.get_offset_from_key(p->stringpool_key); this->add_mapping(p->object, p->shndx, p->offset, p->length, offset); } // 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_.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: %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.