1 // merge.cc -- handle section merging for gold
3 // Copyright (C) 2006-2015 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
29 #include "compressed_output.h"
34 // Class Object_merge_map.
38 Object_merge_map::~Object_merge_map()
40 for (Section_merge_maps::iterator p = this->section_merge_maps_.begin();
41 p != this->section_merge_maps_.end();
46 // Get the Input_merge_map to use for an input section, or NULL.
48 const Object_merge_map::Input_merge_map*
49 Object_merge_map::get_input_merge_map(unsigned int shndx) const
51 gold_assert(shndx != -1U);
52 if (shndx == this->first_shnum_)
53 return &this->first_map_;
54 if (shndx == this->second_shnum_)
55 return &this->second_map_;
56 Section_merge_maps::const_iterator p = this->section_merge_maps_.find(shndx);
57 if (p != this->section_merge_maps_.end())
62 // Get or create the Input_merge_map to use for an input section.
64 Object_merge_map::Input_merge_map*
65 Object_merge_map::get_or_make_input_merge_map(
66 const Output_section_data* output_data, unsigned int shndx) {
67 Input_merge_map* map = this->get_input_merge_map(shndx);
70 // For a given input section in a given object, every mapping
71 // must be done with the same Merge_map.
72 gold_assert(map->output_data == output_data);
76 // We need to create a new entry.
77 if (this->first_shnum_ == -1U)
79 this->first_shnum_ = shndx;
80 this->first_map_.output_data = output_data;
81 return &this->first_map_;
83 if (this->second_shnum_ == -1U)
85 this->second_shnum_ = shndx;
86 this->second_map_.output_data = output_data;
87 return &this->second_map_;
90 Input_merge_map* new_map = new Input_merge_map;
91 new_map->output_data = output_data;
92 this->section_merge_maps_[shndx] = new_map;
99 Object_merge_map::add_mapping(const Output_section_data* output_data,
101 section_offset_type input_offset,
102 section_size_type length,
103 section_offset_type output_offset)
105 Input_merge_map* map = this->get_or_make_input_merge_map(output_data, shndx);
106 map->add_mapping(input_offset, length, output_offset);
110 Object_merge_map::Input_merge_map::add_mapping(
111 section_offset_type input_offset, section_size_type length,
112 section_offset_type output_offset) {
113 // Try to merge the new entry in the last one we saw.
114 if (!this->entries.empty())
116 Input_merge_entry& entry(this->entries.back());
118 // Use section_size_type to avoid signed/unsigned warnings.
119 section_size_type input_offset_u = input_offset;
120 section_size_type output_offset_u = output_offset;
122 // If this entry is not in order, we need to sort the vector
123 // before looking anything up.
124 if (input_offset_u < entry.input_offset + entry.length)
126 gold_assert(input_offset < entry.input_offset);
127 gold_assert(input_offset_u + length
128 <= static_cast<section_size_type>(entry.input_offset));
129 this->sorted = false;
131 else if (entry.input_offset + entry.length == input_offset_u
132 && (output_offset == -1
133 ? entry.output_offset == -1
134 : entry.output_offset + entry.length == output_offset_u))
136 entry.length += length;
141 Input_merge_entry entry;
142 entry.input_offset = input_offset;
143 entry.length = length;
144 entry.output_offset = output_offset;
145 this->entries.push_back(entry);
148 // Get the output offset for an input address.
151 Object_merge_map::get_output_offset(unsigned int shndx,
152 section_offset_type input_offset,
153 section_offset_type* output_offset)
155 Input_merge_map* map = this->get_input_merge_map(shndx);
161 std::sort(map->entries.begin(), map->entries.end(),
162 Input_merge_compare());
166 Input_merge_entry entry;
167 entry.input_offset = input_offset;
168 std::vector<Input_merge_entry>::const_iterator p =
169 std::upper_bound(map->entries.begin(), map->entries.end(),
170 entry, Input_merge_compare());
171 if (p == map->entries.begin())
174 gold_assert(p->input_offset <= input_offset);
176 if (input_offset - p->input_offset
177 >= static_cast<section_offset_type>(p->length))
180 *output_offset = p->output_offset;
181 if (*output_offset != -1)
182 *output_offset += (input_offset - p->input_offset);
186 // Return whether this is the merge map for section SHNDX.
188 const Output_section_data*
189 Object_merge_map::find_merge_section(unsigned int shndx) const {
190 const Object_merge_map::Input_merge_map* map =
191 this->get_input_merge_map(shndx);
194 return map->output_data;
197 // Initialize a mapping from input offsets to output addresses.
201 Object_merge_map::initialize_input_to_output_map(
203 typename elfcpp::Elf_types<size>::Elf_Addr starting_address,
204 Unordered_map<section_offset_type,
205 typename elfcpp::Elf_types<size>::Elf_Addr>* initialize_map)
207 Input_merge_map* map = this->get_input_merge_map(shndx);
208 gold_assert(map != NULL);
210 gold_assert(initialize_map->empty());
211 // We know how many entries we are going to add.
212 // reserve_unordered_map takes an expected count of buckets, not a
213 // count of elements, so double it to try to reduce collisions.
214 reserve_unordered_map(initialize_map, map->entries.size() * 2);
216 for (Input_merge_map::Entries::const_iterator p = map->entries.begin();
217 p != map->entries.end();
220 section_offset_type output_offset = p->output_offset;
221 if (output_offset != -1)
222 output_offset += starting_address;
225 // If we see a relocation against an address we have chosen
226 // to discard, we relocate to zero. FIXME: We could also
227 // issue a warning in this case; that would require
228 // reporting this somehow and checking it in the routines in
232 initialize_map->insert(std::make_pair(p->input_offset, output_offset));
236 // Class Output_merge_base.
238 // Return the output offset for an input offset. The input address is
239 // at offset OFFSET in section SHNDX in OBJECT. If we know the
240 // offset, set *POUTPUT and return true. Otherwise return false.
243 Output_merge_base::do_output_offset(const Relobj* object,
245 section_offset_type offset,
246 section_offset_type* poutput) const
248 return object->merge_output_offset(shndx, offset, poutput);
251 // Record a merged input section for script processing.
254 Output_merge_base::record_input_section(Relobj* relobj, unsigned int shndx)
256 gold_assert(this->keeps_input_sections_ && relobj != NULL);
257 // If this is the first input section, record it. We need do this because
258 // this->input_sections_ is unordered.
259 if (this->first_relobj_ == NULL)
261 this->first_relobj_ = relobj;
262 this->first_shndx_ = shndx;
265 std::pair<Input_sections::iterator, bool> result =
266 this->input_sections_.insert(Section_id(relobj, shndx));
267 // We should insert a merge section once only.
268 gold_assert(result.second);
271 // Class Output_merge_data.
273 // Compute the hash code for a fixed-size constant.
276 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
278 const unsigned char* p = this->pomd_->constant(k);
279 section_size_type entsize =
280 convert_to_section_size_type(this->pomd_->entsize());
282 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
283 if (sizeof(size_t) == 8)
285 size_t result = static_cast<size_t>(14695981039346656037ULL);
286 for (section_size_type i = 0; i < entsize; ++i)
288 result &= (size_t) *p++;
289 result *= 1099511628211ULL;
295 size_t result = 2166136261UL;
296 for (section_size_type i = 0; i < entsize; ++i)
298 result ^= (size_t) *p++;
299 result *= 16777619UL;
305 // Return whether one hash table key equals another.
308 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
309 Merge_data_key k2) const
311 const unsigned char* p1 = this->pomd_->constant(k1);
312 const unsigned char* p2 = this->pomd_->constant(k2);
313 return memcmp(p1, p2, this->pomd_->entsize()) == 0;
316 // Add a constant to the end of the section contents.
319 Output_merge_data::add_constant(const unsigned char* p)
321 section_size_type entsize = convert_to_section_size_type(this->entsize());
322 section_size_type addralign =
323 convert_to_section_size_type(this->addralign());
324 section_size_type addsize = std::max(entsize, addralign);
325 if (this->len_ + addsize > this->alc_)
328 this->alc_ = 128 * addsize;
331 this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
332 if (this->p_ == NULL)
336 memcpy(this->p_ + this->len_, p, entsize);
337 if (addsize > entsize)
338 memset(this->p_ + this->len_ + entsize, 0, addsize - entsize);
339 this->len_ += addsize;
342 // Add the input section SHNDX in OBJECT to a merged output section
343 // which holds fixed length constants. Return whether we were able to
344 // handle the section; if not, it will be linked as usual without
348 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
350 section_size_type len;
352 const unsigned char* p = object->decompressed_section_contents(shndx, &len,
355 section_size_type entsize = convert_to_section_size_type(this->entsize());
357 if (len % entsize != 0)
364 this->input_count_ += len / entsize;
366 Object_merge_map* merge_map = object->get_or_create_merge_map();
367 Object_merge_map::Input_merge_map* input_merge_map =
368 merge_map->get_or_make_input_merge_map(this, shndx);
370 for (section_size_type i = 0; i < len; i += entsize, p += entsize)
372 // Add the constant to the section contents. If we find that it
373 // is already in the hash table, we will remove it again.
374 Merge_data_key k = this->len_;
375 this->add_constant(p);
377 std::pair<Merge_data_hashtable::iterator, bool> ins =
378 this->hashtable_.insert(k);
382 // Key was already present. Remove the copy we just added.
383 this->len_ -= entsize;
387 // Record the offset of this constant in the output section.
388 input_merge_map->add_mapping(i, entsize, k);
391 // For script processing, we keep the input sections.
392 if (this->keeps_input_sections())
393 record_input_section(object, shndx);
401 // Set the final data size in a merged output section with fixed size
405 Output_merge_data::set_final_data_size()
407 // Release the memory we don't need.
408 this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
409 // An Output_merge_data object may be empty and realloc is allowed
410 // to return a NULL pointer in this case. An Output_merge_data is empty
411 // if all its input sections have sizes that are not multiples of entsize.
412 gold_assert(this->p_ != NULL || this->len_ == 0);
413 this->set_data_size(this->len_);
416 // Write the data of a merged output section with fixed size constants
420 Output_merge_data::do_write(Output_file* of)
422 of->write(this->offset(), this->p_, this->len_);
425 // Write the data to a buffer.
428 Output_merge_data::do_write_to_buffer(unsigned char* buffer)
430 memcpy(buffer, this->p_, this->len_);
433 // Print merge stats to stderr.
436 Output_merge_data::do_print_merge_stats(const char* section_name)
439 _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),
440 program_name, section_name,
441 static_cast<unsigned long>(this->entsize()),
442 this->input_count_, this->hashtable_.size());
445 // Class Output_merge_string.
447 // Add an input section to a merged string section.
449 template<typename Char_type>
451 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
454 section_size_type sec_len;
456 const unsigned char* pdata = object->decompressed_section_contents(shndx,
460 const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
461 const Char_type* pend = p + sec_len / sizeof(Char_type);
462 const Char_type* pend0 = pend;
464 if (sec_len % sizeof(Char_type) != 0)
466 object->error(_("mergeable string section length not multiple of "
475 gold_warning(_("%s: last entry in mergeable string section '%s' "
476 "not null terminated"),
477 object->name().c_str(),
478 object->section_name(shndx).c_str());
479 // Find the end of the last NULL-terminated string in the buffer.
480 while (pend0 > p && pend0[-1] != 0)
484 Merged_strings_list* merged_strings_list =
485 new Merged_strings_list(object, shndx);
486 this->merged_strings_lists_.push_back(merged_strings_list);
487 Merged_strings& merged_strings = merged_strings_list->merged_strings;
489 // Count the number of non-null strings in the section and size the list.
491 const Char_type* pt = p;
494 size_t len = string_length(pt);
501 merged_strings.reserve(count + 1);
503 // The index I is in bytes, not characters.
504 section_size_type i = 0;
506 // We assume here that the beginning of the section is correctly
507 // aligned, so each string within the section must retain the same
509 uintptr_t init_align_modulo = (reinterpret_cast<uintptr_t>(pdata)
510 & (this->addralign() - 1));
511 bool has_misaligned_strings = false;
515 size_t len = p < pend0 ? string_length(p) : pend - p;
517 // Within merge input section each string must be aligned.
519 && ((reinterpret_cast<uintptr_t>(p) & (this->addralign() - 1))
520 != init_align_modulo))
521 has_misaligned_strings = true;
524 this->stringpool_.add_with_length(p, len, true, &key);
526 merged_strings.push_back(Merged_string(i, key));
528 i += (len + 1) * sizeof(Char_type);
531 // Record the last offset in the input section so that we can
532 // compute the length of the last string.
533 merged_strings.push_back(Merged_string(i, 0));
535 this->input_count_ += count;
536 this->input_size_ += i;
538 if (has_misaligned_strings)
539 gold_warning(_("%s: section %s contains incorrectly aligned strings;"
540 " the alignment of those strings won't be preserved"),
541 object->name().c_str(),
542 object->section_name(shndx).c_str());
544 // For script processing, we keep the input sections.
545 if (this->keeps_input_sections())
546 record_input_section(object, shndx);
554 // Finalize the mappings from the input sections to the output
555 // section, and return the final data size.
557 template<typename Char_type>
559 Output_merge_string<Char_type>::finalize_merged_data()
561 this->stringpool_.set_string_offsets();
563 for (typename Merged_strings_lists::const_iterator l =
564 this->merged_strings_lists_.begin();
565 l != this->merged_strings_lists_.end();
568 section_offset_type last_input_offset = 0;
569 section_offset_type last_output_offset = 0;
570 Relobj *object = (*l)->object;
571 Object_merge_map* merge_map = object->get_or_create_merge_map();
572 Object_merge_map::Input_merge_map* input_merge_map =
573 merge_map->get_or_make_input_merge_map(this, (*l)->shndx);
575 for (typename Merged_strings::const_iterator p =
576 (*l)->merged_strings.begin();
577 p != (*l)->merged_strings.end();
580 section_size_type length = p->offset - last_input_offset;
582 input_merge_map->add_mapping(last_input_offset, length,
584 last_input_offset = p->offset;
585 if (p->stringpool_key != 0)
587 this->stringpool_.get_offset_from_key(p->stringpool_key);
592 // Save some memory. This also ensures that this function will work
593 // if called twice, as may happen if Layout::set_segment_offsets
594 // finds a better alignment.
595 this->merged_strings_lists_.clear();
597 return this->stringpool_.get_strtab_size();
600 template<typename Char_type>
602 Output_merge_string<Char_type>::set_final_data_size()
604 const off_t final_data_size = this->finalize_merged_data();
605 this->set_data_size(final_data_size);
608 // Write out a merged string section.
610 template<typename Char_type>
612 Output_merge_string<Char_type>::do_write(Output_file* of)
614 this->stringpool_.write(of, this->offset());
617 // Write a merged string section to a buffer.
619 template<typename Char_type>
621 Output_merge_string<Char_type>::do_write_to_buffer(unsigned char* buffer)
623 this->stringpool_.write_to_buffer(buffer, this->data_size());
626 // Return the name of the types of string to use with
627 // do_print_merge_stats.
629 template<typename Char_type>
631 Output_merge_string<Char_type>::string_name()
639 Output_merge_string<char>::string_name()
646 Output_merge_string<uint16_t>::string_name()
648 return "16-bit strings";
653 Output_merge_string<uint32_t>::string_name()
655 return "32-bit strings";
658 // Print merge stats to stderr.
660 template<typename Char_type>
662 Output_merge_string<Char_type>::do_print_merge_stats(const char* section_name)
665 snprintf(buf, sizeof buf, "%s merged %s", section_name, this->string_name());
666 fprintf(stderr, _("%s: %s input bytes: %zu\n"),
667 program_name, buf, this->input_size_);
668 fprintf(stderr, _("%s: %s input strings: %zu\n"),
669 program_name, buf, this->input_count_);
670 this->stringpool_.print_stats(buf);
673 // Instantiate the templates we need.
676 class Output_merge_string<char>;
679 class Output_merge_string<uint16_t>;
682 class Output_merge_string<uint32_t>;
684 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
687 Object_merge_map::initialize_input_to_output_map<32>(
689 elfcpp::Elf_types<32>::Elf_Addr starting_address,
690 Unordered_map<section_offset_type, elfcpp::Elf_types<32>::Elf_Addr>*);
693 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
696 Object_merge_map::initialize_input_to_output_map<64>(
698 elfcpp::Elf_types<64>::Elf_Addr starting_address,
699 Unordered_map<section_offset_type, elfcpp::Elf_types<64>::Elf_Addr>*);
702 } // End namespace gold.