2011-09-19 Tristan Gingold <gingold@adacore.com>
[binutils.git] / gold / merge.cc
blob093b6fc692f5e495574aca5226a7630d8836c036
1 // merge.cc -- handle section merging for gold
3 // Copyright 2006, 2007, 2008, 2009, 2010, 2011 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.
23 #include "gold.h"
25 #include <cstdlib>
26 #include <algorithm>
28 #include "merge.h"
29 #include "compressed_output.h"
31 namespace gold
34 // Class Object_merge_map.
36 // Destructor.
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();
42 ++p)
43 delete p->second;
46 // Get the Input_merge_map to use for an input section, or NULL.
48 Object_merge_map::Input_merge_map*
49 Object_merge_map::get_input_merge_map(unsigned int shndx)
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())
58 return p->second;
59 return NULL;
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(const Merge_map* merge_map,
66 unsigned int shndx)
68 Input_merge_map* map = this->get_input_merge_map(shndx);
69 if (map != NULL)
71 // For a given input section in a given object, every mapping
72 // must be done with the same Merge_map.
73 gold_assert(map->merge_map == merge_map);
74 return map;
77 // We need to create a new entry.
78 if (this->first_shnum_ == -1U)
80 this->first_shnum_ = shndx;
81 this->first_map_.merge_map = merge_map;
82 return &this->first_map_;
84 if (this->second_shnum_ == -1U)
86 this->second_shnum_ = shndx;
87 this->second_map_.merge_map = merge_map;
88 return &this->second_map_;
91 Input_merge_map* new_map = new Input_merge_map;
92 new_map->merge_map = merge_map;
93 this->section_merge_maps_[shndx] = new_map;
94 return new_map;
97 // Add a mapping.
99 void
100 Object_merge_map::add_mapping(const Merge_map* merge_map, unsigned int shndx,
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(merge_map, shndx);
107 // Try to merge the new entry in the last one we saw.
108 if (!map->entries.empty())
110 Input_merge_entry& entry(map->entries.back());
112 // Use section_size_type to avoid signed/unsigned warnings.
113 section_size_type input_offset_u = input_offset;
114 section_size_type output_offset_u = output_offset;
116 // If this entry is not in order, we need to sort the vector
117 // before looking anything up.
118 if (input_offset_u < entry.input_offset + entry.length)
120 gold_assert(input_offset < entry.input_offset);
121 gold_assert(input_offset_u + length
122 <= static_cast<section_size_type>(entry.input_offset));
123 map->sorted = false;
125 else if (entry.input_offset + entry.length == input_offset_u
126 && (output_offset == -1
127 ? entry.output_offset == -1
128 : entry.output_offset + entry.length == output_offset_u))
130 entry.length += length;
131 return;
135 Input_merge_entry entry;
136 entry.input_offset = input_offset;
137 entry.length = length;
138 entry.output_offset = output_offset;
139 map->entries.push_back(entry);
142 // Get the output offset for an input address.
144 bool
145 Object_merge_map::get_output_offset(const Merge_map* merge_map,
146 unsigned int shndx,
147 section_offset_type input_offset,
148 section_offset_type* output_offset)
150 Input_merge_map* map = this->get_input_merge_map(shndx);
151 if (map == NULL
152 || (merge_map != NULL && map->merge_map != merge_map))
153 return false;
155 if (!map->sorted)
157 std::sort(map->entries.begin(), map->entries.end(),
158 Input_merge_compare());
159 map->sorted = true;
162 Input_merge_entry entry;
163 entry.input_offset = input_offset;
164 std::vector<Input_merge_entry>::const_iterator p =
165 std::lower_bound(map->entries.begin(), map->entries.end(),
166 entry, Input_merge_compare());
167 if (p == map->entries.end() || p->input_offset > input_offset)
169 if (p == map->entries.begin())
170 return false;
171 --p;
172 gold_assert(p->input_offset <= input_offset);
175 if (input_offset - p->input_offset
176 >= static_cast<section_offset_type>(p->length))
177 return false;
179 *output_offset = p->output_offset;
180 if (*output_offset != -1)
181 *output_offset += (input_offset - p->input_offset);
182 return true;
185 // Return whether this is the merge map for section SHNDX.
187 inline bool
188 Object_merge_map::is_merge_section_for(const Merge_map* merge_map,
189 unsigned int shndx)
191 Input_merge_map* map = this->get_input_merge_map(shndx);
192 return map != NULL && map->merge_map == merge_map;
195 // Initialize a mapping from input offsets to output addresses.
197 template<int size>
198 void
199 Object_merge_map::initialize_input_to_output_map(
200 unsigned int shndx,
201 typename elfcpp::Elf_types<size>::Elf_Addr starting_address,
202 Unordered_map<section_offset_type,
203 typename elfcpp::Elf_types<size>::Elf_Addr>* initialize_map)
205 Input_merge_map* map = this->get_input_merge_map(shndx);
206 gold_assert(map != NULL);
208 gold_assert(initialize_map->empty());
209 // We know how many entries we are going to add.
210 // reserve_unordered_map takes an expected count of buckets, not a
211 // count of elements, so double it to try to reduce collisions.
212 reserve_unordered_map(initialize_map, map->entries.size() * 2);
214 for (Input_merge_map::Entries::const_iterator p = map->entries.begin();
215 p != map->entries.end();
216 ++p)
218 section_offset_type output_offset = p->output_offset;
219 if (output_offset != -1)
220 output_offset += starting_address;
221 else
223 // If we see a relocation against an address we have chosen
224 // to discard, we relocate to zero. FIXME: We could also
225 // issue a warning in this case; that would require
226 // reporting this somehow and checking it in the routines in
227 // reloc.h.
228 output_offset = 0;
230 initialize_map->insert(std::make_pair(p->input_offset, output_offset));
234 // Class Merge_map.
236 // Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in input
237 // section SHNDX in object OBJECT to an OUTPUT_OFFSET in merged data
238 // in an output section.
240 void
241 Merge_map::add_mapping(Relobj* object, unsigned int shndx,
242 section_offset_type offset, section_size_type length,
243 section_offset_type output_offset)
245 gold_assert(object != NULL);
246 Object_merge_map* object_merge_map = object->merge_map();
247 if (object_merge_map == NULL)
249 object_merge_map = new Object_merge_map();
250 object->set_merge_map(object_merge_map);
253 object_merge_map->add_mapping(this, shndx, offset, length, output_offset);
256 // Return the output offset for an input address. The input address
257 // is at offset OFFSET in section SHNDX in OBJECT. This sets
258 // *OUTPUT_OFFSET to the offset in the merged data in the output
259 // section. This returns true if the mapping is known, false
260 // otherwise.
262 bool
263 Merge_map::get_output_offset(const Relobj* object, unsigned int shndx,
264 section_offset_type offset,
265 section_offset_type* output_offset) const
267 Object_merge_map* object_merge_map = object->merge_map();
268 if (object_merge_map == NULL)
269 return false;
270 return object_merge_map->get_output_offset(this, shndx, offset,
271 output_offset);
274 // Return whether this is the merge section for SHNDX in OBJECT.
276 bool
277 Merge_map::is_merge_section_for(const Relobj* object, unsigned int shndx) const
279 Object_merge_map* object_merge_map = object->merge_map();
280 if (object_merge_map == NULL)
281 return false;
282 return object_merge_map->is_merge_section_for(this, shndx);
285 // Class Output_merge_base.
287 // Return the output offset for an input offset. The input address is
288 // at offset OFFSET in section SHNDX in OBJECT. If we know the
289 // offset, set *POUTPUT and return true. Otherwise return false.
291 bool
292 Output_merge_base::do_output_offset(const Relobj* object,
293 unsigned int shndx,
294 section_offset_type offset,
295 section_offset_type* poutput) const
297 return this->merge_map_.get_output_offset(object, shndx, offset, poutput);
300 // Return whether this is the merge section for SHNDX in OBJECT.
302 bool
303 Output_merge_base::do_is_merge_section_for(const Relobj* object,
304 unsigned int shndx) const
306 return this->merge_map_.is_merge_section_for(object, shndx);
309 // Record a merged input section for script processing.
311 void
312 Output_merge_base::record_input_section(Relobj* relobj, unsigned int shndx)
314 gold_assert(this->keeps_input_sections_ && relobj != NULL);
315 // If this is the first input section, record it. We need do this because
316 // this->input_sections_ is unordered.
317 if (this->first_relobj_ == NULL)
319 this->first_relobj_ = relobj;
320 this->first_shndx_ = shndx;
323 std::pair<Input_sections::iterator, bool> result =
324 this->input_sections_.insert(Section_id(relobj, shndx));
325 // We should insert a merge section once only.
326 gold_assert(result.second);
329 // Class Output_merge_data.
331 // Compute the hash code for a fixed-size constant.
333 size_t
334 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
336 const unsigned char* p = this->pomd_->constant(k);
337 section_size_type entsize =
338 convert_to_section_size_type(this->pomd_->entsize());
340 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
341 if (sizeof(size_t) == 8)
343 size_t result = static_cast<size_t>(14695981039346656037ULL);
344 for (section_size_type i = 0; i < entsize; ++i)
346 result &= (size_t) *p++;
347 result *= 1099511628211ULL;
349 return result;
351 else
353 size_t result = 2166136261UL;
354 for (section_size_type i = 0; i < entsize; ++i)
356 result ^= (size_t) *p++;
357 result *= 16777619UL;
359 return result;
363 // Return whether one hash table key equals another.
365 bool
366 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
367 Merge_data_key k2) const
369 const unsigned char* p1 = this->pomd_->constant(k1);
370 const unsigned char* p2 = this->pomd_->constant(k2);
371 return memcmp(p1, p2, this->pomd_->entsize()) == 0;
374 // Add a constant to the end of the section contents.
376 void
377 Output_merge_data::add_constant(const unsigned char* p)
379 section_size_type entsize = convert_to_section_size_type(this->entsize());
380 section_size_type addralign =
381 convert_to_section_size_type(this->addralign());
382 section_size_type addsize = std::max(entsize, addralign);
383 if (this->len_ + addsize > this->alc_)
385 if (this->alc_ == 0)
386 this->alc_ = 128 * addsize;
387 else
388 this->alc_ *= 2;
389 this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
390 if (this->p_ == NULL)
391 gold_nomem();
394 memcpy(this->p_ + this->len_, p, entsize);
395 if (addsize > entsize)
396 memset(this->p_ + this->len_ + entsize, 0, addsize - entsize);
397 this->len_ += addsize;
400 // Add the input section SHNDX in OBJECT to a merged output section
401 // which holds fixed length constants. Return whether we were able to
402 // handle the section; if not, it will be linked as usual without
403 // constant merging.
405 bool
406 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
408 section_size_type len;
409 section_size_type uncompressed_size = 0;
410 unsigned char* uncompressed_data = NULL;
411 const unsigned char* p = object->section_contents(shndx, &len, false);
413 if (object->section_is_compressed(shndx, &uncompressed_size))
415 uncompressed_data = new unsigned char[uncompressed_size];
416 if (!decompress_input_section(p, len, uncompressed_data,
417 uncompressed_size))
418 object->error(_("could not decompress section %s"),
419 object->section_name(shndx).c_str());
420 p = uncompressed_data;
421 len = uncompressed_size;
424 section_size_type entsize = convert_to_section_size_type(this->entsize());
426 if (len % entsize != 0)
428 if (uncompressed_data != NULL)
429 delete[] uncompressed_data;
430 return false;
433 this->input_count_ += len / entsize;
435 for (section_size_type i = 0; i < len; i += entsize, p += entsize)
437 // Add the constant to the section contents. If we find that it
438 // is already in the hash table, we will remove it again.
439 Merge_data_key k = this->len_;
440 this->add_constant(p);
442 std::pair<Merge_data_hashtable::iterator, bool> ins =
443 this->hashtable_.insert(k);
445 if (!ins.second)
447 // Key was already present. Remove the copy we just added.
448 this->len_ -= entsize;
449 k = *ins.first;
452 // Record the offset of this constant in the output section.
453 this->add_mapping(object, shndx, i, entsize, k);
456 // For script processing, we keep the input sections.
457 if (this->keeps_input_sections())
458 record_input_section(object, shndx);
460 if (uncompressed_data != NULL)
461 delete[] uncompressed_data;
463 return true;
466 // Set the final data size in a merged output section with fixed size
467 // constants.
469 void
470 Output_merge_data::set_final_data_size()
472 // Release the memory we don't need.
473 this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
474 // An Output_merge_data object may be empty and realloc is allowed
475 // to return a NULL pointer in this case. An Output_merge_data is empty
476 // if all its input sections have sizes that are not multiples of entsize.
477 gold_assert(this->p_ != NULL || this->len_ == 0);
478 this->set_data_size(this->len_);
481 // Write the data of a merged output section with fixed size constants
482 // to the file.
484 void
485 Output_merge_data::do_write(Output_file* of)
487 of->write(this->offset(), this->p_, this->len_);
490 // Write the data to a buffer.
492 void
493 Output_merge_data::do_write_to_buffer(unsigned char* buffer)
495 memcpy(buffer, this->p_, this->len_);
498 // Print merge stats to stderr.
500 void
501 Output_merge_data::do_print_merge_stats(const char* section_name)
503 fprintf(stderr,
504 _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),
505 program_name, section_name,
506 static_cast<unsigned long>(this->entsize()),
507 this->input_count_, this->hashtable_.size());
510 // Class Output_merge_string.
512 // Add an input section to a merged string section.
514 template<typename Char_type>
515 bool
516 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
517 unsigned int shndx)
519 section_size_type len;
520 section_size_type uncompressed_size = 0;
521 unsigned char* uncompressed_data = NULL;
522 const unsigned char* pdata = object->section_contents(shndx, &len, false);
524 if (object->section_is_compressed(shndx, &uncompressed_size))
526 uncompressed_data = new unsigned char[uncompressed_size];
527 if (!decompress_input_section(pdata, len, uncompressed_data,
528 uncompressed_size))
529 object->error(_("could not decompress section %s"),
530 object->section_name(shndx).c_str());
531 pdata = uncompressed_data;
532 len = uncompressed_size;
535 const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
536 const Char_type* pend = p + len / sizeof(Char_type);
537 const Char_type* pend0 = pend;
539 if (len % sizeof(Char_type) != 0)
541 object->error(_("mergeable string section length not multiple of "
542 "character size"));
543 if (uncompressed_data != NULL)
544 delete[] uncompressed_data;
545 return false;
548 if (pend[-1] != 0)
550 gold_warning(_("%s: last entry in mergeable string section '%s' "
551 "not null terminated"),
552 object->name().c_str(),
553 object->section_name(shndx).c_str());
554 // Find the end of the last NULL-terminated string in the buffer.
555 while (pend0 > p && pend0[-1] != 0)
556 --pend0;
559 Merged_strings_list* merged_strings_list =
560 new Merged_strings_list(object, shndx);
561 this->merged_strings_lists_.push_back(merged_strings_list);
562 Merged_strings& merged_strings = merged_strings_list->merged_strings;
564 // Count the number of strings in the section and size the list.
565 size_t count = 0;
566 for (const Char_type* pt = p; pt < pend0; pt += string_length(pt) + 1)
567 ++count;
568 if (pend0 < pend)
569 ++count;
570 merged_strings.reserve(count + 1);
572 // The index I is in bytes, not characters.
573 section_size_type i = 0;
574 while (p < pend0)
576 size_t len = string_length(p);
578 Stringpool::Key key;
579 this->stringpool_.add_with_length(p, len, true, &key);
581 merged_strings.push_back(Merged_string(i, key));
583 p += len + 1;
584 i += (len + 1) * sizeof(Char_type);
586 if (p < pend)
588 size_t len = pend - p;
590 Stringpool::Key key;
591 this->stringpool_.add_with_length(p, len, true, &key);
593 merged_strings.push_back(Merged_string(i, key));
595 i += (len + 1) * sizeof(Char_type);
598 // Record the last offset in the input section so that we can
599 // compute the length of the last string.
600 merged_strings.push_back(Merged_string(i, 0));
602 this->input_count_ += count;
603 this->input_size_ += len;
605 // For script processing, we keep the input sections.
606 if (this->keeps_input_sections())
607 record_input_section(object, shndx);
609 if (uncompressed_data != NULL)
610 delete[] uncompressed_data;
612 return true;
615 // Finalize the mappings from the input sections to the output
616 // section, and return the final data size.
618 template<typename Char_type>
619 section_size_type
620 Output_merge_string<Char_type>::finalize_merged_data()
622 this->stringpool_.set_string_offsets();
624 for (typename Merged_strings_lists::const_iterator l =
625 this->merged_strings_lists_.begin();
626 l != this->merged_strings_lists_.end();
627 ++l)
629 section_offset_type last_input_offset = 0;
630 section_offset_type last_output_offset = 0;
631 for (typename Merged_strings::const_iterator p =
632 (*l)->merged_strings.begin();
633 p != (*l)->merged_strings.end();
634 ++p)
636 section_size_type length = p->offset - last_input_offset;
637 if (length > 0)
638 this->add_mapping((*l)->object, (*l)->shndx, last_input_offset,
639 length, last_output_offset);
640 last_input_offset = p->offset;
641 if (p->stringpool_key != 0)
642 last_output_offset =
643 this->stringpool_.get_offset_from_key(p->stringpool_key);
645 delete *l;
648 // Save some memory. This also ensures that this function will work
649 // if called twice, as may happen if Layout::set_segment_offsets
650 // finds a better alignment.
651 this->merged_strings_lists_.clear();
653 return this->stringpool_.get_strtab_size();
656 template<typename Char_type>
657 void
658 Output_merge_string<Char_type>::set_final_data_size()
660 const off_t final_data_size = this->finalize_merged_data();
661 this->set_data_size(final_data_size);
664 // Write out a merged string section.
666 template<typename Char_type>
667 void
668 Output_merge_string<Char_type>::do_write(Output_file* of)
670 this->stringpool_.write(of, this->offset());
673 // Write a merged string section to a buffer.
675 template<typename Char_type>
676 void
677 Output_merge_string<Char_type>::do_write_to_buffer(unsigned char* buffer)
679 this->stringpool_.write_to_buffer(buffer, this->data_size());
682 // Return the name of the types of string to use with
683 // do_print_merge_stats.
685 template<typename Char_type>
686 const char*
687 Output_merge_string<Char_type>::string_name()
689 gold_unreachable();
690 return NULL;
693 template<>
694 const char*
695 Output_merge_string<char>::string_name()
697 return "strings";
700 template<>
701 const char*
702 Output_merge_string<uint16_t>::string_name()
704 return "16-bit strings";
707 template<>
708 const char*
709 Output_merge_string<uint32_t>::string_name()
711 return "32-bit strings";
714 // Print merge stats to stderr.
716 template<typename Char_type>
717 void
718 Output_merge_string<Char_type>::do_print_merge_stats(const char* section_name)
720 char buf[200];
721 snprintf(buf, sizeof buf, "%s merged %s", section_name, this->string_name());
722 fprintf(stderr, _("%s: %s input bytes: %zu\n"),
723 program_name, buf, this->input_size_);
724 fprintf(stderr, _("%s: %s input strings: %zu\n"),
725 program_name, buf, this->input_count_);
726 this->stringpool_.print_stats(buf);
729 // Instantiate the templates we need.
731 template
732 class Output_merge_string<char>;
734 template
735 class Output_merge_string<uint16_t>;
737 template
738 class Output_merge_string<uint32_t>;
740 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
741 template
742 void
743 Object_merge_map::initialize_input_to_output_map<32>(
744 unsigned int shndx,
745 elfcpp::Elf_types<32>::Elf_Addr starting_address,
746 Unordered_map<section_offset_type, elfcpp::Elf_types<32>::Elf_Addr>*);
747 #endif
749 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
750 template
751 void
752 Object_merge_map::initialize_input_to_output_map<64>(
753 unsigned int shndx,
754 elfcpp::Elf_types<64>::Elf_Addr starting_address,
755 Unordered_map<section_offset_type, elfcpp::Elf_types<64>::Elf_Addr>*);
756 #endif
758 } // End namespace gold.