gold/merge.cc

   1 // merge.cc -- handle section merging for gold
   2
   3 // Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   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.
  12
  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.
  17
  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.
  22
  23 #include "gold.h"
  24
  25 #include <cstdlib>
  26 #include <algorithm>
  27
  28 #include "merge.h"
  29
  30 namespace gold
  31 {
  32
  33 // Class Object_merge_map.
  34
  35 // Destructor.
  36
  37 Object_merge_map::~Object_merge_map()
  38 {
  39   for (Section_merge_maps::iterator p = this->section_merge_maps_.begin();
  40        p != this->section_merge_maps_.end();
  41        ++p)
  42     delete p->second;
  43 }
  44
  45 // Get the Input_merge_map to use for an input section, or NULL.
  46
  47 Object_merge_map::Input_merge_map*
  48 Object_merge_map::get_input_merge_map(unsigned int shndx)
  49 {
  50   gold_assert(shndx != -1U);
  51   if (shndx == this->first_shnum_)
  52     return &this->first_map_;
  53   if (shndx == this->second_shnum_)
  54     return &this->second_map_;
  55   Section_merge_maps::const_iterator p = this->section_merge_maps_.find(shndx);
  56   if (p != this->section_merge_maps_.end())
  57     return p->second;
  58   return NULL;
  59 }
  60
  61 // Get or create the Input_merge_map to use for an input section.
  62
  63 Object_merge_map::Input_merge_map*
  64 Object_merge_map::get_or_make_input_merge_map(const Merge_map* merge_map,
  65                                               unsigned int shndx)
  66 {
  67   Input_merge_map* map = this->get_input_merge_map(shndx);
  68   if (map != NULL)
  69     {
  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->merge_map == merge_map);
  73       return map;
  74     }
  75
  76   // We need to create a new entry.
  77   if (this->first_shnum_ == -1U)
  78     {
  79       this->first_shnum_ = shndx;
  80       this->first_map_.merge_map = merge_map;
  81       return &this->first_map_;
  82     }
  83   if (this->second_shnum_ == -1U)
  84     {
  85       this->second_shnum_ = shndx;
  86       this->second_map_.merge_map = merge_map;
  87       return &this->second_map_;
  88     }
  89
  90   Input_merge_map* new_map = new Input_merge_map;
  91   new_map->merge_map = merge_map;
  92   this->section_merge_maps_[shndx] = new_map;
  93   return new_map;
  94 }
  95
  96 // Add a mapping.
  97
  98 void
  99 Object_merge_map::add_mapping(const Merge_map* merge_map, unsigned int shndx,
 100                               section_offset_type input_offset,
 101                               section_size_type length,
 102                               section_offset_type output_offset)
 103 {
 104   Input_merge_map* map = this->get_or_make_input_merge_map(merge_map, shndx);
 105
 106   // Try to merge the new entry in the last one we saw.
 107   if (!map->entries.empty())
 108     {
 109       Input_merge_entry& entry(map->entries.back());
 110
 111       // Use section_size_type to avoid signed/unsigned warnings.
 112       section_size_type input_offset_u = input_offset;
 113       section_size_type output_offset_u = output_offset;
 114
 115       // If this entry is not in order, we need to sort the vector
 116       // before looking anything up.
 117       if (input_offset_u < entry.input_offset + entry.length)
 118         {
 119           gold_assert(input_offset < entry.input_offset);
 120           gold_assert(input_offset_u + length
 121                       <= static_cast<section_size_type>(entry.input_offset));
 122           map->sorted = false;
 123         }
 124       else if (entry.input_offset + entry.length == input_offset_u
 125                && (output_offset == -1
 126                    ? entry.output_offset == -1
 127                    : entry.output_offset + entry.length == output_offset_u))
 128         {
 129           entry.length += length;
 130           return;
 131         }
 132     }
 133
 134   Input_merge_entry entry;
 135   entry.input_offset = input_offset;
 136   entry.length = length;
 137   entry.output_offset = output_offset;
 138   map->entries.push_back(entry);
 139 }
 140
 141 // Get the output offset for an input address.
 142
 143 inline bool
 144 Object_merge_map::get_output_offset(const Merge_map* merge_map,
 145                                     unsigned int shndx,
 146                                     section_offset_type input_offset,
 147                                     section_offset_type *output_offset)
 148 {
 149   Input_merge_map* map = this->get_input_merge_map(shndx);
 150   if (map == NULL
 151       || (merge_map != NULL && map->merge_map != merge_map))
 152     return false;
 153
 154   if (!map->sorted)
 155     {
 156       std::sort(map->entries.begin(), map->entries.end(),
 157                 Input_merge_compare());
 158       map->sorted = true;
 159     }
 160
 161   Input_merge_entry entry;
 162   entry.input_offset = input_offset;
 163   std::vector<Input_merge_entry>::const_iterator p =
 164     std::lower_bound(map->entries.begin(), map->entries.end(),
 165                      entry, Input_merge_compare());
 166   if (p == map->entries.end() || p->input_offset > input_offset)
 167     {
 168       if (p == map->entries.begin())
 169         return false;
 170       --p;
 171       gold_assert(p->input_offset <= input_offset);
 172     }
 173
 174   if (input_offset - p->input_offset
 175       >= static_cast<section_offset_type>(p->length))
 176     return false;
 177
 178   *output_offset = p->output_offset;
 179   if (*output_offset != -1)
 180     *output_offset += (input_offset - p->input_offset);
 181   return true;
 182 }
 183
 184 // Return whether this is the merge map for section SHNDX.
 185
 186 inline bool
 187 Object_merge_map::is_merge_section_for(const Merge_map* merge_map,
 188                                        unsigned int shndx)
 189 {
 190   Input_merge_map* map = this->get_input_merge_map(shndx);
 191   return map != NULL && map->merge_map == merge_map;
 192 }
 193
 194 // Initialize a mapping from input offsets to output addresses.
 195
 196 template<int size>
 197 void
 198 Object_merge_map::initialize_input_to_output_map(
 199     unsigned int shndx,
 200     typename elfcpp::Elf_types<size>::Elf_Addr starting_address,
 201     Unordered_map<section_offset_type,
 202                   typename elfcpp::Elf_types<size>::Elf_Addr>* initialize_map)
 203 {
 204   Input_merge_map* map = this->get_input_merge_map(shndx);
 205   gold_assert(map != NULL);
 206
 207   for (Input_merge_map::Entries::const_iterator p = map->entries.begin();
 208        p != map->entries.end();
 209        ++p)
 210     {
 211       section_offset_type output_offset = p->output_offset;
 212       if (output_offset != -1)
 213         output_offset += starting_address;
 214       else
 215         {
 216           // If we see a relocation against an address we have chosen
 217           // to discard, we relocate to zero.  FIXME: We could also
 218           // issue a warning in this case; that would require
 219           // reporting this somehow and checking it in the routines in
 220           // reloc.h.
 221           output_offset = 0;
 222         }
 223       initialize_map->insert(std::make_pair(p->input_offset, output_offset));
 224     }
 225 }
 226
 227 // Class Merge_map.
 228
 229 // Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in input
 230 // section SHNDX in object OBJECT to an OUTPUT_OFFSET in merged data
 231 // in an output section.
 232
 233 void
 234 Merge_map::add_mapping(Relobj* object, unsigned int shndx,
 235                        section_offset_type offset, section_size_type length,
 236                        section_offset_type output_offset)
 237 {
 238   Object_merge_map* object_merge_map = object->merge_map();
 239   if (object_merge_map == NULL)
 240     {
 241       object_merge_map = new Object_merge_map();
 242       object->set_merge_map(object_merge_map);
 243     }
 244
 245   object_merge_map->add_mapping(this, shndx, offset, length, output_offset);
 246 }
 247
 248 // Return the output offset for an input address.  The input address
 249 // is at offset OFFSET in section SHNDX in OBJECT.  This sets
 250 // *OUTPUT_OFFSET to the offset in the merged data in the output
 251 // section.  This returns true if the mapping is known, false
 252 // otherwise.
 253
 254 bool
 255 Merge_map::get_output_offset(const Relobj* object, unsigned int shndx,
 256                              section_offset_type offset,
 257                              section_offset_type* output_offset) const
 258 {
 259   Object_merge_map* object_merge_map = object->merge_map();
 260   if (object_merge_map == NULL)
 261     return false;
 262   return object_merge_map->get_output_offset(this, shndx, offset,
 263                                              output_offset);
 264 }
 265
 266 // Return whether this is the merge section for SHNDX in OBJECT.
 267
 268 bool
 269 Merge_map::is_merge_section_for(const Relobj* object, unsigned int shndx) const
 270 {
 271   Object_merge_map* object_merge_map = object->merge_map();
 272   if (object_merge_map == NULL)
 273     return false;
 274   return object_merge_map->is_merge_section_for(this, shndx);
 275 }
 276
 277 // Class Output_merge_base.
 278
 279 // Return the output offset for an input offset.  The input address is
 280 // at offset OFFSET in section SHNDX in OBJECT.  If we know the
 281 // offset, set *POUTPUT and return true.  Otherwise return false.
 282
 283 bool
 284 Output_merge_base::do_output_offset(const Relobj* object,
 285                                     unsigned int shndx,
 286                                     section_offset_type offset,
 287                                     section_offset_type* poutput) const
 288 {
 289   return this->merge_map_.get_output_offset(object, shndx, offset, poutput);
 290 }
 291
 292 // Return whether this is the merge section for SHNDX in OBJECT.
 293
 294 bool
 295 Output_merge_base::do_is_merge_section_for(const Relobj* object,
 296                                            unsigned int shndx) const
 297 {
 298   return this->merge_map_.is_merge_section_for(object, shndx);
 299 }
 300
 301 // Class Output_merge_data.
 302
 303 // Compute the hash code for a fixed-size constant.
 304
 305 size_t
 306 Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const
 307 {
 308   const unsigned char* p = this->pomd_->constant(k);
 309   section_size_type entsize =
 310     convert_to_section_size_type(this->pomd_->entsize());
 311
 312   // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
 313   if (sizeof(size_t) == 8)
 314     {
 315       size_t result = static_cast<size_t>(14695981039346656037ULL);
 316       for (section_size_type i = 0; i < entsize; ++i)
 317         {
 318           result &= (size_t) *p++;
 319           result *= 1099511628211ULL;
 320         }
 321       return result;
 322     }
 323   else
 324     {
 325       size_t result = 2166136261UL;
 326       for (section_size_type i = 0; i < entsize; ++i)
 327         {
 328           result ^= (size_t) *p++;
 329           result *= 16777619UL;
 330         }
 331       return result;
 332     }
 333 }
 334
 335 // Return whether one hash table key equals another.
 336
 337 bool
 338 Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,
 339                                              Merge_data_key k2) const
 340 {
 341   const unsigned char* p1 = this->pomd_->constant(k1);
 342   const unsigned char* p2 = this->pomd_->constant(k2);
 343   return memcmp(p1, p2, this->pomd_->entsize()) == 0;
 344 }
 345
 346 // Add a constant to the end of the section contents.
 347
 348 void
 349 Output_merge_data::add_constant(const unsigned char* p)
 350 {
 351   section_size_type entsize = convert_to_section_size_type(this->entsize());
 352   section_size_type addralign =
 353     convert_to_section_size_type(this->addralign());
 354   section_size_type addsize = std::max(entsize, addralign);
 355   if (this->len_ + addsize > this->alc_)
 356     {
 357       if (this->alc_ == 0)
 358         this->alc_ = 128 * addsize;
 359       else
 360         this->alc_ *= 2;
 361       this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));
 362       if (this->p_ == NULL)
 363         gold_nomem();
 364     }
 365
 366   memcpy(this->p_ + this->len_, p, entsize);
 367   if (addsize > entsize)
 368     memset(this->p_ + this->len_ + entsize, 0, addsize - entsize);
 369   this->len_ += addsize;
 370 }
 371
 372 // Add the input section SHNDX in OBJECT to a merged output section
 373 // which holds fixed length constants.  Return whether we were able to
 374 // handle the section; if not, it will be linked as usual without
 375 // constant merging.
 376
 377 bool
 378 Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)
 379 {
 380   section_size_type len;
 381   const unsigned char* p = object->section_contents(shndx, &len, false);
 382
 383   section_size_type entsize = convert_to_section_size_type(this->entsize());
 384
 385   if (len % entsize != 0)
 386     return false;
 387
 388   this->input_count_ += len / entsize;
 389
 390   for (section_size_type i = 0; i < len; i += entsize, p += entsize)
 391     {
 392       // Add the constant to the section contents.  If we find that it
 393       // is already in the hash table, we will remove it again.
 394       Merge_data_key k = this->len_;
 395       this->add_constant(p);
 396
 397       std::pair<Merge_data_hashtable::iterator, bool> ins =
 398         this->hashtable_.insert(k);
 399
 400       if (!ins.second)
 401         {
 402           // Key was already present.  Remove the copy we just added.
 403           this->len_ -= entsize;
 404           k = *ins.first;
 405         }
 406
 407       // Record the offset of this constant in the output section.
 408       this->add_mapping(object, shndx, i, entsize, k);
 409     }
 410
 411   return true;
 412 }
 413
 414 // Set the final data size in a merged output section with fixed size
 415 // constants.
 416
 417 void
 418 Output_merge_data::set_final_data_size()
 419 {
 420   // Release the memory we don't need.
 421   this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));
 422   gold_assert(this->p_ != NULL);
 423   this->set_data_size(this->len_);
 424 }
 425
 426 // Write the data of a merged output section with fixed size constants
 427 // to the file.
 428
 429 void
 430 Output_merge_data::do_write(Output_file* of)
 431 {
 432   of->write(this->offset(), this->p_, this->len_);
 433 }
 434
 435 // Write the data to a buffer.
 436
 437 void
 438 Output_merge_data::do_write_to_buffer(unsigned char* buffer)
 439 {
 440   memcpy(buffer, this->p_, this->len_);
 441 }
 442
 443 // Print merge stats to stderr.
 444
 445 void
 446 Output_merge_data::do_print_merge_stats(const char* section_name)
 447 {
 448   fprintf(stderr,
 449           _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),
 450           program_name, section_name,
 451           static_cast<unsigned long>(this->entsize()),
 452           this->input_count_, this->hashtable_.size());
 453 }
 454
 455 // Class Output_merge_string.
 456
 457 // Add an input section to a merged string section.
 458
 459 template<typename Char_type>
 460 bool
 461 Output_merge_string<Char_type>::do_add_input_section(Relobj* object,
 462                                                      unsigned int shndx)
 463 {
 464   section_size_type len;
 465   const unsigned char* pdata = object->section_contents(shndx, &len, false);
 466
 467   const Char_type* p = reinterpret_cast<const Char_type*>(pdata);
 468   const Char_type* pend = p + len;
 469
 470   if (len % sizeof(Char_type) != 0)
 471     {
 472       object->error(_("mergeable string section length not multiple of "
 473                       "character size"));
 474       return false;
 475     }
 476
 477   size_t count = 0;
 478
 479   // The index I is in bytes, not characters.
 480   section_size_type i = 0;
 481   while (i < len)
 482     {
 483       const Char_type* pl;
 484       for (pl = p; *pl != 0; ++pl)
 485         {
 486           if (pl >= pend)
 487             {
 488               object->error(_("entry in mergeable string section "
 489                               "not null terminated"));
 490               break;
 491             }
 492         }
 493
 494       Stringpool::Key key;
 495       const Char_type* str = this->stringpool_.add_with_length(p, pl - p, true,
 496                                                                &key);
 497
 498       section_size_type bytelen_with_null = ((pl - p) + 1) * sizeof(Char_type);
 499       this->merged_strings_.push_back(Merged_string(object, shndx, i, str,
 500                                                     bytelen_with_null, key));
 501
 502       p = pl + 1;
 503       i += bytelen_with_null;
 504       ++count;
 505     }
 506
 507   this->input_count_ += count;
 508
 509   return true;
 510 }
 511
 512 // Finalize the mappings from the input sections to the output
 513 // section, and return the final data size.
 514
 515 template<typename Char_type>
 516 section_size_type
 517 Output_merge_string<Char_type>::finalize_merged_data()
 518 {
 519   this->stringpool_.set_string_offsets();
 520
 521   for (typename Merged_strings::const_iterator p =
 522          this->merged_strings_.begin();
 523        p != this->merged_strings_.end();
 524        ++p)
 525     {
 526       section_offset_type offset =
 527         this->stringpool_.get_offset_from_key(p->stringpool_key);
 528       this->add_mapping(p->object, p->shndx, p->offset, p->length, offset);
 529     }
 530
 531   // Save some memory.  This also ensures that this function will work
 532   // if called twice, as may happen if Layout::set_segment_offsets
 533   // finds a better alignment.
 534   this->merged_strings_.clear();
 535
 536   return this->stringpool_.get_strtab_size();
 537 }
 538
 539 template<typename Char_type>
 540 void
 541 Output_merge_string<Char_type>::set_final_data_size()
 542 {
 543   const off_t final_data_size = this->finalize_merged_data();
 544   this->set_data_size(final_data_size);
 545 }
 546
 547 // Write out a merged string section.
 548
 549 template<typename Char_type>
 550 void
 551 Output_merge_string<Char_type>::do_write(Output_file* of)
 552 {
 553   this->stringpool_.write(of, this->offset());
 554 }
 555
 556 // Write a merged string section to a buffer.
 557
 558 template<typename Char_type>
 559 void
 560 Output_merge_string<Char_type>::do_write_to_buffer(unsigned char* buffer)
 561 {
 562   this->stringpool_.write_to_buffer(buffer, this->data_size());
 563 }
 564
 565 // Return the name of the types of string to use with
 566 // do_print_merge_stats.
 567
 568 template<typename Char_type>
 569 const char*
 570 Output_merge_string<Char_type>::string_name()
 571 {
 572   gold_unreachable();
 573   return NULL;
 574 }
 575
 576 template<>
 577 const char*
 578 Output_merge_string<char>::string_name()
 579 {
 580   return "strings";
 581 }
 582
 583 template<>
 584 const char*
 585 Output_merge_string<uint16_t>::string_name()
 586 {
 587   return "16-bit strings";
 588 }
 589
 590 template<>
 591 const char*
 592 Output_merge_string<uint32_t>::string_name()
 593 {
 594   return "32-bit strings";
 595 }
 596
 597 // Print merge stats to stderr.
 598
 599 template<typename Char_type>
 600 void
 601 Output_merge_string<Char_type>::do_print_merge_stats(const char* section_name)
 602 {
 603   char buf[200];
 604   snprintf(buf, sizeof buf, "%s merged %s", section_name, this->string_name());
 605   fprintf(stderr, _("%s: %s input: %zu\n"),
 606           program_name, buf, this->input_count_);
 607   this->stringpool_.print_stats(buf);
 608 }
 609
 610 // Instantiate the templates we need.
 611
 612 template
 613 class Output_merge_string<char>;
 614
 615 template
 616 class Output_merge_string<uint16_t>;
 617
 618 template
 619 class Output_merge_string<uint32_t>;
 620
 621 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 622 template
 623 void
 624 Object_merge_map::initialize_input_to_output_map<32>(
 625     unsigned int shndx,
 626     elfcpp::Elf_types<32>::Elf_Addr starting_address,
 627     Unordered_map<section_offset_type, elfcpp::Elf_types<32>::Elf_Addr>*);
 628 #endif
 629
 630 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 631 template
 632 void
 633 Object_merge_map::initialize_input_to_output_map<64>(
 634     unsigned int shndx,
 635     elfcpp::Elf_types<64>::Elf_Addr starting_address,
 636     Unordered_map<section_offset_type, elfcpp::Elf_types<64>::Elf_Addr>*);
 637 #endif
 638
 639 } // End namespace gold.