layout.h revision 1.1.1.2.8.1
1// layout.h -- lay out output file sections for gold -*- C++ -*- 2 3// Copyright 2006, 2007, 2008, 2009, 2010, 2011, 2012 4// Free Software Foundation, Inc. 5// Written by Ian Lance Taylor <iant@google.com>. 6 7// This file is part of gold. 8 9// This program is free software; you can redistribute it and/or modify 10// it under the terms of the GNU General Public License as published by 11// the Free Software Foundation; either version 3 of the License, or 12// (at your option) any later version. 13 14// This program is distributed in the hope that it will be useful, 15// but WITHOUT ANY WARRANTY; without even the implied warranty of 16// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 17// GNU General Public License for more details. 18 19// You should have received a copy of the GNU General Public License 20// along with this program; if not, write to the Free Software 21// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, 22// MA 02110-1301, USA. 23 24#ifndef GOLD_LAYOUT_H 25#define GOLD_LAYOUT_H 26 27#include <cstring> 28#include <list> 29#include <map> 30#include <string> 31#include <utility> 32#include <vector> 33 34#include "script.h" 35#include "workqueue.h" 36#include "object.h" 37#include "dynobj.h" 38#include "stringpool.h" 39 40namespace gold 41{ 42 43class General_options; 44class Incremental_inputs; 45class Incremental_binary; 46class Input_objects; 47class Mapfile; 48class Symbol_table; 49class Output_section_data; 50class Output_section; 51class Output_section_headers; 52class Output_segment_headers; 53class Output_file_header; 54class Output_segment; 55class Output_data; 56class Output_data_reloc_generic; 57class Output_data_dynamic; 58class Output_symtab_xindex; 59class Output_reduced_debug_abbrev_section; 60class Output_reduced_debug_info_section; 61class Eh_frame; 62class Gdb_index; 63class Target; 64struct Timespec; 65 66// Return TRUE if SECNAME is the name of a compressed debug section. 67extern bool 68is_compressed_debug_section(const char* secname); 69 70// Maintain a list of free space within a section, segment, or file. 71// Used for incremental update links. 72 73class Free_list 74{ 75 public: 76 struct Free_list_node 77 { 78 Free_list_node(off_t start, off_t end) 79 : start_(start), end_(end) 80 { } 81 off_t start_; 82 off_t end_; 83 }; 84 typedef std::list<Free_list_node>::const_iterator Const_iterator; 85 86 Free_list() 87 : list_(), last_remove_(list_.begin()), extend_(false), length_(0), 88 min_hole_(0) 89 { } 90 91 // Initialize the free list for a section of length LEN. 92 // If EXTEND is true, free space may be allocated past the end. 93 void 94 init(off_t len, bool extend); 95 96 // Set the minimum hole size that is allowed when allocating 97 // from the free list. 98 void 99 set_min_hole_size(off_t min_hole) 100 { this->min_hole_ = min_hole; } 101 102 // Remove a chunk from the free list. 103 void 104 remove(off_t start, off_t end); 105 106 // Allocate a chunk of space from the free list of length LEN, 107 // with alignment ALIGN, and minimum offset MINOFF. 108 off_t 109 allocate(off_t len, uint64_t align, off_t minoff); 110 111 // Return an iterator for the beginning of the free list. 112 Const_iterator 113 begin() const 114 { return this->list_.begin(); } 115 116 // Return an iterator for the end of the free list. 117 Const_iterator 118 end() const 119 { return this->list_.end(); } 120 121 // Dump the free list (for debugging). 122 void 123 dump(); 124 125 // Print usage statistics. 126 static void 127 print_stats(); 128 129 private: 130 typedef std::list<Free_list_node>::iterator Iterator; 131 132 // The free list. 133 std::list<Free_list_node> list_; 134 135 // The last node visited during a remove operation. 136 Iterator last_remove_; 137 138 // Whether we can extend past the original length. 139 bool extend_; 140 141 // The total length of the section, segment, or file. 142 off_t length_; 143 144 // The minimum hole size allowed. When allocating from the free list, 145 // we must not leave a hole smaller than this. 146 off_t min_hole_; 147 148 // Statistics: 149 // The total number of free lists used. 150 static unsigned int num_lists; 151 // The total number of free list nodes used. 152 static unsigned int num_nodes; 153 // The total number of calls to Free_list::remove. 154 static unsigned int num_removes; 155 // The total number of nodes visited during calls to Free_list::remove. 156 static unsigned int num_remove_visits; 157 // The total number of calls to Free_list::allocate. 158 static unsigned int num_allocates; 159 // The total number of nodes visited during calls to Free_list::allocate. 160 static unsigned int num_allocate_visits; 161}; 162 163// This task function handles mapping the input sections to output 164// sections and laying them out in memory. 165 166class Layout_task_runner : public Task_function_runner 167{ 168 public: 169 // OPTIONS is the command line options, INPUT_OBJECTS is the list of 170 // input objects, SYMTAB is the symbol table, LAYOUT is the layout 171 // object. 172 Layout_task_runner(const General_options& options, 173 const Input_objects* input_objects, 174 Symbol_table* symtab, 175 Target* target, 176 Layout* layout, 177 Mapfile* mapfile) 178 : options_(options), input_objects_(input_objects), symtab_(symtab), 179 target_(target), layout_(layout), mapfile_(mapfile) 180 { } 181 182 // Run the operation. 183 void 184 run(Workqueue*, const Task*); 185 186 private: 187 Layout_task_runner(const Layout_task_runner&); 188 Layout_task_runner& operator=(const Layout_task_runner&); 189 190 const General_options& options_; 191 const Input_objects* input_objects_; 192 Symbol_table* symtab_; 193 Target* target_; 194 Layout* layout_; 195 Mapfile* mapfile_; 196}; 197 198// This class holds information about the comdat group or 199// .gnu.linkonce section that will be kept for a given signature. 200 201class Kept_section 202{ 203 private: 204 // For a comdat group, we build a mapping from the name of each 205 // section in the group to the section index and the size in object. 206 // When we discard a group in some other object file, we use this 207 // map to figure out which kept section the discarded section is 208 // associated with. We then use that mapping when processing relocs 209 // against discarded sections. 210 struct Comdat_section_info 211 { 212 // The section index. 213 unsigned int shndx; 214 // The section size. 215 uint64_t size; 216 217 Comdat_section_info(unsigned int a_shndx, uint64_t a_size) 218 : shndx(a_shndx), size(a_size) 219 { } 220 }; 221 222 // Most comdat groups have only one or two sections, so we use a 223 // std::map rather than an Unordered_map to optimize for that case 224 // without paying too heavily for groups with more sections. 225 typedef std::map<std::string, Comdat_section_info> Comdat_group; 226 227 public: 228 Kept_section() 229 : object_(NULL), shndx_(0), is_comdat_(false), is_group_name_(false) 230 { this->u_.linkonce_size = 0; } 231 232 // We need to support copies for the signature map in the Layout 233 // object, but we should never copy an object after it has been 234 // marked as a comdat section. 235 Kept_section(const Kept_section& k) 236 : object_(k.object_), shndx_(k.shndx_), is_comdat_(false), 237 is_group_name_(k.is_group_name_) 238 { 239 gold_assert(!k.is_comdat_); 240 this->u_.linkonce_size = 0; 241 } 242 243 ~Kept_section() 244 { 245 if (this->is_comdat_) 246 delete this->u_.group_sections; 247 } 248 249 // The object where this section lives. 250 Relobj* 251 object() const 252 { return this->object_; } 253 254 // Set the object. 255 void 256 set_object(Relobj* object) 257 { 258 gold_assert(this->object_ == NULL); 259 this->object_ = object; 260 } 261 262 // The section index. 263 unsigned int 264 shndx() const 265 { return this->shndx_; } 266 267 // Set the section index. 268 void 269 set_shndx(unsigned int shndx) 270 { 271 gold_assert(this->shndx_ == 0); 272 this->shndx_ = shndx; 273 } 274 275 // Whether this is a comdat group. 276 bool 277 is_comdat() const 278 { return this->is_comdat_; } 279 280 // Set that this is a comdat group. 281 void 282 set_is_comdat() 283 { 284 gold_assert(!this->is_comdat_); 285 this->is_comdat_ = true; 286 this->u_.group_sections = new Comdat_group(); 287 } 288 289 // Whether this is associated with the name of a group or section 290 // rather than the symbol name derived from a linkonce section. 291 bool 292 is_group_name() const 293 { return this->is_group_name_; } 294 295 // Note that this represents a comdat group rather than a single 296 // linkonce section. 297 void 298 set_is_group_name() 299 { this->is_group_name_ = true; } 300 301 // Add a section to the group list. 302 void 303 add_comdat_section(const std::string& name, unsigned int shndx, 304 uint64_t size) 305 { 306 gold_assert(this->is_comdat_); 307 Comdat_section_info sinfo(shndx, size); 308 this->u_.group_sections->insert(std::make_pair(name, sinfo)); 309 } 310 311 // Look for a section name in the group list, and return whether it 312 // was found. If found, returns the section index and size. 313 bool 314 find_comdat_section(const std::string& name, unsigned int* pshndx, 315 uint64_t* psize) const 316 { 317 gold_assert(this->is_comdat_); 318 Comdat_group::const_iterator p = this->u_.group_sections->find(name); 319 if (p == this->u_.group_sections->end()) 320 return false; 321 *pshndx = p->second.shndx; 322 *psize = p->second.size; 323 return true; 324 } 325 326 // If there is only one section in the group list, return true, and 327 // return the section index and size. 328 bool 329 find_single_comdat_section(unsigned int* pshndx, uint64_t* psize) const 330 { 331 gold_assert(this->is_comdat_); 332 if (this->u_.group_sections->size() != 1) 333 return false; 334 Comdat_group::const_iterator p = this->u_.group_sections->begin(); 335 *pshndx = p->second.shndx; 336 *psize = p->second.size; 337 return true; 338 } 339 340 // Return the size of a linkonce section. 341 uint64_t 342 linkonce_size() const 343 { 344 gold_assert(!this->is_comdat_); 345 return this->u_.linkonce_size; 346 } 347 348 // Set the size of a linkonce section. 349 void 350 set_linkonce_size(uint64_t size) 351 { 352 gold_assert(!this->is_comdat_); 353 this->u_.linkonce_size = size; 354 } 355 356 private: 357 // No assignment. 358 Kept_section& operator=(const Kept_section&); 359 360 // The object containing the comdat group or .gnu.linkonce section. 361 Relobj* object_; 362 // Index of the group section for comdats and the section itself for 363 // .gnu.linkonce. 364 unsigned int shndx_; 365 // True if this is for a comdat group rather than a .gnu.linkonce 366 // section. 367 bool is_comdat_; 368 // The Kept_sections are values of a mapping, that maps names to 369 // them. This field is true if this struct is associated with the 370 // name of a comdat or .gnu.linkonce, false if it is associated with 371 // the name of a symbol obtained from the .gnu.linkonce.* name 372 // through some heuristics. 373 bool is_group_name_; 374 union 375 { 376 // If the is_comdat_ field is true, this holds a map from names of 377 // the sections in the group to section indexes in object_ and to 378 // section sizes. 379 Comdat_group* group_sections; 380 // If the is_comdat_ field is false, this holds the size of the 381 // single section. 382 uint64_t linkonce_size; 383 } u_; 384}; 385 386// The ordering for output sections. This controls how output 387// sections are ordered within a PT_LOAD output segment. 388 389enum Output_section_order 390{ 391 // Unspecified. Used for non-load segments. Also used for the file 392 // and segment headers. 393 ORDER_INVALID, 394 395 // The PT_INTERP section should come first, so that the dynamic 396 // linker can pick it up quickly. 397 ORDER_INTERP, 398 399 // Loadable read-only note sections come next so that the PT_NOTE 400 // segment is on the first page of the executable. 401 ORDER_RO_NOTE, 402 403 // Put read-only sections used by the dynamic linker early in the 404 // executable to minimize paging. 405 ORDER_DYNAMIC_LINKER, 406 407 // Put reloc sections used by the dynamic linker after other 408 // sections used by the dynamic linker; otherwise, objcopy and strip 409 // get confused. 410 ORDER_DYNAMIC_RELOCS, 411 412 // Put the PLT reloc section after the other dynamic relocs; 413 // otherwise, prelink gets confused. 414 ORDER_DYNAMIC_PLT_RELOCS, 415 416 // The .init section. 417 ORDER_INIT, 418 419 // The PLT. 420 ORDER_PLT, 421 422 // The regular text sections. 423 ORDER_TEXT, 424 425 // The .fini section. 426 ORDER_FINI, 427 428 // The read-only sections. 429 ORDER_READONLY, 430 431 // The exception frame sections. 432 ORDER_EHFRAME, 433 434 // The TLS sections come first in the data section. 435 ORDER_TLS_DATA, 436 ORDER_TLS_BSS, 437 438 // Local RELRO (read-only after relocation) sections come before 439 // non-local RELRO sections. This data will be fully resolved by 440 // the prelinker. 441 ORDER_RELRO_LOCAL, 442 443 // Non-local RELRO sections are grouped together after local RELRO 444 // sections. All RELRO sections must be adjacent so that they can 445 // all be put into a PT_GNU_RELRO segment. 446 ORDER_RELRO, 447 448 // We permit marking exactly one output section as the last RELRO 449 // section. We do this so that the read-only GOT can be adjacent to 450 // the writable GOT. 451 ORDER_RELRO_LAST, 452 453 // Similarly, we permit marking exactly one output section as the 454 // first non-RELRO section. 455 ORDER_NON_RELRO_FIRST, 456 457 // The regular data sections come after the RELRO sections. 458 ORDER_DATA, 459 460 // Large data sections normally go in large data segments. 461 ORDER_LARGE_DATA, 462 463 // Group writable notes so that we can have a single PT_NOTE 464 // segment. 465 ORDER_RW_NOTE, 466 467 // The small data sections must be at the end of the data sections, 468 // so that they can be adjacent to the small BSS sections. 469 ORDER_SMALL_DATA, 470 471 // The BSS sections start here. 472 473 // The small BSS sections must be at the start of the BSS sections, 474 // so that they can be adjacent to the small data sections. 475 ORDER_SMALL_BSS, 476 477 // The regular BSS sections. 478 ORDER_BSS, 479 480 // The large BSS sections come after the other BSS sections. 481 ORDER_LARGE_BSS, 482 483 // Maximum value. 484 ORDER_MAX 485}; 486 487// This class handles the details of laying out input sections. 488 489class Layout 490{ 491 public: 492 Layout(int number_of_input_files, Script_options*); 493 494 ~Layout() 495 { 496 delete this->relaxation_debug_check_; 497 delete this->segment_states_; 498 } 499 500 // For incremental links, record the base file to be modified. 501 void 502 set_incremental_base(Incremental_binary* base); 503 504 Incremental_binary* 505 incremental_base() 506 { return this->incremental_base_; } 507 508 // For incremental links, record the initial fixed layout of a section 509 // from the base file, and return a pointer to the Output_section. 510 template<int size, bool big_endian> 511 Output_section* 512 init_fixed_output_section(const char*, elfcpp::Shdr<size, big_endian>&); 513 514 // Given an input section SHNDX, named NAME, with data in SHDR, from 515 // the object file OBJECT, return the output section where this 516 // input section should go. RELOC_SHNDX is the index of a 517 // relocation section which applies to this section, or 0 if none, 518 // or -1U if more than one. RELOC_TYPE is the type of the 519 // relocation section if there is one. Set *OFFSET to the offset 520 // within the output section. 521 template<int size, bool big_endian> 522 Output_section* 523 layout(Sized_relobj_file<size, big_endian> *object, unsigned int shndx, 524 const char* name, const elfcpp::Shdr<size, big_endian>& shdr, 525 unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset); 526 527 std::map<Section_id, unsigned int>* 528 get_section_order_map() 529 { return &this->section_order_map_; } 530 531 bool 532 is_section_ordering_specified() 533 { return this->section_ordering_specified_; } 534 535 void 536 set_section_ordering_specified() 537 { this->section_ordering_specified_ = true; } 538 539 // For incremental updates, allocate a block of memory from the 540 // free list. Find a block starting at or after MINOFF. 541 off_t 542 allocate(off_t len, uint64_t align, off_t minoff) 543 { return this->free_list_.allocate(len, align, minoff); } 544 545 unsigned int 546 find_section_order_index(const std::string&); 547 548 // Read the sequence of input sections from the file specified with 549 // linker option --section-ordering-file. 550 void 551 read_layout_from_file(); 552 553 // Layout an input reloc section when doing a relocatable link. The 554 // section is RELOC_SHNDX in OBJECT, with data in SHDR. 555 // DATA_SECTION is the reloc section to which it refers. RR is the 556 // relocatable information. 557 template<int size, bool big_endian> 558 Output_section* 559 layout_reloc(Sized_relobj_file<size, big_endian>* object, 560 unsigned int reloc_shndx, 561 const elfcpp::Shdr<size, big_endian>& shdr, 562 Output_section* data_section, 563 Relocatable_relocs* rr); 564 565 // Layout a group section when doing a relocatable link. 566 template<int size, bool big_endian> 567 void 568 layout_group(Symbol_table* symtab, 569 Sized_relobj_file<size, big_endian>* object, 570 unsigned int group_shndx, 571 const char* group_section_name, 572 const char* signature, 573 const elfcpp::Shdr<size, big_endian>& shdr, 574 elfcpp::Elf_Word flags, 575 std::vector<unsigned int>* shndxes); 576 577 // Like layout, only for exception frame sections. OBJECT is an 578 // object file. SYMBOLS is the contents of the symbol table 579 // section, with size SYMBOLS_SIZE. SYMBOL_NAMES is the contents of 580 // the symbol name section, with size SYMBOL_NAMES_SIZE. SHNDX is a 581 // .eh_frame section in OBJECT. SHDR is the section header. 582 // RELOC_SHNDX is the index of a relocation section which applies to 583 // this section, or 0 if none, or -1U if more than one. RELOC_TYPE 584 // is the type of the relocation section if there is one. This 585 // returns the output section, and sets *OFFSET to the offset. 586 template<int size, bool big_endian> 587 Output_section* 588 layout_eh_frame(Sized_relobj_file<size, big_endian>* object, 589 const unsigned char* symbols, 590 off_t symbols_size, 591 const unsigned char* symbol_names, 592 off_t symbol_names_size, 593 unsigned int shndx, 594 const elfcpp::Shdr<size, big_endian>& shdr, 595 unsigned int reloc_shndx, unsigned int reloc_type, 596 off_t* offset); 597 598 // Add .eh_frame information for a PLT. The FDE must start with a 599 // 4-byte PC-relative reference to the start of the PLT, followed by 600 // a 4-byte size of PLT. 601 void 602 add_eh_frame_for_plt(Output_data* plt, const unsigned char* cie_data, 603 size_t cie_length, const unsigned char* fde_data, 604 size_t fde_length); 605 606 // Scan a .debug_info or .debug_types section, and add summary 607 // information to the .gdb_index section. 608 template<int size, bool big_endian> 609 void 610 add_to_gdb_index(bool is_type_unit, 611 Sized_relobj<size, big_endian>* object, 612 const unsigned char* symbols, 613 off_t symbols_size, 614 unsigned int shndx, 615 unsigned int reloc_shndx, 616 unsigned int reloc_type); 617 618 // Handle a GNU stack note. This is called once per input object 619 // file. SEEN_GNU_STACK is true if the object file has a 620 // .note.GNU-stack section. GNU_STACK_FLAGS is the section flags 621 // from that section if there was one. 622 void 623 layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags, 624 const Object*); 625 626 // Add an Output_section_data to the layout. This is used for 627 // special sections like the GOT section. ORDER is where the 628 // section should wind up in the output segment. IS_RELRO is true 629 // for relro sections. 630 Output_section* 631 add_output_section_data(const char* name, elfcpp::Elf_Word type, 632 elfcpp::Elf_Xword flags, 633 Output_section_data*, Output_section_order order, 634 bool is_relro); 635 636 // Increase the size of the relro segment by this much. 637 void 638 increase_relro(unsigned int s) 639 { this->increase_relro_ += s; } 640 641 // Create dynamic sections if necessary. 642 void 643 create_initial_dynamic_sections(Symbol_table*); 644 645 // Define __start and __stop symbols for output sections. 646 void 647 define_section_symbols(Symbol_table*); 648 649 // Create automatic note sections. 650 void 651 create_notes(); 652 653 // Create sections for linker scripts. 654 void 655 create_script_sections() 656 { this->script_options_->create_script_sections(this); } 657 658 // Define symbols from any linker script. 659 void 660 define_script_symbols(Symbol_table* symtab) 661 { this->script_options_->add_symbols_to_table(symtab); } 662 663 // Define symbols for group signatures. 664 void 665 define_group_signatures(Symbol_table*); 666 667 // Return the Stringpool used for symbol names. 668 const Stringpool* 669 sympool() const 670 { return &this->sympool_; } 671 672 // Return the Stringpool used for dynamic symbol names and dynamic 673 // tags. 674 const Stringpool* 675 dynpool() const 676 { return &this->dynpool_; } 677 678 // Return the .dynamic output section. This is only valid after the 679 // layout has been finalized. 680 Output_section* 681 dynamic_section() const 682 { return this->dynamic_section_; } 683 684 // Return the symtab_xindex section used to hold large section 685 // indexes for the normal symbol table. 686 Output_symtab_xindex* 687 symtab_xindex() const 688 { return this->symtab_xindex_; } 689 690 // Return the dynsym_xindex section used to hold large section 691 // indexes for the dynamic symbol table. 692 Output_symtab_xindex* 693 dynsym_xindex() const 694 { return this->dynsym_xindex_; } 695 696 // Return whether a section is a .gnu.linkonce section, given the 697 // section name. 698 static inline bool 699 is_linkonce(const char* name) 700 { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; } 701 702 // Whether we have added an input section. 703 bool 704 have_added_input_section() const 705 { return this->have_added_input_section_; } 706 707 // Return true if a section is a debugging section. 708 static inline bool 709 is_debug_info_section(const char* name) 710 { 711 // Debugging sections can only be recognized by name. 712 return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0 713 || strncmp(name, ".zdebug", sizeof(".zdebug") - 1) == 0 714 || strncmp(name, ".gnu.linkonce.wi.", 715 sizeof(".gnu.linkonce.wi.") - 1) == 0 716 || strncmp(name, ".line", sizeof(".line") - 1) == 0 717 || strncmp(name, ".stab", sizeof(".stab") - 1) == 0); 718 } 719 720 // Return true if RELOBJ is an input file whose base name matches 721 // FILE_NAME. The base name must have an extension of ".o", and 722 // must be exactly FILE_NAME.o or FILE_NAME, one character, ".o". 723 static bool 724 match_file_name(const Relobj* relobj, const char* file_name); 725 726 // Return whether section SHNDX in RELOBJ is a .ctors/.dtors section 727 // with more than one word being mapped to a .init_array/.fini_array 728 // section. 729 bool 730 is_ctors_in_init_array(Relobj* relobj, unsigned int shndx) const; 731 732 // Check if a comdat group or .gnu.linkonce section with the given 733 // NAME is selected for the link. If there is already a section, 734 // *KEPT_SECTION is set to point to the signature and the function 735 // returns false. Otherwise, OBJECT, SHNDX,IS_COMDAT, and 736 // IS_GROUP_NAME are recorded for this NAME in the layout object, 737 // *KEPT_SECTION is set to the internal copy and the function return 738 // false. 739 bool 740 find_or_add_kept_section(const std::string& name, Relobj* object, 741 unsigned int shndx, bool is_comdat, 742 bool is_group_name, Kept_section** kept_section); 743 744 // Finalize the layout after all the input sections have been added. 745 off_t 746 finalize(const Input_objects*, Symbol_table*, Target*, const Task*); 747 748 // Return whether any sections require postprocessing. 749 bool 750 any_postprocessing_sections() const 751 { return this->any_postprocessing_sections_; } 752 753 // Return the size of the output file. 754 off_t 755 output_file_size() const 756 { return this->output_file_size_; } 757 758 // Return the TLS segment. This will return NULL if there isn't 759 // one. 760 Output_segment* 761 tls_segment() const 762 { return this->tls_segment_; } 763 764 // Return the normal symbol table. 765 Output_section* 766 symtab_section() const 767 { 768 gold_assert(this->symtab_section_ != NULL); 769 return this->symtab_section_; 770 } 771 772 // Return the file offset of the normal symbol table. 773 off_t 774 symtab_section_offset() const; 775 776 // Return the section index of the normal symbol tabl.e 777 unsigned int 778 symtab_section_shndx() const; 779 780 // Return the dynamic symbol table. 781 Output_section* 782 dynsym_section() const 783 { 784 gold_assert(this->dynsym_section_ != NULL); 785 return this->dynsym_section_; 786 } 787 788 // Return the dynamic tags. 789 Output_data_dynamic* 790 dynamic_data() const 791 { return this->dynamic_data_; } 792 793 // Write out the output sections. 794 void 795 write_output_sections(Output_file* of) const; 796 797 // Write out data not associated with an input file or the symbol 798 // table. 799 void 800 write_data(const Symbol_table*, Output_file*) const; 801 802 // Write out output sections which can not be written until all the 803 // input sections are complete. 804 void 805 write_sections_after_input_sections(Output_file* of); 806 807 // Return an output section named NAME, or NULL if there is none. 808 Output_section* 809 find_output_section(const char* name) const; 810 811 // Return an output segment of type TYPE, with segment flags SET set 812 // and segment flags CLEAR clear. Return NULL if there is none. 813 Output_segment* 814 find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set, 815 elfcpp::Elf_Word clear) const; 816 817 // Return the number of segments we expect to produce. 818 size_t 819 expected_segment_count() const; 820 821 // Set a flag to indicate that an object file uses the static TLS model. 822 void 823 set_has_static_tls() 824 { this->has_static_tls_ = true; } 825 826 // Return true if any object file uses the static TLS model. 827 bool 828 has_static_tls() const 829 { return this->has_static_tls_; } 830 831 // Return the options which may be set by a linker script. 832 Script_options* 833 script_options() 834 { return this->script_options_; } 835 836 const Script_options* 837 script_options() const 838 { return this->script_options_; } 839 840 // Return the object managing inputs in incremental build. NULL in 841 // non-incremental builds. 842 Incremental_inputs* 843 incremental_inputs() const 844 { return this->incremental_inputs_; } 845 846 // For the target-specific code to add dynamic tags which are common 847 // to most targets. 848 void 849 add_target_dynamic_tags(bool use_rel, const Output_data* plt_got, 850 const Output_data* plt_rel, 851 const Output_data_reloc_generic* dyn_rel, 852 bool add_debug, bool dynrel_includes_plt); 853 854 // Compute and write out the build ID if needed. 855 void 856 write_build_id(Output_file*) const; 857 858 // Rewrite output file in binary format. 859 void 860 write_binary(Output_file* in) const; 861 862 // Print output sections to the map file. 863 void 864 print_to_mapfile(Mapfile*) const; 865 866 // Dump statistical information to stderr. 867 void 868 print_stats() const; 869 870 // A list of segments. 871 872 typedef std::vector<Output_segment*> Segment_list; 873 874 // A list of sections. 875 876 typedef std::vector<Output_section*> Section_list; 877 878 // The list of information to write out which is not attached to 879 // either a section or a segment. 880 typedef std::vector<Output_data*> Data_list; 881 882 // Store the allocated sections into the section list. This is used 883 // by the linker script code. 884 void 885 get_allocated_sections(Section_list*) const; 886 887 // Make a section for a linker script to hold data. 888 Output_section* 889 make_output_section_for_script(const char* name, 890 Script_sections::Section_type section_type); 891 892 // Make a segment. This is used by the linker script code. 893 Output_segment* 894 make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags); 895 896 // Return the number of segments. 897 size_t 898 segment_count() const 899 { return this->segment_list_.size(); } 900 901 // Map from section flags to segment flags. 902 static elfcpp::Elf_Word 903 section_flags_to_segment(elfcpp::Elf_Xword flags); 904 905 // Attach sections to segments. 906 void 907 attach_sections_to_segments(const Target*); 908 909 // For relaxation clean up, we need to know output section data created 910 // from a linker script. 911 void 912 new_output_section_data_from_script(Output_section_data* posd) 913 { 914 if (this->record_output_section_data_from_script_) 915 this->script_output_section_data_list_.push_back(posd); 916 } 917 918 // Return section list. 919 const Section_list& 920 section_list() const 921 { return this->section_list_; } 922 923 private: 924 Layout(const Layout&); 925 Layout& operator=(const Layout&); 926 927 // Mapping from input section names to output section names. 928 struct Section_name_mapping 929 { 930 const char* from; 931 int fromlen; 932 const char* to; 933 int tolen; 934 }; 935 static const Section_name_mapping section_name_mapping[]; 936 static const int section_name_mapping_count; 937 938 // During a relocatable link, a list of group sections and 939 // signatures. 940 struct Group_signature 941 { 942 // The group section. 943 Output_section* section; 944 // The signature. 945 const char* signature; 946 947 Group_signature() 948 : section(NULL), signature(NULL) 949 { } 950 951 Group_signature(Output_section* sectiona, const char* signaturea) 952 : section(sectiona), signature(signaturea) 953 { } 954 }; 955 typedef std::vector<Group_signature> Group_signatures; 956 957 // Create a note section, filling in the header. 958 Output_section* 959 create_note(const char* name, int note_type, const char* section_name, 960 size_t descsz, bool allocate, size_t* trailing_padding); 961 962 // Create a note section for gold version. 963 void 964 create_gold_note(); 965 966 // Record whether the stack must be executable. 967 void 968 create_executable_stack_info(); 969 970 // Create a build ID note if needed. 971 void 972 create_build_id(); 973 974 // Link .stab and .stabstr sections. 975 void 976 link_stabs_sections(); 977 978 // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed 979 // for the next run of incremental linking to check what has changed. 980 void 981 create_incremental_info_sections(Symbol_table*); 982 983 // Find the first read-only PT_LOAD segment, creating one if 984 // necessary. 985 Output_segment* 986 find_first_load_seg(const Target*); 987 988 // Count the local symbols in the regular symbol table and the dynamic 989 // symbol table, and build the respective string pools. 990 void 991 count_local_symbols(const Task*, const Input_objects*); 992 993 // Create the output sections for the symbol table. 994 void 995 create_symtab_sections(const Input_objects*, Symbol_table*, 996 unsigned int, off_t*); 997 998 // Create the .shstrtab section. 999 Output_section* 1000 create_shstrtab(); 1001 1002 // Create the section header table. 1003 void 1004 create_shdrs(const Output_section* shstrtab_section, off_t*); 1005 1006 // Create the dynamic symbol table. 1007 void 1008 create_dynamic_symtab(const Input_objects*, Symbol_table*, 1009 Output_section** pdynstr, 1010 unsigned int* plocal_dynamic_count, 1011 std::vector<Symbol*>* pdynamic_symbols, 1012 Versions* versions); 1013 1014 // Assign offsets to each local portion of the dynamic symbol table. 1015 void 1016 assign_local_dynsym_offsets(const Input_objects*); 1017 1018 // Finish the .dynamic section and PT_DYNAMIC segment. 1019 void 1020 finish_dynamic_section(const Input_objects*, const Symbol_table*); 1021 1022 // Set the size of the _DYNAMIC symbol. 1023 void 1024 set_dynamic_symbol_size(const Symbol_table*); 1025 1026 // Create the .interp section and PT_INTERP segment. 1027 void 1028 create_interp(const Target* target); 1029 1030 // Create the version sections. 1031 void 1032 create_version_sections(const Versions*, 1033 const Symbol_table*, 1034 unsigned int local_symcount, 1035 const std::vector<Symbol*>& dynamic_symbols, 1036 const Output_section* dynstr); 1037 1038 template<int size, bool big_endian> 1039 void 1040 sized_create_version_sections(const Versions* versions, 1041 const Symbol_table*, 1042 unsigned int local_symcount, 1043 const std::vector<Symbol*>& dynamic_symbols, 1044 const Output_section* dynstr); 1045 1046 // Return whether to include this section in the link. 1047 template<int size, bool big_endian> 1048 bool 1049 include_section(Sized_relobj_file<size, big_endian>* object, const char* name, 1050 const elfcpp::Shdr<size, big_endian>&); 1051 1052 // Return the output section name to use given an input section 1053 // name. Set *PLEN to the length of the name. *PLEN must be 1054 // initialized to the length of NAME. 1055 static const char* 1056 output_section_name(const Relobj*, const char* name, size_t* plen); 1057 1058 // Return the number of allocated output sections. 1059 size_t 1060 allocated_output_section_count() const; 1061 1062 // Return the output section for NAME, TYPE and FLAGS. 1063 Output_section* 1064 get_output_section(const char* name, Stringpool::Key name_key, 1065 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags, 1066 Output_section_order order, bool is_relro); 1067 1068 // Choose the output section for NAME in RELOBJ. 1069 Output_section* 1070 choose_output_section(const Relobj* relobj, const char* name, 1071 elfcpp::Elf_Word type, elfcpp::Elf_Xword flags, 1072 bool is_input_section, Output_section_order order, 1073 bool is_relro); 1074 1075 // Create a new Output_section. 1076 Output_section* 1077 make_output_section(const char* name, elfcpp::Elf_Word type, 1078 elfcpp::Elf_Xword flags, Output_section_order order, 1079 bool is_relro); 1080 1081 // Attach a section to a segment. 1082 void 1083 attach_section_to_segment(const Target*, Output_section*); 1084 1085 // Get section order. 1086 Output_section_order 1087 default_section_order(Output_section*, bool is_relro_local); 1088 1089 // Attach an allocated section to a segment. 1090 void 1091 attach_allocated_section_to_segment(const Target*, Output_section*); 1092 1093 // Make the .eh_frame section. 1094 Output_section* 1095 make_eh_frame_section(const Relobj*); 1096 1097 // Set the final file offsets of all the segments. 1098 off_t 1099 set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx); 1100 1101 // Set the file offsets of the sections when doing a relocatable 1102 // link. 1103 off_t 1104 set_relocatable_section_offsets(Output_data*, unsigned int* pshndx); 1105 1106 // Set the final file offsets of all the sections not associated 1107 // with a segment. We set section offsets in three passes: the 1108 // first handles all allocated sections, the second sections that 1109 // require postprocessing, and the last the late-bound STRTAB 1110 // sections (probably only shstrtab, which is the one we care about 1111 // because it holds section names). 1112 enum Section_offset_pass 1113 { 1114 BEFORE_INPUT_SECTIONS_PASS, 1115 POSTPROCESSING_SECTIONS_PASS, 1116 STRTAB_AFTER_POSTPROCESSING_SECTIONS_PASS 1117 }; 1118 off_t 1119 set_section_offsets(off_t, Section_offset_pass pass); 1120 1121 // Set the final section indexes of all the sections not associated 1122 // with a segment. Returns the next unused index. 1123 unsigned int 1124 set_section_indexes(unsigned int pshndx); 1125 1126 // Set the section addresses when using a script. 1127 Output_segment* 1128 set_section_addresses_from_script(Symbol_table*); 1129 1130 // Find appropriate places or orphan sections in a script. 1131 void 1132 place_orphan_sections_in_script(); 1133 1134 // Return whether SEG1 comes before SEG2 in the output file. 1135 bool 1136 segment_precedes(const Output_segment* seg1, const Output_segment* seg2); 1137 1138 // Use to save and restore segments during relaxation. 1139 typedef Unordered_map<const Output_segment*, const Output_segment*> 1140 Segment_states; 1141 1142 // Save states of current output segments. 1143 void 1144 save_segments(Segment_states*); 1145 1146 // Restore output segment states. 1147 void 1148 restore_segments(const Segment_states*); 1149 1150 // Clean up after relaxation so that it is possible to lay out the 1151 // sections and segments again. 1152 void 1153 clean_up_after_relaxation(); 1154 1155 // Doing preparation work for relaxation. This is factored out to make 1156 // Layout::finalized a bit smaller and easier to read. 1157 void 1158 prepare_for_relaxation(); 1159 1160 // Main body of the relaxation loop, which lays out the section. 1161 off_t 1162 relaxation_loop_body(int, Target*, Symbol_table*, Output_segment**, 1163 Output_segment*, Output_segment_headers*, 1164 Output_file_header*, unsigned int*); 1165 1166 // A mapping used for kept comdats/.gnu.linkonce group signatures. 1167 typedef Unordered_map<std::string, Kept_section> Signatures; 1168 1169 // Mapping from input section name/type/flags to output section. We 1170 // use canonicalized strings here. 1171 1172 typedef std::pair<Stringpool::Key, 1173 std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key; 1174 1175 struct Hash_key 1176 { 1177 size_t 1178 operator()(const Key& k) const; 1179 }; 1180 1181 typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map; 1182 1183 // A comparison class for segments. 1184 1185 class Compare_segments 1186 { 1187 public: 1188 Compare_segments(Layout* layout) 1189 : layout_(layout) 1190 { } 1191 1192 bool 1193 operator()(const Output_segment* seg1, const Output_segment* seg2) 1194 { return this->layout_->segment_precedes(seg1, seg2); } 1195 1196 private: 1197 Layout* layout_; 1198 }; 1199 1200 typedef std::vector<Output_section_data*> Output_section_data_list; 1201 1202 // Debug checker class. 1203 class Relaxation_debug_check 1204 { 1205 public: 1206 Relaxation_debug_check() 1207 : section_infos_() 1208 { } 1209 1210 // Check that sections and special data are in reset states. 1211 void 1212 check_output_data_for_reset_values(const Layout::Section_list&, 1213 const Layout::Data_list&); 1214 1215 // Record information of a section list. 1216 void 1217 read_sections(const Layout::Section_list&); 1218 1219 // Verify a section list with recorded information. 1220 void 1221 verify_sections(const Layout::Section_list&); 1222 1223 private: 1224 // Information we care about a section. 1225 struct Section_info 1226 { 1227 // Output section described by this. 1228 Output_section* output_section; 1229 // Load address. 1230 uint64_t address; 1231 // Data size. 1232 off_t data_size; 1233 // File offset. 1234 off_t offset; 1235 }; 1236 1237 // Section information. 1238 std::vector<Section_info> section_infos_; 1239 }; 1240 1241 // The number of input files, for sizing tables. 1242 int number_of_input_files_; 1243 // Information set by scripts or by command line options. 1244 Script_options* script_options_; 1245 // The output section names. 1246 Stringpool namepool_; 1247 // The output symbol names. 1248 Stringpool sympool_; 1249 // The dynamic strings, if needed. 1250 Stringpool dynpool_; 1251 // The list of group sections and linkonce sections which we have seen. 1252 Signatures signatures_; 1253 // The mapping from input section name/type/flags to output sections. 1254 Section_name_map section_name_map_; 1255 // The list of output segments. 1256 Segment_list segment_list_; 1257 // The list of output sections. 1258 Section_list section_list_; 1259 // The list of output sections which are not attached to any output 1260 // segment. 1261 Section_list unattached_section_list_; 1262 // The list of unattached Output_data objects which require special 1263 // handling because they are not Output_sections. 1264 Data_list special_output_list_; 1265 // The section headers. 1266 Output_section_headers* section_headers_; 1267 // A pointer to the PT_TLS segment if there is one. 1268 Output_segment* tls_segment_; 1269 // A pointer to the PT_GNU_RELRO segment if there is one. 1270 Output_segment* relro_segment_; 1271 // A pointer to the PT_INTERP segment if there is one. 1272 Output_segment* interp_segment_; 1273 // A backend may increase the size of the PT_GNU_RELRO segment if 1274 // there is one. This is the amount to increase it by. 1275 unsigned int increase_relro_; 1276 // The SHT_SYMTAB output section. 1277 Output_section* symtab_section_; 1278 // The SHT_SYMTAB_SHNDX for the regular symbol table if there is one. 1279 Output_symtab_xindex* symtab_xindex_; 1280 // The SHT_DYNSYM output section if there is one. 1281 Output_section* dynsym_section_; 1282 // The SHT_SYMTAB_SHNDX for the dynamic symbol table if there is one. 1283 Output_symtab_xindex* dynsym_xindex_; 1284 // The SHT_DYNAMIC output section if there is one. 1285 Output_section* dynamic_section_; 1286 // The _DYNAMIC symbol if there is one. 1287 Symbol* dynamic_symbol_; 1288 // The dynamic data which goes into dynamic_section_. 1289 Output_data_dynamic* dynamic_data_; 1290 // The exception frame output section if there is one. 1291 Output_section* eh_frame_section_; 1292 // The exception frame data for eh_frame_section_. 1293 Eh_frame* eh_frame_data_; 1294 // Whether we have added eh_frame_data_ to the .eh_frame section. 1295 bool added_eh_frame_data_; 1296 // The exception frame header output section if there is one. 1297 Output_section* eh_frame_hdr_section_; 1298 // The data for the .gdb_index section. 1299 Gdb_index* gdb_index_data_; 1300 // The space for the build ID checksum if there is one. 1301 Output_section_data* build_id_note_; 1302 // The output section containing dwarf abbreviations 1303 Output_reduced_debug_abbrev_section* debug_abbrev_; 1304 // The output section containing the dwarf debug info tree 1305 Output_reduced_debug_info_section* debug_info_; 1306 // A list of group sections and their signatures. 1307 Group_signatures group_signatures_; 1308 // The size of the output file. 1309 off_t output_file_size_; 1310 // Whether we have added an input section to an output section. 1311 bool have_added_input_section_; 1312 // Whether we have attached the sections to the segments. 1313 bool sections_are_attached_; 1314 // Whether we have seen an object file marked to require an 1315 // executable stack. 1316 bool input_requires_executable_stack_; 1317 // Whether we have seen at least one object file with an executable 1318 // stack marker. 1319 bool input_with_gnu_stack_note_; 1320 // Whether we have seen at least one object file without an 1321 // executable stack marker. 1322 bool input_without_gnu_stack_note_; 1323 // Whether we have seen an object file that uses the static TLS model. 1324 bool has_static_tls_; 1325 // Whether any sections require postprocessing. 1326 bool any_postprocessing_sections_; 1327 // Whether we have resized the signatures_ hash table. 1328 bool resized_signatures_; 1329 // Whether we have created a .stab*str output section. 1330 bool have_stabstr_section_; 1331 // True if the input sections in the output sections should be sorted 1332 // as specified in a section ordering file. 1333 bool section_ordering_specified_; 1334 // In incremental build, holds information check the inputs and build the 1335 // .gnu_incremental_inputs section. 1336 Incremental_inputs* incremental_inputs_; 1337 // Whether we record output section data created in script 1338 bool record_output_section_data_from_script_; 1339 // List of output data that needs to be removed at relaxation clean up. 1340 Output_section_data_list script_output_section_data_list_; 1341 // Structure to save segment states before entering the relaxation loop. 1342 Segment_states* segment_states_; 1343 // A relaxation debug checker. We only create one when in debugging mode. 1344 Relaxation_debug_check* relaxation_debug_check_; 1345 // Plugins specify section_ordering using this map. This is set in 1346 // update_section_order in plugin.cc 1347 std::map<Section_id, unsigned int> section_order_map_; 1348 // Hash a pattern to its position in the section ordering file. 1349 Unordered_map<std::string, unsigned int> input_section_position_; 1350 // Vector of glob only patterns in the section_ordering file. 1351 std::vector<std::string> input_section_glob_; 1352 // For incremental links, the base file to be modified. 1353 Incremental_binary* incremental_base_; 1354 // For incremental links, a list of free space within the file. 1355 Free_list free_list_; 1356}; 1357 1358// This task handles writing out data in output sections which is not 1359// part of an input section, or which requires special handling. When 1360// this is done, it unblocks both output_sections_blocker and 1361// final_blocker. 1362 1363class Write_sections_task : public Task 1364{ 1365 public: 1366 Write_sections_task(const Layout* layout, Output_file* of, 1367 Task_token* output_sections_blocker, 1368 Task_token* final_blocker) 1369 : layout_(layout), of_(of), 1370 output_sections_blocker_(output_sections_blocker), 1371 final_blocker_(final_blocker) 1372 { } 1373 1374 // The standard Task methods. 1375 1376 Task_token* 1377 is_runnable(); 1378 1379 void 1380 locks(Task_locker*); 1381 1382 void 1383 run(Workqueue*); 1384 1385 std::string 1386 get_name() const 1387 { return "Write_sections_task"; } 1388 1389 private: 1390 class Write_sections_locker; 1391 1392 const Layout* layout_; 1393 Output_file* of_; 1394 Task_token* output_sections_blocker_; 1395 Task_token* final_blocker_; 1396}; 1397 1398// This task handles writing out data which is not part of a section 1399// or segment. 1400 1401class Write_data_task : public Task 1402{ 1403 public: 1404 Write_data_task(const Layout* layout, const Symbol_table* symtab, 1405 Output_file* of, Task_token* final_blocker) 1406 : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker) 1407 { } 1408 1409 // The standard Task methods. 1410 1411 Task_token* 1412 is_runnable(); 1413 1414 void 1415 locks(Task_locker*); 1416 1417 void 1418 run(Workqueue*); 1419 1420 std::string 1421 get_name() const 1422 { return "Write_data_task"; } 1423 1424 private: 1425 const Layout* layout_; 1426 const Symbol_table* symtab_; 1427 Output_file* of_; 1428 Task_token* final_blocker_; 1429}; 1430 1431// This task handles writing out the global symbols. 1432 1433class Write_symbols_task : public Task 1434{ 1435 public: 1436 Write_symbols_task(const Layout* layout, const Symbol_table* symtab, 1437 const Input_objects* input_objects, 1438 const Stringpool* sympool, const Stringpool* dynpool, 1439 Output_file* of, Task_token* final_blocker) 1440 : layout_(layout), symtab_(symtab), input_objects_(input_objects), 1441 sympool_(sympool), dynpool_(dynpool), of_(of), 1442 final_blocker_(final_blocker) 1443 { } 1444 1445 // The standard Task methods. 1446 1447 Task_token* 1448 is_runnable(); 1449 1450 void 1451 locks(Task_locker*); 1452 1453 void 1454 run(Workqueue*); 1455 1456 std::string 1457 get_name() const 1458 { return "Write_symbols_task"; } 1459 1460 private: 1461 const Layout* layout_; 1462 const Symbol_table* symtab_; 1463 const Input_objects* input_objects_; 1464 const Stringpool* sympool_; 1465 const Stringpool* dynpool_; 1466 Output_file* of_; 1467 Task_token* final_blocker_; 1468}; 1469 1470// This task handles writing out data in output sections which can't 1471// be written out until all the input sections have been handled. 1472// This is for sections whose contents is based on the contents of 1473// other output sections. 1474 1475class Write_after_input_sections_task : public Task 1476{ 1477 public: 1478 Write_after_input_sections_task(Layout* layout, Output_file* of, 1479 Task_token* input_sections_blocker, 1480 Task_token* final_blocker) 1481 : layout_(layout), of_(of), 1482 input_sections_blocker_(input_sections_blocker), 1483 final_blocker_(final_blocker) 1484 { } 1485 1486 // The standard Task methods. 1487 1488 Task_token* 1489 is_runnable(); 1490 1491 void 1492 locks(Task_locker*); 1493 1494 void 1495 run(Workqueue*); 1496 1497 std::string 1498 get_name() const 1499 { return "Write_after_input_sections_task"; } 1500 1501 private: 1502 Layout* layout_; 1503 Output_file* of_; 1504 Task_token* input_sections_blocker_; 1505 Task_token* final_blocker_; 1506}; 1507 1508// This task function handles closing the file. 1509 1510class Close_task_runner : public Task_function_runner 1511{ 1512 public: 1513 Close_task_runner(const General_options* options, const Layout* layout, 1514 Output_file* of) 1515 : options_(options), layout_(layout), of_(of) 1516 { } 1517 1518 // Run the operation. 1519 void 1520 run(Workqueue*, const Task*); 1521 1522 private: 1523 const General_options* options_; 1524 const Layout* layout_; 1525 Output_file* of_; 1526}; 1527 1528// A small helper function to align an address. 1529 1530inline uint64_t 1531align_address(uint64_t address, uint64_t addralign) 1532{ 1533 if (addralign != 0) 1534 address = (address + addralign - 1) &~ (addralign - 1); 1535 return address; 1536} 1537 1538} // End namespace gold. 1539 1540#endif // !defined(GOLD_LAYOUT_H) 1541