gold/layout.h

   1 // layout.h -- lay out output file sections for gold  -*- C++ -*-
   2
   3 // Copyright 2006, 2007 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 #ifndef GOLD_LAYOUT_H
  24 #define GOLD_LAYOUT_H
  25
  26 #include <list>
  27 #include <string>
  28 #include <utility>
  29 #include <vector>
  30
  31 #include "workqueue.h"
  32 #include "object.h"
  33 #include "dynobj.h"
  34 #include "stringpool.h"
  35
  36 namespace gold
  37 {
  38
  39 class General_options;
  40 class Input_objects;
  41 class Symbol_table;
  42 class Output_section_data;
  43 class Output_section;
  44 class Output_section_headers;
  45 class Output_segment;
  46 class Output_data;
  47 class Output_data_dynamic;
  48 class Target;
  49
  50 // This task function handles mapping the input sections to output
  51 // sections and laying them out in memory.
  52
  53 class Layout_task_runner : public Task_function_runner
  54 {
  55  public:
  56   // OPTIONS is the command line options, INPUT_OBJECTS is the list of
  57   // input objects, SYMTAB is the symbol table, LAYOUT is the layout
  58   // object.
  59   Layout_task_runner(const General_options& options,
  60                      const Input_objects* input_objects,
  61                      Symbol_table* symtab,
  62                      Layout* layout)
  63     : options_(options), input_objects_(input_objects), symtab_(symtab),
  64       layout_(layout)
  65   { }
  66
  67   // Run the operation.
  68   void
  69   run(Workqueue*);
  70
  71  private:
  72   Layout_task_runner(const Layout_task_runner&);
  73   Layout_task_runner& operator=(const Layout_task_runner&);
  74
  75   const General_options& options_;
  76   const Input_objects* input_objects_;
  77   Symbol_table* symtab_;
  78   Layout* layout_;
  79 };
  80
  81 // This class handles the details of laying out input sections.
  82
  83 class Layout
  84 {
  85  public:
  86   Layout(const General_options& options);
  87
  88   // Given an input section SHNDX, named NAME, with data in SHDR, from
  89   // the object file OBJECT, return the output section where this
  90   // input section should go.  Set *OFFSET to the offset within the
  91   // output section.
  92   template<int size, bool big_endian>
  93   Output_section*
  94   layout(Relobj *object, unsigned int shndx, const char* name,
  95          const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);
  96
  97   // Add an Output_section_data to the layout.  This is used for
  98   // special sections like the GOT section.
  99   void
 100   add_output_section_data(const char* name, elfcpp::Elf_Word type,
 101                           elfcpp::Elf_Xword flags,
 102                           Output_section_data*);
 103
 104   // Create dynamic sections if necessary.
 105   void
 106   create_initial_dynamic_sections(const Input_objects*, Symbol_table*);
 107
 108   // Define __start and __stop symbols for output sections.
 109   void
 110   define_section_symbols(Symbol_table*, const Target*);
 111
 112   // Return the Stringpool used for symbol names.
 113   const Stringpool*
 114   sympool() const
 115   { return &this->sympool_; }
 116
 117   // Return the Stringpool used for dynamic symbol names and dynamic
 118   // tags.
 119   const Stringpool*
 120   dynpool() const
 121   { return &this->dynpool_; }
 122
 123   // Return whether a section is a .gnu.linkonce section, given the
 124   // section name.
 125   static inline bool
 126   is_linkonce(const char* name)
 127   { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
 128
 129   // Record the signature of a comdat section, and return whether to
 130   // include it in the link.  The GROUP parameter is true for a
 131   // section group signature, false for a signature derived from a
 132   // .gnu.linkonce section.
 133   bool
 134   add_comdat(const char*, bool group);
 135
 136   // Finalize the layout after all the input sections have been added.
 137   off_t
 138   finalize(const Input_objects*, Symbol_table*);
 139
 140   // Return the size of the output file.
 141   off_t
 142   output_file_size() const
 143   { return this->output_file_size_; }
 144
 145   // Return the TLS segment.  This will return NULL if there isn't
 146   // one.
 147   Output_segment*
 148   tls_segment() const
 149   { return this->tls_segment_; }
 150
 151   // Return the normal symbol table.
 152   Output_section*
 153   symtab_section() const
 154   {
 155     gold_assert(this->symtab_section_ != NULL);
 156     return this->symtab_section_;
 157   }
 158
 159   // Return the dynamic symbol table.
 160   Output_section*
 161   dynsym_section() const
 162   {
 163     gold_assert(this->dynsym_section_ != NULL);
 164     return this->dynsym_section_;
 165   }
 166
 167   // Return the dynamic tags.
 168   Output_data_dynamic*
 169   dynamic_data() const
 170   { return this->dynamic_data_; }
 171
 172   // Write out data not associated with an input file or the symbol
 173   // table.
 174   void
 175   write_data(const Symbol_table*, Output_file*) const;
 176
 177   // Return an output section named NAME, or NULL if there is none.
 178   Output_section*
 179   find_output_section(const char* name) const;
 180
 181   // Return an output segment of type TYPE, with segment flags SET set
 182   // and segment flags CLEAR clear.  Return NULL if there is none.
 183   Output_segment*
 184   find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
 185                       elfcpp::Elf_Word clear) const;
 186
 187   // The list of segments.
 188
 189   typedef std::vector<Output_segment*> Segment_list;
 190
 191   // The list of sections not attached to a segment.
 192
 193   typedef std::vector<Output_section*> Section_list;
 194
 195   // The list of information to write out which is not attached to
 196   // either a section or a segment.
 197   typedef std::vector<Output_data*> Data_list;
 198
 199  private:
 200   Layout(const Layout&);
 201   Layout& operator=(const Layout&);
 202
 203   // Mapping from .gnu.linkonce section names to output section names.
 204   struct Linkonce_mapping
 205   {
 206     const char* from;
 207     int fromlen;
 208     const char* to;
 209     int tolen;
 210   };
 211   static const Linkonce_mapping linkonce_mapping[];
 212   static const int linkonce_mapping_count;
 213
 214   // Handle an exception frame section.
 215   template<int size, bool big_endian>
 216   void
 217   layout_eh_frame(Relobj*, unsigned int, const char*,
 218                   const elfcpp::Shdr<size, big_endian>&,
 219                   Output_section*, off_t*);
 220
 221   // Create a .note section for gold.
 222   void
 223   create_note_section();
 224
 225   // Find the first read-only PT_LOAD segment, creating one if
 226   // necessary.
 227   Output_segment*
 228   find_first_load_seg();
 229
 230   // Create the output sections for the symbol table.
 231   void
 232   create_symtab_sections(const Input_objects*, Symbol_table*, off_t*);
 233
 234   // Create the .shstrtab section.
 235   Output_section*
 236   create_shstrtab();
 237
 238   // Create the section header table.
 239   Output_section_headers*
 240   create_shdrs(off_t*);
 241
 242   // Create the dynamic symbol table.
 243   void
 244   create_dynamic_symtab(const Target*, Symbol_table*, Output_section** pdynstr,
 245                         unsigned int* plocal_dynamic_count,
 246                         std::vector<Symbol*>* pdynamic_symbols,
 247                         Versions* versions);
 248
 249   // Finish the .dynamic section and PT_DYNAMIC segment.
 250   void
 251   finish_dynamic_section(const Input_objects*, const Symbol_table*);
 252
 253   // Create the .interp section and PT_INTERP segment.
 254   void
 255   create_interp(const Target* target);
 256
 257   // Create the version sections.
 258   void
 259   create_version_sections(const Versions*,
 260                           unsigned int local_symcount,
 261                           const std::vector<Symbol*>& dynamic_symbols,
 262                           const Output_section* dynstr);
 263
 264   template<int size, bool big_endian>
 265   void
 266   sized_create_version_sections(const Versions* versions,
 267                                 unsigned int local_symcount,
 268                                 const std::vector<Symbol*>& dynamic_symbols,
 269                                 const Output_section* dynstr
 270                                 ACCEPT_SIZE_ENDIAN);
 271
 272   // Return whether to include this section in the link.
 273   template<int size, bool big_endian>
 274   bool
 275   include_section(Object* object, const char* name,
 276                   const elfcpp::Shdr<size, big_endian>&);
 277
 278   // Return the output section name to use given an input section
 279   // name.  Set *PLEN to the length of the name.  *PLEN must be
 280   // initialized to the length of NAME.
 281   static const char*
 282   output_section_name(const char* name, size_t* plen);
 283
 284   // Return the output section name to use for a linkonce section
 285   // name.  PLEN is as for output_section_name.
 286   static const char*
 287   linkonce_output_name(const char* name, size_t* plen);
 288
 289   // Return the output section for NAME, TYPE and FLAGS.
 290   Output_section*
 291   get_output_section(const char* name, Stringpool::Key name_key,
 292                      elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
 293
 294   // Create a new Output_section.
 295   Output_section*
 296   make_output_section(const char* name, elfcpp::Elf_Word type,
 297                       elfcpp::Elf_Xword flags);
 298
 299   // Set the final file offsets of all the segments.
 300   off_t
 301   set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
 302
 303   // Set the final file offsets and section indexes of all the
 304   // sections not associated with a segment.
 305   off_t
 306   set_section_offsets(off_t, unsigned int *pshndx);
 307
 308   // Return whether SEG1 comes before SEG2 in the output file.
 309   static bool
 310   segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
 311
 312   // Map from section flags to segment flags.
 313   static elfcpp::Elf_Word
 314   section_flags_to_segment(elfcpp::Elf_Xword flags);
 315
 316   // A mapping used for group signatures.
 317   typedef Unordered_map<std::string, bool> Signatures;
 318
 319   // Mapping from input section name/type/flags to output section.  We
 320   // use canonicalized strings here.
 321
 322   typedef std::pair<Stringpool::Key,
 323                     std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
 324
 325   struct Hash_key
 326   {
 327     size_t
 328     operator()(const Key& k) const;
 329   };
 330
 331   typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
 332
 333   // A comparison class for segments.
 334
 335   struct Compare_segments
 336   {
 337     bool
 338     operator()(const Output_segment* seg1, const Output_segment* seg2)
 339     { return Layout::segment_precedes(seg1, seg2); }
 340   };
 341
 342   // A reference to the options on the command line.
 343   const General_options& options_;
 344   // The output section names.
 345   Stringpool namepool_;
 346   // The output symbol names.
 347   Stringpool sympool_;
 348   // The dynamic strings, if needed.
 349   Stringpool dynpool_;
 350   // The list of group sections and linkonce sections which we have seen.
 351   Signatures signatures_;
 352   // The mapping from input section name/type/flags to output sections.
 353   Section_name_map section_name_map_;
 354   // The list of output segments.
 355   Segment_list segment_list_;
 356   // The list of output sections.
 357   Section_list section_list_;
 358   // The list of output sections which are not attached to any output
 359   // segment.
 360   Section_list unattached_section_list_;
 361   // The list of unattached Output_data objects which require special
 362   // handling because they are not Output_sections.
 363   Data_list special_output_list_;
 364   // A pointer to the PT_TLS segment if there is one.
 365   Output_segment* tls_segment_;
 366   // The SHT_SYMTAB output section.
 367   Output_section* symtab_section_;
 368   // The SHT_DYNSYM output section if there is one.
 369   Output_section* dynsym_section_;
 370   // The SHT_DYNAMIC output section if there is one.
 371   Output_section* dynamic_section_;
 372   // The dynamic data which goes into dynamic_section_.
 373   Output_data_dynamic* dynamic_data_;
 374   // The exception frame section.
 375   Output_section* eh_frame_section_;
 376   // The size of the output file.
 377   off_t output_file_size_;
 378 };
 379
 380 // This task handles writing out data which is not part of a section
 381 // or segment.
 382
 383 class Write_data_task : public Task
 384 {
 385  public:
 386   Write_data_task(const Layout* layout, const Symbol_table* symtab,
 387                   Output_file* of, Task_token* final_blocker)
 388     : layout_(layout), symtab_(symtab), of_(of), final_blocker_(final_blocker)
 389   { }
 390
 391   // The standard Task methods.
 392
 393   Is_runnable_type
 394   is_runnable(Workqueue*);
 395
 396   Task_locker*
 397   locks(Workqueue*);
 398
 399   void
 400   run(Workqueue*);
 401
 402  private:
 403   const Layout* layout_;
 404   const Symbol_table* symtab_;
 405   Output_file* of_;
 406   Task_token* final_blocker_;
 407 };
 408
 409 // This task handles writing out the global symbols.
 410
 411 class Write_symbols_task : public Task
 412 {
 413  public:
 414   Write_symbols_task(const Symbol_table* symtab, const Target* target,
 415                      const Stringpool* sympool, const Stringpool* dynpool,
 416                      Output_file* of, Task_token* final_blocker)
 417     : symtab_(symtab), target_(target), sympool_(sympool), dynpool_(dynpool),
 418       of_(of), final_blocker_(final_blocker)
 419   { }
 420
 421   // The standard Task methods.
 422
 423   Is_runnable_type
 424   is_runnable(Workqueue*);
 425
 426   Task_locker*
 427   locks(Workqueue*);
 428
 429   void
 430   run(Workqueue*);
 431
 432  private:
 433   const Symbol_table* symtab_;
 434   const Target* target_;
 435   const Stringpool* sympool_;
 436   const Stringpool* dynpool_;
 437   Output_file* of_;
 438   Task_token* final_blocker_;
 439 };
 440
 441 // This task function handles closing the file.
 442
 443 class Close_task_runner : public Task_function_runner
 444 {
 445  public:
 446   Close_task_runner(Output_file* of)
 447     : of_(of)
 448   { }
 449
 450   // Run the operation.
 451   void
 452   run(Workqueue*);
 453
 454  private:
 455   Output_file* of_;
 456 };
 457
 458 // A small helper function to align an address.
 459
 460 inline uint64_t
 461 align_address(uint64_t address, uint64_t addralign)
 462 {
 463   if (addralign != 0)
 464     address = (address + addralign - 1) &~ (addralign - 1);
 465   return address;
 466 }
 467
 468 } // End namespace gold.
 469
 470 #endif // !defined(GOLD_LAYOUT_H)