gold/layout.h

   1 // layout.h -- lay out output file sections for gold  -*- C++ -*-
   2
   3 #ifndef GOLD_LAYOUT_H
   4 #define GOLD_LAYOUT_H
   5
   6 #include <list>
   7 #include <string>
   8 #include <utility>
   9 #include <vector>
  10
  11 #include "workqueue.h"
  12 #include "object.h"
  13 #include "dynobj.h"
  14 #include "stringpool.h"
  15
  16 namespace gold
  17 {
  18
  19 class General_options;
  20 class Input_objects;
  21 class Symbol_table;
  22 class Output_section_data;
  23 class Output_section;
  24 class Output_section_headers;
  25 class Output_segment;
  26 class Output_data;
  27 class Output_data_dynamic;
  28 class Target;
  29
  30 // This task function handles mapping the input sections to output
  31 // sections and laying them out in memory.
  32
  33 class Layout_task_runner : public Task_function_runner
  34 {
  35  public:
  36   // OPTIONS is the command line options, INPUT_OBJECTS is the list of
  37   // input objects, SYMTAB is the symbol table, LAYOUT is the layout
  38   // object.
  39   Layout_task_runner(const General_options& options,
  40                      const Input_objects* input_objects,
  41                      Symbol_table* symtab,
  42                      Layout* layout)
  43     : options_(options), input_objects_(input_objects), symtab_(symtab),
  44       layout_(layout)
  45   { }
  46
  47   // Run the operation.
  48   void
  49   run(Workqueue*);
  50
  51  private:
  52   Layout_task_runner(const Layout_task_runner&);
  53   Layout_task_runner& operator=(const Layout_task_runner&);
  54
  55   const General_options& options_;
  56   const Input_objects* input_objects_;
  57   Symbol_table* symtab_;
  58   Layout* layout_;
  59 };
  60
  61 // This class handles the details of laying out input sections.
  62
  63 class Layout
  64 {
  65  public:
  66   Layout(const General_options& options);
  67
  68   // Given an input section SHNDX, named NAME, with data in SHDR, from
  69   // the object file OBJECT, return the output section where this
  70   // input section should go.  Set *OFFSET to the offset within the
  71   // output section.
  72   template<int size, bool big_endian>
  73   Output_section*
  74   layout(Relobj *object, unsigned int shndx, const char* name,
  75          const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);
  76
  77   // Add an Output_section_data to the layout.  This is used for
  78   // special sections like the GOT section.
  79   void
  80   add_output_section_data(const char* name, elfcpp::Elf_Word type,
  81                           elfcpp::Elf_Xword flags,
  82                           Output_section_data*);
  83
  84   // Create dynamic sections if necessary.
  85   void
  86   create_initial_dynamic_sections(const Input_objects*, Symbol_table*);
  87
  88   // Return the Stringpool used for symbol names.
  89   const Stringpool*
  90   sympool() const
  91   { return &this->sympool_; }
  92
  93   // Return the Stringpool used for dynamic symbol names and dynamic
  94   // tags.
  95   const Stringpool*
  96   dynpool() const
  97   { return &this->dynpool_; }
  98
  99   // Return whether a section is a .gnu.linkonce section, given the
 100   // section name.
 101   static inline bool
 102   is_linkonce(const char* name)
 103   { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
 104
 105   // Record the signature of a comdat section, and return whether to
 106   // include it in the link.  The GROUP parameter is true for a
 107   // section group signature, false for a signature derived from a
 108   // .gnu.linkonce section.
 109   bool
 110   add_comdat(const char*, bool group);
 111
 112   // Finalize the layout after all the input sections have been added.
 113   off_t
 114   finalize(const Input_objects*, Symbol_table*);
 115
 116   // Return the TLS segment.  This will return NULL if there isn't
 117   // one.
 118   Output_segment*
 119   tls_segment() const
 120   { return this->tls_segment_; }
 121
 122   // Return the normal symbol table.
 123   Output_section*
 124   symtab_section() const
 125   {
 126     gold_assert(this->symtab_section_ != NULL);
 127     return this->symtab_section_;
 128   }
 129
 130   // Return the dynamic symbol table.
 131   Output_section*
 132   dynsym_section() const
 133   {
 134     gold_assert(this->dynsym_section_ != NULL);
 135     return this->dynsym_section_;
 136   }
 137
 138   // Return the dynamic tags.
 139   Output_data_dynamic*
 140   dynamic_data() const
 141   { return this->dynamic_data_; }
 142
 143   // Write out data not associated with an input file or the symbol
 144   // table.
 145   void
 146   write_data(const Symbol_table*, const Target*, Output_file*) const;
 147
 148   // Return an output section named NAME, or NULL if there is none.
 149   Output_section*
 150   find_output_section(const char* name) const;
 151
 152   // Return an output segment of type TYPE, with segment flags SET set
 153   // and segment flags CLEAR clear.  Return NULL if there is none.
 154   Output_segment*
 155   find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
 156                       elfcpp::Elf_Word clear) const;
 157
 158   // The list of segments.
 159
 160   typedef std::vector<Output_segment*> Segment_list;
 161
 162   // The list of sections not attached to a segment.
 163
 164   typedef std::vector<Output_section*> Section_list;
 165
 166   // The list of information to write out which is not attached to
 167   // either a section or a segment.
 168   typedef std::vector<Output_data*> Data_list;
 169
 170  private:
 171   Layout(const Layout&);
 172   Layout& operator=(const Layout&);
 173
 174   // Mapping from .gnu.linkonce section names to output section names.
 175   struct Linkonce_mapping
 176   {
 177     const char* from;
 178     int fromlen;
 179     const char* to;
 180     int tolen;
 181   };
 182   static const Linkonce_mapping linkonce_mapping[];
 183   static const int linkonce_mapping_count;
 184
 185   // Find the first read-only PT_LOAD segment, creating one if
 186   // necessary.
 187   Output_segment*
 188   find_first_load_seg();
 189
 190   // Create the output sections for the symbol table.
 191   void
 192   create_symtab_sections(int size, const Input_objects*, Symbol_table*,
 193                          off_t*);
 194
 195   // Create the .shstrtab section.
 196   Output_section*
 197   create_shstrtab();
 198
 199   // Create the section header table.
 200   Output_section_headers*
 201   create_shdrs(int size, bool big_endian, off_t*);
 202
 203   // Create the dynamic symbol table.
 204   void
 205   create_dynamic_symtab(const Target*, Symbol_table*, Output_section** pdynstr,
 206                         unsigned int* plocal_dynamic_count,
 207                         std::vector<Symbol*>* pdynamic_symbols,
 208                         Versions* versions);
 209
 210   // Finish the .dynamic section and PT_DYNAMIC segment.
 211   void
 212   finish_dynamic_section(const Input_objects*, const Symbol_table*);
 213
 214   // Create the .interp section and PT_INTERP segment.
 215   void
 216   create_interp(const Target* target);
 217
 218   // Create the version sections.
 219   void
 220   create_version_sections(const Target*, const Versions*,
 221                           unsigned int local_symcount,
 222                           const std::vector<Symbol*>& dynamic_symbols,
 223                           const Output_section* dynstr);
 224
 225   template<int size, bool big_endian>
 226   void
 227   sized_create_version_sections(const Versions* versions,
 228                                 unsigned int local_symcount,
 229                                 const std::vector<Symbol*>& dynamic_symbols,
 230                                 const Output_section* dynstr);
 231
 232   // Return whether to include this section in the link.
 233   template<int size, bool big_endian>
 234   bool
 235   include_section(Object* object, const char* name,
 236                   const elfcpp::Shdr<size, big_endian>&);
 237
 238   // Return the output section name to use given an input section
 239   // name.  Set *PLEN to the length of the name.  *PLEN must be
 240   // initialized to the length of NAME.
 241   static const char*
 242   output_section_name(const char* name, size_t* plen);
 243
 244   // Return the output section name to use for a linkonce section
 245   // name.  PLEN is as for output_section_name.
 246   static const char*
 247   linkonce_output_name(const char* name, size_t* plen);
 248
 249   // Return the output section for NAME, TYPE and FLAGS.
 250   Output_section*
 251   get_output_section(const char* name, Stringpool::Key name_key,
 252                      elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
 253
 254   // Create a new Output_section.
 255   Output_section*
 256   make_output_section(const char* name, elfcpp::Elf_Word type,
 257                       elfcpp::Elf_Xword flags);
 258
 259   // Set the final file offsets of all the segments.
 260   off_t
 261   set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
 262
 263   // Set the final file offsets and section indexes of all the
 264   // sections not associated with a segment.
 265   off_t
 266   set_section_offsets(off_t, unsigned int *pshndx);
 267
 268   // Return whether SEG1 comes before SEG2 in the output file.
 269   static bool
 270   segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
 271
 272   // Map from section flags to segment flags.
 273   static elfcpp::Elf_Word
 274   section_flags_to_segment(elfcpp::Elf_Xword flags);
 275
 276   // A mapping used for group signatures.
 277   typedef Unordered_map<std::string, bool> Signatures;
 278
 279   // Mapping from input section name/type/flags to output section.  We
 280   // use canonicalized strings here.
 281
 282   typedef std::pair<Stringpool::Key,
 283                     std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
 284
 285   struct Hash_key
 286   {
 287     size_t
 288     operator()(const Key& k) const;
 289   };
 290
 291   typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
 292
 293   // A comparison class for segments.
 294
 295   struct Compare_segments
 296   {
 297     bool
 298     operator()(const Output_segment* seg1, const Output_segment* seg2)
 299     { return Layout::segment_precedes(seg1, seg2); }
 300   };
 301
 302   // A reference to the options on the command line.
 303   const General_options& options_;
 304   // The output section names.
 305   Stringpool namepool_;
 306   // The output symbol names.
 307   Stringpool sympool_;
 308   // The dynamic strings, if needed.
 309   Stringpool dynpool_;
 310   // The list of group sections and linkonce sections which we have seen.
 311   Signatures signatures_;
 312   // The mapping from input section name/type/flags to output sections.
 313   Section_name_map section_name_map_;
 314   // The list of output segments.
 315   Segment_list segment_list_;
 316   // The list of output sections.
 317   Section_list section_list_;
 318   // The list of output sections which are not attached to any output
 319   // segment.
 320   Section_list unattached_section_list_;
 321   // The list of unattached Output_data objects which require special
 322   // handling because they are not Output_sections.
 323   Data_list special_output_list_;
 324   // A pointer to the PT_TLS segment if there is one.
 325   Output_segment* tls_segment_;
 326   // The SHT_SYMTAB output section.
 327   Output_section* symtab_section_;
 328   // The SHT_DYNSYM output section if there is one.
 329   Output_section* dynsym_section_;
 330   // The SHT_DYNAMIC output section if there is one.
 331   Output_section* dynamic_section_;
 332   // The dynamic data which goes into dynamic_section_.
 333   Output_data_dynamic* dynamic_data_;
 334 };
 335
 336 // This task handles writing out data which is not part of a section
 337 // or segment.
 338
 339 class Write_data_task : public Task
 340 {
 341  public:
 342   Write_data_task(const Layout* layout, const Symbol_table* symtab,
 343                   const Target* target, Output_file* of,
 344                   Task_token* final_blocker)
 345     : layout_(layout), symtab_(symtab), target_(target), of_(of),
 346       final_blocker_(final_blocker)
 347   { }
 348
 349   // The standard Task methods.
 350
 351   Is_runnable_type
 352   is_runnable(Workqueue*);
 353
 354   Task_locker*
 355   locks(Workqueue*);
 356
 357   void
 358   run(Workqueue*);
 359
 360  private:
 361   const Layout* layout_;
 362   const Symbol_table* symtab_;
 363   const Target* target_;
 364   Output_file* of_;
 365   Task_token* final_blocker_;
 366 };
 367
 368 // This task handles writing out the global symbols.
 369
 370 class Write_symbols_task : public Task
 371 {
 372  public:
 373   Write_symbols_task(const Symbol_table* symtab, const Target* target,
 374                      const Stringpool* sympool, const Stringpool* dynpool,
 375                      Output_file* of, Task_token* final_blocker)
 376     : symtab_(symtab), target_(target), sympool_(sympool), dynpool_(dynpool),
 377       of_(of), final_blocker_(final_blocker)
 378   { }
 379
 380   // The standard Task methods.
 381
 382   Is_runnable_type
 383   is_runnable(Workqueue*);
 384
 385   Task_locker*
 386   locks(Workqueue*);
 387
 388   void
 389   run(Workqueue*);
 390
 391  private:
 392   const Symbol_table* symtab_;
 393   const Target* target_;
 394   const Stringpool* sympool_;
 395   const Stringpool* dynpool_;
 396   Output_file* of_;
 397   Task_token* final_blocker_;
 398 };
 399
 400 // This task function handles closing the file.
 401
 402 class Close_task_runner : public Task_function_runner
 403 {
 404  public:
 405   Close_task_runner(Output_file* of)
 406     : of_(of)
 407   { }
 408
 409   // Run the operation.
 410   void
 411   run(Workqueue*);
 412
 413  private:
 414   Output_file* of_;
 415 };
 416
 417 // A small helper function to align an address.
 418
 419 inline uint64_t
 420 align_address(uint64_t address, uint64_t addralign)
 421 {
 422   if (addralign != 0)
 423     address = (address + addralign - 1) &~ (addralign - 1);
 424   return address;
 425 }
 426
 427 } // End namespace gold.
 428
 429 #endif // !defined(GOLD_LAYOUT_H)