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