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 whether a section is a .gnu.linkonce section, given the
  93   // section name.
  94   static inline bool
  95   is_linkonce(const char* name)
  96   { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
  97
  98   // Record the signature of a comdat section, and return whether to
  99   // include it in the link.  The GROUP parameter is true for a
 100   // section group signature, false for a signature derived from a
 101   // .gnu.linkonce section.
 102   bool
 103   add_comdat(const char*, bool group);
 104
 105   // Finalize the layout after all the input sections have been added.
 106   off_t
 107   finalize(const Input_objects*, Symbol_table*);
 108
 109   // Return the TLS segment.
 110   Output_segment*
 111   tls_segment() const
 112   { return this->tls_segment_; }
 113
 114   // Write out data not associated with an input file or the symbol
 115   // table.
 116   void
 117   write_data(const Symbol_table*, const Target*, Output_file*) const;
 118
 119   // Return an output section named NAME, or NULL if there is none.
 120   Output_section*
 121   find_output_section(const char* name) const;
 122
 123   // Return an output segment of type TYPE, with segment flags SET set
 124   // and segment flags CLEAR clear.  Return NULL if there is none.
 125   Output_segment*
 126   find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
 127                       elfcpp::Elf_Word clear) const;
 128
 129   // The list of segments.
 130
 131   typedef std::vector<Output_segment*> Segment_list;
 132
 133   // The list of sections not attached to a segment.
 134
 135   typedef std::vector<Output_section*> Section_list;
 136
 137   // The list of information to write out which is not attached to
 138   // either a section or a segment.
 139   typedef std::vector<Output_data*> Data_list;
 140
 141  private:
 142   Layout(const Layout&);
 143   Layout& operator=(const Layout&);
 144
 145   // Mapping from .gnu.linkonce section names to output section names.
 146   struct Linkonce_mapping
 147   {
 148     const char* from;
 149     int fromlen;
 150     const char* to;
 151     int tolen;
 152   };
 153   static const Linkonce_mapping linkonce_mapping[];
 154   static const int linkonce_mapping_count;
 155
 156   // Find the first read-only PT_LOAD segment, creating one if
 157   // necessary.
 158   Output_segment*
 159   find_first_load_seg();
 160
 161   // Create the output sections for the symbol table.
 162   void
 163   create_symtab_sections(int size, const Input_objects*, Symbol_table*, off_t*,
 164                          Output_section** ostrtab);
 165
 166   // Create the .shstrtab section.
 167   Output_section*
 168   create_shstrtab();
 169
 170   // Create the section header table.
 171   Output_section_headers*
 172   create_shdrs(int size, bool big_endian, off_t*);
 173
 174   // Create the dynamic symbol table.
 175   void
 176   create_dynamic_symtab(const Target*, Output_data_dynamic*, Symbol_table*);
 177
 178   // Finish the .dynamic section and PT_DYNAMIC segment.
 179   void
 180   finish_dynamic_section(const Input_objects*, const Symbol_table*,
 181                          Output_data_dynamic*);
 182
 183   // Create the .interp section and PT_INTERP segment.
 184   void
 185   create_interp(const Target* target);
 186
 187   // Return whether to include this section in the link.
 188   template<int size, bool big_endian>
 189   bool
 190   include_section(Object* object, const char* name,
 191                   const elfcpp::Shdr<size, big_endian>&);
 192
 193   // Return the output section name to use given an input section
 194   // name.  Set *PLEN to the length of the name.  *PLEN must be
 195   // initialized to the length of NAME.
 196   static const char*
 197   output_section_name(const char* name, size_t* plen);
 198
 199   // Return the output section name to use for a linkonce section
 200   // name.  PLEN is as for output_section_name.
 201   static const char*
 202   linkonce_output_name(const char* name, size_t* plen);
 203
 204   // Return the output section for NAME, TYPE and FLAGS.
 205   Output_section*
 206   get_output_section(const char* name, Stringpool::Key name_key,
 207                      elfcpp::Elf_Word type, elfcpp::Elf_Xword flags);
 208
 209   // Create a new Output_section.
 210   Output_section*
 211   make_output_section(const char* name, elfcpp::Elf_Word type,
 212                       elfcpp::Elf_Xword flags);
 213
 214   // Set the final file offsets of all the segments.
 215   off_t
 216   set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
 217
 218   // Set the final file offsets and section indices of all the
 219   // sections not associated with a segment.
 220   off_t
 221   set_section_offsets(off_t, unsigned int *pshndx);
 222
 223   // Return whether SEG1 comes before SEG2 in the output file.
 224   static bool
 225   segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
 226
 227   // Map from section flags to segment flags.
 228   static elfcpp::Elf_Word
 229   section_flags_to_segment(elfcpp::Elf_Xword flags);
 230
 231   // A mapping used for group signatures.
 232   typedef Unordered_map<std::string, bool> Signatures;
 233
 234   // Mapping from input section name/type/flags to output section.  We
 235   // use canonicalized strings here.
 236
 237   typedef std::pair<Stringpool::Key,
 238                     std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
 239
 240   struct Hash_key
 241   {
 242     size_t
 243     operator()(const Key& k) const;
 244   };
 245
 246   typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
 247
 248   // A comparison class for segments.
 249
 250   struct Compare_segments
 251   {
 252     bool
 253     operator()(const Output_segment* seg1, const Output_segment* seg2)
 254     { return Layout::segment_precedes(seg1, seg2); }
 255   };
 256
 257   // A reference to the options on the command line.
 258   const General_options& options_;
 259   // The output section names.
 260   Stringpool namepool_;
 261   // The output symbol names.
 262   Stringpool sympool_;
 263   // The dynamic strings, if needed.
 264   Stringpool dynpool_;
 265   // The list of group sections and linkonce sections which we have seen.
 266   Signatures signatures_;
 267   // The mapping from input section name/type/flags to output sections.
 268   Section_name_map section_name_map_;
 269   // The list of output segments.
 270   Segment_list segment_list_;
 271   // The list of output sections.
 272   Section_list section_list_;
 273   // The list of output sections which are not attached to any output
 274   // segment.
 275   Section_list unattached_section_list_;
 276   // The list of unattached Output_data objects which require special
 277   // handling because they are not Output_sections.
 278   Data_list special_output_list_;
 279   // A pointer to the PT_TLS segment if there is one.
 280   Output_segment* tls_segment_;
 281   // The SHT_SYMTAB output section.
 282   Output_section* symtab_section_;
 283   // The SHT_DYNSYM output section if there is one.
 284   Output_section* dynsym_section_;
 285   // The SHT_DYNAMIC output section if there is one.
 286   Output_section* dynamic_section_;
 287 };
 288
 289 // This task handles writing out data which is not part of a section
 290 // or segment.
 291
 292 class Write_data_task : public Task
 293 {
 294  public:
 295   Write_data_task(const Layout* layout, const Symbol_table* symtab,
 296                   const Target* target, Output_file* of,
 297                   Task_token* final_blocker)
 298     : layout_(layout), symtab_(symtab), target_(target), of_(of),
 299       final_blocker_(final_blocker)
 300   { }
 301
 302   // The standard Task methods.
 303
 304   Is_runnable_type
 305   is_runnable(Workqueue*);
 306
 307   Task_locker*
 308   locks(Workqueue*);
 309
 310   void
 311   run(Workqueue*);
 312
 313  private:
 314   const Layout* layout_;
 315   const Symbol_table* symtab_;
 316   const Target* target_;
 317   Output_file* of_;
 318   Task_token* final_blocker_;
 319 };
 320
 321 // This task handles writing out the global symbols.
 322
 323 class Write_symbols_task : public Task
 324 {
 325  public:
 326   Write_symbols_task(const Symbol_table* symtab, const Target* target,
 327                      const Stringpool* sympool, Output_file* of,
 328                      Task_token* final_blocker)
 329     : symtab_(symtab), target_(target), sympool_(sympool), of_(of),
 330       final_blocker_(final_blocker)
 331   { }
 332
 333   // The standard Task methods.
 334
 335   Is_runnable_type
 336   is_runnable(Workqueue*);
 337
 338   Task_locker*
 339   locks(Workqueue*);
 340
 341   void
 342   run(Workqueue*);
 343
 344  private:
 345   const Symbol_table* symtab_;
 346   const Target* target_;
 347   const Stringpool* sympool_;
 348   Output_file* of_;
 349   Task_token* final_blocker_;
 350 };
 351
 352 // This task function handles closing the file.
 353
 354 class Close_task_runner : public Task_function_runner
 355 {
 356  public:
 357   Close_task_runner(Output_file* of)
 358     : of_(of)
 359   { }
 360
 361   // Run the operation.
 362   void
 363   run(Workqueue*);
 364
 365  private:
 366   Output_file* of_;
 367 };
 368
 369 // A small helper function to align an address.
 370
 371 inline uint64_t
 372 align_address(uint64_t address, uint64_t addralign)
 373 {
 374   if (addralign != 0)
 375     address = (address + addralign - 1) &~ (addralign - 1);
 376   return address;
 377 }
 378
 379 } // End namespace gold.
 380
 381 #endif // !defined(GOLD_LAYOUT_H)