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_symtab;
  24 class Output_section_headers;
  25 class Output_segment;
  26 class Output_data;
  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(Object *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   // Return the Stringpool used for symbol names.
  84   const Stringpool*
  85   sympool() const
  86   { return &this->sympool_; }
  87
  88   // Return whether a section is a .gnu.linkonce section, given the
  89   // section name.
  90   static inline bool
  91   is_linkonce(const char* name)
  92   { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
  93
  94   // Record the signature of a comdat section, and return whether to
  95   // include it in the link.  The GROUP parameter is true for a
  96   // section group signature, false for a signature derived from a
  97   // .gnu.linkonce section.
  98   bool
  99   add_comdat(const char*, bool group);
 100
 101   // Finalize the layout after all the input sections have been added.
 102   off_t
 103   finalize(const Input_objects*, Symbol_table*);
 104
 105   // Return the TLS segment.
 106   Output_segment*
 107   tls_segment() const
 108   { return this->tls_segment_; }
 109
 110   // Write out data not associated with an input file or the symbol
 111   // table.
 112   void
 113   write_data(Output_file*) const;
 114
 115   // Return an output section named NAME, or NULL if there is none.
 116   Output_section*
 117   find_output_section(const char* name) const;
 118
 119   // Return an output segment of type TYPE, with segment flags SET set
 120   // and segment flags CLEAR clear.  Return NULL if there is none.
 121   Output_segment*
 122   find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,
 123                       elfcpp::Elf_Word clear) const;
 124
 125   // The list of segments.
 126
 127   typedef std::vector<Output_segment*> Segment_list;
 128
 129   // The list of sections not attached to a segment.
 130
 131   typedef std::list<Output_section*> Section_list;
 132
 133   // The list of information to write out which is not attached to
 134   // either a section or a segment.
 135   typedef std::list<Output_data*> Data_list;
 136
 137  private:
 138   Layout(const Layout&);
 139   Layout& operator=(const Layout&);
 140
 141   // Mapping from .gnu.linkonce section names to output section names.
 142   struct Linkonce_mapping
 143   {
 144     const char* from;
 145     int fromlen;
 146     const char* to;
 147     int tolen;
 148   };
 149   static const Linkonce_mapping linkonce_mapping[];
 150   static const int linkonce_mapping_count;
 151
 152   // Find the first read-only PT_LOAD segment, creating one if
 153   // necessary.
 154   Output_segment*
 155   find_first_load_seg();
 156
 157   // Set the final file offsets of all the segments.
 158   off_t
 159   set_segment_offsets(const Target*, Output_segment*, unsigned int* pshndx);
 160
 161   // Set the final file offsets and section indices of all the
 162   // sections not associated with a segment.
 163   off_t
 164   set_section_offsets(off_t, unsigned int *pshndx);
 165
 166   // Create the output sections for the symbol table.
 167   void
 168   create_symtab_sections(int size, const Input_objects*, Symbol_table*, off_t*,
 169                          Output_section** osymtab,
 170                          Output_section** ostrtab);
 171
 172   // Create the .shstrtab section.
 173   Output_section*
 174   create_shstrtab();
 175
 176   // Create the section header table.
 177   Output_section_headers*
 178   create_shdrs(int size, bool big_endian, off_t*);
 179
 180   // Return whether to include this section in the link.
 181   template<int size, bool big_endian>
 182   bool
 183   include_section(Object* object, const char* name,
 184                   const elfcpp::Shdr<size, big_endian>&);
 185
 186   // Return the output section name to use given an input section
 187   // name.  Set *PLEN to the length of the name.  *PLEN must be
 188   // initialized to the length of NAME.
 189   static const char*
 190   output_section_name(const char* name, size_t* plen);
 191
 192   // Return the output section name to use for a linkonce section
 193   // name.  PLEN is as for output_section_name.
 194   static const char*
 195   linkonce_output_name(const char* name, size_t* plen);
 196
 197   // Return the output section for NAME, TYPE and FLAGS.
 198   Output_section*
 199   get_output_section(const char* name, elfcpp::Elf_Word type,
 200                      elfcpp::Elf_Xword flags);
 201
 202   // Create a new Output_section.
 203   Output_section*
 204   make_output_section(const char* name, elfcpp::Elf_Word type,
 205                       elfcpp::Elf_Xword flags);
 206
 207   // Return whether SEG1 comes before SEG2 in the output file.
 208   static bool
 209   segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
 210
 211   // Map from section flags to segment flags.
 212   static elfcpp::Elf_Word
 213   section_flags_to_segment(elfcpp::Elf_Xword flags);
 214
 215   // A mapping used for group signatures.
 216   typedef Unordered_map<std::string, bool> Signatures;
 217
 218   // Mapping from input section name/type/flags to output section.  We
 219   // use canonicalized strings here.
 220
 221   typedef std::pair<const char*,
 222                     std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
 223
 224   struct Hash_key
 225   {
 226     size_t
 227     operator()(const Key& k) const;
 228   };
 229
 230   typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
 231
 232   // A comparison class for segments.
 233
 234   struct Compare_segments
 235   {
 236     bool
 237     operator()(const Output_segment* seg1, const Output_segment* seg2)
 238     { return Layout::segment_precedes(seg1, seg2); }
 239   };
 240
 241   // A reference to the options on the command line.
 242   const General_options& options_;
 243   // The output section names.
 244   Stringpool namepool_;
 245   // The output symbol names.
 246   Stringpool sympool_;
 247   // The list of group sections and linkonce sections which we have seen.
 248   Signatures signatures_;
 249   // The mapping from input section name/type/flags to output sections.
 250   Section_name_map section_name_map_;
 251   // The list of output segments.
 252   Segment_list segment_list_;
 253   // The list of output sections which are not attached to any output
 254   // segment.
 255   Section_list section_list_;
 256   // The list of sections which require special output because they
 257   // are not comprised of input sections.
 258   Data_list special_output_list_;
 259   // A pointer to the PT_TLS segment if there is one.
 260   Output_segment* tls_segment_;
 261 };
 262
 263 // This task handles writing out data which is not part of a section
 264 // or segment.
 265
 266 class Write_data_task : public Task
 267 {
 268  public:
 269   Write_data_task(const Layout* layout, Output_file* of,
 270                   Task_token* final_blocker)
 271     : layout_(layout), of_(of), final_blocker_(final_blocker)
 272   { }
 273
 274   // The standard Task methods.
 275
 276   Is_runnable_type
 277   is_runnable(Workqueue*);
 278
 279   Task_locker*
 280   locks(Workqueue*);
 281
 282   void
 283   run(Workqueue*);
 284
 285  private:
 286   const Layout* layout_;
 287   Output_file* of_;
 288   Task_token* final_blocker_;
 289 };
 290
 291 // This task handles writing out the global symbols.
 292
 293 class Write_symbols_task : public Task
 294 {
 295  public:
 296   Write_symbols_task(const Symbol_table* symtab, const Target* target,
 297                      const Stringpool* sympool, Output_file* of,
 298                      Task_token* final_blocker)
 299     : symtab_(symtab), target_(target), sympool_(sympool), of_(of),
 300       final_blocker_(final_blocker)
 301   { }
 302
 303   // The standard Task methods.
 304
 305   Is_runnable_type
 306   is_runnable(Workqueue*);
 307
 308   Task_locker*
 309   locks(Workqueue*);
 310
 311   void
 312   run(Workqueue*);
 313
 314  private:
 315   const Symbol_table* symtab_;
 316   const Target* target_;
 317   const Stringpool* sympool_;
 318   Output_file* of_;
 319   Task_token* final_blocker_;
 320 };
 321
 322 // This task function handles closing the file.
 323
 324 class Close_task_runner : public Task_function_runner
 325 {
 326  public:
 327   Close_task_runner(Output_file* of)
 328     : of_(of)
 329   { }
 330
 331   // Run the operation.
 332   void
 333   run(Workqueue*);
 334
 335  private:
 336   Output_file* of_;
 337 };
 338
 339 // A small helper function to align an address.
 340
 341 inline uint64_t
 342 align_address(uint64_t address, uint64_t addralign)
 343 {
 344   if (addralign != 0)
 345     address = (address + addralign - 1) &~ (addralign - 1);
 346   return address;
 347 }
 348
 349 } // End namespace gold.
 350
 351 #endif // !defined(GOLD_LAYOUT_H)