gold/dynobj.h

   1 // dynobj.h -- dynamic object support 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_DYNOBJ_H
  24 #define GOLD_DYNOBJ_H
  25
  26 #include <vector>
  27
  28 #include "stringpool.h"
  29 #include "object.h"
  30
  31 namespace gold
  32 {
  33
  34 class General_options;
  35
  36 // A dynamic object (ET_DYN).  This is an abstract base class itself.
  37 // The implementations is the template class Sized_dynobj.
  38
  39 class Dynobj : public Object
  40 {
  41  public:
  42   Dynobj(const std::string& name, Input_file* input_file, off_t offset = 0);
  43
  44   // Return the name to use in a DT_NEEDED entry for this object.
  45   const char*
  46   soname() const;
  47
  48   // Compute the ELF hash code for a string.
  49   static uint32_t
  50   elf_hash(const char*);
  51
  52   // Create a standard ELF hash table, setting *PPHASH and *PHASHLEN.
  53   // DYNSYMS is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the
  54   // number of local dynamic symbols, which is the index of the first
  55   // dynamic gobal symbol.
  56   static void
  57   create_elf_hash_table(const std::vector<Symbol*>& dynsyms,
  58                         unsigned int local_dynsym_count,
  59                         unsigned char** pphash,
  60                         unsigned int* phashlen);
  61
  62   // Create a GNU hash table, setting *PPHASH and *PHASHLEN.  DYNSYMS
  63   // is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the number
  64   // of local dynamic symbols, which is the index of the first dynamic
  65   // gobal symbol.
  66   static void
  67   create_gnu_hash_table(const std::vector<Symbol*>& dynsyms,
  68                         unsigned int local_dynsym_count,
  69                         unsigned char** pphash, unsigned int* phashlen);
  70
  71  protected:
  72   // Set the DT_SONAME string.
  73   void
  74   set_soname_string(const char* s)
  75   { this->soname_.assign(s); }
  76
  77  private:
  78   // Compute the GNU hash code for a string.
  79   static uint32_t
  80   gnu_hash(const char*);
  81
  82   // Compute the number of hash buckets to use.
  83   static unsigned int
  84   compute_bucket_count(const std::vector<uint32_t>& hashcodes,
  85                        bool for_gnu_hash_table);
  86
  87   // Sized version of create_elf_hash_table.
  88   template<bool big_endian>
  89   static void
  90   sized_create_elf_hash_table(const std::vector<uint32_t>& bucket,
  91                               const std::vector<uint32_t>& chain,
  92                               unsigned char* phash,
  93                               unsigned int hashlen);
  94
  95   // Sized version of create_gnu_hash_table.
  96   template<int size, bool big_endian>
  97   static void
  98   sized_create_gnu_hash_table(const std::vector<Symbol*>& hashed_dynsyms,
  99                               const std::vector<uint32_t>& dynsym_hashvals,
 100                               unsigned int unhashed_dynsym_count,
 101                               unsigned char** pphash,
 102                               unsigned int* phashlen);
 103
 104   // The DT_SONAME name, if any.
 105   std::string soname_;
 106 };
 107
 108 // A dynamic object, size and endian specific version.
 109
 110 template<int size, bool big_endian>
 111 class Sized_dynobj : public Dynobj
 112 {
 113  public:
 114   Sized_dynobj(const std::string& name, Input_file* input_file, off_t offset,
 115                const typename elfcpp::Ehdr<size, big_endian>&);
 116
 117   // Set up the object file based on the ELF header.
 118   void
 119   setup(const typename elfcpp::Ehdr<size, big_endian>&);
 120
 121   // Read the symbols.
 122   void
 123   do_read_symbols(Read_symbols_data*);
 124
 125   // Lay out the input sections.
 126   void
 127   do_layout(Symbol_table*, Layout*, Read_symbols_data*);
 128
 129   // Add the symbols to the symbol table.
 130   void
 131   do_add_symbols(Symbol_table*, Read_symbols_data*);
 132
 133   // Get the name of a section.
 134   std::string
 135   do_section_name(unsigned int shndx)
 136   { return this->elf_file_.section_name(shndx); }
 137
 138   // Return a view of the contents of a section.  Set *PLEN to the
 139   // size.
 140   Object::Location
 141   do_section_contents(unsigned int shndx)
 142   { return this->elf_file_.section_contents(shndx); }
 143
 144   // Return section flags.
 145   uint64_t
 146   do_section_flags(unsigned int shndx)
 147   { return this->elf_file_.section_flags(shndx); }
 148
 149   // Return the section link field.
 150   unsigned int
 151   do_section_link(unsigned int shndx)
 152   { return this->elf_file_.section_link(shndx); }
 153
 154  private:
 155   // For convenience.
 156   typedef Sized_dynobj<size, big_endian> This;
 157   static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
 158   static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 159   static const int dyn_size = elfcpp::Elf_sizes<size>::dyn_size;
 160   typedef elfcpp::Shdr<size, big_endian> Shdr;
 161   typedef elfcpp::Dyn<size, big_endian> Dyn;
 162
 163   // Find the dynamic symbol table and the version sections, given the
 164   // section headers.
 165   void
 166   find_dynsym_sections(const unsigned char* pshdrs,
 167                        unsigned int* pdynshm_shndx,
 168                        unsigned int* pversym_shndx,
 169                        unsigned int* pverdef_shndx,
 170                        unsigned int* pverneed_shndx,
 171                        unsigned int* pdynamic_shndx);
 172
 173   // Read the dynamic symbol section SHNDX.
 174   void
 175   read_dynsym_section(const unsigned char* pshdrs, unsigned int shndx,
 176                       elfcpp::SHT type, unsigned int link,
 177                       File_view** view, off_t* view_size,
 178                       unsigned int* view_info);
 179
 180   // Set the SONAME from the SHT_DYNAMIC section at DYNAMIC_SHNDX.
 181   // The STRTAB parameters may have the relevant string table.
 182   void
 183   set_soname(const unsigned char* pshdrs, unsigned int dynamic_shndx,
 184              unsigned int strtab_shndx, const unsigned char* strtabu,
 185              off_t strtab_size);
 186
 187   // Mapping from version number to version name.
 188   typedef std::vector<const char*> Version_map;
 189
 190   // Create the version map.
 191   void
 192   make_version_map(Read_symbols_data* sd, Version_map*) const;
 193
 194   // Add version definitions to the version map.
 195   void
 196   make_verdef_map(Read_symbols_data* sd, Version_map*) const;
 197
 198   // Add version references to the version map.
 199   void
 200   make_verneed_map(Read_symbols_data* sd, Version_map*) const;
 201
 202   // Add an entry to the version map.
 203   void
 204   set_version_map(Version_map*, unsigned int ndx, const char* name) const;
 205
 206   // General access to the ELF file.
 207   elfcpp::Elf_file<size, big_endian, Object> elf_file_;
 208 };
 209
 210 // A base class for Verdef and Verneed_version which just handles the
 211 // version index which will be stored in the SHT_GNU_versym section.
 212
 213 class Version_base
 214 {
 215  public:
 216   Version_base()
 217     : index_(-1U)
 218   { }
 219
 220   virtual
 221   ~Version_base()
 222   { }
 223
 224   // Return the version index.
 225   unsigned int
 226   index() const
 227   {
 228     gold_assert(this->index_ != -1U);
 229     return this->index_;
 230   }
 231
 232   // Set the version index.
 233   void
 234   set_index(unsigned int index)
 235   {
 236     gold_assert(this->index_ == -1U);
 237     this->index_ = index;
 238   }
 239
 240   // Clear the weak flag in a version definition.
 241   virtual void
 242   clear_weak() = 0;
 243
 244  private:
 245   Version_base(const Version_base&);
 246   Version_base& operator=(const Version_base&);
 247
 248   // The index of the version definition or reference.
 249   unsigned int index_;
 250 };
 251
 252 // This class handles a version being defined in the file we are
 253 // generating.
 254
 255 class Verdef : public Version_base
 256 {
 257  public:
 258   Verdef(const char* name, bool is_base, bool is_weak, bool is_symbol_created)
 259     : name_(name), deps_(), is_base_(is_base), is_weak_(is_weak),
 260       is_symbol_created_(is_symbol_created)
 261   { }
 262
 263   // Return the version name.
 264   const char*
 265   name() const
 266   { return this->name_; }
 267
 268   // Return the number of dependencies.
 269   unsigned int
 270   count_dependencies() const
 271   { return this->deps_.size(); }
 272
 273   // Add a dependency to this version.  The NAME should be
 274   // canonicalized in the dynamic Stringpool.
 275   void
 276   add_dependency(const char* name)
 277   { this->deps_.push_back(name); }
 278
 279   // Return whether this definition is weak.
 280   bool
 281   is_weak() const
 282   { return this->is_weak_; }
 283
 284   // Clear the weak flag.
 285   void
 286   clear_weak()
 287   { this->is_weak_ = false; }
 288
 289   // Return whether a version symbol has been created for this
 290   // definition.
 291   bool
 292   is_symbol_created() const
 293   { return this->is_symbol_created_; }
 294
 295   // Write contents to buffer.
 296   template<int size, bool big_endian>
 297   unsigned char*
 298   write(const Stringpool*, bool is_last, unsigned char*
 299         ACCEPT_SIZE_ENDIAN) const;
 300
 301  private:
 302   Verdef(const Verdef&);
 303   Verdef& operator=(const Verdef&);
 304
 305   // The type of the list of version dependencies.  Each dependency
 306   // should be canonicalized in the dynamic Stringpool.
 307   typedef std::vector<const char*> Deps;
 308
 309   // The name of this version.  This should be canonicalized in the
 310   // dynamic Stringpool.
 311   const char* name_;
 312   // A list of other versions which this version depends upon.
 313   Deps deps_;
 314   // Whether this is the base version.
 315   bool is_base_;
 316   // Whether this version is weak.
 317   bool is_weak_;
 318   // Whether a version symbol has been created.
 319   bool is_symbol_created_;
 320 };
 321
 322 // A referened version.  This will be associated with a filename by
 323 // Verneed.
 324
 325 class Verneed_version : public Version_base
 326 {
 327  public:
 328   Verneed_version(const char* version)
 329     : version_(version)
 330   { }
 331
 332   // Return the version name.
 333   const char*
 334   version() const
 335   { return this->version_; }
 336
 337   // Clear the weak flag.  This is invalid for a reference.
 338   void
 339   clear_weak()
 340   { gold_unreachable(); }
 341
 342  private:
 343   Verneed_version(const Verneed_version&);
 344   Verneed_version& operator=(const Verneed_version&);
 345
 346   const char* version_;
 347 };
 348
 349 // Version references in a single dynamic object.
 350
 351 class Verneed
 352 {
 353  public:
 354   Verneed(const char* filename)
 355     : filename_(filename), need_versions_()
 356   { }
 357
 358   ~Verneed();
 359
 360   // Return the file name.
 361   const char*
 362   filename() const
 363   { return this->filename_; }
 364
 365   // Return the number of versions.
 366   unsigned int
 367   count_versions() const
 368   { return this->need_versions_.size(); }
 369
 370   // Add a version name.  The name should be canonicalized in the
 371   // dynamic Stringpool.  If the name is already present, this does
 372   // nothing.
 373   Verneed_version*
 374   add_name(const char* name);
 375
 376   // Set the version indexes, starting at INDEX.  Return the updated
 377   // INDEX.
 378   unsigned int
 379   finalize(unsigned int index);
 380
 381   // Write contents to buffer.
 382   template<int size, bool big_endian>
 383   unsigned char*
 384   write(const Stringpool*, bool is_last, unsigned char*
 385         ACCEPT_SIZE_ENDIAN) const;
 386
 387  private:
 388   Verneed(const Verneed&);
 389   Verneed& operator=(const Verneed&);
 390
 391   // The type of the list of version names.  Each name should be
 392   // canonicalized in the dynamic Stringpool.
 393   typedef std::vector<Verneed_version*> Need_versions;
 394
 395   // The filename of the dynamic object.  This should be
 396   // canonicalized in the dynamic Stringpool.
 397   const char* filename_;
 398   // The list of version names.
 399   Need_versions need_versions_;
 400 };
 401
 402 // This class handles version definitions and references which go into
 403 // the output file.
 404
 405 class Versions
 406 {
 407  public:
 408   Versions()
 409     : defs_(), needs_(), version_table_(), is_finalized_(false)
 410   { }
 411
 412   ~Versions();
 413
 414   // SYM is going into the dynamic symbol table and has a version.
 415   // Record the appropriate version information.
 416   void
 417   record_version(const Symbol_table* symtab, Stringpool*, const Symbol* sym);
 418
 419   // Set the version indexes.  DYNSYM_INDEX is the index we should use
 420   // for the next dynamic symbol.  We add new dynamic symbols to SYMS
 421   // and return an updated DYNSYM_INDEX.
 422   unsigned int
 423   finalize(const Target*, Symbol_table* symtab, unsigned int dynsym_index,
 424            std::vector<Symbol*>* syms);
 425
 426   // Return whether there are any version definitions.
 427   bool
 428   any_defs() const
 429   { return !this->defs_.empty(); }
 430
 431   // Return whether there are any version references.
 432   bool
 433   any_needs() const
 434   { return !this->needs_.empty(); }
 435
 436   // Build an allocated buffer holding the contents of the symbol
 437   // version section (.gnu.version).
 438   template<int size, bool big_endian>
 439   void
 440   symbol_section_contents(const Symbol_table*, const Stringpool*,
 441                           unsigned int local_symcount,
 442                           const std::vector<Symbol*>& syms,
 443                           unsigned char**, unsigned int*
 444                           ACCEPT_SIZE_ENDIAN) const;
 445
 446   // Build an allocated buffer holding the contents of the version
 447   // definition section (.gnu.version_d).
 448   template<int size, bool big_endian>
 449   void
 450   def_section_contents(const Stringpool*, unsigned char**,
 451                        unsigned int* psize, unsigned int* pentries
 452                        ACCEPT_SIZE_ENDIAN) const;
 453
 454   // Build an allocated buffer holding the contents of the version
 455   // reference section (.gnu.version_r).
 456   template<int size, bool big_endian>
 457   void
 458   need_section_contents(const Stringpool*, unsigned char**,
 459                         unsigned int* psize, unsigned int* pentries
 460                         ACCEPT_SIZE_ENDIAN) const;
 461
 462  private:
 463   // The type of the list of version definitions.
 464   typedef std::vector<Verdef*> Defs;
 465
 466   // The type of the list of version references.
 467   typedef std::vector<Verneed*> Needs;
 468
 469   // Handle a symbol SYM defined with version VERSION.
 470   void
 471   add_def(const Symbol* sym, const char* version, Stringpool::Key);
 472
 473   // Add a reference to version NAME in file FILENAME.
 474   void
 475   add_need(Stringpool*, const char* filename, const char* name,
 476            Stringpool::Key);
 477
 478   // Get the dynamic object to use for SYM.
 479   Dynobj*
 480   get_dynobj_for_sym(const Symbol_table*, const Symbol* sym) const;
 481
 482   // Return the version index to use for SYM.
 483   unsigned int
 484   version_index(const Symbol_table*, const Stringpool*,
 485                 const Symbol* sym) const;
 486
 487   // We keep a hash table mapping canonicalized name/version pairs to
 488   // a version base.
 489   typedef std::pair<Stringpool::Key, Stringpool::Key> Key;
 490
 491   struct Version_table_hash
 492   {
 493     size_t
 494     operator()(const Key& k) const
 495     { return k.first + k.second; }
 496   };
 497
 498   struct Version_table_eq
 499   {
 500     bool
 501     operator()(const Key& k1, const Key& k2) const
 502     { return k1.first == k2.first && k1.second == k2.second; }
 503   };
 504
 505   typedef Unordered_map<Key, Version_base*, Version_table_hash,
 506                         Version_table_eq> Version_table;
 507
 508   // The version definitions.
 509   Defs defs_;
 510   // The version references.
 511   Needs needs_;
 512   // The mapping from a canonicalized version/filename pair to a
 513   // version index.  The filename may be NULL.
 514   Version_table version_table_;
 515   // Whether the version indexes have been set.
 516   bool is_finalized_;
 517 };
 518
 519 } // End namespace gold.
 520
 521 #endif // !defined(GOLD_DYNOBJ_H)