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     : Object(name, input_file, true, offset), soname_()
  44   { }
  45
  46   // Return the name to use in a DT_NEEDED entry for this object.
  47   const char*
  48   soname() const;
  49
  50   // Compute the ELF hash code for a string.
  51   static uint32_t
  52   elf_hash(const char*);
  53
  54   // Create a standard ELF hash table, setting *PPHASH and *PHASHLEN.
  55   // DYNSYMS is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the
  56   // number of local dynamic symbols, which is the index of the first
  57   // dynamic gobal symbol.
  58   static void
  59   create_elf_hash_table(const std::vector<Symbol*>& dynsyms,
  60                         unsigned int local_dynsym_count,
  61                         unsigned char** pphash,
  62                         unsigned int* phashlen);
  63
  64   // Create a GNU hash table, setting *PPHASH and *PHASHLEN.  DYNSYMS
  65   // is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the number
  66   // of local dynamic symbols, which is the index of the first dynamic
  67   // gobal symbol.
  68   static void
  69   create_gnu_hash_table(const std::vector<Symbol*>& dynsyms,
  70                         unsigned int local_dynsym_count,
  71                         unsigned char** pphash, unsigned int* phashlen);
  72
  73  protected:
  74   // Set the DT_SONAME string.
  75   void
  76   set_soname_string(const char* s)
  77   { this->soname_.assign(s); }
  78
  79  private:
  80   // Compute the GNU hash code for a string.
  81   static uint32_t
  82   gnu_hash(const char*);
  83
  84   // Compute the number of hash buckets to use.
  85   static unsigned int
  86   compute_bucket_count(const std::vector<uint32_t>& hashcodes,
  87                        bool for_gnu_hash_table);
  88
  89   // Sized version of create_elf_hash_table.
  90   template<bool big_endian>
  91   static void
  92   sized_create_elf_hash_table(const std::vector<uint32_t>& bucket,
  93                               const std::vector<uint32_t>& chain,
  94                               unsigned char* phash,
  95                               unsigned int hashlen);
  96
  97   // Sized version of create_gnu_hash_table.
  98   template<int size, bool big_endian>
  99   static void
 100   sized_create_gnu_hash_table(const std::vector<Symbol*>& hashed_dynsyms,
 101                               const std::vector<uint32_t>& dynsym_hashvals,
 102                               unsigned int unhashed_dynsym_count,
 103                               unsigned char** pphash,
 104                               unsigned int* phashlen);
 105
 106   // The DT_SONAME name, if any.
 107   std::string soname_;
 108 };
 109
 110 // A dynamic object, size and endian specific version.
 111
 112 template<int size, bool big_endian>
 113 class Sized_dynobj : public Dynobj
 114 {
 115  public:
 116   Sized_dynobj(const std::string& name, Input_file* input_file, off_t offset,
 117                const typename elfcpp::Ehdr<size, big_endian>&);
 118
 119   // Set up the object file based on the ELF header.
 120   void
 121   setup(const typename elfcpp::Ehdr<size, big_endian>&);
 122
 123   // Read the symbols.
 124   void
 125   do_read_symbols(Read_symbols_data*);
 126
 127   // Lay out the input sections.
 128   void
 129   do_layout(Symbol_table*, Layout*, Read_symbols_data*);
 130
 131   // Add the symbols to the symbol table.
 132   void
 133   do_add_symbols(Symbol_table*, Read_symbols_data*);
 134
 135   // Get the name of a section.
 136   std::string
 137   do_section_name(unsigned int shndx)
 138   { return this->elf_file_.section_name(shndx); }
 139
 140   // Return a view of the contents of a section.  Set *PLEN to the
 141   // size.
 142   Object::Location
 143   do_section_contents(unsigned int shndx)
 144   { return this->elf_file_.section_contents(shndx); }
 145
 146   // Return section flags.
 147   uint64_t
 148   do_section_flags(unsigned int shndx)
 149   { return this->elf_file_.section_flags(shndx); }
 150
 151   // Return the section link field.
 152   unsigned int
 153   do_section_link(unsigned int shndx)
 154   { return this->elf_file_.section_link(shndx); }
 155
 156  private:
 157   // For convenience.
 158   typedef Sized_dynobj<size, big_endian> This;
 159   static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
 160   static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 161   static const int dyn_size = elfcpp::Elf_sizes<size>::dyn_size;
 162   typedef elfcpp::Shdr<size, big_endian> Shdr;
 163   typedef elfcpp::Dyn<size, big_endian> Dyn;
 164
 165   // Find the dynamic symbol table and the version sections, given the
 166   // section headers.
 167   void
 168   find_dynsym_sections(const unsigned char* pshdrs,
 169                        unsigned int* pdynshm_shndx,
 170                        unsigned int* pversym_shndx,
 171                        unsigned int* pverdef_shndx,
 172                        unsigned int* pverneed_shndx,
 173                        unsigned int* pdynamic_shndx);
 174
 175   // Read the dynamic symbol section SHNDX.
 176   void
 177   read_dynsym_section(const unsigned char* pshdrs, unsigned int shndx,
 178                       elfcpp::SHT type, unsigned int link,
 179                       File_view** view, off_t* view_size,
 180                       unsigned int* view_info);
 181
 182   // Set the SONAME from the SHT_DYNAMIC section at DYNAMIC_SHNDX.
 183   // The STRTAB parameters may have the relevant string table.
 184   void
 185   set_soname(const unsigned char* pshdrs, unsigned int dynamic_shndx,
 186              unsigned int strtab_shndx, const unsigned char* strtabu,
 187              off_t strtab_size);
 188
 189   // Mapping from version number to version name.
 190   typedef std::vector<const char*> Version_map;
 191
 192   // Create the version map.
 193   void
 194   make_version_map(Read_symbols_data* sd, Version_map*) const;
 195
 196   // Add version definitions to the version map.
 197   void
 198   make_verdef_map(Read_symbols_data* sd, Version_map*) const;
 199
 200   // Add version references to the version map.
 201   void
 202   make_verneed_map(Read_symbols_data* sd, Version_map*) const;
 203
 204   // Add an entry to the version map.
 205   void
 206   set_version_map(Version_map*, unsigned int ndx, const char* name) const;
 207
 208   // General access to the ELF file.
 209   elfcpp::Elf_file<size, big_endian, Object> elf_file_;
 210 };
 211
 212 // A base class for Verdef and Verneed_version which just handles the
 213 // version index which will be stored in the SHT_GNU_versym section.
 214
 215 class Version_base
 216 {
 217  public:
 218   Version_base()
 219     : index_(-1U)
 220   { }
 221
 222   virtual
 223   ~Version_base()
 224   { }
 225
 226   // Return the version index.
 227   unsigned int
 228   index() const
 229   {
 230     gold_assert(this->index_ != -1U);
 231     return this->index_;
 232   }
 233
 234   // Set the version index.
 235   void
 236   set_index(unsigned int index)
 237   {
 238     gold_assert(this->index_ == -1U);
 239     this->index_ = index;
 240   }
 241
 242   // Clear the weak flag in a version definition.
 243   virtual void
 244   clear_weak() = 0;
 245
 246  private:
 247   Version_base(const Version_base&);
 248   Version_base& operator=(const Version_base&);
 249
 250   // The index of the version definition or reference.
 251   unsigned int index_;
 252 };
 253
 254 // This class handles a version being defined in the file we are
 255 // generating.
 256
 257 class Verdef : public Version_base
 258 {
 259  public:
 260   Verdef(const char* name, bool is_base, bool is_weak, bool is_symbol_created)
 261     : name_(name), deps_(), is_base_(is_base), is_weak_(is_weak),
 262       is_symbol_created_(is_symbol_created)
 263   { }
 264
 265   // Return the version name.
 266   const char*
 267   name() const
 268   { return this->name_; }
 269
 270   // Return the number of dependencies.
 271   unsigned int
 272   count_dependencies() const
 273   { return this->deps_.size(); }
 274
 275   // Add a dependency to this version.  The NAME should be
 276   // canonicalized in the dynamic Stringpool.
 277   void
 278   add_dependency(const char* name)
 279   { this->deps_.push_back(name); }
 280
 281   // Return whether this definition is weak.
 282   bool
 283   is_weak() const
 284   { return this->is_weak_; }
 285
 286   // Clear the weak flag.
 287   void
 288   clear_weak()
 289   { this->is_weak_ = false; }
 290
 291   // Return whether a version symbol has been created for this
 292   // definition.
 293   bool
 294   is_symbol_created() const
 295   { return this->is_symbol_created_; }
 296
 297   // Write contents to buffer.
 298   template<int size, bool big_endian>
 299   unsigned char*
 300   write(const Stringpool*, bool is_last, unsigned char*
 301         ACCEPT_SIZE_ENDIAN) const;
 302
 303  private:
 304   Verdef(const Verdef&);
 305   Verdef& operator=(const Verdef&);
 306
 307   // The type of the list of version dependencies.  Each dependency
 308   // should be canonicalized in the dynamic Stringpool.
 309   typedef std::vector<const char*> Deps;
 310
 311   // The name of this version.  This should be canonicalized in the
 312   // dynamic Stringpool.
 313   const char* name_;
 314   // A list of other versions which this version depends upon.
 315   Deps deps_;
 316   // Whether this is the base version.
 317   bool is_base_;
 318   // Whether this version is weak.
 319   bool is_weak_;
 320   // Whether a version symbol has been created.
 321   bool is_symbol_created_;
 322 };
 323
 324 // A referened version.  This will be associated with a filename by
 325 // Verneed.
 326
 327 class Verneed_version : public Version_base
 328 {
 329  public:
 330   Verneed_version(const char* version)
 331     : version_(version)
 332   { }
 333
 334   // Return the version name.
 335   const char*
 336   version() const
 337   { return this->version_; }
 338
 339   // Clear the weak flag.  This is invalid for a reference.
 340   void
 341   clear_weak()
 342   { gold_unreachable(); }
 343
 344  private:
 345   Verneed_version(const Verneed_version&);
 346   Verneed_version& operator=(const Verneed_version&);
 347
 348   const char* version_;
 349 };
 350
 351 // Version references in a single dynamic object.
 352
 353 class Verneed
 354 {
 355  public:
 356   Verneed(const char* filename)
 357     : filename_(filename), need_versions_()
 358   { }
 359
 360   ~Verneed();
 361
 362   // Return the file name.
 363   const char*
 364   filename() const
 365   { return this->filename_; }
 366
 367   // Return the number of versions.
 368   unsigned int
 369   count_versions() const
 370   { return this->need_versions_.size(); }
 371
 372   // Add a version name.  The name should be canonicalized in the
 373   // dynamic Stringpool.  If the name is already present, this does
 374   // nothing.
 375   Verneed_version*
 376   add_name(const char* name);
 377
 378   // Set the version indexes, starting at INDEX.  Return the updated
 379   // INDEX.
 380   unsigned int
 381   finalize(unsigned int index);
 382
 383   // Write contents to buffer.
 384   template<int size, bool big_endian>
 385   unsigned char*
 386   write(const Stringpool*, bool is_last, unsigned char*
 387         ACCEPT_SIZE_ENDIAN) const;
 388
 389  private:
 390   Verneed(const Verneed&);
 391   Verneed& operator=(const Verneed&);
 392
 393   // The type of the list of version names.  Each name should be
 394   // canonicalized in the dynamic Stringpool.
 395   typedef std::vector<Verneed_version*> Need_versions;
 396
 397   // The filename of the dynamic object.  This should be
 398   // canonicalized in the dynamic Stringpool.
 399   const char* filename_;
 400   // The list of version names.
 401   Need_versions need_versions_;
 402 };
 403
 404 // This class handles version definitions and references which go into
 405 // the output file.
 406
 407 class Versions
 408 {
 409  public:
 410   Versions()
 411     : defs_(), needs_(), version_table_(), is_finalized_(false)
 412   { }
 413
 414   ~Versions();
 415
 416   // SYM is going into the dynamic symbol table and has a version.
 417   // Record the appropriate version information.
 418   void
 419   record_version(const Symbol_table* symtab, Stringpool*, const Symbol* sym);
 420
 421   // Set the version indexes.  DYNSYM_INDEX is the index we should use
 422   // for the next dynamic symbol.  We add new dynamic symbols to SYMS
 423   // and return an updated DYNSYM_INDEX.
 424   unsigned int
 425   finalize(const Target*, Symbol_table* symtab, unsigned int dynsym_index,
 426            std::vector<Symbol*>* syms);
 427
 428   // Return whether there are any version definitions.
 429   bool
 430   any_defs() const
 431   { return !this->defs_.empty(); }
 432
 433   // Return whether there are any version references.
 434   bool
 435   any_needs() const
 436   { return !this->needs_.empty(); }
 437
 438   // Build an allocated buffer holding the contents of the symbol
 439   // version section (.gnu.version).
 440   template<int size, bool big_endian>
 441   void
 442   symbol_section_contents(const Symbol_table*, const Stringpool*,
 443                           unsigned int local_symcount,
 444                           const std::vector<Symbol*>& syms,
 445                           unsigned char**, unsigned int*
 446                           ACCEPT_SIZE_ENDIAN) const;
 447
 448   // Build an allocated buffer holding the contents of the version
 449   // definition section (.gnu.version_d).
 450   template<int size, bool big_endian>
 451   void
 452   def_section_contents(const Stringpool*, unsigned char**,
 453                        unsigned int* psize, unsigned int* pentries
 454                        ACCEPT_SIZE_ENDIAN) const;
 455
 456   // Build an allocated buffer holding the contents of the version
 457   // reference section (.gnu.version_r).
 458   template<int size, bool big_endian>
 459   void
 460   need_section_contents(const Stringpool*, unsigned char**,
 461                         unsigned int* psize, unsigned int* pentries
 462                         ACCEPT_SIZE_ENDIAN) const;
 463
 464  private:
 465   // The type of the list of version definitions.
 466   typedef std::vector<Verdef*> Defs;
 467
 468   // The type of the list of version references.
 469   typedef std::vector<Verneed*> Needs;
 470
 471   // Handle a symbol SYM defined with version VERSION.
 472   void
 473   add_def(const Symbol* sym, const char* version, Stringpool::Key);
 474
 475   // Add a reference to version NAME in file FILENAME.
 476   void
 477   add_need(Stringpool*, const char* filename, const char* name,
 478            Stringpool::Key);
 479
 480   // Get the dynamic object to use for SYM.
 481   Dynobj*
 482   get_dynobj_for_sym(const Symbol_table*, const Symbol* sym) const;
 483
 484   // Return the version index to use for SYM.
 485   unsigned int
 486   version_index(const Symbol_table*, const Stringpool*,
 487                 const Symbol* sym) const;
 488
 489   // We keep a hash table mapping canonicalized name/version pairs to
 490   // a version base.
 491   typedef std::pair<Stringpool::Key, Stringpool::Key> Key;
 492
 493   struct Version_table_hash
 494   {
 495     size_t
 496     operator()(const Key& k) const
 497     { return k.first + k.second; }
 498   };
 499
 500   struct Version_table_eq
 501   {
 502     bool
 503     operator()(const Key& k1, const Key& k2) const
 504     { return k1.first == k2.first && k1.second == k2.second; }
 505   };
 506
 507   typedef Unordered_map<Key, Version_base*, Version_table_hash,
 508                         Version_table_eq> Version_table;
 509
 510   // The version definitions.
 511   Defs defs_;
 512   // The version references.
 513   Needs needs_;
 514   // The mapping from a canonicalized version/filename pair to a
 515   // version index.  The filename may be NULL.
 516   Version_table version_table_;
 517   // Whether the version indexes have been set.
 518   bool is_finalized_;
 519 };
 520
 521 } // End namespace gold.
 522
 523 #endif // !defined(GOLD_DYNOBJ_H)