gold/dynobj.h

   1 // dynobj.h -- dynamic object support for gold   -*- C++ -*-
   2
   3 // Copyright (C) 2006-2015 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 Version_script_info;
  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   // We keep a list of all the DT_NEEDED entries we find.
  43   typedef std::vector<std::string> Needed;
  44
  45   Dynobj(const std::string& name, Input_file* input_file, off_t offset = 0);
  46
  47   // Return the name to use in a DT_NEEDED entry for this object.
  48   const char*
  49   soname() const
  50   { return this->soname_.c_str(); }
  51
  52   // Return the list of DT_NEEDED strings.
  53   const Needed&
  54   needed() const
  55   { return this->needed_; }
  56
  57   // Return whether this dynamic object has any DT_NEEDED entries
  58   // which were not seen during the link.
  59   bool
  60   has_unknown_needed_entries() const
  61   {
  62     gold_assert(this->unknown_needed_ != UNKNOWN_NEEDED_UNSET);
  63     return this->unknown_needed_ == UNKNOWN_NEEDED_TRUE;
  64   }
  65
  66   // Set whether this dynamic object has any DT_NEEDED entries which
  67   // were not seen during the link.
  68   void
  69   set_has_unknown_needed_entries(bool set)
  70   {
  71     gold_assert(this->unknown_needed_ == UNKNOWN_NEEDED_UNSET);
  72     this->unknown_needed_ = set ? UNKNOWN_NEEDED_TRUE : UNKNOWN_NEEDED_FALSE;
  73   }
  74
  75   // Compute the ELF hash code for a string.
  76   static uint32_t
  77   elf_hash(const char*);
  78
  79   // Create a standard ELF hash table, setting *PPHASH and *PHASHLEN.
  80   // DYNSYMS is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the
  81   // number of local dynamic symbols, which is the index of the first
  82   // dynamic gobal symbol.
  83   static void
  84   create_elf_hash_table(const std::vector<Symbol*>& dynsyms,
  85                         unsigned int local_dynsym_count,
  86                         unsigned char** pphash,
  87                         unsigned int* phashlen);
  88
  89   // Create a GNU hash table, setting *PPHASH and *PHASHLEN.  DYNSYMS
  90   // is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the number
  91   // of local dynamic symbols, which is the index of the first dynamic
  92   // gobal symbol.
  93   static void
  94   create_gnu_hash_table(const std::vector<Symbol*>& dynsyms,
  95                         unsigned int local_dynsym_count,
  96                         unsigned char** pphash, unsigned int* phashlen);
  97
  98  protected:
  99   // Return a pointer to this object.
 100   virtual Dynobj*
 101   do_dynobj()
 102   { return this; }
 103
 104   // Set the DT_SONAME string.
 105   void
 106   set_soname_string(const char* s)
 107   { this->soname_.assign(s); }
 108
 109   // Add an entry to the list of DT_NEEDED strings.
 110   void
 111   add_needed(const char* s)
 112   { this->needed_.push_back(std::string(s)); }
 113
 114  private:
 115   // Compute the GNU hash code for a string.
 116   static uint32_t
 117   gnu_hash(const char*);
 118
 119   // Compute the number of hash buckets to use.
 120   static unsigned int
 121   compute_bucket_count(const std::vector<uint32_t>& hashcodes,
 122                        bool for_gnu_hash_table);
 123
 124   // Sized version of create_elf_hash_table.
 125   template<bool big_endian>
 126   static void
 127   sized_create_elf_hash_table(const std::vector<uint32_t>& bucket,
 128                               const std::vector<uint32_t>& chain,
 129                               unsigned char* phash,
 130                               unsigned int hashlen);
 131
 132   // Sized version of create_gnu_hash_table.
 133   template<int size, bool big_endian>
 134   static void
 135   sized_create_gnu_hash_table(const std::vector<Symbol*>& hashed_dynsyms,
 136                               const std::vector<uint32_t>& dynsym_hashvals,
 137                               unsigned int unhashed_dynsym_count,
 138                               unsigned char** pphash,
 139                               unsigned int* phashlen);
 140
 141   // Values for the has_unknown_needed_entries_ field.
 142   enum Unknown_needed
 143   {
 144     UNKNOWN_NEEDED_UNSET,
 145     UNKNOWN_NEEDED_TRUE,
 146     UNKNOWN_NEEDED_FALSE
 147   };
 148
 149   // The DT_SONAME name, if any.
 150   std::string soname_;
 151   // The list of DT_NEEDED entries.
 152   Needed needed_;
 153   // Whether this dynamic object has any DT_NEEDED entries not seen
 154   // during the link.
 155   Unknown_needed unknown_needed_;
 156 };
 157
 158 // A dynamic object, size and endian specific version.
 159
 160 template<int size, bool big_endian>
 161 class Sized_dynobj : public Dynobj
 162 {
 163  public:
 164   typedef typename Sized_relobj_file<size, big_endian>::Symbols Symbols;
 165
 166   Sized_dynobj(const std::string& name, Input_file* input_file, off_t offset,
 167                const typename elfcpp::Ehdr<size, big_endian>&);
 168
 169   // Set up the object file based on TARGET.
 170   void
 171   setup();
 172
 173   // Read the symbols.
 174   void
 175   do_read_symbols(Read_symbols_data*);
 176
 177   // Lay out the input sections.
 178   void
 179   do_layout(Symbol_table*, Layout*, Read_symbols_data*);
 180
 181   // Add the symbols to the symbol table.
 182   void
 183   do_add_symbols(Symbol_table*, Read_symbols_data*, Layout*);
 184
 185   Archive::Should_include
 186   do_should_include_member(Symbol_table* symtab, Layout*, Read_symbols_data*,
 187                            std::string* why);
 188
 189   // Iterate over global symbols, calling a visitor class V for each.
 190   void
 191   do_for_all_global_symbols(Read_symbols_data* sd,
 192                             Library_base::Symbol_visitor_base* v);
 193
 194   // Iterate over local symbols, calling a visitor class V for each GOT offset
 195   // associated with a local symbol.
 196   void
 197   do_for_all_local_got_entries(Got_offset_list::Visitor* v) const;
 198
 199   // Get the size of a section.
 200   uint64_t
 201   do_section_size(unsigned int shndx)
 202   { return this->elf_file_.section_size(shndx); }
 203
 204   // Get the name of a section.
 205   std::string
 206   do_section_name(unsigned int shndx) const
 207   { return this->elf_file_.section_name(shndx); }
 208
 209   // Return a view of the contents of a section.  Set *PLEN to the
 210   // size.
 211   const unsigned char*
 212   do_section_contents(unsigned int shndx, section_size_type* plen,
 213                       bool cache)
 214   {
 215     Location loc(this->elf_file_.section_contents(shndx));
 216     *plen = convert_to_section_size_type(loc.data_size);
 217     if (*plen == 0)
 218       {
 219         static const unsigned char empty[1] = { '\0' };
 220         return empty;
 221       }
 222     return this->get_view(loc.file_offset, *plen, true, cache);
 223   }
 224
 225   // Return section flags.
 226   uint64_t
 227   do_section_flags(unsigned int shndx)
 228   { return this->elf_file_.section_flags(shndx); }
 229
 230   // Not used for dynobj.
 231   uint64_t
 232   do_section_entsize(unsigned int )
 233   { gold_unreachable(); }
 234
 235   // Return section address.
 236   uint64_t
 237   do_section_address(unsigned int shndx)
 238   { return this->elf_file_.section_addr(shndx); }
 239
 240   // Return section type.
 241   unsigned int
 242   do_section_type(unsigned int shndx)
 243   { return this->elf_file_.section_type(shndx); }
 244
 245   // Return the section link field.
 246   unsigned int
 247   do_section_link(unsigned int shndx)
 248   { return this->elf_file_.section_link(shndx); }
 249
 250   // Return the section link field.
 251   unsigned int
 252   do_section_info(unsigned int shndx)
 253   { return this->elf_file_.section_info(shndx); }
 254
 255   // Return the section alignment.
 256   uint64_t
 257   do_section_addralign(unsigned int shndx)
 258   { return this->elf_file_.section_addralign(shndx); }
 259
 260   // Return the Xindex structure to use.
 261   Xindex*
 262   do_initialize_xindex();
 263
 264   // Get symbol counts.
 265   void
 266   do_get_global_symbol_counts(const Symbol_table*, size_t*, size_t*) const;
 267
 268   // Get the global symbols.
 269   const Symbols*
 270   do_get_global_symbols() const
 271   { return this->symbols_; }
 272
 273  protected:
 274   // Read the symbols.  This is common code for all target-specific
 275   // overrides of do_read_symbols().
 276   void
 277   base_read_symbols(Read_symbols_data*);
 278
 279  private:
 280   // For convenience.
 281   typedef Sized_dynobj<size, big_endian> This;
 282   static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
 283   static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 284   static const int dyn_size = elfcpp::Elf_sizes<size>::dyn_size;
 285   typedef elfcpp::Shdr<size, big_endian> Shdr;
 286   typedef elfcpp::Dyn<size, big_endian> Dyn;
 287
 288   // Adjust a section index if necessary.
 289   unsigned int
 290   adjust_shndx(unsigned int shndx)
 291   {
 292     if (shndx >= elfcpp::SHN_LORESERVE)
 293       shndx += this->elf_file_.large_shndx_offset();
 294     return shndx;
 295   }
 296
 297   // Find the dynamic symbol table and the version sections, given the
 298   // section headers.
 299   void
 300   find_dynsym_sections(const unsigned char* pshdrs,
 301                        unsigned int* pversym_shndx,
 302                        unsigned int* pverdef_shndx,
 303                        unsigned int* pverneed_shndx,
 304                        unsigned int* pdynamic_shndx);
 305
 306   // Read the dynamic symbol section SHNDX.
 307   void
 308   read_dynsym_section(const unsigned char* pshdrs, unsigned int shndx,
 309                       elfcpp::SHT type, unsigned int link,
 310                       File_view** view, section_size_type* view_size,
 311                       unsigned int* view_info);
 312
 313   // Read the dynamic tags.
 314   void
 315   read_dynamic(const unsigned char* pshdrs, unsigned int dynamic_shndx,
 316                unsigned int strtab_shndx, const unsigned char* strtabu,
 317                off_t strtab_size);
 318
 319   // Mapping from version number to version name.
 320   typedef std::vector<const char*> Version_map;
 321
 322   // Create the version map.
 323   void
 324   make_version_map(Read_symbols_data* sd, Version_map*) const;
 325
 326   // Add version definitions to the version map.
 327   void
 328   make_verdef_map(Read_symbols_data* sd, Version_map*) const;
 329
 330   // Add version references to the version map.
 331   void
 332   make_verneed_map(Read_symbols_data* sd, Version_map*) const;
 333
 334   // Add an entry to the version map.
 335   void
 336   set_version_map(Version_map*, unsigned int ndx, const char* name) const;
 337
 338   // General access to the ELF file.
 339   elfcpp::Elf_file<size, big_endian, Object> elf_file_;
 340   // The section index of the dynamic symbol table.
 341   unsigned int dynsym_shndx_;
 342   // The entries in the symbol table for the symbols.  We only keep
 343   // this if we need it to print symbol information.
 344   Symbols* symbols_;
 345   // Number of defined symbols.
 346   size_t defined_count_;
 347 };
 348
 349 // A base class for Verdef and Verneed_version which just handles the
 350 // version index which will be stored in the SHT_GNU_versym section.
 351
 352 class Version_base
 353 {
 354  public:
 355   Version_base()
 356     : index_(-1U)
 357   { }
 358
 359   virtual
 360   ~Version_base()
 361   { }
 362
 363   // Return the version index.
 364   unsigned int
 365   index() const
 366   {
 367     gold_assert(this->index_ != -1U);
 368     return this->index_;
 369   }
 370
 371   // Set the version index.
 372   void
 373   set_index(unsigned int index)
 374   {
 375     gold_assert(this->index_ == -1U);
 376     this->index_ = index;
 377   }
 378
 379   // Clear the weak flag in a version definition.
 380   virtual void
 381   clear_weak() = 0;
 382
 383  private:
 384   Version_base(const Version_base&);
 385   Version_base& operator=(const Version_base&);
 386
 387   // The index of the version definition or reference.
 388   unsigned int index_;
 389 };
 390
 391 // This class handles a version being defined in the file we are
 392 // generating.
 393
 394 class Verdef : public Version_base
 395 {
 396  public:
 397   Verdef(const char* name, const std::vector<std::string>& deps,
 398          bool is_base, bool is_weak, bool is_info, bool is_symbol_created)
 399     : name_(name), deps_(deps), is_base_(is_base), is_weak_(is_weak),
 400       is_info_(is_info), is_symbol_created_(is_symbol_created)
 401   { }
 402
 403   // Return the version name.
 404   const char*
 405   name() const
 406   { return this->name_; }
 407
 408   // Return the number of dependencies.
 409   unsigned int
 410   count_dependencies() const
 411   { return this->deps_.size(); }
 412
 413   // Add a dependency to this version.  The NAME should be
 414   // canonicalized in the dynamic Stringpool.
 415   void
 416   add_dependency(const char* name)
 417   { this->deps_.push_back(name); }
 418
 419   // Return whether this definition is weak.
 420   bool
 421   is_weak() const
 422   { return this->is_weak_; }
 423
 424   // Clear the weak flag.
 425   void
 426   clear_weak()
 427   { this->is_weak_ = false; }
 428
 429   // Return whether this definition is informational.
 430   bool
 431   is_info() const
 432   { return this->is_info_; }
 433
 434   // Return whether a version symbol has been created for this
 435   // definition.
 436   bool
 437   is_symbol_created() const
 438   { return this->is_symbol_created_; }
 439
 440   // Write contents to buffer.
 441   template<int size, bool big_endian>
 442   unsigned char*
 443   write(const Stringpool*, bool is_last, unsigned char*) const;
 444
 445  private:
 446   Verdef(const Verdef&);
 447   Verdef& operator=(const Verdef&);
 448
 449   // The type of the list of version dependencies.  Each dependency
 450   // should be canonicalized in the dynamic Stringpool.
 451   typedef std::vector<std::string> Deps;
 452
 453   // The name of this version.  This should be canonicalized in the
 454   // dynamic Stringpool.
 455   const char* name_;
 456   // A list of other versions which this version depends upon.
 457   Deps deps_;
 458   // Whether this is the base version.
 459   bool is_base_;
 460   // Whether this version is weak.
 461   bool is_weak_;
 462   // Whether this version is informational.
 463   bool is_info_;
 464   // Whether a version symbol has been created.
 465   bool is_symbol_created_;
 466 };
 467
 468 // A referened version.  This will be associated with a filename by
 469 // Verneed.
 470
 471 class Verneed_version : public Version_base
 472 {
 473  public:
 474   Verneed_version(const char* version)
 475     : version_(version)
 476   { }
 477
 478   // Return the version name.
 479   const char*
 480   version() const
 481   { return this->version_; }
 482
 483   // Clear the weak flag.  This is invalid for a reference.
 484   void
 485   clear_weak()
 486   { gold_unreachable(); }
 487
 488  private:
 489   Verneed_version(const Verneed_version&);
 490   Verneed_version& operator=(const Verneed_version&);
 491
 492   const char* version_;
 493 };
 494
 495 // Version references in a single dynamic object.
 496
 497 class Verneed
 498 {
 499  public:
 500   Verneed(const char* filename)
 501     : filename_(filename), need_versions_()
 502   { }
 503
 504   ~Verneed();
 505
 506   // Return the file name.
 507   const char*
 508   filename() const
 509   { return this->filename_; }
 510
 511   // Return the number of versions.
 512   unsigned int
 513   count_versions() const
 514   { return this->need_versions_.size(); }
 515
 516   // Add a version name.  The name should be canonicalized in the
 517   // dynamic Stringpool.  If the name is already present, this does
 518   // nothing.
 519   Verneed_version*
 520   add_name(const char* name);
 521
 522   // Set the version indexes, starting at INDEX.  Return the updated
 523   // INDEX.
 524   unsigned int
 525   finalize(unsigned int index);
 526
 527   // Write contents to buffer.
 528   template<int size, bool big_endian>
 529   unsigned char*
 530   write(const Stringpool*, bool is_last, unsigned char*) const;
 531
 532  private:
 533   Verneed(const Verneed&);
 534   Verneed& operator=(const Verneed&);
 535
 536   // The type of the list of version names.  Each name should be
 537   // canonicalized in the dynamic Stringpool.
 538   typedef std::vector<Verneed_version*> Need_versions;
 539
 540   // The filename of the dynamic object.  This should be
 541   // canonicalized in the dynamic Stringpool.
 542   const char* filename_;
 543   // The list of version names.
 544   Need_versions need_versions_;
 545 };
 546
 547 // This class handles version definitions and references which go into
 548 // the output file.
 549
 550 class Versions
 551 {
 552  public:
 553   Versions(const Version_script_info&, Stringpool*);
 554
 555   ~Versions();
 556
 557   // SYM is going into the dynamic symbol table and has a version.
 558   // Record the appropriate version information.
 559   void
 560   record_version(const Symbol_table* symtab, Stringpool*, const Symbol* sym);
 561
 562   // Set the version indexes.  DYNSYM_INDEX is the index we should use
 563   // for the next dynamic symbol.  We add new dynamic symbols to SYMS
 564   // and return an updated DYNSYM_INDEX.
 565   unsigned int
 566   finalize(Symbol_table* symtab, unsigned int dynsym_index,
 567            std::vector<Symbol*>* syms);
 568
 569   // Return whether there are any version definitions.
 570   bool
 571   any_defs() const
 572   { return !this->defs_.empty(); }
 573
 574   // Return whether there are any version references.
 575   bool
 576   any_needs() const
 577   { return !this->needs_.empty(); }
 578
 579   // Build an allocated buffer holding the contents of the symbol
 580   // version section (.gnu.version).
 581   template<int size, bool big_endian>
 582   void
 583   symbol_section_contents(const Symbol_table*, const Stringpool*,
 584                           unsigned int local_symcount,
 585                           const std::vector<Symbol*>& syms,
 586                           unsigned char**, unsigned int*) const;
 587
 588   // Build an allocated buffer holding the contents of the version
 589   // definition section (.gnu.version_d).
 590   template<int size, bool big_endian>
 591   void
 592   def_section_contents(const Stringpool*, unsigned char**,
 593                        unsigned int* psize, unsigned int* pentries) const;
 594
 595   // Build an allocated buffer holding the contents of the version
 596   // reference section (.gnu.version_r).
 597   template<int size, bool big_endian>
 598   void
 599   need_section_contents(const Stringpool*, unsigned char**,
 600                         unsigned int* psize, unsigned int* pentries) const;
 601
 602   const Version_script_info&
 603   version_script() const
 604   { return this->version_script_; }
 605
 606  private:
 607   Versions(const Versions&);
 608   Versions& operator=(const Versions&);
 609
 610   // The type of the list of version definitions.
 611   typedef std::vector<Verdef*> Defs;
 612
 613   // The type of the list of version references.
 614   typedef std::vector<Verneed*> Needs;
 615
 616   // Handle a symbol SYM defined with version VERSION.
 617   void
 618   add_def(Stringpool*, const Symbol* sym, const char* version,
 619           Stringpool::Key);
 620
 621   // Add a reference to version NAME in file FILENAME.
 622   void
 623   add_need(Stringpool*, const char* filename, const char* name,
 624            Stringpool::Key);
 625
 626   // Get the dynamic object to use for SYM.
 627   Dynobj*
 628   get_dynobj_for_sym(const Symbol_table*, const Symbol* sym) const;
 629
 630   // Return the version index to use for SYM.
 631   unsigned int
 632   version_index(const Symbol_table*, const Stringpool*,
 633                 const Symbol* sym) const;
 634
 635   // Define the base version of a shared library.
 636   void
 637   define_base_version(Stringpool* dynpool);
 638
 639   // We keep a hash table mapping canonicalized name/version pairs to
 640   // a version base.
 641   typedef std::pair<Stringpool::Key, Stringpool::Key> Key;
 642
 643   struct Version_table_hash
 644   {
 645     size_t
 646     operator()(const Key& k) const
 647     { return k.first + k.second; }
 648   };
 649
 650   struct Version_table_eq
 651   {
 652     bool
 653     operator()(const Key& k1, const Key& k2) const
 654     { return k1.first == k2.first && k1.second == k2.second; }
 655   };
 656
 657   typedef Unordered_map<Key, Version_base*, Version_table_hash,
 658                         Version_table_eq> Version_table;
 659
 660   // The version definitions.
 661   Defs defs_;
 662   // The version references.
 663   Needs needs_;
 664   // The mapping from a canonicalized version/filename pair to a
 665   // version index.  The filename may be NULL.
 666   Version_table version_table_;
 667   // Whether the version indexes have been set.
 668   bool is_finalized_;
 669   // Contents of --version-script, if passed, or NULL.
 670   const Version_script_info& version_script_;
 671   // Whether we need to insert a base version.  This is only used for
 672   // shared libraries and is cleared when the base version is defined.
 673   bool needs_base_version_;
 674 };
 675
 676 } // End namespace gold.
 677
 678 #endif // !defined(GOLD_DYNOBJ_H)