gold/dynobj.h

   1 // dynobj.h -- dynamic object support for gold   -*- C++ -*-
   2
   3 // Copyright (C) 2006-2020 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   // Return the word size of the object file.
  76   int
  77   elfsize() const
  78   { gold_unreachable(); }
  79
  80   // Return TRUE if this is a big-endian object file.
  81   bool
  82   is_big_endian() const
  83   { gold_unreachable(); }
  84
  85   // Compute the ELF hash code for a string.
  86   static uint32_t
  87   elf_hash(const char*);
  88
  89   // Create a standard ELF hash table, setting *PPHASH and *PHASHLEN.
  90   // DYNSYMS is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the
  91   // number of local dynamic symbols, which is the index of the first
  92   // dynamic gobal symbol.
  93   static void
  94   create_elf_hash_table(const std::vector<Symbol*>& dynsyms,
  95                         unsigned int local_dynsym_count,
  96                         unsigned char** pphash,
  97                         unsigned int* phashlen);
  98
  99   // Create a GNU hash table, setting *PPHASH and *PHASHLEN.  DYNSYMS
 100   // is the global dynamic symbols.  LOCAL_DYNSYM_COUNT is the number
 101   // of local dynamic symbols, which is the index of the first dynamic
 102   // gobal symbol.
 103   static void
 104   create_gnu_hash_table(const std::vector<Symbol*>& dynsyms,
 105                         unsigned int local_dynsym_count,
 106                         unsigned char** pphash, unsigned int* phashlen);
 107
 108  protected:
 109   // Return a pointer to this object.
 110   virtual Dynobj*
 111   do_dynobj()
 112   { return this; }
 113
 114   // Set the DT_SONAME string.
 115   void
 116   set_soname_string(const char* s)
 117   { this->soname_.assign(s); }
 118
 119   // Add an entry to the list of DT_NEEDED strings.
 120   void
 121   add_needed(const char* s)
 122   { this->needed_.push_back(std::string(s)); }
 123
 124  private:
 125   // Compute the GNU hash code for a string.
 126   static uint32_t
 127   gnu_hash(const char*);
 128
 129   // Compute the number of hash buckets to use.
 130   static unsigned int
 131   compute_bucket_count(const std::vector<uint32_t>& hashcodes,
 132                        bool for_gnu_hash_table);
 133
 134   // Sized version of create_elf_hash_table.
 135   template<int size, bool big_endian>
 136   static void
 137   sized_create_elf_hash_table(const std::vector<uint32_t>& bucket,
 138                               const std::vector<uint32_t>& chain,
 139                               unsigned char* phash,
 140                               unsigned int hashlen);
 141
 142   // Sized version of create_gnu_hash_table.
 143   template<int size, bool big_endian>
 144   static void
 145   sized_create_gnu_hash_table(const std::vector<Symbol*>& hashed_dynsyms,
 146                               const std::vector<uint32_t>& dynsym_hashvals,
 147                               unsigned int unhashed_dynsym_count,
 148                               unsigned char** pphash,
 149                               unsigned int* phashlen);
 150
 151   // Values for the has_unknown_needed_entries_ field.
 152   enum Unknown_needed
 153   {
 154     UNKNOWN_NEEDED_UNSET,
 155     UNKNOWN_NEEDED_TRUE,
 156     UNKNOWN_NEEDED_FALSE
 157   };
 158
 159   // The DT_SONAME name, if any.
 160   std::string soname_;
 161   // The list of DT_NEEDED entries.
 162   Needed needed_;
 163   // Whether this dynamic object has any DT_NEEDED entries not seen
 164   // during the link.
 165   Unknown_needed unknown_needed_;
 166 };
 167
 168 // A dynamic object, size and endian specific version.
 169
 170 template<int size, bool big_endian>
 171 class Sized_dynobj : public Dynobj
 172 {
 173  public:
 174   typedef typename Sized_relobj_file<size, big_endian>::Symbols Symbols;
 175
 176   Sized_dynobj(const std::string& name, Input_file* input_file, off_t offset,
 177                const typename elfcpp::Ehdr<size, big_endian>&);
 178
 179   // Set up the object file based on TARGET.
 180   void
 181   setup();
 182
 183   // Read the symbols.
 184   void
 185   do_read_symbols(Read_symbols_data*);
 186
 187   // Lay out the input sections.
 188   void
 189   do_layout(Symbol_table*, Layout*, Read_symbols_data*);
 190
 191   // Add the symbols to the symbol table.
 192   void
 193   do_add_symbols(Symbol_table*, Read_symbols_data*, Layout*);
 194
 195   Archive::Should_include
 196   do_should_include_member(Symbol_table* symtab, Layout*, Read_symbols_data*,
 197                            std::string* why);
 198
 199   // Iterate over global symbols, calling a visitor class V for each.
 200   void
 201   do_for_all_global_symbols(Read_symbols_data* sd,
 202                             Library_base::Symbol_visitor_base* v);
 203
 204   // Iterate over local symbols, calling a visitor class V for each GOT offset
 205   // associated with a local symbol.
 206   void
 207   do_for_all_local_got_entries(Got_offset_list::Visitor* v) const;
 208
 209   // Get the size of a section.
 210   uint64_t
 211   do_section_size(unsigned int shndx)
 212   { return this->elf_file_.section_size(shndx); }
 213
 214   // Get the name of a section.
 215   std::string
 216   do_section_name(unsigned int shndx) const
 217   { return this->elf_file_.section_name(shndx); }
 218
 219   // Return a view of the contents of a section.  Set *PLEN to the
 220   // size.
 221   const unsigned char*
 222   do_section_contents(unsigned int shndx, section_size_type* plen,
 223                       bool cache)
 224   {
 225     Location loc(this->elf_file_.section_contents(shndx));
 226     *plen = convert_to_section_size_type(loc.data_size);
 227     if (*plen == 0)
 228       {
 229         static const unsigned char empty[1] = { '\0' };
 230         return empty;
 231       }
 232     return this->get_view(loc.file_offset, *plen, true, cache);
 233   }
 234
 235   // Return section flags.
 236   uint64_t
 237   do_section_flags(unsigned int shndx)
 238   { return this->elf_file_.section_flags(shndx); }
 239
 240   // Not used for dynobj.
 241   uint64_t
 242   do_section_entsize(unsigned int )
 243   { gold_unreachable(); }
 244
 245   // Return section address.
 246   uint64_t
 247   do_section_address(unsigned int shndx)
 248   { return this->elf_file_.section_addr(shndx); }
 249
 250   // Return section type.
 251   unsigned int
 252   do_section_type(unsigned int shndx)
 253   { return this->elf_file_.section_type(shndx); }
 254
 255   // Return the section link field.
 256   unsigned int
 257   do_section_link(unsigned int shndx)
 258   { return this->elf_file_.section_link(shndx); }
 259
 260   // Return the section link field.
 261   unsigned int
 262   do_section_info(unsigned int shndx)
 263   { return this->elf_file_.section_info(shndx); }
 264
 265   // Return the section alignment.
 266   uint64_t
 267   do_section_addralign(unsigned int shndx)
 268   { return this->elf_file_.section_addralign(shndx); }
 269
 270   // Return the Xindex structure to use.
 271   Xindex*
 272   do_initialize_xindex();
 273
 274   // Get symbol counts.
 275   void
 276   do_get_global_symbol_counts(const Symbol_table*, size_t*, size_t*) const;
 277
 278   // Get the global symbols.
 279   const Symbols*
 280   do_get_global_symbols() const
 281   { return this->symbols_; }
 282
 283  protected:
 284   // Read the symbols.  This is common code for all target-specific
 285   // overrides of do_read_symbols().
 286   void
 287   base_read_symbols(Read_symbols_data*);
 288
 289  private:
 290   // For convenience.
 291   typedef Sized_dynobj<size, big_endian> This;
 292   static const int shdr_size = elfcpp::Elf_sizes<size>::shdr_size;
 293   static const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
 294   static const int dyn_size = elfcpp::Elf_sizes<size>::dyn_size;
 295   typedef elfcpp::Shdr<size, big_endian> Shdr;
 296   typedef elfcpp::Dyn<size, big_endian> Dyn;
 297
 298   // Adjust a section index if necessary.
 299   unsigned int
 300   adjust_shndx(unsigned int shndx)
 301   {
 302     if (shndx >= elfcpp::SHN_LORESERVE)
 303       shndx += this->elf_file_.large_shndx_offset();
 304     return shndx;
 305   }
 306
 307   // Find the dynamic symbol table and the version sections, given the
 308   // section headers.
 309   void
 310   find_dynsym_sections(const unsigned char* pshdrs,
 311                        unsigned int* pversym_shndx,
 312                        unsigned int* pverdef_shndx,
 313                        unsigned int* pverneed_shndx,
 314                        unsigned int* pdynamic_shndx);
 315
 316   // Read the dynamic symbol section SHNDX.
 317   void
 318   read_dynsym_section(const unsigned char* pshdrs, unsigned int shndx,
 319                       elfcpp::SHT type, unsigned int link,
 320                       File_view** view, section_size_type* view_size,
 321                       unsigned int* view_info);
 322
 323   // Read the dynamic tags.
 324   void
 325   read_dynamic(const unsigned char* pshdrs, unsigned int dynamic_shndx,
 326                unsigned int strtab_shndx, const unsigned char* strtabu,
 327                off_t strtab_size);
 328
 329   // Mapping from version number to version name.
 330   typedef std::vector<const char*> Version_map;
 331
 332   // Create the version map.
 333   void
 334   make_version_map(Read_symbols_data* sd, Version_map*) const;
 335
 336   // Add version definitions to the version map.
 337   void
 338   make_verdef_map(Read_symbols_data* sd, Version_map*) const;
 339
 340   // Add version references to the version map.
 341   void
 342   make_verneed_map(Read_symbols_data* sd, Version_map*) const;
 343
 344   // Add an entry to the version map.
 345   void
 346   set_version_map(Version_map*, unsigned int ndx, const char* name) const;
 347
 348   // General access to the ELF file.
 349   elfcpp::Elf_file<size, big_endian, Object> elf_file_;
 350   // The section index of the dynamic symbol table.
 351   unsigned int dynsym_shndx_;
 352   // The entries in the symbol table for the symbols.  We only keep
 353   // this if we need it to print symbol information.
 354   Symbols* symbols_;
 355   // Number of defined symbols.
 356   size_t defined_count_;
 357 };
 358
 359 // A base class for Verdef and Verneed_version which just handles the
 360 // version index which will be stored in the SHT_GNU_versym section.
 361
 362 class Version_base
 363 {
 364  public:
 365   Version_base()
 366     : index_(-1U)
 367   { }
 368
 369   virtual
 370   ~Version_base()
 371   { }
 372
 373   // Return the version index.
 374   unsigned int
 375   index() const
 376   {
 377     gold_assert(this->index_ != -1U);
 378     return this->index_;
 379   }
 380
 381   // Set the version index.
 382   void
 383   set_index(unsigned int index)
 384   {
 385     gold_assert(this->index_ == -1U);
 386     this->index_ = index;
 387   }
 388
 389   // Clear the weak flag in a version definition.
 390   virtual void
 391   clear_weak() = 0;
 392
 393  private:
 394   Version_base(const Version_base&);
 395   Version_base& operator=(const Version_base&);
 396
 397   // The index of the version definition or reference.
 398   unsigned int index_;
 399 };
 400
 401 // This class handles a version being defined in the file we are
 402 // generating.
 403
 404 class Verdef : public Version_base
 405 {
 406  public:
 407   Verdef(const char* name, const std::vector<std::string>& deps,
 408          bool is_base, bool is_weak, bool is_info, bool is_symbol_created)
 409     : name_(name), deps_(deps), is_base_(is_base), is_weak_(is_weak),
 410       is_info_(is_info), is_symbol_created_(is_symbol_created)
 411   { }
 412
 413   // Return the version name.
 414   const char*
 415   name() const
 416   { return this->name_; }
 417
 418   // Return the number of dependencies.
 419   unsigned int
 420   count_dependencies() const
 421   { return this->deps_.size(); }
 422
 423   // Add a dependency to this version.  The NAME should be
 424   // canonicalized in the dynamic Stringpool.
 425   void
 426   add_dependency(const char* name)
 427   { this->deps_.push_back(name); }
 428
 429   // Return whether this definition is weak.
 430   bool
 431   is_weak() const
 432   { return this->is_weak_; }
 433
 434   // Clear the weak flag.
 435   void
 436   clear_weak()
 437   { this->is_weak_ = false; }
 438
 439   // Return whether this definition is informational.
 440   bool
 441   is_info() const
 442   { return this->is_info_; }
 443
 444   // Return whether a version symbol has been created for this
 445   // definition.
 446   bool
 447   is_symbol_created() const
 448   { return this->is_symbol_created_; }
 449
 450   // Write contents to buffer.
 451   template<int size, bool big_endian>
 452   unsigned char*
 453   write(const Stringpool*, bool is_last, unsigned char*) const;
 454
 455  private:
 456   Verdef(const Verdef&);
 457   Verdef& operator=(const Verdef&);
 458
 459   // The type of the list of version dependencies.  Each dependency
 460   // should be canonicalized in the dynamic Stringpool.
 461   typedef std::vector<std::string> Deps;
 462
 463   // The name of this version.  This should be canonicalized in the
 464   // dynamic Stringpool.
 465   const char* name_;
 466   // A list of other versions which this version depends upon.
 467   Deps deps_;
 468   // Whether this is the base version.
 469   bool is_base_;
 470   // Whether this version is weak.
 471   bool is_weak_;
 472   // Whether this version is informational.
 473   bool is_info_;
 474   // Whether a version symbol has been created.
 475   bool is_symbol_created_;
 476 };
 477
 478 // A referened version.  This will be associated with a filename by
 479 // Verneed.
 480
 481 class Verneed_version : public Version_base
 482 {
 483  public:
 484   Verneed_version(const char* version)
 485     : version_(version)
 486   { }
 487
 488   // Return the version name.
 489   const char*
 490   version() const
 491   { return this->version_; }
 492
 493   // Clear the weak flag.  This is invalid for a reference.
 494   void
 495   clear_weak()
 496   { gold_unreachable(); }
 497
 498  private:
 499   Verneed_version(const Verneed_version&);
 500   Verneed_version& operator=(const Verneed_version&);
 501
 502   const char* version_;
 503 };
 504
 505 // Version references in a single dynamic object.
 506
 507 class Verneed
 508 {
 509  public:
 510   Verneed(const char* filename)
 511     : filename_(filename), need_versions_()
 512   { }
 513
 514   ~Verneed();
 515
 516   // Return the file name.
 517   const char*
 518   filename() const
 519   { return this->filename_; }
 520
 521   // Return the number of versions.
 522   unsigned int
 523   count_versions() const
 524   { return this->need_versions_.size(); }
 525
 526   // Add a version name.  The name should be canonicalized in the
 527   // dynamic Stringpool.  If the name is already present, this does
 528   // nothing.
 529   Verneed_version*
 530   add_name(const char* name);
 531
 532   // Set the version indexes, starting at INDEX.  Return the updated
 533   // INDEX.
 534   unsigned int
 535   finalize(unsigned int index);
 536
 537   // Write contents to buffer.
 538   template<int size, bool big_endian>
 539   unsigned char*
 540   write(const Stringpool*, bool is_last, unsigned char*) const;
 541
 542  private:
 543   Verneed(const Verneed&);
 544   Verneed& operator=(const Verneed&);
 545
 546   // The type of the list of version names.  Each name should be
 547   // canonicalized in the dynamic Stringpool.
 548   typedef std::vector<Verneed_version*> Need_versions;
 549
 550   // The filename of the dynamic object.  This should be
 551   // canonicalized in the dynamic Stringpool.
 552   const char* filename_;
 553   // The list of version names.
 554   Need_versions need_versions_;
 555 };
 556
 557 // This class handles version definitions and references which go into
 558 // the output file.
 559
 560 class Versions
 561 {
 562  public:
 563   Versions(const Version_script_info&, Stringpool*);
 564
 565   ~Versions();
 566
 567   // SYM is going into the dynamic symbol table and has a version.
 568   // Record the appropriate version information.
 569   void
 570   record_version(const Symbol_table* symtab, Stringpool*, const Symbol* sym);
 571
 572   // Set the version indexes.  DYNSYM_INDEX is the index we should use
 573   // for the next dynamic symbol.  We add new dynamic symbols to SYMS
 574   // and return an updated DYNSYM_INDEX.
 575   unsigned int
 576   finalize(Symbol_table* symtab, unsigned int dynsym_index,
 577            std::vector<Symbol*>* syms);
 578
 579   // Return whether there are any version definitions.
 580   bool
 581   any_defs() const
 582   { return !this->defs_.empty(); }
 583
 584   // Return whether there are any version references.
 585   bool
 586   any_needs() const
 587   { return !this->needs_.empty(); }
 588
 589   // Build an allocated buffer holding the contents of the symbol
 590   // version section (.gnu.version).
 591   template<int size, bool big_endian>
 592   void
 593   symbol_section_contents(const Symbol_table*, const Stringpool*,
 594                           unsigned int local_symcount,
 595                           const std::vector<Symbol*>& syms,
 596                           unsigned char**, unsigned int*) const;
 597
 598   // Build an allocated buffer holding the contents of the version
 599   // definition section (.gnu.version_d).
 600   template<int size, bool big_endian>
 601   void
 602   def_section_contents(const Stringpool*, unsigned char**,
 603                        unsigned int* psize, unsigned int* pentries) const;
 604
 605   // Build an allocated buffer holding the contents of the version
 606   // reference section (.gnu.version_r).
 607   template<int size, bool big_endian>
 608   void
 609   need_section_contents(const Stringpool*, unsigned char**,
 610                         unsigned int* psize, unsigned int* pentries) const;
 611
 612   const Version_script_info&
 613   version_script() const
 614   { return this->version_script_; }
 615
 616  private:
 617   Versions(const Versions&);
 618   Versions& operator=(const Versions&);
 619
 620   // The type of the list of version definitions.
 621   typedef std::vector<Verdef*> Defs;
 622
 623   // The type of the list of version references.
 624   typedef std::vector<Verneed*> Needs;
 625
 626   // Handle a symbol SYM defined with version VERSION.
 627   void
 628   add_def(Stringpool*, const Symbol* sym, const char* version,
 629           Stringpool::Key);
 630
 631   // Add a reference to version NAME in file FILENAME.
 632   void
 633   add_need(Stringpool*, const char* filename, const char* name,
 634            Stringpool::Key);
 635
 636   // Get the dynamic object to use for SYM.
 637   Dynobj*
 638   get_dynobj_for_sym(const Symbol_table*, const Symbol* sym) const;
 639
 640   // Return the version index to use for SYM.
 641   unsigned int
 642   version_index(const Symbol_table*, const Stringpool*,
 643                 const Symbol* sym) const;
 644
 645   // Define the base version of a shared library.
 646   void
 647   define_base_version(Stringpool* dynpool);
 648
 649   // We keep a hash table mapping canonicalized name/version pairs to
 650   // a version base.
 651   typedef std::pair<Stringpool::Key, Stringpool::Key> Key;
 652
 653   struct Version_table_hash
 654   {
 655     size_t
 656     operator()(const Key& k) const
 657     { return k.first + k.second; }
 658   };
 659
 660   struct Version_table_eq
 661   {
 662     bool
 663     operator()(const Key& k1, const Key& k2) const
 664     { return k1.first == k2.first && k1.second == k2.second; }
 665   };
 666
 667   typedef Unordered_map<Key, Version_base*, Version_table_hash,
 668                         Version_table_eq> Version_table;
 669
 670   // The version definitions.
 671   Defs defs_;
 672   // The version references.
 673   Needs needs_;
 674   // The mapping from a canonicalized version/filename pair to a
 675   // version index.  The filename may be NULL.
 676   Version_table version_table_;
 677   // Whether the version indexes have been set.
 678   bool is_finalized_;
 679   // Contents of --version-script, if passed, or NULL.
 680   const Version_script_info& version_script_;
 681   // Whether we need to insert a base version.  This is only used for
 682   // shared libraries and is cleared when the base version is defined.
 683   bool needs_base_version_;
 684 };
 685
 686 } // End namespace gold.
 687
 688 #endif // !defined(GOLD_DYNOBJ_H)