1 // dynobj.h -- dynamic object support for gold   -*- C++ -*-
2 
3 // Copyright (C) 2006-2021 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*
soname()49   soname() const
50   { return this->soname_.c_str(); }
51 
52   // Return the list of DT_NEEDED strings.
53   const Needed&
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
has_unknown_needed_entries()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
set_has_unknown_needed_entries(bool set)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
elfsize()77   elfsize() const
78   { gold_unreachable(); }
79 
80   // Return TRUE if this is a big-endian object file.
81   bool
is_big_endian()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*
do_dynobj()111   do_dynobj()
112   { return this; }
113 
114   // Set the DT_SONAME string.
115   void
set_soname_string(const char * s)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
add_needed(const char * s)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
do_section_size(unsigned int shndx)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
do_section_name(unsigned int shndx)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*
do_section_contents(unsigned int shndx,section_size_type * plen,bool cache)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
do_section_flags(unsigned int shndx)237   do_section_flags(unsigned int shndx)
238   { return this->elf_file_.section_flags(shndx); }
239 
240   // Not used for dynobj.
241   uint64_t
do_section_entsize(unsigned int)242   do_section_entsize(unsigned int )
243   { gold_unreachable(); }
244 
245   // Return section address.
246   uint64_t
do_section_address(unsigned int shndx)247   do_section_address(unsigned int shndx)
248   { return this->elf_file_.section_addr(shndx); }
249 
250   // Return section type.
251   unsigned int
do_section_type(unsigned int shndx)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
do_section_link(unsigned int shndx)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
do_section_info(unsigned int shndx)262   do_section_info(unsigned int shndx)
263   { return this->elf_file_.section_info(shndx); }
264 
265   // Return the section alignment.
266   uint64_t
do_section_addralign(unsigned int shndx)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*
do_get_global_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
adjust_shndx(unsigned int shndx)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:
Version_base()365   Version_base()
366     : index_(-1U)
367   { }
368 
369   virtual
~Version_base()370   ~Version_base()
371   { }
372 
373   // Return the version index.
374   unsigned int
index()375   index() const
376   {
377     gold_assert(this->index_ != -1U);
378     return this->index_;
379   }
380 
381   // Set the version index.
382   void
set_index(unsigned int index)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:
Verdef(const char * name,const std::vector<std::string> & deps,bool is_base,bool is_weak,bool is_info,bool is_symbol_created)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*
name()415   name() const
416   { return this->name_; }
417 
418   // Return the number of dependencies.
419   unsigned int
count_dependencies()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
add_dependency(const char * name)426   add_dependency(const char* name)
427   { this->deps_.push_back(name); }
428 
429   // Return whether this definition is weak.
430   bool
is_weak()431   is_weak() const
432   { return this->is_weak_; }
433 
434   // Clear the weak flag.
435   void
clear_weak()436   clear_weak()
437   { this->is_weak_ = false; }
438 
439   // Return whether this definition is informational.
440   bool
is_info()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
is_symbol_created()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:
Verneed_version(const char * version)484   Verneed_version(const char* version)
485     : version_(version)
486   { }
487 
488   // Return the version name.
489   const char*
version()490   version() const
491   { return this->version_; }
492 
493   // Clear the weak flag.  This is invalid for a reference.
494   void
clear_weak()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:
Verneed(const char * filename)510   Verneed(const char* filename)
511     : filename_(filename), need_versions_()
512   { }
513 
514   ~Verneed();
515 
516   // Return the file name.
517   const char*
filename()518   filename() const
519   { return this->filename_; }
520 
521   // Return the number of versions.
522   unsigned int
count_versions()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
any_defs()581   any_defs() const
582   { return !this->defs_.empty(); }
583 
584   // Return whether there are any version references.
585   bool
any_needs()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&
version_script()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
operatorVersion_table_hash656     operator()(const Key& k) const
657     { return k.first + k.second; }
658   };
659 
660   struct Version_table_eq
661   {
662     bool
operatorVersion_table_eq663     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)
689