gold/layout.h

   1 // layout.h -- lay out output file sections for gold  -*- C++ -*-
   2
   3 #ifndef GOLD_LAYOUT_H
   4 #define GOLD_LAYOUT_H
   5
   6 #include <list>
   7 #include <string>
   8 #include <utility>
   9 #include <vector>
  10
  11 #include "options.h"
  12 #include "workqueue.h"
  13 #include "object.h"
  14 #include "stringpool.h"
  15
  16 namespace gold
  17 {
  18
  19 class Input_objects;
  20 class Symbol_table;
  21 class Output_section;
  22 class Output_section_symtab;
  23 class Output_section_headers;
  24 class Output_segment;
  25 class Output_data;
  26
  27 // This Task handles mapping the input sections to output sections and
  28 // laying them out in memory.
  29
  30 class Layout_task : public Task
  31 {
  32  public:
  33   // OPTIONS is the command line options, INPUT_OBJECTS is the list of
  34   // input objects, THIS_BLOCKER is a token which blocks this task
  35   // from executing until all the input symbols have been read.
  36   Layout_task(const General_options& options,
  37               const Input_objects* input_objects,
  38               Symbol_table* symtab,
  39               Task_token* this_blocker)
  40     : options_(options), input_objects_(input_objects), symtab_(symtab),
  41       this_blocker_(this_blocker)
  42   { }
  43
  44   ~Layout_task();
  45
  46   // The standard Task methods.
  47
  48   Is_runnable_type
  49   is_runnable(Workqueue*);
  50
  51   Task_locker*
  52   locks(Workqueue*);
  53
  54   void
  55   run(Workqueue*);
  56
  57  private:
  58   Layout_task(const Layout_task&);
  59   Layout_task& operator=(const Layout_task&);
  60
  61   const General_options& options_;
  62   const Input_objects* input_objects_;
  63   Symbol_table* symtab_;
  64   Task_token* this_blocker_;
  65 };
  66
  67 // This class handles the details of laying out input sections.
  68
  69 class Layout
  70 {
  71  public:
  72   Layout(const General_options& options);
  73
  74   // Initialize the object.
  75   void
  76   init();
  77
  78   // Given an input section named NAME with data in SHDR from the
  79   // object file OBJECT, return the output section where this input
  80   // section should go.  Set *OFFSET to the offset within the output
  81   // section.
  82   template<int size, bool big_endian>
  83   Output_section*
  84   layout(Object *object, const char* name,
  85          const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);
  86
  87   // Return whether a section is a .gnu.linkonce section, given the
  88   // section name.
  89   static inline bool
  90   is_linkonce(const char* name)
  91   { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }
  92
  93   // Record the signature of a comdat section, and return whether to
  94   // include it in the link.  The GROUP parameter is true for a
  95   // section group signature, false for a signature derived from a
  96   // .gnu.linkonce section.
  97   bool
  98   add_comdat(const char*, bool group);
  99
 100   // Finalize the layout after all the input sections have been added.
 101   off_t
 102   finalize(const Input_objects*, Symbol_table*);
 103
 104   // The list of segments.
 105
 106   typedef std::vector<Output_segment*> Segment_list;
 107
 108   // The list of sections not attached to a segment.
 109
 110   typedef std::list<Output_section*> Section_list;
 111
 112   // The list of information to write out which is not attached to
 113   // either a section or a segment.
 114   typedef std::list<Output_data*> Data_list;
 115
 116  private:
 117   Layout(const Layout&);
 118   Layout& operator=(const Layout&);
 119
 120   // Mapping from .gnu.linkonce section names to output section names.
 121   struct Linkonce_mapping
 122   {
 123     const char* from;
 124     int fromlen;
 125     const char* to;
 126   };
 127   static const Linkonce_mapping linkonce_mapping[];
 128   static const int linkonce_mapping_count;
 129
 130   // Find the first read-only PT_LOAD segment, creating one if
 131   // necessary.
 132   Output_segment*
 133   find_first_load_seg();
 134
 135   // Set the final file offsets of all the segments.
 136   off_t
 137   set_segment_offsets(const Target*, Output_segment*);
 138
 139   // Set the final file offsets of all the sections not associated
 140   // with a segment.
 141   off_t
 142   set_section_offsets(off_t);
 143
 144   // Create the output sections for the symbol table.
 145   void
 146   create_symtab_sections(const Input_objects*, Symbol_table*,
 147                          Output_section** osymtab,
 148                          Output_section** ostrtab);
 149
 150   // Create the .shstrtab section.
 151   Output_section*
 152   create_shstrtab();
 153
 154   // Create the section header table.
 155   Output_section_headers*
 156   create_shdrs(int size, off_t);
 157
 158   // Return whether to include this section in the link.
 159   template<int size, bool big_endian>
 160   bool
 161   include_section(Object* object, const char* name,
 162                   const elfcpp::Shdr<size, big_endian>&);
 163
 164   // Return the output section name to use for a linkonce section
 165   // name.
 166   static const char*
 167   linkonce_output_name(const char* name);
 168
 169   // Create a new Output_section.
 170   Output_section*
 171   make_output_section(const char* name, elfcpp::Elf_Word type,
 172                       elfcpp::Elf_Xword flags);
 173
 174   // Return whether SEG1 comes before SEG2 in the output file.
 175   static bool
 176   segment_precedes(const Output_segment* seg1, const Output_segment* seg2);
 177
 178   // Map from section flags to segment flags.
 179   static elfcpp::Elf_Word
 180   section_flags_to_segment(elfcpp::Elf_Xword flags);
 181
 182   // A mapping used for group signatures.
 183   typedef Unordered_map<std::string, bool> Signatures;
 184
 185   // Mapping from input section name/type/flags to output section.  We
 186   // use canonicalized strings here.
 187
 188   typedef std::pair<const char*,
 189                     std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;
 190
 191   struct Hash_key
 192   {
 193     size_t
 194     operator()(const Key& k) const;
 195   };
 196
 197   typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;
 198
 199   // A comparison class for segments.
 200
 201   struct Compare_segments
 202   {
 203     bool
 204     operator()(const Output_segment* seg1, const Output_segment* seg2)
 205     { return Layout::segment_precedes(seg1, seg2); }
 206   };
 207
 208   // A reference to the options on the command line.
 209   const General_options& options_;
 210   // The output section names.
 211   Stringpool namepool_;
 212   // The output symbol names.
 213   Stringpool sympool_;
 214   // The list of group sections and linkonce sections which we have seen.
 215   Signatures signatures_;
 216   // The mapping from input section name/type/flags to output sections.
 217   Section_name_map section_name_map_;
 218   // The list of output segments.
 219   Segment_list segment_list_;
 220   // The list of output sections which are not attached to any output
 221   // segment.
 222   Section_list section_list_;
 223 };
 224
 225 } // End namespace gold.
 226
 227 #endif // !defined(GOLD_LAYOUT_H)