path: root/gold/layout.h

// layout.h -- lay out output file sections for gold  -*- C++ -*-

#ifndef GOLD_LAYOUT_H
#define GOLD_LAYOUT_H

#include <list>
#include <string>
#include <utility>
#include <vector>

#include "options.h"
#include "workqueue.h"
#include "object.h"
#include "stringpool.h"

namespace gold
{

class Input_objects;
class Symbol_table;
class Output_section;
class Output_section_symtab;
class Output_section_headers;
class Output_segment;
class Output_data;

// This Task handles mapping the input sections to output sections and
// laying them out in memory.

class Layout_task : public Task
{
 public:
  // OPTIONS is the command line options, INPUT_OBJECTS is the list of
  // input objects, THIS_BLOCKER is a token which blocks this task
  // from executing until all the input symbols have been read.
  Layout_task(const General_options& options,
	      const Input_objects* input_objects,
	      Symbol_table* symtab,
	      Task_token* this_blocker)
    : options_(options), input_objects_(input_objects), symtab_(symtab),
      this_blocker_(this_blocker)
  { }

  ~Layout_task();

  // The standard Task methods.

  Is_runnable_type
  is_runnable(Workqueue*);

  Task_locker*
  locks(Workqueue*);

  void
  run(Workqueue*);

 private:
  Layout_task(const Layout_task&);
  Layout_task& operator=(const Layout_task&);

  const General_options& options_;
  const Input_objects* input_objects_;
  Symbol_table* symtab_;
  Task_token* this_blocker_;
};

// This class handles the details of laying out input sections.

class Layout
{
 public:
  Layout(const General_options& options);

  // Initialize the object.
  void
  init();

  // Given an input section named NAME with data in SHDR from the
  // object file OBJECT, return the output section where this input
  // section should go.  Set *OFFSET to the offset within the output
  // section.
  template<int size, bool big_endian>
  Output_section*
  layout(Object *object, const char* name,
	 const elfcpp::Shdr<size, big_endian>& shdr, off_t* offset);

  // Return whether a section is a .gnu.linkonce section, given the
  // section name.
  static inline bool
  is_linkonce(const char* name)
  { return strncmp(name, ".gnu.linkonce", sizeof(".gnu.linkonce") - 1) == 0; }

  // Record the signature of a comdat section, and return whether to
  // include it in the link.  The GROUP parameter is true for a
  // section group signature, false for a signature derived from a
  // .gnu.linkonce section.
  bool
  add_comdat(const char*, bool group);

  // Finalize the layout after all the input sections have been added.
  off_t
  finalize(const Input_objects*, Symbol_table*);

  // The list of segments.

  typedef std::vector<Output_segment*> Segment_list;

  // The list of sections not attached to a segment.

  typedef std::list<Output_section*> Section_list;

  // The list of information to write out which is not attached to
  // either a section or a segment.
  typedef std::list<Output_data*> Data_list;

 private:
  Layout(const Layout&);
  Layout& operator=(const Layout&);

  // Mapping from .gnu.linkonce section names to output section names.
  struct Linkonce_mapping
  {
    const char* from;
    int fromlen;
    const char* to;
  };
  static const Linkonce_mapping linkonce_mapping[];
  static const int linkonce_mapping_count;

  // Find the first read-only PT_LOAD segment, creating one if
  // necessary.
  Output_segment*
  find_first_load_seg();

  // Set the final file offsets of all the segments.
  off_t
  set_segment_offsets(const Target*, Output_segment*);

  // Set the final file offsets of all the sections not associated
  // with a segment.
  off_t
  set_section_offsets(off_t);

  // Create the output sections for the symbol table.
  void
  create_symtab_sections(const Input_objects*, Symbol_table*,
			 Output_section** osymtab,
			 Output_section** ostrtab);

  // Create the .shstrtab section.
  Output_section*
  create_shstrtab();

  // Create the section header table.
  Output_section_headers*
  create_shdrs(int size, off_t);

  // Return whether to include this section in the link.
  template<int size, bool big_endian>
  bool
  include_section(Object* object, const char* name,
		  const elfcpp::Shdr<size, big_endian>&);

  // Return the output section name to use for a linkonce section
  // name.
  static const char*
  linkonce_output_name(const char* name);

  // Create a new Output_section.
  Output_section*
  make_output_section(const char* name, elfcpp::Elf_Word type,
		      elfcpp::Elf_Xword flags);

  // Return whether SEG1 comes before SEG2 in the output file.
  static bool
  segment_precedes(const Output_segment* seg1, const Output_segment* seg2);

  // Map from section flags to segment flags.
  static elfcpp::Elf_Word
  section_flags_to_segment(elfcpp::Elf_Xword flags);

  // A mapping used for group signatures.
  typedef Unordered_map<std::string, bool> Signatures;

  // Mapping from input section name/type/flags to output section.  We
  // use canonicalized strings here.

  typedef std::pair<const char*,
		    std::pair<elfcpp::Elf_Word, elfcpp::Elf_Xword> > Key;

  struct Hash_key
  {
    size_t
    operator()(const Key& k) const;
  };

  typedef Unordered_map<Key, Output_section*, Hash_key> Section_name_map;

  // A comparison class for segments.

  struct Compare_segments
  {
    bool
    operator()(const Output_segment* seg1, const Output_segment* seg2)
    { return Layout::segment_precedes(seg1, seg2); }
  };

  // A reference to the options on the command line.
  const General_options& options_;
  // The output section names.
  Stringpool namepool_;
  // The output symbol names.
  Stringpool sympool_;
  // The list of group sections and linkonce sections which we have seen.
  Signatures signatures_;
  // The mapping from input section name/type/flags to output sections.
  Section_name_map section_name_map_;
  // The list of output segments.
  Segment_list segment_list_;
  // The list of output sections which are not attached to any output
  // segment.
  Section_list section_list_;
};

} // End namespace gold.

#endif // !defined(GOLD_LAYOUT_H)