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

// Copyright 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation; either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

// MA 02110-1301, USA.

#ifndef GOLD_LAYOUT_H

#define GOLD_LAYOUT_H

#include <cstring>

#include <list>

#include <map>

#include <string>

#include <utility>

#include <vector>

#include "script.h"

#include "workqueue.h"

#include "object.h"

#include "dynobj.h"

#include "stringpool.h"

namespace gold

{

class General_options;

class Incremental_inputs;

class Input_objects;

class Mapfile;

class Symbol_table;

class Output_section_data;

class Output_section;

class Output_section_headers;

class Output_segment_headers;

class Output_file_header;

class Output_segment;

class Output_data;

class Output_data_dynamic;

class Output_symtab_xindex;

class Output_reduced_debug_abbrev_section;

class Output_reduced_debug_info_section;

class Eh_frame;

class Target;

// This task function handles mapping the input sections to output

// sections and laying them out in memory.

class Layout_task_runner : public Task_function_runner

{

 public:

  // OPTIONS is the command line options, INPUT_OBJECTS is the list of

  // input objects, SYMTAB is the symbol table, LAYOUT is the layout

  // object.

  Layout_task_runner(const General_options& options,

                     const Input_objects* input_objects,

                     Symbol_table* symtab,

                     Target* target,

                     Layout* layout,

                     Mapfile* mapfile)

    : options_(options), input_objects_(input_objects), symtab_(symtab),

      target_(target), layout_(layout), mapfile_(mapfile)

  { }

  // Run the operation.

  void

  run(Workqueue*, const Task*);

 private:

  Layout_task_runner(const Layout_task_runner&);

  Layout_task_runner& operator=(const Layout_task_runner&);

  const General_options& options_;

  const Input_objects* input_objects_;

  Symbol_table* symtab_;

  Target* target_;

  Layout* layout_;

  Mapfile* mapfile_;

};

// This class holds information about the comdat group or

// .gnu.linkonce section that will be kept for a given signature.

class Kept_section

{

 private:

  // For a comdat group, we build a mapping from the name of each

  // section in the group to the section index and the size in object.

  // When we discard a group in some other object file, we use this

  // map to figure out which kept section the discarded section is

  // associated with.  We then use that mapping when processing relocs

  // against discarded sections.

  struct Comdat_section_info

  {

    // The section index.

    unsigned int shndx;

    // The section size.

    uint64_t size;

    Comdat_section_info(unsigned int a_shndx, uint64_t a_size)

      : shndx(a_shndx), size(a_size)

    { }

  };

  // Most comdat groups have only one or two sections, so we use a

  // std::map rather than an Unordered_map to optimize for that case

  // without paying too heavily for groups with more sections.

  typedef std::map<std::string, Comdat_section_info> Comdat_group;

 public:

  Kept_section()

    : object_(NULL), shndx_(0), is_comdat_(false), is_group_name_(false)

  { this->u_.linkonce_size = 0; }

  // We need to support copies for the signature map in the Layout

  // object, but we should never copy an object after it has been

  // marked as a comdat section.

  Kept_section(const Kept_section& k)

    : object_(k.object_), shndx_(k.shndx_), is_comdat_(false),

      is_group_name_(k.is_group_name_)

  {

    gold_assert(!k.is_comdat_);

    this->u_.linkonce_size = 0;

  }

  ~Kept_section()

  {

    if (this->is_comdat_)

      delete this->u_.group_sections;

  }

  // The object where this section lives.

  Relobj*

  object() const

  { return this->object_; }

  // Set the object.

  void

  set_object(Relobj* object)

  {

    gold_assert(this->object_ == NULL);

    this->object_ = object;

  }

  // The section index.

  unsigned int

  shndx() const

  { return this->shndx_; }

  // Set the section index.

  void

  set_shndx(unsigned int shndx)

  {

    gold_assert(this->shndx_ == 0);

    this->shndx_ = shndx;

  }

  // Whether this is a comdat group.

  bool

  is_comdat() const

  { return this->is_comdat_; }

  // Set that this is a comdat group.

  void

  set_is_comdat()

  {

    gold_assert(!this->is_comdat_);

    this->is_comdat_ = true;

    this->u_.group_sections = new Comdat_group();

  }

  // Whether this is associated with the name of a group or section

  // rather than the symbol name derived from a linkonce section.

  bool

  is_group_name() const

  { return this->is_group_name_; }

  // Note that this represents a comdat group rather than a single

  // linkonce section.

  void

  set_is_group_name()

  { this->is_group_name_ = true; }

  // Add a section to the group list.

  void

  add_comdat_section(const std::string& name, unsigned int shndx,

                     uint64_t size)

  {

    gold_assert(this->is_comdat_);

    Comdat_section_info sinfo(shndx, size);

    this->u_.group_sections->insert(std::make_pair(name, sinfo));

  }

  // Look for a section name in the group list, and return whether it

  // was found.  If found, returns the section index and size.

  bool

  find_comdat_section(const std::string& name, unsigned int *pshndx,

                      uint64_t *psize) const

  {

    gold_assert(this->is_comdat_);

    Comdat_group::const_iterator p = this->u_.group_sections->find(name);

    if (p == this->u_.group_sections->end())

      return false;

    *pshndx = p->second.shndx;

    *psize = p->second.size;

    return true;

  }

  // If there is only one section in the group list, return true, and

  // return the section index and size.

  bool

  find_single_comdat_section(unsigned int *pshndx, uint64_t *psize) const

  {

    gold_assert(this->is_comdat_);

    if (this->u_.group_sections->size() != 1)

      return false;

    Comdat_group::const_iterator p = this->u_.group_sections->begin();

    *pshndx = p->second.shndx;

    *psize = p->second.size;

    return true;

  }

  // Return the size of a linkonce section.

  uint64_t

  linkonce_size() const

  {

    gold_assert(!this->is_comdat_);

    return this->u_.linkonce_size;

  }

  // Set the size of a linkonce section.

  void

  set_linkonce_size(uint64_t size)

  {

    gold_assert(!this->is_comdat_);

    this->u_.linkonce_size = size;

  }

 private:

  // No assignment.

  Kept_section& operator=(const Kept_section&);

  // The object containing the comdat group or .gnu.linkonce section.

  Relobj* object_;

  // Index of the group section for comdats and the section itself for

  // .gnu.linkonce.

  unsigned int shndx_;

  // True if this is for a comdat group rather than a .gnu.linkonce

  // section.

  bool is_comdat_;

  // The Kept_sections are values of a mapping, that maps names to

  // them.  This field is true if this struct is associated with the

  // name of a comdat or .gnu.linkonce, false if it is associated with

  // the name of a symbol obtained from the .gnu.linkonce.* name

  // through some heuristics.

  bool is_group_name_;

  union

  {

    // If the is_comdat_ field is true, this holds a map from names of

    // the sections in the group to section indexes in object_ and to

    // section sizes.

    Comdat_group* group_sections;

    // If the is_comdat_ field is false, this holds the size of the

    // single section.

    uint64_t linkonce_size;

  } u_;

};

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

class Layout

{

 public:

  Layout(int number_of_input_files, Script_options*);

  ~Layout()

  {

    delete this->relaxation_debug_check_;

    delete this->segment_states_;

  }

  // Given an input section SHNDX, named NAME, with data in SHDR, from

  // the object file OBJECT, return the output section where this

  // input section should go.  RELOC_SHNDX is the index of a

  // relocation section which applies to this section, or 0 if none,

  // or -1U if more than one.  RELOC_TYPE is the type of the

  // relocation section if there is one.  Set *OFFSET to the offset

  // within the output section.

  template<int size, bool big_endian>

  Output_section*

  layout(Sized_relobj<size, big_endian> *object, unsigned int shndx,

         const char* name, const elfcpp::Shdr<size, big_endian>& shdr,

         unsigned int reloc_shndx, unsigned int reloc_type, off_t* offset);

  // Layout an input reloc section when doing a relocatable link.  The

  // section is RELOC_SHNDX in OBJECT, with data in SHDR.

  // DATA_SECTION is the reloc section to which it refers.  RR is the

  // relocatable information.

  template<int size, bool big_endian>

  Output_section*

  layout_reloc(Sized_relobj<size, big_endian>* object,

               unsigned int reloc_shndx,

               const elfcpp::Shdr<size, big_endian>& shdr,

               Output_section* data_section,

               Relocatable_relocs* rr);

  // Layout a group section when doing a relocatable link.

  template<int size, bool big_endian>

  void

  layout_group(Symbol_table* symtab,

               Sized_relobj<size, big_endian>* object,

               unsigned int group_shndx,

               const char* group_section_name,

               const char* signature,

               const elfcpp::Shdr<size, big_endian>& shdr,

               elfcpp::Elf_Word flags,

               std::vector<unsigned int>* shndxes);

  // Like layout, only for exception frame sections.  OBJECT is an

  // object file.  SYMBOLS is the contents of the symbol table

  // section, with size SYMBOLS_SIZE.  SYMBOL_NAMES is the contents of

  // the symbol name section, with size SYMBOL_NAMES_SIZE.  SHNDX is a

  // .eh_frame section in OBJECT.  SHDR is the section header.

  // RELOC_SHNDX is the index of a relocation section which applies to

  // this section, or 0 if none, or -1U if more than one.  RELOC_TYPE

  // is the type of the relocation section if there is one.  This

  // returns the output section, and sets *OFFSET to the offset.

  template<int size, bool big_endian>

  Output_section*

  layout_eh_frame(Sized_relobj<size, big_endian>* object,

                  const unsigned char* symbols,

                  off_t symbols_size,

                  const unsigned char* symbol_names,

                  off_t symbol_names_size,

                  unsigned int shndx,

                  const elfcpp::Shdr<size, big_endian>& shdr,

                  unsigned int reloc_shndx, unsigned int reloc_type,

                  off_t* offset);

  // Handle a GNU stack note.  This is called once per input object

  // file.  SEEN_GNU_STACK is true if the object file has a

  // .note.GNU-stack section.  GNU_STACK_FLAGS is the section flags

  // from that section if there was one.

  void

  layout_gnu_stack(bool seen_gnu_stack, uint64_t gnu_stack_flags);

  // Add an Output_section_data to the layout.  This is used for

  // special sections like the GOT section.  IS_DYNAMIC_LINKER_SECTION

  // is true for sections which are used by the dynamic linker, such

  // as dynamic reloc sections.

  Output_section*

  add_output_section_data(const char* name, elfcpp::Elf_Word type,

                          elfcpp::Elf_Xword flags,

                          Output_section_data*, bool is_dynamic_linker_section);

  // Create dynamic sections if necessary.

  void

  create_initial_dynamic_sections(Symbol_table*);

  // Define __start and __stop symbols for output sections.

  void

  define_section_symbols(Symbol_table*);

  // Create automatic note sections.

  void

  create_notes();

  // Create sections for linker scripts.

  void

  create_script_sections()

  { this->script_options_->create_script_sections(this); }

  // Define symbols from any linker script.

  void

  define_script_symbols(Symbol_table* symtab)

  { this->script_options_->add_symbols_to_table(symtab); }

  // Define symbols for group signatures.

  void

  define_group_signatures(Symbol_table*);

  // Return the Stringpool used for symbol names.

  const Stringpool*

  sympool() const

  { return &this->sympool_; }

  // Return the Stringpool used for dynamic symbol names and dynamic

  // tags.

  const Stringpool*

  dynpool() const

  { return &this->dynpool_; }

  // Return the symtab_xindex section used to hold large section

  // indexes for the normal symbol table.

  Output_symtab_xindex*

  symtab_xindex() const

  { return this->symtab_xindex_; }

  // Return the dynsym_xindex section used to hold large section

  // indexes for the dynamic symbol table.

  Output_symtab_xindex*

  dynsym_xindex() const

  { return this->dynsym_xindex_; }

  // 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; }

  // Return true if a section is a debugging section.

  static inline bool

  is_debug_info_section(const char* name)

  {

    // Debugging sections can only be recognized by name.

    return (strncmp(name, ".debug", sizeof(".debug") - 1) == 0

            || strncmp(name, ".gnu.linkonce.wi.",

                       sizeof(".gnu.linkonce.wi.") - 1) == 0

            || strncmp(name, ".line", sizeof(".line") - 1) == 0

            || strncmp(name, ".stab", sizeof(".stab") - 1) == 0);

  }

  // Check if a comdat group or .gnu.linkonce section with the given

  // NAME is selected for the link.  If there is already a section,

  // *KEPT_SECTION is set to point to the signature and the function

  // returns false.  Otherwise, OBJECT, SHNDX,IS_COMDAT, and

  // IS_GROUP_NAME are recorded for this NAME in the layout object,

  // *KEPT_SECTION is set to the internal copy and the function return

  // false.

  bool

  find_or_add_kept_section(const std::string& name, Relobj* object,

                           unsigned int shndx, bool is_comdat,

                           bool is_group_name, Kept_section** kept_section);

  // Finalize the layout after all the input sections have been added.

  off_t

  finalize(const Input_objects*, Symbol_table*, Target*, const Task*);

  // Return whether any sections require postprocessing.

  bool

  any_postprocessing_sections() const

  { return this->any_postprocessing_sections_; }

  // Return the size of the output file.

  off_t

  output_file_size() const

  { return this->output_file_size_; }

  // Return the TLS segment.  This will return NULL if there isn't

  // one.

  Output_segment*

  tls_segment() const

  { return this->tls_segment_; }

  // Return the normal symbol table.

  Output_section*

  symtab_section() const

  {

    gold_assert(this->symtab_section_ != NULL);

    return this->symtab_section_;

  }

  // Return the dynamic symbol table.

  Output_section*

  dynsym_section() const

  {

    gold_assert(this->dynsym_section_ != NULL);

    return this->dynsym_section_;

  }

  // Return the dynamic tags.

  Output_data_dynamic*

  dynamic_data() const

  { return this->dynamic_data_; }

  // Write out the output sections.

  void

  write_output_sections(Output_file* of) const;

  // Write out data not associated with an input file or the symbol

  // table.

  void

  write_data(const Symbol_table*, Output_file*) const;

  // Write out output sections which can not be written until all the

  // input sections are complete.

  void

  write_sections_after_input_sections(Output_file* of);

  // Return an output section named NAME, or NULL if there is none.

  Output_section*

  find_output_section(const char* name) const;

  // Return an output segment of type TYPE, with segment flags SET set

  // and segment flags CLEAR clear.  Return NULL if there is none.

  Output_segment*

  find_output_segment(elfcpp::PT type, elfcpp::Elf_Word set,

                      elfcpp::Elf_Word clear) const;

  // Return the number of segments we expect to produce.

  size_t

  expected_segment_count() const;

  // Set a flag to indicate that an object file uses the static TLS model.

  void

  set_has_static_tls()

  { this->has_static_tls_ = true; }

  // Return true if any object file uses the static TLS model.

  bool

  has_static_tls() const

  { return this->has_static_tls_; }

  // Return the options which may be set by a linker script.

  Script_options*

  script_options()

  { return this->script_options_; }

  const Script_options*

  script_options() const

  { return this->script_options_; }

  // Return the object managing inputs in incremental build. NULL in

  // non-incremental builds.

  Incremental_inputs*

  incremental_inputs()

  { return this->incremental_inputs_; }

  // Compute and write out the build ID if needed.

  void

  write_build_id(Output_file*) const;

  // Rewrite output file in binary format.

  void

  write_binary(Output_file* in) const;

  // Print output sections to the map file.

  void

  print_to_mapfile(Mapfile*) const;

  // Dump statistical information to stderr.

  void

  print_stats() const;

  // A list of segments.

  typedef std::vector<Output_segment*> Segment_list;

  // A list of sections.

  typedef std::vector<Output_section*> Section_list;

  // The list of information to write out which is not attached to

  // either a section or a segment.

  typedef std::vector<Output_data*> Data_list;

  // Store the allocated sections into the section list.  This is used

  // by the linker script code.

  void

  get_allocated_sections(Section_list*) const;

  // Make a section for a linker script to hold data.

  Output_section*

  make_output_section_for_script(const char* name);

  // Make a segment.  This is used by the linker script code.

  Output_segment*

  make_output_segment(elfcpp::Elf_Word type, elfcpp::Elf_Word flags);

  // Return the number of segments.

  size_t

  segment_count() const

  { return this->segment_list_.size(); }

  // Map from section flags to segment flags.

  static elfcpp::Elf_Word

  section_flags_to_segment(elfcpp::Elf_Xword flags);

  // Attach sections to segments.

  void

  attach_sections_to_segments();

  // For relaxation clean up, we need to know output section data created

  // from a linker script.

  void

  new_output_section_data_from_script(Output_section_data* posd)

  {

    if (this->record_output_section_data_from_script_)

      this->script_output_section_data_list_.push_back(posd);

  }

  // Return section list.

  const Section_list&

  section_list() const

  { return this->section_list_; }

 private:

  Layout(const Layout&);

  Layout& operator=(const Layout&);

  // Mapping from input section names to output section names.

  struct Section_name_mapping

  {

    const char* from;

    int fromlen;

    const char* to;

    int tolen;

  };

  static const Section_name_mapping section_name_mapping[];

  static const int section_name_mapping_count;

  // During a relocatable link, a list of group sections and

  // signatures.

  struct Group_signature

  {

    // The group section.

    Output_section* section;

    // The signature.

    const char* signature;

    Group_signature()

      : section(NULL), signature(NULL)

    { }

    Group_signature(Output_section* sectiona, const char* signaturea)

      : section(sectiona), signature(signaturea)

    { }

  };

  typedef std::vector<Group_signature> Group_signatures;

  // Create a note section, filling in the header.

  Output_section*

  create_note(const char* name, int note_type, const char *section_name,

              size_t descsz, bool allocate, size_t* trailing_padding);

  // Create a note section for gold version.

  void

  create_gold_note();

  // Record whether the stack must be executable.

  void

  create_executable_stack_info();

  // Create a build ID note if needed.

  void

  create_build_id();

  // Link .stab and .stabstr sections.

  void

  link_stabs_sections();

  // Create .gnu_incremental_inputs and .gnu_incremental_strtab sections needed

  // for the next run of incremental linking to check what has changed.

  void

  create_incremental_info_sections();

  // Find the first read-only PT_LOAD segment, creating one if

  // necessary.

  Output_segment*

  find_first_load_seg();

  // Count the local symbols in the regular symbol table and the dynamic

  // symbol table, and build the respective string pools.

  void

  count_local_symbols(const Task*, const Input_objects*);

  // Create the output sections for the symbol table.

  void

  create_symtab_sections(const Input_objects*, Symbol_table*,

                         unsigned int, off_t*);

  // Create the .shstrtab section.

  Output_section*

  create_shstrtab();

  // Create the section header table.

  void

  create_shdrs(const Output_section* shstrtab_section, off_t*);

  // Create the dynamic symbol table.

  void

  create_dynamic_symtab(const Input_objects*, Symbol_table*,

                        Output_section** pdynstr,

                        unsigned int* plocal_dynamic_count,

                        std::vector<Symbol*>* pdynamic_symbols,

                        Versions* versions);

  // Assign offsets to each local portion of the dynamic symbol table.

  void

  assign_local_dynsym_offsets(const Input_objects*);

  // Finish the .dynamic section and PT_DYNAMIC segment.

  void

  finish_dynamic_section(const Input_objects*, const Symbol_table*);

  // Create the .interp section and PT_INTERP segment.

  void

  create_interp(const Target* target);

  // Create the version sections.

  void

  create_version_sections(const Versions*,

                          const Symbol_table*,

                          unsigned int local_symcount,

                          const std::vector<Symbol*>& dynamic_symbols,

                          const Output_section* dynstr);