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// gc.h -- garbage collection of unused sections

// Copyright 2009 Free Software Foundation, Inc.

// Written by Sriraman Tallam <tmsriram@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_GC_H

#define GOLD_GC_H

#include <queue>

#include <vector>

#include "elfcpp.h"

#include "symtab.h"

#include "icf.h"

namespace gold

{

class Object;

template<int size, bool big_endian>

class Sized_relobj;

template<int sh_type, int size, bool big_endian>

class Reloc_types;

class Output_section;

class General_options;

class Layout;

typedef std::pair<Object *, unsigned int> Section_id;

class Garbage_collection

{

  struct Section_id_hash

  {

    size_t operator()(const Section_id& loc) const

    { return reinterpret_cast<uintptr_t>(loc.first) ^ loc.second; }

  };

 public:

  typedef Unordered_set<Section_id, Section_id_hash> Sections_reachable;

  typedef std::map<Section_id, Sections_reachable> Section_ref;

  typedef std::queue<Section_id> Worklist_type;

  Garbage_collection()

  : is_worklist_ready_(false)

  { }

  // Accessor methods for the private members.

  Sections_reachable&

  referenced_list()

  { return referenced_list_; }

  Section_ref&

  section_reloc_map()

  { return this->section_reloc_map_; }

  Worklist_type&

  worklist()

  { return this->work_list_; }

  bool

  is_worklist_ready()

  { return this->is_worklist_ready_; }

  void

  worklist_ready()

  { this->is_worklist_ready_ = true; }

  void

  do_transitive_closure();

  bool

  is_section_garbage(Object* obj, unsigned int shndx)

  { return (this->referenced_list().find(Section_id(obj, shndx))

            == this->referenced_list().end()); }

 private:

  Worklist_type work_list_;

  bool is_worklist_ready_;

  Section_ref section_reloc_map_;

  Sections_reachable referenced_list_;

};

// Data to pass between successive invocations of do_layout

// in object.cc while garbage collecting.  This data structure

// is filled by using the data from Read_symbols_data.

struct Symbols_data

{

  // Section headers.

  unsigned char* section_headers_data;

  // Section names.

  unsigned char* section_names_data;

  // Size of section name data in bytes.

  section_size_type section_names_size;

  // Symbol data.

  unsigned char* symbols_data;

  // Size of symbol data in bytes.

  section_size_type symbols_size;

  // Offset of external symbols within symbol data.  This structure

  // sometimes contains only external symbols, in which case this will

  // be zero.  Sometimes it contains all symbols.

  section_offset_type external_symbols_offset;

  // Symbol names.

  unsigned char* symbol_names_data;

  // Size of symbol name data in bytes.

  section_size_type symbol_names_size;

};

// This function implements the generic part of reloc

// processing to map a section to all the sections it

// references through relocs.  It is called only during

// garbage collection (--gc-sections) and identical code

// folding (--icf).

template<int size, bool big_endian, typename Target_type, int sh_type,

         typename Scan>

inline void

gc_process_relocs(

    const General_options& ,

    Symbol_table* symtab,

    Layout*,

    Target_type* ,

    Sized_relobj<size, big_endian>* src_obj,

    unsigned int src_indx,

    const unsigned char* prelocs,

    size_t reloc_count,

    Output_section*,

    bool ,

    size_t local_count,

    const unsigned char* plocal_syms)

{

  Object *dst_obj;

  unsigned int dst_indx;

  typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;

  const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;

  const int sym_size = elfcpp::Elf_sizes<size>::sym_size;

  std::vector<Section_id>* secvec = NULL;

  std::vector<Symbol*>* symvec = NULL;

  std::vector<std::pair<long long, long long> >* addendvec = NULL;

  bool is_icf_tracked = false;

  if (parameters->options().icf_enabled()

      && is_prefix_of(".text.", (src_obj)->section_name(src_indx).c_str()))

    {

      is_icf_tracked = true;

      Section_id src_id(src_obj, src_indx);

      secvec = &symtab->icf()->section_reloc_list()[src_id];

      symvec = &symtab->icf()->symbol_reloc_list()[src_id];

      addendvec = &symtab->icf()->addend_reloc_list()[src_id];

    }

  for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)

    {

      Reltype reloc(prelocs);

      typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();

      unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);

      typename elfcpp::Elf_types<size>::Elf_Swxword addend =

      Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&reloc);

      if (r_sym < local_count)

        {

          gold_assert(plocal_syms != NULL);

          typename elfcpp::Sym<size, big_endian> lsym(plocal_syms

                                                      + r_sym * sym_size);

          unsigned int shndx = lsym.get_st_shndx();

          bool is_ordinary;

          shndx = src_obj->adjust_sym_shndx(r_sym, shndx, &is_ordinary);

          if (!is_ordinary)

            continue;

          dst_obj = src_obj;

          dst_indx = shndx;

          Section_id dst_id(dst_obj, dst_indx);

          if (is_icf_tracked)

            {

              (*secvec).push_back(dst_id);

              (*symvec).push_back(NULL);

              long long symvalue = static_cast<long long>(lsym.get_st_value());

              (*addendvec).push_back(std::make_pair(symvalue,

                                              static_cast<long long>(addend)));

            }

          if (shndx == src_indx)

            continue;

        }

      else

        {

          Symbol* gsym = src_obj->global_symbol(r_sym);

          gold_assert(gsym != NULL);

          if (gsym->is_forwarder())

            gsym = symtab->resolve_forwards(gsym);

          if (gsym->source() != Symbol::FROM_OBJECT)

            continue;

          bool is_ordinary;

          dst_obj = gsym->object();

          dst_indx = gsym->shndx(&is_ordinary);

          if (!is_ordinary)

            continue;

          Section_id dst_id(dst_obj, dst_indx);

          if (is_icf_tracked)

            {

              (*secvec).push_back(dst_id);

              (*symvec).push_back(gsym);

              Sized_symbol<size>* sized_gsym =

                        static_cast<Sized_symbol<size>* >(gsym);

              long long symvalue =

                        static_cast<long long>(sized_gsym->value());

              (*addendvec).push_back(std::make_pair(symvalue,

                                        static_cast<long long>(addend)));

            }

        }

      if (parameters->options().gc_sections())

        {

          Section_id src_id(src_obj, src_indx);

          Section_id dst_id(dst_obj, dst_indx);

          Garbage_collection::Section_ref::iterator map_it;

          map_it = symtab->gc()->section_reloc_map().find(src_id);

          if (map_it == symtab->gc()->section_reloc_map().end())

            {

              symtab->gc()->section_reloc_map()[src_id].insert(dst_id);

            }

          else

            {

              Garbage_collection::Sections_reachable& v(map_it->second);

              v.insert(dst_id);

            }

        }

    }

  return;

}

} // End of namespace gold.

#endif