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// merge.cc -- handle section merging for gold

// Copyright 2006, 2007, 2008, 2009, 2010, 2011 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.

#include "gold.h"

#include <cstdlib>

#include <algorithm>

#include "merge.h"

#include "compressed_output.h"

namespace gold

{

// Class Object_merge_map.

// Destructor.

Object_merge_map::~Object_merge_map()

{

  for (Section_merge_maps::iterator p = this->section_merge_maps_.begin();

       p != this->section_merge_maps_.end();

       ++p)

    delete p->second;

}

// Get the Input_merge_map to use for an input section, or NULL.

Object_merge_map::Input_merge_map*

Object_merge_map::get_input_merge_map(unsigned int shndx)

{

  gold_assert(shndx != -1U);

  if (shndx == this->first_shnum_)

    return &this->first_map_;

  if (shndx == this->second_shnum_)

    return &this->second_map_;

  Section_merge_maps::const_iterator p = this->section_merge_maps_.find(shndx);

  if (p != this->section_merge_maps_.end())

    return p->second;

  return NULL;

}

// Get or create the Input_merge_map to use for an input section.

Object_merge_map::Input_merge_map*

Object_merge_map::get_or_make_input_merge_map(const Merge_map* merge_map,

                                              unsigned int shndx)

{

  Input_merge_map* map = this->get_input_merge_map(shndx);

  if (map != NULL)

    {

      // For a given input section in a given object, every mapping

      // must be done with the same Merge_map.

      gold_assert(map->merge_map == merge_map);

      return map;

    }

  // We need to create a new entry.

  if (this->first_shnum_ == -1U)

    {

      this->first_shnum_ = shndx;

      this->first_map_.merge_map = merge_map;

      return &this->first_map_;

    }

  if (this->second_shnum_ == -1U)

    {

      this->second_shnum_ = shndx;

      this->second_map_.merge_map = merge_map;

      return &this->second_map_;

    }

  Input_merge_map* new_map = new Input_merge_map;

  new_map->merge_map = merge_map;

  this->section_merge_maps_[shndx] = new_map;

  return new_map;

}

// Add a mapping.

void

Object_merge_map::add_mapping(const Merge_map* merge_map, unsigned int shndx,

                              section_offset_type input_offset,

                              section_size_type length,

                              section_offset_type output_offset)

{

  Input_merge_map* map = this->get_or_make_input_merge_map(merge_map, shndx);

  // Try to merge the new entry in the last one we saw.

  if (!map->entries.empty())

    {

      Input_merge_entry& entry(map->entries.back());

      // Use section_size_type to avoid signed/unsigned warnings.

      section_size_type input_offset_u = input_offset;

      section_size_type output_offset_u = output_offset;

      // If this entry is not in order, we need to sort the vector

      // before looking anything up.

      if (input_offset_u < entry.input_offset + entry.length)

        {

          gold_assert(input_offset < entry.input_offset);

          gold_assert(input_offset_u + length

                      <= static_cast<section_size_type>(entry.input_offset));

          map->sorted = false;

        }

      else if (entry.input_offset + entry.length == input_offset_u

               && (output_offset == -1

                   ? entry.output_offset == -1

                   : entry.output_offset + entry.length == output_offset_u))

        {

          entry.length += length;

          return;

        }

    }

  Input_merge_entry entry;

  entry.input_offset = input_offset;

  entry.length = length;

  entry.output_offset = output_offset;

  map->entries.push_back(entry);

}

// Get the output offset for an input address.

bool

Object_merge_map::get_output_offset(const Merge_map* merge_map,

                                    unsigned int shndx,

                                    section_offset_type input_offset,

                                    section_offset_type* output_offset)

{

  Input_merge_map* map = this->get_input_merge_map(shndx);

  if (map == NULL

      || (merge_map != NULL && map->merge_map != merge_map))

    return false;

  if (!map->sorted)

    {

      std::sort(map->entries.begin(), map->entries.end(),

                Input_merge_compare());

      map->sorted = true;

    }

  Input_merge_entry entry;

  entry.input_offset = input_offset;

  std::vector<Input_merge_entry>::const_iterator p =

    std::lower_bound(map->entries.begin(), map->entries.end(),

                     entry, Input_merge_compare());

  if (p == map->entries.end() || p->input_offset > input_offset)

    {

      if (p == map->entries.begin())

        return false;

      --p;

      gold_assert(p->input_offset <= input_offset);

    }

  if (input_offset - p->input_offset

      >= static_cast<section_offset_type>(p->length))

    return false;

  *output_offset = p->output_offset;

  if (*output_offset != -1)

    *output_offset += (input_offset - p->input_offset);

  return true;

}

// Return whether this is the merge map for section SHNDX.

inline bool

Object_merge_map::is_merge_section_for(const Merge_map* merge_map,

                                       unsigned int shndx)

{

  Input_merge_map* map = this->get_input_merge_map(shndx);

  return map != NULL && map->merge_map == merge_map;

}

// Initialize a mapping from input offsets to output addresses.

template<int size>

void

Object_merge_map::initialize_input_to_output_map(

    unsigned int shndx,

    typename elfcpp::Elf_types<size>::Elf_Addr starting_address,

    Unordered_map<section_offset_type,

                  typename elfcpp::Elf_types<size>::Elf_Addr>* initialize_map)

{

  Input_merge_map* map = this->get_input_merge_map(shndx);

  gold_assert(map != NULL);

  gold_assert(initialize_map->empty());

  // We know how many entries we are going to add.

  // reserve_unordered_map takes an expected count of buckets, not a

  // count of elements, so double it to try to reduce collisions.

  reserve_unordered_map(initialize_map, map->entries.size() * 2);

  for (Input_merge_map::Entries::const_iterator p = map->entries.begin();

       p != map->entries.end();

       ++p)

    {

      section_offset_type output_offset = p->output_offset;

      if (output_offset != -1)

        output_offset += starting_address;

      else

        {

          // If we see a relocation against an address we have chosen

          // to discard, we relocate to zero.  FIXME: We could also

          // issue a warning in this case; that would require

          // reporting this somehow and checking it in the routines in

          // reloc.h.

          output_offset = 0;

        }

      initialize_map->insert(std::make_pair(p->input_offset, output_offset));

    }

}

// Class Merge_map.

// Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in input

// section SHNDX in object OBJECT to an OUTPUT_OFFSET in merged data

// in an output section.

void

Merge_map::add_mapping(Relobj* object, unsigned int shndx,

                       section_offset_type offset, section_size_type length,

                       section_offset_type output_offset)

{

  gold_assert(object != NULL);

  Object_merge_map* object_merge_map = object->merge_map();

  if (object_merge_map == NULL)

    {

      object_merge_map = new Object_merge_map();

      object->set_merge_map(object_merge_map);

    }

  object_merge_map->add_mapping(this, shndx, offset, length, output_offset);

}

// Return the output offset for an input address.  The input address

// is at offset OFFSET in section SHNDX in OBJECT.  This sets

// *OUTPUT_OFFSET to the offset in the merged data in the output

// section.  This returns true if the mapping is known, false

// otherwise.

bool

Merge_map::get_output_offset(const Relobj* object, unsigned int shndx,

                             section_offset_type offset,

                             section_offset_type* output_offset) const

{

  Object_merge_map* object_merge_map = object->merge_map();

  if (object_merge_map == NULL)

    return false;

  return object_merge_map->get_output_offset(this, shndx, offset,

                                             output_offset);

}

// Return whether this is the merge section for SHNDX in OBJECT.

bool

Merge_map::is_merge_section_for(const Relobj* object, unsigned int shndx) const

{

  Object_merge_map* object_merge_map = object->merge_map();

  if (object_merge_map == NULL)

    return false;

  return object_merge_map->is_merge_section_for(this, shndx);

}

// Class Output_merge_base.

// Return the output offset for an input offset.  The input address is

// at offset OFFSET in section SHNDX in OBJECT.  If we know the

// offset, set *POUTPUT and return true.  Otherwise return false.

bool

Output_merge_base::do_output_offset(const Relobj* object,

                                    unsigned int shndx,

                                    section_offset_type offset,

                                    section_offset_type* poutput) const

{

  return this->merge_map_.get_output_offset(object, shndx, offset, poutput);

}

// Return whether this is the merge section for SHNDX in OBJECT.

bool

Output_merge_base::do_is_merge_section_for(const Relobj* object,

                                           unsigned int shndx) const

{

  return this->merge_map_.is_merge_section_for(object, shndx);

}

// Record a merged input section for script processing.

void

Output_merge_base::record_input_section(Relobj* relobj, unsigned int shndx)

{

  gold_assert(this->keeps_input_sections_ && relobj != NULL);

  // If this is the first input section, record it.  We need do this because

  // this->input_sections_ is unordered.

  if (this->first_relobj_ == NULL)

    {

      this->first_relobj_ = relobj;

      this->first_shndx_ = shndx;

    }

  std::pair<Input_sections::iterator, bool> result =

    this->input_sections_.insert(Section_id(relobj, shndx));

  // We should insert a merge section once only.

  gold_assert(result.second);

}

// Class Output_merge_data.

// Compute the hash code for a fixed-size constant.

size_t

Output_merge_data::Merge_data_hash::operator()(Merge_data_key k) const

{

  const unsigned char* p = this->pomd_->constant(k);

  section_size_type entsize =

    convert_to_section_size_type(this->pomd_->entsize());

  // Fowler/Noll/Vo (FNV) hash (type FNV-1a).

  if (sizeof(size_t) == 8)

    {

      size_t result = static_cast<size_t>(14695981039346656037ULL);

      for (section_size_type i = 0; i < entsize; ++i)

        {

          result &= (size_t) *p++;

          result *= 1099511628211ULL;

        }

      return result;

    }

  else

    {

      size_t result = 2166136261UL;

      for (section_size_type i = 0; i < entsize; ++i)

        {

          result ^= (size_t) *p++;

          result *= 16777619UL;

        }

      return result;

    }

}

// Return whether one hash table key equals another.

bool

Output_merge_data::Merge_data_eq::operator()(Merge_data_key k1,

                                             Merge_data_key k2) const

{

  const unsigned char* p1 = this->pomd_->constant(k1);

  const unsigned char* p2 = this->pomd_->constant(k2);

  return memcmp(p1, p2, this->pomd_->entsize()) == 0;

}

// Add a constant to the end of the section contents.

void

Output_merge_data::add_constant(const unsigned char* p)

{

  section_size_type entsize = convert_to_section_size_type(this->entsize());

  section_size_type addralign =

    convert_to_section_size_type(this->addralign());

  section_size_type addsize = std::max(entsize, addralign);

  if (this->len_ + addsize > this->alc_)

    {

      if (this->alc_ == 0)

        this->alc_ = 128 * addsize;

      else

        this->alc_ *= 2;

      this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->alc_));

      if (this->p_ == NULL)

        gold_nomem();

    }

  memcpy(this->p_ + this->len_, p, entsize);

  if (addsize > entsize)

    memset(this->p_ + this->len_ + entsize, 0, addsize - entsize);

  this->len_ += addsize;

}

// Add the input section SHNDX in OBJECT to a merged output section

// which holds fixed length constants.  Return whether we were able to

// handle the section; if not, it will be linked as usual without

// constant merging.

bool

Output_merge_data::do_add_input_section(Relobj* object, unsigned int shndx)

{

  section_size_type len;

  bool is_new;

  const unsigned char* p = object->decompressed_section_contents(shndx, &len,

                                                                 &is_new);

  section_size_type entsize = convert_to_section_size_type(this->entsize());

  if (len % entsize != 0)

    {

      if (is_new)

        delete[] p;

      return false;

    }

  this->input_count_ += len / entsize;

  for (section_size_type i = 0; i < len; i += entsize, p += entsize)

    {

      // Add the constant to the section contents.  If we find that it

      // is already in the hash table, we will remove it again.

      Merge_data_key k = this->len_;

      this->add_constant(p);

      std::pair<Merge_data_hashtable::iterator, bool> ins =

        this->hashtable_.insert(k);

      if (!ins.second)

        {

          // Key was already present.  Remove the copy we just added.

          this->len_ -= entsize;

          k = *ins.first;

        }

      // Record the offset of this constant in the output section.

      this->add_mapping(object, shndx, i, entsize, k);

    }

  // For script processing, we keep the input sections.

  if (this->keeps_input_sections())

    record_input_section(object, shndx);

  if (is_new)

    delete[] p;

  return true;

}

// Set the final data size in a merged output section with fixed size

// constants.

void

Output_merge_data::set_final_data_size()

{

  // Release the memory we don't need.

  this->p_ = static_cast<unsigned char*>(realloc(this->p_, this->len_));

  // An Output_merge_data object may be empty and realloc is allowed

  // to return a NULL pointer in this case.  An Output_merge_data is empty

  // if all its input sections have sizes that are not multiples of entsize.

  gold_assert(this->p_ != NULL || this->len_ == 0);

  this->set_data_size(this->len_);

}

// Write the data of a merged output section with fixed size constants

// to the file.

void

Output_merge_data::do_write(Output_file* of)

{

  of->write(this->offset(), this->p_, this->len_);

}

// Write the data to a buffer.

void

Output_merge_data::do_write_to_buffer(unsigned char* buffer)

{

  memcpy(buffer, this->p_, this->len_);

}

// Print merge stats to stderr.

void

Output_merge_data::do_print_merge_stats(const char* section_name)

{

  fprintf(stderr,

          _("%s: %s merged constants size: %lu; input: %zu; output: %zu\n"),

          program_name, section_name,

          static_cast<unsigned long>(this->entsize()),

          this->input_count_, this->hashtable_.size());

}

// Class Output_merge_string.

// Add an input section to a merged string section.

template<typename Char_type>

bool

Output_merge_string<Char_type>::do_add_input_section(Relobj* object,

                                                     unsigned int shndx)

{

  section_size_type len;

  bool is_new;

  const unsigned char* pdata = object->decompressed_section_contents(shndx,

                                                                     &len,

                                                                     &is_new);

  const Char_type* p = reinterpret_cast<const Char_type*>(pdata);

  const Char_type* pend = p + len / sizeof(Char_type);

  const Char_type* pend0 = pend;

  if (len % sizeof(Char_type) != 0)

    {

      object->error(_("mergeable string section length not multiple of "

                      "character size"));

      if (is_new)

        delete[] pdata;

      return false;

    }

  if (pend[-1] != 0)

    {

      gold_warning(_("%s: last entry in mergeable string section '%s' "

                     "not null terminated"),

                   object->name().c_str(),

                   object->section_name(shndx).c_str());

      // Find the end of the last NULL-terminated string in the buffer.

      while (pend0 > p && pend0[-1] != 0)

        --pend0;

    }

  Merged_strings_list* merged_strings_list =

      new Merged_strings_list(object, shndx);

  this->merged_strings_lists_.push_back(merged_strings_list);

  Merged_strings& merged_strings = merged_strings_list->merged_strings;

  // Count the number of strings in the section and size the list.

  size_t count = 0;

  for (const Char_type* pt = p; pt < pend0; pt += string_length(pt) + 1)

    ++count;

  if (pend0 < pend)

    ++count;

  merged_strings.reserve(count + 1);

  // The index I is in bytes, not characters.

  section_size_type i = 0;

  while (p < pend0)

    {

      size_t len = string_length(p);

      Stringpool::Key key;

      this->stringpool_.add_with_length(p, len, true, &key);

      merged_strings.push_back(Merged_string(i, key));

      p += len + 1;

      i += (len + 1) * sizeof(Char_type);

    }

  if (p < pend)

    {

      size_t len = pend - p;

      Stringpool::Key key;

      this->stringpool_.add_with_length(p, len, true, &key);

      merged_strings.push_back(Merged_string(i, key));

      i += (len + 1) * sizeof(Char_type);

    }

  // Record the last offset in the input section so that we can

  // compute the length of the last string.

  merged_strings.push_back(Merged_string(i, 0));

  this->input_count_ += count;

  this->input_size_ += len;

  // For script processing, we keep the input sections.

  if (this->keeps_input_sections())

    record_input_section(object, shndx);

  if (is_new)

    delete[] pdata;

  return true;

}

// Finalize the mappings from the input sections to the output

// section, and return the final data size.

template<typename Char_type>

section_size_type

Output_merge_string<Char_type>::finalize_merged_data()

{

  this->stringpool_.set_string_offsets();

  for (typename Merged_strings_lists::const_iterator l =

         this->merged_strings_lists_.begin();

       l != this->merged_strings_lists_.end();

       ++l)

    {

      section_offset_type last_input_offset = 0;

      section_offset_type last_output_offset = 0;

      for (typename Merged_strings::const_iterator p =

             (*l)->merged_strings.begin();

           p != (*l)->merged_strings.end();

           ++p)

        {

          section_size_type length = p->offset - last_input_offset;

          if (length > 0)

            this->add_mapping((*l)->object, (*l)->shndx, last_input_offset,

                              length, last_output_offset);

          last_input_offset = p->offset;

          if (p->stringpool_key != 0)

            last_output_offset =

                this->stringpool_.get_offset_from_key(p->stringpool_key);

        }

      delete *l;

    }

  // Save some memory.  This also ensures that this function will work

  // if called twice, as may happen if Layout::set_segment_offsets

  // finds a better alignment.

  this->merged_strings_lists_.clear();

  return this->stringpool_.get_strtab_size();

}

template<typename Char_type>

void

Output_merge_string<Char_type>::set_final_data_size()

{

  const off_t final_data_size = this->finalize_merged_data();

  this->set_data_size(final_data_size);

}

// Write out a merged string section.

template<typename Char_type>

void

Output_merge_string<Char_type>::do_write(Output_file* of)

{

  this->stringpool_.write(of, this->offset());

}

// Write a merged string section to a buffer.