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// common.cc -- handle common symbols for gold

// Copyright 2006, 2007, 2008, 2009, 2010 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 <algorithm>

#include "workqueue.h"

#include "mapfile.h"

#include "layout.h"

#include "output.h"

#include "symtab.h"

#include "common.h"

namespace gold

{

// Allocate_commons_task methods.

// This task allocates the common symbols.  We arrange to run it

// before anything else which needs to access the symbol table.

Task_token*

Allocate_commons_task::is_runnable()

{

  return NULL;

}

// Release a blocker.

void

Allocate_commons_task::locks(Task_locker* tl)

{

  tl->add(this, this->blocker_);

}

// Allocate the common symbols.

void

Allocate_commons_task::run(Workqueue*)

{

  this->symtab_->allocate_commons(this->layout_, this->mapfile_);

}

// This class is used to sort the common symbol.  We normally put the

// larger common symbols first.  This can be changed by using

// --sort-commons, which tells the linker to sort by alignment.

template<int size>

class Sort_commons

{

 public:

  Sort_commons(const Symbol_table* symtab,

               Symbol_table::Sort_commons_order sort_order)

    : symtab_(symtab), sort_order_(sort_order)

  { }

  bool operator()(const Symbol* a, const Symbol* b) const;

 private:

  // The symbol table.

  const Symbol_table* symtab_;

  // How to sort.

  Symbol_table::Sort_commons_order sort_order_;

};

template<int size>

bool

Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const

{

  if (pa == NULL)

    return false;

  if (pb == NULL)

    return true;

  const Symbol_table* symtab = this->symtab_;

  const Sized_symbol<size>* psa = symtab->get_sized_symbol<size>(pa);

  const Sized_symbol<size>* psb = symtab->get_sized_symbol<size>(pb);

  // The size.

  typename Sized_symbol<size>::Size_type sa = psa->symsize();

  typename Sized_symbol<size>::Size_type sb = psb->symsize();

  // The alignment.

  typename Sized_symbol<size>::Value_type aa = psa->value();

  typename Sized_symbol<size>::Value_type ab = psb->value();

  if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_DESCENDING)

    {

      if (aa < ab)

        return false;

      else if (ab < aa)

        return true;

    }

  else if (this->sort_order_

           == Symbol_table::SORT_COMMONS_BY_ALIGNMENT_ASCENDING)

    {

      if (aa < ab)

        return true;

      else if (ab < aa)

        return false;

    }

  else

    gold_assert(this->sort_order_

                == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING);

  // Sort by descending size.

  if (sa < sb)

    return false;

  else if (sb < sa)

    return true;

  if (this->sort_order_ == Symbol_table::SORT_COMMONS_BY_SIZE_DESCENDING)

    {

      // When the symbols are the same size, we sort them by

      // alignment, largest alignment first.

      if (aa < ab)

        return false;

      else if (ab < aa)

        return true;

    }

  // Otherwise we stabilize the sort by sorting by name.

  return strcmp(psa->name(), psb->name()) < 0;

}

// Allocate the common symbols.

void

Symbol_table::allocate_commons(Layout* layout, Mapfile* mapfile)

{

  Sort_commons_order sort_order;

  if (!parameters->options().user_set_sort_common())

    sort_order = SORT_COMMONS_BY_SIZE_DESCENDING;

  else

    {

      const char* order = parameters->options().sort_common();

      if (*order == '\0' || strcmp(order, "descending") == 0)

        sort_order = SORT_COMMONS_BY_ALIGNMENT_DESCENDING;

      else if (strcmp(order, "ascending") == 0)

        sort_order = SORT_COMMONS_BY_ALIGNMENT_ASCENDING;

      else

        {

          gold_error("invalid --sort-common argument: %s", order);

          sort_order = SORT_COMMONS_BY_SIZE_DESCENDING;

        }

    }

  if (parameters->target().get_size() == 32)

    {

#if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)

      this->do_allocate_commons<32>(layout, mapfile, sort_order);

#else

      gold_unreachable();

#endif

    }

  else if (parameters->target().get_size() == 64)

    {

#if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)

      this->do_allocate_commons<64>(layout, mapfile, sort_order);

#else

      gold_unreachable();

#endif

    }

  else

    gold_unreachable();

}

// Allocated the common symbols, sized version.

template<int size>

void

Symbol_table::do_allocate_commons(Layout* layout, Mapfile* mapfile,

                                  Sort_commons_order sort_order)

{

  if (!this->commons_.empty())

    this->do_allocate_commons_list<size>(layout, COMMONS_NORMAL,

                                         &this->commons_, mapfile,

                                         sort_order);

  if (!this->tls_commons_.empty())

    this->do_allocate_commons_list<size>(layout, COMMONS_TLS,

                                         &this->tls_commons_, mapfile,

                                         sort_order);

  if (!this->small_commons_.empty())

    this->do_allocate_commons_list<size>(layout, COMMONS_SMALL,

                                         &this->small_commons_, mapfile,

                                         sort_order);

  if (!this->large_commons_.empty())

    this->do_allocate_commons_list<size>(layout, COMMONS_LARGE,

                                         &this->large_commons_, mapfile,

                                         sort_order);

}

// Allocate the common symbols in a list.  IS_TLS indicates whether

// these are TLS common symbols.

template<int size>

void

Symbol_table::do_allocate_commons_list(

    Layout* layout,

    Commons_section_type commons_section_type,

    Commons_type* commons,

    Mapfile* mapfile,

    Sort_commons_order sort_order)

{

  typedef typename Sized_symbol<size>::Value_type Value_type;

  typedef typename Sized_symbol<size>::Size_type Size_type;

  // We've kept a list of all the common symbols.  But the symbol may

  // have been resolved to a defined symbol by now.  And it may be a

  // forwarder.  First remove all non-common symbols.

  bool any = false;

  uint64_t addralign = 0;

  for (Commons_type::iterator p = commons->begin();

       p != commons->end();

       ++p)

    {

      Symbol* sym = *p;

      if (sym->is_forwarder())

        {

          sym = this->resolve_forwards(sym);

          *p = sym;

        }

      if (!sym->is_common())

        *p = NULL;

      else

        {

          any = true;

          Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);

          if (ssym->value() > addralign)

            addralign = ssym->value();

        }

    }

  if (!any)

    return;

  // Sort the common symbols.

  std::sort(commons->begin(), commons->end(),

            Sort_commons<size>(this, sort_order));

  // Place them in a newly allocated BSS section.

  elfcpp::Elf_Xword flags = elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC;

  const char* name;

  const char* ds_name;

  switch (commons_section_type)

    {

    case COMMONS_NORMAL:

      name = ".bss";

      ds_name = "** common";

      break;

    case COMMONS_TLS:

      flags |= elfcpp::SHF_TLS;

      name = ".tbss";

      ds_name = "** tls common";

      break;

    case COMMONS_SMALL:

      flags |= parameters->target().small_common_section_flags();

      name = ".sbss";

      ds_name = "** small common";

      break;

    case COMMONS_LARGE:

      flags |= parameters->target().large_common_section_flags();

      name = ".lbss";

      ds_name = "** large common";

      break;

    default:

      gold_unreachable();

    }

  Output_data_space* poc = new Output_data_space(addralign, ds_name);

  Output_section* os = layout->add_output_section_data(name,

                                                       elfcpp::SHT_NOBITS,

                                                       flags, poc,

                                                       ORDER_INVALID,

                                                       false);

  if (os != NULL)

    {

      if (commons_section_type == COMMONS_SMALL)

        os->set_is_small_section();

      else if (commons_section_type == COMMONS_LARGE)

        os->set_is_large_section();

    }

  // Allocate them all.

  off_t off = 0;

  for (Commons_type::iterator p = commons->begin();

       p != commons->end();

       ++p)

    {

      Symbol* sym = *p;

      if (sym == NULL)

        break;

      // Because we followed forwarding symbols above, but we didn't

      // do it reliably before adding symbols to the list, it is

      // possible for us to have the same symbol on the list twice.

      // This can happen in the horrible case where a program defines

      // a common symbol with the same name as a versioned libc

      // symbol.  That will show up here as a symbol which has already

      // been allocated and is therefore no longer a common symbol.

      if (!sym->is_common())

        continue;

      Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);

      // Record the symbol in the map file now, before we change its

      // value.  Pass the size in separately so that we don't have to

      // templatize the map code, which is not performance sensitive.

      if (mapfile != NULL)

        mapfile->report_allocate_common(sym, ssym->symsize());

      off = align_address(off, ssym->value());

      ssym->allocate_common(poc, off);

      off += ssym->symsize();

    }

  poc->set_current_data_size(off);

  commons->clear();

}

} // End namespace gold.