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

// Copyright (C) 2006-2024 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <[email protected]>.

// 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)
{
 // 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;
 Output_section* os;

 if (!parameters->incremental_update())
   {
     poc = new Output_data_space(addralign, ds_name);
     os = layout->add_output_section_data(name, elfcpp::SHT_NOBITS, flags,
                                          poc, ORDER_INVALID, false);
   }
 else
   {
     // When doing an incremental update, we need to allocate each common
     // directly from the output section's free list.
     poc = NULL;
     os = layout->find_output_section(name);
   }

 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());

     if (poc != NULL)
       {
         off = align_address(off, ssym->value());
         ssym->allocate_common(poc, off);
         off += ssym->symsize();
       }
     else
       {
         // For an incremental update, allocate from the free list.
         off = os->allocate(ssym->symsize(), ssym->value());
         if (off == -1)
           gold_fallback(_("out of patch space in section %s; "
                           "relink with --incremental-full"),
                         os->name());
         ssym->allocate_common(os, off);
       }
   }

 if (poc != NULL)
   poc->set_current_data_size(off);

 commons->clear();
}

} // End namespace gold.

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