gold/common.cc - binutils-gdb - Git at Google

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

 // Copyright (C) 2006-2025 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)
 {
   // 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.
	// common.cc -- handle common symbols for gold

	// Copyright (C) 2006-2025 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)
	{
	// 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.