gold/target-reloc.h - binutils-gdb - Git at Google

 // target-reloc.h -- target specific relocation support  -*- C++ -*-

 // Copyright 2006, 2007, 2008 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.

 #ifndef GOLD_TARGET_RELOC_H
 #define GOLD_TARGET_RELOC_H

 #include "elfcpp.h"
 #include "symtab.h"
 #include "reloc.h"
 #include "reloc-types.h"

 namespace gold
 {

 // This function implements the generic part of reloc scanning.  The
 // template parameter Scan must be a class type which provides two
 // functions: local() and global().  Those functions implement the
 // machine specific part of scanning.  We do it this way to
 // avoidmaking a function call for each relocation, and to avoid
 // repeating the generic code for each target.

 template<int size, bool big_endian, typename Target_type, int sh_type,
 	 typename Scan>
 inline void
 scan_relocs(
     const General_options& options,
     Symbol_table* symtab,
     Layout* layout,
     Target_type* target,
     Sized_relobj<size, big_endian>* object,
     unsigned int data_shndx,
     const unsigned char* prelocs,
     size_t reloc_count,
     Output_section* output_section,
     bool needs_special_offset_handling,
     size_t local_count,
     const unsigned char* plocal_syms)
 {
   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;
   Scan scan;

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

       if (needs_special_offset_handling
 	  && !output_section->is_input_address_mapped(object, data_shndx,
 						      reloc.get_r_offset()))
 	continue;

       typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
       unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
       unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

       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 = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
 	  if (is_ordinary
 	      && shndx != elfcpp::SHN_UNDEF
 	      && !object->is_section_included(shndx))
 	    {
 	      // RELOC is a relocation against a local symbol in a
 	      // section we are discarding.  We can ignore this
 	      // relocation.  It will eventually become a reloc
 	      // against the value zero.
 	      //
 	      // FIXME: We should issue a warning if this is an
 	      // allocated section; is this the best place to do it?
 	      //
 	      // FIXME: The old GNU linker would in some cases look
 	      // for the linkonce section which caused this section to
 	      // be discarded, and, if the other section was the same
 	      // size, change the reloc to refer to the other section.
 	      // That seems risky and weird to me, and I don't know of
 	      // any case where it is actually required.

 	      continue;
 	    }

 	  scan.local(options, symtab, layout, target, object, data_shndx,
 		     output_section, reloc, r_type, lsym);
 	}
       else
 	{
 	  Symbol* gsym = object->global_symbol(r_sym);
 	  gold_assert(gsym != NULL);
 	  if (gsym->is_forwarder())
 	    gsym = symtab->resolve_forwards(gsym);

 	  scan.global(options, symtab, layout, target, object, data_shndx,
 		      output_section, reloc, r_type, gsym);
 	}
     }
 }

 // Behavior for relocations to discarded comdat sections.

 enum Comdat_behavior
 {
   CB_UNDETERMINED,   // Not yet determined -- need to look at section name.
   CB_PRETEND,        // Attempt to map to the corresponding kept section.
   CB_IGNORE,         // Ignore the relocation.
   CB_WARNING         // Print a warning.
 };

 // Decide what the linker should do for relocations that refer to discarded
 // comdat sections.  This decision is based on the name of the section being
 // relocated.

 inline Comdat_behavior
 get_comdat_behavior(const char* name)
 {
   if (Layout::is_debug_info_section(name))
     return CB_PRETEND;
   if (strcmp(name, ".eh_frame") == 0
       || strcmp(name, ".gcc_except_table") == 0)
     return CB_IGNORE;
   return CB_WARNING;
 }

 // This function implements the generic part of relocation processing.
 // The template parameter Relocate must be a class type which provides
 // a single function, relocate(), which implements the machine
 // specific part of a relocation.

 // SIZE is the ELF size: 32 or 64.  BIG_ENDIAN is the endianness of
 // the data.  SH_TYPE is the section type: SHT_REL or SHT_RELA.
 // RELOCATE implements operator() to do a relocation.

 // PRELOCS points to the relocation data.  RELOC_COUNT is the number
 // of relocs.  OUTPUT_SECTION is the output section.
 // NEEDS_SPECIAL_OFFSET_HANDLING is true if input offsets need to be
 // mapped to output offsets.

 // VIEW is the section data, VIEW_ADDRESS is its memory address, and
 // VIEW_SIZE is the size.  These refer to the input section, unless
 // NEEDS_SPECIAL_OFFSET_HANDLING is true, in which case they refer to
 // the output section.

 template<int size, bool big_endian, typename Target_type, int sh_type,
 	 typename Relocate>
 inline void
 relocate_section(
     const Relocate_info<size, big_endian>* relinfo,
     Target_type* target,
     const unsigned char* prelocs,
     size_t reloc_count,
     Output_section* output_section,
     bool needs_special_offset_handling,
     unsigned char* view,
     typename elfcpp::Elf_types<size>::Elf_Addr view_address,
     section_size_type view_size)
 {
   typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
   const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
   Relocate relocate;

   Sized_relobj<size, big_endian>* object = relinfo->object;
   unsigned int local_count = object->local_symbol_count();

   Comdat_behavior comdat_behavior = CB_UNDETERMINED;

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

       section_offset_type offset =
 	convert_to_section_size_type(reloc.get_r_offset());

       if (needs_special_offset_handling)
 	{
 	  offset = output_section->output_offset(relinfo->object,
 						 relinfo->data_shndx,
 						 offset);
 	  if (offset == -1)
 	    continue;
 	}

       typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
       unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
       unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

       const Sized_symbol<size>* sym;

       Symbol_value<size> symval;
       const Symbol_value<size> *psymval;
       if (r_sym < local_count)
 	{
 	  sym = NULL;
 	  psymval = object->local_symbol(r_sym);

           // If the local symbol belongs to a section we are discarding,
           // and that section is a debug section, try to find the
           // corresponding kept section and map this symbol to its
           // counterpart in the kept section.
 	  bool is_ordinary;
 	  unsigned int shndx = psymval->input_shndx(&is_ordinary);
 	  if (is_ordinary
 	      && shndx != elfcpp::SHN_UNDEF
 	      && !object->is_section_included(shndx))
 	    {
 	      if (comdat_behavior == CB_UNDETERMINED)
 	        {
 	          std::string name = object->section_name(relinfo->data_shndx);
 	          comdat_behavior = get_comdat_behavior(name.c_str());
 	        }
 	      if (comdat_behavior == CB_PRETEND)
 	        {
                   bool found;
 	          typename elfcpp::Elf_types<size>::Elf_Addr value =
 	            object->map_to_kept_section(shndx, &found);
 	          if (found)
 	            symval.set_output_value(value + psymval->input_value());
                   else
                     symval.set_output_value(0);
 	        }
 	      else
 	        {
 	          if (comdat_behavior == CB_WARNING)
                     gold_warning_at_location(relinfo, i, offset,
                                              _("Relocation refers to discarded "
                                                "comdat section"));
                   symval.set_output_value(0);
 	        }
 	      symval.set_no_output_symtab_entry();
 	      psymval = &symval;
 	    }
 	}
       else
 	{
 	  const Symbol* gsym = object->global_symbol(r_sym);
 	  gold_assert(gsym != NULL);
 	  if (gsym->is_forwarder())
 	    gsym = relinfo->symtab->resolve_forwards(gsym);

 	  sym = static_cast<const Sized_symbol<size>*>(gsym);
 	  if (sym->has_symtab_index())
 	    symval.set_output_symtab_index(sym->symtab_index());
 	  else
 	    symval.set_no_output_symtab_entry();
 	  symval.set_output_value(sym->value());
 	  psymval = &symval;
 	}

       if (!relocate.relocate(relinfo, target, i, reloc, r_type, sym, psymval,
 			     view + offset, view_address + offset, view_size))
 	continue;

       if (offset < 0 || static_cast<section_size_type>(offset) >= view_size)
 	{
 	  gold_error_at_location(relinfo, i, offset,
 				 _("reloc has bad offset %zu"),
 				 static_cast<size_t>(offset));
 	  continue;
 	}

       if (sym != NULL
 	  && sym->is_undefined()
 	  && sym->binding() != elfcpp::STB_WEAK
           && !target->is_defined_by_abi(sym)
 	  && (!parameters->options().shared()       // -shared
               || parameters->options().defs()))     // -z defs
 	gold_undefined_symbol(sym, relinfo, i, offset);

       if (sym != NULL && sym->has_warning())
 	relinfo->symtab->issue_warning(sym, relinfo, i, offset);
     }
 }

 // This class may be used as a typical class for the
 // Scan_relocatable_reloc parameter to scan_relocatable_relocs.  The
 // template parameter Classify_reloc must be a class type which
 // provides a function get_size_for_reloc which returns the number of
 // bytes to which a reloc applies.  This class is intended to capture
 // the most typical target behaviour, while still permitting targets
 // to define their own independent class for Scan_relocatable_reloc.

 template<int sh_type, typename Classify_reloc>
 class Default_scan_relocatable_relocs
 {
  public:
   // Return the strategy to use for a local symbol which is not a
   // section symbol, given the relocation type.
   inline Relocatable_relocs::Reloc_strategy
   local_non_section_strategy(unsigned int, Relobj*)
   { return Relocatable_relocs::RELOC_COPY; }

   // Return the strategy to use for a local symbol which is a section
   // symbol, given the relocation type.
   inline Relocatable_relocs::Reloc_strategy
   local_section_strategy(unsigned int r_type, Relobj* object)
   {
     if (sh_type == elfcpp::SHT_RELA)
       return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA;
     else
       {
 	Classify_reloc classify;
 	switch (classify.get_size_for_reloc(r_type, object))
 	  {
 	  case 0:
 	    return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0;
 	  case 1:
 	    return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1;
 	  case 2:
 	    return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2;
 	  case 4:
 	    return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4;
 	  case 8:
 	    return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8;
 	  default:
 	    gold_unreachable();
 	  }
       }
   }

   // Return the strategy to use for a global symbol, given the
   // relocation type, the object, and the symbol index.
   inline Relocatable_relocs::Reloc_strategy
   global_strategy(unsigned int, Relobj*, unsigned int)
   { return Relocatable_relocs::RELOC_COPY; }
 };

 // Scan relocs during a relocatable link.  This is a default
 // definition which should work for most targets.
 // Scan_relocatable_reloc must name a class type which provides three
 // functions which return a Relocatable_relocs::Reloc_strategy code:
 // global_strategy, local_non_section_strategy, and
 // local_section_strategy.  Most targets should be able to use
 // Default_scan_relocatable_relocs as this class.

 template<int size, bool big_endian, int sh_type,
 	 typename Scan_relocatable_reloc>
 void
 scan_relocatable_relocs(
     const General_options&,
     Symbol_table*,
     Layout*,
     Sized_relobj<size, big_endian>* object,
     unsigned int data_shndx,
     const unsigned char* prelocs,
     size_t reloc_count,
     Output_section* output_section,
     bool needs_special_offset_handling,
     size_t local_symbol_count,
     const unsigned char* plocal_syms,
     Relocatable_relocs* rr)
 {
   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;
   Scan_relocatable_reloc scan;

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

       Relocatable_relocs::Reloc_strategy strategy;

       if (needs_special_offset_handling
 	  && !output_section->is_input_address_mapped(object, data_shndx,
 						      reloc.get_r_offset()))
 	strategy = Relocatable_relocs::RELOC_DISCARD;
       else
 	{
 	  typename elfcpp::Elf_types<size>::Elf_WXword r_info =
 	    reloc.get_r_info();
 	  const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
 	  const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

 	  if (r_sym >= local_symbol_count)
 	    strategy = scan.global_strategy(r_type, object, r_sym);
 	  else
 	    {
 	      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 = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
 	      if (is_ordinary
 		  && shndx != elfcpp::SHN_UNDEF
 		  && !object->is_section_included(shndx))
 		{
 		  // RELOC is a relocation against a local symbol
 		  // defined in a section we are discarding.  Discard
 		  // the reloc.  FIXME: Should we issue a warning?
 		  strategy = Relocatable_relocs::RELOC_DISCARD;
 		}
 	      else if (lsym.get_st_type() != elfcpp::STT_SECTION)
 		strategy = scan.local_non_section_strategy(r_type, object);
 	      else
 		{
 		  strategy = scan.local_section_strategy(r_type, object);
 		  if (strategy != Relocatable_relocs::RELOC_DISCARD)
                     object->output_section(shndx)->set_needs_symtab_index();
 		}
 	    }
 	}

       rr->set_next_reloc_strategy(strategy);
     }
 }

 // Relocate relocs during a relocatable link.  This is a default
 // definition which should work for most targets.

 template<int size, bool big_endian, int sh_type>
 void
 relocate_for_relocatable(
     const Relocate_info<size, big_endian>* relinfo,
     const unsigned char* prelocs,
     size_t reloc_count,
     Output_section* output_section,
     typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section,
     const Relocatable_relocs* rr,
     unsigned char* view,
     typename elfcpp::Elf_types<size>::Elf_Addr view_address,
     section_size_type,
     unsigned char* reloc_view,
     section_size_type reloc_view_size)
 {
   typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
   typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
   typedef typename Reloc_types<sh_type, size, big_endian>::Reloc_write
     Reltype_write;
   const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
   const Address invalid_address = static_cast<Address>(0) - 1;

   Sized_relobj<size, big_endian>* const object = relinfo->object;
   const unsigned int local_count = object->local_symbol_count();

   unsigned char* pwrite = reloc_view;

   for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
     {
       Relocatable_relocs::Reloc_strategy strategy = rr->strategy(i);
       if (strategy == Relocatable_relocs::RELOC_DISCARD)
 	continue;

       Reltype reloc(prelocs);
       Reltype_write reloc_write(pwrite);

       typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
       const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
       const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

       // Get the new symbol index.

       unsigned int new_symndx;
       if (r_sym < local_count)
 	{
 	  switch (strategy)
 	    {
 	    case Relocatable_relocs::RELOC_COPY:
 	      new_symndx = object->symtab_index(r_sym);
 	      gold_assert(new_symndx != -1U);
 	      break;

 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
 	      {
 		// We are adjusting a section symbol.  We need to find
 		// the symbol table index of the section symbol for
 		// the output section corresponding to input section
 		// in which this symbol is defined.
 		gold_assert(r_sym < local_count);
 		bool is_ordinary;
 		unsigned int shndx =
 		  object->local_symbol_input_shndx(r_sym, &is_ordinary);
 		gold_assert(is_ordinary);
 		Output_section* os = object->output_section(shndx);
 		gold_assert(os != NULL);
 		gold_assert(os->needs_symtab_index());
 		new_symndx = os->symtab_index();
 	      }
 	      break;

 	    default:
 	      gold_unreachable();
 	    }
 	}
       else
 	{
 	  const Symbol* gsym = object->global_symbol(r_sym);
 	  gold_assert(gsym != NULL);
 	  if (gsym->is_forwarder())
 	    gsym = relinfo->symtab->resolve_forwards(gsym);

 	  gold_assert(gsym->has_symtab_index());
 	  new_symndx = gsym->symtab_index();
 	}

       // Get the new offset--the location in the output section where
       // this relocation should be applied.

       Address offset = reloc.get_r_offset();
       Address new_offset;
       if (offset_in_output_section != invalid_address)
 	new_offset = offset + offset_in_output_section;
       else
 	{
           section_offset_type sot_offset =
               convert_types<section_offset_type, Address>(offset);
 	  section_offset_type new_sot_offset =
               output_section->output_offset(object, relinfo->data_shndx,
                                             sot_offset);
 	  gold_assert(new_sot_offset != -1);
           new_offset = new_sot_offset;
 	}

       // In an object file, r_offset is an offset within the section.
       // In an executable or dynamic object, generated by
       // --emit-relocs, r_offset is an absolute address.
       if (!parameters->options().relocatable())
 	{
 	  new_offset += view_address;
 	  if (offset_in_output_section != invalid_address)
 	    new_offset -= offset_in_output_section;
 	}

       reloc_write.put_r_offset(new_offset);
       reloc_write.put_r_info(elfcpp::elf_r_info<size>(new_symndx, r_type));

       // Handle the reloc addend based on the strategy.

       if (strategy == Relocatable_relocs::RELOC_COPY)
 	{
 	  if (sh_type == elfcpp::SHT_RELA)
 	    Reloc_types<sh_type, size, big_endian>::
 	      copy_reloc_addend(&reloc_write,
 				&reloc);
 	}
       else
 	{
 	  // The relocation uses a section symbol in the input file.
 	  // We are adjusting it to use a section symbol in the output
 	  // file.  The input section symbol refers to some address in
 	  // the input section.  We need the relocation in the output
 	  // file to refer to that same address.  This adjustment to
 	  // the addend is the same calculation we use for a simple
 	  // absolute relocation for the input section symbol.

 	  const Symbol_value<size>* psymval = object->local_symbol(r_sym);

 	  unsigned char* padd = view + offset;
 	  switch (strategy)
 	    {
 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
 	      {
 		typename elfcpp::Elf_types<size>::Elf_Swxword addend;
 		addend = Reloc_types<sh_type, size, big_endian>::
 			   get_reloc_addend(&reloc);
 		addend = psymval->value(object, addend);
 		Reloc_types<sh_type, size, big_endian>::
 		  set_reloc_addend(&reloc_write, addend);
 	      }
 	      break;

 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
 	      break;

 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
 	      Relocate_functions<size, big_endian>::rel8(padd, object,
 							 psymval);
 	      break;

 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
 	      Relocate_functions<size, big_endian>::rel16(padd, object,
 							  psymval);
 	      break;

 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
 	      Relocate_functions<size, big_endian>::rel32(padd, object,
 							  psymval);
 	      break;

 	    case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
 	      Relocate_functions<size, big_endian>::rel64(padd, object,
 							  psymval);
 	      break;

 	    default:
 	      gold_unreachable();
 	    }
 	}

       pwrite += reloc_size;
     }

   gold_assert(static_cast<section_size_type>(pwrite - reloc_view)
 	      == reloc_view_size);
 }

 } // End namespace gold.

 #endif // !defined(GOLD_TARGET_RELOC_H)
	// target-reloc.h -- target specific relocation support -- C++ --

	// Copyright 2006, 2007, 2008 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.

	#ifndef GOLD_TARGET_RELOC_H
	#define GOLD_TARGET_RELOC_H

	#include "elfcpp.h"
	#include "symtab.h"
	#include "reloc.h"
	#include "reloc-types.h"

	namespace gold
	{

	// This function implements the generic part of reloc scanning. The
	// template parameter Scan must be a class type which provides two
	// functions: local() and global(). Those functions implement the
	// machine specific part of scanning. We do it this way to
	// avoidmaking a function call for each relocation, and to avoid
	// repeating the generic code for each target.

	template<int size, bool big_endian, typename Target_type, int sh_type,
	typename Scan>
	inline void
	scan_relocs(
	const General_options& options,
	Symbol_table* symtab,
	Layout* layout,
	Target_type* target,
	Sized_relobj<size, big_endian>* object,
	unsigned int data_shndx,
	const unsigned char* prelocs,
	size_t reloc_count,
	Output_section* output_section,
	bool needs_special_offset_handling,
	size_t local_count,
	const unsigned char* plocal_syms)
	{
	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;
	Scan scan;

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

	if (needs_special_offset_handling
	&& !output_section->is_input_address_mapped(object, data_shndx,
	reloc.get_r_offset()))
	continue;

	typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
	unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
	unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

	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 = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
	if (is_ordinary
	&& shndx != elfcpp::SHN_UNDEF
	&& !object->is_section_included(shndx))
	{
	// RELOC is a relocation against a local symbol in a
	// section we are discarding. We can ignore this
	// relocation. It will eventually become a reloc
	// against the value zero.
	//
	// FIXME: We should issue a warning if this is an
	// allocated section; is this the best place to do it?
	//
	// FIXME: The old GNU linker would in some cases look
	// for the linkonce section which caused this section to
	// be discarded, and, if the other section was the same
	// size, change the reloc to refer to the other section.
	// That seems risky and weird to me, and I don't know of
	// any case where it is actually required.

	continue;
	}

	scan.local(options, symtab, layout, target, object, data_shndx,
	output_section, reloc, r_type, lsym);
	}
	else
	{
	Symbol* gsym = object->global_symbol(r_sym);
	gold_assert(gsym != NULL);
	if (gsym->is_forwarder())
	gsym = symtab->resolve_forwards(gsym);

	scan.global(options, symtab, layout, target, object, data_shndx,
	output_section, reloc, r_type, gsym);
	}
	}
	}

	// Behavior for relocations to discarded comdat sections.

	enum Comdat_behavior
	{
	CB_UNDETERMINED, // Not yet determined -- need to look at section name.
	CB_PRETEND, // Attempt to map to the corresponding kept section.
	CB_IGNORE, // Ignore the relocation.
	CB_WARNING // Print a warning.
	};

	// Decide what the linker should do for relocations that refer to discarded
	// comdat sections. This decision is based on the name of the section being
	// relocated.

	inline Comdat_behavior
	get_comdat_behavior(const char* name)
	{
	if (Layout::is_debug_info_section(name))
	return CB_PRETEND;
	if (strcmp(name, ".eh_frame") == 0
	\|\| strcmp(name, ".gcc_except_table") == 0)
	return CB_IGNORE;
	return CB_WARNING;
	}

	// This function implements the generic part of relocation processing.
	// The template parameter Relocate must be a class type which provides
	// a single function, relocate(), which implements the machine
	// specific part of a relocation.

	// SIZE is the ELF size: 32 or 64. BIG_ENDIAN is the endianness of
	// the data. SH_TYPE is the section type: SHT_REL or SHT_RELA.
	// RELOCATE implements operator() to do a relocation.

	// PRELOCS points to the relocation data. RELOC_COUNT is the number
	// of relocs. OUTPUT_SECTION is the output section.
	// NEEDS_SPECIAL_OFFSET_HANDLING is true if input offsets need to be
	// mapped to output offsets.

	// VIEW is the section data, VIEW_ADDRESS is its memory address, and
	// VIEW_SIZE is the size. These refer to the input section, unless
	// NEEDS_SPECIAL_OFFSET_HANDLING is true, in which case they refer to
	// the output section.

	template<int size, bool big_endian, typename Target_type, int sh_type,
	typename Relocate>
	inline void
	relocate_section(
	const Relocate_info<size, big_endian>* relinfo,
	Target_type* target,
	const unsigned char* prelocs,
	size_t reloc_count,
	Output_section* output_section,
	bool needs_special_offset_handling,
	unsigned char* view,
	typename elfcpp::Elf_types<size>::Elf_Addr view_address,
	section_size_type view_size)
	{
	typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
	const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
	Relocate relocate;

	Sized_relobj<size, big_endian>* object = relinfo->object;
	unsigned int local_count = object->local_symbol_count();

	Comdat_behavior comdat_behavior = CB_UNDETERMINED;

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

	section_offset_type offset =
	convert_to_section_size_type(reloc.get_r_offset());

	if (needs_special_offset_handling)
	{
	offset = output_section->output_offset(relinfo->object,
	relinfo->data_shndx,
	offset);
	if (offset == -1)
	continue;
	}

	typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
	unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
	unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

	const Sized_symbol<size>* sym;

	Symbol_value<size> symval;
	const Symbol_value<size> *psymval;
	if (r_sym < local_count)
	{
	sym = NULL;
	psymval = object->local_symbol(r_sym);

	// If the local symbol belongs to a section we are discarding,
	// and that section is a debug section, try to find the
	// corresponding kept section and map this symbol to its
	// counterpart in the kept section.
	bool is_ordinary;
	unsigned int shndx = psymval->input_shndx(&is_ordinary);
	if (is_ordinary
	&& shndx != elfcpp::SHN_UNDEF
	&& !object->is_section_included(shndx))
	{
	if (comdat_behavior == CB_UNDETERMINED)
	{
	std::string name = object->section_name(relinfo->data_shndx);
	comdat_behavior = get_comdat_behavior(name.c_str());
	}
	if (comdat_behavior == CB_PRETEND)
	{
	bool found;
	typename elfcpp::Elf_types<size>::Elf_Addr value =
	object->map_to_kept_section(shndx, &found);
	if (found)
	symval.set_output_value(value + psymval->input_value());
	else
	symval.set_output_value(0);
	}
	else
	{
	if (comdat_behavior == CB_WARNING)
	gold_warning_at_location(relinfo, i, offset,
	_("Relocation refers to discarded "
	"comdat section"));
	symval.set_output_value(0);
	}
	symval.set_no_output_symtab_entry();
	psymval = &symval;
	}
	}
	else
	{
	const Symbol* gsym = object->global_symbol(r_sym);
	gold_assert(gsym != NULL);
	if (gsym->is_forwarder())
	gsym = relinfo->symtab->resolve_forwards(gsym);

	sym = static_cast<const Sized_symbol<size>*>(gsym);
	if (sym->has_symtab_index())
	symval.set_output_symtab_index(sym->symtab_index());
	else
	symval.set_no_output_symtab_entry();
	symval.set_output_value(sym->value());
	psymval = &symval;
	}

	if (!relocate.relocate(relinfo, target, i, reloc, r_type, sym, psymval,
	view + offset, view_address + offset, view_size))
	continue;

	if (offset < 0 \|\| static_cast<section_size_type>(offset) >= view_size)
	{
	gold_error_at_location(relinfo, i, offset,
	_("reloc has bad offset %zu"),
	static_cast<size_t>(offset));
	continue;
	}

	if (sym != NULL
	&& sym->is_undefined()
	&& sym->binding() != elfcpp::STB_WEAK
	&& !target->is_defined_by_abi(sym)
	&& (!parameters->options().shared() // -shared
	\|\| parameters->options().defs())) // -z defs
	gold_undefined_symbol(sym, relinfo, i, offset);

	if (sym != NULL && sym->has_warning())
	relinfo->symtab->issue_warning(sym, relinfo, i, offset);
	}
	}

	// This class may be used as a typical class for the
	// Scan_relocatable_reloc parameter to scan_relocatable_relocs. The
	// template parameter Classify_reloc must be a class type which
	// provides a function get_size_for_reloc which returns the number of
	// bytes to which a reloc applies. This class is intended to capture
	// the most typical target behaviour, while still permitting targets
	// to define their own independent class for Scan_relocatable_reloc.

	template<int sh_type, typename Classify_reloc>
	class Default_scan_relocatable_relocs
	{
	public:
	// Return the strategy to use for a local symbol which is not a
	// section symbol, given the relocation type.
	inline Relocatable_relocs::Reloc_strategy
	local_non_section_strategy(unsigned int, Relobj*)
	{ return Relocatable_relocs::RELOC_COPY; }

	// Return the strategy to use for a local symbol which is a section
	// symbol, given the relocation type.
	inline Relocatable_relocs::Reloc_strategy
	local_section_strategy(unsigned int r_type, Relobj* object)
	{
	if (sh_type == elfcpp::SHT_RELA)
	return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA;
	else
	{
	Classify_reloc classify;
	switch (classify.get_size_for_reloc(r_type, object))
	{
	case 0:
	return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0;
	case 1:
	return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1;
	case 2:
	return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2;
	case 4:
	return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4;
	case 8:
	return Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8;
	default:
	gold_unreachable();
	}
	}
	}

	// Return the strategy to use for a global symbol, given the
	// relocation type, the object, and the symbol index.
	inline Relocatable_relocs::Reloc_strategy
	global_strategy(unsigned int, Relobj*, unsigned int)
	{ return Relocatable_relocs::RELOC_COPY; }
	};

	// Scan relocs during a relocatable link. This is a default
	// definition which should work for most targets.
	// Scan_relocatable_reloc must name a class type which provides three
	// functions which return a Relocatable_relocs::Reloc_strategy code:
	// global_strategy, local_non_section_strategy, and
	// local_section_strategy. Most targets should be able to use
	// Default_scan_relocatable_relocs as this class.

	template<int size, bool big_endian, int sh_type,
	typename Scan_relocatable_reloc>
	void
	scan_relocatable_relocs(
	const General_options&,
	Symbol_table*,
	Layout*,
	Sized_relobj<size, big_endian>* object,
	unsigned int data_shndx,
	const unsigned char* prelocs,
	size_t reloc_count,
	Output_section* output_section,
	bool needs_special_offset_handling,
	size_t local_symbol_count,
	const unsigned char* plocal_syms,
	Relocatable_relocs* rr)
	{
	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;
	Scan_relocatable_reloc scan;

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

	Relocatable_relocs::Reloc_strategy strategy;

	if (needs_special_offset_handling
	&& !output_section->is_input_address_mapped(object, data_shndx,
	reloc.get_r_offset()))
	strategy = Relocatable_relocs::RELOC_DISCARD;
	else
	{
	typename elfcpp::Elf_types<size>::Elf_WXword r_info =
	reloc.get_r_info();
	const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
	const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

	if (r_sym >= local_symbol_count)
	strategy = scan.global_strategy(r_type, object, r_sym);
	else
	{
	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 = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary);
	if (is_ordinary
	&& shndx != elfcpp::SHN_UNDEF
	&& !object->is_section_included(shndx))
	{
	// RELOC is a relocation against a local symbol
	// defined in a section we are discarding. Discard
	// the reloc. FIXME: Should we issue a warning?
	strategy = Relocatable_relocs::RELOC_DISCARD;
	}
	else if (lsym.get_st_type() != elfcpp::STT_SECTION)
	strategy = scan.local_non_section_strategy(r_type, object);
	else
	{
	strategy = scan.local_section_strategy(r_type, object);
	if (strategy != Relocatable_relocs::RELOC_DISCARD)
	object->output_section(shndx)->set_needs_symtab_index();
	}
	}
	}

	rr->set_next_reloc_strategy(strategy);
	}
	}

	// Relocate relocs during a relocatable link. This is a default
	// definition which should work for most targets.

	template<int size, bool big_endian, int sh_type>
	void
	relocate_for_relocatable(
	const Relocate_info<size, big_endian>* relinfo,
	const unsigned char* prelocs,
	size_t reloc_count,
	Output_section* output_section,
	typename elfcpp::Elf_types<size>::Elf_Addr offset_in_output_section,
	const Relocatable_relocs* rr,
	unsigned char* view,
	typename elfcpp::Elf_types<size>::Elf_Addr view_address,
	section_size_type,
	unsigned char* reloc_view,
	section_size_type reloc_view_size)
	{
	typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
	typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype;
	typedef typename Reloc_types<sh_type, size, big_endian>::Reloc_write
	Reltype_write;
	const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size;
	const Address invalid_address = static_cast<Address>(0) - 1;

	Sized_relobj<size, big_endian>* const object = relinfo->object;
	const unsigned int local_count = object->local_symbol_count();

	unsigned char* pwrite = reloc_view;

	for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size)
	{
	Relocatable_relocs::Reloc_strategy strategy = rr->strategy(i);
	if (strategy == Relocatable_relocs::RELOC_DISCARD)
	continue;

	Reltype reloc(prelocs);
	Reltype_write reloc_write(pwrite);

	typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info();
	const unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info);
	const unsigned int r_type = elfcpp::elf_r_type<size>(r_info);

	// Get the new symbol index.

	unsigned int new_symndx;
	if (r_sym < local_count)
	{
	switch (strategy)
	{
	case Relocatable_relocs::RELOC_COPY:
	new_symndx = object->symtab_index(r_sym);
	gold_assert(new_symndx != -1U);
	break;

	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
	{
	// We are adjusting a section symbol. We need to find
	// the symbol table index of the section symbol for
	// the output section corresponding to input section
	// in which this symbol is defined.
	gold_assert(r_sym < local_count);
	bool is_ordinary;
	unsigned int shndx =
	object->local_symbol_input_shndx(r_sym, &is_ordinary);
	gold_assert(is_ordinary);
	Output_section* os = object->output_section(shndx);
	gold_assert(os != NULL);
	gold_assert(os->needs_symtab_index());
	new_symndx = os->symtab_index();
	}
	break;

	default:
	gold_unreachable();
	}
	}
	else
	{
	const Symbol* gsym = object->global_symbol(r_sym);
	gold_assert(gsym != NULL);
	if (gsym->is_forwarder())
	gsym = relinfo->symtab->resolve_forwards(gsym);

	gold_assert(gsym->has_symtab_index());
	new_symndx = gsym->symtab_index();
	}

	// Get the new offset--the location in the output section where
	// this relocation should be applied.

	Address offset = reloc.get_r_offset();
	Address new_offset;
	if (offset_in_output_section != invalid_address)
	new_offset = offset + offset_in_output_section;
	else
	{
	section_offset_type sot_offset =
	convert_types<section_offset_type, Address>(offset);
	section_offset_type new_sot_offset =
	output_section->output_offset(object, relinfo->data_shndx,
	sot_offset);
	gold_assert(new_sot_offset != -1);
	new_offset = new_sot_offset;
	}

	// In an object file, r_offset is an offset within the section.
	// In an executable or dynamic object, generated by
	// --emit-relocs, r_offset is an absolute address.
	if (!parameters->options().relocatable())
	{
	new_offset += view_address;
	if (offset_in_output_section != invalid_address)
	new_offset -= offset_in_output_section;
	}

	reloc_write.put_r_offset(new_offset);
	reloc_write.put_r_info(elfcpp::elf_r_info<size>(new_symndx, r_type));

	// Handle the reloc addend based on the strategy.

	if (strategy == Relocatable_relocs::RELOC_COPY)
	{
	if (sh_type == elfcpp::SHT_RELA)
	Reloc_types<sh_type, size, big_endian>::
	copy_reloc_addend(&reloc_write,
	&reloc);
	}
	else
	{
	// The relocation uses a section symbol in the input file.
	// We are adjusting it to use a section symbol in the output
	// file. The input section symbol refers to some address in
	// the input section. We need the relocation in the output
	// file to refer to that same address. This adjustment to
	// the addend is the same calculation we use for a simple
	// absolute relocation for the input section symbol.

	const Symbol_value<size>* psymval = object->local_symbol(r_sym);

	unsigned char* padd = view + offset;
	switch (strategy)
	{
	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_RELA:
	{
	typename elfcpp::Elf_types<size>::Elf_Swxword addend;
	addend = Reloc_types<sh_type, size, big_endian>::
	get_reloc_addend(&reloc);
	addend = psymval->value(object, addend);
	Reloc_types<sh_type, size, big_endian>::
	set_reloc_addend(&reloc_write, addend);
	}
	break;

	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_0:
	break;

	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_1:
	Relocate_functions<size, big_endian>::rel8(padd, object,
	psymval);
	break;

	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_2:
	Relocate_functions<size, big_endian>::rel16(padd, object,
	psymval);
	break;

	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_4:
	Relocate_functions<size, big_endian>::rel32(padd, object,
	psymval);
	break;

	case Relocatable_relocs::RELOC_ADJUST_FOR_SECTION_8:
	Relocate_functions<size, big_endian>::rel64(padd, object,
	psymval);
	break;

	default:
	gold_unreachable();
	}
	}

	pwrite += reloc_size;
	}

	gold_assert(static_cast<section_size_type>(pwrite - reloc_view)
	== reloc_view_size);
	}

	} // End namespace gold.

	#endif // !defined(GOLD_TARGET_RELOC_H)