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// 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 "object.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.

// RELOC_SYMBOL_CHANGES is used for -fsplit-stack support.  If it is

// not NULL, it is a vector indexed by relocation index.  If that

// entry is not NULL, it points to a global symbol which used as the

// symbol for the relocation, ignoring the symbol index in the

// relocation.

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,

    const Reloc_symbol_changes* reloc_symbol_changes)

{

  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

          && (reloc_symbol_changes == NULL

              || (*reloc_symbol_changes)[i] == NULL))

        {

          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.  The symbol must not 

          // correspond to a section we are folding.

          bool is_ordinary;

          unsigned int shndx = psymval->input_shndx(&is_ordinary);

          if (is_ordinary

              && shndx != elfcpp::SHN_UNDEF

              && !object->is_section_included(shndx)

              && !(relinfo->symtab->is_section_folded(object, 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;

          if (reloc_symbol_changes != NULL

              && (*reloc_symbol_changes)[i] != NULL)

            gsym = (*reloc_symbol_changes)[i];

          else

            {

              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, output_section, 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_at_location(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 r_type, Relobj*, unsigned int r_sym)

  {

    // We assume that relocation type 0 is NONE.  Targets which are

    // different must override.

    if (r_type == 0 && r_sym == 0)

      return Relocatable_relocs::RELOC_DISCARD;

    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,

                                                           r_sym);

              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)