Subversion Repositories scarts

// copy-relocs.cc -- handle COPY relocations for gold.

// 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.

#include "gold.h"

#include "symtab.h"

#include "copy-relocs.h"

namespace gold

{

// Copy_relocs::Copy_reloc_entry methods.

// Emit the reloc if appropriate.

template<int sh_type, int size, bool big_endian>

void

Copy_relocs<sh_type, size, big_endian>::Copy_reloc_entry::emit(

    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)

{

  // If the symbol is no longer defined in a dynamic object, then we

  // emitted a COPY relocation, and we do not want to emit this

  // dynamic relocation.

  if (this->sym_->is_from_dynobj())

    reloc_section->add_global(this->sym_, this->reloc_type_,

                              this->output_section_, this->relobj_,

                              this->shndx_, this->address_,

                              this->addend_);

}

// Copy_relocs methods.

// Handle a relocation against a symbol which may force us to generate

// a COPY reloc.

template<int sh_type, int size, bool big_endian>

void

Copy_relocs<sh_type, size, big_endian>::copy_reloc(

    Symbol_table* symtab,

    Layout* layout,

    Sized_symbol<size>* sym,

    Sized_relobj<size, big_endian>* object,

    unsigned int shndx,

    Output_section *output_section,

    const Reloc& rel,

    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)

{

  if (this->need_copy_reloc(sym, object, shndx))

    this->emit_copy_reloc(symtab, layout, sym, reloc_section);

  else

    {

      // We may not need a COPY relocation.  Save this relocation to

      // possibly be emitted later.

      this->save(sym, object, shndx, output_section, rel);

    }

}

// Return whether we need a COPY reloc for a relocation against SYM.

// The relocation is begin applied to section SHNDX in OBJECT.

template<int sh_type, int size, bool big_endian>

bool

Copy_relocs<sh_type, size, big_endian>::need_copy_reloc(

    Sized_symbol<size>* sym,

    Sized_relobj<size, big_endian>* object,

    unsigned int shndx) const

{

  // FIXME: Handle -z nocopyrelocs.

  if (sym->symsize() == 0)

    return false;

  // If this is a readonly section, then we need a COPY reloc.

  // Otherwise we can use a dynamic reloc.  Note that calling

  // section_flags here can be slow, as the information is not cached;

  // fortunately we shouldn't see too many potential COPY relocs.

  if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)

    return true;

  return false;

}

// Emit a COPY relocation for SYM.

template<int sh_type, int size, bool big_endian>

void

Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc(

    Symbol_table* symtab,

    Layout* layout,

    Sized_symbol<size>* sym,

    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)

{

  typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize();

  // There is no defined way to determine the required alignment of

  // the symbol.  We know that the symbol is defined in a dynamic

  // object.  We start with the alignment of the section in which it

  // is defined; presumably we do not require an alignment larger than

  // that.  Then we reduce that alignment if the symbol is not aligned

  // within the section.

  gold_assert(sym->is_from_dynobj());

  bool is_ordinary;

  unsigned int shndx = sym->shndx(&is_ordinary);

  gold_assert(is_ordinary);

  typename elfcpp::Elf_types<size>::Elf_WXword addralign =

    sym->object()->section_addralign(shndx);

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

  while ((value & (addralign - 1)) != 0)

    addralign >>= 1;

  if (this->dynbss_ == NULL)

    {

      this->dynbss_ = new Output_data_space(addralign, "** dynbss");

      layout->add_output_section_data(".bss",

                                      elfcpp::SHT_NOBITS,

                                      elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,

                                      this->dynbss_);

    }

  Output_data_space* dynbss = this->dynbss_;

  if (addralign > dynbss->addralign())

    dynbss->set_space_alignment(addralign);

  section_size_type dynbss_size =

    convert_to_section_size_type(dynbss->current_data_size());

  dynbss_size = align_address(dynbss_size, addralign);

  section_size_type offset = dynbss_size;

  dynbss->set_current_data_size(dynbss_size + symsize);

  // Define the symbol as being copied.

  symtab->define_with_copy_reloc(sym, dynbss, offset);

  // Add the COPY relocation to the dynamic reloc section.

  this->add_copy_reloc(sym, offset, reloc_section);

}

// Add a COPY relocation for SYM to RELOC_SECTION.

template<int sh_type, int size, bool big_endian>

void

Copy_relocs<sh_type, size, big_endian>::add_copy_reloc(

    Symbol* sym,

    section_size_type offset,

    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)

{

  reloc_section->add_global(sym, this->copy_reloc_type_, this->dynbss_,

                            offset, 0);

}

// Save a relocation to possibly be emitted later.

template<int sh_type, int size, bool big_endian>

void

Copy_relocs<sh_type, size, big_endian>::save(

    Symbol* sym,

    Sized_relobj<size, big_endian>* object,

    unsigned int shndx,

    Output_section* output_section,

    const Reloc& rel)

{

  unsigned int reloc_type = elfcpp::elf_r_type<size>(rel.get_r_info());

  typename elfcpp::Elf_types<size>::Elf_Addr addend =

    Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&rel);

  this->entries_.push_back(Copy_reloc_entry(sym, reloc_type, object, shndx,

                                            output_section, rel.get_r_offset(),

                                            addend));

}

// Emit any saved relocs.

template<int sh_type, int size, bool big_endian>

void

Copy_relocs<sh_type, size, big_endian>::emit(

    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)

{

  for (typename Copy_reloc_entries::iterator p = this->entries_.begin();

       p != this->entries_.end();

       ++p)

    p->emit(reloc_section);

  // We no longer need the saved information.

  this->entries_.clear();

}

// Instantiate the templates we need.

#ifdef HAVE_TARGET_32_LITTLE

template

class Copy_relocs<elfcpp::SHT_REL, 32, false>;

template

class Copy_relocs<elfcpp::SHT_RELA, 32, false>;

#endif

#ifdef HAVE_TARGET_32_BIG

template

class Copy_relocs<elfcpp::SHT_REL, 32, true>;

template

class Copy_relocs<elfcpp::SHT_RELA, 32, true>;

#endif

#ifdef HAVE_TARGET_64_LITTLE

template

class Copy_relocs<elfcpp::SHT_REL, 64, false>;

template

class Copy_relocs<elfcpp::SHT_RELA, 64, false>;

#endif

#ifdef HAVE_TARGET_64_BIG

template

class Copy_relocs<elfcpp::SHT_REL, 64, true>;

template

class Copy_relocs<elfcpp::SHT_RELA, 64, true>;

#endif

} // End namespace gold.