binutils-gdb/gold/target-reloc.h

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

// Copyright 2006, 2007 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-types.h"

namespace gold
{

// This function implements the generic part of reloc scanning.  This
// is an inline function which takes a class whose member functions
// local() and global() 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);
	  const unsigned int shndx = lsym.get_st_shndx();
	  if (shndx < elfcpp::SHN_LORESERVE
	      && shndx != elfcpp::SHN_UNDEF
	      && !object->is_section_included(lsym.get_st_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);
	}
    }
}

// This function implements the generic part of relocation processing.
// This is an inline function which take a class whose relocate()
// implements the machine specific part of relocation.  We do it this
// way to avoid making a function call for each relocation, and to
// avoid repeating the generic relocation handling code for each
// target.

// 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,
    off_t 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();

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

      off_t offset = 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);
	}
      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 || 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
	  && !parameters->output_is_shared())
	gold_undefined_symbol(sym, relinfo, i, offset);

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

} // End namespace gold.

#endif // !defined(GOLD_TARGET_RELOC_H)