[deliverable/binutils-gdb.git] / gold / copy-relocs.cc

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

// Copyright (C) 2006-2017 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 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_file<size, big_endian>* object,
    unsigned int shndx,
    Output_section* output_section,
    unsigned int r_type,
    typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
    typename elfcpp::Elf_types<size>::Elf_Swxword r_addend,
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  if (this->need_copy_reloc(sym, object, shndx))
    this->make_copy_reloc(symtab, layout, sym, object, 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,
		 r_type, r_offset, r_addend);
    }
}

// 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_file<size, big_endian>* object,
    unsigned int shndx) const
{
  if (!parameters->options().copyreloc())
    return false;

  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,
    Sized_symbol<size>* sym,
    Output_data* posd,
    off_t offset,
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  // Define the symbol as being copied.
  symtab->define_with_copy_reloc(sym, posd, offset);

  // Add the COPY relocation to the dynamic reloc section.
  reloc_section->add_global_generic(sym, this->copy_reloc_type_, posd,
				    offset, 0);
}

// Make a COPY relocation for SYM and emit it.

template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::make_copy_reloc(
    Symbol_table* symtab,
    Layout* layout,
    Sized_symbol<size>* sym,
    Sized_relobj_file<size, big_endian>* object,
    Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
  // We should not be here if -z nocopyreloc is given.
  gold_assert(parameters->options().copyreloc());

  gold_assert(sym->is_from_dynobj());

  // The symbol must not have protected visibility.
  if (sym->is_protected())
    {
      gold_error(_("%s: cannot make copy relocation for "
		   "protected symbol '%s', defined in %s"),
		 object->name().c_str(),
		 sym->name(),
		 sym->object()->name().c_str());
    }

  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.
  bool is_ordinary;
  unsigned int shndx = sym->shndx(&is_ordinary);
  gold_assert(is_ordinary);
  typename elfcpp::Elf_types<size>::Elf_WXword addralign;
  bool is_readonly = false;

  {
    // Lock the object so we can read from it.  This is only called
    // single-threaded from scan_relocs, so it is OK to lock.
    // Unfortunately we have no way to pass in a Task token.
    const Task* dummy_task = reinterpret_cast<const Task*>(-1);
    Object* obj = sym->object();
    Task_lock_obj<Object> tl(dummy_task, obj);
    addralign = obj->section_addralign(shndx);
    if (parameters->options().relro())
      {
	if ((obj->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
	  is_readonly = true;
	else
	  {
	    // Symbols in .data.rel.ro should also be treated as read-only.
	    if (obj->section_name(shndx) == ".data.rel.ro")
	      is_readonly = true;
	  }
      }
  }

  typename Sized_symbol<size>::Value_type value = sym->value();
  while ((value & (addralign - 1)) != 0)
    addralign >>= 1;

  // Mark the dynamic object as needed for the --as-needed option.
  sym->object()->set_is_needed();

  Output_data_space* dynbss;

  if (is_readonly)
    {
      if (this->dynrelro_ == NULL)
	{
	  this->dynrelro_ = new Output_data_space(addralign, "** dynrelro");
	  layout->add_output_section_data(".data.rel.ro",
					  elfcpp::SHT_PROGBITS,
					  elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
					  this->dynrelro_, ORDER_RELRO, false);
	}
      dynbss = this->dynrelro_;
    }
  else
    {
      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_, ORDER_BSS, false);
	}
      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);

  this->emit_copy_reloc(symtab, sym, dynbss, offset, reloc_section);
}

// 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_file<size, big_endian>* object,
    unsigned int shndx,
    Output_section* output_section,
    unsigned int r_type,
    typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
    typename elfcpp::Elf_types<size>::Elf_Swxword r_addend)
{
  this->entries_.push_back(Copy_reloc_entry(sym, r_type, object, shndx,
					    output_section, r_offset,
					    r_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)
    {
      Copy_reloc_entry& entry = *p;

      // 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 (entry.sym_->is_from_dynobj())
        reloc_section->add_global_generic(entry.sym_, entry.reloc_type_,
                                          entry.output_section_, entry.relobj_,
                                          entry.shndx_, entry.address_,
                                          entry.addend_);
    }

  // 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.
Commit	Line	Data
12c0daef ILT	1	// copy-relocs.cc -- handle COPY relocations for gold.
12c0daef ILT	2
2571583a	3	// Copyright (C) 2006-2017 Free Software Foundation, Inc.
12c0daef ILT	4	// Written by Ian Lance Taylor <iant@google.com>.
	5
	6	// This file is part of gold.
	7
	8	// This program is free software; you can redistribute it and/or modify
	9	// it under the terms of the GNU General Public License as published by
	10	// the Free Software Foundation; either version 3 of the License, or
	11	// (at your option) any later version.
	12
	13	// This program is distributed in the hope that it will be useful,
	14	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	16	// GNU General Public License for more details.
	17
	18	// You should have received a copy of the GNU General Public License
	19	// along with this program; if not, write to the Free Software
	20	// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
	21	// MA 02110-1301, USA.
	22
	23	#include "gold.h"
	24
	25	#include "symtab.h"
	26	#include "copy-relocs.h"
	27
	28	namespace gold
	29	{
	30
12c0daef ILT	31	// Copy_relocs methods.
	32
	33	// Handle a relocation against a symbol which may force us to generate
	34	// a COPY reloc.
	35
	36	template<int sh_type, int size, bool big_endian>
	37	void
	38	Copy_relocs<sh_type, size, big_endian>::copy_reloc(
	39	Symbol_table* symtab,
	40	Layout* layout,
	41	Sized_symbol<size>* sym,
6fa2a40b	42	Sized_relobj_file<size, big_endian>* object,
12c0daef	43	unsigned int shndx,
ca09d69a	44	Output_section* output_section,
859d7987 CC	45	unsigned int r_type,
	46	typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
	47	typename elfcpp::Elf_types<size>::Elf_Swxword r_addend,
12c0daef ILT	48	Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
	49	{
	50	if (this->need_copy_reloc(sym, object, shndx))
6eeb0170	51	this->make_copy_reloc(symtab, layout, sym, object, reloc_section);
12c0daef ILT	52	else
	53	{
	54	// We may not need a COPY relocation. Save this relocation to
	55	// possibly be emitted later.
859d7987 CC	56	this->save(sym, object, shndx, output_section,
859d7987 CC	57	r_type, r_offset, r_addend);
12c0daef ILT	58	}
	59	}
	60
	61	// Return whether we need a COPY reloc for a relocation against SYM.
	62	// The relocation is begin applied to section SHNDX in OBJECT.
	63
	64	template<int sh_type, int size, bool big_endian>
	65	bool
	66	Copy_relocs<sh_type, size, big_endian>::need_copy_reloc(
	67	Sized_symbol<size>* sym,
6fa2a40b	68	Sized_relobj_file<size, big_endian>* object,
12c0daef ILT	69	unsigned int shndx) const
12c0daef ILT	70	{
966d4097 DK	71	if (!parameters->options().copyreloc())
966d4097 DK	72	return false;
12c0daef ILT	73
	74	if (sym->symsize() == 0)
	75	return false;
	76
	77	// If this is a readonly section, then we need a COPY reloc.
	78	// Otherwise we can use a dynamic reloc. Note that calling
	79	// section_flags here can be slow, as the information is not cached;
	80	// fortunately we shouldn't see too many potential COPY relocs.
	81	if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
	82	return true;
	83
	84	return false;
	85	}
	86
	87	// Emit a COPY relocation for SYM.
	88
	89	template<int sh_type, int size, bool big_endian>
	90	void
	91	Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc(
26d3c67d CC	92	Symbol_table* symtab,
	93	Sized_symbol<size>* sym,
	94	Output_data* posd,
	95	off_t offset,
	96	Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
	97	{
	98	// Define the symbol as being copied.
	99	symtab->define_with_copy_reloc(sym, posd, offset);
	100
	101	// Add the COPY relocation to the dynamic reloc section.
83896202 ILT	102	reloc_section->add_global_generic(sym, this->copy_reloc_type_, posd,
83896202 ILT	103	offset, 0);
26d3c67d CC	104	}
	105
	106	// Make a COPY relocation for SYM and emit it.
	107
	108	template<int sh_type, int size, bool big_endian>
	109	void
	110	Copy_relocs<sh_type, size, big_endian>::make_copy_reloc(
12c0daef ILT	111	Symbol_table* symtab,
	112	Layout* layout,
	113	Sized_symbol<size>* sym,
6eeb0170	114	Sized_relobj_file<size, big_endian>* object,
12c0daef ILT	115	Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
12c0daef ILT	116	{
966d4097 DK	117	// We should not be here if -z nocopyreloc is given.
	118	gold_assert(parameters->options().copyreloc());
	119
6eeb0170 CC	120	gold_assert(sym->is_from_dynobj());
	121
	122	// The symbol must not have protected visibility.
	123	if (sym->is_protected())
	124	{
	125	gold_error(_("%s: cannot make copy relocation for "
	126	"protected symbol '%s', defined in %s"),
	127	object->name().c_str(),
	128	sym->name(),
	129	sym->object()->name().c_str());
	130	}
	131
12c0daef ILT	132	typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize();
	133
	134	// There is no defined way to determine the required alignment of
	135	// the symbol. We know that the symbol is defined in a dynamic
	136	// object. We start with the alignment of the section in which it
	137	// is defined; presumably we do not require an alignment larger than
	138	// that. Then we reduce that alignment if the symbol is not aligned
	139	// within the section.
d491d34e ILT	140	bool is_ordinary;
	141	unsigned int shndx = sym->shndx(&is_ordinary);
	142	gold_assert(is_ordinary);
5f9bcf58	143	typename elfcpp::Elf_types<size>::Elf_WXword addralign;
b733bcb7	144	bool is_readonly = false;
5f9bcf58 CC	145
	146	{
	147	// Lock the object so we can read from it. This is only called
	148	// single-threaded from scan_relocs, so it is OK to lock.
	149	// Unfortunately we have no way to pass in a Task token.
	150	const Task* dummy_task = reinterpret_cast<const Task*>(-1);
	151	Object* obj = sym->object();
	152	Task_lock_obj<Object> tl(dummy_task, obj);
	153	addralign = obj->section_addralign(shndx);
b733bcb7 CC	154	if (parameters->options().relro())
	155	{
	156	if ((obj->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
	157	is_readonly = true;
	158	else
	159	{
	160	// Symbols in .data.rel.ro should also be treated as read-only.
	161	if (obj->section_name(shndx) == ".data.rel.ro")
	162	is_readonly = true;
	163	}
	164	}
5f9bcf58	165	}
12c0daef ILT	166
	167	typename Sized_symbol<size>::Value_type value = sym->value();
	168	while ((value & (addralign - 1)) != 0)
	169	addralign >>= 1;
	170
659948a4 ILT	171	// Mark the dynamic object as needed for the --as-needed option.
	172	sym->object()->set_is_needed();
	173
b733bcb7 CC	174	Output_data_space* dynbss;
	175
	176	if (is_readonly)
12c0daef	177	{
b733bcb7 CC	178	if (this->dynrelro_ == NULL)
	179	{
	180	this->dynrelro_ = new Output_data_space(addralign, "** dynrelro");
	181	layout->add_output_section_data(".data.rel.ro",
	182	elfcpp::SHT_PROGBITS,
	183	elfcpp::SHF_ALLOC \| elfcpp::SHF_WRITE,
	184	this->dynrelro_, ORDER_RELRO, false);
	185	}
	186	dynbss = this->dynrelro_;
	187	}
	188	else
	189	{
	190	if (this->dynbss_ == NULL)
	191	{
	192	this->dynbss_ = new Output_data_space(addralign, "** dynbss");
	193	layout->add_output_section_data(".bss",
	194	elfcpp::SHT_NOBITS,
	195	elfcpp::SHF_ALLOC \| elfcpp::SHF_WRITE,
	196	this->dynbss_, ORDER_BSS, false);
	197	}
	198	dynbss = this->dynbss_;
12c0daef	199	}
12c0daef ILT	200
	201	if (addralign > dynbss->addralign())
	202	dynbss->set_space_alignment(addralign);
	203
	204	section_size_type dynbss_size =
	205	convert_to_section_size_type(dynbss->current_data_size());
	206	dynbss_size = align_address(dynbss_size, addralign);
	207	section_size_type offset = dynbss_size;
	208	dynbss->set_current_data_size(dynbss_size + symsize);
	209
26d3c67d	210	this->emit_copy_reloc(symtab, sym, dynbss, offset, reloc_section);
12c0daef ILT	211	}
	212
	213	// Save a relocation to possibly be emitted later.
	214
	215	template<int sh_type, int size, bool big_endian>
	216	void
ef9beddf ILT	217	Copy_relocs<sh_type, size, big_endian>::save(
ef9beddf ILT	218	Symbol* sym,
6fa2a40b	219	Sized_relobj_file<size, big_endian>* object,
ef9beddf ILT	220	unsigned int shndx,
ef9beddf ILT	221	Output_section* output_section,
859d7987 CC	222	unsigned int r_type,
	223	typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
	224	typename elfcpp::Elf_types<size>::Elf_Swxword r_addend)
12c0daef	225	{
859d7987 CC	226	this->entries_.push_back(Copy_reloc_entry(sym, r_type, object, shndx,
	227	output_section, r_offset,
	228	r_addend));
12c0daef ILT	229	}
	230
	231	// Emit any saved relocs.
	232
	233	template<int sh_type, int size, bool big_endian>
	234	void
	235	Copy_relocs<sh_type, size, big_endian>::emit(
	236	Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
	237	{
	238	for (typename Copy_reloc_entries::iterator p = this->entries_.begin();
	239	p != this->entries_.end();
	240	++p)
91f43acd CC	241	{
	242	Copy_reloc_entry& entry = *p;
	243
	244	// If the symbol is no longer defined in a dynamic object, then we
	245	// emitted a COPY relocation, and we do not want to emit this
	246	// dynamic relocation.
	247	if (entry.sym_->is_from_dynobj())
	248	reloc_section->add_global_generic(entry.sym_, entry.reloc_type_,
	249	entry.output_section_, entry.relobj_,
	250	entry.shndx_, entry.address_,
	251	entry.addend_);
	252	}
12c0daef ILT	253
	254	// We no longer need the saved information.
	255	this->entries_.clear();
	256	}
	257
	258	// Instantiate the templates we need.
	259
	260	#ifdef HAVE_TARGET_32_LITTLE
	261	template
	262	class Copy_relocs<elfcpp::SHT_REL, 32, false>;
	263
	264	template
	265	class Copy_relocs<elfcpp::SHT_RELA, 32, false>;
	266	#endif
	267
	268	#ifdef HAVE_TARGET_32_BIG
	269	template
	270	class Copy_relocs<elfcpp::SHT_REL, 32, true>;
	271
	272	template
	273	class Copy_relocs<elfcpp::SHT_RELA, 32, true>;
	274	#endif
	275
	276	#ifdef HAVE_TARGET_64_LITTLE
	277	template
	278	class Copy_relocs<elfcpp::SHT_REL, 64, false>;
	279
	280	template
	281	class Copy_relocs<elfcpp::SHT_RELA, 64, false>;
	282	#endif
	283
	284	#ifdef HAVE_TARGET_64_BIG
	285	template
	286	class Copy_relocs<elfcpp::SHT_REL, 64, true>;
	287
	288	template
	289	class Copy_relocs<elfcpp::SHT_RELA, 64, true>;
	290	#endif
	291
	292	} // End namespace gold.