xref: /frameworks/compile/mclinker/lib/Target/X86/X86Relocator.cpp

//===- X86Relocator.cpp -------------------------------------------===//
//
//                     The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "X86Relocator.h"
#include "X86RelocationFunctions.h"

#include <mcld/Support/MsgHandling.h>
#include <mcld/LD/LDSymbol.h>

#include <llvm/ADT/Twine.h>
#include <llvm/Support/DataTypes.h>
#include <llvm/Support/ELF.h>

using namespace mcld;

//===--------------------------------------------------------------------===//
// Relocation Functions and Tables
//===--------------------------------------------------------------------===//
DECL_X86_32_APPLY_RELOC_FUNCS

/// the prototype of applying function
typedef Relocator::Result (*X86_32ApplyFunctionType)(Relocation& pReloc,
						     X86_32Relocator& pParent);

// the table entry of applying functions
struct X86_32ApplyFunctionTriple
{
  X86_32ApplyFunctionType func;
  unsigned int type;
  const char* name;
  unsigned int size;
};

// declare the table of applying functions
static const X86_32ApplyFunctionTriple X86_32ApplyFunctions[] = {
  DECL_X86_32_APPLY_RELOC_FUNC_PTRS
};

//===--------------------------------------------------------------------===//
// X86Relocator
//===--------------------------------------------------------------------===//
X86Relocator::X86Relocator()
  : Relocator() {
}

X86Relocator::~X86Relocator()
{
}

//===--------------------------------------------------------------------===//
// X86_32Relocator
//===--------------------------------------------------------------------===//
X86_32Relocator::X86_32Relocator(X86_32GNULDBackend& pParent)
  : X86Relocator(), m_Target(pParent) {
}

Relocator::Result
X86_32Relocator::applyRelocation(Relocation& pRelocation)
{
  Relocation::Type type = pRelocation.type();

  if (type >= sizeof (X86_32ApplyFunctions) / sizeof (X86_32ApplyFunctions[0]) ) {
    return Unknown;
  }

  // apply the relocation
  return X86_32ApplyFunctions[type].func(pRelocation, *this);
}

const char* X86_32Relocator::getName(Relocation::Type pType) const
{
  return X86_32ApplyFunctions[pType].name;
}

Relocator::Size X86_32Relocator::getSize(Relocation::Type pType) const
{
  return X86_32ApplyFunctions[pType].size;;
}

//===--------------------------------------------------------------------===//
// Relocation helper function
//===--------------------------------------------------------------------===//

/// helper_DynRel - Get an relocation entry in .rel.dyn
static
Relocation& helper_DynRel(ResolveInfo* pSym,
                          Fragment& pFrag,
                          uint64_t pOffset,
                          X86Relocator::Type pType,
                          X86_32Relocator& pParent)
{
  X86_32GNULDBackend& ld_backend = pParent.getTarget();
  Relocation& rel_entry = *ld_backend.getRelDyn().consumeEntry();
  rel_entry.setType(pType);
  rel_entry.targetRef().assign(pFrag, pOffset);
  if (pType == llvm::ELF::R_386_RELATIVE || NULL == pSym)
    rel_entry.setSymInfo(0);
  else
    rel_entry.setSymInfo(pSym);

  return rel_entry;
}


/// helper_use_relative_reloc - Check if symbol can use relocation
/// R_386_RELATIVE
static bool
helper_use_relative_reloc(const ResolveInfo& pSym,
                          const X86_32Relocator& pFactory)

{
  // if symbol is dynamic or undefine or preemptible
  if (pSym.isDyn() ||
      pSym.isUndef() ||
      pFactory.getTarget().isSymbolPreemptible(pSym))
    return false;
  return true;
}

static
X86_32GOTEntry& helper_get_GOT_and_init(Relocation& pReloc,
					X86_32Relocator& pParent)
{
  // rsym - The relocation target symbol
  ResolveInfo* rsym = pReloc.symInfo();
  X86_32GNULDBackend& ld_backend = pParent.getTarget();

  X86_32GOTEntry* got_entry = pParent.getSymGOTMap().lookUp(*rsym);
  if (NULL != got_entry)
    return *got_entry;

  // not found
  got_entry = ld_backend.getGOT().consume();
  pParent.getSymGOTMap().record(*rsym, *got_entry);

  // If we first get this GOT entry, we should initialize it.
  if (rsym->reserved() & X86GNULDBackend::ReserveGOT) {
    // No corresponding dynamic relocation, initialize to the symbol value.
    got_entry->setValue(pReloc.symValue());
  }
  else if (rsym->reserved() & X86GNULDBackend::GOTRel) {
    // Initialize got_entry content and the corresponding dynamic relocation.
    if (helper_use_relative_reloc(*rsym, pParent)) {
      helper_DynRel(rsym, *got_entry, 0x0, llvm::ELF::R_386_RELATIVE, pParent);
      got_entry->setValue(pReloc.symValue());
    }
    else {
      helper_DynRel(rsym, *got_entry, 0x0, llvm::ELF::R_386_GLOB_DAT, pParent);
      got_entry->setValue(0);
    }
  }
  else {
    fatal(diag::reserve_entry_number_mismatch_got);
  }
  return *got_entry;
}


static
X86Relocator::Address helper_GOT_ORG(X86_32Relocator& pParent)
{
  return pParent.getTarget().getGOTPLT().addr();
}


static
X86Relocator::Address helper_GOT(Relocation& pReloc, X86_32Relocator& pParent)
{
  X86_32GOTEntry& got_entry = helper_get_GOT_and_init(pReloc, pParent);
  X86Relocator::Address got_addr = pParent.getTarget().getGOT().addr();
  return got_addr + got_entry.getOffset();
}


static
PLTEntryBase& helper_get_PLT_and_init(Relocation& pReloc,
				      X86_32Relocator& pParent)
{
  // rsym - The relocation target symbol
  ResolveInfo* rsym = pReloc.symInfo();
  X86_32GNULDBackend& ld_backend = pParent.getTarget();

  PLTEntryBase* plt_entry = pParent.getSymPLTMap().lookUp(*rsym);
  if (NULL != plt_entry)
    return *plt_entry;

  // not found
  plt_entry = ld_backend.getPLT().consume();
  pParent.getSymPLTMap().record(*rsym, *plt_entry);
  // If we first get this PLT entry, we should initialize it.
  if (rsym->reserved() & X86GNULDBackend::ReservePLT) {
    X86_32GOTEntry* gotplt_entry = pParent.getSymGOTPLTMap().lookUp(*rsym);
    assert(NULL == gotplt_entry && "PLT entry not exist, but DynRel entry exist!");
    gotplt_entry = ld_backend.getGOTPLT().consume();
    pParent.getSymGOTPLTMap().record(*rsym, *gotplt_entry);
    // init the corresponding rel entry in .rel.plt
    Relocation& rel_entry = *ld_backend.getRelPLT().consumeEntry();
    rel_entry.setType(llvm::ELF::R_386_JUMP_SLOT);
    rel_entry.targetRef().assign(*gotplt_entry);
    rel_entry.setSymInfo(rsym);
  }
  else {
    fatal(diag::reserve_entry_number_mismatch_plt);
  }

  return *plt_entry;
}


static
X86Relocator::Address helper_PLT_ORG(X86_32Relocator& pParent)
{
  return pParent.getTarget().getPLT().addr();
}


static
X86Relocator::Address helper_PLT(Relocation& pReloc, X86_32Relocator& pParent)
{
  PLTEntryBase& plt_entry = helper_get_PLT_and_init(pReloc, pParent);
  return helper_PLT_ORG(pParent) + plt_entry.getOffset();
}


//=========================================//
// Each relocation function implementation //
//=========================================//

// R_386_NONE
X86Relocator::Result none(Relocation& pReloc, X86_32Relocator& pParent)
{
  return X86Relocator::OK;
}

// R_386_32: S + A
// R_386_16
// R_386_8
X86Relocator::Result abs(Relocation& pReloc, X86_32Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  Relocator::DWord S = pReloc.symValue();
  bool has_dyn_rel = pParent.getTarget().symbolNeedsDynRel(
                              *rsym,
                              (rsym->reserved() & X86GNULDBackend::ReservePLT),
                              true);

  LDSection& target_sect = pReloc.targetRef().frag()->getParent()->getSection();
  // If the flag of target section is not ALLOC, we will not scan this relocation
  // but perform static relocation. (e.g., applying .debug section)
  if (0x0 == (llvm::ELF::SHF_ALLOC & target_sect.flag())) {
    pReloc.target() = S + A;
    return X86Relocator::OK;
  }

  // A local symbol may need REL Type dynamic relocation
  if (rsym->isLocal() && has_dyn_rel) {
    if (llvm::ELF::R_386_32 == pReloc.type()) {
      helper_DynRel(rsym, *pReloc.targetRef().frag(),
                    pReloc.targetRef().offset(), llvm::ELF::R_386_RELATIVE,
                    pParent);
    }
    else {
      // FIXME: check Section symbol
      helper_DynRel(rsym, *pReloc.targetRef().frag(),
                    pReloc.targetRef().offset(), pReloc.type(), pParent);
    }
    pReloc.target() = S + A;
    return X86Relocator::OK;
  }

  // An external symbol may need PLT and dynamic relocation
  if (!rsym->isLocal()) {
    if (rsym->reserved() & X86GNULDBackend::ReservePLT) {
      S = helper_PLT(pReloc, pParent);
    }
    // If we generate a dynamic relocation (except R_386_RELATIVE)
    // for a place, we should not perform static relocation on it
    // in order to keep the addend store in the place correct.
    if (has_dyn_rel) {
      if (llvm::ELF::R_386_32 == pReloc.type() &&
          helper_use_relative_reloc(*rsym, pParent)) {
        helper_DynRel(rsym, *pReloc.targetRef().frag(),
              pReloc.targetRef().offset(), llvm::ELF::R_386_RELATIVE, pParent);
      }
      else {
        helper_DynRel(rsym, *pReloc.targetRef().frag(),
                          pReloc.targetRef().offset(), pReloc.type(), pParent);
        return X86Relocator::OK;
      }
    }
  }

  // perform static relocation
  pReloc.target() = S + A;
  return X86Relocator::OK;
}

// R_386_PC32: S + A - P
// R_386_PC16
// R_386_PC8
X86Relocator::Result rel(Relocation& pReloc, X86_32Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  Relocator::DWord S = pReloc.symValue();
  Relocator::DWord P = pReloc.place();

  LDSection& target_sect = pReloc.targetRef().frag()->getParent()->getSection();
  // If the flag of target section is not ALLOC, we will not scan this relocation
  // but perform static relocation. (e.g., applying .debug section)
  if (0x0 == (llvm::ELF::SHF_ALLOC & target_sect.flag())) {
    pReloc.target() = S + A - P;
    return X86Relocator::OK;
  }

  // An external symbol may need PLT and dynamic relocation
  if (!rsym->isLocal()) {
    if (rsym->reserved() & X86GNULDBackend::ReservePLT) {
       S = helper_PLT(pReloc, pParent);
       pReloc.target() = S + A - P;
    }
    if (pParent.getTarget().symbolNeedsDynRel(
                              *rsym,
                              (rsym->reserved() & X86GNULDBackend::ReservePLT),
                              false)) {
      if (helper_use_relative_reloc(*rsym, pParent) ) {
        helper_DynRel(rsym, *pReloc.targetRef().frag(),
              pReloc.targetRef().offset(), llvm::ELF::R_386_RELATIVE, pParent);
      }
      else {
        helper_DynRel(rsym, *pReloc.targetRef().frag(),
                          pReloc.targetRef().offset(), pReloc.type(), pParent);
          return X86Relocator::OK;
      }
    }
  }

   // perform static relocation
  pReloc.target() = S + A - P;
  return X86Relocator::OK;
}

// R_386_GOTOFF: S + A - GOT_ORG
X86Relocator::Result gotoff32(Relocation& pReloc, X86_32Relocator& pParent)
{
  Relocator::DWord      A = pReloc.target() + pReloc.addend();
  X86Relocator::Address GOT_ORG = helper_GOT_ORG(pParent);
  X86Relocator::Address S = pReloc.symValue();

  pReloc.target() = S + A - GOT_ORG;
  return X86Relocator::OK;
}

// R_386_GOTPC: GOT_ORG + A - P
X86Relocator::Result gotpc32(Relocation& pReloc, X86_32Relocator& pParent)
{
  Relocator::DWord      A       = pReloc.target() + pReloc.addend();
  X86Relocator::Address GOT_ORG = helper_GOT_ORG(pParent);
  // Apply relocation.
  pReloc.target() = GOT_ORG + A - pReloc.place();
  return X86Relocator::OK;
}

// R_386_GOT32: GOT(S) + A - GOT_ORG
X86Relocator::Result got32(Relocation& pReloc, X86_32Relocator& pParent)
{
  if (!(pReloc.symInfo()->reserved()
       & (X86GNULDBackend::ReserveGOT |X86GNULDBackend::GOTRel))) {
    return X86Relocator::BadReloc;
  }
  X86Relocator::Address GOT_S   = helper_GOT(pReloc, pParent);
  Relocator::DWord      A       = pReloc.target() + pReloc.addend();
  X86Relocator::Address GOT_ORG = helper_GOT_ORG(pParent);
  // Apply relocation.
  pReloc.target() = GOT_S + A - GOT_ORG;
  return X86Relocator::OK;
}

// R_386_PLT32: PLT(S) + A - P
X86Relocator::Result plt32(Relocation& pReloc, X86_32Relocator& pParent)
{
  // PLT_S depends on if there is a PLT entry.
  X86Relocator::Address PLT_S;
  if ((pReloc.symInfo()->reserved() & X86GNULDBackend::ReservePLT))
    PLT_S = helper_PLT(pReloc, pParent);
  else
    PLT_S = pReloc.symValue();
  Relocator::DWord      A = pReloc.target() + pReloc.addend();
  X86Relocator::Address P = pReloc.place();
  pReloc.target() = PLT_S + A - P;
  return X86Relocator::OK;
}

// R_386_TLS_GD:
X86Relocator::Result tls_gd(Relocation& pReloc, X86_32Relocator& pParent)
{
  // global-dynamic
  ResolveInfo* rsym = pReloc.symInfo();
  // must reserve two pairs of got and dynamic relocation
  if (!(rsym->reserved() & X86GNULDBackend::GOTRel)) {
     return X86Relocator::BadReloc;
  }

  X86_32GNULDBackend& ld_backend = pParent.getTarget();
  ELFFileFormat* file_format = pParent.getTarget().getOutputFormat();
  // setup corresponding got and dynamic relocatio entries:
  // get first got entry, if there is already a got entry for rsym, then apply
  // this relocation to the got entry directly. If not, setup the corresponding
  // got and dyn relocation entries
  X86_32GOTEntry* got_entry1 = pParent.getSymGOTMap().lookUp(*rsym);

  if (NULL == got_entry1) {
    // get and init two got entries if not exist
    got_entry1 = ld_backend.getGOT().consume();
    pParent.getSymGOTMap().record(*rsym, *got_entry1);
    X86_32GOTEntry* got_entry2 = ld_backend.getGOT().consume();
    got_entry1->setValue(0x0);
    got_entry2->setValue(0x0);
    // setup dyn rel for get_entry1
    Relocation& rel_entry1 = helper_DynRel(rsym, *got_entry1, 0x0,
                                        llvm::ELF::R_386_TLS_DTPMOD32, pParent);
    if (rsym->isLocal()) {
      // for local symbol, set got_entry2 to symbol value
      got_entry2->setValue(pReloc.symValue());

      // for local tls symbol, add rel entry against the section symbol this
      // symbol belong to (.tdata or .tbss)
      const LDSection* sym_sect =
         &rsym->outSymbol()->fragRef()->frag()->getParent()->getSection();
      ResolveInfo* sect_sym = NULL;
      if (&file_format->getTData() == sym_sect)
        sect_sym = pParent.getTarget().getTDATASymbol().resolveInfo();
      else
        sect_sym = pParent.getTarget().getTBSSSymbol().resolveInfo();
      rel_entry1.setSymInfo(sect_sym);
    }
    else {
      // for non-local symbol, add a pair of rel entries against this symbol
      // for those two got entries
      helper_DynRel(rsym, *got_entry2, 0x0,
                                        llvm::ELF::R_386_TLS_DTPOFF32, pParent);
    }
  }

  // perform relocation to the first got entry
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  // GOT_OFF - the offset between the got_entry1 and _GLOBAL_OFFSET_TABLE (the
  // .got.plt section)
  X86Relocator::Address GOT_OFF =
     file_format->getGOT().addr() +
     got_entry1->getOffset() -
     file_format->getGOTPLT().addr();
  pReloc.target() = GOT_OFF + A;
  return X86Relocator::OK;
}

// R_386_TLS_LDM
X86Relocator::Result tls_ldm(Relocation& pReloc, X86_32Relocator& pParent)
{
  // FIXME: no linker optimization for TLS relocation
  const X86_32GOTEntry& got_entry = pParent.getTarget().getTLSModuleID();

  // All GOT offsets are relative to the end of the GOT.
  X86Relocator::SWord GOT_S = got_entry.getOffset() -
                                      (pParent.getTarget().getGOTPLT().addr() -
                                       pParent.getTarget().getGOT().addr());
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  pReloc.target() = GOT_S + A;

  return X86Relocator::OK;
}

// R_386_TLS_LDO_32
X86Relocator::Result tls_ldo_32(Relocation& pReloc, X86_32Relocator& pParent)
{
  // FIXME: no linker optimization for TLS relocation
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  X86Relocator::Address S = pReloc.symValue();
  pReloc.target() = S + A;
  return X86Relocator::OK;
}

// R_X86_TLS_IE
X86Relocator::Result tls_ie(Relocation& pReloc, X86_32Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  if (!(rsym->reserved() & X86GNULDBackend::GOTRel)) {
     return X86Relocator::BadReloc;
  }

  if (rsym->reserved() & X86GNULDBackend::ReserveRel) {
    // when building shared object, set up a RELATIVE dynamic relocation
    helper_DynRel(rsym, *pReloc.targetRef().frag(), pReloc.targetRef().offset(),
                                            llvm::ELF::R_386_RELATIVE, pParent);
  }

  // set up the got and dynamic relocation entries if not exist
  X86_32GOTEntry* got_entry = pParent.getSymGOTMap().lookUp(*rsym);
  if (NULL == got_entry) {
    // set got entry
    X86_32GNULDBackend& ld_backend = pParent.getTarget();
    got_entry = ld_backend.getGOT().consume();
    pParent.getSymGOTMap().record(*rsym, *got_entry);
    got_entry->setValue(0x0);
    // set relocation entry
    Relocation& rel_entry = *ld_backend.getRelDyn().consumeEntry();
    rel_entry.setType(llvm::ELF::R_386_TLS_TPOFF);
    rel_entry.setSymInfo(rsym);
    rel_entry.targetRef().assign(*got_entry);
  }

  // perform relocation to the absolute address of got_entry
  X86Relocator::Address GOT_S =
                 pParent.getTarget().getGOT().addr() + got_entry->getOffset();

  Relocator::DWord A = pReloc.target() + pReloc.addend();
  pReloc.target() = GOT_S + A;

  return X86Relocator::OK;
}

// R_386_TLS_GOTIE
X86Relocator::Result tls_gotie(Relocation& pReloc, X86_32Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  if (!(rsym->reserved() & X86GNULDBackend::GOTRel)) {
     return X86Relocator::BadReloc;
  }

  // set up the got and dynamic relocation entries if not exist
  X86_32GOTEntry* got_entry = pParent.getSymGOTMap().lookUp(*rsym);
  if (NULL == got_entry) {
    // set got entry
    X86_32GNULDBackend& ld_backend = pParent.getTarget();
    got_entry = ld_backend.getGOT().consume();
    pParent.getSymGOTMap().record(*rsym, *got_entry);
    got_entry->setValue(0x0);
    // set relocation entry
    Relocation& rel_entry = *ld_backend.getRelDyn().consumeEntry();
    rel_entry.setType(llvm::ELF::R_386_TLS_TPOFF);
    rel_entry.setSymInfo(rsym);
    rel_entry.targetRef().assign(*got_entry);
  }

  // All GOT offsets are relative to the end of the GOT.
  X86Relocator::SWord GOT_S = got_entry->getOffset() -
    (pParent.getTarget().getGOTPLT().addr() - pParent.getTarget().getGOT().addr());
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  pReloc.target() = GOT_S + A;

  return X86Relocator::OK;
}

// R_X86_TLS_LE
X86Relocator::Result tls_le(Relocation& pReloc, X86_32Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  if (pReloc.symInfo()->reserved() & X86GNULDBackend::ReserveRel) {
    helper_DynRel(rsym,
                  *pReloc.targetRef().frag(),
                  pReloc.targetRef().offset(),
                  llvm::ELF::R_386_TLS_TPOFF,
                  pParent);
    return X86Relocator::OK;
  }

  // perform static relocation
  // get TLS segment
  ELFSegment* tls_seg = pParent.getTarget().elfSegmentTable().find(
                                       llvm::ELF::PT_TLS, llvm::ELF::PF_R, 0x0);
  Relocator::DWord A = pReloc.target() + pReloc.addend();
  X86Relocator::Address S = pReloc.symValue();
  pReloc.target() = S + A - tls_seg->memsz();
  return X86Relocator::OK;
}

X86Relocator::Result unsupport(Relocation& pReloc, X86_32Relocator& pParent)
{
  return X86Relocator::Unsupport;
}

//===--------------------------------------------------------------------===//
// Relocation Functions and Tables
//===--------------------------------------------------------------------===//
DECL_X86_64_APPLY_RELOC_FUNCS

/// the prototype of applying function
typedef Relocator::Result (*X86_64ApplyFunctionType)(Relocation& pReloc,
						     X86_64Relocator& pParent);

// the table entry of applying functions
struct X86_64ApplyFunctionTriple
{
  X86_64ApplyFunctionType func;
  unsigned int type;
  const char* name;
  unsigned int size;
};

// declare the table of applying functions
static const X86_64ApplyFunctionTriple X86_64ApplyFunctions[] = {
  DECL_X86_64_APPLY_RELOC_FUNC_PTRS
};

//===--------------------------------------------------------------------===//
// X86_64Relocator
//===--------------------------------------------------------------------===//
X86_64Relocator::X86_64Relocator(X86_64GNULDBackend& pParent)
  : X86Relocator(), m_Target(pParent) {
}

Relocator::Result
X86_64Relocator::applyRelocation(Relocation& pRelocation)
{
  Relocation::Type type = pRelocation.type();

  if (type >= sizeof (X86_64ApplyFunctions) / sizeof (X86_64ApplyFunctions[0]) ) {
    return Unknown;
  }

  // apply the relocation
  return X86_64ApplyFunctions[type].func(pRelocation, *this);
}

const char* X86_64Relocator::getName(Relocation::Type pType) const
{
  return X86_64ApplyFunctions[pType].name;
}

Relocator::Size X86_64Relocator::getSize(Relocation::Type pType) const
{
  return X86_64ApplyFunctions[pType].size;
}

/// helper_DynRel - Get an relocation entry in .rela.dyn
static
Relocation& helper_DynRel(ResolveInfo* pSym,
                          Fragment& pFrag,
                          uint64_t pOffset,
                          X86Relocator::Type pType,
                          X86_64Relocator& pParent)
{
  X86_64GNULDBackend& ld_backend = pParent.getTarget();
  Relocation& rel_entry = *ld_backend.getRelDyn().consumeEntry();
  rel_entry.setType(pType);
  rel_entry.targetRef().assign(pFrag, pOffset);
  if (pType == llvm::ELF::R_X86_64_RELATIVE || NULL == pSym)
    rel_entry.setSymInfo(0);
  else
    rel_entry.setSymInfo(pSym);

  return rel_entry;
}


/// helper_use_relative_reloc - Check if symbol can use relocation
/// R_X86_64_RELATIVE
static bool
helper_use_relative_reloc(const ResolveInfo& pSym,
                          const X86_64Relocator& pFactory)

{
  // if symbol is dynamic or undefine or preemptible
  if (pSym.isDyn() ||
      pSym.isUndef() ||
      pFactory.getTarget().isSymbolPreemptible(pSym))
    return false;
  return true;
}

static
X86_64GOTEntry& helper_get_GOT_and_init(Relocation& pReloc,
					X86_64Relocator& pParent)
{
  // rsym - The relocation target symbol
  ResolveInfo* rsym = pReloc.symInfo();
  X86_64GNULDBackend& ld_backend = pParent.getTarget();

  X86_64GOTEntry* got_entry = pParent.getSymGOTMap().lookUp(*rsym);
  if (NULL != got_entry)
    return *got_entry;

  // not found
  got_entry = ld_backend.getGOT().consume();
  pParent.getSymGOTMap().record(*rsym, *got_entry);

  // If we first get this GOT entry, we should initialize it.
  if (rsym->reserved() & X86GNULDBackend::ReserveGOT) {
    // No corresponding dynamic relocation, initialize to the symbol value.
    got_entry->setValue(pReloc.symValue());
  }
  else if (rsym->reserved() & X86GNULDBackend::GOTRel) {
    // Initialize got_entry content and the corresponding dynamic relocation.
    if (helper_use_relative_reloc(*rsym, pParent)) {
      Relocation& rel_entry = helper_DynRel(rsym, *got_entry, 0x0,
					    llvm::ELF::R_X86_64_RELATIVE,
					    pParent);
      rel_entry.setAddend(pReloc.symValue());
    }
    else {
      helper_DynRel(rsym, *got_entry, 0x0, llvm::ELF::R_X86_64_GLOB_DAT,
		    pParent);
    }
    got_entry->setValue(0);
  }
  else {
    fatal(diag::reserve_entry_number_mismatch_got);
  }
  return *got_entry;
}

static
X86Relocator::Address helper_GOT_ORG(X86_64Relocator& pParent)
{
  return pParent.getTarget().getGOT().addr();
}

static
X86Relocator::Address helper_GOT(Relocation& pReloc, X86_64Relocator& pParent)
{
  X86_64GOTEntry& got_entry = helper_get_GOT_and_init(pReloc, pParent);
  return got_entry.getOffset();
}

static
PLTEntryBase& helper_get_PLT_and_init(Relocation& pReloc,
				      X86_64Relocator& pParent)
{
  // rsym - The relocation target symbol
  ResolveInfo* rsym = pReloc.symInfo();
  X86_64GNULDBackend& ld_backend = pParent.getTarget();

  PLTEntryBase* plt_entry = pParent.getSymPLTMap().lookUp(*rsym);
  if (NULL != plt_entry)
    return *plt_entry;

  // not found
  plt_entry = ld_backend.getPLT().consume();
  pParent.getSymPLTMap().record(*rsym, *plt_entry);
  // If we first get this PLT entry, we should initialize it.
  if (rsym->reserved() & X86GNULDBackend::ReservePLT) {
    X86_64GOTEntry* gotplt_entry = pParent.getSymGOTPLTMap().lookUp(*rsym);
    assert(NULL == gotplt_entry && "PLT entry not exist, but DynRel entry exist!");
    gotplt_entry = ld_backend.getGOTPLT().consume();
    pParent.getSymGOTPLTMap().record(*rsym, *gotplt_entry);
    // init the corresponding rel entry in .rel.plt
    Relocation& rel_entry = *ld_backend.getRelPLT().consumeEntry();
    rel_entry.setType(llvm::ELF::R_X86_64_JUMP_SLOT);
    rel_entry.targetRef().assign(*gotplt_entry);
    rel_entry.setSymInfo(rsym);
  }
  else {
    fatal(diag::reserve_entry_number_mismatch_plt);
  }

  return *plt_entry;
}

static
X86Relocator::Address helper_PLT_ORG(X86_64Relocator& pParent)
{
  return pParent.getTarget().getPLT().addr();
}

static
X86Relocator::Address helper_PLT(Relocation& pReloc, X86_64Relocator& pParent)
{
  PLTEntryBase& plt_entry = helper_get_PLT_and_init(pReloc, pParent);
  return helper_PLT_ORG(pParent) + plt_entry.getOffset();
}

//
// R_X86_64_NONE
X86Relocator::Result none(Relocation& pReloc, X86_64Relocator& pParent)
{
  return X86Relocator::OK;
}

// R_X86_64_64: S + A
// R_X86_64_32:
// R_X86_64_16:
// R_X86_64_8
X86Relocator::Result abs(Relocation& pReloc, X86_64Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  Relocator::DWord A = pReloc.addend();
  Relocator::DWord S = pReloc.symValue();
  bool has_dyn_rel = pParent.getTarget().symbolNeedsDynRel(
                              *rsym,
                              (rsym->reserved() & X86GNULDBackend::ReservePLT),
                              true);

  LDSection& target_sect = pReloc.targetRef().frag()->getParent()->getSection();
  // If the flag of target section is not ALLOC, we will not scan this relocation
  // but perform static relocation. (e.g., applying .debug section)
  if (0x0 == (llvm::ELF::SHF_ALLOC & target_sect.flag())) {
    pReloc.target() = S + A;
    return X86Relocator::OK;
  }

  Relocation::Type pointerRel = pParent.getTarget().getPointerRel();

  // A local symbol may need REL Type dynamic relocation
  if (rsym->isLocal() && has_dyn_rel) {
    if (pointerRel == pReloc.type()) {
      Relocation& rel_entry = helper_DynRel(rsym, *pReloc.targetRef().frag(),
					    pReloc.targetRef().offset(),
					    llvm::ELF::R_X86_64_RELATIVE,
					    pParent);
      rel_entry.setAddend(S + A);
    }
    else {
      // FIXME: check Section symbol
      Relocation& rel_entry = helper_DynRel(rsym, *pReloc.targetRef().frag(),
					    pReloc.targetRef().offset(),
					    pReloc.type(), pParent);
      rel_entry.setAddend(S + A);
    }
    return X86Relocator::OK;
  }

  // An external symbol may need PLT and dynamic relocation
  if (!rsym->isLocal()) {
    // If we generate a dynamic relocation for a place with explicit
    // addend, there is no need to perform static relocation on it.
    if (has_dyn_rel) {
      Relocation& rel_entry = helper_DynRel(rsym, *pReloc.targetRef().frag(),
					    pReloc.targetRef().offset(),
					    llvm::ELF::R_X86_64_RELATIVE,
					    pParent);
      // Copy addend.
      rel_entry.setAddend(A);
      return X86Relocator::OK;
    }
    else if (rsym->reserved() & X86GNULDBackend::ReservePLT) {
      S = helper_PLT(pReloc, pParent);
    }
  }

  // perform static relocation
  pReloc.target() = S + A;
  return X86Relocator::OK;
}

// R_X86_64_32S: S + A
X86Relocator::Result signed32(Relocation& pReloc, X86_64Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  Relocator::DWord A = pReloc.addend();
  Relocator::DWord S = pReloc.symValue();
  bool has_dyn_rel = pParent.getTarget().symbolNeedsDynRel(
                              *rsym,
                              (rsym->reserved() & X86GNULDBackend::ReservePLT),
                              true);

  // There should be no dynamic relocations for R_X86_64_32S.
  if (has_dyn_rel)
    return X86Relocator::BadReloc;

  LDSection& target_sect = pReloc.targetRef().frag()->getParent()->getSection();
  // If the flag of target section is not ALLOC, we will not scan this relocation
  // but perform static relocation. (e.g., applying .debug section)
  // An external symbol may need PLT and dynamic relocation
  if (0x0 != (llvm::ELF::SHF_ALLOC & target_sect.flag()) &&
      !rsym->isLocal() && rsym->reserved() & X86GNULDBackend::ReservePLT)
    S = helper_PLT(pReloc, pParent);

  // Check 32-bit signed overflow.
  Relocator::SWord V = S + A;
  if (V > INT64_C(0x7fffffff) || V < INT64_C(-0x80000000))
    return X86Relocator::Overflow;

  // perform static relocation
  pReloc.target() = S + A;
  return X86Relocator::OK;
}

// R_X86_64_GOTPCREL: GOT(S) + GOT_ORG + A - P
X86Relocator::Result gotpcrel(Relocation& pReloc, X86_64Relocator& pParent)
{
  if (!(pReloc.symInfo()->reserved()
       & (X86GNULDBackend::ReserveGOT |X86GNULDBackend::GOTRel))) {
    return X86Relocator::BadReloc;
  }
  X86Relocator::Address GOT_S   = helper_GOT(pReloc, pParent);
  Relocator::DWord      A       = pReloc.addend();
  X86Relocator::Address GOT_ORG = helper_GOT_ORG(pParent);
  // Apply relocation.
  pReloc.target() = GOT_S + GOT_ORG + A - pReloc.place();
  return X86Relocator::OK;
}

// R_X86_64_PLT32: PLT(S) + A - P
X86Relocator::Result plt32(Relocation& pReloc, X86_64Relocator& pParent)
{
  // PLT_S depends on if there is a PLT entry.
  X86Relocator::Address PLT_S;
  if ((pReloc.symInfo()->reserved() & X86GNULDBackend::ReservePLT))
    PLT_S = helper_PLT(pReloc, pParent);
  else
    PLT_S = pReloc.symValue();
  Relocator::DWord      A = pReloc.addend();
  X86Relocator::Address P = pReloc.place();
  pReloc.target() = PLT_S + A - P;
  return X86Relocator::OK;
}

// R_X86_64_PC32: S + A - P
// R_X86_64_PC16
// R_X86_64_PC8
X86Relocator::Result rel(Relocation& pReloc, X86_64Relocator& pParent)
{
  ResolveInfo* rsym = pReloc.symInfo();
  Relocator::DWord A = pReloc.addend();
  Relocator::DWord S = pReloc.symValue();
  Relocator::DWord P = pReloc.place();

  LDSection& target_sect = pReloc.targetRef().frag()->getParent()->getSection();
  // If the flag of target section is not ALLOC, we will not scan this relocation
  // but perform static relocation. (e.g., applying .debug section)
  if (0x0 == (llvm::ELF::SHF_ALLOC & target_sect.flag())) {
    pReloc.target() = S + A - P;
    return X86Relocator::OK;
  }

  // An external symbol may need PLT and dynamic relocation
  if (!rsym->isLocal()) {
    if (rsym->reserved() & X86GNULDBackend::ReservePLT) {
       S = helper_PLT(pReloc, pParent);
       pReloc.target() = S + A - P;
    }
    if (pParent.getTarget().symbolNeedsDynRel(
                              *rsym,
                              (rsym->reserved() & X86GNULDBackend::ReservePLT),
                              false)) {
          return X86Relocator::Overflow;
    }
  }

   // perform static relocation
  pReloc.target() = S + A - P;
  return X86Relocator::OK;
}

X86Relocator::Result unsupport(Relocation& pReloc, X86_64Relocator& pParent)
{
  return X86Relocator::Unsupport;
}