void ARMGNULDBackend::createARMGOT(MCLinker& pLinker, const Output& pOutput)
{
// get .got LDSection and create MCSectionData
ELFFileFormat* file_format = getOutputFormat(pOutput);
LDSection& got = file_format->getGOT();
m_pGOT = new ARMGOT(got, pLinker.getOrCreateSectData(got));
// define symbol _GLOBAL_OFFSET_TABLE_ when .got create
if( m_pGOTSymbol != NULL ) {
pLinker.defineSymbol<MCLinker::Force, MCLinker::Unresolve>(
"_GLOBAL_OFFSET_TABLE_",
false,
ResolveInfo::Object,
ResolveInfo::Define,
ResolveInfo::Local,
0x0, // size
0x0, // value
pLinker.getLayout().getFragmentRef(*(m_pGOT->begin()), 0x0),
ResolveInfo::Hidden);
}
else {
m_pGOTSymbol = pLinker.defineSymbol<MCLinker::Force, MCLinker::Resolve>(
"_GLOBAL_OFFSET_TABLE_",
false,
ResolveInfo::Object,
ResolveInfo::Define,
ResolveInfo::Local,
0x0, // size
0x0, // value
pLinker.getLayout().getFragmentRef(*(m_pGOT->begin()), 0x0),
ResolveInfo::Hidden);
}
}
bool ARMGNULDBackend::initRelocFactory(const MCLinker& pLinker)
{
if (NULL == m_pRelocFactory) {
m_pRelocFactory = new ARMRelocationFactory(1024, *this);
m_pRelocFactory->setLayout(pLinker.getLayout());
}
return true;
}
/// allocateCommonSymbols - allocate common symbols in the corresponding
/// sections.
/// @refer Google gold linker: common.cc: 214
bool
ARMGNULDBackend::allocateCommonSymbols(const MCLDInfo& pInfo, MCLinker& pLinker) const
{
SymbolCategory& symbol_list = pLinker.getOutputSymbols();
if (symbol_list.emptyCommons() && symbol_list.emptyLocals())
return true;
// addralign := max value of all common symbols
uint64_t addralign = 0x0;
// Due to the visibility, some common symbols may be forcefully local.
SymbolCategory::iterator com_sym, com_end = symbol_list.localEnd();
for (com_sym = symbol_list.localBegin(); com_sym != com_end; ++com_sym) {
if (ResolveInfo::Common == (*com_sym)->desc()) {
if ((*com_sym)->value() > addralign)
addralign = (*com_sym)->value();
}
}
// global common symbols.
com_end = symbol_list.commonEnd();
for (com_sym = symbol_list.commonBegin(); com_sym != com_end; ++com_sym) {
if ((*com_sym)->value() > addralign)
addralign = (*com_sym)->value();
}
// FIXME: If the order of common symbols is defined, then sort common symbols
// com_sym = symbol_list.commonBegin();
// std::sort(com_sym, com_end, some kind of order);
// get or create corresponding BSS LDSection
LDSection* bss_sect_hdr = NULL;
if (ResolveInfo::ThreadLocal == (*com_sym)->type()) {
bss_sect_hdr = &pLinker.getOrCreateOutputSectHdr(
".tbss",
LDFileFormat::BSS,
llvm::ELF::SHT_NOBITS,
llvm::ELF::SHF_WRITE | llvm::ELF::SHF_ALLOC);
}
else {
bss_sect_hdr = &pLinker.getOrCreateOutputSectHdr(".bss",
LDFileFormat::BSS,
llvm::ELF::SHT_NOBITS,
llvm::ELF::SHF_WRITE | llvm::ELF::SHF_ALLOC);
}
// get or create corresponding BSS MCSectionData
assert(NULL != bss_sect_hdr);
llvm::MCSectionData& bss_section = pLinker.getOrCreateSectData(*bss_sect_hdr);
// allocate all common symbols
uint64_t offset = bss_sect_hdr->size();
// allocate all local common symbols
com_end = symbol_list.localEnd();
for (com_sym = symbol_list.localBegin(); com_sym != com_end; ++com_sym) {
if (ResolveInfo::Common == (*com_sym)->desc()) {
// We have to reset the description of the symbol here. When doing
// incremental linking, the output relocatable object may have common
// symbols. Therefore, we can not treat common symbols as normal symbols
// when emitting the regular name pools. We must change the symbols'
// description here.
(*com_sym)->resolveInfo()->setDesc(ResolveInfo::Define);
llvm::MCFragment* frag = new llvm::MCFillFragment(0x0, 1, (*com_sym)->size());
(*com_sym)->setFragmentRef(new MCFragmentRef(*frag, 0));
uint64_t size = pLinker.getLayout().appendFragment(*frag,
bss_section,
(*com_sym)->value());
offset += size;
}
}
// allocate all global common symbols
com_end = symbol_list.commonEnd();
for (com_sym = symbol_list.commonBegin(); com_sym != com_end; ++com_sym) {
// We have to reset the description of the symbol here. When doing
// incremental linking, the output relocatable object may have common
// symbols. Therefore, we can not treat common symbols as normal symbols
// when emitting the regular name pools. We must change the symbols'
// description here.
(*com_sym)->resolveInfo()->setDesc(ResolveInfo::Define);
llvm::MCFragment* frag = new llvm::MCFillFragment(0x0, 1, (*com_sym)->size());
(*com_sym)->setFragmentRef(new MCFragmentRef(*frag, 0));
uint64_t size = pLinker.getLayout().appendFragment(*frag,
bss_section,
(*com_sym)->value());
offset += size;
}
bss_sect_hdr->setSize(offset);
symbol_list.changeCommonsToGlobal();
return true;
}
void ARMGNULDBackend::scanLocalReloc(Relocation& pReloc,
const LDSymbol& pInputSym,
MCLinker& pLinker,
const MCLDInfo& pLDInfo,
const Output& pOutput)
{
// rsym - The relocation target symbol
ResolveInfo* rsym = pReloc.symInfo();
updateAddend(pReloc, pInputSym, pLinker.getLayout());
switch(pReloc.type()){
// Set R_ARM_TARGET1 to R_ARM_ABS32
// Ref: GNU gold 1.11 arm.cc, line 9892
case llvm::ELF::R_ARM_TARGET1:
pReloc.setType(llvm::ELF::R_ARM_ABS32);
case llvm::ELF::R_ARM_ABS32:
case llvm::ELF::R_ARM_ABS32_NOI: {
// If buiding PIC object (shared library or PIC executable),
// a dynamic relocations with RELATIVE type to this location is needed.
// Reserve an entry in .rel.dyn
if(isPIC(pLDInfo, pOutput)) {
// create .rel.dyn section if not exist
if(NULL == m_pRelDyn)
createARMRelDyn(pLinker, pOutput);
m_pRelDyn->reserveEntry(*m_pRelocFactory);
// set Rel bit
rsym->setReserved(rsym->reserved() | 0x1u);
}
return;
}
case llvm::ELF::R_ARM_ABS16:
case llvm::ELF::R_ARM_ABS12:
case llvm::ELF::R_ARM_THM_ABS5:
case llvm::ELF::R_ARM_ABS8:
case llvm::ELF::R_ARM_BASE_ABS:
case llvm::ELF::R_ARM_MOVW_ABS_NC:
case llvm::ELF::R_ARM_MOVT_ABS:
case llvm::ELF::R_ARM_THM_MOVW_ABS_NC:
case llvm::ELF::R_ARM_THM_MOVT_ABS: {
// Update value keep in relocation place if we meet a section symbol
if(rsym->type() == ResolveInfo::Section) {
pReloc.target() = pLinker.getLayout().getOutputOffset(
*pInputSym.fragRef()) + pReloc.target();
}
// If building PIC object (shared library or PIC executable),
// a dynamic relocation for this location is needed.
// Reserve an entry in .rel.dyn
if(isPIC(pLDInfo, pOutput)) {
checkValidReloc(pReloc, pLDInfo, pOutput);
// create .rel.dyn section if not exist
if(NULL == m_pRelDyn)
createARMRelDyn(pLinker, pOutput);
m_pRelDyn->reserveEntry(*m_pRelocFactory);
// set Rel bit
rsym->setReserved(rsym->reserved() | 0x1u);
}
return;
}
case llvm::ELF::R_ARM_GOTOFF32:
case llvm::ELF::R_ARM_GOTOFF12: {
// A GOT section is needed
if(NULL == m_pGOT)
createARMGOT(pLinker, pOutput);
return;
}
// Set R_ARM_TARGET2 to R_ARM_GOT_PREL
// Ref: GNU gold 1.11 arm.cc, line 9892
case llvm::ELF::R_ARM_TARGET2:
pReloc.setType(llvm::ELF::R_ARM_GOT_PREL);
case llvm::ELF::R_ARM_GOT_BREL:
case llvm::ELF::R_ARM_GOT_PREL: {
// A GOT entry is needed for these relocation type.
// return if we already create GOT for this symbol
if(rsym->reserved() & 0x6u)
return;
if(NULL == m_pGOT)
createARMGOT(pLinker, pOutput);
m_pGOT->reserveEntry();
// If building PIC object, a dynamic relocation with
// type RELATIVE is needed to relocate this GOT entry.
// Reserve an entry in .rel.dyn
if(isPIC(pLDInfo, pOutput)) {
// create .rel.dyn section if not exist
if(NULL == m_pRelDyn)
createARMRelDyn(pLinker, pOutput);
m_pRelDyn->reserveEntry(*m_pRelocFactory);
// set GOTRel bit
rsym->setReserved(rsym->reserved() | 0x4u);
return;
}
// set GOT bit
rsym->setReserved(rsym->reserved() | 0x2u);
return;
}
case llvm::ELF::R_ARM_BASE_PREL: {
// FIXME: Currently we only support R_ARM_BASE_PREL against
// symbol _GLOBAL_OFFSET_TABLE_
if(rsym != m_pGOTSymbol->resolveInfo()) {
llvm::report_fatal_error(llvm::Twine("Do not support relocation '") +
llvm::Twine("R_ARM_BASE_PREL' against symbol '") +
llvm::Twine(rsym->name()) +
llvm::Twine(".'"));
}
return;
}
case llvm::ELF::R_ARM_COPY:
case llvm::ELF::R_ARM_GLOB_DAT:
case llvm::ELF::R_ARM_JUMP_SLOT:
case llvm::ELF::R_ARM_RELATIVE: {
// These are relocation type for dynamic linker, shold not
// appear in object file.
llvm::report_fatal_error(llvm::Twine("unexpected reloc ") +
llvm::Twine((int)pReloc.type()) +
llvm::Twine(" in object file"));
break;
}
default: {
break;
}
} // end switch
}