/// computePCBegin - return the address of FDE's pc
/// @ref binutils gold: ehframe.cc:222
uint32_t EhFrameHdr::computePCBegin(const EhFrame::FDE& pFDE,
const MemoryRegion& pEhFrameRegion)
{
uint8_t fde_encoding = pFDE.getCIE().getFDEEncode();
unsigned int eh_value = fde_encoding & 0x7;
// check the size to read in
if (eh_value == llvm::dwarf::DW_EH_PE_absptr) {
eh_value = DW_EH_PE_udata4;
}
size_t pc_size = 0x0;
switch (eh_value) {
case DW_EH_PE_udata2:
pc_size = 2;
break;
case DW_EH_PE_udata4:
pc_size = 4;
break;
case DW_EH_PE_udata8:
pc_size = 8;
break;
default:
// TODO
break;
}
SizeTraits<32>::Address pc = 0x0;
const uint8_t* offset = (const uint8_t*) pEhFrameRegion.start() +
pFDE.getOffset() +
pFDE.getDataStart();
std::memcpy(&pc, offset, pc_size);
// adjust the signed value
bool is_signed = (fde_encoding & llvm::dwarf::DW_EH_PE_signed) != 0x0;
if (DW_EH_PE_udata2 == eh_value && is_signed)
pc = (pc ^ 0x8000) - 0x8000;
// handle eh application
switch (fde_encoding & 0x70)
{
case DW_EH_PE_absptr:
break;
case DW_EH_PE_pcrel:
pc += m_EhFrame.addr() + pFDE.getOffset() + pFDE.getDataStart();
break;
case DW_EH_PE_datarel:
// TODO
break;
default:
// TODO
break;
}
return pc;
}
void X86GNULDBackend::addEhFrameForPLT(Module& pModule)
{
LDSection* plt_sect = pModule.getSection(".plt");
if (!plt_sect || plt_sect->size() == 0u)
return;
LDSection* eh_sect = pModule.getSection(".eh_frame");
if (!eh_sect || !eh_sect->hasEhFrame())
return;
EhFrame* eh_frame = eh_sect->getEhFrame();
SectionData::FragmentListType& frag_list =
eh_frame->getSectionData()->getFragmentList();
llvm::StringRef cie_region = createCIERegionForPLT();
llvm::StringRef fde_region = createFDERegionForPLT();
EhFrame::CIE* cie = new EhFrame::GeneratedCIE(cie_region);
EhFrame::FDE* fde = new EhFrame::GeneratedFDE(fde_region, *cie);
// Augmentation data only contains FDE encoding.
uint8_t aug_data = (uint8_t)(llvm::dwarf::DW_EH_PE_pcrel |
llvm::dwarf::DW_EH_PE_sdata4);
cie->setFDEEncode(aug_data);
cie->setAugmentationData(std::string(1, aug_data));
EhFrame::cie_iterator i = eh_frame->cie_begin();
for (EhFrame::cie_iterator e = eh_frame->cie_end(); i != e; ++i) {
EhFrame::CIE& exist_cie = **i;
if (exist_cie == *cie) {
// Insert the FDE fragment
SectionData::iterator cur_iter(exist_cie);
frag_list.insertAfter(cur_iter, fde);
fde->setCIE(exist_cie);
// Cleanup the CIE we created
cie->clearFDEs();
delete cie;
break;
}
}
if (i == eh_frame->cie_end()) {
// Newly insert
eh_frame->addCIE(*cie);
eh_frame->addFDE(*fde);
}
}
void EhFrame::addFDE(EhFrame::FDE& pFDE, bool pAlsoAddFragment)
{
pFDE.getCIE().add(pFDE);
if (pAlsoAddFragment)
addFragment(pFDE);
}