/// Create - create a fragment reference for a given fragment.
///
/// @param pFrag - the given fragment
/// @param pOffset - the offset, can be larger than the fragment, but can not
/// be larger than the section size.
/// @return if the offset is legal, return the fragment reference. Otherwise,
/// return NULL.
FragmentRef* FragmentRef::Create(Fragment& pFrag, uint64_t pOffset) {
int64_t offset = pOffset;
Fragment* frag = &pFrag;
while (frag != NULL) {
offset -= frag->size();
if (offset <= 0)
break;
frag = frag->getNextNode();
}
if ((frag != NULL) && (frag->size() != 0)) {
if (offset == 0)
frag = frag->getNextNode();
else
offset += frag->size();
}
if (frag == NULL)
return Null();
FragmentRef* result = g_FragRefFactory->allocate();
new (result) FragmentRef(*frag, offset);
return result;
}
void AArch64GNULDBackend::scanErrata(Module& pModule,
IRBuilder& pBuilder,
size_t& num_new_stubs,
size_t& stubs_strlen) {
// TODO: Implement AArch64 ErrataStubFactory to create the specific erratum
// stub and simplify the logics.
for (Module::iterator sect = pModule.begin(), sectEnd = pModule.end();
sect != sectEnd; ++sect) {
if (((*sect)->kind() == LDFileFormat::TEXT) && (*sect)->hasSectionData()) {
SectionData* sd = (*sect)->getSectionData();
for (SectionData::iterator it = sd->begin(), ie = sd->end(); it != ie;
++it) {
Fragment* frag = llvm::dyn_cast<RegionFragment>(it);
if (frag != NULL) {
FragmentRef* frag_ref = FragmentRef::Create(*frag, 0);
for (unsigned offset = 0; offset < frag->size();
offset += AArch64InsnHelpers::InsnSize) {
Stub* stub = getStubFactory()->create(*frag_ref,
pBuilder,
*getBRIslandFactory());
if (stub != NULL) {
// A stub symbol should be local
assert(stub->symInfo() != NULL && stub->symInfo()->isLocal());
const AArch64CA53ErratumStub* erratum_stub =
reinterpret_cast<const AArch64CA53ErratumStub*>(stub);
assert(erratum_stub != NULL);
// Rewrite the erratum instruction as a branch to the stub.
uint64_t offset = frag_ref->offset() +
erratum_stub->getErratumInsnOffset();
Relocation* reloc =
Relocation::Create(llvm::ELF::R_AARCH64_JUMP26,
*(FragmentRef::Create(*frag, offset)),
/* pAddend */0);
reloc->setSymInfo(stub->symInfo());
reloc->target() = AArch64InsnHelpers::buildBranchInsn();
addExtraRelocation(reloc);
++num_new_stubs;
stubs_strlen += stub->symInfo()->nameSize() + 1;
}
frag_ref->assign(*frag, offset + AArch64InsnHelpers::InsnSize);
} // for each INSN
}
} // for each FRAGMENT
}
} // for each TEXT section
}
/// produce - produce a island for the given fragment
/// @param pFragment - the fragment needs a branch island
BranchIsland* BranchIslandFactory::produce(Fragment& pFragment)
{
assert(NULL == find(pFragment));
uint64_t island_offset = pFragment.getOffset() + m_MaxBranchRange -
(pFragment.getOffset() % m_MaxBranchRange);
// find out the last fragment whose offset is smaller than the calculated
// offset of the island
Fragment* frag = &pFragment;
while (NULL != frag->getNextNode()) {
if (frag->getNextNode()->getOffset() > island_offset)
break;
frag = frag->getNextNode();
}
// fall back one step if needed
if (NULL != frag &&
(frag->getOffset() + frag->size()) > island_offset)
frag = frag->getPrevNode();
// check not to break the alignment constraint in the target section
// (i.e., do not insert the island after a Alignment fragment)
while (NULL != frag &&
Fragment::Alignment == frag->getKind()) {
frag = frag->getPrevNode();
}
// can not find an entry fragment to bridge the island
if (NULL == frag)
return NULL;
BranchIsland *island = allocate();
new (island) BranchIsland(*frag, // entry fragment to the island
m_MaxIslandSize, // the max size of the island
size() - 1u); // index in the island factory
return island;
}
void ARMGNULDBackend::rewriteARMExIdxSection(Module& pModule) {
if (!m_pEXIDX->hasSectionData()) {
// Return if this is empty section.
return;
}
SectionData* sectData = m_pEXIDX->getSectionData();
SectionData::FragmentListType& list = sectData->getFragmentList();
// Move the first fragment (align fragment) and last fragment (null fragment)
// to temporary list because we would only like to sort the region fragment.
SectionData::FragmentListType tmp;
{
SectionData::iterator first = sectData->begin();
SectionData::iterator last = sectData->end();
--last;
assert(first->getKind() == Fragment::Alignment);
assert(last->getKind() == Fragment::Null);
tmp.splice(tmp.end(), list, first);
tmp.splice(tmp.end(), list, last);
}
// Sort the region fragments in the .ARM.exidx output section.
sort(list, ExIdxFragmentComparator(m_ExData));
// Fix the coverage of the .ARM.exidx table.
llvm::StringRef cantUnwindRegion(g_CantUnwindEntry,
sizeof(g_CantUnwindEntry));
SectionData::FragmentListType::iterator it = list.begin();
if (it != list.end()) {
Fragment* prevTextFrag = m_ExData.getTupleByExIdx(it)->getTextFragment();
uint64_t prevTextEnd = prevTextFrag->getParent()->getSection().addr() +
prevTextFrag->getOffset() +
prevTextFrag->size();
++it;
while (it != list.end()) {
Fragment* currTextFrag = m_ExData.getTupleByExIdx(it)->getTextFragment();
uint64_t currTextBegin = currTextFrag->getParent()->getSection().addr() +
currTextFrag->getOffset();
if (currTextBegin > prevTextEnd) {
// Found a gap. Insert a can't unwind entry.
RegionFragment* frag = new RegionFragment(cantUnwindRegion, nullptr);
frag->setParent(sectData);
list.insert(it, frag);
// Add PREL31 reference to the beginning of the uncovered region.
Relocation* reloc =
Relocation::Create(static_cast<uint32_t>(llvm::ELF::R_ARM_PREL31),
*FragmentRef::Create(*frag, /* pOffset */0),
/* pAddend */0);
reloc->setSymInfo(
CreateLocalSymbolToFragmentEnd(pModule, *prevTextFrag));
addExtraRelocation(reloc);
}
prevTextEnd = currTextBegin + currTextFrag->size();
prevTextFrag = currTextFrag;
++it;
}
// Add a can't unwind entry to terminate .ARM.exidx section.
RegionFragment* frag = new RegionFragment(cantUnwindRegion, nullptr);
frag->setParent(sectData);
list.push_back(frag);
// Add PREL31 reference to the end of the .text section.
Relocation* reloc =
Relocation::Create(static_cast<uint32_t>(llvm::ELF::R_ARM_PREL31),
*FragmentRef::Create(*frag, /* pOffset */0),
/* pAddend */0);
reloc->setSymInfo(CreateLocalSymbolToFragmentEnd(pModule, *prevTextFrag));
addExtraRelocation(reloc);
}
// Add the first and the last fragment back.
list.splice(list.begin(), tmp, tmp.begin());
list.splice(list.end(), tmp, tmp.begin());
// Update the fragment offsets.
uint64_t offset = 0;
for (SectionData::iterator it = sectData->begin(), end = sectData->end();
it != end; ++it) {
it->setOffset(offset);
offset += it->size();
}
// Update the section size.
m_pEXIDX->setSize(offset);
// Rebuild the section header.
setOutputSectionAddress(pModule);
}
