llvm::Error perform(SimpleFile &mergedFile) override {
// Scan all references in all atoms.
for (const DefinedAtom *atom : mergedFile.defined()) {
for (const Reference *ref : *atom) {
// Look at instructions accessing the GOT.
bool canBypassGOT;
if (!_archHandler.isGOTAccess(*ref, canBypassGOT))
continue;
const Atom *target = ref->target();
assert(target != nullptr);
if (!shouldReplaceTargetWithGOTAtom(target, canBypassGOT)) {
// Update reference kind to reflect that target is a direct accesss.
_archHandler.updateReferenceToGOT(ref, false);
} else {
// Replace the target with a reference to a GOT entry.
const DefinedAtom *gotEntry = makeGOTEntry(target);
const_cast<Reference *>(ref)->setTarget(gotEntry);
// Update reference kind to reflect that target is now a GOT entry.
_archHandler.updateReferenceToGOT(ref, true);
}
}
}
// Sort and add all created GOT Atoms to master file
std::vector<const GOTEntryAtom *> entries;
entries.reserve(_targetToGOT.size());
for (auto &it : _targetToGOT)
entries.push_back(it.second);
std::sort(entries.begin(), entries.end(),
[](const GOTEntryAtom *left, const GOTEntryAtom *right) {
return (left->slotName().compare(right->slotName()) < 0);
});
for (const GOTEntryAtom *slot : entries)
mergedFile.addAtom(*slot);
return llvm::Error::success();
}
std::error_code perform(SimpleFile &mergedFile) override {
// Skip this pass if output format uses text relocations instead of stubs.
if (!this->noTextRelocs())
return std::error_code();
// Scan all references in all atoms.
for (const DefinedAtom *atom : mergedFile.defined()) {
for (const Reference *ref : *atom) {
// Look at call-sites.
if (!this->isCallSite(*ref))
continue;
const Atom *target = ref->target();
assert(target != nullptr);
if (isa<SharedLibraryAtom>(target)) {
// Calls to shared libraries go through stubs.
_targetToUses[target].push_back(ref);
continue;
}
const DefinedAtom *defTarget = dyn_cast<DefinedAtom>(target);
if (defTarget && defTarget->interposable() != DefinedAtom::interposeNo){
// Calls to interposable functions in same linkage unit must also go
// through a stub.
assert(defTarget->scope() != DefinedAtom::scopeTranslationUnit);
_targetToUses[target].push_back(ref);
}
}
}
// Exit early if no stubs needed.
if (_targetToUses.empty())
return std::error_code();
// First add help-common and GOT slots used by lazy binding.
SimpleDefinedAtom *helperCommonAtom =
new (_file.allocator()) StubHelperCommonAtom(_file, _stubInfo);
SimpleDefinedAtom *helperCacheNLPAtom =
new (_file.allocator()) NonLazyPointerAtom(_file, _ctx.is64Bit());
SimpleDefinedAtom *helperBinderNLPAtom =
new (_file.allocator()) NonLazyPointerAtom(_file, _ctx.is64Bit());
addReference(helperCommonAtom, _stubInfo.stubHelperCommonReferenceToCache,
helperCacheNLPAtom);
addOptReference(
helperCommonAtom, _stubInfo.stubHelperCommonReferenceToCache,
_stubInfo.optStubHelperCommonReferenceToCache, helperCacheNLPAtom);
addReference(helperCommonAtom, _stubInfo.stubHelperCommonReferenceToBinder,
helperBinderNLPAtom);
addOptReference(
helperCommonAtom, _stubInfo.stubHelperCommonReferenceToBinder,
_stubInfo.optStubHelperCommonReferenceToBinder, helperBinderNLPAtom);
mergedFile.addAtom(*helperCommonAtom);
mergedFile.addAtom(*helperBinderNLPAtom);
mergedFile.addAtom(*helperCacheNLPAtom);
// Add reference to dyld_stub_binder in libSystem.dylib
auto I = std::find_if(
mergedFile.sharedLibrary().begin(), mergedFile.sharedLibrary().end(),
[&](const SharedLibraryAtom *atom) {
return atom->name().equals(_stubInfo.binderSymbolName);
});
assert(I != mergedFile.sharedLibrary().end() &&
"dyld_stub_binder not found");
addReference(helperBinderNLPAtom, _stubInfo.nonLazyPointerReferenceToBinder, *I);
// Sort targets by name, so stubs and lazy pointers are consistent
std::vector<const Atom *> targetsNeedingStubs;
for (auto it : _targetToUses)
targetsNeedingStubs.push_back(it.first);
std::sort(targetsNeedingStubs.begin(), targetsNeedingStubs.end(),
[](const Atom * left, const Atom * right) {
return (left->name().compare(right->name()) < 0);
});
// Make and append stubs, lazy pointers, and helpers in alphabetical order.
unsigned lazyOffset = 0;
for (const Atom *target : targetsNeedingStubs) {
auto *stub = new (_file.allocator()) StubAtom(_file, _stubInfo);
auto *lp =
new (_file.allocator()) LazyPointerAtom(_file, _ctx.is64Bit());
auto *helper = new (_file.allocator()) StubHelperAtom(_file, _stubInfo);
addReference(stub, _stubInfo.stubReferenceToLP, lp);
addOptReference(stub, _stubInfo.stubReferenceToLP,
_stubInfo.optStubReferenceToLP, lp);
addReference(lp, _stubInfo.lazyPointerReferenceToHelper, helper);
addReference(lp, _stubInfo.lazyPointerReferenceToFinal, target);
addReference(helper, _stubInfo.stubHelperReferenceToImm, helper);
addReferenceAddend(helper, _stubInfo.stubHelperReferenceToImm, helper,
lazyOffset);
addReference(helper, _stubInfo.stubHelperReferenceToHelperCommon,
helperCommonAtom);
mergedFile.addAtom(*stub);
mergedFile.addAtom(*lp);
mergedFile.addAtom(*helper);
// Update each reference to use stub.
for (const Reference *ref : _targetToUses[target]) {
assert(ref->target() == target);
// Switch call site to reference stub atom instead.
const_cast<Reference *>(ref)->setTarget(stub);
}
// Calculate new offset
lazyOffset += target->name().size() + 12;
}
return std::error_code();
}
std::error_code perform(SimpleFile &mergedFile) override {
// Add the image info.
mergedFile.addAtom(*getImageInfo());
return std::error_code();
}
llvm::Error perform(SimpleFile &mergedFile) override {
DEBUG(llvm::dbgs() << "MachO Compact Unwind pass\n");
std::map<const Atom *, CompactUnwindEntry> unwindLocs;
std::map<const Atom *, const Atom *> dwarfFrames;
std::vector<const Atom *> personalities;
uint32_t numLSDAs = 0;
// First collect all __compact_unwind and __eh_frame entries, addressable by
// the function referred to.
collectCompactUnwindEntries(mergedFile, unwindLocs, personalities,
numLSDAs);
collectDwarfFrameEntries(mergedFile, dwarfFrames);
// Skip rest of pass if no unwind info.
if (unwindLocs.empty() && dwarfFrames.empty())
return llvm::Error::success();
// FIXME: if there are more than 4 personality functions then we need to
// defer to DWARF info for the ones we don't put in the list. They should
// also probably be sorted by frequency.
assert(personalities.size() <= 4);
// TODO: Find commmon encodings for use by compressed pages.
std::vector<uint32_t> commonEncodings;
// Now sort the entries by final address and fixup the compact encoding to
// its final form (i.e. set personality function bits & create DWARF
// references where needed).
std::vector<CompactUnwindEntry> unwindInfos = createUnwindInfoEntries(
mergedFile, unwindLocs, personalities, dwarfFrames);
// Remove any unused eh-frame atoms.
pruneUnusedEHFrames(mergedFile, unwindInfos, unwindLocs, dwarfFrames);
// Finally, we can start creating pages based on these entries.
DEBUG(llvm::dbgs() << " Splitting entries into pages\n");
// FIXME: we split the entries into pages naively: lots of 4k pages followed
// by a small one. ld64 tried to minimize space and align them to real 4k
// boundaries. That might be worth doing, or perhaps we could perform some
// minor balancing for expected number of lookups.
std::vector<UnwindInfoPage> pages;
auto remainingInfos = llvm::makeArrayRef(unwindInfos);
do {
pages.push_back(UnwindInfoPage());
// FIXME: we only create regular pages at the moment. These can hold up to
// 1021 entries according to the documentation.
unsigned entriesInPage = std::min(1021U, (unsigned)remainingInfos.size());
pages.back().entries = remainingInfos.slice(0, entriesInPage);
remainingInfos = remainingInfos.slice(entriesInPage);
DEBUG(llvm::dbgs()
<< " Page from " << pages.back().entries[0].rangeStart->name()
<< " to " << pages.back().entries.back().rangeStart->name() << " + "
<< llvm::format("0x%x", pages.back().entries.back().rangeLength)
<< " has " << entriesInPage << " entries\n");
} while (!remainingInfos.empty());
auto *unwind = new (_file.allocator())
UnwindInfoAtom(_archHandler, _file, _isBig, personalities,
commonEncodings, pages, numLSDAs);
mergedFile.addAtom(*unwind);
// Finally, remove all __compact_unwind atoms now that we've processed them.
mergedFile.removeDefinedAtomsIf([](const DefinedAtom *atom) {
return atom->contentType() == DefinedAtom::typeCompactUnwindInfo;
});
return llvm::Error::success();
}
