void StubsPass::perform(MutableFile &mergedFile) {
// Skip this pass if output format uses text relocations instead of stubs.
if ( ! this->noTextRelocs() )
return;
// 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->kind()) ) {
const Atom* target = ref->target();
assert(target != nullptr);
bool replaceCalleeWithStub = false;
if ( target->definition() == Atom::definitionSharedLibrary ) {
// Calls to shared libraries go through stubs.
replaceCalleeWithStub = true;
}
else if (const DefinedAtom* defTarget =
dyn_cast<DefinedAtom>(target)) {
if ( defTarget->interposable() != DefinedAtom::interposeNo ) {
// Calls to interposable functions in same linkage unit
// must also go through a stub.
assert(defTarget->scope() != DefinedAtom::scopeTranslationUnit);
replaceCalleeWithStub = true;
}
}
if ( replaceCalleeWithStub ) {
// Make file-format specific stub and other support atoms.
const DefinedAtom* stub = this->getStub(*target);
assert(stub != nullptr);
// Switch call site to reference stub atom instead.
(const_cast<Reference*>(ref))->setTarget(stub);
}
}
}
}
// Add all created stubs and support Atoms.
this->addStubAtoms(mergedFile);
}
void GOTPass::perform(MutableFile &mergedFile) {
// Use map so all pointers to same symbol use same GOT entry.
llvm::DenseMap<const Atom*, const DefinedAtom*> targetToGOT;
// 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 (!isGOTAccess(ref->kind(), 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.
updateReferenceToGOT(ref, false);
continue;
}
// Replace the target with a reference to a GOT entry.
const DefinedAtom *gotEntry = findGOTAtom(target, targetToGOT);
if (!gotEntry) {
gotEntry = makeGOTEntry(*target);
assert(gotEntry != nullptr);
assert(gotEntry->contentType() == DefinedAtom::typeGOT);
targetToGOT[target] = gotEntry;
}
const_cast<Reference *>(ref)->setTarget(gotEntry);
// Update reference kind to reflect that target is now a GOT entry.
updateReferenceToGOT(ref, true);
}
}
// add all created GOT Atoms to master file
for (auto &it : targetToGOT) {
mergedFile.addAtom(*it.second);
}
}