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[asan] Refactor instrumentation of globals.
llvm-svn: 291858
This commit is contained in:
Evgeniy Stepanov
parent
705a43068b
commit
58d4939dad
@ -600,6 +600,22 @@ private:
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void initializeCallbacks(Module &M);
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bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
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void InstrumentGlobalsCOFF(IRBuilder<> &IRB, Module &M,
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ArrayRef<GlobalVariable *> ExtendedGlobals,
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ArrayRef<Constant *> MetadataInitializers);
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void InstrumentGlobalsMachO(IRBuilder<> &IRB, Module &M,
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ArrayRef<GlobalVariable *> ExtendedGlobals,
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ArrayRef<Constant *> MetadataInitializers);
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void
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InstrumentGlobalsWithMetadataArray(IRBuilder<> &IRB, Module &M,
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ArrayRef<GlobalVariable *> ExtendedGlobals,
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ArrayRef<Constant *> MetadataInitializers);
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GlobalVariable *CreateMetadataGlobal(Module &M, Constant *Initializer,
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StringRef OriginalName);
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void SetComdatForGlobalMetadata(GlobalVariable *G, GlobalVariable *Metadata);
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IRBuilder<> CreateAsanModuleDtor(Module &M);
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bool ShouldInstrumentGlobal(GlobalVariable *G);
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bool ShouldUseMachOGlobalsSection() const;
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StringRef getGlobalMetadataSection() const;
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@ -1553,17 +1569,172 @@ void AddressSanitizerModule::initializeCallbacks(Module &M) {
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// Declare the functions that find globals in a shared object and then invoke
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// the (un)register function on them.
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AsanRegisterImageGlobals = checkSanitizerInterfaceFunction(
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M.getOrInsertFunction(kAsanRegisterImageGlobalsName,
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IRB.getVoidTy(), IntptrTy, nullptr));
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AsanRegisterImageGlobals =
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checkSanitizerInterfaceFunction(M.getOrInsertFunction(
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kAsanRegisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
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AsanRegisterImageGlobals->setLinkage(Function::ExternalLinkage);
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AsanUnregisterImageGlobals = checkSanitizerInterfaceFunction(
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M.getOrInsertFunction(kAsanUnregisterImageGlobalsName,
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IRB.getVoidTy(), IntptrTy, nullptr));
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AsanUnregisterImageGlobals =
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checkSanitizerInterfaceFunction(M.getOrInsertFunction(
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kAsanUnregisterImageGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
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AsanUnregisterImageGlobals->setLinkage(Function::ExternalLinkage);
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}
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// Put the metadata and the instrumented global in the same group. This ensures
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// that the metadata is discarded if the instrumented global is discarded.
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void AddressSanitizerModule::SetComdatForGlobalMetadata(
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GlobalVariable *G, GlobalVariable *Metadata) {
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Module &M = *G->getParent();
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Comdat *C = G->getComdat();
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if (!C) {
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if (!G->hasName()) {
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// If G is unnamed, it must be internal. Give it an artificial name
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// so we can put it in a comdat.
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assert(G->hasLocalLinkage());
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G->setName(Twine(kAsanGenPrefix) + "_anon_global");
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}
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C = M.getOrInsertComdat(G->getName());
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// Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF.
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if (TargetTriple.isOSBinFormatCOFF())
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C->setSelectionKind(Comdat::NoDuplicates);
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G->setComdat(C);
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}
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assert(G->hasComdat());
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Metadata->setComdat(G->getComdat());
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}
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// Create a separate metadata global and put it in the appropriate ASan
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// global registration section.
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GlobalVariable *
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AddressSanitizerModule::CreateMetadataGlobal(Module &M, Constant *Initializer,
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StringRef OriginalName) {
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auto &DL = M.getDataLayout();
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GlobalVariable *Metadata =
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new GlobalVariable(M, Initializer->getType(), false,
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GlobalVariable::InternalLinkage, Initializer,
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Twine("__asan_global_") +
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GlobalValue::getRealLinkageName(OriginalName));
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Metadata->setSection(getGlobalMetadataSection());
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// We don't want any padding, but we also need a reasonable alignment.
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// The MSVC linker always inserts padding when linking incrementally. We
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// cope with that by aligning each struct to its size, which must be a power
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// of two.
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unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(Initializer->getType());
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assert(isPowerOf2_32(SizeOfGlobalStruct) &&
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"global metadata will not be padded appropriately");
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Metadata->setAlignment(SizeOfGlobalStruct);
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return Metadata;
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}
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IRBuilder<> AddressSanitizerModule::CreateAsanModuleDtor(Module &M) {
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Function *AsanDtorFunction =
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Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
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GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
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BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
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appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
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return IRBuilder<>(ReturnInst::Create(*C, AsanDtorBB));
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}
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void AddressSanitizerModule::InstrumentGlobalsCOFF(
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IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
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ArrayRef<Constant *> MetadataInitializers) {
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assert(ExtendedGlobals.size() == MetadataInitializers.size());
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for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
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GlobalVariable *G = ExtendedGlobals[i];
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GlobalVariable *Metadata =
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CreateMetadataGlobal(M, MetadataInitializers[i], G->getName());
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SetComdatForGlobalMetadata(G, Metadata);
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}
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}
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void AddressSanitizerModule::InstrumentGlobalsMachO(
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IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
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ArrayRef<Constant *> MetadataInitializers) {
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assert(ExtendedGlobals.size() == MetadataInitializers.size());
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// On recent Mach-O platforms, use a structure which binds the liveness of
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// the global variable to the metadata struct. Keep the list of "Liveness" GV
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// created to be added to llvm.compiler.used
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StructType *LivenessTy = StructType::get(IntptrTy, IntptrTy, nullptr);
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SmallVector<GlobalValue *, 16> LivenessGlobals(ExtendedGlobals.size());
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for (size_t i = 0; i < ExtendedGlobals.size(); i++) {
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Constant *Initializer = MetadataInitializers[i];
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GlobalVariable *G = ExtendedGlobals[i];
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GlobalVariable *Metadata =
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CreateMetadataGlobal(M, Initializer, G->getName());
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// On recent Mach-O platforms, we emit the global metadata in a way that
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// allows the linker to properly strip dead globals.
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auto LivenessBinder = ConstantStruct::get(
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LivenessTy, Initializer->getAggregateElement(0u),
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ConstantExpr::getPointerCast(Metadata, IntptrTy), nullptr);
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GlobalVariable *Liveness = new GlobalVariable(
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M, LivenessTy, false, GlobalVariable::InternalLinkage, LivenessBinder,
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Twine("__asan_binder_") + G->getName());
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Liveness->setSection("__DATA,__asan_liveness,regular,live_support");
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LivenessGlobals[i] = Liveness;
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}
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// Update llvm.compiler.used, adding the new liveness globals. This is
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// needed so that during LTO these variables stay alive. The alternative
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// would be to have the linker handling the LTO symbols, but libLTO
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// current API does not expose access to the section for each symbol.
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if (!LivenessGlobals.empty())
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appendToCompilerUsed(M, LivenessGlobals);
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// RegisteredFlag serves two purposes. First, we can pass it to dladdr()
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// to look up the loaded image that contains it. Second, we can store in it
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// whether registration has already occurred, to prevent duplicate
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// registration.
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//
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// common linkage ensures that there is only one global per shared library.
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GlobalVariable *RegisteredFlag = new GlobalVariable(
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M, IntptrTy, false, GlobalVariable::CommonLinkage,
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ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
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RegisteredFlag->setVisibility(GlobalVariable::HiddenVisibility);
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IRB.CreateCall(AsanRegisterImageGlobals,
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{IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
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// We also need to unregister globals at the end, e.g., when a shared library
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// gets closed.
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IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
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IRB_Dtor.CreateCall(AsanUnregisterImageGlobals,
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{IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
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}
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void AddressSanitizerModule::InstrumentGlobalsWithMetadataArray(
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IRBuilder<> &IRB, Module &M, ArrayRef<GlobalVariable *> ExtendedGlobals,
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ArrayRef<Constant *> MetadataInitializers) {
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assert(ExtendedGlobals.size() == MetadataInitializers.size());
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unsigned N = ExtendedGlobals.size();
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assert(N > 0);
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// On platforms that don't have a custom metadata section, we emit an array
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// of global metadata structures.
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ArrayType *ArrayOfGlobalStructTy =
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ArrayType::get(MetadataInitializers[0]->getType(), N);
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auto AllGlobals = new GlobalVariable(
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M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
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ConstantArray::get(ArrayOfGlobalStructTy, MetadataInitializers), "");
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IRB.CreateCall(AsanRegisterGlobals,
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{IRB.CreatePointerCast(AllGlobals, IntptrTy),
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ConstantInt::get(IntptrTy, N)});
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// We also need to unregister globals at the end, e.g., when a shared library
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// gets closed.
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IRBuilder<> IRB_Dtor = CreateAsanModuleDtor(M);
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IRB_Dtor.CreateCall(AsanUnregisterGlobals,
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{IRB.CreatePointerCast(AllGlobals, IntptrTy),
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ConstantInt::get(IntptrTy, N)});
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}
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// This function replaces all global variables with new variables that have
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// trailing redzones. It also creates a function that poisons
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// redzones and inserts this function into llvm.global_ctors.
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@ -1580,9 +1751,6 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
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if (n == 0) return false;
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auto &DL = M.getDataLayout();
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bool UseComdatMetadata = TargetTriple.isOSBinFormatCOFF();
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bool UseMachOGlobalsSection = ShouldUseMachOGlobalsSection();
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bool UseMetadataArray = !(UseComdatMetadata || UseMachOGlobalsSection);
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// A global is described by a structure
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// size_t beg;
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@ -1597,19 +1765,8 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
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StructType *GlobalStructTy =
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StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
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IntptrTy, IntptrTy, IntptrTy, nullptr);
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unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(GlobalStructTy);
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assert(isPowerOf2_32(SizeOfGlobalStruct) &&
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"global metadata will not be padded appropriately");
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SmallVector<Constant *, 16> Initializers(UseMetadataArray ? n : 0);
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// On recent Mach-O platforms, use a structure which binds the liveness of
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// the global variable to the metadata struct. Keep the list of "Liveness" GV
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// created to be added to llvm.compiler.used
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StructType *LivenessTy = nullptr;
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if (UseMachOGlobalsSection)
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LivenessTy = StructType::get(IntptrTy, IntptrTy, nullptr);
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SmallVector<GlobalValue *, 16> LivenessGlobals(
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UseMachOGlobalsSection ? n : 0);
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SmallVector<GlobalVariable *, 16> NewGlobals(n);
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SmallVector<Constant *, 16> Initializers(n);
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bool HasDynamicallyInitializedGlobals = false;
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@ -1681,25 +1838,7 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
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ConstantExpr::getGetElementPtr(NewTy, NewGlobal, Indices2, true));
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NewGlobal->takeName(G);
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G->eraseFromParent();
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G = NewGlobal;
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if (UseComdatMetadata) {
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// Get or create a COMDAT for G so that we can use it with our metadata.
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Comdat *C = G->getComdat();
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if (!C) {
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if (!G->hasName()) {
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// If G is unnamed, it must be internal. Give it an artificial name
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// so we can put it in a comdat.
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assert(G->hasLocalLinkage());
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G->setName(Twine(kAsanGenPrefix) + "_anon_global");
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}
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C = M.getOrInsertComdat(G->getName());
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// Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF.
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if (TargetTriple.isOSBinFormatCOFF())
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C->setSelectionKind(Comdat::NoDuplicates);
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G->setComdat(C);
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}
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}
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NewGlobals[i] = NewGlobal;
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Constant *SourceLoc;
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if (!MD.SourceLoc.empty()) {
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@ -1750,117 +1889,21 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
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DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
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// If we aren't using separate metadata globals, add it to the initializer
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// list and continue.
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if (UseMetadataArray) {
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Initializers[i] = Initializer;
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continue;
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}
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Initializers[i] = Initializer;
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}
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// Create a separate metadata global and put it in the appropriate ASan
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// global registration section.
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GlobalVariable *Metadata = new GlobalVariable(
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M, GlobalStructTy, false, GlobalVariable::InternalLinkage,
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Initializer, Twine("__asan_global_") +
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GlobalValue::getRealLinkageName(G->getName()));
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Metadata->setSection(getGlobalMetadataSection());
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// We don't want any padding, but we also need a reasonable alignment.
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// The MSVC linker always inserts padding when linking incrementally. We
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// cope with that by aligning each struct to its size, which must be a power
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// of two.
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Metadata->setAlignment(SizeOfGlobalStruct);
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// On platforms that support comdats, put the metadata and the
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// instrumented global in the same group. This ensures that the metadata
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// is discarded if the instrumented global is discarded.
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if (UseComdatMetadata) {
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assert(G->hasComdat());
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Metadata->setComdat(G->getComdat());
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continue;
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}
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assert(UseMachOGlobalsSection);
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// On recent Mach-O platforms, we emit the global metadata in a way that
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// allows the linker to properly strip dead globals.
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auto LivenessBinder = ConstantStruct::get(
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LivenessTy, Initializer->getAggregateElement(0u),
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ConstantExpr::getPointerCast(Metadata, IntptrTy), nullptr);
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GlobalVariable *Liveness = new GlobalVariable(
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M, LivenessTy, false, GlobalVariable::InternalLinkage, LivenessBinder,
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Twine("__asan_binder_") + G->getName());
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Liveness->setSection("__DATA,__asan_liveness,regular,live_support");
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LivenessGlobals[i] = Liveness;
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if (TargetTriple.isOSBinFormatCOFF()) {
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InstrumentGlobalsCOFF(IRB, M, NewGlobals, Initializers);
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} else if (ShouldUseMachOGlobalsSection()) {
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InstrumentGlobalsMachO(IRB, M, NewGlobals, Initializers);
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} else {
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InstrumentGlobalsWithMetadataArray(IRB, M, NewGlobals, Initializers);
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}
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// Create calls for poisoning before initializers run and unpoisoning after.
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if (HasDynamicallyInitializedGlobals)
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createInitializerPoisonCalls(M, ModuleName);
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// Platforms with a dedicated metadata section don't need to emit any more
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// code.
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if (UseComdatMetadata)
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return true;
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GlobalVariable *AllGlobals = nullptr;
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GlobalVariable *RegisteredFlag = nullptr;
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if (UseMachOGlobalsSection) {
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// RegisteredFlag serves two purposes. First, we can pass it to dladdr()
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// to look up the loaded image that contains it. Second, we can store in it
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// whether registration has already occurred, to prevent duplicate
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// registration.
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//
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// common linkage ensures that there is only one global per shared library.
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RegisteredFlag = new GlobalVariable(
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M, IntptrTy, false, GlobalVariable::CommonLinkage,
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ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
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RegisteredFlag->setVisibility(GlobalVariable::HiddenVisibility);
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// Update llvm.compiler.used, adding the new liveness globals. This is
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// needed so that during LTO these variables stay alive. The alternative
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// would be to have the linker handling the LTO symbols, but libLTO
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// current API does not expose access to the section for each symbol.
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if (!LivenessGlobals.empty())
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appendToCompilerUsed(M, LivenessGlobals);
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} else if (UseMetadataArray) {
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// On platforms that don't have a custom metadata section, we emit an array
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// of global metadata structures.
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ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
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AllGlobals = new GlobalVariable(
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M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
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ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
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}
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// Create a call to register the globals with the runtime.
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if (UseMachOGlobalsSection) {
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IRB.CreateCall(AsanRegisterImageGlobals,
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{IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
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} else {
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IRB.CreateCall(AsanRegisterGlobals,
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{IRB.CreatePointerCast(AllGlobals, IntptrTy),
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ConstantInt::get(IntptrTy, n)});
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}
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// We also need to unregister globals at the end, e.g., when a shared library
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// gets closed.
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Function *AsanDtorFunction =
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Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
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GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
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BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
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IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
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if (UseMachOGlobalsSection) {
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IRB_Dtor.CreateCall(AsanUnregisterImageGlobals,
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{IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
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} else {
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IRB_Dtor.CreateCall(AsanUnregisterGlobals,
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{IRB.CreatePointerCast(AllGlobals, IntptrTy),
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ConstantInt::get(IntptrTy, n)});
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}
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appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
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DEBUG(dbgs() << M);
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return true;
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}
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@ -21,13 +21,12 @@ target triple = "x86_64-apple-macosx10.11.0"
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; Find the liveness binder for @global and its metadata:
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; CHECK: @__asan_binder_global = internal global {{.*}} @global {{.*}} [[METADATA]] {{.*}} section "__DATA,__asan_liveness,regular,live_support"
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; Test that there is the flag global variable:
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; CHECK: @__asan_globals_registered = common hidden global i64 0
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; The binder has to be inserted to llvm.compiler.used to avoid being stripped
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; during LTO.
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; CHECK: @llvm.compiler.used {{.*}} @__asan_binder_global {{.*}} section "llvm.metadata"
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; Test that there is the flag global variable:
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; CHECK: @__asan_globals_registered = common hidden global i64 0
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; Test that __asan_register_image_globals is invoked from the constructor:
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; CHECK-LABEL: define internal void @asan.module_ctor
|
||||
|
||||
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