| //===-- SafeStack.cpp - Safe Stack Insertion ------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass splits the stack into the safe stack (kept as-is for LLVM backend) |
| // and the unsafe stack (explicitly allocated and managed through the runtime |
| // support library). |
| // |
| // http://clang.llvm.org/docs/SafeStack.html |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Instrumentation.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/Triple.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/TargetTransformInfo.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/DIBuilder.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/InstIterator.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/IRBuilder.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/Format.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_os_ostream.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/Transforms/Utils/ModuleUtils.h" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "safestack" |
| |
| namespace llvm { |
| |
| STATISTIC(NumFunctions, "Total number of functions"); |
| STATISTIC(NumUnsafeStackFunctions, "Number of functions with unsafe stack"); |
| STATISTIC(NumUnsafeStackRestorePointsFunctions, |
| "Number of functions that use setjmp or exceptions"); |
| |
| STATISTIC(NumAllocas, "Total number of allocas"); |
| STATISTIC(NumUnsafeStaticAllocas, "Number of unsafe static allocas"); |
| STATISTIC(NumUnsafeDynamicAllocas, "Number of unsafe dynamic allocas"); |
| STATISTIC(NumUnsafeStackRestorePoints, "Number of setjmps and landingpads"); |
| |
| } // namespace llvm |
| |
| namespace { |
| |
| /// Check whether a given alloca instruction (AI) should be put on the safe |
| /// stack or not. The function analyzes all uses of AI and checks whether it is |
| /// only accessed in a memory safe way (as decided statically). |
| bool IsSafeStackAlloca(const AllocaInst *AI) { |
| // Go through all uses of this alloca and check whether all accesses to the |
| // allocated object are statically known to be memory safe and, hence, the |
| // object can be placed on the safe stack. |
| |
| SmallPtrSet<const Value *, 16> Visited; |
| SmallVector<const Instruction *, 8> WorkList; |
| WorkList.push_back(AI); |
| |
| // A DFS search through all uses of the alloca in bitcasts/PHI/GEPs/etc. |
| while (!WorkList.empty()) { |
| const Instruction *V = WorkList.pop_back_val(); |
| for (const Use &UI : V->uses()) { |
| auto I = cast<const Instruction>(UI.getUser()); |
| assert(V == UI.get()); |
| |
| switch (I->getOpcode()) { |
| case Instruction::Load: |
| // Loading from a pointer is safe. |
| break; |
| case Instruction::VAArg: |
| // "va-arg" from a pointer is safe. |
| break; |
| case Instruction::Store: |
| if (V == I->getOperand(0)) |
| // Stored the pointer - conservatively assume it may be unsafe. |
| return false; |
| // Storing to the pointee is safe. |
| break; |
| |
| case Instruction::GetElementPtr: |
| if (!cast<const GetElementPtrInst>(I)->hasAllConstantIndices()) |
| // GEP with non-constant indices can lead to memory errors. |
| // This also applies to inbounds GEPs, as the inbounds attribute |
| // represents an assumption that the address is in bounds, rather than |
| // an assertion that it is. |
| return false; |
| |
| // We assume that GEP on static alloca with constant indices is safe, |
| // otherwise a compiler would detect it and warn during compilation. |
| |
| if (!isa<const ConstantInt>(AI->getArraySize())) |
| // However, if the array size itself is not constant, the access |
| // might still be unsafe at runtime. |
| return false; |
| |
| /* fallthrough */ |
| |
| case Instruction::BitCast: |
| case Instruction::IntToPtr: |
| case Instruction::PHI: |
| case Instruction::PtrToInt: |
| case Instruction::Select: |
| // The object can be safe or not, depending on how the result of the |
| // instruction is used. |
| if (Visited.insert(I).second) |
| WorkList.push_back(cast<const Instruction>(I)); |
| break; |
| |
| case Instruction::Call: |
| case Instruction::Invoke: { |
| // FIXME: add support for memset and memcpy intrinsics. |
| ImmutableCallSite CS(I); |
| |
| // LLVM 'nocapture' attribute is only set for arguments whose address |
| // is not stored, passed around, or used in any other non-trivial way. |
| // We assume that passing a pointer to an object as a 'nocapture' |
| // argument is safe. |
| // FIXME: a more precise solution would require an interprocedural |
| // analysis here, which would look at all uses of an argument inside |
| // the function being called. |
| ImmutableCallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end(); |
| for (ImmutableCallSite::arg_iterator A = B; A != E; ++A) |
| if (A->get() == V && !CS.doesNotCapture(A - B)) |
| // The parameter is not marked 'nocapture' - unsafe. |
| return false; |
| continue; |
| } |
| |
| default: |
| // The object is unsafe if it is used in any other way. |
| return false; |
| } |
| } |
| } |
| |
| // All uses of the alloca are safe, we can place it on the safe stack. |
| return true; |
| } |
| |
| /// The SafeStack pass splits the stack of each function into the |
| /// safe stack, which is only accessed through memory safe dereferences |
| /// (as determined statically), and the unsafe stack, which contains all |
| /// local variables that are accessed in unsafe ways. |
| class SafeStack : public FunctionPass { |
| const DataLayout *DL; |
| |
| Type *StackPtrTy; |
| Type *IntPtrTy; |
| Type *Int32Ty; |
| Type *Int8Ty; |
| |
| Constant *UnsafeStackPtr = nullptr; |
| |
| /// Unsafe stack alignment. Each stack frame must ensure that the stack is |
| /// aligned to this value. We need to re-align the unsafe stack if the |
| /// alignment of any object on the stack exceeds this value. |
| /// |
| /// 16 seems like a reasonable upper bound on the alignment of objects that we |
| /// might expect to appear on the stack on most common targets. |
| enum { StackAlignment = 16 }; |
| |
| /// \brief Build a constant representing a pointer to the unsafe stack |
| /// pointer. |
| Constant *getOrCreateUnsafeStackPtr(Module &M); |
| |
| /// \brief Find all static allocas, dynamic allocas, return instructions and |
| /// stack restore points (exception unwind blocks and setjmp calls) in the |
| /// given function and append them to the respective vectors. |
| void findInsts(Function &F, SmallVectorImpl<AllocaInst *> &StaticAllocas, |
| SmallVectorImpl<AllocaInst *> &DynamicAllocas, |
| SmallVectorImpl<ReturnInst *> &Returns, |
| SmallVectorImpl<Instruction *> &StackRestorePoints); |
| |
| /// \brief Allocate space for all static allocas in \p StaticAllocas, |
| /// replace allocas with pointers into the unsafe stack and generate code to |
| /// restore the stack pointer before all return instructions in \p Returns. |
| /// |
| /// \returns A pointer to the top of the unsafe stack after all unsafe static |
| /// allocas are allocated. |
| Value *moveStaticAllocasToUnsafeStack(Function &F, |
| ArrayRef<AllocaInst *> StaticAllocas, |
| ArrayRef<ReturnInst *> Returns); |
| |
| /// \brief Generate code to restore the stack after all stack restore points |
| /// in \p StackRestorePoints. |
| /// |
| /// \returns A local variable in which to maintain the dynamic top of the |
| /// unsafe stack if needed. |
| AllocaInst * |
| createStackRestorePoints(Function &F, |
| ArrayRef<Instruction *> StackRestorePoints, |
| Value *StaticTop, bool NeedDynamicTop); |
| |
| /// \brief Replace all allocas in \p DynamicAllocas with code to allocate |
| /// space dynamically on the unsafe stack and store the dynamic unsafe stack |
| /// top to \p DynamicTop if non-null. |
| void moveDynamicAllocasToUnsafeStack(Function &F, Value *UnsafeStackPtr, |
| AllocaInst *DynamicTop, |
| ArrayRef<AllocaInst *> DynamicAllocas); |
| |
| public: |
| static char ID; // Pass identification, replacement for typeid. |
| SafeStack() : FunctionPass(ID), DL(nullptr) { |
| initializeSafeStackPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<AliasAnalysis>(); |
| } |
| |
| virtual bool doInitialization(Module &M) { |
| DL = &M.getDataLayout(); |
| |
| StackPtrTy = Type::getInt8PtrTy(M.getContext()); |
| IntPtrTy = DL->getIntPtrType(M.getContext()); |
| Int32Ty = Type::getInt32Ty(M.getContext()); |
| Int8Ty = Type::getInt8Ty(M.getContext()); |
| |
| return false; |
| } |
| |
| bool runOnFunction(Function &F); |
| |
| }; // class SafeStack |
| |
| Constant *SafeStack::getOrCreateUnsafeStackPtr(Module &M) { |
| // The unsafe stack pointer is stored in a global variable with a magic name. |
| const char *kUnsafeStackPtrVar = "__safestack_unsafe_stack_ptr"; |
| |
| auto UnsafeStackPtr = |
| dyn_cast_or_null<GlobalVariable>(M.getNamedValue(kUnsafeStackPtrVar)); |
| |
| if (!UnsafeStackPtr) { |
| // The global variable is not defined yet, define it ourselves. |
| // We use the initial-exec TLS model because we do not support the variable |
| // living anywhere other than in the main executable. |
| UnsafeStackPtr = new GlobalVariable( |
| /*Module=*/M, /*Type=*/StackPtrTy, |
| /*isConstant=*/false, /*Linkage=*/GlobalValue::ExternalLinkage, |
| /*Initializer=*/0, /*Name=*/kUnsafeStackPtrVar, |
| /*InsertBefore=*/nullptr, |
| /*ThreadLocalMode=*/GlobalValue::InitialExecTLSModel); |
| } else { |
| // The variable exists, check its type and attributes. |
| if (UnsafeStackPtr->getValueType() != StackPtrTy) { |
| report_fatal_error(Twine(kUnsafeStackPtrVar) + " must have void* type"); |
| } |
| |
| if (!UnsafeStackPtr->isThreadLocal()) { |
| report_fatal_error(Twine(kUnsafeStackPtrVar) + " must be thread-local"); |
| } |
| } |
| |
| return UnsafeStackPtr; |
| } |
| |
| void SafeStack::findInsts(Function &F, |
| SmallVectorImpl<AllocaInst *> &StaticAllocas, |
| SmallVectorImpl<AllocaInst *> &DynamicAllocas, |
| SmallVectorImpl<ReturnInst *> &Returns, |
| SmallVectorImpl<Instruction *> &StackRestorePoints) { |
| for (Instruction &I : inst_range(&F)) { |
| if (auto AI = dyn_cast<AllocaInst>(&I)) { |
| ++NumAllocas; |
| |
| if (IsSafeStackAlloca(AI)) |
| continue; |
| |
| if (AI->isStaticAlloca()) { |
| ++NumUnsafeStaticAllocas; |
| StaticAllocas.push_back(AI); |
| } else { |
| ++NumUnsafeDynamicAllocas; |
| DynamicAllocas.push_back(AI); |
| } |
| } else if (auto RI = dyn_cast<ReturnInst>(&I)) { |
| Returns.push_back(RI); |
| } else if (auto CI = dyn_cast<CallInst>(&I)) { |
| // setjmps require stack restore. |
| if (CI->getCalledFunction() && CI->canReturnTwice()) |
| StackRestorePoints.push_back(CI); |
| } else if (auto LP = dyn_cast<LandingPadInst>(&I)) { |
| // Exception landing pads require stack restore. |
| StackRestorePoints.push_back(LP); |
| } else if (auto II = dyn_cast<IntrinsicInst>(&I)) { |
| if (II->getIntrinsicID() == Intrinsic::gcroot) |
| llvm::report_fatal_error( |
| "gcroot intrinsic not compatible with safestack attribute"); |
| } |
| } |
| } |
| |
| AllocaInst * |
| SafeStack::createStackRestorePoints(Function &F, |
| ArrayRef<Instruction *> StackRestorePoints, |
| Value *StaticTop, bool NeedDynamicTop) { |
| if (StackRestorePoints.empty()) |
| return nullptr; |
| |
| IRBuilder<> IRB(StaticTop |
| ? cast<Instruction>(StaticTop)->getNextNode() |
| : (Instruction *)F.getEntryBlock().getFirstInsertionPt()); |
| |
| // We need the current value of the shadow stack pointer to restore |
| // after longjmp or exception catching. |
| |
| // FIXME: On some platforms this could be handled by the longjmp/exception |
| // runtime itself. |
| |
| AllocaInst *DynamicTop = nullptr; |
| if (NeedDynamicTop) |
| // If we also have dynamic alloca's, the stack pointer value changes |
| // throughout the function. For now we store it in an alloca. |
| DynamicTop = IRB.CreateAlloca(StackPtrTy, /*ArraySize=*/nullptr, |
| "unsafe_stack_dynamic_ptr"); |
| |
| if (!StaticTop) |
| // We need the original unsafe stack pointer value, even if there are |
| // no unsafe static allocas. |
| StaticTop = IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr"); |
| |
| if (NeedDynamicTop) |
| IRB.CreateStore(StaticTop, DynamicTop); |
| |
| // Restore current stack pointer after longjmp/exception catch. |
| for (Instruction *I : StackRestorePoints) { |
| ++NumUnsafeStackRestorePoints; |
| |
| IRB.SetInsertPoint(cast<Instruction>(I->getNextNode())); |
| Value *CurrentTop = DynamicTop ? IRB.CreateLoad(DynamicTop) : StaticTop; |
| IRB.CreateStore(CurrentTop, UnsafeStackPtr); |
| } |
| |
| return DynamicTop; |
| } |
| |
| Value * |
| SafeStack::moveStaticAllocasToUnsafeStack(Function &F, |
| ArrayRef<AllocaInst *> StaticAllocas, |
| ArrayRef<ReturnInst *> Returns) { |
| if (StaticAllocas.empty()) |
| return nullptr; |
| |
| IRBuilder<> IRB(F.getEntryBlock().getFirstInsertionPt()); |
| DIBuilder DIB(*F.getParent()); |
| |
| // We explicitly compute and set the unsafe stack layout for all unsafe |
| // static alloca instructions. We save the unsafe "base pointer" in the |
| // prologue into a local variable and restore it in the epilogue. |
| |
| // Load the current stack pointer (we'll also use it as a base pointer). |
| // FIXME: use a dedicated register for it ? |
| Instruction *BasePointer = |
| IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr"); |
| assert(BasePointer->getType() == StackPtrTy); |
| |
| for (ReturnInst *RI : Returns) { |
| IRB.SetInsertPoint(RI); |
| IRB.CreateStore(BasePointer, UnsafeStackPtr); |
| } |
| |
| // Compute maximum alignment among static objects on the unsafe stack. |
| unsigned MaxAlignment = 0; |
| for (AllocaInst *AI : StaticAllocas) { |
| Type *Ty = AI->getAllocatedType(); |
| unsigned Align = |
| std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI->getAlignment()); |
| if (Align > MaxAlignment) |
| MaxAlignment = Align; |
| } |
| |
| if (MaxAlignment > StackAlignment) { |
| // Re-align the base pointer according to the max requested alignment. |
| assert(isPowerOf2_32(MaxAlignment)); |
| IRB.SetInsertPoint(cast<Instruction>(BasePointer->getNextNode())); |
| BasePointer = cast<Instruction>(IRB.CreateIntToPtr( |
| IRB.CreateAnd(IRB.CreatePtrToInt(BasePointer, IntPtrTy), |
| ConstantInt::get(IntPtrTy, ~uint64_t(MaxAlignment - 1))), |
| StackPtrTy)); |
| } |
| |
| // Allocate space for every unsafe static AllocaInst on the unsafe stack. |
| int64_t StaticOffset = 0; // Current stack top. |
| for (AllocaInst *AI : StaticAllocas) { |
| IRB.SetInsertPoint(AI); |
| |
| auto CArraySize = cast<ConstantInt>(AI->getArraySize()); |
| Type *Ty = AI->getAllocatedType(); |
| |
| uint64_t Size = DL->getTypeAllocSize(Ty) * CArraySize->getZExtValue(); |
| if (Size == 0) |
| Size = 1; // Don't create zero-sized stack objects. |
| |
| // Ensure the object is properly aligned. |
| unsigned Align = |
| std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI->getAlignment()); |
| |
| // Add alignment. |
| // NOTE: we ensure that BasePointer itself is aligned to >= Align. |
| StaticOffset += Size; |
| StaticOffset = RoundUpToAlignment(StaticOffset, Align); |
| |
| Value *Off = IRB.CreateGEP(BasePointer, // BasePointer is i8* |
| ConstantInt::get(Int32Ty, -StaticOffset)); |
| Value *NewAI = IRB.CreateBitCast(Off, AI->getType(), AI->getName()); |
| if (AI->hasName() && isa<Instruction>(NewAI)) |
| cast<Instruction>(NewAI)->takeName(AI); |
| |
| // Replace alloc with the new location. |
| replaceDbgDeclareForAlloca(AI, NewAI, DIB, /*Deref=*/true); |
| AI->replaceAllUsesWith(NewAI); |
| AI->eraseFromParent(); |
| } |
| |
| // Re-align BasePointer so that our callees would see it aligned as |
| // expected. |
| // FIXME: no need to update BasePointer in leaf functions. |
| StaticOffset = RoundUpToAlignment(StaticOffset, StackAlignment); |
| |
| // Update shadow stack pointer in the function epilogue. |
| IRB.SetInsertPoint(cast<Instruction>(BasePointer->getNextNode())); |
| |
| Value *StaticTop = |
| IRB.CreateGEP(BasePointer, ConstantInt::get(Int32Ty, -StaticOffset), |
| "unsafe_stack_static_top"); |
| IRB.CreateStore(StaticTop, UnsafeStackPtr); |
| return StaticTop; |
| } |
| |
| void SafeStack::moveDynamicAllocasToUnsafeStack( |
| Function &F, Value *UnsafeStackPtr, AllocaInst *DynamicTop, |
| ArrayRef<AllocaInst *> DynamicAllocas) { |
| DIBuilder DIB(*F.getParent()); |
| |
| for (AllocaInst *AI : DynamicAllocas) { |
| IRBuilder<> IRB(AI); |
| |
| // Compute the new SP value (after AI). |
| Value *ArraySize = AI->getArraySize(); |
| if (ArraySize->getType() != IntPtrTy) |
| ArraySize = IRB.CreateIntCast(ArraySize, IntPtrTy, false); |
| |
| Type *Ty = AI->getAllocatedType(); |
| uint64_t TySize = DL->getTypeAllocSize(Ty); |
| Value *Size = IRB.CreateMul(ArraySize, ConstantInt::get(IntPtrTy, TySize)); |
| |
| Value *SP = IRB.CreatePtrToInt(IRB.CreateLoad(UnsafeStackPtr), IntPtrTy); |
| SP = IRB.CreateSub(SP, Size); |
| |
| // Align the SP value to satisfy the AllocaInst, type and stack alignments. |
| unsigned Align = std::max( |
| std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI->getAlignment()), |
| (unsigned)StackAlignment); |
| |
| assert(isPowerOf2_32(Align)); |
| Value *NewTop = IRB.CreateIntToPtr( |
| IRB.CreateAnd(SP, ConstantInt::get(IntPtrTy, ~uint64_t(Align - 1))), |
| StackPtrTy); |
| |
| // Save the stack pointer. |
| IRB.CreateStore(NewTop, UnsafeStackPtr); |
| if (DynamicTop) |
| IRB.CreateStore(NewTop, DynamicTop); |
| |
| Value *NewAI = IRB.CreateIntToPtr(SP, AI->getType()); |
| if (AI->hasName() && isa<Instruction>(NewAI)) |
| NewAI->takeName(AI); |
| |
| replaceDbgDeclareForAlloca(AI, NewAI, DIB, /*Deref=*/true); |
| AI->replaceAllUsesWith(NewAI); |
| AI->eraseFromParent(); |
| } |
| |
| if (!DynamicAllocas.empty()) { |
| // Now go through the instructions again, replacing stacksave/stackrestore. |
| for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) { |
| Instruction *I = &*(It++); |
| auto II = dyn_cast<IntrinsicInst>(I); |
| if (!II) |
| continue; |
| |
| if (II->getIntrinsicID() == Intrinsic::stacksave) { |
| IRBuilder<> IRB(II); |
| Instruction *LI = IRB.CreateLoad(UnsafeStackPtr); |
| LI->takeName(II); |
| II->replaceAllUsesWith(LI); |
| II->eraseFromParent(); |
| } else if (II->getIntrinsicID() == Intrinsic::stackrestore) { |
| IRBuilder<> IRB(II); |
| Instruction *SI = IRB.CreateStore(II->getArgOperand(0), UnsafeStackPtr); |
| SI->takeName(II); |
| assert(II->use_empty()); |
| II->eraseFromParent(); |
| } |
| } |
| } |
| } |
| |
| bool SafeStack::runOnFunction(Function &F) { |
| auto AA = &getAnalysis<AliasAnalysis>(); |
| |
| DEBUG(dbgs() << "[SafeStack] Function: " << F.getName() << "\n"); |
| |
| if (!F.hasFnAttribute(Attribute::SafeStack)) { |
| DEBUG(dbgs() << "[SafeStack] safestack is not requested" |
| " for this function\n"); |
| return false; |
| } |
| |
| if (F.isDeclaration()) { |
| DEBUG(dbgs() << "[SafeStack] function definition" |
| " is not available\n"); |
| return false; |
| } |
| |
| { |
| // Make sure the regular stack protector won't run on this function |
| // (safestack attribute takes precedence). |
| AttrBuilder B; |
| B.addAttribute(Attribute::StackProtect) |
| .addAttribute(Attribute::StackProtectReq) |
| .addAttribute(Attribute::StackProtectStrong); |
| F.removeAttributes( |
| AttributeSet::FunctionIndex, |
| AttributeSet::get(F.getContext(), AttributeSet::FunctionIndex, B)); |
| } |
| |
| if (AA->onlyReadsMemory(&F)) { |
| // XXX: we don't protect against information leak attacks for now. |
| DEBUG(dbgs() << "[SafeStack] function only reads memory\n"); |
| return false; |
| } |
| |
| ++NumFunctions; |
| |
| SmallVector<AllocaInst *, 16> StaticAllocas; |
| SmallVector<AllocaInst *, 4> DynamicAllocas; |
| SmallVector<ReturnInst *, 4> Returns; |
| |
| // Collect all points where stack gets unwound and needs to be restored |
| // This is only necessary because the runtime (setjmp and unwind code) is |
| // not aware of the unsafe stack and won't unwind/restore it prorerly. |
| // To work around this problem without changing the runtime, we insert |
| // instrumentation to restore the unsafe stack pointer when necessary. |
| SmallVector<Instruction *, 4> StackRestorePoints; |
| |
| // Find all static and dynamic alloca instructions that must be moved to the |
| // unsafe stack, all return instructions and stack restore points. |
| findInsts(F, StaticAllocas, DynamicAllocas, Returns, StackRestorePoints); |
| |
| if (StaticAllocas.empty() && DynamicAllocas.empty() && |
| StackRestorePoints.empty()) |
| return false; // Nothing to do in this function. |
| |
| if (!StaticAllocas.empty() || !DynamicAllocas.empty()) |
| ++NumUnsafeStackFunctions; // This function has the unsafe stack. |
| |
| if (!StackRestorePoints.empty()) |
| ++NumUnsafeStackRestorePointsFunctions; |
| |
| if (!UnsafeStackPtr) |
| UnsafeStackPtr = getOrCreateUnsafeStackPtr(*F.getParent()); |
| |
| // The top of the unsafe stack after all unsafe static allocas are allocated. |
| Value *StaticTop = moveStaticAllocasToUnsafeStack(F, StaticAllocas, Returns); |
| |
| // Safe stack object that stores the current unsafe stack top. It is updated |
| // as unsafe dynamic (non-constant-sized) allocas are allocated and freed. |
| // This is only needed if we need to restore stack pointer after longjmp |
| // or exceptions, and we have dynamic allocations. |
| // FIXME: a better alternative might be to store the unsafe stack pointer |
| // before setjmp / invoke instructions. |
| AllocaInst *DynamicTop = createStackRestorePoints( |
| F, StackRestorePoints, StaticTop, !DynamicAllocas.empty()); |
| |
| // Handle dynamic allocas. |
| moveDynamicAllocasToUnsafeStack(F, UnsafeStackPtr, DynamicTop, |
| DynamicAllocas); |
| |
| DEBUG(dbgs() << "[SafeStack] safestack applied\n"); |
| return true; |
| } |
| |
| } // end anonymous namespace |
| |
| char SafeStack::ID = 0; |
| INITIALIZE_PASS_BEGIN(SafeStack, "safe-stack", |
| "Safe Stack instrumentation pass", false, false) |
| INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) |
| INITIALIZE_PASS_END(SafeStack, "safe-stack", "Safe Stack instrumentation pass", |
| false, false) |
| |
| FunctionPass *llvm::createSafeStackPass() { return new SafeStack(); } |