1 //===-- SafeStack.cpp - Safe Stack Insertion ------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass splits the stack into the safe stack (kept as-is for LLVM backend)
11 // and the unsafe stack (explicitly allocated and managed through the runtime
14 // http://clang.llvm.org/docs/SafeStack.html
16 //===----------------------------------------------------------------------===//
18 #include "llvm/Transforms/Instrumentation.h"
19 #include "llvm/ADT/Statistic.h"
20 #include "llvm/ADT/Triple.h"
21 #include "llvm/Analysis/AliasAnalysis.h"
22 #include "llvm/CodeGen/Passes.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DataLayout.h"
25 #include "llvm/IR/DerivedTypes.h"
26 #include "llvm/IR/DIBuilder.h"
27 #include "llvm/IR/Function.h"
28 #include "llvm/IR/InstIterator.h"
29 #include "llvm/IR/Instructions.h"
30 #include "llvm/IR/IntrinsicInst.h"
31 #include "llvm/IR/Intrinsics.h"
32 #include "llvm/IR/IRBuilder.h"
33 #include "llvm/IR/Module.h"
34 #include "llvm/Pass.h"
35 #include "llvm/Support/CommandLine.h"
36 #include "llvm/Support/Debug.h"
37 #include "llvm/Support/Format.h"
38 #include "llvm/Support/MathExtras.h"
39 #include "llvm/Support/raw_os_ostream.h"
40 #include "llvm/Target/TargetLowering.h"
41 #include "llvm/Target/TargetSubtargetInfo.h"
42 #include "llvm/Transforms/Utils/Local.h"
43 #include "llvm/Transforms/Utils/ModuleUtils.h"
47 #define DEBUG_TYPE "safestack"
49 static const char *const kUnsafeStackPtrVar = "__safestack_unsafe_stack_ptr";
50 static const char *const kUnsafeStackPtrAddrFn = "__safestack_pointer_address";
54 STATISTIC(NumFunctions, "Total number of functions");
55 STATISTIC(NumUnsafeStackFunctions, "Number of functions with unsafe stack");
56 STATISTIC(NumUnsafeStackRestorePointsFunctions,
57 "Number of functions that use setjmp or exceptions");
59 STATISTIC(NumAllocas, "Total number of allocas");
60 STATISTIC(NumUnsafeStaticAllocas, "Number of unsafe static allocas");
61 STATISTIC(NumUnsafeDynamicAllocas, "Number of unsafe dynamic allocas");
62 STATISTIC(NumUnsafeStackRestorePoints, "Number of setjmps and landingpads");
68 /// Check whether a given alloca instruction (AI) should be put on the safe
69 /// stack or not. The function analyzes all uses of AI and checks whether it is
70 /// only accessed in a memory safe way (as decided statically).
71 bool IsSafeStackAlloca(const AllocaInst *AI) {
72 // Go through all uses of this alloca and check whether all accesses to the
73 // allocated object are statically known to be memory safe and, hence, the
74 // object can be placed on the safe stack.
76 SmallPtrSet<const Value *, 16> Visited;
77 SmallVector<const Instruction *, 8> WorkList;
78 WorkList.push_back(AI);
80 // A DFS search through all uses of the alloca in bitcasts/PHI/GEPs/etc.
81 while (!WorkList.empty()) {
82 const Instruction *V = WorkList.pop_back_val();
83 for (const Use &UI : V->uses()) {
84 auto I = cast<const Instruction>(UI.getUser());
85 assert(V == UI.get());
87 switch (I->getOpcode()) {
88 case Instruction::Load:
89 // Loading from a pointer is safe.
91 case Instruction::VAArg:
92 // "va-arg" from a pointer is safe.
94 case Instruction::Store:
95 if (V == I->getOperand(0))
96 // Stored the pointer - conservatively assume it may be unsafe.
98 // Storing to the pointee is safe.
101 case Instruction::GetElementPtr:
102 if (!cast<const GetElementPtrInst>(I)->hasAllConstantIndices())
103 // GEP with non-constant indices can lead to memory errors.
104 // This also applies to inbounds GEPs, as the inbounds attribute
105 // represents an assumption that the address is in bounds, rather than
106 // an assertion that it is.
109 // We assume that GEP on static alloca with constant indices is safe,
110 // otherwise a compiler would detect it and warn during compilation.
112 if (!isa<const ConstantInt>(AI->getArraySize()))
113 // However, if the array size itself is not constant, the access
114 // might still be unsafe at runtime.
119 case Instruction::BitCast:
120 case Instruction::IntToPtr:
121 case Instruction::PHI:
122 case Instruction::PtrToInt:
123 case Instruction::Select:
124 // The object can be safe or not, depending on how the result of the
125 // instruction is used.
126 if (Visited.insert(I).second)
127 WorkList.push_back(cast<const Instruction>(I));
130 case Instruction::Call:
131 case Instruction::Invoke: {
132 // FIXME: add support for memset and memcpy intrinsics.
133 ImmutableCallSite CS(I);
135 // LLVM 'nocapture' attribute is only set for arguments whose address
136 // is not stored, passed around, or used in any other non-trivial way.
137 // We assume that passing a pointer to an object as a 'nocapture'
139 // FIXME: a more precise solution would require an interprocedural
140 // analysis here, which would look at all uses of an argument inside
141 // the function being called.
142 ImmutableCallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
143 for (ImmutableCallSite::arg_iterator A = B; A != E; ++A)
144 if (A->get() == V && !CS.doesNotCapture(A - B))
145 // The parameter is not marked 'nocapture' - unsafe.
151 // The object is unsafe if it is used in any other way.
157 // All uses of the alloca are safe, we can place it on the safe stack.
161 /// The SafeStack pass splits the stack of each function into the
162 /// safe stack, which is only accessed through memory safe dereferences
163 /// (as determined statically), and the unsafe stack, which contains all
164 /// local variables that are accessed in unsafe ways.
165 class SafeStack : public FunctionPass {
166 const TargetMachine *TM;
167 const TargetLoweringBase *TLI;
168 const DataLayout *DL;
175 Value *UnsafeStackPtr = nullptr;
177 /// Unsafe stack alignment. Each stack frame must ensure that the stack is
178 /// aligned to this value. We need to re-align the unsafe stack if the
179 /// alignment of any object on the stack exceeds this value.
181 /// 16 seems like a reasonable upper bound on the alignment of objects that we
182 /// might expect to appear on the stack on most common targets.
183 enum { StackAlignment = 16 };
185 /// \brief Build a constant representing a pointer to the unsafe stack
187 Value *getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F);
189 /// \brief Find all static allocas, dynamic allocas, return instructions and
190 /// stack restore points (exception unwind blocks and setjmp calls) in the
191 /// given function and append them to the respective vectors.
192 void findInsts(Function &F, SmallVectorImpl<AllocaInst *> &StaticAllocas,
193 SmallVectorImpl<AllocaInst *> &DynamicAllocas,
194 SmallVectorImpl<ReturnInst *> &Returns,
195 SmallVectorImpl<Instruction *> &StackRestorePoints);
197 /// \brief Allocate space for all static allocas in \p StaticAllocas,
198 /// replace allocas with pointers into the unsafe stack and generate code to
199 /// restore the stack pointer before all return instructions in \p Returns.
201 /// \returns A pointer to the top of the unsafe stack after all unsafe static
202 /// allocas are allocated.
203 Value *moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
204 ArrayRef<AllocaInst *> StaticAllocas,
205 ArrayRef<ReturnInst *> Returns);
207 /// \brief Generate code to restore the stack after all stack restore points
208 /// in \p StackRestorePoints.
210 /// \returns A local variable in which to maintain the dynamic top of the
211 /// unsafe stack if needed.
213 createStackRestorePoints(IRBuilder<> &IRB, Function &F,
214 ArrayRef<Instruction *> StackRestorePoints,
215 Value *StaticTop, bool NeedDynamicTop);
217 /// \brief Replace all allocas in \p DynamicAllocas with code to allocate
218 /// space dynamically on the unsafe stack and store the dynamic unsafe stack
219 /// top to \p DynamicTop if non-null.
220 void moveDynamicAllocasToUnsafeStack(Function &F, Value *UnsafeStackPtr,
221 AllocaInst *DynamicTop,
222 ArrayRef<AllocaInst *> DynamicAllocas);
225 static char ID; // Pass identification, replacement for typeid.
226 SafeStack(const TargetMachine *TM)
227 : FunctionPass(ID), TM(TM), TLI(nullptr), DL(nullptr) {
228 initializeSafeStackPass(*PassRegistry::getPassRegistry());
230 SafeStack() : SafeStack(nullptr) {}
232 void getAnalysisUsage(AnalysisUsage &AU) const override {
233 AU.addRequired<AAResultsWrapperPass>();
236 bool doInitialization(Module &M) override {
237 DL = &M.getDataLayout();
239 StackPtrTy = Type::getInt8PtrTy(M.getContext());
240 IntPtrTy = DL->getIntPtrType(M.getContext());
241 Int32Ty = Type::getInt32Ty(M.getContext());
242 Int8Ty = Type::getInt8Ty(M.getContext());
247 bool runOnFunction(Function &F) override;
248 }; // class SafeStack
250 Value *SafeStack::getOrCreateUnsafeStackPtr(IRBuilder<> &IRB, Function &F) {
251 Module &M = *F.getParent();
252 Triple TargetTriple(M.getTargetTriple());
255 unsigned AddressSpace;
256 // Check if the target keeps the unsafe stack pointer at a fixed offset.
257 if (TLI && TLI->getSafeStackPointerLocation(Offset, AddressSpace)) {
258 Constant *OffsetVal =
259 ConstantInt::get(Type::getInt32Ty(F.getContext()), Offset);
260 return ConstantExpr::getIntToPtr(OffsetVal,
261 StackPtrTy->getPointerTo(AddressSpace));
264 // Android provides a libc function that returns the stack pointer address.
265 if (TargetTriple.getEnvironment() == llvm::Triple::Android) {
266 Value *Fn = M.getOrInsertFunction(kUnsafeStackPtrAddrFn,
267 StackPtrTy->getPointerTo(0), nullptr);
268 return IRB.CreateCall(Fn);
270 // Otherwise, declare a thread-local variable with a magic name.
271 auto UnsafeStackPtr =
272 dyn_cast_or_null<GlobalVariable>(M.getNamedValue(kUnsafeStackPtrVar));
274 if (!UnsafeStackPtr) {
275 // The global variable is not defined yet, define it ourselves.
276 // We use the initial-exec TLS model because we do not support the
277 // variable living anywhere other than in the main executable.
278 UnsafeStackPtr = new GlobalVariable(
279 /*Module=*/M, /*Type=*/StackPtrTy,
280 /*isConstant=*/false, /*Linkage=*/GlobalValue::ExternalLinkage,
281 /*Initializer=*/0, /*Name=*/kUnsafeStackPtrVar,
282 /*InsertBefore=*/nullptr,
283 /*ThreadLocalMode=*/GlobalValue::InitialExecTLSModel);
285 // The variable exists, check its type and attributes.
286 if (UnsafeStackPtr->getValueType() != StackPtrTy) {
287 report_fatal_error(Twine(kUnsafeStackPtrVar) + " must have void* type");
290 if (!UnsafeStackPtr->isThreadLocal()) {
291 report_fatal_error(Twine(kUnsafeStackPtrVar) + " must be thread-local");
294 return UnsafeStackPtr;
298 void SafeStack::findInsts(Function &F,
299 SmallVectorImpl<AllocaInst *> &StaticAllocas,
300 SmallVectorImpl<AllocaInst *> &DynamicAllocas,
301 SmallVectorImpl<ReturnInst *> &Returns,
302 SmallVectorImpl<Instruction *> &StackRestorePoints) {
303 for (Instruction &I : instructions(&F)) {
304 if (auto AI = dyn_cast<AllocaInst>(&I)) {
307 if (IsSafeStackAlloca(AI))
310 if (AI->isStaticAlloca()) {
311 ++NumUnsafeStaticAllocas;
312 StaticAllocas.push_back(AI);
314 ++NumUnsafeDynamicAllocas;
315 DynamicAllocas.push_back(AI);
317 } else if (auto RI = dyn_cast<ReturnInst>(&I)) {
318 Returns.push_back(RI);
319 } else if (auto CI = dyn_cast<CallInst>(&I)) {
320 // setjmps require stack restore.
321 if (CI->getCalledFunction() && CI->canReturnTwice())
322 StackRestorePoints.push_back(CI);
323 } else if (auto LP = dyn_cast<LandingPadInst>(&I)) {
324 // Exception landing pads require stack restore.
325 StackRestorePoints.push_back(LP);
326 } else if (auto II = dyn_cast<IntrinsicInst>(&I)) {
327 if (II->getIntrinsicID() == Intrinsic::gcroot)
328 llvm::report_fatal_error(
329 "gcroot intrinsic not compatible with safestack attribute");
335 SafeStack::createStackRestorePoints(IRBuilder<> &IRB, Function &F,
336 ArrayRef<Instruction *> StackRestorePoints,
337 Value *StaticTop, bool NeedDynamicTop) {
338 if (StackRestorePoints.empty())
341 // We need the current value of the shadow stack pointer to restore
342 // after longjmp or exception catching.
344 // FIXME: On some platforms this could be handled by the longjmp/exception
347 AllocaInst *DynamicTop = nullptr;
349 // If we also have dynamic alloca's, the stack pointer value changes
350 // throughout the function. For now we store it in an alloca.
351 DynamicTop = IRB.CreateAlloca(StackPtrTy, /*ArraySize=*/nullptr,
352 "unsafe_stack_dynamic_ptr");
355 // We need the original unsafe stack pointer value, even if there are
356 // no unsafe static allocas.
357 StaticTop = IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr");
360 IRB.CreateStore(StaticTop, DynamicTop);
362 // Restore current stack pointer after longjmp/exception catch.
363 for (Instruction *I : StackRestorePoints) {
364 ++NumUnsafeStackRestorePoints;
366 IRB.SetInsertPoint(cast<Instruction>(I->getNextNode()));
367 Value *CurrentTop = DynamicTop ? IRB.CreateLoad(DynamicTop) : StaticTop;
368 IRB.CreateStore(CurrentTop, UnsafeStackPtr);
375 SafeStack::moveStaticAllocasToUnsafeStack(IRBuilder<> &IRB, Function &F,
376 ArrayRef<AllocaInst *> StaticAllocas,
377 ArrayRef<ReturnInst *> Returns) {
378 if (StaticAllocas.empty())
381 DIBuilder DIB(*F.getParent());
383 // We explicitly compute and set the unsafe stack layout for all unsafe
384 // static alloca instructions. We save the unsafe "base pointer" in the
385 // prologue into a local variable and restore it in the epilogue.
387 // Load the current stack pointer (we'll also use it as a base pointer).
388 // FIXME: use a dedicated register for it ?
389 Instruction *BasePointer =
390 IRB.CreateLoad(UnsafeStackPtr, false, "unsafe_stack_ptr");
391 assert(BasePointer->getType() == StackPtrTy);
393 for (ReturnInst *RI : Returns) {
394 IRB.SetInsertPoint(RI);
395 IRB.CreateStore(BasePointer, UnsafeStackPtr);
398 // Compute maximum alignment among static objects on the unsafe stack.
399 unsigned MaxAlignment = 0;
400 for (AllocaInst *AI : StaticAllocas) {
401 Type *Ty = AI->getAllocatedType();
403 std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI->getAlignment());
404 if (Align > MaxAlignment)
405 MaxAlignment = Align;
408 if (MaxAlignment > StackAlignment) {
409 // Re-align the base pointer according to the max requested alignment.
410 assert(isPowerOf2_32(MaxAlignment));
411 IRB.SetInsertPoint(cast<Instruction>(BasePointer->getNextNode()));
412 BasePointer = cast<Instruction>(IRB.CreateIntToPtr(
413 IRB.CreateAnd(IRB.CreatePtrToInt(BasePointer, IntPtrTy),
414 ConstantInt::get(IntPtrTy, ~uint64_t(MaxAlignment - 1))),
418 // Allocate space for every unsafe static AllocaInst on the unsafe stack.
419 int64_t StaticOffset = 0; // Current stack top.
420 for (AllocaInst *AI : StaticAllocas) {
421 IRB.SetInsertPoint(AI);
423 auto CArraySize = cast<ConstantInt>(AI->getArraySize());
424 Type *Ty = AI->getAllocatedType();
426 uint64_t Size = DL->getTypeAllocSize(Ty) * CArraySize->getZExtValue();
428 Size = 1; // Don't create zero-sized stack objects.
430 // Ensure the object is properly aligned.
432 std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI->getAlignment());
435 // NOTE: we ensure that BasePointer itself is aligned to >= Align.
436 StaticOffset += Size;
437 StaticOffset = RoundUpToAlignment(StaticOffset, Align);
439 Value *Off = IRB.CreateGEP(BasePointer, // BasePointer is i8*
440 ConstantInt::get(Int32Ty, -StaticOffset));
441 Value *NewAI = IRB.CreateBitCast(Off, AI->getType(), AI->getName());
442 if (AI->hasName() && isa<Instruction>(NewAI))
443 cast<Instruction>(NewAI)->takeName(AI);
445 // Replace alloc with the new location.
446 replaceDbgDeclareForAlloca(AI, NewAI, DIB, /*Deref=*/true);
447 AI->replaceAllUsesWith(NewAI);
448 AI->eraseFromParent();
451 // Re-align BasePointer so that our callees would see it aligned as
453 // FIXME: no need to update BasePointer in leaf functions.
454 StaticOffset = RoundUpToAlignment(StaticOffset, StackAlignment);
456 // Update shadow stack pointer in the function epilogue.
457 IRB.SetInsertPoint(cast<Instruction>(BasePointer->getNextNode()));
460 IRB.CreateGEP(BasePointer, ConstantInt::get(Int32Ty, -StaticOffset),
461 "unsafe_stack_static_top");
462 IRB.CreateStore(StaticTop, UnsafeStackPtr);
466 void SafeStack::moveDynamicAllocasToUnsafeStack(
467 Function &F, Value *UnsafeStackPtr, AllocaInst *DynamicTop,
468 ArrayRef<AllocaInst *> DynamicAllocas) {
469 DIBuilder DIB(*F.getParent());
471 for (AllocaInst *AI : DynamicAllocas) {
474 // Compute the new SP value (after AI).
475 Value *ArraySize = AI->getArraySize();
476 if (ArraySize->getType() != IntPtrTy)
477 ArraySize = IRB.CreateIntCast(ArraySize, IntPtrTy, false);
479 Type *Ty = AI->getAllocatedType();
480 uint64_t TySize = DL->getTypeAllocSize(Ty);
481 Value *Size = IRB.CreateMul(ArraySize, ConstantInt::get(IntPtrTy, TySize));
483 Value *SP = IRB.CreatePtrToInt(IRB.CreateLoad(UnsafeStackPtr), IntPtrTy);
484 SP = IRB.CreateSub(SP, Size);
486 // Align the SP value to satisfy the AllocaInst, type and stack alignments.
487 unsigned Align = std::max(
488 std::max((unsigned)DL->getPrefTypeAlignment(Ty), AI->getAlignment()),
489 (unsigned)StackAlignment);
491 assert(isPowerOf2_32(Align));
492 Value *NewTop = IRB.CreateIntToPtr(
493 IRB.CreateAnd(SP, ConstantInt::get(IntPtrTy, ~uint64_t(Align - 1))),
496 // Save the stack pointer.
497 IRB.CreateStore(NewTop, UnsafeStackPtr);
499 IRB.CreateStore(NewTop, DynamicTop);
501 Value *NewAI = IRB.CreateIntToPtr(SP, AI->getType());
502 if (AI->hasName() && isa<Instruction>(NewAI))
505 replaceDbgDeclareForAlloca(AI, NewAI, DIB, /*Deref=*/true);
506 AI->replaceAllUsesWith(NewAI);
507 AI->eraseFromParent();
510 if (!DynamicAllocas.empty()) {
511 // Now go through the instructions again, replacing stacksave/stackrestore.
512 for (inst_iterator It = inst_begin(&F), Ie = inst_end(&F); It != Ie;) {
513 Instruction *I = &*(It++);
514 auto II = dyn_cast<IntrinsicInst>(I);
518 if (II->getIntrinsicID() == Intrinsic::stacksave) {
520 Instruction *LI = IRB.CreateLoad(UnsafeStackPtr);
522 II->replaceAllUsesWith(LI);
523 II->eraseFromParent();
524 } else if (II->getIntrinsicID() == Intrinsic::stackrestore) {
526 Instruction *SI = IRB.CreateStore(II->getArgOperand(0), UnsafeStackPtr);
528 assert(II->use_empty());
529 II->eraseFromParent();
535 bool SafeStack::runOnFunction(Function &F) {
536 DEBUG(dbgs() << "[SafeStack] Function: " << F.getName() << "\n");
538 if (!F.hasFnAttribute(Attribute::SafeStack)) {
539 DEBUG(dbgs() << "[SafeStack] safestack is not requested"
540 " for this function\n");
544 if (F.isDeclaration()) {
545 DEBUG(dbgs() << "[SafeStack] function definition"
546 " is not available\n");
550 auto AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
552 TLI = TM ? TM->getSubtargetImpl(F)->getTargetLowering() : nullptr;
555 // Make sure the regular stack protector won't run on this function
556 // (safestack attribute takes precedence).
558 B.addAttribute(Attribute::StackProtect)
559 .addAttribute(Attribute::StackProtectReq)
560 .addAttribute(Attribute::StackProtectStrong);
562 AttributeSet::FunctionIndex,
563 AttributeSet::get(F.getContext(), AttributeSet::FunctionIndex, B));
566 if (AA->onlyReadsMemory(&F)) {
567 // XXX: we don't protect against information leak attacks for now.
568 DEBUG(dbgs() << "[SafeStack] function only reads memory\n");
574 SmallVector<AllocaInst *, 16> StaticAllocas;
575 SmallVector<AllocaInst *, 4> DynamicAllocas;
576 SmallVector<ReturnInst *, 4> Returns;
578 // Collect all points where stack gets unwound and needs to be restored
579 // This is only necessary because the runtime (setjmp and unwind code) is
580 // not aware of the unsafe stack and won't unwind/restore it prorerly.
581 // To work around this problem without changing the runtime, we insert
582 // instrumentation to restore the unsafe stack pointer when necessary.
583 SmallVector<Instruction *, 4> StackRestorePoints;
585 // Find all static and dynamic alloca instructions that must be moved to the
586 // unsafe stack, all return instructions and stack restore points.
587 findInsts(F, StaticAllocas, DynamicAllocas, Returns, StackRestorePoints);
589 if (StaticAllocas.empty() && DynamicAllocas.empty() &&
590 StackRestorePoints.empty())
591 return false; // Nothing to do in this function.
593 if (!StaticAllocas.empty() || !DynamicAllocas.empty())
594 ++NumUnsafeStackFunctions; // This function has the unsafe stack.
596 if (!StackRestorePoints.empty())
597 ++NumUnsafeStackRestorePointsFunctions;
599 IRBuilder<> IRB(F.begin()->getFirstInsertionPt());
600 UnsafeStackPtr = getOrCreateUnsafeStackPtr(IRB, F);
602 // The top of the unsafe stack after all unsafe static allocas are allocated.
603 Value *StaticTop = moveStaticAllocasToUnsafeStack(IRB, F, StaticAllocas, Returns);
605 // Safe stack object that stores the current unsafe stack top. It is updated
606 // as unsafe dynamic (non-constant-sized) allocas are allocated and freed.
607 // This is only needed if we need to restore stack pointer after longjmp
608 // or exceptions, and we have dynamic allocations.
609 // FIXME: a better alternative might be to store the unsafe stack pointer
610 // before setjmp / invoke instructions.
611 AllocaInst *DynamicTop = createStackRestorePoints(
612 IRB, F, StackRestorePoints, StaticTop, !DynamicAllocas.empty());
614 // Handle dynamic allocas.
615 moveDynamicAllocasToUnsafeStack(F, UnsafeStackPtr, DynamicTop,
618 DEBUG(dbgs() << "[SafeStack] safestack applied\n");
622 } // end anonymous namespace
624 char SafeStack::ID = 0;
625 INITIALIZE_TM_PASS_BEGIN(SafeStack, "safe-stack",
626 "Safe Stack instrumentation pass", false, false)
627 INITIALIZE_TM_PASS_END(SafeStack, "safe-stack",
628 "Safe Stack instrumentation pass", false, false)
630 FunctionPass *llvm::createSafeStackPass(const llvm::TargetMachine *TM) {
631 return new SafeStack(TM);