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📄 AggressiveAntiDepBreaker.cpp(37.23 KB)
📄 AggressiveAntiDepBreaker.h(6.8 KB)
📄 AllocationOrder.cpp(1.96 KB)
📄 AllocationOrder.h(2.96 KB)
📄 Analysis.cpp(32.62 KB)
📁 AsmPrinter
📄 AtomicExpandPass.cpp(71.86 KB)
📄 BBSectionsPrepare.cpp(18.8 KB)
📄 BasicTargetTransformInfo.cpp(1.53 KB)
📄 BranchFolding.cpp(77.92 KB)
📄 BranchFolding.h(7.36 KB)
📄 BranchRelaxation.cpp(19.45 KB)
📄 BreakFalseDeps.cpp(9.79 KB)
📄 BuiltinGCs.cpp(4.88 KB)
📄 CFGuardLongjmp.cpp(3.73 KB)
📄 CFIInstrInserter.cpp(17.53 KB)
📄 CalcSpillWeights.cpp(10.22 KB)
📄 CallingConvLower.cpp(10.4 KB)
📄 CodeGen.cpp(5.28 KB)
📄 CodeGenPrepare.cpp(295.01 KB)
📄 CommandFlags.cpp(24.89 KB)
📄 CriticalAntiDepBreaker.cpp(27.91 KB)
📄 CriticalAntiDepBreaker.h(4.22 KB)
📄 DFAPacketizer.cpp(10.91 KB)
📄 DeadMachineInstructionElim.cpp(6.52 KB)
📄 DetectDeadLanes.cpp(20.74 KB)
📄 DwarfEHPrepare.cpp(9.01 KB)
📄 EarlyIfConversion.cpp(37.51 KB)
📄 EdgeBundles.cpp(3.21 KB)
📄 ExecutionDomainFix.cpp(14.67 KB)
📄 ExpandMemCmp.cpp(33.66 KB)
📄 ExpandPostRAPseudos.cpp(7.28 KB)
📄 ExpandReductions.cpp(7.23 KB)
📄 FEntryInserter.cpp(1.81 KB)
📄 FaultMaps.cpp(4.99 KB)
📄 FinalizeISel.cpp(2.65 KB)
📄 FixupStatepointCallerSaved.cpp(11.06 KB)
📄 FuncletLayout.cpp(2.21 KB)
📄 GCMetadata.cpp(5.1 KB)
📄 GCMetadataPrinter.cpp(748 B)
📄 GCRootLowering.cpp(11.46 KB)
📄 GCStrategy.cpp(708 B)
📁 GlobalISel
📄 GlobalMerge.cpp(24.52 KB)
📄 HardwareLoops.cpp(18.44 KB)
📄 IfConversion.cpp(89.43 KB)
📄 ImplicitNullChecks.cpp(25.14 KB)
📄 IndirectBrExpandPass.cpp(7.79 KB)
📄 InlineSpiller.cpp(58.24 KB)
📄 InterferenceCache.cpp(8.83 KB)
📄 InterferenceCache.h(7.22 KB)
📄 InterleavedAccessPass.cpp(16.59 KB)
📄 InterleavedLoadCombinePass.cpp(42.35 KB)
📄 IntrinsicLowering.cpp(17.08 KB)
📄 LLVMTargetMachine.cpp(10.25 KB)
📄 LatencyPriorityQueue.cpp(5.64 KB)
📄 LazyMachineBlockFrequencyInfo.cpp(3.36 KB)
📄 LexicalScopes.cpp(12.16 KB)
📄 LiveDebugValues.cpp(78.98 KB)
📄 LiveDebugVariables.cpp(51.79 KB)
📄 LiveDebugVariables.h(2.15 KB)
📄 LiveInterval.cpp(46.67 KB)
📄 LiveIntervalCalc.cpp(7.62 KB)
📄 LiveIntervalUnion.cpp(6.36 KB)
📄 LiveIntervals.cpp(64.59 KB)
📄 LivePhysRegs.cpp(11.08 KB)
📄 LiveRangeCalc.cpp(15.72 KB)
📄 LiveRangeEdit.cpp(17.03 KB)
📄 LiveRangeShrink.cpp(8.69 KB)
📄 LiveRangeUtils.h(2.12 KB)
📄 LiveRegMatrix.cpp(7.47 KB)
📄 LiveRegUnits.cpp(4.72 KB)
📄 LiveStacks.cpp(2.95 KB)
📄 LiveVariables.cpp(30.26 KB)
📄 LocalStackSlotAllocation.cpp(17.26 KB)
📄 LoopTraversal.cpp(2.89 KB)
📄 LowLevelType.cpp(1.93 KB)
📄 LowerEmuTLS.cpp(5.66 KB)
📄 MBFIWrapper.cpp(1.57 KB)
📄 MIRCanonicalizerPass.cpp(12.46 KB)
📄 MIRNamerPass.cpp(2.16 KB)
📁 MIRParser
📄 MIRPrinter.cpp(32.67 KB)
📄 MIRPrintingPass.cpp(1.99 KB)
📄 MIRVRegNamerUtils.cpp(6.04 KB)
📄 MIRVRegNamerUtils.h(3.25 KB)
📄 MachineBasicBlock.cpp(50.47 KB)
📄 MachineBlockFrequencyInfo.cpp(10.13 KB)
📄 MachineBlockPlacement.cpp(137.61 KB)
📄 MachineBranchProbabilityInfo.cpp(3.5 KB)
📄 MachineCSE.cpp(31.82 KB)
📄 MachineCombiner.cpp(28.13 KB)
📄 MachineCopyPropagation.cpp(29.21 KB)
📄 MachineDebugify.cpp(6.47 KB)
📄 MachineDominanceFrontier.cpp(1.83 KB)
📄 MachineDominators.cpp(4.86 KB)
📄 MachineFrameInfo.cpp(9.77 KB)
📄 MachineFunction.cpp(42.97 KB)
📄 MachineFunctionPass.cpp(4.78 KB)
📄 MachineFunctionPrinterPass.cpp(2.3 KB)
📄 MachineInstr.cpp(76.39 KB)
📄 MachineInstrBundle.cpp(11.49 KB)
📄 MachineLICM.cpp(57.05 KB)
📄 MachineLoopInfo.cpp(4.98 KB)
📄 MachineLoopUtils.cpp(5.16 KB)
📄 MachineModuleInfo.cpp(9.9 KB)
📄 MachineModuleInfoImpls.cpp(1.5 KB)
📄 MachineOperand.cpp(39.6 KB)
📄 MachineOptimizationRemarkEmitter.cpp(3.29 KB)
📄 MachineOutliner.cpp(42.13 KB)
📄 MachinePipeliner.cpp(111.33 KB)
📄 MachinePostDominators.cpp(2.42 KB)
📄 MachineRegionInfo.cpp(4.75 KB)
📄 MachineRegisterInfo.cpp(22.97 KB)
📄 MachineSSAUpdater.cpp(12.99 KB)
📄 MachineScheduler.cpp(136.89 KB)
📄 MachineSink.cpp(51.94 KB)
📄 MachineSizeOpts.cpp(8.76 KB)
📄 MachineStripDebug.cpp(3.76 KB)
📄 MachineTraceMetrics.cpp(49.58 KB)
📄 MachineVerifier.cpp(107.98 KB)
📄 MacroFusion.cpp(7.55 KB)
📄 ModuloSchedule.cpp(85.09 KB)
📄 NonRelocatableStringpool.cpp(1.65 KB)
📄 OptimizePHIs.cpp(6.7 KB)
📄 PHIElimination.cpp(27.73 KB)
📄 PHIEliminationUtils.cpp(2.56 KB)
📄 PHIEliminationUtils.h(972 B)
📄 ParallelCG.cpp(3.71 KB)
📄 PatchableFunction.cpp(3.44 KB)
📄 PeepholeOptimizer.cpp(78.41 KB)
📄 PostRAHazardRecognizer.cpp(3.5 KB)
📄 PostRASchedulerList.cpp(24.31 KB)
📄 PreISelIntrinsicLowering.cpp(7.91 KB)
📄 ProcessImplicitDefs.cpp(5.4 KB)
📄 PrologEpilogInserter.cpp(50.45 KB)
📄 PseudoSourceValue.cpp(4.71 KB)
📄 RDFGraph.cpp(58.39 KB)
📄 RDFLiveness.cpp(40.7 KB)
📄 RDFRegisters.cpp(11.29 KB)
📄 ReachingDefAnalysis.cpp(21.74 KB)
📄 RegAllocBase.cpp(6.31 KB)
📄 RegAllocBase.h(4.63 KB)
📄 RegAllocBasic.cpp(11.33 KB)
📄 RegAllocFast.cpp(45.78 KB)
📄 RegAllocGreedy.cpp(123.32 KB)
📄 RegAllocPBQP.cpp(33.14 KB)
📄 RegUsageInfoCollector.cpp(7.39 KB)
📄 RegUsageInfoPropagate.cpp(5.07 KB)
📄 RegisterClassInfo.cpp(6.62 KB)
📄 RegisterCoalescer.cpp(151.71 KB)
📄 RegisterCoalescer.h(4.04 KB)
📄 RegisterPressure.cpp(48.86 KB)
📄 RegisterScavenging.cpp(27.48 KB)
📄 RegisterUsageInfo.cpp(3.18 KB)
📄 RenameIndependentSubregs.cpp(14.79 KB)
📄 ResetMachineFunctionPass.cpp(3.48 KB)
📄 SafeStack.cpp(34.12 KB)
📄 SafeStackLayout.cpp(5.3 KB)
📄 SafeStackLayout.h(2.41 KB)
📄 ScalarizeMaskedMemIntrin.cpp(31.46 KB)
📄 ScheduleDAG.cpp(21.34 KB)
📄 ScheduleDAGInstrs.cpp(54.59 KB)
📄 ScheduleDAGPrinter.cpp(3.21 KB)
📄 ScoreboardHazardRecognizer.cpp(7.96 KB)
📁 SelectionDAG
📄 ShadowStackGCLowering.cpp(14.16 KB)
📄 ShrinkWrap.cpp(23.03 KB)
📄 SjLjEHPrepare.cpp(18.93 KB)
📄 SlotIndexes.cpp(9.35 KB)
📄 SpillPlacement.cpp(12.58 KB)
📄 SpillPlacement.h(6.67 KB)
📄 SplitKit.cpp(66.39 KB)
📄 SplitKit.h(23.7 KB)
📄 StackColoring.cpp(49.03 KB)
📄 StackMapLivenessAnalysis.cpp(6.16 KB)
📄 StackMaps.cpp(19.74 KB)
📄 StackProtector.cpp(22.94 KB)
📄 StackSlotColoring.cpp(17.12 KB)
📄 SwiftErrorValueTracking.cpp(11.37 KB)
📄 SwitchLoweringUtils.cpp(18.33 KB)
📄 TailDuplication.cpp(3.32 KB)
📄 TailDuplicator.cpp(38.29 KB)
📄 TargetFrameLoweringImpl.cpp(6.24 KB)
📄 TargetInstrInfo.cpp(51.1 KB)
📄 TargetLoweringBase.cpp(82.53 KB)
📄 TargetLoweringObjectFileImpl.cpp(80.52 KB)
📄 TargetOptionsImpl.cpp(2 KB)
📄 TargetPassConfig.cpp(48.89 KB)
📄 TargetRegisterInfo.cpp(19.15 KB)
📄 TargetSchedule.cpp(13.16 KB)
📄 TargetSubtargetInfo.cpp(1.89 KB)
📄 TwoAddressInstructionPass.cpp(62.08 KB)
📄 TypePromotion.cpp(32.46 KB)
📄 UnreachableBlockElim.cpp(7.48 KB)
📄 ValueTypes.cpp(19.87 KB)
📄 VirtRegMap.cpp(21.4 KB)
📄 WasmEHPrepare.cpp(17.48 KB)
📄 WinEHPrepare.cpp(51.16 KB)
📄 XRayInstrumentation.cpp(9.66 KB)

Editing: StackProtector.cpp

//===- StackProtector.cpp - Stack Protector Insertion ---------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass inserts stack protectors into functions which need them. A variable
// with a random value in it is stored onto the stack before the local variables
// are allocated. Upon exiting the block, the stored value is checked. If it's
// changed, then there was some sort of violation and the program aborts.
//
//===----------------------------------------------------------------------===//

#include "llvm/CodeGen/StackProtector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <utility>

using namespace llvm;

#define DEBUG_TYPE "stack-protector"

STATISTIC(NumFunProtected, "Number of functions protected");
STATISTIC(NumAddrTaken, "Number of local variables that have their address"
                        " taken.");

static cl::opt<bool> EnableSelectionDAGSP("enable-selectiondag-sp",
                                          cl::init(true), cl::Hidden);

char StackProtector::ID = 0;

StackProtector::StackProtector() : FunctionPass(ID), SSPBufferSize(8) {
  initializeStackProtectorPass(*PassRegistry::getPassRegistry());
}

INITIALIZE_PASS_BEGIN(StackProtector, DEBUG_TYPE,
                      "Insert stack protectors", false, true)
INITIALIZE_PASS_DEPENDENCY(TargetPassConfig)
INITIALIZE_PASS_END(StackProtector, DEBUG_TYPE,
                    "Insert stack protectors", false, true)

FunctionPass *llvm::createStackProtectorPass() { return new StackProtector(); }

void StackProtector::getAnalysisUsage(AnalysisUsage &AU) const {
  AU.addRequired<TargetPassConfig>();
  AU.addPreserved<DominatorTreeWrapperPass>();
}

bool StackProtector::runOnFunction(Function &Fn) {
  F = &Fn;
  M = F->getParent();
  DominatorTreeWrapperPass *DTWP =
      getAnalysisIfAvailable<DominatorTreeWrapperPass>();
  DT = DTWP ? &DTWP->getDomTree() : nullptr;
  TM = &getAnalysis<TargetPassConfig>().getTM<TargetMachine>();
  Trip = TM->getTargetTriple();
  TLI = TM->getSubtargetImpl(Fn)->getTargetLowering();
  HasPrologue = false;
  HasIRCheck = false;

Attribute Attr = Fn.getFnAttribute("stack-protector-buffer-size");
  if (Attr.isStringAttribute() &&
      Attr.getValueAsString().getAsInteger(10, SSPBufferSize))
    return false; // Invalid integer string

if (!RequiresStackProtector())
    return false;

// TODO(etienneb): Functions with funclets are not correctly supported now.
  // Do nothing if this is funclet-based personality.
  if (Fn.hasPersonalityFn()) {
    EHPersonality Personality = classifyEHPersonality(Fn.getPersonalityFn());
    if (isFuncletEHPersonality(Personality))
      return false;
  }

++NumFunProtected;
  return InsertStackProtectors();
}

/// \param [out] IsLarge is set to true if a protectable array is found and
/// it is "large" ( >= ssp-buffer-size).  In the case of a structure with
/// multiple arrays, this gets set if any of them is large.
bool StackProtector::ContainsProtectableArray(Type *Ty, bool &IsLarge,
                                              bool Strong,
                                              bool InStruct) const {
  if (!Ty)
    return false;
  if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
    if (!AT->getElementType()->isIntegerTy(8)) {
      // If we're on a non-Darwin platform or we're inside of a structure, don't
      // add stack protectors unless the array is a character array.
      // However, in strong mode any array, regardless of type and size,
      // triggers a protector.
      if (!Strong && (InStruct || !Trip.isOSDarwin()))
        return false;
    }

// If an array has more than SSPBufferSize bytes of allocated space, then we
    // emit stack protectors.
    if (SSPBufferSize <= M->getDataLayout().getTypeAllocSize(AT)) {
      IsLarge = true;
      return true;
    }

if (Strong)
      // Require a protector for all arrays in strong mode
      return true;
  }

const StructType *ST = dyn_cast<StructType>(Ty);
  if (!ST)
    return false;

bool NeedsProtector = false;
  for (StructType::element_iterator I = ST->element_begin(),
                                    E = ST->element_end();
       I != E; ++I)
    if (ContainsProtectableArray(*I, IsLarge, Strong, true)) {
      // If the element is a protectable array and is large (>= SSPBufferSize)
      // then we are done.  If the protectable array is not large, then
      // keep looking in case a subsequent element is a large array.
      if (IsLarge)
        return true;
      NeedsProtector = true;
    }

return NeedsProtector;
}

bool StackProtector::HasAddressTaken(const Instruction *AI,
                                     uint64_t AllocSize) {
  const DataLayout &DL = M->getDataLayout();
  for (const User *U : AI->users()) {
    const auto *I = cast<Instruction>(U);
    // If this instruction accesses memory make sure it doesn't access beyond
    // the bounds of the allocated object.
    Optional<MemoryLocation> MemLoc = MemoryLocation::getOrNone(I);
    if (MemLoc.hasValue() && MemLoc->Size.getValue() > AllocSize)
      return true;
    switch (I->getOpcode()) {
    case Instruction::Store:
      if (AI == cast<StoreInst>(I)->getValueOperand())
        return true;
      break;
    case Instruction::AtomicCmpXchg:
      // cmpxchg conceptually includes both a load and store from the same
      // location. So, like store, the value being stored is what matters.
      if (AI == cast<AtomicCmpXchgInst>(I)->getNewValOperand())
        return true;
      break;
    case Instruction::PtrToInt:
      if (AI == cast<PtrToIntInst>(I)->getOperand(0))
        return true;
      break;
    case Instruction::Call: {
      // Ignore intrinsics that do not become real instructions.
      // TODO: Narrow this to intrinsics that have store-like effects.
      const auto *CI = cast<CallInst>(I);
      if (!isa<DbgInfoIntrinsic>(CI) && !CI->isLifetimeStartOrEnd())
        return true;
      break;
    }
    case Instruction::Invoke:
      return true;
    case Instruction::GetElementPtr: {
      // If the GEP offset is out-of-bounds, or is non-constant and so has to be
      // assumed to be potentially out-of-bounds, then any memory access that
      // would use it could also be out-of-bounds meaning stack protection is
      // required.
      const GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
      unsigned TypeSize = DL.getIndexTypeSizeInBits(I->getType());
      APInt Offset(TypeSize, 0);
      APInt MaxOffset(TypeSize, AllocSize);
      if (!GEP->accumulateConstantOffset(DL, Offset) || Offset.ugt(MaxOffset))
        return true;
      // Adjust AllocSize to be the space remaining after this offset.
      if (HasAddressTaken(I, AllocSize - Offset.getLimitedValue()))
        return true;
      break;
    }
    case Instruction::BitCast:
    case Instruction::Select:
    case Instruction::AddrSpaceCast:
      if (HasAddressTaken(I, AllocSize))
        return true;
      break;
    case Instruction::PHI: {
      // Keep track of what PHI nodes we have already visited to ensure
      // they are only visited once.
      const auto *PN = cast<PHINode>(I);
      if (VisitedPHIs.insert(PN).second)
        if (HasAddressTaken(PN, AllocSize))
          return true;
      break;
    }
    case Instruction::Load:
    case Instruction::AtomicRMW:
    case Instruction::Ret:
      // These instructions take an address operand, but have load-like or
      // other innocuous behavior that should not trigger a stack protector.
      // atomicrmw conceptually has both load and store semantics, but the
      // value being stored must be integer; so if a pointer is being stored,
      // we'll catch it in the PtrToInt case above.
      break;
    default:
      // Conservatively return true for any instruction that takes an address
      // operand, but is not handled above.
      return true;
    }
  }
  return false;
}

/// Search for the first call to the llvm.stackprotector intrinsic and return it
/// if present.
static const CallInst *findStackProtectorIntrinsic(Function &F) {
  for (const BasicBlock &BB : F)
    for (const Instruction &I : BB)
      if (const CallInst *CI = dyn_cast<CallInst>(&I))
        if (CI->getCalledFunction() ==
            Intrinsic::getDeclaration(F.getParent(), Intrinsic::stackprotector))
          return CI;
  return nullptr;
}

/// Check whether or not this function needs a stack protector based
/// upon the stack protector level.
///
/// We use two heuristics: a standard (ssp) and strong (sspstrong).
/// The standard heuristic which will add a guard variable to functions that
/// call alloca with a either a variable size or a size >= SSPBufferSize,
/// functions with character buffers larger than SSPBufferSize, and functions
/// with aggregates containing character buffers larger than SSPBufferSize. The
/// strong heuristic will add a guard variables to functions that call alloca
/// regardless of size, functions with any buffer regardless of type and size,
/// functions with aggregates that contain any buffer regardless of type and
/// size, and functions that contain stack-based variables that have had their
/// address taken.
bool StackProtector::RequiresStackProtector() {
  bool Strong = false;
  bool NeedsProtector = false;
  HasPrologue = findStackProtectorIntrinsic(*F);

if (F->hasFnAttribute(Attribute::SafeStack))
    return false;

// We are constructing the OptimizationRemarkEmitter on the fly rather than
  // using the analysis pass to avoid building DominatorTree and LoopInfo which
  // are not available this late in the IR pipeline.
  OptimizationRemarkEmitter ORE(F);

if (F->hasFnAttribute(Attribute::StackProtectReq)) {
    ORE.emit([&]() {
      return OptimizationRemark(DEBUG_TYPE, "StackProtectorRequested", F)
             << "Stack protection applied to function "
             << ore::NV("Function", F)
             << " due to a function attribute or command-line switch";
    });
    NeedsProtector = true;
    Strong = true; // Use the same heuristic as strong to determine SSPLayout
  } else if (F->hasFnAttribute(Attribute::StackProtectStrong))
    Strong = true;
  else if (HasPrologue)
    NeedsProtector = true;
  else if (!F->hasFnAttribute(Attribute::StackProtect))
    return false;

for (const BasicBlock &BB : *F) {
    for (const Instruction &I : BB) {
      if (const AllocaInst *AI = dyn_cast<AllocaInst>(&I)) {
        if (AI->isArrayAllocation()) {
          auto RemarkBuilder = [&]() {
            return OptimizationRemark(DEBUG_TYPE, "StackProtectorAllocaOrArray",
                                      &I)
                   << "Stack protection applied to function "
                   << ore::NV("Function", F)
                   << " due to a call to alloca or use of a variable length "
                      "array";
          };
          if (const auto *CI = dyn_cast<ConstantInt>(AI->getArraySize())) {
            if (CI->getLimitedValue(SSPBufferSize) >= SSPBufferSize) {
              // A call to alloca with size >= SSPBufferSize requires
              // stack protectors.
              Layout.insert(std::make_pair(AI,
                                           MachineFrameInfo::SSPLK_LargeArray));
              ORE.emit(RemarkBuilder);
              NeedsProtector = true;
            } else if (Strong) {
              // Require protectors for all alloca calls in strong mode.
              Layout.insert(std::make_pair(AI,
                                           MachineFrameInfo::SSPLK_SmallArray));
              ORE.emit(RemarkBuilder);
              NeedsProtector = true;
            }
          } else {
            // A call to alloca with a variable size requires protectors.
            Layout.insert(std::make_pair(AI,
                                         MachineFrameInfo::SSPLK_LargeArray));
            ORE.emit(RemarkBuilder);
            NeedsProtector = true;
          }
          continue;
        }

bool IsLarge = false;
        if (ContainsProtectableArray(AI->getAllocatedType(), IsLarge, Strong)) {
          Layout.insert(std::make_pair(AI, IsLarge
                                       ? MachineFrameInfo::SSPLK_LargeArray
                                       : MachineFrameInfo::SSPLK_SmallArray));
          ORE.emit([&]() {
            return OptimizationRemark(DEBUG_TYPE, "StackProtectorBuffer", &I)
                   << "Stack protection applied to function "
                   << ore::NV("Function", F)
                   << " due to a stack allocated buffer or struct containing a "
                      "buffer";
          });
          NeedsProtector = true;
          continue;
        }

if (Strong && HasAddressTaken(AI, M->getDataLayout().getTypeAllocSize(
                                              AI->getAllocatedType()))) {
          ++NumAddrTaken;
          Layout.insert(std::make_pair(AI, MachineFrameInfo::SSPLK_AddrOf));
          ORE.emit([&]() {
            return OptimizationRemark(DEBUG_TYPE, "StackProtectorAddressTaken",
                                      &I)
                   << "Stack protection applied to function "
                   << ore::NV("Function", F)
                   << " due to the address of a local variable being taken";
          });
          NeedsProtector = true;
        }
        // Clear any PHIs that we visited, to make sure we examine all uses of
        // any subsequent allocas that we look at.
        VisitedPHIs.clear();
      }
    }
  }

return NeedsProtector;
}

/// Create a stack guard loading and populate whether SelectionDAG SSP is
/// supported.
static Value *getStackGuard(const TargetLoweringBase *TLI, Module *M,
                            IRBuilder<> &B,
                            bool *SupportsSelectionDAGSP = nullptr) {
  if (Value *Guard = TLI->getIRStackGuard(B))
    return B.CreateLoad(B.getInt8PtrTy(), Guard, true, "StackGuard");

// Use SelectionDAG SSP handling, since there isn't an IR guard.
  //
  // This is more or less weird, since we optionally output whether we
  // should perform a SelectionDAG SP here. The reason is that it's strictly
  // defined as !TLI->getIRStackGuard(B), where getIRStackGuard is also
  // mutating. There is no way to get this bit without mutating the IR, so
  // getting this bit has to happen in this right time.
  //
  // We could have define a new function TLI::supportsSelectionDAGSP(), but that
  // will put more burden on the backends' overriding work, especially when it
  // actually conveys the same information getIRStackGuard() already gives.
  if (SupportsSelectionDAGSP)
    *SupportsSelectionDAGSP = true;
  TLI->insertSSPDeclarations(*M);
  return B.CreateCall(Intrinsic::getDeclaration(M, Intrinsic::stackguard));
}

/// Insert code into the entry block that stores the stack guard
/// variable onto the stack:
///
///   entry:
///     StackGuardSlot = alloca i8*
///     StackGuard = <stack guard>
///     call void @llvm.stackprotector(StackGuard, StackGuardSlot)
///
/// Returns true if the platform/triple supports the stackprotectorcreate pseudo
/// node.
static bool CreatePrologue(Function *F, Module *M, ReturnInst *RI,
                           const TargetLoweringBase *TLI, AllocaInst *&AI) {
  bool SupportsSelectionDAGSP = false;
  IRBuilder<> B(&F->getEntryBlock().front());
  PointerType *PtrTy = Type::getInt8PtrTy(RI->getContext());
  AI = B.CreateAlloca(PtrTy, nullptr, "StackGuardSlot");

Value *GuardSlot = getStackGuard(TLI, M, B, &SupportsSelectionDAGSP);
  B.CreateCall(Intrinsic::getDeclaration(M, Intrinsic::stackprotector),
               {GuardSlot, AI});
  return SupportsSelectionDAGSP;
}

/// InsertStackProtectors - Insert code into the prologue and epilogue of the
/// function.
///
///  - The prologue code loads and stores the stack guard onto the stack.
///  - The epilogue checks the value stored in the prologue against the original
///    value. It calls __stack_chk_fail if they differ.
bool StackProtector::InsertStackProtectors() {
  // If the target wants to XOR the frame pointer into the guard value, it's
  // impossible to emit the check in IR, so the target *must* support stack
  // protection in SDAG.
  bool SupportsSelectionDAGSP =
      TLI->useStackGuardXorFP() ||
      (EnableSelectionDAGSP && !TM->Options.EnableFastISel &&
       !TM->Options.EnableGlobalISel);
  AllocaInst *AI = nullptr;       // Place on stack that stores the stack guard.

for (Function::iterator I = F->begin(), E = F->end(); I != E;) {
    BasicBlock *BB = &*I++;
    ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
    if (!RI)
      continue;

// Generate prologue instrumentation if not already generated.
    if (!HasPrologue) {
      HasPrologue = true;
      SupportsSelectionDAGSP &= CreatePrologue(F, M, RI, TLI, AI);
    }

// SelectionDAG based code generation. Nothing else needs to be done here.
    // The epilogue instrumentation is postponed to SelectionDAG.
    if (SupportsSelectionDAGSP)
      break;

// Find the stack guard slot if the prologue was not created by this pass
    // itself via a previous call to CreatePrologue().
    if (!AI) {
      const CallInst *SPCall = findStackProtectorIntrinsic(*F);
      assert(SPCall && "Call to llvm.stackprotector is missing");
      AI = cast<AllocaInst>(SPCall->getArgOperand(1));
    }

// Set HasIRCheck to true, so that SelectionDAG will not generate its own
    // version. SelectionDAG called 'shouldEmitSDCheck' to check whether
    // instrumentation has already been generated.
    HasIRCheck = true;

// Generate epilogue instrumentation. The epilogue intrumentation can be
    // function-based or inlined depending on which mechanism the target is
    // providing.
    if (Function *GuardCheck = TLI->getSSPStackGuardCheck(*M)) {
      // Generate the function-based epilogue instrumentation.
      // The target provides a guard check function, generate a call to it.
      IRBuilder<> B(RI);
      LoadInst *Guard = B.CreateLoad(B.getInt8PtrTy(), AI, true, "Guard");
      CallInst *Call = B.CreateCall(GuardCheck, {Guard});
      Call->setAttributes(GuardCheck->getAttributes());
      Call->setCallingConv(GuardCheck->getCallingConv());
    } else {
      // Generate the epilogue with inline instrumentation.
      // If we do not support SelectionDAG based tail calls, generate IR level
      // tail calls.
      //
      // For each block with a return instruction, convert this:
      //
      //   return:
      //     ...
      //     ret ...
      //
      // into this:
      //
      //   return:
      //     ...
      //     %1 = <stack guard>
      //     %2 = load StackGuardSlot
      //     %3 = cmp i1 %1, %2
      //     br i1 %3, label %SP_return, label %CallStackCheckFailBlk
      //
      //   SP_return:
      //     ret ...
      //
      //   CallStackCheckFailBlk:
      //     call void @__stack_chk_fail()
      //     unreachable

// Create the FailBB. We duplicate the BB every time since the MI tail
      // merge pass will merge together all of the various BB into one including
      // fail BB generated by the stack protector pseudo instruction.
      BasicBlock *FailBB = CreateFailBB();

// Split the basic block before the return instruction.
      BasicBlock *NewBB = BB->splitBasicBlock(RI->getIterator(), "SP_return");

// Update the dominator tree if we need to.
      if (DT && DT->isReachableFromEntry(BB)) {
        DT->addNewBlock(NewBB, BB);
        DT->addNewBlock(FailBB, BB);
      }

// Remove default branch instruction to the new BB.
      BB->getTerminator()->eraseFromParent();

// Move the newly created basic block to the point right after the old
      // basic block so that it's in the "fall through" position.
      NewBB->moveAfter(BB);

// Generate the stack protector instructions in the old basic block.
      IRBuilder<> B(BB);
      Value *Guard = getStackGuard(TLI, M, B);
      LoadInst *LI2 = B.CreateLoad(B.getInt8PtrTy(), AI, true);
      Value *Cmp = B.CreateICmpEQ(Guard, LI2);
      auto SuccessProb =
          BranchProbabilityInfo::getBranchProbStackProtector(true);
      auto FailureProb =
          BranchProbabilityInfo::getBranchProbStackProtector(false);
      MDNode *Weights = MDBuilder(F->getContext())
                            .createBranchWeights(SuccessProb.getNumerator(),
                                                 FailureProb.getNumerator());
      B.CreateCondBr(Cmp, NewBB, FailBB, Weights);
    }
  }

// Return if we didn't modify any basic blocks. i.e., there are no return
  // statements in the function.
  return HasPrologue;
}

/// CreateFailBB - Create a basic block to jump to when the stack protector
/// check fails.
BasicBlock *StackProtector::CreateFailBB() {
  LLVMContext &Context = F->getContext();
  BasicBlock *FailBB = BasicBlock::Create(Context, "CallStackCheckFailBlk", F);
  IRBuilder<> B(FailBB);
  B.SetCurrentDebugLocation(DebugLoc::get(0, 0, F->getSubprogram()));
  if (Trip.isOSOpenBSD()) {
    FunctionCallee StackChkFail = M->getOrInsertFunction(
        "__stack_smash_handler", Type::getVoidTy(Context),
        Type::getInt8PtrTy(Context));

B.CreateCall(StackChkFail, B.CreateGlobalStringPtr(F->getName(), "SSH"));
  } else {
    FunctionCallee StackChkFail =
        M->getOrInsertFunction("__stack_chk_fail", Type::getVoidTy(Context));

B.CreateCall(StackChkFail, {});
  }
  B.CreateUnreachable();
  return FailBB;
}

bool StackProtector::shouldEmitSDCheck(const BasicBlock &BB) const {
  return HasPrologue && !HasIRCheck && isa<ReturnInst>(BB.getTerminator());
}

void StackProtector::copyToMachineFrameInfo(MachineFrameInfo &MFI) const {
  if (Layout.empty())
    return;

for (int I = 0, E = MFI.getObjectIndexEnd(); I != E; ++I) {
    if (MFI.isDeadObjectIndex(I))
      continue;

const AllocaInst *AI = MFI.getObjectAllocation(I);
    if (!AI)
      continue;

SSPLayoutMap::const_iterator LI = Layout.find(AI);
    if (LI == Layout.end())
      continue;

MFI.setObjectSSPLayout(I, LI->second);
  }
}

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