AddressSanitizer.cpp revision d4429214a2dffcfd8f97956ac8b1a67c4795d242 
1//===-- AddressSanitizer.cpp - memory error detector ------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file is a part of AddressSanitizer, an address sanity checker.
11// Details of the algorithm:
12//  http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
13//
14//===----------------------------------------------------------------------===//
15
16#define DEBUG_TYPE "asan"
17
18#include "llvm/Transforms/Instrumentation.h"
19#include "llvm/ADT/ArrayRef.h"
20#include "llvm/ADT/DenseMap.h"
21#include "llvm/ADT/DepthFirstIterator.h"
22#include "llvm/ADT/OwningPtr.h"
23#include "llvm/ADT/SmallSet.h"
24#include "llvm/ADT/SmallString.h"
25#include "llvm/ADT/SmallVector.h"
26#include "llvm/ADT/StringExtras.h"
27#include "llvm/ADT/Triple.h"
28#include "llvm/DIBuilder.h"
29#include "llvm/IR/DataLayout.h"
30#include "llvm/IR/Function.h"
31#include "llvm/IR/IRBuilder.h"
32#include "llvm/IR/InlineAsm.h"
33#include "llvm/IR/IntrinsicInst.h"
34#include "llvm/IR/LLVMContext.h"
35#include "llvm/IR/Module.h"
36#include "llvm/IR/Type.h"
37#include "llvm/InstVisitor.h"
38#include "llvm/Support/CallSite.h"
39#include "llvm/Support/CommandLine.h"
40#include "llvm/Support/DataTypes.h"
41#include "llvm/Support/Debug.h"
42#include "llvm/Support/Endian.h"
43#include "llvm/Support/raw_ostream.h"
44#include "llvm/Support/system_error.h"
45#include "llvm/Transforms/Utils/BasicBlockUtils.h"
46#include "llvm/Transforms/Utils/BlackList.h"
47#include "llvm/Transforms/Utils/Cloning.h"
48#include "llvm/Transforms/Utils/Local.h"
49#include "llvm/Transforms/Utils/ModuleUtils.h"
50#include <algorithm>
51#include <string>
52
53using namespace llvm;
54
55static const uint64_t kDefaultShadowScale = 3;
56static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
57static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
58static const uint64_t kDefaultShort64bitShadowOffset = 0x7FFF8000;  // < 2G.
59static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
60static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa8000;
61
62static const size_t kMaxStackMallocSize = 1 << 16;  // 64K
63static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
64static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
65
66static const char *kAsanModuleCtorName = "asan.module_ctor";
67static const char *kAsanModuleDtorName = "asan.module_dtor";
68static const int   kAsanCtorAndCtorPriority = 1;
69static const char *kAsanReportErrorTemplate = "__asan_report_";
70static const char *kAsanReportLoadN = "__asan_report_load_n";
71static const char *kAsanReportStoreN = "__asan_report_store_n";
72static const char *kAsanRegisterGlobalsName = "__asan_register_globals";
73static const char *kAsanUnregisterGlobalsName = "__asan_unregister_globals";
74static const char *kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
75static const char *kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
76static const char *kAsanInitName = "__asan_init_v3";
77static const char *kAsanHandleNoReturnName = "__asan_handle_no_return";
78static const char *kAsanMappingOffsetName = "__asan_mapping_offset";
79static const char *kAsanMappingScaleName = "__asan_mapping_scale";
80static const char *kAsanStackMallocName = "__asan_stack_malloc";
81static const char *kAsanStackFreeName = "__asan_stack_free";
82static const char *kAsanGenPrefix = "__asan_gen_";
83static const char *kAsanPoisonStackMemoryName = "__asan_poison_stack_memory";
84static const char *kAsanUnpoisonStackMemoryName =
85    "__asan_unpoison_stack_memory";
86
87static const int kAsanStackLeftRedzoneMagic = 0xf1;
88static const int kAsanStackMidRedzoneMagic = 0xf2;
89static const int kAsanStackRightRedzoneMagic = 0xf3;
90static const int kAsanStackPartialRedzoneMagic = 0xf4;
91
92// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
93static const size_t kNumberOfAccessSizes = 5;
94
95// Command-line flags.
96
97// This flag may need to be replaced with -f[no-]asan-reads.
98static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
99       cl::desc("instrument read instructions"), cl::Hidden, cl::init(true));
100static cl::opt<bool> ClInstrumentWrites("asan-instrument-writes",
101       cl::desc("instrument write instructions"), cl::Hidden, cl::init(true));
102static cl::opt<bool> ClInstrumentAtomics("asan-instrument-atomics",
103       cl::desc("instrument atomic instructions (rmw, cmpxchg)"),
104       cl::Hidden, cl::init(true));
105static cl::opt<bool> ClAlwaysSlowPath("asan-always-slow-path",
106       cl::desc("use instrumentation with slow path for all accesses"),
107       cl::Hidden, cl::init(false));
108// This flag limits the number of instructions to be instrumented
109// in any given BB. Normally, this should be set to unlimited (INT_MAX),
110// but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary
111// set it to 10000.
112static cl::opt<int> ClMaxInsnsToInstrumentPerBB("asan-max-ins-per-bb",
113       cl::init(10000),
114       cl::desc("maximal number of instructions to instrument in any given BB"),
115       cl::Hidden);
116// This flag may need to be replaced with -f[no]asan-stack.
117static cl::opt<bool> ClStack("asan-stack",
118       cl::desc("Handle stack memory"), cl::Hidden, cl::init(true));
119// This flag may need to be replaced with -f[no]asan-use-after-return.
120static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
121       cl::desc("Check return-after-free"), cl::Hidden, cl::init(false));
122// This flag may need to be replaced with -f[no]asan-globals.
123static cl::opt<bool> ClGlobals("asan-globals",
124       cl::desc("Handle global objects"), cl::Hidden, cl::init(true));
125static cl::opt<bool> ClInitializers("asan-initialization-order",
126       cl::desc("Handle C++ initializer order"), cl::Hidden, cl::init(false));
127static cl::opt<bool> ClMemIntrin("asan-memintrin",
128       cl::desc("Handle memset/memcpy/memmove"), cl::Hidden, cl::init(true));
129static cl::opt<bool> ClRealignStack("asan-realign-stack",
130       cl::desc("Realign stack to 32"), cl::Hidden, cl::init(true));
131static cl::opt<std::string> ClBlacklistFile("asan-blacklist",
132       cl::desc("File containing the list of objects to ignore "
133                "during instrumentation"), cl::Hidden);
134
135// This is an experimental feature that will allow to choose between
136// instrumented and non-instrumented code at link-time.
137// If this option is on, just before instrumenting a function we create its
138// clone; if the function is not changed by asan the clone is deleted.
139// If we end up with a clone, we put the instrumented function into a section
140// called "ASAN" and the uninstrumented function into a section called "NOASAN".
141//
142// This is still a prototype, we need to figure out a way to keep two copies of
143// a function so that the linker can easily choose one of them.
144static cl::opt<bool> ClKeepUninstrumented("asan-keep-uninstrumented-functions",
145       cl::desc("Keep uninstrumented copies of functions"),
146       cl::Hidden, cl::init(false));
147
148// These flags allow to change the shadow mapping.
149// The shadow mapping looks like
150//    Shadow = (Mem >> scale) + (1 << offset_log)
151static cl::opt<int> ClMappingScale("asan-mapping-scale",
152       cl::desc("scale of asan shadow mapping"), cl::Hidden, cl::init(0));
153static cl::opt<int> ClMappingOffsetLog("asan-mapping-offset-log",
154       cl::desc("offset of asan shadow mapping"), cl::Hidden, cl::init(-1));
155static cl::opt<bool> ClShort64BitOffset("asan-short-64bit-mapping-offset",
156       cl::desc("Use short immediate constant as the mapping offset for 64bit"),
157       cl::Hidden, cl::init(true));
158
159// Optimization flags. Not user visible, used mostly for testing
160// and benchmarking the tool.
161static cl::opt<bool> ClOpt("asan-opt",
162       cl::desc("Optimize instrumentation"), cl::Hidden, cl::init(true));
163static cl::opt<bool> ClOptSameTemp("asan-opt-same-temp",
164       cl::desc("Instrument the same temp just once"), cl::Hidden,
165       cl::init(true));
166static cl::opt<bool> ClOptGlobals("asan-opt-globals",
167       cl::desc("Don't instrument scalar globals"), cl::Hidden, cl::init(true));
168
169static cl::opt<bool> ClCheckLifetime("asan-check-lifetime",
170       cl::desc("Use llvm.lifetime intrinsics to insert extra checks"),
171       cl::Hidden, cl::init(false));
172
173// Debug flags.
174static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
175                            cl::init(0));
176static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
177                                 cl::Hidden, cl::init(0));
178static cl::opt<std::string> ClDebugFunc("asan-debug-func",
179                                        cl::Hidden, cl::desc("Debug func"));
180static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
181                               cl::Hidden, cl::init(-1));
182static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"),
183                               cl::Hidden, cl::init(-1));
184
185namespace {
186/// A set of dynamically initialized globals extracted from metadata.
187class SetOfDynamicallyInitializedGlobals {
188 public:
189  void Init(Module& M) {
190    // Clang generates metadata identifying all dynamically initialized globals.
191    NamedMDNode *DynamicGlobals =
192        M.getNamedMetadata("llvm.asan.dynamically_initialized_globals");
193    if (!DynamicGlobals)
194      return;
195    for (int i = 0, n = DynamicGlobals->getNumOperands(); i < n; ++i) {
196      MDNode *MDN = DynamicGlobals->getOperand(i);
197      assert(MDN->getNumOperands() == 1);
198      Value *VG = MDN->getOperand(0);
199      // The optimizer may optimize away a global entirely, in which case we
200      // cannot instrument access to it.
201      if (!VG)
202        continue;
203      DynInitGlobals.insert(cast<GlobalVariable>(VG));
204    }
205  }
206  bool Contains(GlobalVariable *G) { return DynInitGlobals.count(G) != 0; }
207 private:
208  SmallSet<GlobalValue*, 32> DynInitGlobals;
209};
210
211/// This struct defines the shadow mapping using the rule:
212///   shadow = (mem >> Scale) ADD-or-OR Offset.
213struct ShadowMapping {
214  int Scale;
215  uint64_t Offset;
216  bool OrShadowOffset;
217};
218
219static ShadowMapping getShadowMapping(const Module &M, int LongSize,
220                                      bool ZeroBaseShadow) {
221  llvm::Triple TargetTriple(M.getTargetTriple());
222  bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
223  bool IsMacOSX = TargetTriple.getOS() == llvm::Triple::MacOSX;
224  bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64;
225  bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
226  bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips ||
227                  TargetTriple.getArch() == llvm::Triple::mipsel;
228
229  ShadowMapping Mapping;
230
231  // OR-ing shadow offset if more efficient (at least on x86),
232  // but on ppc64 we have to use add since the shadow offset is not neccesary
233  // 1/8-th of the address space.
234  Mapping.OrShadowOffset = !IsPPC64 && !ClShort64BitOffset;
235
236  Mapping.Offset = (IsAndroid || ZeroBaseShadow) ? 0 :
237      (LongSize == 32 ?
238       (IsMIPS32 ? kMIPS32_ShadowOffset32 : kDefaultShadowOffset32) :
239       IsPPC64 ? kPPC64_ShadowOffset64 : kDefaultShadowOffset64);
240  if (!ZeroBaseShadow && ClShort64BitOffset && IsX86_64 && !IsMacOSX) {
241    assert(LongSize == 64);
242    Mapping.Offset = kDefaultShort64bitShadowOffset;
243  }
244  if (!ZeroBaseShadow && ClMappingOffsetLog >= 0) {
245    // Zero offset log is the special case.
246    Mapping.Offset = (ClMappingOffsetLog == 0) ? 0 : 1ULL << ClMappingOffsetLog;
247  }
248
249  Mapping.Scale = kDefaultShadowScale;
250  if (ClMappingScale) {
251    Mapping.Scale = ClMappingScale;
252  }
253
254  return Mapping;
255}
256
257static size_t RedzoneSizeForScale(int MappingScale) {
258  // Redzone used for stack and globals is at least 32 bytes.
259  // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
260  return std::max(32U, 1U << MappingScale);
261}
262
263/// AddressSanitizer: instrument the code in module to find memory bugs.
264struct AddressSanitizer : public FunctionPass {
265  AddressSanitizer(bool CheckInitOrder = true,
266                   bool CheckUseAfterReturn = false,
267                   bool CheckLifetime = false,
268                   StringRef BlacklistFile = StringRef(),
269                   bool ZeroBaseShadow = false)
270      : FunctionPass(ID),
271        CheckInitOrder(CheckInitOrder || ClInitializers),
272        CheckUseAfterReturn(CheckUseAfterReturn || ClUseAfterReturn),
273        CheckLifetime(CheckLifetime || ClCheckLifetime),
274        BlacklistFile(BlacklistFile.empty() ? ClBlacklistFile
275                                            : BlacklistFile),
276        ZeroBaseShadow(ZeroBaseShadow) {}
277  virtual const char *getPassName() const {
278    return "AddressSanitizerFunctionPass";
279  }
280  void instrumentMop(Instruction *I);
281  void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
282                         Value *Addr, uint32_t TypeSize, bool IsWrite,
283                         Value *SizeArgument);
284  Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
285                           Value *ShadowValue, uint32_t TypeSize);
286  Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
287                                 bool IsWrite, size_t AccessSizeIndex,
288                                 Value *SizeArgument);
289  bool instrumentMemIntrinsic(MemIntrinsic *MI);
290  void instrumentMemIntrinsicParam(Instruction *OrigIns, Value *Addr,
291                                   Value *Size,
292                                   Instruction *InsertBefore, bool IsWrite);
293  Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
294  bool runOnFunction(Function &F);
295  bool maybeInsertAsanInitAtFunctionEntry(Function &F);
296  void emitShadowMapping(Module &M, IRBuilder<> &IRB) const;
297  virtual bool doInitialization(Module &M);
298  static char ID;  // Pass identification, replacement for typeid
299
300 private:
301  void initializeCallbacks(Module &M);
302
303  bool ShouldInstrumentGlobal(GlobalVariable *G);
304  bool LooksLikeCodeInBug11395(Instruction *I);
305  void FindDynamicInitializers(Module &M);
306
307  bool CheckInitOrder;
308  bool CheckUseAfterReturn;
309  bool CheckLifetime;
310  SmallString<64> BlacklistFile;
311  bool ZeroBaseShadow;
312
313  LLVMContext *C;
314  DataLayout *TD;
315  int LongSize;
316  Type *IntptrTy;
317  ShadowMapping Mapping;
318  Function *AsanCtorFunction;
319  Function *AsanInitFunction;
320  Function *AsanHandleNoReturnFunc;
321  OwningPtr<BlackList> BL;
322  // This array is indexed by AccessIsWrite and log2(AccessSize).
323  Function *AsanErrorCallback[2][kNumberOfAccessSizes];
324  // This array is indexed by AccessIsWrite.
325  Function *AsanErrorCallbackSized[2];
326  InlineAsm *EmptyAsm;
327  SetOfDynamicallyInitializedGlobals DynamicallyInitializedGlobals;
328
329  friend struct FunctionStackPoisoner;
330};
331
332class AddressSanitizerModule : public ModulePass {
333 public:
334  AddressSanitizerModule(bool CheckInitOrder = true,
335                         StringRef BlacklistFile = StringRef(),
336                         bool ZeroBaseShadow = false)
337      : ModulePass(ID),
338        CheckInitOrder(CheckInitOrder || ClInitializers),
339        BlacklistFile(BlacklistFile.empty() ? ClBlacklistFile
340                                            : BlacklistFile),
341        ZeroBaseShadow(ZeroBaseShadow) {}
342  bool runOnModule(Module &M);
343  static char ID;  // Pass identification, replacement for typeid
344  virtual const char *getPassName() const {
345    return "AddressSanitizerModule";
346  }
347
348 private:
349  void initializeCallbacks(Module &M);
350
351  bool ShouldInstrumentGlobal(GlobalVariable *G);
352  void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
353  size_t RedzoneSize() const {
354    return RedzoneSizeForScale(Mapping.Scale);
355  }
356
357  bool CheckInitOrder;
358  SmallString<64> BlacklistFile;
359  bool ZeroBaseShadow;
360
361  OwningPtr<BlackList> BL;
362  SetOfDynamicallyInitializedGlobals DynamicallyInitializedGlobals;
363  Type *IntptrTy;
364  LLVMContext *C;
365  DataLayout *TD;
366  ShadowMapping Mapping;
367  Function *AsanPoisonGlobals;
368  Function *AsanUnpoisonGlobals;
369  Function *AsanRegisterGlobals;
370  Function *AsanUnregisterGlobals;
371};
372
373// Stack poisoning does not play well with exception handling.
374// When an exception is thrown, we essentially bypass the code
375// that unpoisones the stack. This is why the run-time library has
376// to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
377// stack in the interceptor. This however does not work inside the
378// actual function which catches the exception. Most likely because the
379// compiler hoists the load of the shadow value somewhere too high.
380// This causes asan to report a non-existing bug on 453.povray.
381// It sounds like an LLVM bug.
382struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
383  Function &F;
384  AddressSanitizer &ASan;
385  DIBuilder DIB;
386  LLVMContext *C;
387  Type *IntptrTy;
388  Type *IntptrPtrTy;
389  ShadowMapping Mapping;
390
391  SmallVector<AllocaInst*, 16> AllocaVec;
392  SmallVector<Instruction*, 8> RetVec;
393  uint64_t TotalStackSize;
394  unsigned StackAlignment;
395
396  Function *AsanStackMallocFunc, *AsanStackFreeFunc;
397  Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc;
398
399  // Stores a place and arguments of poisoning/unpoisoning call for alloca.
400  struct AllocaPoisonCall {
401    IntrinsicInst *InsBefore;
402    uint64_t Size;
403    bool DoPoison;
404  };
405  SmallVector<AllocaPoisonCall, 8> AllocaPoisonCallVec;
406
407  // Maps Value to an AllocaInst from which the Value is originated.
408  typedef DenseMap<Value*, AllocaInst*> AllocaForValueMapTy;
409  AllocaForValueMapTy AllocaForValue;
410
411  FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
412      : F(F), ASan(ASan), DIB(*F.getParent()), C(ASan.C),
413        IntptrTy(ASan.IntptrTy), IntptrPtrTy(PointerType::get(IntptrTy, 0)),
414        Mapping(ASan.Mapping),
415        TotalStackSize(0), StackAlignment(1 << Mapping.Scale) {}
416
417  bool runOnFunction() {
418    if (!ClStack) return false;
419    // Collect alloca, ret, lifetime instructions etc.
420    for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
421         DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
422      BasicBlock *BB = *DI;
423      visit(*BB);
424    }
425    if (AllocaVec.empty()) return false;
426
427    initializeCallbacks(*F.getParent());
428
429    poisonStack();
430
431    if (ClDebugStack) {
432      DEBUG(dbgs() << F);
433    }
434    return true;
435  }
436
437  // Finds all static Alloca instructions and puts
438  // poisoned red zones around all of them.
439  // Then unpoison everything back before the function returns.
440  void poisonStack();
441
442  // ----------------------- Visitors.
443  /// \brief Collect all Ret instructions.
444  void visitReturnInst(ReturnInst &RI) {
445    RetVec.push_back(&RI);
446  }
447
448  /// \brief Collect Alloca instructions we want (and can) handle.
449  void visitAllocaInst(AllocaInst &AI) {
450    if (!isInterestingAlloca(AI)) return;
451
452    StackAlignment = std::max(StackAlignment, AI.getAlignment());
453    AllocaVec.push_back(&AI);
454    uint64_t AlignedSize = getAlignedAllocaSize(&AI);
455    TotalStackSize += AlignedSize;
456  }
457
458  /// \brief Collect lifetime intrinsic calls to check for use-after-scope
459  /// errors.
460  void visitIntrinsicInst(IntrinsicInst &II) {
461    if (!ASan.CheckLifetime) return;
462    Intrinsic::ID ID = II.getIntrinsicID();
463    if (ID != Intrinsic::lifetime_start &&
464        ID != Intrinsic::lifetime_end)
465      return;
466    // Found lifetime intrinsic, add ASan instrumentation if necessary.
467    ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
468    // If size argument is undefined, don't do anything.
469    if (Size->isMinusOne()) return;
470    // Check that size doesn't saturate uint64_t and can
471    // be stored in IntptrTy.
472    const uint64_t SizeValue = Size->getValue().getLimitedValue();
473    if (SizeValue == ~0ULL ||
474        !ConstantInt::isValueValidForType(IntptrTy, SizeValue))
475      return;
476    // Find alloca instruction that corresponds to llvm.lifetime argument.
477    AllocaInst *AI = findAllocaForValue(II.getArgOperand(1));
478    if (!AI) return;
479    bool DoPoison = (ID == Intrinsic::lifetime_end);
480    AllocaPoisonCall APC = {&II, SizeValue, DoPoison};
481    AllocaPoisonCallVec.push_back(APC);
482  }
483
484  // ---------------------- Helpers.
485  void initializeCallbacks(Module &M);
486
487  // Check if we want (and can) handle this alloca.
488  bool isInterestingAlloca(AllocaInst &AI) {
489    return (!AI.isArrayAllocation() &&
490            AI.isStaticAlloca() &&
491            AI.getAlignment() <= RedzoneSize() &&
492            AI.getAllocatedType()->isSized());
493  }
494
495  size_t RedzoneSize() const {
496    return RedzoneSizeForScale(Mapping.Scale);
497  }
498  uint64_t getAllocaSizeInBytes(AllocaInst *AI) {
499    Type *Ty = AI->getAllocatedType();
500    uint64_t SizeInBytes = ASan.TD->getTypeAllocSize(Ty);
501    return SizeInBytes;
502  }
503  uint64_t getAlignedSize(uint64_t SizeInBytes) {
504    size_t RZ = RedzoneSize();
505    return ((SizeInBytes + RZ - 1) / RZ) * RZ;
506  }
507  uint64_t getAlignedAllocaSize(AllocaInst *AI) {
508    uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
509    return getAlignedSize(SizeInBytes);
510  }
511  /// Finds alloca where the value comes from.
512  AllocaInst *findAllocaForValue(Value *V);
513  void poisonRedZones(const ArrayRef<AllocaInst*> &AllocaVec, IRBuilder<> IRB,
514                      Value *ShadowBase, bool DoPoison);
515  void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> IRB, bool DoPoison);
516};
517
518}  // namespace
519
520char AddressSanitizer::ID = 0;
521INITIALIZE_PASS(AddressSanitizer, "asan",
522    "AddressSanitizer: detects use-after-free and out-of-bounds bugs.",
523    false, false)
524FunctionPass *llvm::createAddressSanitizerFunctionPass(
525    bool CheckInitOrder, bool CheckUseAfterReturn, bool CheckLifetime,
526    StringRef BlacklistFile, bool ZeroBaseShadow) {
527  return new AddressSanitizer(CheckInitOrder, CheckUseAfterReturn,
528                              CheckLifetime, BlacklistFile, ZeroBaseShadow);
529}
530
531char AddressSanitizerModule::ID = 0;
532INITIALIZE_PASS(AddressSanitizerModule, "asan-module",
533    "AddressSanitizer: detects use-after-free and out-of-bounds bugs."
534    "ModulePass", false, false)
535ModulePass *llvm::createAddressSanitizerModulePass(
536    bool CheckInitOrder, StringRef BlacklistFile, bool ZeroBaseShadow) {
537  return new AddressSanitizerModule(CheckInitOrder, BlacklistFile,
538                                    ZeroBaseShadow);
539}
540
541static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
542  size_t Res = countTrailingZeros(TypeSize / 8);
543  assert(Res < kNumberOfAccessSizes);
544  return Res;
545}
546
547// Create a constant for Str so that we can pass it to the run-time lib.
548static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str) {
549  Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
550  GlobalVariable *GV = new GlobalVariable(M, StrConst->getType(), true,
551                            GlobalValue::PrivateLinkage, StrConst,
552                            kAsanGenPrefix);
553  GV->setUnnamedAddr(true);  // Ok to merge these.
554  GV->setAlignment(1);  // Strings may not be merged w/o setting align 1.
555  return GV;
556}
557
558static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
559  return G->getName().find(kAsanGenPrefix) == 0;
560}
561
562Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
563  // Shadow >> scale
564  Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
565  if (Mapping.Offset == 0)
566    return Shadow;
567  // (Shadow >> scale) | offset
568  if (Mapping.OrShadowOffset)
569    return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
570  else
571    return IRB.CreateAdd(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
572}
573
574void AddressSanitizer::instrumentMemIntrinsicParam(
575    Instruction *OrigIns,
576    Value *Addr, Value *Size, Instruction *InsertBefore, bool IsWrite) {
577  IRBuilder<> IRB(InsertBefore);
578  if (Size->getType() != IntptrTy)
579    Size = IRB.CreateIntCast(Size, IntptrTy, false);
580  // Check the first byte.
581  instrumentAddress(OrigIns, InsertBefore, Addr, 8, IsWrite, Size);
582  // Check the last byte.
583  IRB.SetInsertPoint(InsertBefore);
584  Value *SizeMinusOne = IRB.CreateSub(Size, ConstantInt::get(IntptrTy, 1));
585  Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
586  Value *AddrLast = IRB.CreateAdd(AddrLong, SizeMinusOne);
587  instrumentAddress(OrigIns, InsertBefore, AddrLast, 8, IsWrite, Size);
588}
589
590// Instrument memset/memmove/memcpy
591bool AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
592  Value *Dst = MI->getDest();
593  MemTransferInst *MemTran = dyn_cast<MemTransferInst>(MI);
594  Value *Src = MemTran ? MemTran->getSource() : 0;
595  Value *Length = MI->getLength();
596
597  Constant *ConstLength = dyn_cast<Constant>(Length);
598  Instruction *InsertBefore = MI;
599  if (ConstLength) {
600    if (ConstLength->isNullValue()) return false;
601  } else {
602    // The size is not a constant so it could be zero -- check at run-time.
603    IRBuilder<> IRB(InsertBefore);
604
605    Value *Cmp = IRB.CreateICmpNE(Length,
606                                  Constant::getNullValue(Length->getType()));
607    InsertBefore = SplitBlockAndInsertIfThen(cast<Instruction>(Cmp), false);
608  }
609
610  instrumentMemIntrinsicParam(MI, Dst, Length, InsertBefore, true);
611  if (Src)
612    instrumentMemIntrinsicParam(MI, Src, Length, InsertBefore, false);
613  return true;
614}
615
616// If I is an interesting memory access, return the PointerOperand
617// and set IsWrite. Otherwise return NULL.
618static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite) {
619  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
620    if (!ClInstrumentReads) return NULL;
621    *IsWrite = false;
622    return LI->getPointerOperand();
623  }
624  if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
625    if (!ClInstrumentWrites) return NULL;
626    *IsWrite = true;
627    return SI->getPointerOperand();
628  }
629  if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
630    if (!ClInstrumentAtomics) return NULL;
631    *IsWrite = true;
632    return RMW->getPointerOperand();
633  }
634  if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
635    if (!ClInstrumentAtomics) return NULL;
636    *IsWrite = true;
637    return XCHG->getPointerOperand();
638  }
639  return NULL;
640}
641
642void AddressSanitizer::instrumentMop(Instruction *I) {
643  bool IsWrite = false;
644  Value *Addr = isInterestingMemoryAccess(I, &IsWrite);
645  assert(Addr);
646  if (ClOpt && ClOptGlobals) {
647    if (GlobalVariable *G = dyn_cast<GlobalVariable>(Addr)) {
648      // If initialization order checking is disabled, a simple access to a
649      // dynamically initialized global is always valid.
650      if (!CheckInitOrder)
651        return;
652      // If a global variable does not have dynamic initialization we don't
653      // have to instrument it.  However, if a global does not have initailizer
654      // at all, we assume it has dynamic initializer (in other TU).
655      if (G->hasInitializer() && !DynamicallyInitializedGlobals.Contains(G))
656        return;
657    }
658  }
659
660  Type *OrigPtrTy = Addr->getType();
661  Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
662
663  assert(OrigTy->isSized());
664  uint32_t TypeSize = TD->getTypeStoreSizeInBits(OrigTy);
665
666  assert((TypeSize % 8) == 0);
667
668  // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check.
669  if (TypeSize == 8  || TypeSize == 16 ||
670      TypeSize == 32 || TypeSize == 64 || TypeSize == 128)
671    return instrumentAddress(I, I, Addr, TypeSize, IsWrite, 0);
672  // Instrument unusual size (but still multiple of 8).
673  // We can not do it with a single check, so we do 1-byte check for the first
674  // and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
675  // to report the actual access size.
676  IRBuilder<> IRB(I);
677  Value *LastByte =  IRB.CreateIntToPtr(
678      IRB.CreateAdd(IRB.CreatePointerCast(Addr, IntptrTy),
679                    ConstantInt::get(IntptrTy, TypeSize / 8 - 1)),
680      OrigPtrTy);
681  Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8);
682  instrumentAddress(I, I, Addr, 8, IsWrite, Size);
683  instrumentAddress(I, I, LastByte, 8, IsWrite, Size);
684}
685
686// Validate the result of Module::getOrInsertFunction called for an interface
687// function of AddressSanitizer. If the instrumented module defines a function
688// with the same name, their prototypes must match, otherwise
689// getOrInsertFunction returns a bitcast.
690static Function *checkInterfaceFunction(Constant *FuncOrBitcast) {
691  if (isa<Function>(FuncOrBitcast)) return cast<Function>(FuncOrBitcast);
692  FuncOrBitcast->dump();
693  report_fatal_error("trying to redefine an AddressSanitizer "
694                     "interface function");
695}
696
697Instruction *AddressSanitizer::generateCrashCode(
698    Instruction *InsertBefore, Value *Addr,
699    bool IsWrite, size_t AccessSizeIndex, Value *SizeArgument) {
700  IRBuilder<> IRB(InsertBefore);
701  CallInst *Call = SizeArgument
702    ? IRB.CreateCall2(AsanErrorCallbackSized[IsWrite], Addr, SizeArgument)
703    : IRB.CreateCall(AsanErrorCallback[IsWrite][AccessSizeIndex], Addr);
704
705  // We don't do Call->setDoesNotReturn() because the BB already has
706  // UnreachableInst at the end.
707  // This EmptyAsm is required to avoid callback merge.
708  IRB.CreateCall(EmptyAsm);
709  return Call;
710}
711
712Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
713                                            Value *ShadowValue,
714                                            uint32_t TypeSize) {
715  size_t Granularity = 1 << Mapping.Scale;
716  // Addr & (Granularity - 1)
717  Value *LastAccessedByte = IRB.CreateAnd(
718      AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
719  // (Addr & (Granularity - 1)) + size - 1
720  if (TypeSize / 8 > 1)
721    LastAccessedByte = IRB.CreateAdd(
722        LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
723  // (uint8_t) ((Addr & (Granularity-1)) + size - 1)
724  LastAccessedByte = IRB.CreateIntCast(
725      LastAccessedByte, ShadowValue->getType(), false);
726  // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
727  return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
728}
729
730void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
731                                         Instruction *InsertBefore,
732                                         Value *Addr, uint32_t TypeSize,
733                                         bool IsWrite, Value *SizeArgument) {
734  IRBuilder<> IRB(InsertBefore);
735  Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
736
737  Type *ShadowTy  = IntegerType::get(
738      *C, std::max(8U, TypeSize >> Mapping.Scale));
739  Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
740  Value *ShadowPtr = memToShadow(AddrLong, IRB);
741  Value *CmpVal = Constant::getNullValue(ShadowTy);
742  Value *ShadowValue = IRB.CreateLoad(
743      IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
744
745  Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
746  size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
747  size_t Granularity = 1 << Mapping.Scale;
748  TerminatorInst *CrashTerm = 0;
749
750  if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) {
751    TerminatorInst *CheckTerm =
752        SplitBlockAndInsertIfThen(cast<Instruction>(Cmp), false);
753    assert(dyn_cast<BranchInst>(CheckTerm)->isUnconditional());
754    BasicBlock *NextBB = CheckTerm->getSuccessor(0);
755    IRB.SetInsertPoint(CheckTerm);
756    Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
757    BasicBlock *CrashBlock =
758        BasicBlock::Create(*C, "", NextBB->getParent(), NextBB);
759    CrashTerm = new UnreachableInst(*C, CrashBlock);
760    BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
761    ReplaceInstWithInst(CheckTerm, NewTerm);
762  } else {
763    CrashTerm = SplitBlockAndInsertIfThen(cast<Instruction>(Cmp), true);
764  }
765
766  Instruction *Crash = generateCrashCode(
767      CrashTerm, AddrLong, IsWrite, AccessSizeIndex, SizeArgument);
768  Crash->setDebugLoc(OrigIns->getDebugLoc());
769}
770
771void AddressSanitizerModule::createInitializerPoisonCalls(
772    Module &M, GlobalValue *ModuleName) {
773  // We do all of our poisoning and unpoisoning within _GLOBAL__I_a.
774  Function *GlobalInit = M.getFunction("_GLOBAL__I_a");
775  // If that function is not present, this TU contains no globals, or they have
776  // all been optimized away
777  if (!GlobalInit)
778    return;
779
780  // Set up the arguments to our poison/unpoison functions.
781  IRBuilder<> IRB(GlobalInit->begin()->getFirstInsertionPt());
782
783  // Add a call to poison all external globals before the given function starts.
784  Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
785  IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
786
787  // Add calls to unpoison all globals before each return instruction.
788  for (Function::iterator I = GlobalInit->begin(), E = GlobalInit->end();
789      I != E; ++I) {
790    if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator())) {
791      CallInst::Create(AsanUnpoisonGlobals, "", RI);
792    }
793  }
794}
795
796bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
797  Type *Ty = cast<PointerType>(G->getType())->getElementType();
798  DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
799
800  if (BL->isIn(*G)) return false;
801  if (!Ty->isSized()) return false;
802  if (!G->hasInitializer()) return false;
803  if (GlobalWasGeneratedByAsan(G)) return false;  // Our own global.
804  // Touch only those globals that will not be defined in other modules.
805  // Don't handle ODR type linkages since other modules may be built w/o asan.
806  if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
807      G->getLinkage() != GlobalVariable::PrivateLinkage &&
808      G->getLinkage() != GlobalVariable::InternalLinkage)
809    return false;
810  // Two problems with thread-locals:
811  //   - The address of the main thread's copy can't be computed at link-time.
812  //   - Need to poison all copies, not just the main thread's one.
813  if (G->isThreadLocal())
814    return false;
815  // For now, just ignore this Alloca if the alignment is large.
816  if (G->getAlignment() > RedzoneSize()) return false;
817
818  // Ignore all the globals with the names starting with "\01L_OBJC_".
819  // Many of those are put into the .cstring section. The linker compresses
820  // that section by removing the spare \0s after the string terminator, so
821  // our redzones get broken.
822  if ((G->getName().find("\01L_OBJC_") == 0) ||
823      (G->getName().find("\01l_OBJC_") == 0)) {
824    DEBUG(dbgs() << "Ignoring \\01L_OBJC_* global: " << *G);
825    return false;
826  }
827
828  if (G->hasSection()) {
829    StringRef Section(G->getSection());
830    // Ignore the globals from the __OBJC section. The ObjC runtime assumes
831    // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
832    // them.
833    if ((Section.find("__OBJC,") == 0) ||
834        (Section.find("__DATA, __objc_") == 0)) {
835      DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G);
836      return false;
837    }
838    // See http://code.google.com/p/address-sanitizer/issues/detail?id=32
839    // Constant CFString instances are compiled in the following way:
840    //  -- the string buffer is emitted into
841    //     __TEXT,__cstring,cstring_literals
842    //  -- the constant NSConstantString structure referencing that buffer
843    //     is placed into __DATA,__cfstring
844    // Therefore there's no point in placing redzones into __DATA,__cfstring.
845    // Moreover, it causes the linker to crash on OS X 10.7
846    if (Section.find("__DATA,__cfstring") == 0) {
847      DEBUG(dbgs() << "Ignoring CFString: " << *G);
848      return false;
849    }
850  }
851
852  return true;
853}
854
855void AddressSanitizerModule::initializeCallbacks(Module &M) {
856  IRBuilder<> IRB(*C);
857  // Declare our poisoning and unpoisoning functions.
858  AsanPoisonGlobals = checkInterfaceFunction(M.getOrInsertFunction(
859      kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, NULL));
860  AsanPoisonGlobals->setLinkage(Function::ExternalLinkage);
861  AsanUnpoisonGlobals = checkInterfaceFunction(M.getOrInsertFunction(
862      kAsanUnpoisonGlobalsName, IRB.getVoidTy(), NULL));
863  AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
864  // Declare functions that register/unregister globals.
865  AsanRegisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
866      kAsanRegisterGlobalsName, IRB.getVoidTy(),
867      IntptrTy, IntptrTy, NULL));
868  AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
869  AsanUnregisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
870      kAsanUnregisterGlobalsName,
871      IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
872  AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
873}
874
875// This function replaces all global variables with new variables that have
876// trailing redzones. It also creates a function that poisons
877// redzones and inserts this function into llvm.global_ctors.
878bool AddressSanitizerModule::runOnModule(Module &M) {
879  if (!ClGlobals) return false;
880  TD = getAnalysisIfAvailable<DataLayout>();
881  if (!TD)
882    return false;
883  BL.reset(new BlackList(BlacklistFile));
884  if (BL->isIn(M)) return false;
885  C = &(M.getContext());
886  int LongSize = TD->getPointerSizeInBits();
887  IntptrTy = Type::getIntNTy(*C, LongSize);
888  Mapping = getShadowMapping(M, LongSize, ZeroBaseShadow);
889  initializeCallbacks(M);
890  DynamicallyInitializedGlobals.Init(M);
891
892  SmallVector<GlobalVariable *, 16> GlobalsToChange;
893
894  for (Module::GlobalListType::iterator G = M.global_begin(),
895       E = M.global_end(); G != E; ++G) {
896    if (ShouldInstrumentGlobal(G))
897      GlobalsToChange.push_back(G);
898  }
899
900  size_t n = GlobalsToChange.size();
901  if (n == 0) return false;
902
903  // A global is described by a structure
904  //   size_t beg;
905  //   size_t size;
906  //   size_t size_with_redzone;
907  //   const char *name;
908  //   const char *module_name;
909  //   size_t has_dynamic_init;
910  // We initialize an array of such structures and pass it to a run-time call.
911  StructType *GlobalStructTy = StructType::get(IntptrTy, IntptrTy,
912                                               IntptrTy, IntptrTy,
913                                               IntptrTy, IntptrTy, NULL);
914  SmallVector<Constant *, 16> Initializers(n), DynamicInit;
915
916
917  Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
918  assert(CtorFunc);
919  IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
920
921  bool HasDynamicallyInitializedGlobals = false;
922
923  GlobalVariable *ModuleName = createPrivateGlobalForString(
924      M, M.getModuleIdentifier());
925  // We shouldn't merge same module names, as this string serves as unique
926  // module ID in runtime.
927  ModuleName->setUnnamedAddr(false);
928
929  for (size_t i = 0; i < n; i++) {
930    static const uint64_t kMaxGlobalRedzone = 1 << 18;
931    GlobalVariable *G = GlobalsToChange[i];
932    PointerType *PtrTy = cast<PointerType>(G->getType());
933    Type *Ty = PtrTy->getElementType();
934    uint64_t SizeInBytes = TD->getTypeAllocSize(Ty);
935    uint64_t MinRZ = RedzoneSize();
936    // MinRZ <= RZ <= kMaxGlobalRedzone
937    // and trying to make RZ to be ~ 1/4 of SizeInBytes.
938    uint64_t RZ = std::max(MinRZ,
939                         std::min(kMaxGlobalRedzone,
940                                  (SizeInBytes / MinRZ / 4) * MinRZ));
941    uint64_t RightRedzoneSize = RZ;
942    // Round up to MinRZ
943    if (SizeInBytes % MinRZ)
944      RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
945    assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
946    Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
947    // Determine whether this global should be poisoned in initialization.
948    bool GlobalHasDynamicInitializer =
949        DynamicallyInitializedGlobals.Contains(G);
950    // Don't check initialization order if this global is blacklisted.
951    GlobalHasDynamicInitializer &= !BL->isInInit(*G);
952
953    StructType *NewTy = StructType::get(Ty, RightRedZoneTy, NULL);
954    Constant *NewInitializer = ConstantStruct::get(
955        NewTy, G->getInitializer(),
956        Constant::getNullValue(RightRedZoneTy), NULL);
957
958    GlobalVariable *Name = createPrivateGlobalForString(M, G->getName());
959
960    // Create a new global variable with enough space for a redzone.
961    GlobalVariable *NewGlobal = new GlobalVariable(
962        M, NewTy, G->isConstant(), G->getLinkage(),
963        NewInitializer, "", G, G->getThreadLocalMode());
964    NewGlobal->copyAttributesFrom(G);
965    NewGlobal->setAlignment(MinRZ);
966
967    Value *Indices2[2];
968    Indices2[0] = IRB.getInt32(0);
969    Indices2[1] = IRB.getInt32(0);
970
971    G->replaceAllUsesWith(
972        ConstantExpr::getGetElementPtr(NewGlobal, Indices2, true));
973    NewGlobal->takeName(G);
974    G->eraseFromParent();
975
976    Initializers[i] = ConstantStruct::get(
977        GlobalStructTy,
978        ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
979        ConstantInt::get(IntptrTy, SizeInBytes),
980        ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
981        ConstantExpr::getPointerCast(Name, IntptrTy),
982        ConstantExpr::getPointerCast(ModuleName, IntptrTy),
983        ConstantInt::get(IntptrTy, GlobalHasDynamicInitializer),
984        NULL);
985
986    // Populate the first and last globals declared in this TU.
987    if (CheckInitOrder && GlobalHasDynamicInitializer)
988      HasDynamicallyInitializedGlobals = true;
989
990    DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
991  }
992
993  ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
994  GlobalVariable *AllGlobals = new GlobalVariable(
995      M, ArrayOfGlobalStructTy, false, GlobalVariable::PrivateLinkage,
996      ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
997
998  // Create calls for poisoning before initializers run and unpoisoning after.
999  if (CheckInitOrder && HasDynamicallyInitializedGlobals)
1000    createInitializerPoisonCalls(M, ModuleName);
1001  IRB.CreateCall2(AsanRegisterGlobals,
1002                  IRB.CreatePointerCast(AllGlobals, IntptrTy),
1003                  ConstantInt::get(IntptrTy, n));
1004
1005  // We also need to unregister globals at the end, e.g. when a shared library
1006  // gets closed.
1007  Function *AsanDtorFunction = Function::Create(
1008      FunctionType::get(Type::getVoidTy(*C), false),
1009      GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
1010  BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
1011  IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
1012  IRB_Dtor.CreateCall2(AsanUnregisterGlobals,
1013                       IRB.CreatePointerCast(AllGlobals, IntptrTy),
1014                       ConstantInt::get(IntptrTy, n));
1015  appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndCtorPriority);
1016
1017  DEBUG(dbgs() << M);
1018  return true;
1019}
1020
1021void AddressSanitizer::initializeCallbacks(Module &M) {
1022  IRBuilder<> IRB(*C);
1023  // Create __asan_report* callbacks.
1024  for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
1025    for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
1026         AccessSizeIndex++) {
1027      // IsWrite and TypeSize are encoded in the function name.
1028      std::string FunctionName = std::string(kAsanReportErrorTemplate) +
1029          (AccessIsWrite ? "store" : "load") + itostr(1 << AccessSizeIndex);
1030      // If we are merging crash callbacks, they have two parameters.
1031      AsanErrorCallback[AccessIsWrite][AccessSizeIndex] =
1032          checkInterfaceFunction(M.getOrInsertFunction(
1033              FunctionName, IRB.getVoidTy(), IntptrTy, NULL));
1034    }
1035  }
1036  AsanErrorCallbackSized[0] = checkInterfaceFunction(M.getOrInsertFunction(
1037              kAsanReportLoadN, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
1038  AsanErrorCallbackSized[1] = checkInterfaceFunction(M.getOrInsertFunction(
1039              kAsanReportStoreN, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
1040
1041  AsanHandleNoReturnFunc = checkInterfaceFunction(M.getOrInsertFunction(
1042      kAsanHandleNoReturnName, IRB.getVoidTy(), NULL));
1043  // We insert an empty inline asm after __asan_report* to avoid callback merge.
1044  EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
1045                            StringRef(""), StringRef(""),
1046                            /*hasSideEffects=*/true);
1047}
1048
1049void AddressSanitizer::emitShadowMapping(Module &M, IRBuilder<> &IRB) const {
1050  // Tell the values of mapping offset and scale to the run-time.
1051  GlobalValue *asan_mapping_offset =
1052      new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
1053                     ConstantInt::get(IntptrTy, Mapping.Offset),
1054                     kAsanMappingOffsetName);
1055  // Read the global, otherwise it may be optimized away.
1056  IRB.CreateLoad(asan_mapping_offset, true);
1057
1058  GlobalValue *asan_mapping_scale =
1059      new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
1060                         ConstantInt::get(IntptrTy, Mapping.Scale),
1061                         kAsanMappingScaleName);
1062  // Read the global, otherwise it may be optimized away.
1063  IRB.CreateLoad(asan_mapping_scale, true);
1064}
1065
1066// virtual
1067bool AddressSanitizer::doInitialization(Module &M) {
1068  // Initialize the private fields. No one has accessed them before.
1069  TD = getAnalysisIfAvailable<DataLayout>();
1070
1071  if (!TD)
1072    return false;
1073  BL.reset(new BlackList(BlacklistFile));
1074  DynamicallyInitializedGlobals.Init(M);
1075
1076  C = &(M.getContext());
1077  LongSize = TD->getPointerSizeInBits();
1078  IntptrTy = Type::getIntNTy(*C, LongSize);
1079
1080  AsanCtorFunction = Function::Create(
1081      FunctionType::get(Type::getVoidTy(*C), false),
1082      GlobalValue::InternalLinkage, kAsanModuleCtorName, &M);
1083  BasicBlock *AsanCtorBB = BasicBlock::Create(*C, "", AsanCtorFunction);
1084  // call __asan_init in the module ctor.
1085  IRBuilder<> IRB(ReturnInst::Create(*C, AsanCtorBB));
1086  AsanInitFunction = checkInterfaceFunction(
1087      M.getOrInsertFunction(kAsanInitName, IRB.getVoidTy(), NULL));
1088  AsanInitFunction->setLinkage(Function::ExternalLinkage);
1089  IRB.CreateCall(AsanInitFunction);
1090
1091  Mapping = getShadowMapping(M, LongSize, ZeroBaseShadow);
1092  emitShadowMapping(M, IRB);
1093
1094  appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndCtorPriority);
1095  return true;
1096}
1097
1098bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
1099  // For each NSObject descendant having a +load method, this method is invoked
1100  // by the ObjC runtime before any of the static constructors is called.
1101  // Therefore we need to instrument such methods with a call to __asan_init
1102  // at the beginning in order to initialize our runtime before any access to
1103  // the shadow memory.
1104  // We cannot just ignore these methods, because they may call other
1105  // instrumented functions.
1106  if (F.getName().find(" load]") != std::string::npos) {
1107    IRBuilder<> IRB(F.begin()->begin());
1108    IRB.CreateCall(AsanInitFunction);
1109    return true;
1110  }
1111  return false;
1112}
1113
1114bool AddressSanitizer::runOnFunction(Function &F) {
1115  if (BL->isIn(F)) return false;
1116  if (&F == AsanCtorFunction) return false;
1117  if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
1118  DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
1119  initializeCallbacks(*F.getParent());
1120
1121  // If needed, insert __asan_init before checking for SanitizeAddress attr.
1122  maybeInsertAsanInitAtFunctionEntry(F);
1123
1124  if (!F.hasFnAttribute(Attribute::SanitizeAddress))
1125    return false;
1126
1127  if (!ClDebugFunc.empty() && ClDebugFunc != F.getName())
1128    return false;
1129
1130  // We want to instrument every address only once per basic block (unless there
1131  // are calls between uses).
1132  SmallSet<Value*, 16> TempsToInstrument;
1133  SmallVector<Instruction*, 16> ToInstrument;
1134  SmallVector<Instruction*, 8> NoReturnCalls;
1135  int NumAllocas = 0;
1136  bool IsWrite;
1137
1138  // Fill the set of memory operations to instrument.
1139  for (Function::iterator FI = F.begin(), FE = F.end();
1140       FI != FE; ++FI) {
1141    TempsToInstrument.clear();
1142    int NumInsnsPerBB = 0;
1143    for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
1144         BI != BE; ++BI) {
1145      if (LooksLikeCodeInBug11395(BI)) return false;
1146      if (Value *Addr = isInterestingMemoryAccess(BI, &IsWrite)) {
1147        if (ClOpt && ClOptSameTemp) {
1148          if (!TempsToInstrument.insert(Addr))
1149            continue;  // We've seen this temp in the current BB.
1150        }
1151      } else if (isa<MemIntrinsic>(BI) && ClMemIntrin) {
1152        // ok, take it.
1153      } else {
1154        if (isa<AllocaInst>(BI))
1155          NumAllocas++;
1156        CallSite CS(BI);
1157        if (CS) {
1158          // A call inside BB.
1159          TempsToInstrument.clear();
1160          if (CS.doesNotReturn())
1161            NoReturnCalls.push_back(CS.getInstruction());
1162        }
1163        continue;
1164      }
1165      ToInstrument.push_back(BI);
1166      NumInsnsPerBB++;
1167      if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB)
1168        break;
1169    }
1170  }
1171
1172  Function *UninstrumentedDuplicate = 0;
1173  bool LikelyToInstrument =
1174      !NoReturnCalls.empty() || !ToInstrument.empty() || (NumAllocas > 0);
1175  if (ClKeepUninstrumented && LikelyToInstrument) {
1176    ValueToValueMapTy VMap;
1177    UninstrumentedDuplicate = CloneFunction(&F, VMap, false);
1178    UninstrumentedDuplicate->removeFnAttr(Attribute::SanitizeAddress);
1179    UninstrumentedDuplicate->setName("NOASAN_" + F.getName());
1180    F.getParent()->getFunctionList().push_back(UninstrumentedDuplicate);
1181  }
1182
1183  // Instrument.
1184  int NumInstrumented = 0;
1185  for (size_t i = 0, n = ToInstrument.size(); i != n; i++) {
1186    Instruction *Inst = ToInstrument[i];
1187    if (ClDebugMin < 0 || ClDebugMax < 0 ||
1188        (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
1189      if (isInterestingMemoryAccess(Inst, &IsWrite))
1190        instrumentMop(Inst);
1191      else
1192        instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
1193    }
1194    NumInstrumented++;
1195  }
1196
1197  FunctionStackPoisoner FSP(F, *this);
1198  bool ChangedStack = FSP.runOnFunction();
1199
1200  // We must unpoison the stack before every NoReturn call (throw, _exit, etc).
1201  // See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
1202  for (size_t i = 0, n = NoReturnCalls.size(); i != n; i++) {
1203    Instruction *CI = NoReturnCalls[i];
1204    IRBuilder<> IRB(CI);
1205    IRB.CreateCall(AsanHandleNoReturnFunc);
1206  }
1207
1208  bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
1209  DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n");
1210
1211  if (ClKeepUninstrumented) {
1212    if (!res) {
1213      // No instrumentation is done, no need for the duplicate.
1214      if (UninstrumentedDuplicate)
1215        UninstrumentedDuplicate->eraseFromParent();
1216    } else {
1217      // The function was instrumented. We must have the duplicate.
1218      assert(UninstrumentedDuplicate);
1219      UninstrumentedDuplicate->setSection("NOASAN");
1220      assert(!F.hasSection());
1221      F.setSection("ASAN");
1222    }
1223  }
1224
1225  return res;
1226}
1227
1228static uint64_t ValueForPoison(uint64_t PoisonByte, size_t ShadowRedzoneSize) {
1229  if (ShadowRedzoneSize == 1) return PoisonByte;
1230  if (ShadowRedzoneSize == 2) return (PoisonByte << 8) + PoisonByte;
1231  if (ShadowRedzoneSize == 4)
1232    return (PoisonByte << 24) + (PoisonByte << 16) +
1233        (PoisonByte << 8) + (PoisonByte);
1234  llvm_unreachable("ShadowRedzoneSize is either 1, 2 or 4");
1235}
1236
1237static void PoisonShadowPartialRightRedzone(uint8_t *Shadow,
1238                                            size_t Size,
1239                                            size_t RZSize,
1240                                            size_t ShadowGranularity,
1241                                            uint8_t Magic) {
1242  for (size_t i = 0; i < RZSize;
1243       i+= ShadowGranularity, Shadow++) {
1244    if (i + ShadowGranularity <= Size) {
1245      *Shadow = 0;  // fully addressable
1246    } else if (i >= Size) {
1247      *Shadow = Magic;  // unaddressable
1248    } else {
1249      *Shadow = Size - i;  // first Size-i bytes are addressable
1250    }
1251  }
1252}
1253
1254// Workaround for bug 11395: we don't want to instrument stack in functions
1255// with large assembly blobs (32-bit only), otherwise reg alloc may crash.
1256// FIXME: remove once the bug 11395 is fixed.
1257bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
1258  if (LongSize != 32) return false;
1259  CallInst *CI = dyn_cast<CallInst>(I);
1260  if (!CI || !CI->isInlineAsm()) return false;
1261  if (CI->getNumArgOperands() <= 5) return false;
1262  // We have inline assembly with quite a few arguments.
1263  return true;
1264}
1265
1266void FunctionStackPoisoner::initializeCallbacks(Module &M) {
1267  IRBuilder<> IRB(*C);
1268  AsanStackMallocFunc = checkInterfaceFunction(M.getOrInsertFunction(
1269      kAsanStackMallocName, IntptrTy, IntptrTy, IntptrTy, NULL));
1270  AsanStackFreeFunc = checkInterfaceFunction(M.getOrInsertFunction(
1271      kAsanStackFreeName, IRB.getVoidTy(),
1272      IntptrTy, IntptrTy, IntptrTy, NULL));
1273  AsanPoisonStackMemoryFunc = checkInterfaceFunction(M.getOrInsertFunction(
1274      kAsanPoisonStackMemoryName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
1275  AsanUnpoisonStackMemoryFunc = checkInterfaceFunction(M.getOrInsertFunction(
1276      kAsanUnpoisonStackMemoryName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
1277}
1278
1279void FunctionStackPoisoner::poisonRedZones(
1280  const ArrayRef<AllocaInst*> &AllocaVec, IRBuilder<> IRB, Value *ShadowBase,
1281  bool DoPoison) {
1282  size_t ShadowRZSize = RedzoneSize() >> Mapping.Scale;
1283  assert(ShadowRZSize >= 1 && ShadowRZSize <= 4);
1284  Type *RZTy = Type::getIntNTy(*C, ShadowRZSize * 8);
1285  Type *RZPtrTy = PointerType::get(RZTy, 0);
1286
1287  Value *PoisonLeft  = ConstantInt::get(RZTy,
1288    ValueForPoison(DoPoison ? kAsanStackLeftRedzoneMagic : 0LL, ShadowRZSize));
1289  Value *PoisonMid   = ConstantInt::get(RZTy,
1290    ValueForPoison(DoPoison ? kAsanStackMidRedzoneMagic : 0LL, ShadowRZSize));
1291  Value *PoisonRight = ConstantInt::get(RZTy,
1292    ValueForPoison(DoPoison ? kAsanStackRightRedzoneMagic : 0LL, ShadowRZSize));
1293
1294  // poison the first red zone.
1295  IRB.CreateStore(PoisonLeft, IRB.CreateIntToPtr(ShadowBase, RZPtrTy));
1296
1297  // poison all other red zones.
1298  uint64_t Pos = RedzoneSize();
1299  for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
1300    AllocaInst *AI = AllocaVec[i];
1301    uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
1302    uint64_t AlignedSize = getAlignedAllocaSize(AI);
1303    assert(AlignedSize - SizeInBytes < RedzoneSize());
1304    Value *Ptr = NULL;
1305
1306    Pos += AlignedSize;
1307
1308    assert(ShadowBase->getType() == IntptrTy);
1309    if (SizeInBytes < AlignedSize) {
1310      // Poison the partial redzone at right
1311      Ptr = IRB.CreateAdd(
1312          ShadowBase, ConstantInt::get(IntptrTy,
1313                                       (Pos >> Mapping.Scale) - ShadowRZSize));
1314      size_t AddressableBytes = RedzoneSize() - (AlignedSize - SizeInBytes);
1315      uint32_t Poison = 0;
1316      if (DoPoison) {
1317        PoisonShadowPartialRightRedzone((uint8_t*)&Poison, AddressableBytes,
1318                                        RedzoneSize(),
1319                                        1ULL << Mapping.Scale,
1320                                        kAsanStackPartialRedzoneMagic);
1321        Poison =
1322            ASan.TD->isLittleEndian()
1323                ? support::endian::byte_swap<uint32_t, support::little>(Poison)
1324                : support::endian::byte_swap<uint32_t, support::big>(Poison);
1325      }
1326      Value *PartialPoison = ConstantInt::get(RZTy, Poison);
1327      IRB.CreateStore(PartialPoison, IRB.CreateIntToPtr(Ptr, RZPtrTy));
1328    }
1329
1330    // Poison the full redzone at right.
1331    Ptr = IRB.CreateAdd(ShadowBase,
1332                        ConstantInt::get(IntptrTy, Pos >> Mapping.Scale));
1333    bool LastAlloca = (i == AllocaVec.size() - 1);
1334    Value *Poison = LastAlloca ? PoisonRight : PoisonMid;
1335    IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, RZPtrTy));
1336
1337    Pos += RedzoneSize();
1338  }
1339}
1340
1341void FunctionStackPoisoner::poisonStack() {
1342  uint64_t LocalStackSize = TotalStackSize +
1343                            (AllocaVec.size() + 1) * RedzoneSize();
1344
1345  bool DoStackMalloc = ASan.CheckUseAfterReturn
1346      && LocalStackSize <= kMaxStackMallocSize;
1347
1348  assert(AllocaVec.size() > 0);
1349  Instruction *InsBefore = AllocaVec[0];
1350  IRBuilder<> IRB(InsBefore);
1351
1352
1353  Type *ByteArrayTy = ArrayType::get(IRB.getInt8Ty(), LocalStackSize);
1354  AllocaInst *MyAlloca =
1355      new AllocaInst(ByteArrayTy, "MyAlloca", InsBefore);
1356  if (ClRealignStack && StackAlignment < RedzoneSize())
1357    StackAlignment = RedzoneSize();
1358  MyAlloca->setAlignment(StackAlignment);
1359  assert(MyAlloca->isStaticAlloca());
1360  Value *OrigStackBase = IRB.CreatePointerCast(MyAlloca, IntptrTy);
1361  Value *LocalStackBase = OrigStackBase;
1362
1363  if (DoStackMalloc) {
1364    LocalStackBase = IRB.CreateCall2(AsanStackMallocFunc,
1365        ConstantInt::get(IntptrTy, LocalStackSize), OrigStackBase);
1366  }
1367
1368  // This string will be parsed by the run-time (DescribeAddressIfStack).
1369  SmallString<2048> StackDescriptionStorage;
1370  raw_svector_ostream StackDescription(StackDescriptionStorage);
1371  StackDescription << AllocaVec.size() << " ";
1372
1373  // Insert poison calls for lifetime intrinsics for alloca.
1374  bool HavePoisonedAllocas = false;
1375  for (size_t i = 0, n = AllocaPoisonCallVec.size(); i < n; i++) {
1376    const AllocaPoisonCall &APC = AllocaPoisonCallVec[i];
1377    IntrinsicInst *II = APC.InsBefore;
1378    AllocaInst *AI = findAllocaForValue(II->getArgOperand(1));
1379    assert(AI);
1380    IRBuilder<> IRB(II);
1381    poisonAlloca(AI, APC.Size, IRB, APC.DoPoison);
1382    HavePoisonedAllocas |= APC.DoPoison;
1383  }
1384
1385  uint64_t Pos = RedzoneSize();
1386  // Replace Alloca instructions with base+offset.
1387  for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
1388    AllocaInst *AI = AllocaVec[i];
1389    uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
1390    StringRef Name = AI->getName();
1391    StackDescription << Pos << " " << SizeInBytes << " "
1392                     << Name.size() << " " << Name << " ";
1393    uint64_t AlignedSize = getAlignedAllocaSize(AI);
1394    assert((AlignedSize % RedzoneSize()) == 0);
1395    Value *NewAllocaPtr = IRB.CreateIntToPtr(
1396            IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Pos)),
1397            AI->getType());
1398    replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB);
1399    AI->replaceAllUsesWith(NewAllocaPtr);
1400    Pos += AlignedSize + RedzoneSize();
1401  }
1402  assert(Pos == LocalStackSize);
1403
1404  // The left-most redzone has enough space for at least 4 pointers.
1405  // Write the Magic value to redzone[0].
1406  Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
1407  IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
1408                  BasePlus0);
1409  // Write the frame description constant to redzone[1].
1410  Value *BasePlus1 = IRB.CreateIntToPtr(
1411    IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, ASan.LongSize/8)),
1412    IntptrPtrTy);
1413  GlobalVariable *StackDescriptionGlobal =
1414      createPrivateGlobalForString(*F.getParent(), StackDescription.str());
1415  Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal,
1416                                             IntptrTy);
1417  IRB.CreateStore(Description, BasePlus1);
1418  // Write the PC to redzone[2].
1419  Value *BasePlus2 = IRB.CreateIntToPtr(
1420    IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy,
1421                                                   2 * ASan.LongSize/8)),
1422    IntptrPtrTy);
1423  IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
1424
1425  // Poison the stack redzones at the entry.
1426  Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
1427  poisonRedZones(AllocaVec, IRB, ShadowBase, true);
1428
1429  // Unpoison the stack before all ret instructions.
1430  for (size_t i = 0, n = RetVec.size(); i < n; i++) {
1431    Instruction *Ret = RetVec[i];
1432    IRBuilder<> IRBRet(Ret);
1433    // Mark the current frame as retired.
1434    IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
1435                       BasePlus0);
1436    // Unpoison the stack.
1437    poisonRedZones(AllocaVec, IRBRet, ShadowBase, false);
1438    if (DoStackMalloc) {
1439      // In use-after-return mode, mark the whole stack frame unaddressable.
1440      IRBRet.CreateCall3(AsanStackFreeFunc, LocalStackBase,
1441                         ConstantInt::get(IntptrTy, LocalStackSize),
1442                         OrigStackBase);
1443    } else if (HavePoisonedAllocas) {
1444      // If we poisoned some allocas in llvm.lifetime analysis,
1445      // unpoison whole stack frame now.
1446      assert(LocalStackBase == OrigStackBase);
1447      poisonAlloca(LocalStackBase, LocalStackSize, IRBRet, false);
1448    }
1449  }
1450
1451  // We are done. Remove the old unused alloca instructions.
1452  for (size_t i = 0, n = AllocaVec.size(); i < n; i++)
1453    AllocaVec[i]->eraseFromParent();
1454}
1455
1456void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size,
1457                                         IRBuilder<> IRB, bool DoPoison) {
1458  // For now just insert the call to ASan runtime.
1459  Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy);
1460  Value *SizeArg = ConstantInt::get(IntptrTy, Size);
1461  IRB.CreateCall2(DoPoison ? AsanPoisonStackMemoryFunc
1462                           : AsanUnpoisonStackMemoryFunc,
1463                  AddrArg, SizeArg);
1464}
1465
1466// Handling llvm.lifetime intrinsics for a given %alloca:
1467// (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca.
1468// (2) if %size is constant, poison memory for llvm.lifetime.end (to detect
1469//     invalid accesses) and unpoison it for llvm.lifetime.start (the memory
1470//     could be poisoned by previous llvm.lifetime.end instruction, as the
1471//     variable may go in and out of scope several times, e.g. in loops).
1472// (3) if we poisoned at least one %alloca in a function,
1473//     unpoison the whole stack frame at function exit.
1474
1475AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
1476  if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
1477    // We're intested only in allocas we can handle.
1478    return isInterestingAlloca(*AI) ? AI : 0;
1479  // See if we've already calculated (or started to calculate) alloca for a
1480  // given value.
1481  AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
1482  if (I != AllocaForValue.end())
1483    return I->second;
1484  // Store 0 while we're calculating alloca for value V to avoid
1485  // infinite recursion if the value references itself.
1486  AllocaForValue[V] = 0;
1487  AllocaInst *Res = 0;
1488  if (CastInst *CI = dyn_cast<CastInst>(V))
1489    Res = findAllocaForValue(CI->getOperand(0));
1490  else if (PHINode *PN = dyn_cast<PHINode>(V)) {
1491    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1492      Value *IncValue = PN->getIncomingValue(i);
1493      // Allow self-referencing phi-nodes.
1494      if (IncValue == PN) continue;
1495      AllocaInst *IncValueAI = findAllocaForValue(IncValue);
1496      // AI for incoming values should exist and should all be equal.
1497      if (IncValueAI == 0 || (Res != 0 && IncValueAI != Res))
1498        return 0;
1499      Res = IncValueAI;
1500    }
1501  }
1502  if (Res != 0)
1503    AllocaForValue[V] = Res;
1504  return Res;
1505}
1506