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 #include "llvm/ADT/ArrayRef.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/DepthFirstIterator.h"
19 #include "llvm/ADT/SetVector.h"
20 #include "llvm/ADT/SmallSet.h"
21 #include "llvm/ADT/SmallVector.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/ADT/StringExtras.h"
24 #include "llvm/ADT/Triple.h"
25 #include "llvm/Analysis/MemoryBuiltins.h"
26 #include "llvm/Analysis/TargetLibraryInfo.h"
27 #include "llvm/Analysis/ValueTracking.h"
28 #include "llvm/IR/CallSite.h"
29 #include "llvm/IR/DIBuilder.h"
30 #include "llvm/IR/DataLayout.h"
31 #include "llvm/IR/Dominators.h"
32 #include "llvm/IR/Function.h"
33 #include "llvm/IR/IRBuilder.h"
34 #include "llvm/IR/InlineAsm.h"
35 #include "llvm/IR/InstVisitor.h"
36 #include "llvm/IR/IntrinsicInst.h"
37 #include "llvm/IR/LLVMContext.h"
38 #include "llvm/IR/MDBuilder.h"
39 #include "llvm/IR/Module.h"
40 #include "llvm/IR/Type.h"
41 #include "llvm/MC/MCSectionMachO.h"
42 #include "llvm/Support/CommandLine.h"
43 #include "llvm/Support/DataTypes.h"
44 #include "llvm/Support/Debug.h"
45 #include "llvm/Support/Endian.h"
46 #include "llvm/Support/SwapByteOrder.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include "llvm/Transforms/Instrumentation.h"
49 #include "llvm/Transforms/Scalar.h"
50 #include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
51 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
52 #include "llvm/Transforms/Utils/Cloning.h"
53 #include "llvm/Transforms/Utils/Local.h"
54 #include "llvm/Transforms/Utils/ModuleUtils.h"
55 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
56 #include <algorithm>
57 #include <iomanip>
58 #include <limits>
59 #include <sstream>
60 #include <string>
61 #include <system_error>
62 
63 using namespace llvm;
64 
65 #define DEBUG_TYPE "asan"
66 
67 static const uint64_t kDefaultShadowScale = 3;
68 static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
69 static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
70 static const uint64_t kDynamicShadowSentinel = ~(uint64_t)0;
71 static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
72 static const uint64_t kIOSSimShadowOffset32 = 1ULL << 30;
73 static const uint64_t kIOSSimShadowOffset64 = kDefaultShadowOffset64;
74 static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000;  // < 2G.
75 static const uint64_t kLinuxKasan_ShadowOffset64 = 0xdffffc0000000000;
76 static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
77 static const uint64_t kSystemZ_ShadowOffset64 = 1ULL << 52;
78 static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000;
79 static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 37;
80 static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36;
81 static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
82 static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
83 static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
84 // The shadow memory space is dynamically allocated.
85 static const uint64_t kWindowsShadowOffset64 = kDynamicShadowSentinel;
86 
87 static const size_t kMinStackMallocSize = 1 << 6;   // 64B
88 static const size_t kMaxStackMallocSize = 1 << 16;  // 64K
89 static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
90 static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
91 
92 static const char *const kAsanModuleCtorName = "asan.module_ctor";
93 static const char *const kAsanModuleDtorName = "asan.module_dtor";
94 static const uint64_t kAsanCtorAndDtorPriority = 1;
95 static const char *const kAsanReportErrorTemplate = "__asan_report_";
96 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
97 static const char *const kAsanUnregisterGlobalsName =
98     "__asan_unregister_globals";
99 static const char *const kAsanRegisterImageGlobalsName =
100   "__asan_register_image_globals";
101 static const char *const kAsanUnregisterImageGlobalsName =
102   "__asan_unregister_image_globals";
103 static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
104 static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
105 static const char *const kAsanInitName = "__asan_init";
106 static const char *const kAsanVersionCheckName =
107     "__asan_version_mismatch_check_v8";
108 static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
109 static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
110 static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
111 static const int kMaxAsanStackMallocSizeClass = 10;
112 static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
113 static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
114 static const char *const kAsanGenPrefix = "__asan_gen_";
115 static const char *const kODRGenPrefix = "__odr_asan_gen_";
116 static const char *const kSanCovGenPrefix = "__sancov_gen_";
117 static const char *const kAsanSetShadowPrefix = "__asan_set_shadow_";
118 static const char *const kAsanPoisonStackMemoryName =
119     "__asan_poison_stack_memory";
120 static const char *const kAsanUnpoisonStackMemoryName =
121     "__asan_unpoison_stack_memory";
122 static const char *const kAsanGlobalsRegisteredFlagName =
123     "__asan_globals_registered";
124 
125 static const char *const kAsanOptionDetectUseAfterReturn =
126     "__asan_option_detect_stack_use_after_return";
127 
128 static const char *const kAsanShadowMemoryDynamicAddress =
129     "__asan_shadow_memory_dynamic_address";
130 
131 static const char *const kAsanAllocaPoison = "__asan_alloca_poison";
132 static const char *const kAsanAllocasUnpoison = "__asan_allocas_unpoison";
133 
134 // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
135 static const size_t kNumberOfAccessSizes = 5;
136 
137 static const unsigned kAllocaRzSize = 32;
138 
139 // Command-line flags.
140 static cl::opt<bool> ClEnableKasan(
141     "asan-kernel", cl::desc("Enable KernelAddressSanitizer instrumentation"),
142     cl::Hidden, cl::init(false));
143 static cl::opt<bool> ClRecover(
144     "asan-recover",
145     cl::desc("Enable recovery mode (continue-after-error)."),
146     cl::Hidden, cl::init(false));
147 
148 // This flag may need to be replaced with -f[no-]asan-reads.
149 static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
150                                        cl::desc("instrument read instructions"),
151                                        cl::Hidden, cl::init(true));
152 static cl::opt<bool> ClInstrumentWrites(
153     "asan-instrument-writes", cl::desc("instrument write instructions"),
154     cl::Hidden, cl::init(true));
155 static cl::opt<bool> ClInstrumentAtomics(
156     "asan-instrument-atomics",
157     cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden,
158     cl::init(true));
159 static cl::opt<bool> ClAlwaysSlowPath(
160     "asan-always-slow-path",
161     cl::desc("use instrumentation with slow path for all accesses"), cl::Hidden,
162     cl::init(false));
163 static cl::opt<bool> ClForceDynamicShadow(
164     "asan-force-dynamic-shadow",
165     cl::desc("Load shadow address into a local variable for each function"),
166     cl::Hidden, cl::init(false));
167 
168 // This flag limits the number of instructions to be instrumented
169 // in any given BB. Normally, this should be set to unlimited (INT_MAX),
170 // but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary
171 // set it to 10000.
172 static cl::opt<int> ClMaxInsnsToInstrumentPerBB(
173     "asan-max-ins-per-bb", cl::init(10000),
174     cl::desc("maximal number of instructions to instrument in any given BB"),
175     cl::Hidden);
176 // This flag may need to be replaced with -f[no]asan-stack.
177 static cl::opt<bool> ClStack("asan-stack", cl::desc("Handle stack memory"),
178                              cl::Hidden, cl::init(true));
179 static cl::opt<uint32_t> ClMaxInlinePoisoningSize(
180     "asan-max-inline-poisoning-size",
181     cl::desc(
182         "Inline shadow poisoning for blocks up to the given size in bytes."),
183     cl::Hidden, cl::init(64));
184 static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
185                                       cl::desc("Check stack-use-after-return"),
186                                       cl::Hidden, cl::init(true));
187 static cl::opt<bool> ClUseAfterScope("asan-use-after-scope",
188                                      cl::desc("Check stack-use-after-scope"),
189                                      cl::Hidden, cl::init(false));
190 // This flag may need to be replaced with -f[no]asan-globals.
191 static cl::opt<bool> ClGlobals("asan-globals",
192                                cl::desc("Handle global objects"), cl::Hidden,
193                                cl::init(true));
194 static cl::opt<bool> ClInitializers("asan-initialization-order",
195                                     cl::desc("Handle C++ initializer order"),
196                                     cl::Hidden, cl::init(true));
197 static cl::opt<bool> ClInvalidPointerPairs(
198     "asan-detect-invalid-pointer-pair",
199     cl::desc("Instrument <, <=, >, >=, - with pointer operands"), cl::Hidden,
200     cl::init(false));
201 static cl::opt<unsigned> ClRealignStack(
202     "asan-realign-stack",
203     cl::desc("Realign stack to the value of this flag (power of two)"),
204     cl::Hidden, cl::init(32));
205 static cl::opt<int> ClInstrumentationWithCallsThreshold(
206     "asan-instrumentation-with-call-threshold",
207     cl::desc(
208         "If the function being instrumented contains more than "
209         "this number of memory accesses, use callbacks instead of "
210         "inline checks (-1 means never use callbacks)."),
211     cl::Hidden, cl::init(7000));
212 static cl::opt<std::string> ClMemoryAccessCallbackPrefix(
213     "asan-memory-access-callback-prefix",
214     cl::desc("Prefix for memory access callbacks"), cl::Hidden,
215     cl::init("__asan_"));
216 static cl::opt<bool>
217     ClInstrumentDynamicAllocas("asan-instrument-dynamic-allocas",
218                                cl::desc("instrument dynamic allocas"),
219                                cl::Hidden, cl::init(true));
220 static cl::opt<bool> ClSkipPromotableAllocas(
221     "asan-skip-promotable-allocas",
222     cl::desc("Do not instrument promotable allocas"), cl::Hidden,
223     cl::init(true));
224 
225 // These flags allow to change the shadow mapping.
226 // The shadow mapping looks like
227 //    Shadow = (Mem >> scale) + offset
228 static cl::opt<int> ClMappingScale("asan-mapping-scale",
229                                    cl::desc("scale of asan shadow mapping"),
230                                    cl::Hidden, cl::init(0));
231 static cl::opt<unsigned long long> ClMappingOffset(
232     "asan-mapping-offset",
233     cl::desc("offset of asan shadow mapping [EXPERIMENTAL]"), cl::Hidden,
234     cl::init(0));
235 
236 // Optimization flags. Not user visible, used mostly for testing
237 // and benchmarking the tool.
238 static cl::opt<bool> ClOpt("asan-opt", cl::desc("Optimize instrumentation"),
239                            cl::Hidden, cl::init(true));
240 static cl::opt<bool> ClOptSameTemp(
241     "asan-opt-same-temp", cl::desc("Instrument the same temp just once"),
242     cl::Hidden, cl::init(true));
243 static cl::opt<bool> ClOptGlobals("asan-opt-globals",
244                                   cl::desc("Don't instrument scalar globals"),
245                                   cl::Hidden, cl::init(true));
246 static cl::opt<bool> ClOptStack(
247     "asan-opt-stack", cl::desc("Don't instrument scalar stack variables"),
248     cl::Hidden, cl::init(false));
249 
250 static cl::opt<bool> ClDynamicAllocaStack(
251     "asan-stack-dynamic-alloca",
252     cl::desc("Use dynamic alloca to represent stack variables"), cl::Hidden,
253     cl::init(true));
254 
255 static cl::opt<uint32_t> ClForceExperiment(
256     "asan-force-experiment",
257     cl::desc("Force optimization experiment (for testing)"), cl::Hidden,
258     cl::init(0));
259 
260 static cl::opt<bool>
261     ClUsePrivateAliasForGlobals("asan-use-private-alias",
262                                 cl::desc("Use private aliases for global"
263                                          " variables"),
264                                 cl::Hidden, cl::init(false));
265 
266 static cl::opt<bool>
267     ClUseMachOGlobalsSection("asan-globals-live-support",
268                              cl::desc("Use linker features to support dead "
269                                       "code stripping of globals "
270                                       "(Mach-O only)"),
271                              cl::Hidden, cl::init(true));
272 
273 // Debug flags.
274 static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
275                             cl::init(0));
276 static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
277                                  cl::Hidden, cl::init(0));
278 static cl::opt<std::string> ClDebugFunc("asan-debug-func", cl::Hidden,
279                                         cl::desc("Debug func"));
280 static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
281                                cl::Hidden, cl::init(-1));
282 static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug max inst"),
283                                cl::Hidden, cl::init(-1));
284 
285 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
286 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
287 STATISTIC(NumOptimizedAccessesToGlobalVar,
288           "Number of optimized accesses to global vars");
289 STATISTIC(NumOptimizedAccessesToStackVar,
290           "Number of optimized accesses to stack vars");
291 
292 namespace {
293 /// Frontend-provided metadata for source location.
294 struct LocationMetadata {
295   StringRef Filename;
296   int LineNo;
297   int ColumnNo;
298 
299   LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {}
300 
301   bool empty() const { return Filename.empty(); }
302 
303   void parse(MDNode *MDN) {
304     assert(MDN->getNumOperands() == 3);
305     MDString *DIFilename = cast<MDString>(MDN->getOperand(0));
306     Filename = DIFilename->getString();
307     LineNo =
308         mdconst::extract<ConstantInt>(MDN->getOperand(1))->getLimitedValue();
309     ColumnNo =
310         mdconst::extract<ConstantInt>(MDN->getOperand(2))->getLimitedValue();
311   }
312 };
313 
314 /// Frontend-provided metadata for global variables.
315 class GlobalsMetadata {
316  public:
317   struct Entry {
318     Entry() : SourceLoc(), Name(), IsDynInit(false), IsBlacklisted(false) {}
319     LocationMetadata SourceLoc;
320     StringRef Name;
321     bool IsDynInit;
322     bool IsBlacklisted;
323   };
324 
325   GlobalsMetadata() : inited_(false) {}
326 
327   void reset() {
328     inited_ = false;
329     Entries.clear();
330   }
331 
332   void init(Module &M) {
333     assert(!inited_);
334     inited_ = true;
335     NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
336     if (!Globals) return;
337     for (auto MDN : Globals->operands()) {
338       // Metadata node contains the global and the fields of "Entry".
339       assert(MDN->getNumOperands() == 5);
340       auto *GV = mdconst::extract_or_null<GlobalVariable>(MDN->getOperand(0));
341       // The optimizer may optimize away a global entirely.
342       if (!GV) continue;
343       // We can already have an entry for GV if it was merged with another
344       // global.
345       Entry &E = Entries[GV];
346       if (auto *Loc = cast_or_null<MDNode>(MDN->getOperand(1)))
347         E.SourceLoc.parse(Loc);
348       if (auto *Name = cast_or_null<MDString>(MDN->getOperand(2)))
349         E.Name = Name->getString();
350       ConstantInt *IsDynInit =
351           mdconst::extract<ConstantInt>(MDN->getOperand(3));
352       E.IsDynInit |= IsDynInit->isOne();
353       ConstantInt *IsBlacklisted =
354           mdconst::extract<ConstantInt>(MDN->getOperand(4));
355       E.IsBlacklisted |= IsBlacklisted->isOne();
356     }
357   }
358 
359   /// Returns metadata entry for a given global.
360   Entry get(GlobalVariable *G) const {
361     auto Pos = Entries.find(G);
362     return (Pos != Entries.end()) ? Pos->second : Entry();
363   }
364 
365  private:
366   bool inited_;
367   DenseMap<GlobalVariable *, Entry> Entries;
368 };
369 
370 /// This struct defines the shadow mapping using the rule:
371 ///   shadow = (mem >> Scale) ADD-or-OR Offset.
372 struct ShadowMapping {
373   int Scale;
374   uint64_t Offset;
375   bool OrShadowOffset;
376 };
377 
378 static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize,
379                                       bool IsKasan) {
380   bool IsAndroid = TargetTriple.isAndroid();
381   bool IsIOS = TargetTriple.isiOS() || TargetTriple.isWatchOS();
382   bool IsFreeBSD = TargetTriple.isOSFreeBSD();
383   bool IsLinux = TargetTriple.isOSLinux();
384   bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 ||
385                  TargetTriple.getArch() == llvm::Triple::ppc64le;
386   bool IsSystemZ = TargetTriple.getArch() == llvm::Triple::systemz;
387   bool IsX86 = TargetTriple.getArch() == llvm::Triple::x86;
388   bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
389   bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips ||
390                   TargetTriple.getArch() == llvm::Triple::mipsel;
391   bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 ||
392                   TargetTriple.getArch() == llvm::Triple::mips64el;
393   bool IsAArch64 = TargetTriple.getArch() == llvm::Triple::aarch64;
394   bool IsWindows = TargetTriple.isOSWindows();
395 
396   ShadowMapping Mapping;
397 
398   if (LongSize == 32) {
399     // Android is always PIE, which means that the beginning of the address
400     // space is always available.
401     if (IsAndroid)
402       Mapping.Offset = 0;
403     else if (IsMIPS32)
404       Mapping.Offset = kMIPS32_ShadowOffset32;
405     else if (IsFreeBSD)
406       Mapping.Offset = kFreeBSD_ShadowOffset32;
407     else if (IsIOS)
408       // If we're targeting iOS and x86, the binary is built for iOS simulator.
409       Mapping.Offset = IsX86 ? kIOSSimShadowOffset32 : kIOSShadowOffset32;
410     else if (IsWindows)
411       Mapping.Offset = kWindowsShadowOffset32;
412     else
413       Mapping.Offset = kDefaultShadowOffset32;
414   } else {  // LongSize == 64
415     if (IsPPC64)
416       Mapping.Offset = kPPC64_ShadowOffset64;
417     else if (IsSystemZ)
418       Mapping.Offset = kSystemZ_ShadowOffset64;
419     else if (IsFreeBSD)
420       Mapping.Offset = kFreeBSD_ShadowOffset64;
421     else if (IsLinux && IsX86_64) {
422       if (IsKasan)
423         Mapping.Offset = kLinuxKasan_ShadowOffset64;
424       else
425         Mapping.Offset = kSmallX86_64ShadowOffset;
426     } else if (IsWindows && IsX86_64) {
427       Mapping.Offset = kWindowsShadowOffset64;
428     } else if (IsMIPS64)
429       Mapping.Offset = kMIPS64_ShadowOffset64;
430     else if (IsIOS)
431       // If we're targeting iOS and x86, the binary is built for iOS simulator.
432       // We are using dynamic shadow offset on the 64-bit devices.
433       Mapping.Offset =
434         IsX86_64 ? kIOSSimShadowOffset64 : kDynamicShadowSentinel;
435     else if (IsAArch64)
436       Mapping.Offset = kAArch64_ShadowOffset64;
437     else
438       Mapping.Offset = kDefaultShadowOffset64;
439   }
440 
441   if (ClForceDynamicShadow) {
442     Mapping.Offset = kDynamicShadowSentinel;
443   }
444 
445   Mapping.Scale = kDefaultShadowScale;
446   if (ClMappingScale.getNumOccurrences() > 0) {
447     Mapping.Scale = ClMappingScale;
448   }
449 
450   if (ClMappingOffset.getNumOccurrences() > 0) {
451     Mapping.Offset = ClMappingOffset;
452   }
453 
454   // OR-ing shadow offset if more efficient (at least on x86) if the offset
455   // is a power of two, but on ppc64 we have to use add since the shadow
456   // offset is not necessary 1/8-th of the address space.  On SystemZ,
457   // we could OR the constant in a single instruction, but it's more
458   // efficient to load it once and use indexed addressing.
459   Mapping.OrShadowOffset = !IsAArch64 && !IsPPC64 && !IsSystemZ
460                            && !(Mapping.Offset & (Mapping.Offset - 1))
461                            && Mapping.Offset != kDynamicShadowSentinel;
462 
463   return Mapping;
464 }
465 
466 static size_t RedzoneSizeForScale(int MappingScale) {
467   // Redzone used for stack and globals is at least 32 bytes.
468   // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
469   return std::max(32U, 1U << MappingScale);
470 }
471 
472 /// AddressSanitizer: instrument the code in module to find memory bugs.
473 struct AddressSanitizer : public FunctionPass {
474   explicit AddressSanitizer(bool CompileKernel = false, bool Recover = false,
475                             bool UseAfterScope = false)
476       : FunctionPass(ID), CompileKernel(CompileKernel || ClEnableKasan),
477         Recover(Recover || ClRecover),
478         UseAfterScope(UseAfterScope || ClUseAfterScope),
479         LocalDynamicShadow(nullptr) {
480     initializeAddressSanitizerPass(*PassRegistry::getPassRegistry());
481   }
482   StringRef getPassName() const override {
483     return "AddressSanitizerFunctionPass";
484   }
485   void getAnalysisUsage(AnalysisUsage &AU) const override {
486     AU.addRequired<DominatorTreeWrapperPass>();
487     AU.addRequired<TargetLibraryInfoWrapperPass>();
488   }
489   uint64_t getAllocaSizeInBytes(const AllocaInst &AI) const {
490     uint64_t ArraySize = 1;
491     if (AI.isArrayAllocation()) {
492       const ConstantInt *CI = dyn_cast<ConstantInt>(AI.getArraySize());
493       assert(CI && "non-constant array size");
494       ArraySize = CI->getZExtValue();
495     }
496     Type *Ty = AI.getAllocatedType();
497     uint64_t SizeInBytes =
498         AI.getModule()->getDataLayout().getTypeAllocSize(Ty);
499     return SizeInBytes * ArraySize;
500   }
501   /// Check if we want (and can) handle this alloca.
502   bool isInterestingAlloca(const AllocaInst &AI);
503 
504   /// If it is an interesting memory access, return the PointerOperand
505   /// and set IsWrite/Alignment. Otherwise return nullptr.
506   /// MaybeMask is an output parameter for the mask Value, if we're looking at a
507   /// masked load/store.
508   Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
509                                    uint64_t *TypeSize, unsigned *Alignment,
510                                    Value **MaybeMask = nullptr);
511   void instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, Instruction *I,
512                      bool UseCalls, const DataLayout &DL);
513   void instrumentPointerComparisonOrSubtraction(Instruction *I);
514   void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
515                          Value *Addr, uint32_t TypeSize, bool IsWrite,
516                          Value *SizeArgument, bool UseCalls, uint32_t Exp);
517   void instrumentUnusualSizeOrAlignment(Instruction *I, Value *Addr,
518                                         uint32_t TypeSize, bool IsWrite,
519                                         Value *SizeArgument, bool UseCalls,
520                                         uint32_t Exp);
521   Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
522                            Value *ShadowValue, uint32_t TypeSize);
523   Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
524                                  bool IsWrite, size_t AccessSizeIndex,
525                                  Value *SizeArgument, uint32_t Exp);
526   void instrumentMemIntrinsic(MemIntrinsic *MI);
527   Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
528   bool runOnFunction(Function &F) override;
529   bool maybeInsertAsanInitAtFunctionEntry(Function &F);
530   void maybeInsertDynamicShadowAtFunctionEntry(Function &F);
531   void markEscapedLocalAllocas(Function &F);
532   bool doInitialization(Module &M) override;
533   bool doFinalization(Module &M) override;
534   static char ID;  // Pass identification, replacement for typeid
535 
536   DominatorTree &getDominatorTree() const { return *DT; }
537 
538  private:
539   void initializeCallbacks(Module &M);
540 
541   bool LooksLikeCodeInBug11395(Instruction *I);
542   bool GlobalIsLinkerInitialized(GlobalVariable *G);
543   bool isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis, Value *Addr,
544                     uint64_t TypeSize) const;
545 
546   /// Helper to cleanup per-function state.
547   struct FunctionStateRAII {
548     AddressSanitizer *Pass;
549     FunctionStateRAII(AddressSanitizer *Pass) : Pass(Pass) {
550       assert(Pass->ProcessedAllocas.empty() &&
551              "last pass forgot to clear cache");
552       assert(!Pass->LocalDynamicShadow);
553     }
554     ~FunctionStateRAII() {
555       Pass->LocalDynamicShadow = nullptr;
556       Pass->ProcessedAllocas.clear();
557     }
558   };
559 
560   LLVMContext *C;
561   Triple TargetTriple;
562   int LongSize;
563   bool CompileKernel;
564   bool Recover;
565   bool UseAfterScope;
566   Type *IntptrTy;
567   ShadowMapping Mapping;
568   DominatorTree *DT;
569   Function *AsanCtorFunction = nullptr;
570   Function *AsanInitFunction = nullptr;
571   Function *AsanHandleNoReturnFunc;
572   Function *AsanPtrCmpFunction, *AsanPtrSubFunction;
573   // This array is indexed by AccessIsWrite, Experiment and log2(AccessSize).
574   Function *AsanErrorCallback[2][2][kNumberOfAccessSizes];
575   Function *AsanMemoryAccessCallback[2][2][kNumberOfAccessSizes];
576   // This array is indexed by AccessIsWrite and Experiment.
577   Function *AsanErrorCallbackSized[2][2];
578   Function *AsanMemoryAccessCallbackSized[2][2];
579   Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
580   InlineAsm *EmptyAsm;
581   Value *LocalDynamicShadow;
582   GlobalsMetadata GlobalsMD;
583   DenseMap<const AllocaInst *, bool> ProcessedAllocas;
584 
585   friend struct FunctionStackPoisoner;
586 };
587 
588 class AddressSanitizerModule : public ModulePass {
589  public:
590   explicit AddressSanitizerModule(bool CompileKernel = false,
591                                   bool Recover = false)
592       : ModulePass(ID), CompileKernel(CompileKernel || ClEnableKasan),
593         Recover(Recover || ClRecover) {}
594   bool runOnModule(Module &M) override;
595   static char ID;  // Pass identification, replacement for typeid
596   StringRef getPassName() const override { return "AddressSanitizerModule"; }
597 
598 private:
599   void initializeCallbacks(Module &M);
600 
601   bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
602   bool ShouldInstrumentGlobal(GlobalVariable *G);
603   bool ShouldUseMachOGlobalsSection() const;
604   StringRef getGlobalMetadataSection() const;
605   void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
606   void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
607   size_t MinRedzoneSizeForGlobal() const {
608     return RedzoneSizeForScale(Mapping.Scale);
609   }
610 
611   GlobalsMetadata GlobalsMD;
612   bool CompileKernel;
613   bool Recover;
614   Type *IntptrTy;
615   LLVMContext *C;
616   Triple TargetTriple;
617   ShadowMapping Mapping;
618   Function *AsanPoisonGlobals;
619   Function *AsanUnpoisonGlobals;
620   Function *AsanRegisterGlobals;
621   Function *AsanUnregisterGlobals;
622   Function *AsanRegisterImageGlobals;
623   Function *AsanUnregisterImageGlobals;
624 };
625 
626 // Stack poisoning does not play well with exception handling.
627 // When an exception is thrown, we essentially bypass the code
628 // that unpoisones the stack. This is why the run-time library has
629 // to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
630 // stack in the interceptor. This however does not work inside the
631 // actual function which catches the exception. Most likely because the
632 // compiler hoists the load of the shadow value somewhere too high.
633 // This causes asan to report a non-existing bug on 453.povray.
634 // It sounds like an LLVM bug.
635 struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
636   Function &F;
637   AddressSanitizer &ASan;
638   DIBuilder DIB;
639   LLVMContext *C;
640   Type *IntptrTy;
641   Type *IntptrPtrTy;
642   ShadowMapping Mapping;
643 
644   SmallVector<AllocaInst *, 16> AllocaVec;
645   SmallVector<AllocaInst *, 16> StaticAllocasToMoveUp;
646   SmallVector<Instruction *, 8> RetVec;
647   unsigned StackAlignment;
648 
649   Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
650       *AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
651   Function *AsanSetShadowFunc[0x100] = {};
652   Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc;
653   Function *AsanAllocaPoisonFunc, *AsanAllocasUnpoisonFunc;
654 
655   // Stores a place and arguments of poisoning/unpoisoning call for alloca.
656   struct AllocaPoisonCall {
657     IntrinsicInst *InsBefore;
658     AllocaInst *AI;
659     uint64_t Size;
660     bool DoPoison;
661   };
662   SmallVector<AllocaPoisonCall, 8> DynamicAllocaPoisonCallVec;
663   SmallVector<AllocaPoisonCall, 8> StaticAllocaPoisonCallVec;
664 
665   SmallVector<AllocaInst *, 1> DynamicAllocaVec;
666   SmallVector<IntrinsicInst *, 1> StackRestoreVec;
667   AllocaInst *DynamicAllocaLayout = nullptr;
668   IntrinsicInst *LocalEscapeCall = nullptr;
669 
670   // Maps Value to an AllocaInst from which the Value is originated.
671   typedef DenseMap<Value *, AllocaInst *> AllocaForValueMapTy;
672   AllocaForValueMapTy AllocaForValue;
673 
674   bool HasNonEmptyInlineAsm = false;
675   bool HasReturnsTwiceCall = false;
676   std::unique_ptr<CallInst> EmptyInlineAsm;
677 
678   FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
679       : F(F),
680         ASan(ASan),
681         DIB(*F.getParent(), /*AllowUnresolved*/ false),
682         C(ASan.C),
683         IntptrTy(ASan.IntptrTy),
684         IntptrPtrTy(PointerType::get(IntptrTy, 0)),
685         Mapping(ASan.Mapping),
686         StackAlignment(1 << Mapping.Scale),
687         EmptyInlineAsm(CallInst::Create(ASan.EmptyAsm)) {}
688 
689   bool runOnFunction() {
690     if (!ClStack) return false;
691     // Collect alloca, ret, lifetime instructions etc.
692     for (BasicBlock *BB : depth_first(&F.getEntryBlock())) visit(*BB);
693 
694     if (AllocaVec.empty() && DynamicAllocaVec.empty()) return false;
695 
696     initializeCallbacks(*F.getParent());
697 
698     processDynamicAllocas();
699     processStaticAllocas();
700 
701     if (ClDebugStack) {
702       DEBUG(dbgs() << F);
703     }
704     return true;
705   }
706 
707   // Finds all Alloca instructions and puts
708   // poisoned red zones around all of them.
709   // Then unpoison everything back before the function returns.
710   void processStaticAllocas();
711   void processDynamicAllocas();
712 
713   void createDynamicAllocasInitStorage();
714 
715   // ----------------------- Visitors.
716   /// \brief Collect all Ret instructions.
717   void visitReturnInst(ReturnInst &RI) { RetVec.push_back(&RI); }
718 
719   /// \brief Collect all Resume instructions.
720   void visitResumeInst(ResumeInst &RI) { RetVec.push_back(&RI); }
721 
722   /// \brief Collect all CatchReturnInst instructions.
723   void visitCleanupReturnInst(CleanupReturnInst &CRI) { RetVec.push_back(&CRI); }
724 
725   void unpoisonDynamicAllocasBeforeInst(Instruction *InstBefore,
726                                         Value *SavedStack) {
727     IRBuilder<> IRB(InstBefore);
728     Value *DynamicAreaPtr = IRB.CreatePtrToInt(SavedStack, IntptrTy);
729     // When we insert _asan_allocas_unpoison before @llvm.stackrestore, we
730     // need to adjust extracted SP to compute the address of the most recent
731     // alloca. We have a special @llvm.get.dynamic.area.offset intrinsic for
732     // this purpose.
733     if (!isa<ReturnInst>(InstBefore)) {
734       Function *DynamicAreaOffsetFunc = Intrinsic::getDeclaration(
735           InstBefore->getModule(), Intrinsic::get_dynamic_area_offset,
736           {IntptrTy});
737 
738       Value *DynamicAreaOffset = IRB.CreateCall(DynamicAreaOffsetFunc, {});
739 
740       DynamicAreaPtr = IRB.CreateAdd(IRB.CreatePtrToInt(SavedStack, IntptrTy),
741                                      DynamicAreaOffset);
742     }
743 
744     IRB.CreateCall(AsanAllocasUnpoisonFunc,
745                    {IRB.CreateLoad(DynamicAllocaLayout), DynamicAreaPtr});
746   }
747 
748   // Unpoison dynamic allocas redzones.
749   void unpoisonDynamicAllocas() {
750     for (auto &Ret : RetVec)
751       unpoisonDynamicAllocasBeforeInst(Ret, DynamicAllocaLayout);
752 
753     for (auto &StackRestoreInst : StackRestoreVec)
754       unpoisonDynamicAllocasBeforeInst(StackRestoreInst,
755                                        StackRestoreInst->getOperand(0));
756   }
757 
758   // Deploy and poison redzones around dynamic alloca call. To do this, we
759   // should replace this call with another one with changed parameters and
760   // replace all its uses with new address, so
761   //   addr = alloca type, old_size, align
762   // is replaced by
763   //   new_size = (old_size + additional_size) * sizeof(type)
764   //   tmp = alloca i8, new_size, max(align, 32)
765   //   addr = tmp + 32 (first 32 bytes are for the left redzone).
766   // Additional_size is added to make new memory allocation contain not only
767   // requested memory, but also left, partial and right redzones.
768   void handleDynamicAllocaCall(AllocaInst *AI);
769 
770   /// \brief Collect Alloca instructions we want (and can) handle.
771   void visitAllocaInst(AllocaInst &AI) {
772     if (!ASan.isInterestingAlloca(AI)) {
773       if (AI.isStaticAlloca()) {
774         // Skip over allocas that are present *before* the first instrumented
775         // alloca, we don't want to move those around.
776         if (AllocaVec.empty())
777           return;
778 
779         StaticAllocasToMoveUp.push_back(&AI);
780       }
781       return;
782     }
783 
784     StackAlignment = std::max(StackAlignment, AI.getAlignment());
785     if (!AI.isStaticAlloca())
786       DynamicAllocaVec.push_back(&AI);
787     else
788       AllocaVec.push_back(&AI);
789   }
790 
791   /// \brief Collect lifetime intrinsic calls to check for use-after-scope
792   /// errors.
793   void visitIntrinsicInst(IntrinsicInst &II) {
794     Intrinsic::ID ID = II.getIntrinsicID();
795     if (ID == Intrinsic::stackrestore) StackRestoreVec.push_back(&II);
796     if (ID == Intrinsic::localescape) LocalEscapeCall = &II;
797     if (!ASan.UseAfterScope)
798       return;
799     if (ID != Intrinsic::lifetime_start && ID != Intrinsic::lifetime_end)
800       return;
801     // Found lifetime intrinsic, add ASan instrumentation if necessary.
802     ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
803     // If size argument is undefined, don't do anything.
804     if (Size->isMinusOne()) return;
805     // Check that size doesn't saturate uint64_t and can
806     // be stored in IntptrTy.
807     const uint64_t SizeValue = Size->getValue().getLimitedValue();
808     if (SizeValue == ~0ULL ||
809         !ConstantInt::isValueValidForType(IntptrTy, SizeValue))
810       return;
811     // Find alloca instruction that corresponds to llvm.lifetime argument.
812     AllocaInst *AI = findAllocaForValue(II.getArgOperand(1));
813     if (!AI || !ASan.isInterestingAlloca(*AI))
814       return;
815     bool DoPoison = (ID == Intrinsic::lifetime_end);
816     AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};
817     if (AI->isStaticAlloca())
818       StaticAllocaPoisonCallVec.push_back(APC);
819     else if (ClInstrumentDynamicAllocas)
820       DynamicAllocaPoisonCallVec.push_back(APC);
821   }
822 
823   void visitCallSite(CallSite CS) {
824     Instruction *I = CS.getInstruction();
825     if (CallInst *CI = dyn_cast<CallInst>(I)) {
826       HasNonEmptyInlineAsm |=
827           CI->isInlineAsm() && !CI->isIdenticalTo(EmptyInlineAsm.get());
828       HasReturnsTwiceCall |= CI->canReturnTwice();
829     }
830   }
831 
832   // ---------------------- Helpers.
833   void initializeCallbacks(Module &M);
834 
835   bool doesDominateAllExits(const Instruction *I) const {
836     for (auto Ret : RetVec) {
837       if (!ASan.getDominatorTree().dominates(I, Ret)) return false;
838     }
839     return true;
840   }
841 
842   /// Finds alloca where the value comes from.
843   AllocaInst *findAllocaForValue(Value *V);
844 
845   // Copies bytes from ShadowBytes into shadow memory for indexes where
846   // ShadowMask is not zero. If ShadowMask[i] is zero, we assume that
847   // ShadowBytes[i] is constantly zero and doesn't need to be overwritten.
848   void copyToShadow(ArrayRef<uint8_t> ShadowMask, ArrayRef<uint8_t> ShadowBytes,
849                     IRBuilder<> &IRB, Value *ShadowBase);
850   void copyToShadow(ArrayRef<uint8_t> ShadowMask, ArrayRef<uint8_t> ShadowBytes,
851                     size_t Begin, size_t End, IRBuilder<> &IRB,
852                     Value *ShadowBase);
853   void copyToShadowInline(ArrayRef<uint8_t> ShadowMask,
854                           ArrayRef<uint8_t> ShadowBytes, size_t Begin,
855                           size_t End, IRBuilder<> &IRB, Value *ShadowBase);
856 
857   void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison);
858 
859   Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L,
860                                bool Dynamic);
861   PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue,
862                      Instruction *ThenTerm, Value *ValueIfFalse);
863 };
864 
865 } // anonymous namespace
866 
867 char AddressSanitizer::ID = 0;
868 INITIALIZE_PASS_BEGIN(
869     AddressSanitizer, "asan",
870     "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
871     false)
872 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
873 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
874 INITIALIZE_PASS_END(
875     AddressSanitizer, "asan",
876     "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
877     false)
878 FunctionPass *llvm::createAddressSanitizerFunctionPass(bool CompileKernel,
879                                                        bool Recover,
880                                                        bool UseAfterScope) {
881   assert(!CompileKernel || Recover);
882   return new AddressSanitizer(CompileKernel, Recover, UseAfterScope);
883 }
884 
885 char AddressSanitizerModule::ID = 0;
886 INITIALIZE_PASS(
887     AddressSanitizerModule, "asan-module",
888     "AddressSanitizer: detects use-after-free and out-of-bounds bugs."
889     "ModulePass",
890     false, false)
891 ModulePass *llvm::createAddressSanitizerModulePass(bool CompileKernel,
892                                                    bool Recover) {
893   assert(!CompileKernel || Recover);
894   return new AddressSanitizerModule(CompileKernel, Recover);
895 }
896 
897 static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
898   size_t Res = countTrailingZeros(TypeSize / 8);
899   assert(Res < kNumberOfAccessSizes);
900   return Res;
901 }
902 
903 // \brief Create a constant for Str so that we can pass it to the run-time lib.
904 static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
905                                                     bool AllowMerging) {
906   Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
907   // We use private linkage for module-local strings. If they can be merged
908   // with another one, we set the unnamed_addr attribute.
909   GlobalVariable *GV =
910       new GlobalVariable(M, StrConst->getType(), true,
911                          GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix);
912   if (AllowMerging) GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
913   GV->setAlignment(1);  // Strings may not be merged w/o setting align 1.
914   return GV;
915 }
916 
917 /// \brief Create a global describing a source location.
918 static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M,
919                                                        LocationMetadata MD) {
920   Constant *LocData[] = {
921       createPrivateGlobalForString(M, MD.Filename, true),
922       ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo),
923       ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo),
924   };
925   auto LocStruct = ConstantStruct::getAnon(LocData);
926   auto GV = new GlobalVariable(M, LocStruct->getType(), true,
927                                GlobalValue::PrivateLinkage, LocStruct,
928                                kAsanGenPrefix);
929   GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
930   return GV;
931 }
932 
933 /// \brief Check if \p G has been created by a trusted compiler pass.
934 static bool GlobalWasGeneratedByCompiler(GlobalVariable *G) {
935   // Do not instrument asan globals.
936   if (G->getName().startswith(kAsanGenPrefix) ||
937       G->getName().startswith(kSanCovGenPrefix) ||
938       G->getName().startswith(kODRGenPrefix))
939     return true;
940 
941   // Do not instrument gcov counter arrays.
942   if (G->getName() == "__llvm_gcov_ctr")
943     return true;
944 
945   return false;
946 }
947 
948 Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
949   // Shadow >> scale
950   Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
951   if (Mapping.Offset == 0) return Shadow;
952   // (Shadow >> scale) | offset
953   Value *ShadowBase;
954   if (LocalDynamicShadow)
955     ShadowBase = LocalDynamicShadow;
956   else
957     ShadowBase = ConstantInt::get(IntptrTy, Mapping.Offset);
958   if (Mapping.OrShadowOffset)
959     return IRB.CreateOr(Shadow, ShadowBase);
960   else
961     return IRB.CreateAdd(Shadow, ShadowBase);
962 }
963 
964 // Instrument memset/memmove/memcpy
965 void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
966   IRBuilder<> IRB(MI);
967   if (isa<MemTransferInst>(MI)) {
968     IRB.CreateCall(
969         isa<MemMoveInst>(MI) ? AsanMemmove : AsanMemcpy,
970         {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
971          IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()),
972          IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
973   } else if (isa<MemSetInst>(MI)) {
974     IRB.CreateCall(
975         AsanMemset,
976         {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
977          IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
978          IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
979   }
980   MI->eraseFromParent();
981 }
982 
983 /// Check if we want (and can) handle this alloca.
984 bool AddressSanitizer::isInterestingAlloca(const AllocaInst &AI) {
985   auto PreviouslySeenAllocaInfo = ProcessedAllocas.find(&AI);
986 
987   if (PreviouslySeenAllocaInfo != ProcessedAllocas.end())
988     return PreviouslySeenAllocaInfo->getSecond();
989 
990   bool IsInteresting =
991       (AI.getAllocatedType()->isSized() &&
992        // alloca() may be called with 0 size, ignore it.
993        ((!AI.isStaticAlloca()) || getAllocaSizeInBytes(AI) > 0) &&
994        // We are only interested in allocas not promotable to registers.
995        // Promotable allocas are common under -O0.
996        (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI)) &&
997        // inalloca allocas are not treated as static, and we don't want
998        // dynamic alloca instrumentation for them as well.
999        !AI.isUsedWithInAlloca());
1000 
1001   ProcessedAllocas[&AI] = IsInteresting;
1002   return IsInteresting;
1003 }
1004 
1005 Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I,
1006                                                    bool *IsWrite,
1007                                                    uint64_t *TypeSize,
1008                                                    unsigned *Alignment,
1009                                                    Value **MaybeMask) {
1010   // Skip memory accesses inserted by another instrumentation.
1011   if (I->getMetadata("nosanitize")) return nullptr;
1012 
1013   // Do not instrument the load fetching the dynamic shadow address.
1014   if (LocalDynamicShadow == I)
1015     return nullptr;
1016 
1017   Value *PtrOperand = nullptr;
1018   const DataLayout &DL = I->getModule()->getDataLayout();
1019   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
1020     if (!ClInstrumentReads) return nullptr;
1021     *IsWrite = false;
1022     *TypeSize = DL.getTypeStoreSizeInBits(LI->getType());
1023     *Alignment = LI->getAlignment();
1024     PtrOperand = LI->getPointerOperand();
1025   } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
1026     if (!ClInstrumentWrites) return nullptr;
1027     *IsWrite = true;
1028     *TypeSize = DL.getTypeStoreSizeInBits(SI->getValueOperand()->getType());
1029     *Alignment = SI->getAlignment();
1030     PtrOperand = SI->getPointerOperand();
1031   } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
1032     if (!ClInstrumentAtomics) return nullptr;
1033     *IsWrite = true;
1034     *TypeSize = DL.getTypeStoreSizeInBits(RMW->getValOperand()->getType());
1035     *Alignment = 0;
1036     PtrOperand = RMW->getPointerOperand();
1037   } else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
1038     if (!ClInstrumentAtomics) return nullptr;
1039     *IsWrite = true;
1040     *TypeSize = DL.getTypeStoreSizeInBits(XCHG->getCompareOperand()->getType());
1041     *Alignment = 0;
1042     PtrOperand = XCHG->getPointerOperand();
1043   } else if (auto CI = dyn_cast<CallInst>(I)) {
1044     auto *F = dyn_cast<Function>(CI->getCalledValue());
1045     if (F && (F->getName().startswith("llvm.masked.load.") ||
1046               F->getName().startswith("llvm.masked.store."))) {
1047       unsigned OpOffset = 0;
1048       if (F->getName().startswith("llvm.masked.store.")) {
1049         // Masked store has an initial operand for the value.
1050         OpOffset = 1;
1051         *IsWrite = true;
1052       } else {
1053         *IsWrite = false;
1054       }
1055       // Only instrument if the mask is constant for now.
1056       if (isa<ConstantVector>(CI->getOperand(2 + OpOffset))) {
1057         auto BasePtr = CI->getOperand(0 + OpOffset);
1058         auto Ty = cast<PointerType>(BasePtr->getType())->getElementType();
1059         *TypeSize = DL.getTypeStoreSizeInBits(Ty);
1060         if (auto AlignmentConstant =
1061                 dyn_cast<ConstantInt>(CI->getOperand(1 + OpOffset)))
1062           *Alignment = (unsigned)AlignmentConstant->getZExtValue();
1063         else
1064           *Alignment = 1; // No alignment guarantees. We probably got Undef
1065         if (MaybeMask)
1066           *MaybeMask = CI->getOperand(2 + OpOffset);
1067         PtrOperand = BasePtr;
1068       }
1069     }
1070   }
1071 
1072   // Do not instrument acesses from different address spaces; we cannot deal
1073   // with them.
1074   if (PtrOperand) {
1075     Type *PtrTy = cast<PointerType>(PtrOperand->getType()->getScalarType());
1076     if (PtrTy->getPointerAddressSpace() != 0)
1077       return nullptr;
1078   }
1079 
1080   // Treat memory accesses to promotable allocas as non-interesting since they
1081   // will not cause memory violations. This greatly speeds up the instrumented
1082   // executable at -O0.
1083   if (ClSkipPromotableAllocas)
1084     if (auto AI = dyn_cast_or_null<AllocaInst>(PtrOperand))
1085       return isInterestingAlloca(*AI) ? AI : nullptr;
1086 
1087   return PtrOperand;
1088 }
1089 
1090 static bool isPointerOperand(Value *V) {
1091   return V->getType()->isPointerTy() || isa<PtrToIntInst>(V);
1092 }
1093 
1094 // This is a rough heuristic; it may cause both false positives and
1095 // false negatives. The proper implementation requires cooperation with
1096 // the frontend.
1097 static bool isInterestingPointerComparisonOrSubtraction(Instruction *I) {
1098   if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
1099     if (!Cmp->isRelational()) return false;
1100   } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
1101     if (BO->getOpcode() != Instruction::Sub) return false;
1102   } else {
1103     return false;
1104   }
1105   return isPointerOperand(I->getOperand(0)) &&
1106          isPointerOperand(I->getOperand(1));
1107 }
1108 
1109 bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) {
1110   // If a global variable does not have dynamic initialization we don't
1111   // have to instrument it.  However, if a global does not have initializer
1112   // at all, we assume it has dynamic initializer (in other TU).
1113   return G->hasInitializer() && !GlobalsMD.get(G).IsDynInit;
1114 }
1115 
1116 void AddressSanitizer::instrumentPointerComparisonOrSubtraction(
1117     Instruction *I) {
1118   IRBuilder<> IRB(I);
1119   Function *F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction;
1120   Value *Param[2] = {I->getOperand(0), I->getOperand(1)};
1121   for (Value *&i : Param) {
1122     if (i->getType()->isPointerTy())
1123       i = IRB.CreatePointerCast(i, IntptrTy);
1124   }
1125   IRB.CreateCall(F, Param);
1126 }
1127 
1128 static void doInstrumentAddress(AddressSanitizer *Pass, Instruction *I,
1129                                 Value *Addr, unsigned Alignment,
1130                                 unsigned Granularity, uint32_t TypeSize,
1131                                 bool IsWrite, Value *SizeArgument,
1132                                 bool UseCalls, uint32_t Exp) {
1133   // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
1134   // if the data is properly aligned.
1135   if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
1136        TypeSize == 128) &&
1137       (Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
1138     return Pass->instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr,
1139                                    UseCalls, Exp);
1140   Pass->instrumentUnusualSizeOrAlignment(I, Addr, TypeSize, IsWrite, nullptr,
1141                                          UseCalls, Exp);
1142 }
1143 
1144 static void instrumentMaskedLoadOrStore(AddressSanitizer *Pass,
1145                                         const DataLayout &DL, Type *IntptrTy,
1146                                         ConstantVector *Mask, Instruction *I,
1147                                         Value *Addr, unsigned Alignment,
1148                                         unsigned Granularity, uint32_t TypeSize,
1149                                         bool IsWrite, Value *SizeArgument,
1150                                         bool UseCalls, uint32_t Exp) {
1151   auto *VTy = cast<PointerType>(Addr->getType())->getElementType();
1152   uint64_t ElemTypeSize = DL.getTypeStoreSizeInBits(VTy->getScalarType());
1153   unsigned Num = VTy->getVectorNumElements();
1154   auto Zero = ConstantInt::get(IntptrTy, 0);
1155   for (unsigned Idx = 0; Idx < Num; ++Idx) {
1156     // dyn_cast as we might get UndefValue
1157     auto Masked = dyn_cast<ConstantInt>(Mask->getOperand(Idx));
1158     if (Masked && Masked->isAllOnesValue()) {
1159       IRBuilder<> IRB(I);
1160       auto InstrumentedAddress =
1161           IRB.CreateGEP(Addr, {Zero, ConstantInt::get(IntptrTy, Idx)});
1162       doInstrumentAddress(Pass, I, InstrumentedAddress, Alignment, Granularity,
1163                           ElemTypeSize, IsWrite, SizeArgument, UseCalls, Exp);
1164     }
1165   }
1166 }
1167 
1168 void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
1169                                      Instruction *I, bool UseCalls,
1170                                      const DataLayout &DL) {
1171   bool IsWrite = false;
1172   unsigned Alignment = 0;
1173   uint64_t TypeSize = 0;
1174   Value *MaybeMask = nullptr;
1175   Value *Addr =
1176       isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment, &MaybeMask);
1177   assert(Addr);
1178 
1179   // Optimization experiments.
1180   // The experiments can be used to evaluate potential optimizations that remove
1181   // instrumentation (assess false negatives). Instead of completely removing
1182   // some instrumentation, you set Exp to a non-zero value (mask of optimization
1183   // experiments that want to remove instrumentation of this instruction).
1184   // If Exp is non-zero, this pass will emit special calls into runtime
1185   // (e.g. __asan_report_exp_load1 instead of __asan_report_load1). These calls
1186   // make runtime terminate the program in a special way (with a different
1187   // exit status). Then you run the new compiler on a buggy corpus, collect
1188   // the special terminations (ideally, you don't see them at all -- no false
1189   // negatives) and make the decision on the optimization.
1190   uint32_t Exp = ClForceExperiment;
1191 
1192   if (ClOpt && ClOptGlobals) {
1193     // If initialization order checking is disabled, a simple access to a
1194     // dynamically initialized global is always valid.
1195     GlobalVariable *G = dyn_cast<GlobalVariable>(GetUnderlyingObject(Addr, DL));
1196     if (G && (!ClInitializers || GlobalIsLinkerInitialized(G)) &&
1197         isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
1198       NumOptimizedAccessesToGlobalVar++;
1199       return;
1200     }
1201   }
1202 
1203   if (ClOpt && ClOptStack) {
1204     // A direct inbounds access to a stack variable is always valid.
1205     if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
1206         isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
1207       NumOptimizedAccessesToStackVar++;
1208       return;
1209     }
1210   }
1211 
1212   if (IsWrite)
1213     NumInstrumentedWrites++;
1214   else
1215     NumInstrumentedReads++;
1216 
1217   unsigned Granularity = 1 << Mapping.Scale;
1218   if (MaybeMask) {
1219     auto Mask = cast<ConstantVector>(MaybeMask);
1220     instrumentMaskedLoadOrStore(this, DL, IntptrTy, Mask, I, Addr, Alignment,
1221                                 Granularity, TypeSize, IsWrite, nullptr,
1222                                 UseCalls, Exp);
1223   } else {
1224     doInstrumentAddress(this, I, Addr, Alignment, Granularity, TypeSize,
1225                         IsWrite, nullptr, UseCalls, Exp);
1226   }
1227 }
1228 
1229 Instruction *AddressSanitizer::generateCrashCode(Instruction *InsertBefore,
1230                                                  Value *Addr, bool IsWrite,
1231                                                  size_t AccessSizeIndex,
1232                                                  Value *SizeArgument,
1233                                                  uint32_t Exp) {
1234   IRBuilder<> IRB(InsertBefore);
1235   Value *ExpVal = Exp == 0 ? nullptr : ConstantInt::get(IRB.getInt32Ty(), Exp);
1236   CallInst *Call = nullptr;
1237   if (SizeArgument) {
1238     if (Exp == 0)
1239       Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][0],
1240                             {Addr, SizeArgument});
1241     else
1242       Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][1],
1243                             {Addr, SizeArgument, ExpVal});
1244   } else {
1245     if (Exp == 0)
1246       Call =
1247           IRB.CreateCall(AsanErrorCallback[IsWrite][0][AccessSizeIndex], Addr);
1248     else
1249       Call = IRB.CreateCall(AsanErrorCallback[IsWrite][1][AccessSizeIndex],
1250                             {Addr, ExpVal});
1251   }
1252 
1253   // We don't do Call->setDoesNotReturn() because the BB already has
1254   // UnreachableInst at the end.
1255   // This EmptyAsm is required to avoid callback merge.
1256   IRB.CreateCall(EmptyAsm, {});
1257   return Call;
1258 }
1259 
1260 Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
1261                                            Value *ShadowValue,
1262                                            uint32_t TypeSize) {
1263   size_t Granularity = static_cast<size_t>(1) << Mapping.Scale;
1264   // Addr & (Granularity - 1)
1265   Value *LastAccessedByte =
1266       IRB.CreateAnd(AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
1267   // (Addr & (Granularity - 1)) + size - 1
1268   if (TypeSize / 8 > 1)
1269     LastAccessedByte = IRB.CreateAdd(
1270         LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
1271   // (uint8_t) ((Addr & (Granularity-1)) + size - 1)
1272   LastAccessedByte =
1273       IRB.CreateIntCast(LastAccessedByte, ShadowValue->getType(), false);
1274   // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
1275   return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
1276 }
1277 
1278 void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
1279                                          Instruction *InsertBefore, Value *Addr,
1280                                          uint32_t TypeSize, bool IsWrite,
1281                                          Value *SizeArgument, bool UseCalls,
1282                                          uint32_t Exp) {
1283   IRBuilder<> IRB(InsertBefore);
1284   Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
1285   size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
1286 
1287   if (UseCalls) {
1288     if (Exp == 0)
1289       IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][0][AccessSizeIndex],
1290                      AddrLong);
1291     else
1292       IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][1][AccessSizeIndex],
1293                      {AddrLong, ConstantInt::get(IRB.getInt32Ty(), Exp)});
1294     return;
1295   }
1296 
1297   Type *ShadowTy =
1298       IntegerType::get(*C, std::max(8U, TypeSize >> Mapping.Scale));
1299   Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
1300   Value *ShadowPtr = memToShadow(AddrLong, IRB);
1301   Value *CmpVal = Constant::getNullValue(ShadowTy);
1302   Value *ShadowValue =
1303       IRB.CreateLoad(IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
1304 
1305   Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
1306   size_t Granularity = 1ULL << Mapping.Scale;
1307   TerminatorInst *CrashTerm = nullptr;
1308 
1309   if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) {
1310     // We use branch weights for the slow path check, to indicate that the slow
1311     // path is rarely taken. This seems to be the case for SPEC benchmarks.
1312     TerminatorInst *CheckTerm = SplitBlockAndInsertIfThen(
1313         Cmp, InsertBefore, false, MDBuilder(*C).createBranchWeights(1, 100000));
1314     assert(cast<BranchInst>(CheckTerm)->isUnconditional());
1315     BasicBlock *NextBB = CheckTerm->getSuccessor(0);
1316     IRB.SetInsertPoint(CheckTerm);
1317     Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
1318     if (Recover) {
1319       CrashTerm = SplitBlockAndInsertIfThen(Cmp2, CheckTerm, false);
1320     } else {
1321       BasicBlock *CrashBlock =
1322         BasicBlock::Create(*C, "", NextBB->getParent(), NextBB);
1323       CrashTerm = new UnreachableInst(*C, CrashBlock);
1324       BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
1325       ReplaceInstWithInst(CheckTerm, NewTerm);
1326     }
1327   } else {
1328     CrashTerm = SplitBlockAndInsertIfThen(Cmp, InsertBefore, !Recover);
1329   }
1330 
1331   Instruction *Crash = generateCrashCode(CrashTerm, AddrLong, IsWrite,
1332                                          AccessSizeIndex, SizeArgument, Exp);
1333   Crash->setDebugLoc(OrigIns->getDebugLoc());
1334 }
1335 
1336 // Instrument unusual size or unusual alignment.
1337 // We can not do it with a single check, so we do 1-byte check for the first
1338 // and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
1339 // to report the actual access size.
1340 void AddressSanitizer::instrumentUnusualSizeOrAlignment(
1341     Instruction *I, Value *Addr, uint32_t TypeSize, bool IsWrite,
1342     Value *SizeArgument, bool UseCalls, uint32_t Exp) {
1343   IRBuilder<> IRB(I);
1344   Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8);
1345   Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
1346   if (UseCalls) {
1347     if (Exp == 0)
1348       IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][0],
1349                      {AddrLong, Size});
1350     else
1351       IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][1],
1352                      {AddrLong, Size, ConstantInt::get(IRB.getInt32Ty(), Exp)});
1353   } else {
1354     Value *LastByte = IRB.CreateIntToPtr(
1355         IRB.CreateAdd(AddrLong, ConstantInt::get(IntptrTy, TypeSize / 8 - 1)),
1356         Addr->getType());
1357     instrumentAddress(I, I, Addr, 8, IsWrite, Size, false, Exp);
1358     instrumentAddress(I, I, LastByte, 8, IsWrite, Size, false, Exp);
1359   }
1360 }
1361 
1362 void AddressSanitizerModule::poisonOneInitializer(Function &GlobalInit,
1363                                                   GlobalValue *ModuleName) {
1364   // Set up the arguments to our poison/unpoison functions.
1365   IRBuilder<> IRB(&GlobalInit.front(),
1366                   GlobalInit.front().getFirstInsertionPt());
1367 
1368   // Add a call to poison all external globals before the given function starts.
1369   Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
1370   IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
1371 
1372   // Add calls to unpoison all globals before each return instruction.
1373   for (auto &BB : GlobalInit.getBasicBlockList())
1374     if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1375       CallInst::Create(AsanUnpoisonGlobals, "", RI);
1376 }
1377 
1378 void AddressSanitizerModule::createInitializerPoisonCalls(
1379     Module &M, GlobalValue *ModuleName) {
1380   GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
1381 
1382   ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1383   for (Use &OP : CA->operands()) {
1384     if (isa<ConstantAggregateZero>(OP)) continue;
1385     ConstantStruct *CS = cast<ConstantStruct>(OP);
1386 
1387     // Must have a function or null ptr.
1388     if (Function *F = dyn_cast<Function>(CS->getOperand(1))) {
1389       if (F->getName() == kAsanModuleCtorName) continue;
1390       ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
1391       // Don't instrument CTORs that will run before asan.module_ctor.
1392       if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue;
1393       poisonOneInitializer(*F, ModuleName);
1394     }
1395   }
1396 }
1397 
1398 bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
1399   Type *Ty = G->getValueType();
1400   DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
1401 
1402   if (GlobalsMD.get(G).IsBlacklisted) return false;
1403   if (!Ty->isSized()) return false;
1404   if (!G->hasInitializer()) return false;
1405   if (GlobalWasGeneratedByCompiler(G)) return false; // Our own globals.
1406   // Touch only those globals that will not be defined in other modules.
1407   // Don't handle ODR linkage types and COMDATs since other modules may be built
1408   // without ASan.
1409   if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
1410       G->getLinkage() != GlobalVariable::PrivateLinkage &&
1411       G->getLinkage() != GlobalVariable::InternalLinkage)
1412     return false;
1413   if (G->hasComdat()) return false;
1414   // Two problems with thread-locals:
1415   //   - The address of the main thread's copy can't be computed at link-time.
1416   //   - Need to poison all copies, not just the main thread's one.
1417   if (G->isThreadLocal()) return false;
1418   // For now, just ignore this Global if the alignment is large.
1419   if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
1420 
1421   if (G->hasSection()) {
1422     StringRef Section = G->getSection();
1423 
1424     // Globals from llvm.metadata aren't emitted, do not instrument them.
1425     if (Section == "llvm.metadata") return false;
1426     // Do not instrument globals from special LLVM sections.
1427     if (Section.find("__llvm") != StringRef::npos || Section.find("__LLVM") != StringRef::npos) return false;
1428 
1429     // Do not instrument function pointers to initialization and termination
1430     // routines: dynamic linker will not properly handle redzones.
1431     if (Section.startswith(".preinit_array") ||
1432         Section.startswith(".init_array") ||
1433         Section.startswith(".fini_array")) {
1434       return false;
1435     }
1436 
1437     // Callbacks put into the CRT initializer/terminator sections
1438     // should not be instrumented.
1439     // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
1440     // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
1441     if (Section.startswith(".CRT")) {
1442       DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
1443       return false;
1444     }
1445 
1446     if (TargetTriple.isOSBinFormatMachO()) {
1447       StringRef ParsedSegment, ParsedSection;
1448       unsigned TAA = 0, StubSize = 0;
1449       bool TAAParsed;
1450       std::string ErrorCode = MCSectionMachO::ParseSectionSpecifier(
1451           Section, ParsedSegment, ParsedSection, TAA, TAAParsed, StubSize);
1452       assert(ErrorCode.empty() && "Invalid section specifier.");
1453 
1454       // Ignore the globals from the __OBJC section. The ObjC runtime assumes
1455       // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
1456       // them.
1457       if (ParsedSegment == "__OBJC" ||
1458           (ParsedSegment == "__DATA" && ParsedSection.startswith("__objc_"))) {
1459         DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n");
1460         return false;
1461       }
1462       // See http://code.google.com/p/address-sanitizer/issues/detail?id=32
1463       // Constant CFString instances are compiled in the following way:
1464       //  -- the string buffer is emitted into
1465       //     __TEXT,__cstring,cstring_literals
1466       //  -- the constant NSConstantString structure referencing that buffer
1467       //     is placed into __DATA,__cfstring
1468       // Therefore there's no point in placing redzones into __DATA,__cfstring.
1469       // Moreover, it causes the linker to crash on OS X 10.7
1470       if (ParsedSegment == "__DATA" && ParsedSection == "__cfstring") {
1471         DEBUG(dbgs() << "Ignoring CFString: " << *G << "\n");
1472         return false;
1473       }
1474       // The linker merges the contents of cstring_literals and removes the
1475       // trailing zeroes.
1476       if (ParsedSegment == "__TEXT" && (TAA & MachO::S_CSTRING_LITERALS)) {
1477         DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n");
1478         return false;
1479       }
1480     }
1481   }
1482 
1483   return true;
1484 }
1485 
1486 // On Mach-O platforms, we emit global metadata in a separate section of the
1487 // binary in order to allow the linker to properly dead strip. This is only
1488 // supported on recent versions of ld64.
1489 bool AddressSanitizerModule::ShouldUseMachOGlobalsSection() const {
1490   if (!ClUseMachOGlobalsSection)
1491     return false;
1492 
1493   if (!TargetTriple.isOSBinFormatMachO())
1494     return false;
1495 
1496   if (TargetTriple.isMacOSX() && !TargetTriple.isMacOSXVersionLT(10, 11))
1497     return true;
1498   if (TargetTriple.isiOS() /* or tvOS */ && !TargetTriple.isOSVersionLT(9))
1499     return true;
1500   if (TargetTriple.isWatchOS() && !TargetTriple.isOSVersionLT(2))
1501     return true;
1502 
1503   return false;
1504 }
1505 
1506 StringRef AddressSanitizerModule::getGlobalMetadataSection() const {
1507   switch (TargetTriple.getObjectFormat()) {
1508   case Triple::COFF:  return ".ASAN$GL";
1509   case Triple::ELF:   return "asan_globals";
1510   case Triple::MachO: return "__DATA,__asan_globals,regular";
1511   default: break;
1512   }
1513   llvm_unreachable("unsupported object format");
1514 }
1515 
1516 void AddressSanitizerModule::initializeCallbacks(Module &M) {
1517   IRBuilder<> IRB(*C);
1518 
1519   // Declare our poisoning and unpoisoning functions.
1520   AsanPoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1521       kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
1522   AsanPoisonGlobals->setLinkage(Function::ExternalLinkage);
1523   AsanUnpoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1524       kAsanUnpoisonGlobalsName, IRB.getVoidTy(), nullptr));
1525   AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
1526 
1527   // Declare functions that register/unregister globals.
1528   AsanRegisterGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1529       kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1530   AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
1531   AsanUnregisterGlobals = checkSanitizerInterfaceFunction(
1532       M.getOrInsertFunction(kAsanUnregisterGlobalsName, IRB.getVoidTy(),
1533                             IntptrTy, IntptrTy, nullptr));
1534   AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
1535 
1536   // Declare the functions that find globals in a shared object and then invoke
1537   // the (un)register function on them.
1538   AsanRegisterImageGlobals = checkSanitizerInterfaceFunction(
1539       M.getOrInsertFunction(kAsanRegisterImageGlobalsName,
1540       IRB.getVoidTy(), IntptrTy, nullptr));
1541   AsanRegisterImageGlobals->setLinkage(Function::ExternalLinkage);
1542 
1543   AsanUnregisterImageGlobals = checkSanitizerInterfaceFunction(
1544       M.getOrInsertFunction(kAsanUnregisterImageGlobalsName,
1545       IRB.getVoidTy(), IntptrTy, nullptr));
1546   AsanUnregisterImageGlobals->setLinkage(Function::ExternalLinkage);
1547 }
1548 
1549 // This function replaces all global variables with new variables that have
1550 // trailing redzones. It also creates a function that poisons
1551 // redzones and inserts this function into llvm.global_ctors.
1552 bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
1553   GlobalsMD.init(M);
1554 
1555   SmallVector<GlobalVariable *, 16> GlobalsToChange;
1556 
1557   for (auto &G : M.globals()) {
1558     if (ShouldInstrumentGlobal(&G)) GlobalsToChange.push_back(&G);
1559   }
1560 
1561   size_t n = GlobalsToChange.size();
1562   if (n == 0) return false;
1563 
1564   auto &DL = M.getDataLayout();
1565   bool UseComdatMetadata = TargetTriple.isOSBinFormatCOFF();
1566   bool UseMachOGlobalsSection = ShouldUseMachOGlobalsSection();
1567   bool UseMetadataArray = !(UseComdatMetadata || UseMachOGlobalsSection);
1568 
1569   // A global is described by a structure
1570   //   size_t beg;
1571   //   size_t size;
1572   //   size_t size_with_redzone;
1573   //   const char *name;
1574   //   const char *module_name;
1575   //   size_t has_dynamic_init;
1576   //   void *source_location;
1577   //   size_t odr_indicator;
1578   // We initialize an array of such structures and pass it to a run-time call.
1579   StructType *GlobalStructTy =
1580       StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
1581                       IntptrTy, IntptrTy, IntptrTy, nullptr);
1582   unsigned SizeOfGlobalStruct = DL.getTypeAllocSize(GlobalStructTy);
1583   assert((isPowerOf2_32(SizeOfGlobalStruct) ||
1584           !TargetTriple.isOSBinFormatCOFF()) &&
1585          "global metadata will not be padded appropriately");
1586   SmallVector<Constant *, 16> Initializers(UseMetadataArray ? n : 0);
1587 
1588   // On recent Mach-O platforms, use a structure which binds the liveness of
1589   // the global variable to the metadata struct. Keep the list of "Liveness" GV
1590   // created to be added to llvm.compiler.used
1591   StructType *LivenessTy  = nullptr;
1592   if (UseMachOGlobalsSection)
1593     LivenessTy = StructType::get(IntptrTy, IntptrTy, nullptr);
1594   SmallVector<GlobalValue *, 16> LivenessGlobals(
1595       UseMachOGlobalsSection ? n : 0);
1596 
1597   bool HasDynamicallyInitializedGlobals = false;
1598 
1599   // We shouldn't merge same module names, as this string serves as unique
1600   // module ID in runtime.
1601   GlobalVariable *ModuleName = createPrivateGlobalForString(
1602       M, M.getModuleIdentifier(), /*AllowMerging*/ false);
1603 
1604   for (size_t i = 0; i < n; i++) {
1605     static const uint64_t kMaxGlobalRedzone = 1 << 18;
1606     GlobalVariable *G = GlobalsToChange[i];
1607 
1608     auto MD = GlobalsMD.get(G);
1609     StringRef NameForGlobal = G->getName();
1610     // Create string holding the global name (use global name from metadata
1611     // if it's available, otherwise just write the name of global variable).
1612     GlobalVariable *Name = createPrivateGlobalForString(
1613         M, MD.Name.empty() ? NameForGlobal : MD.Name,
1614         /*AllowMerging*/ true);
1615 
1616     Type *Ty = G->getValueType();
1617     uint64_t SizeInBytes = DL.getTypeAllocSize(Ty);
1618     uint64_t MinRZ = MinRedzoneSizeForGlobal();
1619     // MinRZ <= RZ <= kMaxGlobalRedzone
1620     // and trying to make RZ to be ~ 1/4 of SizeInBytes.
1621     uint64_t RZ = std::max(
1622         MinRZ, std::min(kMaxGlobalRedzone, (SizeInBytes / MinRZ / 4) * MinRZ));
1623     uint64_t RightRedzoneSize = RZ;
1624     // Round up to MinRZ
1625     if (SizeInBytes % MinRZ) RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
1626     assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
1627     Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
1628 
1629     StructType *NewTy = StructType::get(Ty, RightRedZoneTy, nullptr);
1630     Constant *NewInitializer =
1631         ConstantStruct::get(NewTy, G->getInitializer(),
1632                             Constant::getNullValue(RightRedZoneTy), nullptr);
1633 
1634     // Create a new global variable with enough space for a redzone.
1635     GlobalValue::LinkageTypes Linkage = G->getLinkage();
1636     if (G->isConstant() && Linkage == GlobalValue::PrivateLinkage)
1637       Linkage = GlobalValue::InternalLinkage;
1638     GlobalVariable *NewGlobal =
1639         new GlobalVariable(M, NewTy, G->isConstant(), Linkage, NewInitializer,
1640                            "", G, G->getThreadLocalMode());
1641     NewGlobal->copyAttributesFrom(G);
1642     NewGlobal->setAlignment(MinRZ);
1643 
1644     // Move null-terminated C strings to "__asan_cstring" section on Darwin.
1645     if (TargetTriple.isOSBinFormatMachO() && !G->hasSection() &&
1646         G->isConstant()) {
1647       auto Seq = dyn_cast<ConstantDataSequential>(G->getInitializer());
1648       if (Seq && Seq->isCString())
1649         NewGlobal->setSection("__TEXT,__asan_cstring,regular");
1650     }
1651 
1652     // Transfer the debug info.  The payload starts at offset zero so we can
1653     // copy the debug info over as is.
1654     SmallVector<DIGlobalVariable *, 1> GVs;
1655     G->getDebugInfo(GVs);
1656     for (auto *GV : GVs)
1657       NewGlobal->addDebugInfo(GV);
1658 
1659     Value *Indices2[2];
1660     Indices2[0] = IRB.getInt32(0);
1661     Indices2[1] = IRB.getInt32(0);
1662 
1663     G->replaceAllUsesWith(
1664         ConstantExpr::getGetElementPtr(NewTy, NewGlobal, Indices2, true));
1665     NewGlobal->takeName(G);
1666     G->eraseFromParent();
1667     G = NewGlobal;
1668 
1669     if (UseComdatMetadata) {
1670       // Get or create a COMDAT for G so that we can use it with our metadata.
1671       Comdat *C = G->getComdat();
1672       if (!C) {
1673         if (!G->hasName()) {
1674           // If G is unnamed, it must be internal. Give it an artificial name
1675           // so we can put it in a comdat.
1676           assert(G->hasLocalLinkage());
1677           G->setName(Twine(kAsanGenPrefix) + "_anon_global");
1678         }
1679         C = M.getOrInsertComdat(G->getName());
1680         // Make this IMAGE_COMDAT_SELECT_NODUPLICATES on COFF.
1681         if (TargetTriple.isOSBinFormatCOFF())
1682           C->setSelectionKind(Comdat::NoDuplicates);
1683         G->setComdat(C);
1684       }
1685     }
1686 
1687     Constant *SourceLoc;
1688     if (!MD.SourceLoc.empty()) {
1689       auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc);
1690       SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy);
1691     } else {
1692       SourceLoc = ConstantInt::get(IntptrTy, 0);
1693     }
1694 
1695     Constant *ODRIndicator = ConstantExpr::getNullValue(IRB.getInt8PtrTy());
1696     GlobalValue *InstrumentedGlobal = NewGlobal;
1697 
1698     bool CanUsePrivateAliases =
1699         TargetTriple.isOSBinFormatELF() || TargetTriple.isOSBinFormatMachO();
1700     if (CanUsePrivateAliases && ClUsePrivateAliasForGlobals) {
1701       // Create local alias for NewGlobal to avoid crash on ODR between
1702       // instrumented and non-instrumented libraries.
1703       auto *GA = GlobalAlias::create(GlobalValue::InternalLinkage,
1704                                      NameForGlobal + M.getName(), NewGlobal);
1705 
1706       // With local aliases, we need to provide another externally visible
1707       // symbol __odr_asan_XXX to detect ODR violation.
1708       auto *ODRIndicatorSym =
1709           new GlobalVariable(M, IRB.getInt8Ty(), false, Linkage,
1710                              Constant::getNullValue(IRB.getInt8Ty()),
1711                              kODRGenPrefix + NameForGlobal, nullptr,
1712                              NewGlobal->getThreadLocalMode());
1713 
1714       // Set meaningful attributes for indicator symbol.
1715       ODRIndicatorSym->setVisibility(NewGlobal->getVisibility());
1716       ODRIndicatorSym->setDLLStorageClass(NewGlobal->getDLLStorageClass());
1717       ODRIndicatorSym->setAlignment(1);
1718       ODRIndicator = ODRIndicatorSym;
1719       InstrumentedGlobal = GA;
1720     }
1721 
1722     Constant *Initializer = ConstantStruct::get(
1723         GlobalStructTy,
1724         ConstantExpr::getPointerCast(InstrumentedGlobal, IntptrTy),
1725         ConstantInt::get(IntptrTy, SizeInBytes),
1726         ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
1727         ConstantExpr::getPointerCast(Name, IntptrTy),
1728         ConstantExpr::getPointerCast(ModuleName, IntptrTy),
1729         ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc,
1730         ConstantExpr::getPointerCast(ODRIndicator, IntptrTy), nullptr);
1731 
1732     if (ClInitializers && MD.IsDynInit) HasDynamicallyInitializedGlobals = true;
1733 
1734     DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
1735 
1736     // If we aren't using separate metadata globals, add it to the initializer
1737     // list and continue.
1738     if (UseMetadataArray) {
1739       Initializers[i] = Initializer;
1740       continue;
1741     }
1742 
1743     // Create a separate metadata global and put it in the appropriate ASan
1744     // global registration section.
1745     GlobalVariable *Metadata = new GlobalVariable(
1746         M, GlobalStructTy, false, GlobalVariable::InternalLinkage,
1747         Initializer, Twine("__asan_global_") +
1748                              GlobalValue::getRealLinkageName(G->getName()));
1749     Metadata->setSection(getGlobalMetadataSection());
1750 
1751     // The MSVC linker always inserts padding when linking incrementally. We
1752     // cope with that by aligning each struct to its size, which must be a power
1753     // of two.
1754     if (TargetTriple.isOSBinFormatCOFF())
1755       Metadata->setAlignment(SizeOfGlobalStruct);
1756     else
1757       Metadata->setAlignment(1); // Don't leave padding in between.
1758 
1759     // On platforms that support comdats, put the metadata and the
1760     // instrumented global in the same group. This ensures that the metadata
1761     // is discarded if the instrumented global is discarded.
1762     if (UseComdatMetadata) {
1763       assert(G->hasComdat());
1764       Metadata->setComdat(G->getComdat());
1765       continue;
1766     }
1767     assert(UseMachOGlobalsSection);
1768 
1769     // On recent Mach-O platforms, we emit the global metadata in a way that
1770     // allows the linker to properly strip dead globals.
1771     auto LivenessBinder = ConstantStruct::get(
1772         LivenessTy, Initializer->getAggregateElement(0u),
1773         ConstantExpr::getPointerCast(Metadata, IntptrTy), nullptr);
1774     GlobalVariable *Liveness = new GlobalVariable(
1775         M, LivenessTy, false, GlobalVariable::InternalLinkage, LivenessBinder,
1776         Twine("__asan_binder_") + G->getName());
1777     Liveness->setSection("__DATA,__asan_liveness,regular,live_support");
1778     LivenessGlobals[i] = Liveness;
1779   }
1780 
1781   // Create calls for poisoning before initializers run and unpoisoning after.
1782   if (HasDynamicallyInitializedGlobals)
1783     createInitializerPoisonCalls(M, ModuleName);
1784 
1785   // Platforms with a dedicated metadata section don't need to emit any more
1786   // code.
1787   if (UseComdatMetadata)
1788     return true;
1789 
1790   GlobalVariable *AllGlobals = nullptr;
1791   GlobalVariable *RegisteredFlag = nullptr;
1792 
1793   if (UseMachOGlobalsSection) {
1794     // RegisteredFlag serves two purposes. First, we can pass it to dladdr()
1795     // to look up the loaded image that contains it. Second, we can store in it
1796     // whether registration has already occurred, to prevent duplicate
1797     // registration.
1798     //
1799     // common linkage ensures that there is only one global per shared library.
1800     RegisteredFlag = new GlobalVariable(
1801         M, IntptrTy, false, GlobalVariable::CommonLinkage,
1802         ConstantInt::get(IntptrTy, 0), kAsanGlobalsRegisteredFlagName);
1803 
1804     // Update llvm.compiler.used, adding the new liveness globals. This is
1805     // needed so that during LTO these variables stay alive. The alternative
1806     // would be to have the linker handling the LTO symbols, but libLTO
1807     // current API does not expose access to the section for each symbol.
1808     if (!LivenessGlobals.empty())
1809       appendToCompilerUsed(M, LivenessGlobals);
1810   } else if (UseMetadataArray) {
1811     // On platforms that don't have a custom metadata section, we emit an array
1812     // of global metadata structures.
1813     ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
1814     AllGlobals = new GlobalVariable(
1815         M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
1816         ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
1817   }
1818 
1819   // Create a call to register the globals with the runtime.
1820   if (UseMachOGlobalsSection) {
1821     IRB.CreateCall(AsanRegisterImageGlobals,
1822                    {IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
1823   } else {
1824     IRB.CreateCall(AsanRegisterGlobals,
1825                    {IRB.CreatePointerCast(AllGlobals, IntptrTy),
1826                     ConstantInt::get(IntptrTy, n)});
1827   }
1828 
1829   // We also need to unregister globals at the end, e.g., when a shared library
1830   // gets closed.
1831   Function *AsanDtorFunction =
1832       Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
1833                        GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
1834   BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
1835   IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
1836 
1837   if (UseMachOGlobalsSection) {
1838     IRB_Dtor.CreateCall(AsanUnregisterImageGlobals,
1839                         {IRB.CreatePointerCast(RegisteredFlag, IntptrTy)});
1840   } else {
1841     IRB_Dtor.CreateCall(AsanUnregisterGlobals,
1842                         {IRB.CreatePointerCast(AllGlobals, IntptrTy),
1843                          ConstantInt::get(IntptrTy, n)});
1844   }
1845 
1846   appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
1847 
1848   DEBUG(dbgs() << M);
1849   return true;
1850 }
1851 
1852 bool AddressSanitizerModule::runOnModule(Module &M) {
1853   C = &(M.getContext());
1854   int LongSize = M.getDataLayout().getPointerSizeInBits();
1855   IntptrTy = Type::getIntNTy(*C, LongSize);
1856   TargetTriple = Triple(M.getTargetTriple());
1857   Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
1858   initializeCallbacks(M);
1859 
1860   bool Changed = false;
1861 
1862   // TODO(glider): temporarily disabled globals instrumentation for KASan.
1863   if (ClGlobals && !CompileKernel) {
1864     Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
1865     assert(CtorFunc);
1866     IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
1867     Changed |= InstrumentGlobals(IRB, M);
1868   }
1869 
1870   return Changed;
1871 }
1872 
1873 void AddressSanitizer::initializeCallbacks(Module &M) {
1874   IRBuilder<> IRB(*C);
1875   // Create __asan_report* callbacks.
1876   // IsWrite, TypeSize and Exp are encoded in the function name.
1877   for (int Exp = 0; Exp < 2; Exp++) {
1878     for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
1879       const std::string TypeStr = AccessIsWrite ? "store" : "load";
1880       const std::string ExpStr = Exp ? "exp_" : "";
1881       const std::string SuffixStr = CompileKernel ? "N" : "_n";
1882       const std::string EndingStr = Recover ? "_noabort" : "";
1883       Type *ExpType = Exp ? Type::getInt32Ty(*C) : nullptr;
1884       AsanErrorCallbackSized[AccessIsWrite][Exp] =
1885           checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1886               kAsanReportErrorTemplate + ExpStr + TypeStr + SuffixStr + EndingStr,
1887               IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr));
1888       AsanMemoryAccessCallbackSized[AccessIsWrite][Exp] =
1889           checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1890               ClMemoryAccessCallbackPrefix + ExpStr + TypeStr + "N" + EndingStr,
1891               IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr));
1892       for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
1893            AccessSizeIndex++) {
1894         const std::string Suffix = TypeStr + itostr(1ULL << AccessSizeIndex);
1895         AsanErrorCallback[AccessIsWrite][Exp][AccessSizeIndex] =
1896             checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1897                 kAsanReportErrorTemplate + ExpStr + Suffix + EndingStr,
1898                 IRB.getVoidTy(), IntptrTy, ExpType, nullptr));
1899         AsanMemoryAccessCallback[AccessIsWrite][Exp][AccessSizeIndex] =
1900             checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1901                 ClMemoryAccessCallbackPrefix + ExpStr + Suffix + EndingStr,
1902                 IRB.getVoidTy(), IntptrTy, ExpType, nullptr));
1903       }
1904     }
1905   }
1906 
1907   const std::string MemIntrinCallbackPrefix =
1908       CompileKernel ? std::string("") : ClMemoryAccessCallbackPrefix;
1909   AsanMemmove = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1910       MemIntrinCallbackPrefix + "memmove", IRB.getInt8PtrTy(),
1911       IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
1912   AsanMemcpy = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1913       MemIntrinCallbackPrefix + "memcpy", IRB.getInt8PtrTy(),
1914       IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
1915   AsanMemset = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1916       MemIntrinCallbackPrefix + "memset", IRB.getInt8PtrTy(),
1917       IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy, nullptr));
1918 
1919   AsanHandleNoReturnFunc = checkSanitizerInterfaceFunction(
1920       M.getOrInsertFunction(kAsanHandleNoReturnName, IRB.getVoidTy(), nullptr));
1921 
1922   AsanPtrCmpFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1923       kAsanPtrCmp, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1924   AsanPtrSubFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1925       kAsanPtrSub, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1926   // We insert an empty inline asm after __asan_report* to avoid callback merge.
1927   EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
1928                             StringRef(""), StringRef(""),
1929                             /*hasSideEffects=*/true);
1930 }
1931 
1932 // virtual
1933 bool AddressSanitizer::doInitialization(Module &M) {
1934   // Initialize the private fields. No one has accessed them before.
1935 
1936   GlobalsMD.init(M);
1937 
1938   C = &(M.getContext());
1939   LongSize = M.getDataLayout().getPointerSizeInBits();
1940   IntptrTy = Type::getIntNTy(*C, LongSize);
1941   TargetTriple = Triple(M.getTargetTriple());
1942 
1943   if (!CompileKernel) {
1944     std::tie(AsanCtorFunction, AsanInitFunction) =
1945         createSanitizerCtorAndInitFunctions(
1946             M, kAsanModuleCtorName, kAsanInitName,
1947             /*InitArgTypes=*/{}, /*InitArgs=*/{}, kAsanVersionCheckName);
1948     appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
1949   }
1950   Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
1951   return true;
1952 }
1953 
1954 bool AddressSanitizer::doFinalization(Module &M) {
1955   GlobalsMD.reset();
1956   return false;
1957 }
1958 
1959 bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
1960   // For each NSObject descendant having a +load method, this method is invoked
1961   // by the ObjC runtime before any of the static constructors is called.
1962   // Therefore we need to instrument such methods with a call to __asan_init
1963   // at the beginning in order to initialize our runtime before any access to
1964   // the shadow memory.
1965   // We cannot just ignore these methods, because they may call other
1966   // instrumented functions.
1967   if (F.getName().find(" load]") != std::string::npos) {
1968     IRBuilder<> IRB(&F.front(), F.front().begin());
1969     IRB.CreateCall(AsanInitFunction, {});
1970     return true;
1971   }
1972   return false;
1973 }
1974 
1975 void AddressSanitizer::maybeInsertDynamicShadowAtFunctionEntry(Function &F) {
1976   // Generate code only when dynamic addressing is needed.
1977   if (Mapping.Offset != kDynamicShadowSentinel)
1978     return;
1979 
1980   IRBuilder<> IRB(&F.front().front());
1981   Value *GlobalDynamicAddress = F.getParent()->getOrInsertGlobal(
1982       kAsanShadowMemoryDynamicAddress, IntptrTy);
1983   LocalDynamicShadow = IRB.CreateLoad(GlobalDynamicAddress);
1984 }
1985 
1986 void AddressSanitizer::markEscapedLocalAllocas(Function &F) {
1987   // Find the one possible call to llvm.localescape and pre-mark allocas passed
1988   // to it as uninteresting. This assumes we haven't started processing allocas
1989   // yet. This check is done up front because iterating the use list in
1990   // isInterestingAlloca would be algorithmically slower.
1991   assert(ProcessedAllocas.empty() && "must process localescape before allocas");
1992 
1993   // Try to get the declaration of llvm.localescape. If it's not in the module,
1994   // we can exit early.
1995   if (!F.getParent()->getFunction("llvm.localescape")) return;
1996 
1997   // Look for a call to llvm.localescape call in the entry block. It can't be in
1998   // any other block.
1999   for (Instruction &I : F.getEntryBlock()) {
2000     IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
2001     if (II && II->getIntrinsicID() == Intrinsic::localescape) {
2002       // We found a call. Mark all the allocas passed in as uninteresting.
2003       for (Value *Arg : II->arg_operands()) {
2004         AllocaInst *AI = dyn_cast<AllocaInst>(Arg->stripPointerCasts());
2005         assert(AI && AI->isStaticAlloca() &&
2006                "non-static alloca arg to localescape");
2007         ProcessedAllocas[AI] = false;
2008       }
2009       break;
2010     }
2011   }
2012 }
2013 
2014 bool AddressSanitizer::runOnFunction(Function &F) {
2015   if (&F == AsanCtorFunction) return false;
2016   if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
2017   if (!ClDebugFunc.empty() && ClDebugFunc == F.getName()) return false;
2018   if (F.getName().startswith("__asan_")) return false;
2019 
2020   bool FunctionModified = false;
2021 
2022   // If needed, insert __asan_init before checking for SanitizeAddress attr.
2023   // This function needs to be called even if the function body is not
2024   // instrumented.
2025   if (maybeInsertAsanInitAtFunctionEntry(F))
2026     FunctionModified = true;
2027 
2028   // Leave if the function doesn't need instrumentation.
2029   if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return FunctionModified;
2030 
2031   DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
2032 
2033   initializeCallbacks(*F.getParent());
2034   DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
2035 
2036   FunctionStateRAII CleanupObj(this);
2037 
2038   maybeInsertDynamicShadowAtFunctionEntry(F);
2039 
2040   // We can't instrument allocas used with llvm.localescape. Only static allocas
2041   // can be passed to that intrinsic.
2042   markEscapedLocalAllocas(F);
2043 
2044   // We want to instrument every address only once per basic block (unless there
2045   // are calls between uses).
2046   SmallSet<Value *, 16> TempsToInstrument;
2047   SmallVector<Instruction *, 16> ToInstrument;
2048   SmallVector<Instruction *, 8> NoReturnCalls;
2049   SmallVector<BasicBlock *, 16> AllBlocks;
2050   SmallVector<Instruction *, 16> PointerComparisonsOrSubtracts;
2051   int NumAllocas = 0;
2052   bool IsWrite;
2053   unsigned Alignment;
2054   uint64_t TypeSize;
2055   const TargetLibraryInfo *TLI =
2056       &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
2057 
2058   // Fill the set of memory operations to instrument.
2059   for (auto &BB : F) {
2060     AllBlocks.push_back(&BB);
2061     TempsToInstrument.clear();
2062     int NumInsnsPerBB = 0;
2063     for (auto &Inst : BB) {
2064       if (LooksLikeCodeInBug11395(&Inst)) return false;
2065       if (Value *Addr = isInterestingMemoryAccess(&Inst, &IsWrite, &TypeSize,
2066                                                   &Alignment)) {
2067         if (ClOpt && ClOptSameTemp) {
2068           if (!TempsToInstrument.insert(Addr).second)
2069             continue;  // We've seen this temp in the current BB.
2070         }
2071       } else if (ClInvalidPointerPairs &&
2072                  isInterestingPointerComparisonOrSubtraction(&Inst)) {
2073         PointerComparisonsOrSubtracts.push_back(&Inst);
2074         continue;
2075       } else if (isa<MemIntrinsic>(Inst)) {
2076         // ok, take it.
2077       } else {
2078         if (isa<AllocaInst>(Inst)) NumAllocas++;
2079         CallSite CS(&Inst);
2080         if (CS) {
2081           // A call inside BB.
2082           TempsToInstrument.clear();
2083           if (CS.doesNotReturn()) NoReturnCalls.push_back(CS.getInstruction());
2084         }
2085         if (CallInst *CI = dyn_cast<CallInst>(&Inst))
2086           maybeMarkSanitizerLibraryCallNoBuiltin(CI, TLI);
2087         continue;
2088       }
2089       ToInstrument.push_back(&Inst);
2090       NumInsnsPerBB++;
2091       if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB) break;
2092     }
2093   }
2094 
2095   bool UseCalls =
2096       CompileKernel ||
2097       (ClInstrumentationWithCallsThreshold >= 0 &&
2098        ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold);
2099   const DataLayout &DL = F.getParent()->getDataLayout();
2100   ObjectSizeOffsetVisitor ObjSizeVis(DL, TLI, F.getContext(),
2101                                      /*RoundToAlign=*/true);
2102 
2103   // Instrument.
2104   int NumInstrumented = 0;
2105   for (auto Inst : ToInstrument) {
2106     if (ClDebugMin < 0 || ClDebugMax < 0 ||
2107         (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
2108       if (isInterestingMemoryAccess(Inst, &IsWrite, &TypeSize, &Alignment))
2109         instrumentMop(ObjSizeVis, Inst, UseCalls,
2110                       F.getParent()->getDataLayout());
2111       else
2112         instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
2113     }
2114     NumInstrumented++;
2115   }
2116 
2117   FunctionStackPoisoner FSP(F, *this);
2118   bool ChangedStack = FSP.runOnFunction();
2119 
2120   // We must unpoison the stack before every NoReturn call (throw, _exit, etc).
2121   // See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
2122   for (auto CI : NoReturnCalls) {
2123     IRBuilder<> IRB(CI);
2124     IRB.CreateCall(AsanHandleNoReturnFunc, {});
2125   }
2126 
2127   for (auto Inst : PointerComparisonsOrSubtracts) {
2128     instrumentPointerComparisonOrSubtraction(Inst);
2129     NumInstrumented++;
2130   }
2131 
2132   if (NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty())
2133     FunctionModified = true;
2134 
2135   DEBUG(dbgs() << "ASAN done instrumenting: " << FunctionModified << " "
2136                << F << "\n");
2137 
2138   return FunctionModified;
2139 }
2140 
2141 // Workaround for bug 11395: we don't want to instrument stack in functions
2142 // with large assembly blobs (32-bit only), otherwise reg alloc may crash.
2143 // FIXME: remove once the bug 11395 is fixed.
2144 bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
2145   if (LongSize != 32) return false;
2146   CallInst *CI = dyn_cast<CallInst>(I);
2147   if (!CI || !CI->isInlineAsm()) return false;
2148   if (CI->getNumArgOperands() <= 5) return false;
2149   // We have inline assembly with quite a few arguments.
2150   return true;
2151 }
2152 
2153 void FunctionStackPoisoner::initializeCallbacks(Module &M) {
2154   IRBuilder<> IRB(*C);
2155   for (int i = 0; i <= kMaxAsanStackMallocSizeClass; i++) {
2156     std::string Suffix = itostr(i);
2157     AsanStackMallocFunc[i] = checkSanitizerInterfaceFunction(
2158         M.getOrInsertFunction(kAsanStackMallocNameTemplate + Suffix, IntptrTy,
2159                               IntptrTy, nullptr));
2160     AsanStackFreeFunc[i] = checkSanitizerInterfaceFunction(
2161         M.getOrInsertFunction(kAsanStackFreeNameTemplate + Suffix,
2162                               IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
2163   }
2164   if (ASan.UseAfterScope) {
2165     AsanPoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
2166         M.getOrInsertFunction(kAsanPoisonStackMemoryName, IRB.getVoidTy(),
2167                               IntptrTy, IntptrTy, nullptr));
2168     AsanUnpoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
2169         M.getOrInsertFunction(kAsanUnpoisonStackMemoryName, IRB.getVoidTy(),
2170                               IntptrTy, IntptrTy, nullptr));
2171   }
2172 
2173   for (size_t Val : {0x00, 0xf1, 0xf2, 0xf3, 0xf5, 0xf8}) {
2174     std::ostringstream Name;
2175     Name << kAsanSetShadowPrefix;
2176     Name << std::setw(2) << std::setfill('0') << std::hex << Val;
2177     AsanSetShadowFunc[Val] =
2178         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
2179             Name.str(), IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
2180   }
2181 
2182   AsanAllocaPoisonFunc = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
2183       kAsanAllocaPoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
2184   AsanAllocasUnpoisonFunc =
2185       checkSanitizerInterfaceFunction(M.getOrInsertFunction(
2186           kAsanAllocasUnpoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
2187 }
2188 
2189 void FunctionStackPoisoner::copyToShadowInline(ArrayRef<uint8_t> ShadowMask,
2190                                                ArrayRef<uint8_t> ShadowBytes,
2191                                                size_t Begin, size_t End,
2192                                                IRBuilder<> &IRB,
2193                                                Value *ShadowBase) {
2194   if (Begin >= End)
2195     return;
2196 
2197   const size_t LargestStoreSizeInBytes =
2198       std::min<size_t>(sizeof(uint64_t), ASan.LongSize / 8);
2199 
2200   const bool IsLittleEndian = F.getParent()->getDataLayout().isLittleEndian();
2201 
2202   // Poison given range in shadow using larges store size with out leading and
2203   // trailing zeros in ShadowMask. Zeros never change, so they need neither
2204   // poisoning nor up-poisoning. Still we don't mind if some of them get into a
2205   // middle of a store.
2206   for (size_t i = Begin; i < End;) {
2207     if (!ShadowMask[i]) {
2208       assert(!ShadowBytes[i]);
2209       ++i;
2210       continue;
2211     }
2212 
2213     size_t StoreSizeInBytes = LargestStoreSizeInBytes;
2214     // Fit store size into the range.
2215     while (StoreSizeInBytes > End - i)
2216       StoreSizeInBytes /= 2;
2217 
2218     // Minimize store size by trimming trailing zeros.
2219     for (size_t j = StoreSizeInBytes - 1; j && !ShadowMask[i + j]; --j) {
2220       while (j <= StoreSizeInBytes / 2)
2221         StoreSizeInBytes /= 2;
2222     }
2223 
2224     uint64_t Val = 0;
2225     for (size_t j = 0; j < StoreSizeInBytes; j++) {
2226       if (IsLittleEndian)
2227         Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
2228       else
2229         Val = (Val << 8) | ShadowBytes[i + j];
2230     }
2231 
2232     Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
2233     Value *Poison = IRB.getIntN(StoreSizeInBytes * 8, Val);
2234     IRB.CreateAlignedStore(
2235         Poison, IRB.CreateIntToPtr(Ptr, Poison->getType()->getPointerTo()), 1);
2236 
2237     i += StoreSizeInBytes;
2238   }
2239 }
2240 
2241 void FunctionStackPoisoner::copyToShadow(ArrayRef<uint8_t> ShadowMask,
2242                                          ArrayRef<uint8_t> ShadowBytes,
2243                                          IRBuilder<> &IRB, Value *ShadowBase) {
2244   copyToShadow(ShadowMask, ShadowBytes, 0, ShadowMask.size(), IRB, ShadowBase);
2245 }
2246 
2247 void FunctionStackPoisoner::copyToShadow(ArrayRef<uint8_t> ShadowMask,
2248                                          ArrayRef<uint8_t> ShadowBytes,
2249                                          size_t Begin, size_t End,
2250                                          IRBuilder<> &IRB, Value *ShadowBase) {
2251   assert(ShadowMask.size() == ShadowBytes.size());
2252   size_t Done = Begin;
2253   for (size_t i = Begin, j = Begin + 1; i < End; i = j++) {
2254     if (!ShadowMask[i]) {
2255       assert(!ShadowBytes[i]);
2256       continue;
2257     }
2258     uint8_t Val = ShadowBytes[i];
2259     if (!AsanSetShadowFunc[Val])
2260       continue;
2261 
2262     // Skip same values.
2263     for (; j < End && ShadowMask[j] && Val == ShadowBytes[j]; ++j) {
2264     }
2265 
2266     if (j - i >= ClMaxInlinePoisoningSize) {
2267       copyToShadowInline(ShadowMask, ShadowBytes, Done, i, IRB, ShadowBase);
2268       IRB.CreateCall(AsanSetShadowFunc[Val],
2269                      {IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i)),
2270                       ConstantInt::get(IntptrTy, j - i)});
2271       Done = j;
2272     }
2273   }
2274 
2275   copyToShadowInline(ShadowMask, ShadowBytes, Done, End, IRB, ShadowBase);
2276 }
2277 
2278 // Fake stack allocator (asan_fake_stack.h) has 11 size classes
2279 // for every power of 2 from kMinStackMallocSize to kMaxAsanStackMallocSizeClass
2280 static int StackMallocSizeClass(uint64_t LocalStackSize) {
2281   assert(LocalStackSize <= kMaxStackMallocSize);
2282   uint64_t MaxSize = kMinStackMallocSize;
2283   for (int i = 0;; i++, MaxSize *= 2)
2284     if (LocalStackSize <= MaxSize) return i;
2285   llvm_unreachable("impossible LocalStackSize");
2286 }
2287 
2288 PHINode *FunctionStackPoisoner::createPHI(IRBuilder<> &IRB, Value *Cond,
2289                                           Value *ValueIfTrue,
2290                                           Instruction *ThenTerm,
2291                                           Value *ValueIfFalse) {
2292   PHINode *PHI = IRB.CreatePHI(IntptrTy, 2);
2293   BasicBlock *CondBlock = cast<Instruction>(Cond)->getParent();
2294   PHI->addIncoming(ValueIfFalse, CondBlock);
2295   BasicBlock *ThenBlock = ThenTerm->getParent();
2296   PHI->addIncoming(ValueIfTrue, ThenBlock);
2297   return PHI;
2298 }
2299 
2300 Value *FunctionStackPoisoner::createAllocaForLayout(
2301     IRBuilder<> &IRB, const ASanStackFrameLayout &L, bool Dynamic) {
2302   AllocaInst *Alloca;
2303   if (Dynamic) {
2304     Alloca = IRB.CreateAlloca(IRB.getInt8Ty(),
2305                               ConstantInt::get(IRB.getInt64Ty(), L.FrameSize),
2306                               "MyAlloca");
2307   } else {
2308     Alloca = IRB.CreateAlloca(ArrayType::get(IRB.getInt8Ty(), L.FrameSize),
2309                               nullptr, "MyAlloca");
2310     assert(Alloca->isStaticAlloca());
2311   }
2312   assert((ClRealignStack & (ClRealignStack - 1)) == 0);
2313   size_t FrameAlignment = std::max(L.FrameAlignment, (size_t)ClRealignStack);
2314   Alloca->setAlignment(FrameAlignment);
2315   return IRB.CreatePointerCast(Alloca, IntptrTy);
2316 }
2317 
2318 void FunctionStackPoisoner::createDynamicAllocasInitStorage() {
2319   BasicBlock &FirstBB = *F.begin();
2320   IRBuilder<> IRB(dyn_cast<Instruction>(FirstBB.begin()));
2321   DynamicAllocaLayout = IRB.CreateAlloca(IntptrTy, nullptr);
2322   IRB.CreateStore(Constant::getNullValue(IntptrTy), DynamicAllocaLayout);
2323   DynamicAllocaLayout->setAlignment(32);
2324 }
2325 
2326 void FunctionStackPoisoner::processDynamicAllocas() {
2327   if (!ClInstrumentDynamicAllocas || DynamicAllocaVec.empty()) {
2328     assert(DynamicAllocaPoisonCallVec.empty());
2329     return;
2330   }
2331 
2332   // Insert poison calls for lifetime intrinsics for dynamic allocas.
2333   for (const auto &APC : DynamicAllocaPoisonCallVec) {
2334     assert(APC.InsBefore);
2335     assert(APC.AI);
2336     assert(ASan.isInterestingAlloca(*APC.AI));
2337     assert(!APC.AI->isStaticAlloca());
2338 
2339     IRBuilder<> IRB(APC.InsBefore);
2340     poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison);
2341     // Dynamic allocas will be unpoisoned unconditionally below in
2342     // unpoisonDynamicAllocas.
2343     // Flag that we need unpoison static allocas.
2344   }
2345 
2346   // Handle dynamic allocas.
2347   createDynamicAllocasInitStorage();
2348   for (auto &AI : DynamicAllocaVec)
2349     handleDynamicAllocaCall(AI);
2350   unpoisonDynamicAllocas();
2351 }
2352 
2353 void FunctionStackPoisoner::processStaticAllocas() {
2354   if (AllocaVec.empty()) {
2355     assert(StaticAllocaPoisonCallVec.empty());
2356     return;
2357   }
2358 
2359   int StackMallocIdx = -1;
2360   DebugLoc EntryDebugLocation;
2361   if (auto SP = F.getSubprogram())
2362     EntryDebugLocation = DebugLoc::get(SP->getScopeLine(), 0, SP);
2363 
2364   Instruction *InsBefore = AllocaVec[0];
2365   IRBuilder<> IRB(InsBefore);
2366   IRB.SetCurrentDebugLocation(EntryDebugLocation);
2367 
2368   // Make sure non-instrumented allocas stay in the entry block. Otherwise,
2369   // debug info is broken, because only entry-block allocas are treated as
2370   // regular stack slots.
2371   auto InsBeforeB = InsBefore->getParent();
2372   assert(InsBeforeB == &F.getEntryBlock());
2373   for (auto *AI : StaticAllocasToMoveUp)
2374     if (AI->getParent() == InsBeforeB)
2375       AI->moveBefore(InsBefore);
2376 
2377   // If we have a call to llvm.localescape, keep it in the entry block.
2378   if (LocalEscapeCall) LocalEscapeCall->moveBefore(InsBefore);
2379 
2380   SmallVector<ASanStackVariableDescription, 16> SVD;
2381   SVD.reserve(AllocaVec.size());
2382   for (AllocaInst *AI : AllocaVec) {
2383     ASanStackVariableDescription D = {AI->getName().data(),
2384                                       ASan.getAllocaSizeInBytes(*AI),
2385                                       0,
2386                                       AI->getAlignment(),
2387                                       AI,
2388                                       0,
2389                                       0};
2390     SVD.push_back(D);
2391   }
2392 
2393   // Minimal header size (left redzone) is 4 pointers,
2394   // i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms.
2395   size_t MinHeaderSize = ASan.LongSize / 2;
2396   const ASanStackFrameLayout &L =
2397       ComputeASanStackFrameLayout(SVD, 1ULL << Mapping.Scale, MinHeaderSize);
2398 
2399   // Build AllocaToSVDMap for ASanStackVariableDescription lookup.
2400   DenseMap<const AllocaInst *, ASanStackVariableDescription *> AllocaToSVDMap;
2401   for (auto &Desc : SVD)
2402     AllocaToSVDMap[Desc.AI] = &Desc;
2403 
2404   // Update SVD with information from lifetime intrinsics.
2405   for (const auto &APC : StaticAllocaPoisonCallVec) {
2406     assert(APC.InsBefore);
2407     assert(APC.AI);
2408     assert(ASan.isInterestingAlloca(*APC.AI));
2409     assert(APC.AI->isStaticAlloca());
2410 
2411     ASanStackVariableDescription &Desc = *AllocaToSVDMap[APC.AI];
2412     Desc.LifetimeSize = Desc.Size;
2413     if (const DILocation *FnLoc = EntryDebugLocation.get()) {
2414       if (const DILocation *LifetimeLoc = APC.InsBefore->getDebugLoc().get()) {
2415         if (LifetimeLoc->getFile() == FnLoc->getFile())
2416           if (unsigned Line = LifetimeLoc->getLine())
2417             Desc.Line = std::min(Desc.Line ? Desc.Line : Line, Line);
2418       }
2419     }
2420   }
2421 
2422   auto DescriptionString = ComputeASanStackFrameDescription(SVD);
2423   DEBUG(dbgs() << DescriptionString << " --- " << L.FrameSize << "\n");
2424   uint64_t LocalStackSize = L.FrameSize;
2425   bool DoStackMalloc = ClUseAfterReturn && !ASan.CompileKernel &&
2426                        LocalStackSize <= kMaxStackMallocSize;
2427   bool DoDynamicAlloca = ClDynamicAllocaStack;
2428   // Don't do dynamic alloca or stack malloc if:
2429   // 1) There is inline asm: too often it makes assumptions on which registers
2430   //    are available.
2431   // 2) There is a returns_twice call (typically setjmp), which is
2432   //    optimization-hostile, and doesn't play well with introduced indirect
2433   //    register-relative calculation of local variable addresses.
2434   DoDynamicAlloca &= !HasNonEmptyInlineAsm && !HasReturnsTwiceCall;
2435   DoStackMalloc &= !HasNonEmptyInlineAsm && !HasReturnsTwiceCall;
2436 
2437   Value *StaticAlloca =
2438       DoDynamicAlloca ? nullptr : createAllocaForLayout(IRB, L, false);
2439 
2440   Value *FakeStack;
2441   Value *LocalStackBase;
2442 
2443   if (DoStackMalloc) {
2444     // void *FakeStack = __asan_option_detect_stack_use_after_return
2445     //     ? __asan_stack_malloc_N(LocalStackSize)
2446     //     : nullptr;
2447     // void *LocalStackBase = (FakeStack) ? FakeStack : alloca(LocalStackSize);
2448     Constant *OptionDetectUseAfterReturn = F.getParent()->getOrInsertGlobal(
2449         kAsanOptionDetectUseAfterReturn, IRB.getInt32Ty());
2450     Value *UseAfterReturnIsEnabled =
2451         IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUseAfterReturn),
2452                          Constant::getNullValue(IRB.getInt32Ty()));
2453     Instruction *Term =
2454         SplitBlockAndInsertIfThen(UseAfterReturnIsEnabled, InsBefore, false);
2455     IRBuilder<> IRBIf(Term);
2456     IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
2457     StackMallocIdx = StackMallocSizeClass(LocalStackSize);
2458     assert(StackMallocIdx <= kMaxAsanStackMallocSizeClass);
2459     Value *FakeStackValue =
2460         IRBIf.CreateCall(AsanStackMallocFunc[StackMallocIdx],
2461                          ConstantInt::get(IntptrTy, LocalStackSize));
2462     IRB.SetInsertPoint(InsBefore);
2463     IRB.SetCurrentDebugLocation(EntryDebugLocation);
2464     FakeStack = createPHI(IRB, UseAfterReturnIsEnabled, FakeStackValue, Term,
2465                           ConstantInt::get(IntptrTy, 0));
2466 
2467     Value *NoFakeStack =
2468         IRB.CreateICmpEQ(FakeStack, Constant::getNullValue(IntptrTy));
2469     Term = SplitBlockAndInsertIfThen(NoFakeStack, InsBefore, false);
2470     IRBIf.SetInsertPoint(Term);
2471     IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
2472     Value *AllocaValue =
2473         DoDynamicAlloca ? createAllocaForLayout(IRBIf, L, true) : StaticAlloca;
2474     IRB.SetInsertPoint(InsBefore);
2475     IRB.SetCurrentDebugLocation(EntryDebugLocation);
2476     LocalStackBase = createPHI(IRB, NoFakeStack, AllocaValue, Term, FakeStack);
2477   } else {
2478     // void *FakeStack = nullptr;
2479     // void *LocalStackBase = alloca(LocalStackSize);
2480     FakeStack = ConstantInt::get(IntptrTy, 0);
2481     LocalStackBase =
2482         DoDynamicAlloca ? createAllocaForLayout(IRB, L, true) : StaticAlloca;
2483   }
2484 
2485   // Replace Alloca instructions with base+offset.
2486   for (const auto &Desc : SVD) {
2487     AllocaInst *AI = Desc.AI;
2488     Value *NewAllocaPtr = IRB.CreateIntToPtr(
2489         IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Desc.Offset)),
2490         AI->getType());
2491     replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB, /*Deref=*/true);
2492     AI->replaceAllUsesWith(NewAllocaPtr);
2493   }
2494 
2495   // The left-most redzone has enough space for at least 4 pointers.
2496   // Write the Magic value to redzone[0].
2497   Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
2498   IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
2499                   BasePlus0);
2500   // Write the frame description constant to redzone[1].
2501   Value *BasePlus1 = IRB.CreateIntToPtr(
2502       IRB.CreateAdd(LocalStackBase,
2503                     ConstantInt::get(IntptrTy, ASan.LongSize / 8)),
2504       IntptrPtrTy);
2505   GlobalVariable *StackDescriptionGlobal =
2506       createPrivateGlobalForString(*F.getParent(), DescriptionString,
2507                                    /*AllowMerging*/ true);
2508   Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal, IntptrTy);
2509   IRB.CreateStore(Description, BasePlus1);
2510   // Write the PC to redzone[2].
2511   Value *BasePlus2 = IRB.CreateIntToPtr(
2512       IRB.CreateAdd(LocalStackBase,
2513                     ConstantInt::get(IntptrTy, 2 * ASan.LongSize / 8)),
2514       IntptrPtrTy);
2515   IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
2516 
2517   const auto &ShadowAfterScope = GetShadowBytesAfterScope(SVD, L);
2518 
2519   // Poison the stack red zones at the entry.
2520   Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
2521   // As mask we must use most poisoned case: red zones and after scope.
2522   // As bytes we can use either the same or just red zones only.
2523   copyToShadow(ShadowAfterScope, ShadowAfterScope, IRB, ShadowBase);
2524 
2525   if (!StaticAllocaPoisonCallVec.empty()) {
2526     const auto &ShadowInScope = GetShadowBytes(SVD, L);
2527 
2528     // Poison static allocas near lifetime intrinsics.
2529     for (const auto &APC : StaticAllocaPoisonCallVec) {
2530       const ASanStackVariableDescription &Desc = *AllocaToSVDMap[APC.AI];
2531       assert(Desc.Offset % L.Granularity == 0);
2532       size_t Begin = Desc.Offset / L.Granularity;
2533       size_t End = Begin + (APC.Size + L.Granularity - 1) / L.Granularity;
2534 
2535       IRBuilder<> IRB(APC.InsBefore);
2536       copyToShadow(ShadowAfterScope,
2537                    APC.DoPoison ? ShadowAfterScope : ShadowInScope, Begin, End,
2538                    IRB, ShadowBase);
2539     }
2540   }
2541 
2542   SmallVector<uint8_t, 64> ShadowClean(ShadowAfterScope.size(), 0);
2543   SmallVector<uint8_t, 64> ShadowAfterReturn;
2544 
2545   // (Un)poison the stack before all ret instructions.
2546   for (auto Ret : RetVec) {
2547     IRBuilder<> IRBRet(Ret);
2548     // Mark the current frame as retired.
2549     IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
2550                        BasePlus0);
2551     if (DoStackMalloc) {
2552       assert(StackMallocIdx >= 0);
2553       // if FakeStack != 0  // LocalStackBase == FakeStack
2554       //     // In use-after-return mode, poison the whole stack frame.
2555       //     if StackMallocIdx <= 4
2556       //         // For small sizes inline the whole thing:
2557       //         memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize);
2558       //         **SavedFlagPtr(FakeStack) = 0
2559       //     else
2560       //         __asan_stack_free_N(FakeStack, LocalStackSize)
2561       // else
2562       //     <This is not a fake stack; unpoison the redzones>
2563       Value *Cmp =
2564           IRBRet.CreateICmpNE(FakeStack, Constant::getNullValue(IntptrTy));
2565       TerminatorInst *ThenTerm, *ElseTerm;
2566       SplitBlockAndInsertIfThenElse(Cmp, Ret, &ThenTerm, &ElseTerm);
2567 
2568       IRBuilder<> IRBPoison(ThenTerm);
2569       if (StackMallocIdx <= 4) {
2570         int ClassSize = kMinStackMallocSize << StackMallocIdx;
2571         ShadowAfterReturn.resize(ClassSize / L.Granularity,
2572                                  kAsanStackUseAfterReturnMagic);
2573         copyToShadow(ShadowAfterReturn, ShadowAfterReturn, IRBPoison,
2574                      ShadowBase);
2575         Value *SavedFlagPtrPtr = IRBPoison.CreateAdd(
2576             FakeStack,
2577             ConstantInt::get(IntptrTy, ClassSize - ASan.LongSize / 8));
2578         Value *SavedFlagPtr = IRBPoison.CreateLoad(
2579             IRBPoison.CreateIntToPtr(SavedFlagPtrPtr, IntptrPtrTy));
2580         IRBPoison.CreateStore(
2581             Constant::getNullValue(IRBPoison.getInt8Ty()),
2582             IRBPoison.CreateIntToPtr(SavedFlagPtr, IRBPoison.getInt8PtrTy()));
2583       } else {
2584         // For larger frames call __asan_stack_free_*.
2585         IRBPoison.CreateCall(
2586             AsanStackFreeFunc[StackMallocIdx],
2587             {FakeStack, ConstantInt::get(IntptrTy, LocalStackSize)});
2588       }
2589 
2590       IRBuilder<> IRBElse(ElseTerm);
2591       copyToShadow(ShadowAfterScope, ShadowClean, IRBElse, ShadowBase);
2592     } else {
2593       copyToShadow(ShadowAfterScope, ShadowClean, IRBRet, ShadowBase);
2594     }
2595   }
2596 
2597   // We are done. Remove the old unused alloca instructions.
2598   for (auto AI : AllocaVec) AI->eraseFromParent();
2599 }
2600 
2601 void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size,
2602                                          IRBuilder<> &IRB, bool DoPoison) {
2603   // For now just insert the call to ASan runtime.
2604   Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy);
2605   Value *SizeArg = ConstantInt::get(IntptrTy, Size);
2606   IRB.CreateCall(
2607       DoPoison ? AsanPoisonStackMemoryFunc : AsanUnpoisonStackMemoryFunc,
2608       {AddrArg, SizeArg});
2609 }
2610 
2611 // Handling llvm.lifetime intrinsics for a given %alloca:
2612 // (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca.
2613 // (2) if %size is constant, poison memory for llvm.lifetime.end (to detect
2614 //     invalid accesses) and unpoison it for llvm.lifetime.start (the memory
2615 //     could be poisoned by previous llvm.lifetime.end instruction, as the
2616 //     variable may go in and out of scope several times, e.g. in loops).
2617 // (3) if we poisoned at least one %alloca in a function,
2618 //     unpoison the whole stack frame at function exit.
2619 
2620 AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
2621   if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
2622     // We're interested only in allocas we can handle.
2623     return ASan.isInterestingAlloca(*AI) ? AI : nullptr;
2624   // See if we've already calculated (or started to calculate) alloca for a
2625   // given value.
2626   AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
2627   if (I != AllocaForValue.end()) return I->second;
2628   // Store 0 while we're calculating alloca for value V to avoid
2629   // infinite recursion if the value references itself.
2630   AllocaForValue[V] = nullptr;
2631   AllocaInst *Res = nullptr;
2632   if (CastInst *CI = dyn_cast<CastInst>(V))
2633     Res = findAllocaForValue(CI->getOperand(0));
2634   else if (PHINode *PN = dyn_cast<PHINode>(V)) {
2635     for (Value *IncValue : PN->incoming_values()) {
2636       // Allow self-referencing phi-nodes.
2637       if (IncValue == PN) continue;
2638       AllocaInst *IncValueAI = findAllocaForValue(IncValue);
2639       // AI for incoming values should exist and should all be equal.
2640       if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res))
2641         return nullptr;
2642       Res = IncValueAI;
2643     }
2644   } else if (GetElementPtrInst *EP = dyn_cast<GetElementPtrInst>(V)) {
2645     Res = findAllocaForValue(EP->getPointerOperand());
2646   } else {
2647     DEBUG(dbgs() << "Alloca search canceled on unknown instruction: " << *V << "\n");
2648   }
2649   if (Res) AllocaForValue[V] = Res;
2650   return Res;
2651 }
2652 
2653 void FunctionStackPoisoner::handleDynamicAllocaCall(AllocaInst *AI) {
2654   IRBuilder<> IRB(AI);
2655 
2656   const unsigned Align = std::max(kAllocaRzSize, AI->getAlignment());
2657   const uint64_t AllocaRedzoneMask = kAllocaRzSize - 1;
2658 
2659   Value *Zero = Constant::getNullValue(IntptrTy);
2660   Value *AllocaRzSize = ConstantInt::get(IntptrTy, kAllocaRzSize);
2661   Value *AllocaRzMask = ConstantInt::get(IntptrTy, AllocaRedzoneMask);
2662 
2663   // Since we need to extend alloca with additional memory to locate
2664   // redzones, and OldSize is number of allocated blocks with
2665   // ElementSize size, get allocated memory size in bytes by
2666   // OldSize * ElementSize.
2667   const unsigned ElementSize =
2668       F.getParent()->getDataLayout().getTypeAllocSize(AI->getAllocatedType());
2669   Value *OldSize =
2670       IRB.CreateMul(IRB.CreateIntCast(AI->getArraySize(), IntptrTy, false),
2671                     ConstantInt::get(IntptrTy, ElementSize));
2672 
2673   // PartialSize = OldSize % 32
2674   Value *PartialSize = IRB.CreateAnd(OldSize, AllocaRzMask);
2675 
2676   // Misalign = kAllocaRzSize - PartialSize;
2677   Value *Misalign = IRB.CreateSub(AllocaRzSize, PartialSize);
2678 
2679   // PartialPadding = Misalign != kAllocaRzSize ? Misalign : 0;
2680   Value *Cond = IRB.CreateICmpNE(Misalign, AllocaRzSize);
2681   Value *PartialPadding = IRB.CreateSelect(Cond, Misalign, Zero);
2682 
2683   // AdditionalChunkSize = Align + PartialPadding + kAllocaRzSize
2684   // Align is added to locate left redzone, PartialPadding for possible
2685   // partial redzone and kAllocaRzSize for right redzone respectively.
2686   Value *AdditionalChunkSize = IRB.CreateAdd(
2687       ConstantInt::get(IntptrTy, Align + kAllocaRzSize), PartialPadding);
2688 
2689   Value *NewSize = IRB.CreateAdd(OldSize, AdditionalChunkSize);
2690 
2691   // Insert new alloca with new NewSize and Align params.
2692   AllocaInst *NewAlloca = IRB.CreateAlloca(IRB.getInt8Ty(), NewSize);
2693   NewAlloca->setAlignment(Align);
2694 
2695   // NewAddress = Address + Align
2696   Value *NewAddress = IRB.CreateAdd(IRB.CreatePtrToInt(NewAlloca, IntptrTy),
2697                                     ConstantInt::get(IntptrTy, Align));
2698 
2699   // Insert __asan_alloca_poison call for new created alloca.
2700   IRB.CreateCall(AsanAllocaPoisonFunc, {NewAddress, OldSize});
2701 
2702   // Store the last alloca's address to DynamicAllocaLayout. We'll need this
2703   // for unpoisoning stuff.
2704   IRB.CreateStore(IRB.CreatePtrToInt(NewAlloca, IntptrTy), DynamicAllocaLayout);
2705 
2706   Value *NewAddressPtr = IRB.CreateIntToPtr(NewAddress, AI->getType());
2707 
2708   // Replace all uses of AddessReturnedByAlloca with NewAddressPtr.
2709   AI->replaceAllUsesWith(NewAddressPtr);
2710 
2711   // We are done. Erase old alloca from parent.
2712   AI->eraseFromParent();
2713 }
2714 
2715 // isSafeAccess returns true if Addr is always inbounds with respect to its
2716 // base object. For example, it is a field access or an array access with
2717 // constant inbounds index.
2718 bool AddressSanitizer::isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis,
2719                                     Value *Addr, uint64_t TypeSize) const {
2720   SizeOffsetType SizeOffset = ObjSizeVis.compute(Addr);
2721   if (!ObjSizeVis.bothKnown(SizeOffset)) return false;
2722   uint64_t Size = SizeOffset.first.getZExtValue();
2723   int64_t Offset = SizeOffset.second.getSExtValue();
2724   // Three checks are required to ensure safety:
2725   // . Offset >= 0  (since the offset is given from the base ptr)
2726   // . Size >= Offset  (unsigned)
2727   // . Size - Offset >= NeededSize  (unsigned)
2728   return Offset >= 0 && Size >= uint64_t(Offset) &&
2729          Size - uint64_t(Offset) >= TypeSize / 8;
2730 }
2731