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/Transforms/Instrumentation.h" 17 #include "llvm/ADT/ArrayRef.h" 18 #include "llvm/ADT/DenseMap.h" 19 #include "llvm/ADT/DenseSet.h" 20 #include "llvm/ADT/DepthFirstIterator.h" 21 #include "llvm/ADT/SmallSet.h" 22 #include "llvm/ADT/SmallString.h" 23 #include "llvm/ADT/SmallVector.h" 24 #include "llvm/ADT/Statistic.h" 25 #include "llvm/ADT/StringExtras.h" 26 #include "llvm/ADT/Triple.h" 27 #include "llvm/Analysis/MemoryBuiltins.h" 28 #include "llvm/Analysis/TargetLibraryInfo.h" 29 #include "llvm/Analysis/ValueTracking.h" 30 #include "llvm/IR/CallSite.h" 31 #include "llvm/IR/DIBuilder.h" 32 #include "llvm/IR/DataLayout.h" 33 #include "llvm/IR/Dominators.h" 34 #include "llvm/IR/Function.h" 35 #include "llvm/IR/IRBuilder.h" 36 #include "llvm/IR/InlineAsm.h" 37 #include "llvm/IR/InstVisitor.h" 38 #include "llvm/IR/IntrinsicInst.h" 39 #include "llvm/IR/LLVMContext.h" 40 #include "llvm/IR/MDBuilder.h" 41 #include "llvm/IR/Module.h" 42 #include "llvm/IR/Type.h" 43 #include "llvm/MC/MCSectionMachO.h" 44 #include "llvm/Support/CommandLine.h" 45 #include "llvm/Support/DataTypes.h" 46 #include "llvm/Support/Debug.h" 47 #include "llvm/Support/Endian.h" 48 #include "llvm/Support/SwapByteOrder.h" 49 #include "llvm/Support/raw_ostream.h" 50 #include "llvm/Transforms/Scalar.h" 51 #include "llvm/Transforms/Utils/ASanStackFrameLayout.h" 52 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 53 #include "llvm/Transforms/Utils/Cloning.h" 54 #include "llvm/Transforms/Utils/Local.h" 55 #include "llvm/Transforms/Utils/ModuleUtils.h" 56 #include "llvm/Transforms/Utils/PromoteMemToReg.h" 57 #include <algorithm> 58 #include <string> 59 #include <system_error> 60 61 using namespace llvm; 62 63 #define DEBUG_TYPE "asan" 64 65 static const uint64_t kDefaultShadowScale = 3; 66 static const uint64_t kDefaultShadowOffset32 = 1ULL << 29; 67 static const uint64_t kIOSShadowOffset32 = 1ULL << 30; 68 static const uint64_t kDefaultShadowOffset64 = 1ULL << 44; 69 static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000; // < 2G. 70 static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41; 71 static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000; 72 static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 37; 73 static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36; 74 static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30; 75 static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46; 76 static const uint64_t kWindowsShadowOffset32 = 3ULL << 28; 77 78 static const size_t kMinStackMallocSize = 1 << 6; // 64B 79 static const size_t kMaxStackMallocSize = 1 << 16; // 64K 80 static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3; 81 static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E; 82 83 static const char *const kAsanModuleCtorName = "asan.module_ctor"; 84 static const char *const kAsanModuleDtorName = "asan.module_dtor"; 85 static const uint64_t kAsanCtorAndDtorPriority = 1; 86 static const char *const kAsanReportErrorTemplate = "__asan_report_"; 87 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals"; 88 static const char *const kAsanUnregisterGlobalsName = 89 "__asan_unregister_globals"; 90 static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init"; 91 static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init"; 92 static const char *const kAsanInitName = "__asan_init_v5"; 93 static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp"; 94 static const char *const kAsanPtrSub = "__sanitizer_ptr_sub"; 95 static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return"; 96 static const int kMaxAsanStackMallocSizeClass = 10; 97 static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_"; 98 static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_"; 99 static const char *const kAsanGenPrefix = "__asan_gen_"; 100 static const char *const kSanCovGenPrefix = "__sancov_gen_"; 101 static const char *const kAsanPoisonStackMemoryName = 102 "__asan_poison_stack_memory"; 103 static const char *const kAsanUnpoisonStackMemoryName = 104 "__asan_unpoison_stack_memory"; 105 106 static const char *const kAsanOptionDetectUAR = 107 "__asan_option_detect_stack_use_after_return"; 108 109 static const char *const kAsanAllocaPoison = "__asan_alloca_poison"; 110 static const char *const kAsanAllocasUnpoison = "__asan_allocas_unpoison"; 111 112 // Accesses sizes are powers of two: 1, 2, 4, 8, 16. 113 static const size_t kNumberOfAccessSizes = 5; 114 115 static const unsigned kAllocaRzSize = 32; 116 117 // Command-line flags. 118 119 // This flag may need to be replaced with -f[no-]asan-reads. 120 static cl::opt<bool> ClInstrumentReads("asan-instrument-reads", 121 cl::desc("instrument read instructions"), 122 cl::Hidden, cl::init(true)); 123 static cl::opt<bool> ClInstrumentWrites( 124 "asan-instrument-writes", cl::desc("instrument write instructions"), 125 cl::Hidden, cl::init(true)); 126 static cl::opt<bool> ClInstrumentAtomics( 127 "asan-instrument-atomics", 128 cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden, 129 cl::init(true)); 130 static cl::opt<bool> ClAlwaysSlowPath( 131 "asan-always-slow-path", 132 cl::desc("use instrumentation with slow path for all accesses"), cl::Hidden, 133 cl::init(false)); 134 // This flag limits the number of instructions to be instrumented 135 // in any given BB. Normally, this should be set to unlimited (INT_MAX), 136 // but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary 137 // set it to 10000. 138 static cl::opt<int> ClMaxInsnsToInstrumentPerBB( 139 "asan-max-ins-per-bb", cl::init(10000), 140 cl::desc("maximal number of instructions to instrument in any given BB"), 141 cl::Hidden); 142 // This flag may need to be replaced with -f[no]asan-stack. 143 static cl::opt<bool> ClStack("asan-stack", cl::desc("Handle stack memory"), 144 cl::Hidden, cl::init(true)); 145 static cl::opt<bool> ClUseAfterReturn("asan-use-after-return", 146 cl::desc("Check return-after-free"), 147 cl::Hidden, cl::init(true)); 148 // This flag may need to be replaced with -f[no]asan-globals. 149 static cl::opt<bool> ClGlobals("asan-globals", 150 cl::desc("Handle global objects"), cl::Hidden, 151 cl::init(true)); 152 static cl::opt<bool> ClInitializers("asan-initialization-order", 153 cl::desc("Handle C++ initializer order"), 154 cl::Hidden, cl::init(true)); 155 static cl::opt<bool> ClInvalidPointerPairs( 156 "asan-detect-invalid-pointer-pair", 157 cl::desc("Instrument <, <=, >, >=, - with pointer operands"), cl::Hidden, 158 cl::init(false)); 159 static cl::opt<unsigned> ClRealignStack( 160 "asan-realign-stack", 161 cl::desc("Realign stack to the value of this flag (power of two)"), 162 cl::Hidden, cl::init(32)); 163 static cl::opt<int> ClInstrumentationWithCallsThreshold( 164 "asan-instrumentation-with-call-threshold", 165 cl::desc( 166 "If the function being instrumented contains more than " 167 "this number of memory accesses, use callbacks instead of " 168 "inline checks (-1 means never use callbacks)."), 169 cl::Hidden, cl::init(7000)); 170 static cl::opt<std::string> ClMemoryAccessCallbackPrefix( 171 "asan-memory-access-callback-prefix", 172 cl::desc("Prefix for memory access callbacks"), cl::Hidden, 173 cl::init("__asan_")); 174 static cl::opt<bool> ClInstrumentAllocas("asan-instrument-allocas", 175 cl::desc("instrument dynamic allocas"), 176 cl::Hidden, cl::init(false)); 177 static cl::opt<bool> ClSkipPromotableAllocas( 178 "asan-skip-promotable-allocas", 179 cl::desc("Do not instrument promotable allocas"), cl::Hidden, 180 cl::init(true)); 181 182 // These flags allow to change the shadow mapping. 183 // The shadow mapping looks like 184 // Shadow = (Mem >> scale) + (1 << offset_log) 185 static cl::opt<int> ClMappingScale("asan-mapping-scale", 186 cl::desc("scale of asan shadow mapping"), 187 cl::Hidden, cl::init(0)); 188 189 // Optimization flags. Not user visible, used mostly for testing 190 // and benchmarking the tool. 191 static cl::opt<bool> ClOpt("asan-opt", cl::desc("Optimize instrumentation"), 192 cl::Hidden, cl::init(true)); 193 static cl::opt<bool> ClOptSameTemp( 194 "asan-opt-same-temp", cl::desc("Instrument the same temp just once"), 195 cl::Hidden, cl::init(true)); 196 static cl::opt<bool> ClOptGlobals("asan-opt-globals", 197 cl::desc("Don't instrument scalar globals"), 198 cl::Hidden, cl::init(true)); 199 static cl::opt<bool> ClOptStack( 200 "asan-opt-stack", cl::desc("Don't instrument scalar stack variables"), 201 cl::Hidden, cl::init(false)); 202 203 static cl::opt<bool> ClCheckLifetime( 204 "asan-check-lifetime", 205 cl::desc("Use llvm.lifetime intrinsics to insert extra checks"), cl::Hidden, 206 cl::init(false)); 207 208 static cl::opt<bool> ClDynamicAllocaStack( 209 "asan-stack-dynamic-alloca", 210 cl::desc("Use dynamic alloca to represent stack variables"), cl::Hidden, 211 cl::init(true)); 212 213 static cl::opt<uint32_t> ClForceExperiment( 214 "asan-force-experiment", 215 cl::desc("Force optimization experiment (for testing)"), cl::Hidden, 216 cl::init(0)); 217 218 // Debug flags. 219 static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden, 220 cl::init(0)); 221 static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"), 222 cl::Hidden, cl::init(0)); 223 static cl::opt<std::string> ClDebugFunc("asan-debug-func", cl::Hidden, 224 cl::desc("Debug func")); 225 static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"), 226 cl::Hidden, cl::init(-1)); 227 static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"), 228 cl::Hidden, cl::init(-1)); 229 230 STATISTIC(NumInstrumentedReads, "Number of instrumented reads"); 231 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes"); 232 STATISTIC(NumOptimizedAccessesToGlobalVar, 233 "Number of optimized accesses to global vars"); 234 STATISTIC(NumOptimizedAccessesToStackVar, 235 "Number of optimized accesses to stack vars"); 236 237 namespace { 238 /// Frontend-provided metadata for source location. 239 struct LocationMetadata { 240 StringRef Filename; 241 int LineNo; 242 int ColumnNo; 243 244 LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {} 245 246 bool empty() const { return Filename.empty(); } 247 248 void parse(MDNode *MDN) { 249 assert(MDN->getNumOperands() == 3); 250 MDString *DIFilename = cast<MDString>(MDN->getOperand(0)); 251 Filename = DIFilename->getString(); 252 LineNo = 253 mdconst::extract<ConstantInt>(MDN->getOperand(1))->getLimitedValue(); 254 ColumnNo = 255 mdconst::extract<ConstantInt>(MDN->getOperand(2))->getLimitedValue(); 256 } 257 }; 258 259 /// Frontend-provided metadata for global variables. 260 class GlobalsMetadata { 261 public: 262 struct Entry { 263 Entry() : SourceLoc(), Name(), IsDynInit(false), IsBlacklisted(false) {} 264 LocationMetadata SourceLoc; 265 StringRef Name; 266 bool IsDynInit; 267 bool IsBlacklisted; 268 }; 269 270 GlobalsMetadata() : inited_(false) {} 271 272 void init(Module &M) { 273 assert(!inited_); 274 inited_ = true; 275 NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals"); 276 if (!Globals) return; 277 for (auto MDN : Globals->operands()) { 278 // Metadata node contains the global and the fields of "Entry". 279 assert(MDN->getNumOperands() == 5); 280 auto *GV = mdconst::extract_or_null<GlobalVariable>(MDN->getOperand(0)); 281 // The optimizer may optimize away a global entirely. 282 if (!GV) continue; 283 // We can already have an entry for GV if it was merged with another 284 // global. 285 Entry &E = Entries[GV]; 286 if (auto *Loc = cast_or_null<MDNode>(MDN->getOperand(1))) 287 E.SourceLoc.parse(Loc); 288 if (auto *Name = cast_or_null<MDString>(MDN->getOperand(2))) 289 E.Name = Name->getString(); 290 ConstantInt *IsDynInit = 291 mdconst::extract<ConstantInt>(MDN->getOperand(3)); 292 E.IsDynInit |= IsDynInit->isOne(); 293 ConstantInt *IsBlacklisted = 294 mdconst::extract<ConstantInt>(MDN->getOperand(4)); 295 E.IsBlacklisted |= IsBlacklisted->isOne(); 296 } 297 } 298 299 /// Returns metadata entry for a given global. 300 Entry get(GlobalVariable *G) const { 301 auto Pos = Entries.find(G); 302 return (Pos != Entries.end()) ? Pos->second : Entry(); 303 } 304 305 private: 306 bool inited_; 307 DenseMap<GlobalVariable *, Entry> Entries; 308 }; 309 310 /// This struct defines the shadow mapping using the rule: 311 /// shadow = (mem >> Scale) ADD-or-OR Offset. 312 struct ShadowMapping { 313 int Scale; 314 uint64_t Offset; 315 bool OrShadowOffset; 316 }; 317 318 static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize) { 319 bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android; 320 bool IsIOS = TargetTriple.isiOS(); 321 bool IsFreeBSD = TargetTriple.isOSFreeBSD(); 322 bool IsLinux = TargetTriple.isOSLinux(); 323 bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 || 324 TargetTriple.getArch() == llvm::Triple::ppc64le; 325 bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64; 326 bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips || 327 TargetTriple.getArch() == llvm::Triple::mipsel; 328 bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 || 329 TargetTriple.getArch() == llvm::Triple::mips64el; 330 bool IsAArch64 = TargetTriple.getArch() == llvm::Triple::aarch64; 331 bool IsWindows = TargetTriple.isOSWindows(); 332 333 ShadowMapping Mapping; 334 335 if (LongSize == 32) { 336 if (IsAndroid) 337 Mapping.Offset = 0; 338 else if (IsMIPS32) 339 Mapping.Offset = kMIPS32_ShadowOffset32; 340 else if (IsFreeBSD) 341 Mapping.Offset = kFreeBSD_ShadowOffset32; 342 else if (IsIOS) 343 Mapping.Offset = kIOSShadowOffset32; 344 else if (IsWindows) 345 Mapping.Offset = kWindowsShadowOffset32; 346 else 347 Mapping.Offset = kDefaultShadowOffset32; 348 } else { // LongSize == 64 349 if (IsPPC64) 350 Mapping.Offset = kPPC64_ShadowOffset64; 351 else if (IsFreeBSD) 352 Mapping.Offset = kFreeBSD_ShadowOffset64; 353 else if (IsLinux && IsX86_64) 354 Mapping.Offset = kSmallX86_64ShadowOffset; 355 else if (IsMIPS64) 356 Mapping.Offset = kMIPS64_ShadowOffset64; 357 else if (IsAArch64) 358 Mapping.Offset = kAArch64_ShadowOffset64; 359 else 360 Mapping.Offset = kDefaultShadowOffset64; 361 } 362 363 Mapping.Scale = kDefaultShadowScale; 364 if (ClMappingScale) { 365 Mapping.Scale = ClMappingScale; 366 } 367 368 // OR-ing shadow offset if more efficient (at least on x86) if the offset 369 // is a power of two, but on ppc64 we have to use add since the shadow 370 // offset is not necessary 1/8-th of the address space. 371 Mapping.OrShadowOffset = !IsPPC64 && !(Mapping.Offset & (Mapping.Offset - 1)); 372 373 return Mapping; 374 } 375 376 static size_t RedzoneSizeForScale(int MappingScale) { 377 // Redzone used for stack and globals is at least 32 bytes. 378 // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively. 379 return std::max(32U, 1U << MappingScale); 380 } 381 382 /// AddressSanitizer: instrument the code in module to find memory bugs. 383 struct AddressSanitizer : public FunctionPass { 384 AddressSanitizer() : FunctionPass(ID) { 385 initializeAddressSanitizerPass(*PassRegistry::getPassRegistry()); 386 } 387 const char *getPassName() const override { 388 return "AddressSanitizerFunctionPass"; 389 } 390 void getAnalysisUsage(AnalysisUsage &AU) const override { 391 AU.addRequired<DominatorTreeWrapperPass>(); 392 AU.addRequired<TargetLibraryInfoWrapperPass>(); 393 } 394 uint64_t getAllocaSizeInBytes(AllocaInst *AI) const { 395 Type *Ty = AI->getAllocatedType(); 396 uint64_t SizeInBytes = 397 AI->getModule()->getDataLayout().getTypeAllocSize(Ty); 398 return SizeInBytes; 399 } 400 /// Check if we want (and can) handle this alloca. 401 bool isInterestingAlloca(AllocaInst &AI); 402 403 // Check if we have dynamic alloca. 404 bool isDynamicAlloca(AllocaInst &AI) const { 405 return AI.isArrayAllocation() || !AI.isStaticAlloca(); 406 } 407 408 /// If it is an interesting memory access, return the PointerOperand 409 /// and set IsWrite/Alignment. Otherwise return nullptr. 410 Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite, 411 uint64_t *TypeSize, unsigned *Alignment); 412 void instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, Instruction *I, 413 bool UseCalls, const DataLayout &DL); 414 void instrumentPointerComparisonOrSubtraction(Instruction *I); 415 void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore, 416 Value *Addr, uint32_t TypeSize, bool IsWrite, 417 Value *SizeArgument, bool UseCalls, uint32_t Exp); 418 void instrumentUnusualSizeOrAlignment(Instruction *I, Value *Addr, 419 uint32_t TypeSize, bool IsWrite, 420 Value *SizeArgument, bool UseCalls, 421 uint32_t Exp); 422 Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong, 423 Value *ShadowValue, uint32_t TypeSize); 424 Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr, 425 bool IsWrite, size_t AccessSizeIndex, 426 Value *SizeArgument, uint32_t Exp); 427 void instrumentMemIntrinsic(MemIntrinsic *MI); 428 Value *memToShadow(Value *Shadow, IRBuilder<> &IRB); 429 bool runOnFunction(Function &F) override; 430 bool maybeInsertAsanInitAtFunctionEntry(Function &F); 431 bool doInitialization(Module &M) override; 432 static char ID; // Pass identification, replacement for typeid 433 434 DominatorTree &getDominatorTree() const { return *DT; } 435 436 private: 437 void initializeCallbacks(Module &M); 438 439 bool LooksLikeCodeInBug11395(Instruction *I); 440 bool GlobalIsLinkerInitialized(GlobalVariable *G); 441 bool isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis, Value *Addr, 442 uint64_t TypeSize) const; 443 444 LLVMContext *C; 445 Triple TargetTriple; 446 int LongSize; 447 Type *IntptrTy; 448 ShadowMapping Mapping; 449 DominatorTree *DT; 450 Function *AsanCtorFunction; 451 Function *AsanInitFunction; 452 Function *AsanHandleNoReturnFunc; 453 Function *AsanPtrCmpFunction, *AsanPtrSubFunction; 454 // This array is indexed by AccessIsWrite, Experiment and log2(AccessSize). 455 Function *AsanErrorCallback[2][2][kNumberOfAccessSizes]; 456 Function *AsanMemoryAccessCallback[2][2][kNumberOfAccessSizes]; 457 // This array is indexed by AccessIsWrite and Experiment. 458 Function *AsanErrorCallbackSized[2][2]; 459 Function *AsanMemoryAccessCallbackSized[2][2]; 460 Function *AsanMemmove, *AsanMemcpy, *AsanMemset; 461 InlineAsm *EmptyAsm; 462 GlobalsMetadata GlobalsMD; 463 DenseMap<AllocaInst *, bool> ProcessedAllocas; 464 465 friend struct FunctionStackPoisoner; 466 }; 467 468 class AddressSanitizerModule : public ModulePass { 469 public: 470 AddressSanitizerModule() : ModulePass(ID) {} 471 bool runOnModule(Module &M) override; 472 static char ID; // Pass identification, replacement for typeid 473 const char *getPassName() const override { return "AddressSanitizerModule"; } 474 475 private: 476 void initializeCallbacks(Module &M); 477 478 bool InstrumentGlobals(IRBuilder<> &IRB, Module &M); 479 bool ShouldInstrumentGlobal(GlobalVariable *G); 480 void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName); 481 void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName); 482 size_t MinRedzoneSizeForGlobal() const { 483 return RedzoneSizeForScale(Mapping.Scale); 484 } 485 486 GlobalsMetadata GlobalsMD; 487 Type *IntptrTy; 488 LLVMContext *C; 489 Triple TargetTriple; 490 ShadowMapping Mapping; 491 Function *AsanPoisonGlobals; 492 Function *AsanUnpoisonGlobals; 493 Function *AsanRegisterGlobals; 494 Function *AsanUnregisterGlobals; 495 }; 496 497 // Stack poisoning does not play well with exception handling. 498 // When an exception is thrown, we essentially bypass the code 499 // that unpoisones the stack. This is why the run-time library has 500 // to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire 501 // stack in the interceptor. This however does not work inside the 502 // actual function which catches the exception. Most likely because the 503 // compiler hoists the load of the shadow value somewhere too high. 504 // This causes asan to report a non-existing bug on 453.povray. 505 // It sounds like an LLVM bug. 506 struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> { 507 Function &F; 508 AddressSanitizer &ASan; 509 DIBuilder DIB; 510 LLVMContext *C; 511 Type *IntptrTy; 512 Type *IntptrPtrTy; 513 ShadowMapping Mapping; 514 515 SmallVector<AllocaInst *, 16> AllocaVec; 516 SmallVector<Instruction *, 8> RetVec; 517 unsigned StackAlignment; 518 519 Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1], 520 *AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1]; 521 Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc; 522 Function *AsanAllocaPoisonFunc, *AsanAllocasUnpoisonFunc; 523 524 // Stores a place and arguments of poisoning/unpoisoning call for alloca. 525 struct AllocaPoisonCall { 526 IntrinsicInst *InsBefore; 527 AllocaInst *AI; 528 uint64_t Size; 529 bool DoPoison; 530 }; 531 SmallVector<AllocaPoisonCall, 8> AllocaPoisonCallVec; 532 533 SmallVector<AllocaInst *, 1> DynamicAllocaVec; 534 SmallVector<IntrinsicInst *, 1> StackRestoreVec; 535 AllocaInst *DynamicAllocaLayout = nullptr; 536 537 // Maps Value to an AllocaInst from which the Value is originated. 538 typedef DenseMap<Value *, AllocaInst *> AllocaForValueMapTy; 539 AllocaForValueMapTy AllocaForValue; 540 541 bool HasNonEmptyInlineAsm; 542 std::unique_ptr<CallInst> EmptyInlineAsm; 543 544 FunctionStackPoisoner(Function &F, AddressSanitizer &ASan) 545 : F(F), 546 ASan(ASan), 547 DIB(*F.getParent(), /*AllowUnresolved*/ false), 548 C(ASan.C), 549 IntptrTy(ASan.IntptrTy), 550 IntptrPtrTy(PointerType::get(IntptrTy, 0)), 551 Mapping(ASan.Mapping), 552 StackAlignment(1 << Mapping.Scale), 553 HasNonEmptyInlineAsm(false), 554 EmptyInlineAsm(CallInst::Create(ASan.EmptyAsm)) {} 555 556 bool runOnFunction() { 557 if (!ClStack) return false; 558 // Collect alloca, ret, lifetime instructions etc. 559 for (BasicBlock *BB : depth_first(&F.getEntryBlock())) visit(*BB); 560 561 if (AllocaVec.empty() && DynamicAllocaVec.empty()) return false; 562 563 initializeCallbacks(*F.getParent()); 564 565 poisonStack(); 566 567 if (ClDebugStack) { 568 DEBUG(dbgs() << F); 569 } 570 return true; 571 } 572 573 // Finds all Alloca instructions and puts 574 // poisoned red zones around all of them. 575 // Then unpoison everything back before the function returns. 576 void poisonStack(); 577 578 void createDynamicAllocasInitStorage(); 579 580 // ----------------------- Visitors. 581 /// \brief Collect all Ret instructions. 582 void visitReturnInst(ReturnInst &RI) { RetVec.push_back(&RI); } 583 584 void unpoisonDynamicAllocasBeforeInst(Instruction *InstBefore, 585 Value *SavedStack) { 586 IRBuilder<> IRB(InstBefore); 587 IRB.CreateCall(AsanAllocasUnpoisonFunc, 588 {IRB.CreateLoad(DynamicAllocaLayout), 589 IRB.CreatePtrToInt(SavedStack, IntptrTy)}); 590 } 591 592 // Unpoison dynamic allocas redzones. 593 void unpoisonDynamicAllocas() { 594 for (auto &Ret : RetVec) 595 unpoisonDynamicAllocasBeforeInst(Ret, DynamicAllocaLayout); 596 597 for (auto &StackRestoreInst : StackRestoreVec) 598 unpoisonDynamicAllocasBeforeInst(StackRestoreInst, 599 StackRestoreInst->getOperand(0)); 600 } 601 602 // Deploy and poison redzones around dynamic alloca call. To do this, we 603 // should replace this call with another one with changed parameters and 604 // replace all its uses with new address, so 605 // addr = alloca type, old_size, align 606 // is replaced by 607 // new_size = (old_size + additional_size) * sizeof(type) 608 // tmp = alloca i8, new_size, max(align, 32) 609 // addr = tmp + 32 (first 32 bytes are for the left redzone). 610 // Additional_size is added to make new memory allocation contain not only 611 // requested memory, but also left, partial and right redzones. 612 void handleDynamicAllocaCall(AllocaInst *AI); 613 614 /// \brief Collect Alloca instructions we want (and can) handle. 615 void visitAllocaInst(AllocaInst &AI) { 616 if (!ASan.isInterestingAlloca(AI)) return; 617 618 StackAlignment = std::max(StackAlignment, AI.getAlignment()); 619 if (ASan.isDynamicAlloca(AI)) 620 DynamicAllocaVec.push_back(&AI); 621 else 622 AllocaVec.push_back(&AI); 623 } 624 625 /// \brief Collect lifetime intrinsic calls to check for use-after-scope 626 /// errors. 627 void visitIntrinsicInst(IntrinsicInst &II) { 628 Intrinsic::ID ID = II.getIntrinsicID(); 629 if (ID == Intrinsic::stackrestore) StackRestoreVec.push_back(&II); 630 if (!ClCheckLifetime) return; 631 if (ID != Intrinsic::lifetime_start && ID != Intrinsic::lifetime_end) 632 return; 633 // Found lifetime intrinsic, add ASan instrumentation if necessary. 634 ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0)); 635 // If size argument is undefined, don't do anything. 636 if (Size->isMinusOne()) return; 637 // Check that size doesn't saturate uint64_t and can 638 // be stored in IntptrTy. 639 const uint64_t SizeValue = Size->getValue().getLimitedValue(); 640 if (SizeValue == ~0ULL || 641 !ConstantInt::isValueValidForType(IntptrTy, SizeValue)) 642 return; 643 // Find alloca instruction that corresponds to llvm.lifetime argument. 644 AllocaInst *AI = findAllocaForValue(II.getArgOperand(1)); 645 if (!AI) return; 646 bool DoPoison = (ID == Intrinsic::lifetime_end); 647 AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison}; 648 AllocaPoisonCallVec.push_back(APC); 649 } 650 651 void visitCallInst(CallInst &CI) { 652 HasNonEmptyInlineAsm |= 653 CI.isInlineAsm() && !CI.isIdenticalTo(EmptyInlineAsm.get()); 654 } 655 656 // ---------------------- Helpers. 657 void initializeCallbacks(Module &M); 658 659 bool doesDominateAllExits(const Instruction *I) const { 660 for (auto Ret : RetVec) { 661 if (!ASan.getDominatorTree().dominates(I, Ret)) return false; 662 } 663 return true; 664 } 665 666 /// Finds alloca where the value comes from. 667 AllocaInst *findAllocaForValue(Value *V); 668 void poisonRedZones(ArrayRef<uint8_t> ShadowBytes, IRBuilder<> &IRB, 669 Value *ShadowBase, bool DoPoison); 670 void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison); 671 672 void SetShadowToStackAfterReturnInlined(IRBuilder<> &IRB, Value *ShadowBase, 673 int Size); 674 Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L, 675 bool Dynamic); 676 PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue, 677 Instruction *ThenTerm, Value *ValueIfFalse); 678 }; 679 680 } // namespace 681 682 char AddressSanitizer::ID = 0; 683 INITIALIZE_PASS_BEGIN( 684 AddressSanitizer, "asan", 685 "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false, 686 false) 687 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 688 INITIALIZE_PASS_END( 689 AddressSanitizer, "asan", 690 "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false, 691 false) 692 FunctionPass *llvm::createAddressSanitizerFunctionPass() { 693 return new AddressSanitizer(); 694 } 695 696 char AddressSanitizerModule::ID = 0; 697 INITIALIZE_PASS( 698 AddressSanitizerModule, "asan-module", 699 "AddressSanitizer: detects use-after-free and out-of-bounds bugs." 700 "ModulePass", 701 false, false) 702 ModulePass *llvm::createAddressSanitizerModulePass() { 703 return new AddressSanitizerModule(); 704 } 705 706 static size_t TypeSizeToSizeIndex(uint32_t TypeSize) { 707 size_t Res = countTrailingZeros(TypeSize / 8); 708 assert(Res < kNumberOfAccessSizes); 709 return Res; 710 } 711 712 // \brief Create a constant for Str so that we can pass it to the run-time lib. 713 static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str, 714 bool AllowMerging) { 715 Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str); 716 // We use private linkage for module-local strings. If they can be merged 717 // with another one, we set the unnamed_addr attribute. 718 GlobalVariable *GV = 719 new GlobalVariable(M, StrConst->getType(), true, 720 GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix); 721 if (AllowMerging) GV->setUnnamedAddr(true); 722 GV->setAlignment(1); // Strings may not be merged w/o setting align 1. 723 return GV; 724 } 725 726 /// \brief Create a global describing a source location. 727 static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M, 728 LocationMetadata MD) { 729 Constant *LocData[] = { 730 createPrivateGlobalForString(M, MD.Filename, true), 731 ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo), 732 ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo), 733 }; 734 auto LocStruct = ConstantStruct::getAnon(LocData); 735 auto GV = new GlobalVariable(M, LocStruct->getType(), true, 736 GlobalValue::PrivateLinkage, LocStruct, 737 kAsanGenPrefix); 738 GV->setUnnamedAddr(true); 739 return GV; 740 } 741 742 static bool GlobalWasGeneratedByAsan(GlobalVariable *G) { 743 return G->getName().find(kAsanGenPrefix) == 0 || 744 G->getName().find(kSanCovGenPrefix) == 0; 745 } 746 747 Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) { 748 // Shadow >> scale 749 Shadow = IRB.CreateLShr(Shadow, Mapping.Scale); 750 if (Mapping.Offset == 0) return Shadow; 751 // (Shadow >> scale) | offset 752 if (Mapping.OrShadowOffset) 753 return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset)); 754 else 755 return IRB.CreateAdd(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset)); 756 } 757 758 // Instrument memset/memmove/memcpy 759 void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) { 760 IRBuilder<> IRB(MI); 761 if (isa<MemTransferInst>(MI)) { 762 IRB.CreateCall( 763 isa<MemMoveInst>(MI) ? AsanMemmove : AsanMemcpy, 764 {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()), 765 IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()), 766 IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)}); 767 } else if (isa<MemSetInst>(MI)) { 768 IRB.CreateCall( 769 AsanMemset, 770 {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()), 771 IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false), 772 IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)}); 773 } 774 MI->eraseFromParent(); 775 } 776 777 /// Check if we want (and can) handle this alloca. 778 bool AddressSanitizer::isInterestingAlloca(AllocaInst &AI) { 779 auto PreviouslySeenAllocaInfo = ProcessedAllocas.find(&AI); 780 781 if (PreviouslySeenAllocaInfo != ProcessedAllocas.end()) 782 return PreviouslySeenAllocaInfo->getSecond(); 783 784 bool IsInteresting = 785 (AI.getAllocatedType()->isSized() && 786 // alloca() may be called with 0 size, ignore it. 787 getAllocaSizeInBytes(&AI) > 0 && 788 // We are only interested in allocas not promotable to registers. 789 // Promotable allocas are common under -O0. 790 (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI) || 791 isDynamicAlloca(AI))); 792 793 ProcessedAllocas[&AI] = IsInteresting; 794 return IsInteresting; 795 } 796 797 /// If I is an interesting memory access, return the PointerOperand 798 /// and set IsWrite/Alignment. Otherwise return nullptr. 799 Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I, 800 bool *IsWrite, 801 uint64_t *TypeSize, 802 unsigned *Alignment) { 803 // Skip memory accesses inserted by another instrumentation. 804 if (I->getMetadata("nosanitize")) return nullptr; 805 806 Value *PtrOperand = nullptr; 807 const DataLayout &DL = I->getModule()->getDataLayout(); 808 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 809 if (!ClInstrumentReads) return nullptr; 810 *IsWrite = false; 811 *TypeSize = DL.getTypeStoreSizeInBits(LI->getType()); 812 *Alignment = LI->getAlignment(); 813 PtrOperand = LI->getPointerOperand(); 814 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 815 if (!ClInstrumentWrites) return nullptr; 816 *IsWrite = true; 817 *TypeSize = DL.getTypeStoreSizeInBits(SI->getValueOperand()->getType()); 818 *Alignment = SI->getAlignment(); 819 PtrOperand = SI->getPointerOperand(); 820 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) { 821 if (!ClInstrumentAtomics) return nullptr; 822 *IsWrite = true; 823 *TypeSize = DL.getTypeStoreSizeInBits(RMW->getValOperand()->getType()); 824 *Alignment = 0; 825 PtrOperand = RMW->getPointerOperand(); 826 } else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) { 827 if (!ClInstrumentAtomics) return nullptr; 828 *IsWrite = true; 829 *TypeSize = DL.getTypeStoreSizeInBits(XCHG->getCompareOperand()->getType()); 830 *Alignment = 0; 831 PtrOperand = XCHG->getPointerOperand(); 832 } 833 834 // Treat memory accesses to promotable allocas as non-interesting since they 835 // will not cause memory violations. This greatly speeds up the instrumented 836 // executable at -O0. 837 if (ClSkipPromotableAllocas) 838 if (auto AI = dyn_cast_or_null<AllocaInst>(PtrOperand)) 839 return isInterestingAlloca(*AI) ? AI : nullptr; 840 841 return PtrOperand; 842 } 843 844 static bool isPointerOperand(Value *V) { 845 return V->getType()->isPointerTy() || isa<PtrToIntInst>(V); 846 } 847 848 // This is a rough heuristic; it may cause both false positives and 849 // false negatives. The proper implementation requires cooperation with 850 // the frontend. 851 static bool isInterestingPointerComparisonOrSubtraction(Instruction *I) { 852 if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) { 853 if (!Cmp->isRelational()) return false; 854 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) { 855 if (BO->getOpcode() != Instruction::Sub) return false; 856 } else { 857 return false; 858 } 859 if (!isPointerOperand(I->getOperand(0)) || 860 !isPointerOperand(I->getOperand(1))) 861 return false; 862 return true; 863 } 864 865 bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) { 866 // If a global variable does not have dynamic initialization we don't 867 // have to instrument it. However, if a global does not have initializer 868 // at all, we assume it has dynamic initializer (in other TU). 869 return G->hasInitializer() && !GlobalsMD.get(G).IsDynInit; 870 } 871 872 void AddressSanitizer::instrumentPointerComparisonOrSubtraction( 873 Instruction *I) { 874 IRBuilder<> IRB(I); 875 Function *F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction; 876 Value *Param[2] = {I->getOperand(0), I->getOperand(1)}; 877 for (int i = 0; i < 2; i++) { 878 if (Param[i]->getType()->isPointerTy()) 879 Param[i] = IRB.CreatePointerCast(Param[i], IntptrTy); 880 } 881 IRB.CreateCall(F, Param); 882 } 883 884 void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, 885 Instruction *I, bool UseCalls, 886 const DataLayout &DL) { 887 bool IsWrite = false; 888 unsigned Alignment = 0; 889 uint64_t TypeSize = 0; 890 Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment); 891 assert(Addr); 892 893 // Optimization experiments. 894 // The experiments can be used to evaluate potential optimizations that remove 895 // instrumentation (assess false negatives). Instead of completely removing 896 // some instrumentation, you set Exp to a non-zero value (mask of optimization 897 // experiments that want to remove instrumentation of this instruction). 898 // If Exp is non-zero, this pass will emit special calls into runtime 899 // (e.g. __asan_report_exp_load1 instead of __asan_report_load1). These calls 900 // make runtime terminate the program in a special way (with a different 901 // exit status). Then you run the new compiler on a buggy corpus, collect 902 // the special terminations (ideally, you don't see them at all -- no false 903 // negatives) and make the decision on the optimization. 904 uint32_t Exp = ClForceExperiment; 905 906 if (ClOpt && ClOptGlobals) { 907 // If initialization order checking is disabled, a simple access to a 908 // dynamically initialized global is always valid. 909 GlobalVariable *G = dyn_cast<GlobalVariable>(GetUnderlyingObject(Addr, DL)); 910 if (G != NULL && (!ClInitializers || GlobalIsLinkerInitialized(G)) && 911 isSafeAccess(ObjSizeVis, Addr, TypeSize)) { 912 NumOptimizedAccessesToGlobalVar++; 913 return; 914 } 915 } 916 917 if (ClOpt && ClOptStack) { 918 // A direct inbounds access to a stack variable is always valid. 919 if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) && 920 isSafeAccess(ObjSizeVis, Addr, TypeSize)) { 921 NumOptimizedAccessesToStackVar++; 922 return; 923 } 924 } 925 926 if (IsWrite) 927 NumInstrumentedWrites++; 928 else 929 NumInstrumentedReads++; 930 931 unsigned Granularity = 1 << Mapping.Scale; 932 // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check 933 // if the data is properly aligned. 934 if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 || 935 TypeSize == 128) && 936 (Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8)) 937 return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls, 938 Exp); 939 instrumentUnusualSizeOrAlignment(I, Addr, TypeSize, IsWrite, nullptr, 940 UseCalls, Exp); 941 } 942 943 Instruction *AddressSanitizer::generateCrashCode(Instruction *InsertBefore, 944 Value *Addr, bool IsWrite, 945 size_t AccessSizeIndex, 946 Value *SizeArgument, 947 uint32_t Exp) { 948 IRBuilder<> IRB(InsertBefore); 949 Value *ExpVal = Exp == 0 ? nullptr : ConstantInt::get(IRB.getInt32Ty(), Exp); 950 CallInst *Call = nullptr; 951 if (SizeArgument) { 952 if (Exp == 0) 953 Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][0], 954 {Addr, SizeArgument}); 955 else 956 Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][1], 957 {Addr, SizeArgument, ExpVal}); 958 } else { 959 if (Exp == 0) 960 Call = 961 IRB.CreateCall(AsanErrorCallback[IsWrite][0][AccessSizeIndex], Addr); 962 else 963 Call = IRB.CreateCall(AsanErrorCallback[IsWrite][1][AccessSizeIndex], 964 {Addr, ExpVal}); 965 } 966 967 // We don't do Call->setDoesNotReturn() because the BB already has 968 // UnreachableInst at the end. 969 // This EmptyAsm is required to avoid callback merge. 970 IRB.CreateCall(EmptyAsm, {}); 971 return Call; 972 } 973 974 Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong, 975 Value *ShadowValue, 976 uint32_t TypeSize) { 977 size_t Granularity = 1 << Mapping.Scale; 978 // Addr & (Granularity - 1) 979 Value *LastAccessedByte = 980 IRB.CreateAnd(AddrLong, ConstantInt::get(IntptrTy, Granularity - 1)); 981 // (Addr & (Granularity - 1)) + size - 1 982 if (TypeSize / 8 > 1) 983 LastAccessedByte = IRB.CreateAdd( 984 LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1)); 985 // (uint8_t) ((Addr & (Granularity-1)) + size - 1) 986 LastAccessedByte = 987 IRB.CreateIntCast(LastAccessedByte, ShadowValue->getType(), false); 988 // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue 989 return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue); 990 } 991 992 void AddressSanitizer::instrumentAddress(Instruction *OrigIns, 993 Instruction *InsertBefore, Value *Addr, 994 uint32_t TypeSize, bool IsWrite, 995 Value *SizeArgument, bool UseCalls, 996 uint32_t Exp) { 997 IRBuilder<> IRB(InsertBefore); 998 Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy); 999 size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize); 1000 1001 if (UseCalls) { 1002 if (Exp == 0) 1003 IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][0][AccessSizeIndex], 1004 AddrLong); 1005 else 1006 IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][1][AccessSizeIndex], 1007 {AddrLong, ConstantInt::get(IRB.getInt32Ty(), Exp)}); 1008 return; 1009 } 1010 1011 Type *ShadowTy = 1012 IntegerType::get(*C, std::max(8U, TypeSize >> Mapping.Scale)); 1013 Type *ShadowPtrTy = PointerType::get(ShadowTy, 0); 1014 Value *ShadowPtr = memToShadow(AddrLong, IRB); 1015 Value *CmpVal = Constant::getNullValue(ShadowTy); 1016 Value *ShadowValue = 1017 IRB.CreateLoad(IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy)); 1018 1019 Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal); 1020 size_t Granularity = 1 << Mapping.Scale; 1021 TerminatorInst *CrashTerm = nullptr; 1022 1023 if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) { 1024 // We use branch weights for the slow path check, to indicate that the slow 1025 // path is rarely taken. This seems to be the case for SPEC benchmarks. 1026 TerminatorInst *CheckTerm = SplitBlockAndInsertIfThen( 1027 Cmp, InsertBefore, false, MDBuilder(*C).createBranchWeights(1, 100000)); 1028 assert(cast<BranchInst>(CheckTerm)->isUnconditional()); 1029 BasicBlock *NextBB = CheckTerm->getSuccessor(0); 1030 IRB.SetInsertPoint(CheckTerm); 1031 Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize); 1032 BasicBlock *CrashBlock = 1033 BasicBlock::Create(*C, "", NextBB->getParent(), NextBB); 1034 CrashTerm = new UnreachableInst(*C, CrashBlock); 1035 BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2); 1036 ReplaceInstWithInst(CheckTerm, NewTerm); 1037 } else { 1038 CrashTerm = SplitBlockAndInsertIfThen(Cmp, InsertBefore, true); 1039 } 1040 1041 Instruction *Crash = generateCrashCode(CrashTerm, AddrLong, IsWrite, 1042 AccessSizeIndex, SizeArgument, Exp); 1043 Crash->setDebugLoc(OrigIns->getDebugLoc()); 1044 } 1045 1046 // Instrument unusual size or unusual alignment. 1047 // We can not do it with a single check, so we do 1-byte check for the first 1048 // and the last bytes. We call __asan_report_*_n(addr, real_size) to be able 1049 // to report the actual access size. 1050 void AddressSanitizer::instrumentUnusualSizeOrAlignment( 1051 Instruction *I, Value *Addr, uint32_t TypeSize, bool IsWrite, 1052 Value *SizeArgument, bool UseCalls, uint32_t Exp) { 1053 IRBuilder<> IRB(I); 1054 Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8); 1055 Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy); 1056 if (UseCalls) { 1057 if (Exp == 0) 1058 IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][0], 1059 {AddrLong, Size}); 1060 else 1061 IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][1], 1062 {AddrLong, Size, ConstantInt::get(IRB.getInt32Ty(), Exp)}); 1063 } else { 1064 Value *LastByte = IRB.CreateIntToPtr( 1065 IRB.CreateAdd(AddrLong, ConstantInt::get(IntptrTy, TypeSize / 8 - 1)), 1066 Addr->getType()); 1067 instrumentAddress(I, I, Addr, 8, IsWrite, Size, false, Exp); 1068 instrumentAddress(I, I, LastByte, 8, IsWrite, Size, false, Exp); 1069 } 1070 } 1071 1072 void AddressSanitizerModule::poisonOneInitializer(Function &GlobalInit, 1073 GlobalValue *ModuleName) { 1074 // Set up the arguments to our poison/unpoison functions. 1075 IRBuilder<> IRB(GlobalInit.begin()->getFirstInsertionPt()); 1076 1077 // Add a call to poison all external globals before the given function starts. 1078 Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy); 1079 IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr); 1080 1081 // Add calls to unpoison all globals before each return instruction. 1082 for (auto &BB : GlobalInit.getBasicBlockList()) 1083 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator())) 1084 CallInst::Create(AsanUnpoisonGlobals, "", RI); 1085 } 1086 1087 void AddressSanitizerModule::createInitializerPoisonCalls( 1088 Module &M, GlobalValue *ModuleName) { 1089 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors"); 1090 1091 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 1092 for (Use &OP : CA->operands()) { 1093 if (isa<ConstantAggregateZero>(OP)) continue; 1094 ConstantStruct *CS = cast<ConstantStruct>(OP); 1095 1096 // Must have a function or null ptr. 1097 if (Function *F = dyn_cast<Function>(CS->getOperand(1))) { 1098 if (F->getName() == kAsanModuleCtorName) continue; 1099 ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0)); 1100 // Don't instrument CTORs that will run before asan.module_ctor. 1101 if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue; 1102 poisonOneInitializer(*F, ModuleName); 1103 } 1104 } 1105 } 1106 1107 bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) { 1108 Type *Ty = cast<PointerType>(G->getType())->getElementType(); 1109 DEBUG(dbgs() << "GLOBAL: " << *G << "\n"); 1110 1111 if (GlobalsMD.get(G).IsBlacklisted) return false; 1112 if (!Ty->isSized()) return false; 1113 if (!G->hasInitializer()) return false; 1114 if (GlobalWasGeneratedByAsan(G)) return false; // Our own global. 1115 // Touch only those globals that will not be defined in other modules. 1116 // Don't handle ODR linkage types and COMDATs since other modules may be built 1117 // without ASan. 1118 if (G->getLinkage() != GlobalVariable::ExternalLinkage && 1119 G->getLinkage() != GlobalVariable::PrivateLinkage && 1120 G->getLinkage() != GlobalVariable::InternalLinkage) 1121 return false; 1122 if (G->hasComdat()) return false; 1123 // Two problems with thread-locals: 1124 // - The address of the main thread's copy can't be computed at link-time. 1125 // - Need to poison all copies, not just the main thread's one. 1126 if (G->isThreadLocal()) return false; 1127 // For now, just ignore this Global if the alignment is large. 1128 if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false; 1129 1130 if (G->hasSection()) { 1131 StringRef Section(G->getSection()); 1132 1133 // Globals from llvm.metadata aren't emitted, do not instrument them. 1134 if (Section == "llvm.metadata") return false; 1135 1136 // Callbacks put into the CRT initializer/terminator sections 1137 // should not be instrumented. 1138 // See https://code.google.com/p/address-sanitizer/issues/detail?id=305 1139 // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx 1140 if (Section.startswith(".CRT")) { 1141 DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n"); 1142 return false; 1143 } 1144 1145 if (TargetTriple.isOSBinFormatMachO()) { 1146 StringRef ParsedSegment, ParsedSection; 1147 unsigned TAA = 0, StubSize = 0; 1148 bool TAAParsed; 1149 std::string ErrorCode = MCSectionMachO::ParseSectionSpecifier( 1150 Section, ParsedSegment, ParsedSection, TAA, TAAParsed, StubSize); 1151 if (!ErrorCode.empty()) { 1152 assert(false && "Invalid section specifier."); 1153 return false; 1154 } 1155 1156 // Ignore the globals from the __OBJC section. The ObjC runtime assumes 1157 // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to 1158 // them. 1159 if (ParsedSegment == "__OBJC" || 1160 (ParsedSegment == "__DATA" && ParsedSection.startswith("__objc_"))) { 1161 DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n"); 1162 return false; 1163 } 1164 // See http://code.google.com/p/address-sanitizer/issues/detail?id=32 1165 // Constant CFString instances are compiled in the following way: 1166 // -- the string buffer is emitted into 1167 // __TEXT,__cstring,cstring_literals 1168 // -- the constant NSConstantString structure referencing that buffer 1169 // is placed into __DATA,__cfstring 1170 // Therefore there's no point in placing redzones into __DATA,__cfstring. 1171 // Moreover, it causes the linker to crash on OS X 10.7 1172 if (ParsedSegment == "__DATA" && ParsedSection == "__cfstring") { 1173 DEBUG(dbgs() << "Ignoring CFString: " << *G << "\n"); 1174 return false; 1175 } 1176 // The linker merges the contents of cstring_literals and removes the 1177 // trailing zeroes. 1178 if (ParsedSegment == "__TEXT" && (TAA & MachO::S_CSTRING_LITERALS)) { 1179 DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n"); 1180 return false; 1181 } 1182 } 1183 } 1184 1185 return true; 1186 } 1187 1188 void AddressSanitizerModule::initializeCallbacks(Module &M) { 1189 IRBuilder<> IRB(*C); 1190 // Declare our poisoning and unpoisoning functions. 1191 AsanPoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1192 kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr)); 1193 AsanPoisonGlobals->setLinkage(Function::ExternalLinkage); 1194 AsanUnpoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1195 kAsanUnpoisonGlobalsName, IRB.getVoidTy(), nullptr)); 1196 AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage); 1197 // Declare functions that register/unregister globals. 1198 AsanRegisterGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1199 kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr)); 1200 AsanRegisterGlobals->setLinkage(Function::ExternalLinkage); 1201 AsanUnregisterGlobals = checkSanitizerInterfaceFunction( 1202 M.getOrInsertFunction(kAsanUnregisterGlobalsName, IRB.getVoidTy(), 1203 IntptrTy, IntptrTy, nullptr)); 1204 AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage); 1205 } 1206 1207 // This function replaces all global variables with new variables that have 1208 // trailing redzones. It also creates a function that poisons 1209 // redzones and inserts this function into llvm.global_ctors. 1210 bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) { 1211 GlobalsMD.init(M); 1212 1213 SmallVector<GlobalVariable *, 16> GlobalsToChange; 1214 1215 for (auto &G : M.globals()) { 1216 if (ShouldInstrumentGlobal(&G)) GlobalsToChange.push_back(&G); 1217 } 1218 1219 size_t n = GlobalsToChange.size(); 1220 if (n == 0) return false; 1221 1222 // A global is described by a structure 1223 // size_t beg; 1224 // size_t size; 1225 // size_t size_with_redzone; 1226 // const char *name; 1227 // const char *module_name; 1228 // size_t has_dynamic_init; 1229 // void *source_location; 1230 // We initialize an array of such structures and pass it to a run-time call. 1231 StructType *GlobalStructTy = 1232 StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy, 1233 IntptrTy, IntptrTy, nullptr); 1234 SmallVector<Constant *, 16> Initializers(n); 1235 1236 bool HasDynamicallyInitializedGlobals = false; 1237 1238 // We shouldn't merge same module names, as this string serves as unique 1239 // module ID in runtime. 1240 GlobalVariable *ModuleName = createPrivateGlobalForString( 1241 M, M.getModuleIdentifier(), /*AllowMerging*/ false); 1242 1243 auto &DL = M.getDataLayout(); 1244 for (size_t i = 0; i < n; i++) { 1245 static const uint64_t kMaxGlobalRedzone = 1 << 18; 1246 GlobalVariable *G = GlobalsToChange[i]; 1247 1248 auto MD = GlobalsMD.get(G); 1249 // Create string holding the global name (use global name from metadata 1250 // if it's available, otherwise just write the name of global variable). 1251 GlobalVariable *Name = createPrivateGlobalForString( 1252 M, MD.Name.empty() ? G->getName() : MD.Name, 1253 /*AllowMerging*/ true); 1254 1255 PointerType *PtrTy = cast<PointerType>(G->getType()); 1256 Type *Ty = PtrTy->getElementType(); 1257 uint64_t SizeInBytes = DL.getTypeAllocSize(Ty); 1258 uint64_t MinRZ = MinRedzoneSizeForGlobal(); 1259 // MinRZ <= RZ <= kMaxGlobalRedzone 1260 // and trying to make RZ to be ~ 1/4 of SizeInBytes. 1261 uint64_t RZ = std::max( 1262 MinRZ, std::min(kMaxGlobalRedzone, (SizeInBytes / MinRZ / 4) * MinRZ)); 1263 uint64_t RightRedzoneSize = RZ; 1264 // Round up to MinRZ 1265 if (SizeInBytes % MinRZ) RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ); 1266 assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0); 1267 Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize); 1268 1269 StructType *NewTy = StructType::get(Ty, RightRedZoneTy, nullptr); 1270 Constant *NewInitializer = 1271 ConstantStruct::get(NewTy, G->getInitializer(), 1272 Constant::getNullValue(RightRedZoneTy), nullptr); 1273 1274 // Create a new global variable with enough space for a redzone. 1275 GlobalValue::LinkageTypes Linkage = G->getLinkage(); 1276 if (G->isConstant() && Linkage == GlobalValue::PrivateLinkage) 1277 Linkage = GlobalValue::InternalLinkage; 1278 GlobalVariable *NewGlobal = 1279 new GlobalVariable(M, NewTy, G->isConstant(), Linkage, NewInitializer, 1280 "", G, G->getThreadLocalMode()); 1281 NewGlobal->copyAttributesFrom(G); 1282 NewGlobal->setAlignment(MinRZ); 1283 1284 Value *Indices2[2]; 1285 Indices2[0] = IRB.getInt32(0); 1286 Indices2[1] = IRB.getInt32(0); 1287 1288 G->replaceAllUsesWith( 1289 ConstantExpr::getGetElementPtr(NewTy, NewGlobal, Indices2, true)); 1290 NewGlobal->takeName(G); 1291 G->eraseFromParent(); 1292 1293 Constant *SourceLoc; 1294 if (!MD.SourceLoc.empty()) { 1295 auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc); 1296 SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy); 1297 } else { 1298 SourceLoc = ConstantInt::get(IntptrTy, 0); 1299 } 1300 1301 Initializers[i] = ConstantStruct::get( 1302 GlobalStructTy, ConstantExpr::getPointerCast(NewGlobal, IntptrTy), 1303 ConstantInt::get(IntptrTy, SizeInBytes), 1304 ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize), 1305 ConstantExpr::getPointerCast(Name, IntptrTy), 1306 ConstantExpr::getPointerCast(ModuleName, IntptrTy), 1307 ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc, nullptr); 1308 1309 if (ClInitializers && MD.IsDynInit) HasDynamicallyInitializedGlobals = true; 1310 1311 DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n"); 1312 } 1313 1314 ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n); 1315 GlobalVariable *AllGlobals = new GlobalVariable( 1316 M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage, 1317 ConstantArray::get(ArrayOfGlobalStructTy, Initializers), ""); 1318 1319 // Create calls for poisoning before initializers run and unpoisoning after. 1320 if (HasDynamicallyInitializedGlobals) 1321 createInitializerPoisonCalls(M, ModuleName); 1322 IRB.CreateCall(AsanRegisterGlobals, 1323 {IRB.CreatePointerCast(AllGlobals, IntptrTy), 1324 ConstantInt::get(IntptrTy, n)}); 1325 1326 // We also need to unregister globals at the end, e.g. when a shared library 1327 // gets closed. 1328 Function *AsanDtorFunction = 1329 Function::Create(FunctionType::get(Type::getVoidTy(*C), false), 1330 GlobalValue::InternalLinkage, kAsanModuleDtorName, &M); 1331 BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction); 1332 IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB)); 1333 IRB_Dtor.CreateCall(AsanUnregisterGlobals, 1334 {IRB.CreatePointerCast(AllGlobals, IntptrTy), 1335 ConstantInt::get(IntptrTy, n)}); 1336 appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority); 1337 1338 DEBUG(dbgs() << M); 1339 return true; 1340 } 1341 1342 bool AddressSanitizerModule::runOnModule(Module &M) { 1343 C = &(M.getContext()); 1344 int LongSize = M.getDataLayout().getPointerSizeInBits(); 1345 IntptrTy = Type::getIntNTy(*C, LongSize); 1346 TargetTriple = Triple(M.getTargetTriple()); 1347 Mapping = getShadowMapping(TargetTriple, LongSize); 1348 initializeCallbacks(M); 1349 1350 bool Changed = false; 1351 1352 Function *CtorFunc = M.getFunction(kAsanModuleCtorName); 1353 assert(CtorFunc); 1354 IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator()); 1355 1356 if (ClGlobals) Changed |= InstrumentGlobals(IRB, M); 1357 1358 return Changed; 1359 } 1360 1361 void AddressSanitizer::initializeCallbacks(Module &M) { 1362 IRBuilder<> IRB(*C); 1363 // Create __asan_report* callbacks. 1364 // IsWrite, TypeSize and Exp are encoded in the function name. 1365 for (int Exp = 0; Exp < 2; Exp++) { 1366 for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) { 1367 const std::string TypeStr = AccessIsWrite ? "store" : "load"; 1368 const std::string ExpStr = Exp ? "exp_" : ""; 1369 const Type *ExpType = Exp ? Type::getInt32Ty(*C) : nullptr; 1370 AsanErrorCallbackSized[AccessIsWrite][Exp] = 1371 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1372 kAsanReportErrorTemplate + ExpStr + TypeStr + "_n", 1373 IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr)); 1374 AsanMemoryAccessCallbackSized[AccessIsWrite][Exp] = 1375 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1376 ClMemoryAccessCallbackPrefix + ExpStr + TypeStr + "N", 1377 IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr)); 1378 for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes; 1379 AccessSizeIndex++) { 1380 const std::string Suffix = TypeStr + itostr(1 << AccessSizeIndex); 1381 AsanErrorCallback[AccessIsWrite][Exp][AccessSizeIndex] = 1382 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1383 kAsanReportErrorTemplate + ExpStr + Suffix, IRB.getVoidTy(), 1384 IntptrTy, ExpType, nullptr)); 1385 AsanMemoryAccessCallback[AccessIsWrite][Exp][AccessSizeIndex] = 1386 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1387 ClMemoryAccessCallbackPrefix + ExpStr + Suffix, IRB.getVoidTy(), 1388 IntptrTy, ExpType, nullptr)); 1389 } 1390 } 1391 } 1392 1393 AsanMemmove = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1394 ClMemoryAccessCallbackPrefix + "memmove", IRB.getInt8PtrTy(), 1395 IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr)); 1396 AsanMemcpy = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1397 ClMemoryAccessCallbackPrefix + "memcpy", IRB.getInt8PtrTy(), 1398 IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr)); 1399 AsanMemset = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1400 ClMemoryAccessCallbackPrefix + "memset", IRB.getInt8PtrTy(), 1401 IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy, nullptr)); 1402 1403 AsanHandleNoReturnFunc = checkSanitizerInterfaceFunction( 1404 M.getOrInsertFunction(kAsanHandleNoReturnName, IRB.getVoidTy(), nullptr)); 1405 1406 AsanPtrCmpFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1407 kAsanPtrCmp, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr)); 1408 AsanPtrSubFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1409 kAsanPtrSub, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr)); 1410 // We insert an empty inline asm after __asan_report* to avoid callback merge. 1411 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false), 1412 StringRef(""), StringRef(""), 1413 /*hasSideEffects=*/true); 1414 } 1415 1416 // virtual 1417 bool AddressSanitizer::doInitialization(Module &M) { 1418 // Initialize the private fields. No one has accessed them before. 1419 1420 GlobalsMD.init(M); 1421 1422 C = &(M.getContext()); 1423 LongSize = M.getDataLayout().getPointerSizeInBits(); 1424 IntptrTy = Type::getIntNTy(*C, LongSize); 1425 TargetTriple = Triple(M.getTargetTriple()); 1426 1427 std::tie(AsanCtorFunction, AsanInitFunction) = 1428 createSanitizerCtorAndInitFunctions(M, kAsanModuleCtorName, kAsanInitName, 1429 /*InitArgTypes=*/{}, 1430 /*InitArgs=*/{}); 1431 1432 Mapping = getShadowMapping(TargetTriple, LongSize); 1433 1434 appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority); 1435 return true; 1436 } 1437 1438 bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) { 1439 // For each NSObject descendant having a +load method, this method is invoked 1440 // by the ObjC runtime before any of the static constructors is called. 1441 // Therefore we need to instrument such methods with a call to __asan_init 1442 // at the beginning in order to initialize our runtime before any access to 1443 // the shadow memory. 1444 // We cannot just ignore these methods, because they may call other 1445 // instrumented functions. 1446 if (F.getName().find(" load]") != std::string::npos) { 1447 IRBuilder<> IRB(F.begin()->begin()); 1448 IRB.CreateCall(AsanInitFunction, {}); 1449 return true; 1450 } 1451 return false; 1452 } 1453 1454 bool AddressSanitizer::runOnFunction(Function &F) { 1455 if (&F == AsanCtorFunction) return false; 1456 if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false; 1457 DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n"); 1458 initializeCallbacks(*F.getParent()); 1459 1460 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 1461 1462 // If needed, insert __asan_init before checking for SanitizeAddress attr. 1463 maybeInsertAsanInitAtFunctionEntry(F); 1464 1465 if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return false; 1466 1467 if (!ClDebugFunc.empty() && ClDebugFunc != F.getName()) return false; 1468 1469 // We want to instrument every address only once per basic block (unless there 1470 // are calls between uses). 1471 SmallSet<Value *, 16> TempsToInstrument; 1472 SmallVector<Instruction *, 16> ToInstrument; 1473 SmallVector<Instruction *, 8> NoReturnCalls; 1474 SmallVector<BasicBlock *, 16> AllBlocks; 1475 SmallVector<Instruction *, 16> PointerComparisonsOrSubtracts; 1476 int NumAllocas = 0; 1477 bool IsWrite; 1478 unsigned Alignment; 1479 uint64_t TypeSize; 1480 1481 // Fill the set of memory operations to instrument. 1482 for (auto &BB : F) { 1483 AllBlocks.push_back(&BB); 1484 TempsToInstrument.clear(); 1485 int NumInsnsPerBB = 0; 1486 for (auto &Inst : BB) { 1487 if (LooksLikeCodeInBug11395(&Inst)) return false; 1488 if (Value *Addr = isInterestingMemoryAccess(&Inst, &IsWrite, &TypeSize, 1489 &Alignment)) { 1490 if (ClOpt && ClOptSameTemp) { 1491 if (!TempsToInstrument.insert(Addr).second) 1492 continue; // We've seen this temp in the current BB. 1493 } 1494 } else if (ClInvalidPointerPairs && 1495 isInterestingPointerComparisonOrSubtraction(&Inst)) { 1496 PointerComparisonsOrSubtracts.push_back(&Inst); 1497 continue; 1498 } else if (isa<MemIntrinsic>(Inst)) { 1499 // ok, take it. 1500 } else { 1501 if (isa<AllocaInst>(Inst)) NumAllocas++; 1502 CallSite CS(&Inst); 1503 if (CS) { 1504 // A call inside BB. 1505 TempsToInstrument.clear(); 1506 if (CS.doesNotReturn()) NoReturnCalls.push_back(CS.getInstruction()); 1507 } 1508 continue; 1509 } 1510 ToInstrument.push_back(&Inst); 1511 NumInsnsPerBB++; 1512 if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB) break; 1513 } 1514 } 1515 1516 bool UseCalls = false; 1517 if (ClInstrumentationWithCallsThreshold >= 0 && 1518 ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold) 1519 UseCalls = true; 1520 1521 const TargetLibraryInfo *TLI = 1522 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); 1523 const DataLayout &DL = F.getParent()->getDataLayout(); 1524 ObjectSizeOffsetVisitor ObjSizeVis(DL, TLI, F.getContext(), 1525 /*RoundToAlign=*/true); 1526 1527 // Instrument. 1528 int NumInstrumented = 0; 1529 for (auto Inst : ToInstrument) { 1530 if (ClDebugMin < 0 || ClDebugMax < 0 || 1531 (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) { 1532 if (isInterestingMemoryAccess(Inst, &IsWrite, &TypeSize, &Alignment)) 1533 instrumentMop(ObjSizeVis, Inst, UseCalls, 1534 F.getParent()->getDataLayout()); 1535 else 1536 instrumentMemIntrinsic(cast<MemIntrinsic>(Inst)); 1537 } 1538 NumInstrumented++; 1539 } 1540 1541 FunctionStackPoisoner FSP(F, *this); 1542 bool ChangedStack = FSP.runOnFunction(); 1543 1544 // We must unpoison the stack before every NoReturn call (throw, _exit, etc). 1545 // See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37 1546 for (auto CI : NoReturnCalls) { 1547 IRBuilder<> IRB(CI); 1548 IRB.CreateCall(AsanHandleNoReturnFunc, {}); 1549 } 1550 1551 for (auto Inst : PointerComparisonsOrSubtracts) { 1552 instrumentPointerComparisonOrSubtraction(Inst); 1553 NumInstrumented++; 1554 } 1555 1556 bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty(); 1557 1558 DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n"); 1559 1560 return res; 1561 } 1562 1563 // Workaround for bug 11395: we don't want to instrument stack in functions 1564 // with large assembly blobs (32-bit only), otherwise reg alloc may crash. 1565 // FIXME: remove once the bug 11395 is fixed. 1566 bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) { 1567 if (LongSize != 32) return false; 1568 CallInst *CI = dyn_cast<CallInst>(I); 1569 if (!CI || !CI->isInlineAsm()) return false; 1570 if (CI->getNumArgOperands() <= 5) return false; 1571 // We have inline assembly with quite a few arguments. 1572 return true; 1573 } 1574 1575 void FunctionStackPoisoner::initializeCallbacks(Module &M) { 1576 IRBuilder<> IRB(*C); 1577 for (int i = 0; i <= kMaxAsanStackMallocSizeClass; i++) { 1578 std::string Suffix = itostr(i); 1579 AsanStackMallocFunc[i] = checkSanitizerInterfaceFunction( 1580 M.getOrInsertFunction(kAsanStackMallocNameTemplate + Suffix, IntptrTy, 1581 IntptrTy, nullptr)); 1582 AsanStackFreeFunc[i] = checkSanitizerInterfaceFunction( 1583 M.getOrInsertFunction(kAsanStackFreeNameTemplate + Suffix, 1584 IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr)); 1585 } 1586 AsanPoisonStackMemoryFunc = checkSanitizerInterfaceFunction( 1587 M.getOrInsertFunction(kAsanPoisonStackMemoryName, IRB.getVoidTy(), 1588 IntptrTy, IntptrTy, nullptr)); 1589 AsanUnpoisonStackMemoryFunc = checkSanitizerInterfaceFunction( 1590 M.getOrInsertFunction(kAsanUnpoisonStackMemoryName, IRB.getVoidTy(), 1591 IntptrTy, IntptrTy, nullptr)); 1592 AsanAllocaPoisonFunc = checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1593 kAsanAllocaPoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr)); 1594 AsanAllocasUnpoisonFunc = 1595 checkSanitizerInterfaceFunction(M.getOrInsertFunction( 1596 kAsanAllocasUnpoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr)); 1597 } 1598 1599 void FunctionStackPoisoner::poisonRedZones(ArrayRef<uint8_t> ShadowBytes, 1600 IRBuilder<> &IRB, Value *ShadowBase, 1601 bool DoPoison) { 1602 size_t n = ShadowBytes.size(); 1603 size_t i = 0; 1604 // We need to (un)poison n bytes of stack shadow. Poison as many as we can 1605 // using 64-bit stores (if we are on 64-bit arch), then poison the rest 1606 // with 32-bit stores, then with 16-byte stores, then with 8-byte stores. 1607 for (size_t LargeStoreSizeInBytes = ASan.LongSize / 8; 1608 LargeStoreSizeInBytes != 0; LargeStoreSizeInBytes /= 2) { 1609 for (; i + LargeStoreSizeInBytes - 1 < n; i += LargeStoreSizeInBytes) { 1610 uint64_t Val = 0; 1611 for (size_t j = 0; j < LargeStoreSizeInBytes; j++) { 1612 if (F.getParent()->getDataLayout().isLittleEndian()) 1613 Val |= (uint64_t)ShadowBytes[i + j] << (8 * j); 1614 else 1615 Val = (Val << 8) | ShadowBytes[i + j]; 1616 } 1617 if (!Val) continue; 1618 Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i)); 1619 Type *StoreTy = Type::getIntNTy(*C, LargeStoreSizeInBytes * 8); 1620 Value *Poison = ConstantInt::get(StoreTy, DoPoison ? Val : 0); 1621 IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, StoreTy->getPointerTo())); 1622 } 1623 } 1624 } 1625 1626 // Fake stack allocator (asan_fake_stack.h) has 11 size classes 1627 // for every power of 2 from kMinStackMallocSize to kMaxAsanStackMallocSizeClass 1628 static int StackMallocSizeClass(uint64_t LocalStackSize) { 1629 assert(LocalStackSize <= kMaxStackMallocSize); 1630 uint64_t MaxSize = kMinStackMallocSize; 1631 for (int i = 0;; i++, MaxSize *= 2) 1632 if (LocalStackSize <= MaxSize) return i; 1633 llvm_unreachable("impossible LocalStackSize"); 1634 } 1635 1636 // Set Size bytes starting from ShadowBase to kAsanStackAfterReturnMagic. 1637 // We can not use MemSet intrinsic because it may end up calling the actual 1638 // memset. Size is a multiple of 8. 1639 // Currently this generates 8-byte stores on x86_64; it may be better to 1640 // generate wider stores. 1641 void FunctionStackPoisoner::SetShadowToStackAfterReturnInlined( 1642 IRBuilder<> &IRB, Value *ShadowBase, int Size) { 1643 assert(!(Size % 8)); 1644 1645 // kAsanStackAfterReturnMagic is 0xf5. 1646 const uint64_t kAsanStackAfterReturnMagic64 = 0xf5f5f5f5f5f5f5f5ULL; 1647 1648 for (int i = 0; i < Size; i += 8) { 1649 Value *p = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i)); 1650 IRB.CreateStore( 1651 ConstantInt::get(IRB.getInt64Ty(), kAsanStackAfterReturnMagic64), 1652 IRB.CreateIntToPtr(p, IRB.getInt64Ty()->getPointerTo())); 1653 } 1654 } 1655 1656 static DebugLoc getFunctionEntryDebugLocation(Function &F) { 1657 for (const auto &Inst : F.getEntryBlock()) 1658 if (!isa<AllocaInst>(Inst)) return Inst.getDebugLoc(); 1659 return DebugLoc(); 1660 } 1661 1662 PHINode *FunctionStackPoisoner::createPHI(IRBuilder<> &IRB, Value *Cond, 1663 Value *ValueIfTrue, 1664 Instruction *ThenTerm, 1665 Value *ValueIfFalse) { 1666 PHINode *PHI = IRB.CreatePHI(IntptrTy, 2); 1667 BasicBlock *CondBlock = cast<Instruction>(Cond)->getParent(); 1668 PHI->addIncoming(ValueIfFalse, CondBlock); 1669 BasicBlock *ThenBlock = ThenTerm->getParent(); 1670 PHI->addIncoming(ValueIfTrue, ThenBlock); 1671 return PHI; 1672 } 1673 1674 Value *FunctionStackPoisoner::createAllocaForLayout( 1675 IRBuilder<> &IRB, const ASanStackFrameLayout &L, bool Dynamic) { 1676 AllocaInst *Alloca; 1677 if (Dynamic) { 1678 Alloca = IRB.CreateAlloca(IRB.getInt8Ty(), 1679 ConstantInt::get(IRB.getInt64Ty(), L.FrameSize), 1680 "MyAlloca"); 1681 } else { 1682 Alloca = IRB.CreateAlloca(ArrayType::get(IRB.getInt8Ty(), L.FrameSize), 1683 nullptr, "MyAlloca"); 1684 assert(Alloca->isStaticAlloca()); 1685 } 1686 assert((ClRealignStack & (ClRealignStack - 1)) == 0); 1687 size_t FrameAlignment = std::max(L.FrameAlignment, (size_t)ClRealignStack); 1688 Alloca->setAlignment(FrameAlignment); 1689 return IRB.CreatePointerCast(Alloca, IntptrTy); 1690 } 1691 1692 void FunctionStackPoisoner::createDynamicAllocasInitStorage() { 1693 BasicBlock &FirstBB = *F.begin(); 1694 IRBuilder<> IRB(dyn_cast<Instruction>(FirstBB.begin())); 1695 DynamicAllocaLayout = IRB.CreateAlloca(IntptrTy, nullptr); 1696 IRB.CreateStore(Constant::getNullValue(IntptrTy), DynamicAllocaLayout); 1697 DynamicAllocaLayout->setAlignment(32); 1698 } 1699 1700 void FunctionStackPoisoner::poisonStack() { 1701 assert(AllocaVec.size() > 0 || DynamicAllocaVec.size() > 0); 1702 1703 if (ClInstrumentAllocas && DynamicAllocaVec.size() > 0) { 1704 // Handle dynamic allocas. 1705 createDynamicAllocasInitStorage(); 1706 for (auto &AI : DynamicAllocaVec) handleDynamicAllocaCall(AI); 1707 1708 unpoisonDynamicAllocas(); 1709 } 1710 1711 if (AllocaVec.size() == 0) return; 1712 1713 int StackMallocIdx = -1; 1714 DebugLoc EntryDebugLocation = getFunctionEntryDebugLocation(F); 1715 1716 Instruction *InsBefore = AllocaVec[0]; 1717 IRBuilder<> IRB(InsBefore); 1718 IRB.SetCurrentDebugLocation(EntryDebugLocation); 1719 1720 SmallVector<ASanStackVariableDescription, 16> SVD; 1721 SVD.reserve(AllocaVec.size()); 1722 for (AllocaInst *AI : AllocaVec) { 1723 ASanStackVariableDescription D = {AI->getName().data(), 1724 ASan.getAllocaSizeInBytes(AI), 1725 AI->getAlignment(), AI, 0}; 1726 SVD.push_back(D); 1727 } 1728 // Minimal header size (left redzone) is 4 pointers, 1729 // i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms. 1730 size_t MinHeaderSize = ASan.LongSize / 2; 1731 ASanStackFrameLayout L; 1732 ComputeASanStackFrameLayout(SVD, 1UL << Mapping.Scale, MinHeaderSize, &L); 1733 DEBUG(dbgs() << L.DescriptionString << " --- " << L.FrameSize << "\n"); 1734 uint64_t LocalStackSize = L.FrameSize; 1735 bool DoStackMalloc = 1736 ClUseAfterReturn && LocalStackSize <= kMaxStackMallocSize; 1737 // Don't do dynamic alloca in presence of inline asm: too often it makes 1738 // assumptions on which registers are available. Don't do stack malloc in the 1739 // presence of inline asm on 32-bit platforms for the same reason. 1740 bool DoDynamicAlloca = ClDynamicAllocaStack && !HasNonEmptyInlineAsm; 1741 DoStackMalloc &= !HasNonEmptyInlineAsm || ASan.LongSize != 32; 1742 1743 Value *StaticAlloca = 1744 DoDynamicAlloca ? nullptr : createAllocaForLayout(IRB, L, false); 1745 1746 Value *FakeStack; 1747 Value *LocalStackBase; 1748 1749 if (DoStackMalloc) { 1750 // void *FakeStack = __asan_option_detect_stack_use_after_return 1751 // ? __asan_stack_malloc_N(LocalStackSize) 1752 // : nullptr; 1753 // void *LocalStackBase = (FakeStack) ? FakeStack : alloca(LocalStackSize); 1754 Constant *OptionDetectUAR = F.getParent()->getOrInsertGlobal( 1755 kAsanOptionDetectUAR, IRB.getInt32Ty()); 1756 Value *UARIsEnabled = 1757 IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUAR), 1758 Constant::getNullValue(IRB.getInt32Ty())); 1759 Instruction *Term = 1760 SplitBlockAndInsertIfThen(UARIsEnabled, InsBefore, false); 1761 IRBuilder<> IRBIf(Term); 1762 IRBIf.SetCurrentDebugLocation(EntryDebugLocation); 1763 StackMallocIdx = StackMallocSizeClass(LocalStackSize); 1764 assert(StackMallocIdx <= kMaxAsanStackMallocSizeClass); 1765 Value *FakeStackValue = 1766 IRBIf.CreateCall(AsanStackMallocFunc[StackMallocIdx], 1767 ConstantInt::get(IntptrTy, LocalStackSize)); 1768 IRB.SetInsertPoint(InsBefore); 1769 IRB.SetCurrentDebugLocation(EntryDebugLocation); 1770 FakeStack = createPHI(IRB, UARIsEnabled, FakeStackValue, Term, 1771 ConstantInt::get(IntptrTy, 0)); 1772 1773 Value *NoFakeStack = 1774 IRB.CreateICmpEQ(FakeStack, Constant::getNullValue(IntptrTy)); 1775 Term = SplitBlockAndInsertIfThen(NoFakeStack, InsBefore, false); 1776 IRBIf.SetInsertPoint(Term); 1777 IRBIf.SetCurrentDebugLocation(EntryDebugLocation); 1778 Value *AllocaValue = 1779 DoDynamicAlloca ? createAllocaForLayout(IRBIf, L, true) : StaticAlloca; 1780 IRB.SetInsertPoint(InsBefore); 1781 IRB.SetCurrentDebugLocation(EntryDebugLocation); 1782 LocalStackBase = createPHI(IRB, NoFakeStack, AllocaValue, Term, FakeStack); 1783 } else { 1784 // void *FakeStack = nullptr; 1785 // void *LocalStackBase = alloca(LocalStackSize); 1786 FakeStack = ConstantInt::get(IntptrTy, 0); 1787 LocalStackBase = 1788 DoDynamicAlloca ? createAllocaForLayout(IRB, L, true) : StaticAlloca; 1789 } 1790 1791 // Insert poison calls for lifetime intrinsics for alloca. 1792 bool HavePoisonedAllocas = false; 1793 for (const auto &APC : AllocaPoisonCallVec) { 1794 assert(APC.InsBefore); 1795 assert(APC.AI); 1796 IRBuilder<> IRB(APC.InsBefore); 1797 poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison); 1798 HavePoisonedAllocas |= APC.DoPoison; 1799 } 1800 1801 // Replace Alloca instructions with base+offset. 1802 for (const auto &Desc : SVD) { 1803 AllocaInst *AI = Desc.AI; 1804 Value *NewAllocaPtr = IRB.CreateIntToPtr( 1805 IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Desc.Offset)), 1806 AI->getType()); 1807 replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB, /*Deref=*/true); 1808 AI->replaceAllUsesWith(NewAllocaPtr); 1809 } 1810 1811 // The left-most redzone has enough space for at least 4 pointers. 1812 // Write the Magic value to redzone[0]. 1813 Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy); 1814 IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic), 1815 BasePlus0); 1816 // Write the frame description constant to redzone[1]. 1817 Value *BasePlus1 = IRB.CreateIntToPtr( 1818 IRB.CreateAdd(LocalStackBase, 1819 ConstantInt::get(IntptrTy, ASan.LongSize / 8)), 1820 IntptrPtrTy); 1821 GlobalVariable *StackDescriptionGlobal = 1822 createPrivateGlobalForString(*F.getParent(), L.DescriptionString, 1823 /*AllowMerging*/ true); 1824 Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal, IntptrTy); 1825 IRB.CreateStore(Description, BasePlus1); 1826 // Write the PC to redzone[2]. 1827 Value *BasePlus2 = IRB.CreateIntToPtr( 1828 IRB.CreateAdd(LocalStackBase, 1829 ConstantInt::get(IntptrTy, 2 * ASan.LongSize / 8)), 1830 IntptrPtrTy); 1831 IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2); 1832 1833 // Poison the stack redzones at the entry. 1834 Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB); 1835 poisonRedZones(L.ShadowBytes, IRB, ShadowBase, true); 1836 1837 // (Un)poison the stack before all ret instructions. 1838 for (auto Ret : RetVec) { 1839 IRBuilder<> IRBRet(Ret); 1840 // Mark the current frame as retired. 1841 IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic), 1842 BasePlus0); 1843 if (DoStackMalloc) { 1844 assert(StackMallocIdx >= 0); 1845 // if FakeStack != 0 // LocalStackBase == FakeStack 1846 // // In use-after-return mode, poison the whole stack frame. 1847 // if StackMallocIdx <= 4 1848 // // For small sizes inline the whole thing: 1849 // memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize); 1850 // **SavedFlagPtr(FakeStack) = 0 1851 // else 1852 // __asan_stack_free_N(FakeStack, LocalStackSize) 1853 // else 1854 // <This is not a fake stack; unpoison the redzones> 1855 Value *Cmp = 1856 IRBRet.CreateICmpNE(FakeStack, Constant::getNullValue(IntptrTy)); 1857 TerminatorInst *ThenTerm, *ElseTerm; 1858 SplitBlockAndInsertIfThenElse(Cmp, Ret, &ThenTerm, &ElseTerm); 1859 1860 IRBuilder<> IRBPoison(ThenTerm); 1861 if (StackMallocIdx <= 4) { 1862 int ClassSize = kMinStackMallocSize << StackMallocIdx; 1863 SetShadowToStackAfterReturnInlined(IRBPoison, ShadowBase, 1864 ClassSize >> Mapping.Scale); 1865 Value *SavedFlagPtrPtr = IRBPoison.CreateAdd( 1866 FakeStack, 1867 ConstantInt::get(IntptrTy, ClassSize - ASan.LongSize / 8)); 1868 Value *SavedFlagPtr = IRBPoison.CreateLoad( 1869 IRBPoison.CreateIntToPtr(SavedFlagPtrPtr, IntptrPtrTy)); 1870 IRBPoison.CreateStore( 1871 Constant::getNullValue(IRBPoison.getInt8Ty()), 1872 IRBPoison.CreateIntToPtr(SavedFlagPtr, IRBPoison.getInt8PtrTy())); 1873 } else { 1874 // For larger frames call __asan_stack_free_*. 1875 IRBPoison.CreateCall( 1876 AsanStackFreeFunc[StackMallocIdx], 1877 {FakeStack, ConstantInt::get(IntptrTy, LocalStackSize)}); 1878 } 1879 1880 IRBuilder<> IRBElse(ElseTerm); 1881 poisonRedZones(L.ShadowBytes, IRBElse, ShadowBase, false); 1882 } else if (HavePoisonedAllocas) { 1883 // If we poisoned some allocas in llvm.lifetime analysis, 1884 // unpoison whole stack frame now. 1885 poisonAlloca(LocalStackBase, LocalStackSize, IRBRet, false); 1886 } else { 1887 poisonRedZones(L.ShadowBytes, IRBRet, ShadowBase, false); 1888 } 1889 } 1890 1891 // We are done. Remove the old unused alloca instructions. 1892 for (auto AI : AllocaVec) AI->eraseFromParent(); 1893 } 1894 1895 void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size, 1896 IRBuilder<> &IRB, bool DoPoison) { 1897 // For now just insert the call to ASan runtime. 1898 Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy); 1899 Value *SizeArg = ConstantInt::get(IntptrTy, Size); 1900 IRB.CreateCall( 1901 DoPoison ? AsanPoisonStackMemoryFunc : AsanUnpoisonStackMemoryFunc, 1902 {AddrArg, SizeArg}); 1903 } 1904 1905 // Handling llvm.lifetime intrinsics for a given %alloca: 1906 // (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca. 1907 // (2) if %size is constant, poison memory for llvm.lifetime.end (to detect 1908 // invalid accesses) and unpoison it for llvm.lifetime.start (the memory 1909 // could be poisoned by previous llvm.lifetime.end instruction, as the 1910 // variable may go in and out of scope several times, e.g. in loops). 1911 // (3) if we poisoned at least one %alloca in a function, 1912 // unpoison the whole stack frame at function exit. 1913 1914 AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) { 1915 if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) 1916 // We're intested only in allocas we can handle. 1917 return ASan.isInterestingAlloca(*AI) ? AI : nullptr; 1918 // See if we've already calculated (or started to calculate) alloca for a 1919 // given value. 1920 AllocaForValueMapTy::iterator I = AllocaForValue.find(V); 1921 if (I != AllocaForValue.end()) return I->second; 1922 // Store 0 while we're calculating alloca for value V to avoid 1923 // infinite recursion if the value references itself. 1924 AllocaForValue[V] = nullptr; 1925 AllocaInst *Res = nullptr; 1926 if (CastInst *CI = dyn_cast<CastInst>(V)) 1927 Res = findAllocaForValue(CI->getOperand(0)); 1928 else if (PHINode *PN = dyn_cast<PHINode>(V)) { 1929 for (Value *IncValue : PN->incoming_values()) { 1930 // Allow self-referencing phi-nodes. 1931 if (IncValue == PN) continue; 1932 AllocaInst *IncValueAI = findAllocaForValue(IncValue); 1933 // AI for incoming values should exist and should all be equal. 1934 if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res)) 1935 return nullptr; 1936 Res = IncValueAI; 1937 } 1938 } 1939 if (Res) AllocaForValue[V] = Res; 1940 return Res; 1941 } 1942 1943 void FunctionStackPoisoner::handleDynamicAllocaCall(AllocaInst *AI) { 1944 IRBuilder<> IRB(AI); 1945 1946 const unsigned Align = std::max(kAllocaRzSize, AI->getAlignment()); 1947 const uint64_t AllocaRedzoneMask = kAllocaRzSize - 1; 1948 1949 Value *Zero = Constant::getNullValue(IntptrTy); 1950 Value *AllocaRzSize = ConstantInt::get(IntptrTy, kAllocaRzSize); 1951 Value *AllocaRzMask = ConstantInt::get(IntptrTy, AllocaRedzoneMask); 1952 1953 // Since we need to extend alloca with additional memory to locate 1954 // redzones, and OldSize is number of allocated blocks with 1955 // ElementSize size, get allocated memory size in bytes by 1956 // OldSize * ElementSize. 1957 const unsigned ElementSize = 1958 F.getParent()->getDataLayout().getTypeAllocSize(AI->getAllocatedType()); 1959 Value *OldSize = 1960 IRB.CreateMul(IRB.CreateIntCast(AI->getArraySize(), IntptrTy, false), 1961 ConstantInt::get(IntptrTy, ElementSize)); 1962 1963 // PartialSize = OldSize % 32 1964 Value *PartialSize = IRB.CreateAnd(OldSize, AllocaRzMask); 1965 1966 // Misalign = kAllocaRzSize - PartialSize; 1967 Value *Misalign = IRB.CreateSub(AllocaRzSize, PartialSize); 1968 1969 // PartialPadding = Misalign != kAllocaRzSize ? Misalign : 0; 1970 Value *Cond = IRB.CreateICmpNE(Misalign, AllocaRzSize); 1971 Value *PartialPadding = IRB.CreateSelect(Cond, Misalign, Zero); 1972 1973 // AdditionalChunkSize = Align + PartialPadding + kAllocaRzSize 1974 // Align is added to locate left redzone, PartialPadding for possible 1975 // partial redzone and kAllocaRzSize for right redzone respectively. 1976 Value *AdditionalChunkSize = IRB.CreateAdd( 1977 ConstantInt::get(IntptrTy, Align + kAllocaRzSize), PartialPadding); 1978 1979 Value *NewSize = IRB.CreateAdd(OldSize, AdditionalChunkSize); 1980 1981 // Insert new alloca with new NewSize and Align params. 1982 AllocaInst *NewAlloca = IRB.CreateAlloca(IRB.getInt8Ty(), NewSize); 1983 NewAlloca->setAlignment(Align); 1984 1985 // NewAddress = Address + Align 1986 Value *NewAddress = IRB.CreateAdd(IRB.CreatePtrToInt(NewAlloca, IntptrTy), 1987 ConstantInt::get(IntptrTy, Align)); 1988 1989 // Insert __asan_alloca_poison call for new created alloca. 1990 IRB.CreateCall(AsanAllocaPoisonFunc, {NewAddress, OldSize}); 1991 1992 // Store the last alloca's address to DynamicAllocaLayout. We'll need this 1993 // for unpoisoning stuff. 1994 IRB.CreateStore(IRB.CreatePtrToInt(NewAlloca, IntptrTy), DynamicAllocaLayout); 1995 1996 Value *NewAddressPtr = IRB.CreateIntToPtr(NewAddress, AI->getType()); 1997 1998 // Replace all uses of AddessReturnedByAlloca with NewAddressPtr. 1999 AI->replaceAllUsesWith(NewAddressPtr); 2000 2001 // We are done. Erase old alloca from parent. 2002 AI->eraseFromParent(); 2003 } 2004 2005 // isSafeAccess returns true if Addr is always inbounds with respect to its 2006 // base object. For example, it is a field access or an array access with 2007 // constant inbounds index. 2008 bool AddressSanitizer::isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis, 2009 Value *Addr, uint64_t TypeSize) const { 2010 SizeOffsetType SizeOffset = ObjSizeVis.compute(Addr); 2011 if (!ObjSizeVis.bothKnown(SizeOffset)) return false; 2012 uint64_t Size = SizeOffset.first.getZExtValue(); 2013 int64_t Offset = SizeOffset.second.getSExtValue(); 2014 // Three checks are required to ensure safety: 2015 // . Offset >= 0 (since the offset is given from the base ptr) 2016 // . Size >= Offset (unsigned) 2017 // . Size - Offset >= NeededSize (unsigned) 2018 return Offset >= 0 && Size >= uint64_t(Offset) && 2019 Size - uint64_t(Offset) >= TypeSize / 8; 2020 } 2021