lib/Transforms/Instrumentation/ThreadSanitizer.cpp

   1 //===-- ThreadSanitizer.cpp - race detector -------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file is a part of ThreadSanitizer, a race detector.
  10 //
  11 // The tool is under development, for the details about previous versions see
  12 // http://code.google.com/p/data-race-test
  13 //
  14 // The instrumentation phase is quite simple:
  15 //   - Insert calls to run-time library before every memory access.
  16 //      - Optimizations may apply to avoid instrumenting some of the accesses.
  17 //   - Insert calls at function entry/exit.
  18 // The rest is handled by the run-time library.
  19 //===----------------------------------------------------------------------===//
  20
  21 #include "llvm/Transforms/Instrumentation/ThreadSanitizer.h"
  22 #include "llvm/ADT/SmallPtrSet.h"
  23 #include "llvm/ADT/SmallString.h"
  24 #include "llvm/ADT/SmallVector.h"
  25 #include "llvm/ADT/Statistic.h"
  26 #include "llvm/ADT/StringExtras.h"
  27 #include "llvm/Analysis/CaptureTracking.h"
  28 #include "llvm/Analysis/TargetLibraryInfo.h"
  29 #include "llvm/Transforms/Utils/Local.h"
  30 #include "llvm/Analysis/ValueTracking.h"
  31 #include "llvm/IR/DataLayout.h"
  32 #include "llvm/IR/Function.h"
  33 #include "llvm/IR/IRBuilder.h"
  34 #include "llvm/IR/IntrinsicInst.h"
  35 #include "llvm/IR/Intrinsics.h"
  36 #include "llvm/IR/LLVMContext.h"
  37 #include "llvm/IR/Metadata.h"
  38 #include "llvm/IR/Module.h"
  39 #include "llvm/IR/Type.h"
  40 #include "llvm/ProfileData/InstrProf.h"
  41 #include "llvm/Support/CommandLine.h"
  42 #include "llvm/Support/Debug.h"
  43 #include "llvm/Support/MathExtras.h"
  44 #include "llvm/Support/raw_ostream.h"
  45 #include "llvm/Transforms/Instrumentation.h"
  46 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  47 #include "llvm/Transforms/Utils/EscapeEnumerator.h"
  48 #include "llvm/Transforms/Utils/ModuleUtils.h"
  49
  50 using namespace llvm;
  51
  52 #define DEBUG_TYPE "tsan"
  53
  54 static cl::opt<bool>  ClInstrumentMemoryAccesses(
  55     "tsan-instrument-memory-accesses", cl::init(true),
  56     cl::desc("Instrument memory accesses"), cl::Hidden);
  57 static cl::opt<bool>  ClInstrumentFuncEntryExit(
  58     "tsan-instrument-func-entry-exit", cl::init(true),
  59     cl::desc("Instrument function entry and exit"), cl::Hidden);
  60 static cl::opt<bool>  ClHandleCxxExceptions(
  61     "tsan-handle-cxx-exceptions", cl::init(true),
  62     cl::desc("Handle C++ exceptions (insert cleanup blocks for unwinding)"),
  63     cl::Hidden);
  64 static cl::opt<bool>  ClInstrumentAtomics(
  65     "tsan-instrument-atomics", cl::init(true),
  66     cl::desc("Instrument atomics"), cl::Hidden);
  67 static cl::opt<bool>  ClInstrumentMemIntrinsics(
  68     "tsan-instrument-memintrinsics", cl::init(true),
  69     cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
  70
  71 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
  72 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
  73 STATISTIC(NumOmittedReadsBeforeWrite,
  74           "Number of reads ignored due to following writes");
  75 STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
  76 STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
  77 STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
  78 STATISTIC(NumOmittedReadsFromConstantGlobals,
  79           "Number of reads from constant globals");
  80 STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
  81 STATISTIC(NumOmittedNonCaptured, "Number of accesses ignored due to capturing");
  82
  83 static const char *const kTsanModuleCtorName = "tsan.module_ctor";
  84 static const char *const kTsanInitName = "__tsan_init";
  85
  86 namespace {
  87
  88 /// ThreadSanitizer: instrument the code in module to find races.
  89 ///
  90 /// Instantiating ThreadSanitizer inserts the tsan runtime library API function
  91 /// declarations into the module if they don't exist already. Instantiating
  92 /// ensures the __tsan_init function is in the list of global constructors for
  93 /// the module.
  94 struct ThreadSanitizer {
  95   bool sanitizeFunction(Function &F, const TargetLibraryInfo &TLI);
  96
  97 private:
  98   void initialize(Module &M);
  99   bool instrumentLoadOrStore(Instruction *I, const DataLayout &DL);
 100   bool instrumentAtomic(Instruction *I, const DataLayout &DL);
 101   bool instrumentMemIntrinsic(Instruction *I);
 102   void chooseInstructionsToInstrument(SmallVectorImpl<Instruction *> &Local,
 103                                       SmallVectorImpl<Instruction *> &All,
 104                                       const DataLayout &DL);
 105   bool addrPointsToConstantData(Value *Addr);
 106   int getMemoryAccessFuncIndex(Value *Addr, const DataLayout &DL);
 107   void InsertRuntimeIgnores(Function &F);
 108
 109   Type *IntptrTy;
 110   FunctionCallee TsanFuncEntry;
 111   FunctionCallee TsanFuncExit;
 112   FunctionCallee TsanIgnoreBegin;
 113   FunctionCallee TsanIgnoreEnd;
 114   // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
 115   static const size_t kNumberOfAccessSizes = 5;
 116   FunctionCallee TsanRead[kNumberOfAccessSizes];
 117   FunctionCallee TsanWrite[kNumberOfAccessSizes];
 118   FunctionCallee TsanUnalignedRead[kNumberOfAccessSizes];
 119   FunctionCallee TsanUnalignedWrite[kNumberOfAccessSizes];
 120   FunctionCallee TsanAtomicLoad[kNumberOfAccessSizes];
 121   FunctionCallee TsanAtomicStore[kNumberOfAccessSizes];
 122   FunctionCallee TsanAtomicRMW[AtomicRMWInst::LAST_BINOP + 1]
 123                               [kNumberOfAccessSizes];
 124   FunctionCallee TsanAtomicCAS[kNumberOfAccessSizes];
 125   FunctionCallee TsanAtomicThreadFence;
 126   FunctionCallee TsanAtomicSignalFence;
 127   FunctionCallee TsanVptrUpdate;
 128   FunctionCallee TsanVptrLoad;
 129   FunctionCallee MemmoveFn, MemcpyFn, MemsetFn;
 130 };
 131
 132 struct ThreadSanitizerLegacyPass : FunctionPass {
 133   ThreadSanitizerLegacyPass() : FunctionPass(ID) {}
 134   StringRef getPassName() const override;
 135   void getAnalysisUsage(AnalysisUsage &AU) const override;
 136   bool runOnFunction(Function &F) override;
 137   bool doInitialization(Module &M) override;
 138   static char ID; // Pass identification, replacement for typeid.
 139 private:
 140   Optional<ThreadSanitizer> TSan;
 141 };
 142
 143 void insertModuleCtor(Module &M) {
 144   getOrCreateSanitizerCtorAndInitFunctions(
 145       M, kTsanModuleCtorName, kTsanInitName, /*InitArgTypes=*/{},
 146       /*InitArgs=*/{},
 147       // This callback is invoked when the functions are created the first
 148       // time. Hook them into the global ctors list in that case:
 149       [&](Function *Ctor, FunctionCallee) { appendToGlobalCtors(M, Ctor, 0); });
 150 }
 151
 152 }  // namespace
 153
 154 PreservedAnalyses ThreadSanitizerPass::run(Function &F,
 155                                            FunctionAnalysisManager &FAM) {
 156   ThreadSanitizer TSan;
 157   if (TSan.sanitizeFunction(F, FAM.getResult<TargetLibraryAnalysis>(F)))
 158     return PreservedAnalyses::none();
 159   return PreservedAnalyses::all();
 160 }
 161
 162 PreservedAnalyses ThreadSanitizerPass::run(Module &M,
 163                                            ModuleAnalysisManager &MAM) {
 164   insertModuleCtor(M);
 165   return PreservedAnalyses::none();
 166 }
 167
 168 char ThreadSanitizerLegacyPass::ID = 0;
 169 INITIALIZE_PASS_BEGIN(ThreadSanitizerLegacyPass, "tsan",
 170                       "ThreadSanitizer: detects data races.", false, false)
 171 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
 172 INITIALIZE_PASS_END(ThreadSanitizerLegacyPass, "tsan",
 173                     "ThreadSanitizer: detects data races.", false, false)
 174
 175 StringRef ThreadSanitizerLegacyPass::getPassName() const {
 176   return "ThreadSanitizerLegacyPass";
 177 }
 178
 179 void ThreadSanitizerLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
 180   AU.addRequired<TargetLibraryInfoWrapperPass>();
 181 }
 182
 183 bool ThreadSanitizerLegacyPass::doInitialization(Module &M) {
 184   insertModuleCtor(M);
 185   TSan.emplace();
 186   return true;
 187 }
 188
 189 bool ThreadSanitizerLegacyPass::runOnFunction(Function &F) {
 190   auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
 191   TSan->sanitizeFunction(F, TLI);
 192   return true;
 193 }
 194
 195 FunctionPass *llvm::createThreadSanitizerLegacyPassPass() {
 196   return new ThreadSanitizerLegacyPass();
 197 }
 198
 199 void ThreadSanitizer::initialize(Module &M) {
 200   const DataLayout &DL = M.getDataLayout();
 201   IntptrTy = DL.getIntPtrType(M.getContext());
 202
 203   IRBuilder<> IRB(M.getContext());
 204   AttributeList Attr;
 205   Attr = Attr.addAttribute(M.getContext(), AttributeList::FunctionIndex,
 206                            Attribute::NoUnwind);
 207   // Initialize the callbacks.
 208   TsanFuncEntry = M.getOrInsertFunction("__tsan_func_entry", Attr,
 209                                         IRB.getVoidTy(), IRB.getInt8PtrTy());
 210   TsanFuncExit =
 211       M.getOrInsertFunction("__tsan_func_exit", Attr, IRB.getVoidTy());
 212   TsanIgnoreBegin = M.getOrInsertFunction("__tsan_ignore_thread_begin", Attr,
 213                                           IRB.getVoidTy());
 214   TsanIgnoreEnd =
 215       M.getOrInsertFunction("__tsan_ignore_thread_end", Attr, IRB.getVoidTy());
 216   IntegerType *OrdTy = IRB.getInt32Ty();
 217   for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
 218     const unsigned ByteSize = 1U << i;
 219     const unsigned BitSize = ByteSize * 8;
 220     std::string ByteSizeStr = utostr(ByteSize);
 221     std::string BitSizeStr = utostr(BitSize);
 222     SmallString<32> ReadName("__tsan_read" + ByteSizeStr);
 223     TsanRead[i] = M.getOrInsertFunction(ReadName, Attr, IRB.getVoidTy(),
 224                                         IRB.getInt8PtrTy());
 225
 226     SmallString<32> WriteName("__tsan_write" + ByteSizeStr);
 227     TsanWrite[i] = M.getOrInsertFunction(WriteName, Attr, IRB.getVoidTy(),
 228                                          IRB.getInt8PtrTy());
 229
 230     SmallString<64> UnalignedReadName("__tsan_unaligned_read" + ByteSizeStr);
 231     TsanUnalignedRead[i] = M.getOrInsertFunction(
 232         UnalignedReadName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
 233
 234     SmallString<64> UnalignedWriteName("__tsan_unaligned_write" + ByteSizeStr);
 235     TsanUnalignedWrite[i] = M.getOrInsertFunction(
 236         UnalignedWriteName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
 237
 238     Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
 239     Type *PtrTy = Ty->getPointerTo();
 240     SmallString<32> AtomicLoadName("__tsan_atomic" + BitSizeStr + "_load");
 241     TsanAtomicLoad[i] =
 242         M.getOrInsertFunction(AtomicLoadName, Attr, Ty, PtrTy, OrdTy);
 243
 244     SmallString<32> AtomicStoreName("__tsan_atomic" + BitSizeStr + "_store");
 245     TsanAtomicStore[i] = M.getOrInsertFunction(
 246         AtomicStoreName, Attr, IRB.getVoidTy(), PtrTy, Ty, OrdTy);
 247
 248     for (int op = AtomicRMWInst::FIRST_BINOP;
 249         op <= AtomicRMWInst::LAST_BINOP; ++op) {
 250       TsanAtomicRMW[op][i] = nullptr;
 251       const char *NamePart = nullptr;
 252       if (op == AtomicRMWInst::Xchg)
 253         NamePart = "_exchange";
 254       else if (op == AtomicRMWInst::Add)
 255         NamePart = "_fetch_add";
 256       else if (op == AtomicRMWInst::Sub)
 257         NamePart = "_fetch_sub";
 258       else if (op == AtomicRMWInst::And)
 259         NamePart = "_fetch_and";
 260       else if (op == AtomicRMWInst::Or)
 261         NamePart = "_fetch_or";
 262       else if (op == AtomicRMWInst::Xor)
 263         NamePart = "_fetch_xor";
 264       else if (op == AtomicRMWInst::Nand)
 265         NamePart = "_fetch_nand";
 266       else
 267         continue;
 268       SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
 269       TsanAtomicRMW[op][i] =
 270           M.getOrInsertFunction(RMWName, Attr, Ty, PtrTy, Ty, OrdTy);
 271     }
 272
 273     SmallString<32> AtomicCASName("__tsan_atomic" + BitSizeStr +
 274                                   "_compare_exchange_val");
 275     TsanAtomicCAS[i] = M.getOrInsertFunction(AtomicCASName, Attr, Ty, PtrTy, Ty,
 276                                              Ty, OrdTy, OrdTy);
 277   }
 278   TsanVptrUpdate =
 279       M.getOrInsertFunction("__tsan_vptr_update", Attr, IRB.getVoidTy(),
 280                             IRB.getInt8PtrTy(), IRB.getInt8PtrTy());
 281   TsanVptrLoad = M.getOrInsertFunction("__tsan_vptr_read", Attr,
 282                                        IRB.getVoidTy(), IRB.getInt8PtrTy());
 283   TsanAtomicThreadFence = M.getOrInsertFunction("__tsan_atomic_thread_fence",
 284                                                 Attr, IRB.getVoidTy(), OrdTy);
 285   TsanAtomicSignalFence = M.getOrInsertFunction("__tsan_atomic_signal_fence",
 286                                                 Attr, IRB.getVoidTy(), OrdTy);
 287
 288   MemmoveFn =
 289       M.getOrInsertFunction("memmove", Attr, IRB.getInt8PtrTy(),
 290                             IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy);
 291   MemcpyFn =
 292       M.getOrInsertFunction("memcpy", Attr, IRB.getInt8PtrTy(),
 293                             IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy);
 294   MemsetFn =
 295       M.getOrInsertFunction("memset", Attr, IRB.getInt8PtrTy(),
 296                             IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy);
 297 }
 298
 299 static bool isVtableAccess(Instruction *I) {
 300   if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
 301     return Tag->isTBAAVtableAccess();
 302   return false;
 303 }
 304
 305 // Do not instrument known races/"benign races" that come from compiler
 306 // instrumentatin. The user has no way of suppressing them.
 307 static bool shouldInstrumentReadWriteFromAddress(const Module *M, Value *Addr) {
 308   // Peel off GEPs and BitCasts.
 309   Addr = Addr->stripInBoundsOffsets();
 310
 311   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
 312     if (GV->hasSection()) {
 313       StringRef SectionName = GV->getSection();
 314       // Check if the global is in the PGO counters section.
 315       auto OF = Triple(M->getTargetTriple()).getObjectFormat();
 316       if (SectionName.endswith(
 317               getInstrProfSectionName(IPSK_cnts, OF, /*AddSegmentInfo=*/false)))
 318         return false;
 319     }
 320
 321     // Check if the global is private gcov data.
 322     if (GV->getName().startswith("__llvm_gcov") ||
 323         GV->getName().startswith("__llvm_gcda"))
 324       return false;
 325   }
 326
 327   // Do not instrument acesses from different address spaces; we cannot deal
 328   // with them.
 329   if (Addr) {
 330     Type *PtrTy = cast<PointerType>(Addr->getType()->getScalarType());
 331     if (PtrTy->getPointerAddressSpace() != 0)
 332       return false;
 333   }
 334
 335   return true;
 336 }
 337
 338 bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
 339   // If this is a GEP, just analyze its pointer operand.
 340   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
 341     Addr = GEP->getPointerOperand();
 342
 343   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
 344     if (GV->isConstant()) {
 345       // Reads from constant globals can not race with any writes.
 346       NumOmittedReadsFromConstantGlobals++;
 347       return true;
 348     }
 349   } else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
 350     if (isVtableAccess(L)) {
 351       // Reads from a vtable pointer can not race with any writes.
 352       NumOmittedReadsFromVtable++;
 353       return true;
 354     }
 355   }
 356   return false;
 357 }
 358
 359 // Instrumenting some of the accesses may be proven redundant.
 360 // Currently handled:
 361 //  - read-before-write (within same BB, no calls between)
 362 //  - not captured variables
 363 //
 364 // We do not handle some of the patterns that should not survive
 365 // after the classic compiler optimizations.
 366 // E.g. two reads from the same temp should be eliminated by CSE,
 367 // two writes should be eliminated by DSE, etc.
 368 //
 369 // 'Local' is a vector of insns within the same BB (no calls between).
 370 // 'All' is a vector of insns that will be instrumented.
 371 void ThreadSanitizer::chooseInstructionsToInstrument(
 372     SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
 373     const DataLayout &DL) {
 374   SmallPtrSet<Value*, 8> WriteTargets;
 375   // Iterate from the end.
 376   for (Instruction *I : reverse(Local)) {
 377     if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
 378       Value *Addr = Store->getPointerOperand();
 379       if (!shouldInstrumentReadWriteFromAddress(I->getModule(), Addr))
 380         continue;
 381       WriteTargets.insert(Addr);
 382     } else {
 383       LoadInst *Load = cast<LoadInst>(I);
 384       Value *Addr = Load->getPointerOperand();
 385       if (!shouldInstrumentReadWriteFromAddress(I->getModule(), Addr))
 386         continue;
 387       if (WriteTargets.count(Addr)) {
 388         // We will write to this temp, so no reason to analyze the read.
 389         NumOmittedReadsBeforeWrite++;
 390         continue;
 391       }
 392       if (addrPointsToConstantData(Addr)) {
 393         // Addr points to some constant data -- it can not race with any writes.
 394         continue;
 395       }
 396     }
 397     Value *Addr = isa<StoreInst>(*I)
 398         ? cast<StoreInst>(I)->getPointerOperand()
 399         : cast<LoadInst>(I)->getPointerOperand();
 400     if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
 401         !PointerMayBeCaptured(Addr, true, true)) {
 402       // The variable is addressable but not captured, so it cannot be
 403       // referenced from a different thread and participate in a data race
 404       // (see llvm/Analysis/CaptureTracking.h for details).
 405       NumOmittedNonCaptured++;
 406       continue;
 407     }
 408     All.push_back(I);
 409   }
 410   Local.clear();
 411 }
 412
 413 static bool isAtomic(Instruction *I) {
 414   // TODO: Ask TTI whether synchronization scope is between threads.
 415   if (LoadInst *LI = dyn_cast<LoadInst>(I))
 416     return LI->isAtomic() && LI->getSyncScopeID() != SyncScope::SingleThread;
 417   if (StoreInst *SI = dyn_cast<StoreInst>(I))
 418     return SI->isAtomic() && SI->getSyncScopeID() != SyncScope::SingleThread;
 419   if (isa<AtomicRMWInst>(I))
 420     return true;
 421   if (isa<AtomicCmpXchgInst>(I))
 422     return true;
 423   if (isa<FenceInst>(I))
 424     return true;
 425   return false;
 426 }
 427
 428 void ThreadSanitizer::InsertRuntimeIgnores(Function &F) {
 429   IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
 430   IRB.CreateCall(TsanIgnoreBegin);
 431   EscapeEnumerator EE(F, "tsan_ignore_cleanup", ClHandleCxxExceptions);
 432   while (IRBuilder<> *AtExit = EE.Next()) {
 433     AtExit->CreateCall(TsanIgnoreEnd);
 434   }
 435 }
 436
 437 bool ThreadSanitizer::sanitizeFunction(Function &F,
 438                                        const TargetLibraryInfo &TLI) {
 439   // This is required to prevent instrumenting call to __tsan_init from within
 440   // the module constructor.
 441   if (F.getName() == kTsanModuleCtorName)
 442     return false;
 443   initialize(*F.getParent());
 444   SmallVector<Instruction*, 8> AllLoadsAndStores;
 445   SmallVector<Instruction*, 8> LocalLoadsAndStores;
 446   SmallVector<Instruction*, 8> AtomicAccesses;
 447   SmallVector<Instruction*, 8> MemIntrinCalls;
 448   bool Res = false;
 449   bool HasCalls = false;
 450   bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeThread);
 451   const DataLayout &DL = F.getParent()->getDataLayout();
 452
 453   // Traverse all instructions, collect loads/stores/returns, check for calls.
 454   for (auto &BB : F) {
 455     for (auto &Inst : BB) {
 456       if (isAtomic(&Inst))
 457         AtomicAccesses.push_back(&Inst);
 458       else if (isa<LoadInst>(Inst) || isa<StoreInst>(Inst))
 459         LocalLoadsAndStores.push_back(&Inst);
 460       else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
 461         if (CallInst *CI = dyn_cast<CallInst>(&Inst))
 462           maybeMarkSanitizerLibraryCallNoBuiltin(CI, &TLI);
 463         if (isa<MemIntrinsic>(Inst))
 464           MemIntrinCalls.push_back(&Inst);
 465         HasCalls = true;
 466         chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores,
 467                                        DL);
 468       }
 469     }
 470     chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores, DL);
 471   }
 472
 473   // We have collected all loads and stores.
 474   // FIXME: many of these accesses do not need to be checked for races
 475   // (e.g. variables that do not escape, etc).
 476
 477   // Instrument memory accesses only if we want to report bugs in the function.
 478   if (ClInstrumentMemoryAccesses && SanitizeFunction)
 479     for (auto Inst : AllLoadsAndStores) {
 480       Res |= instrumentLoadOrStore(Inst, DL);
 481     }
 482
 483   // Instrument atomic memory accesses in any case (they can be used to
 484   // implement synchronization).
 485   if (ClInstrumentAtomics)
 486     for (auto Inst : AtomicAccesses) {
 487       Res |= instrumentAtomic(Inst, DL);
 488     }
 489
 490   if (ClInstrumentMemIntrinsics && SanitizeFunction)
 491     for (auto Inst : MemIntrinCalls) {
 492       Res |= instrumentMemIntrinsic(Inst);
 493     }
 494
 495   if (F.hasFnAttribute("sanitize_thread_no_checking_at_run_time")) {
 496     assert(!F.hasFnAttribute(Attribute::SanitizeThread));
 497     if (HasCalls)
 498       InsertRuntimeIgnores(F);
 499   }
 500
 501   // Instrument function entry/exit points if there were instrumented accesses.
 502   if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
 503     IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
 504     Value *ReturnAddress = IRB.CreateCall(
 505         Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
 506         IRB.getInt32(0));
 507     IRB.CreateCall(TsanFuncEntry, ReturnAddress);
 508
 509     EscapeEnumerator EE(F, "tsan_cleanup", ClHandleCxxExceptions);
 510     while (IRBuilder<> *AtExit = EE.Next()) {
 511       AtExit->CreateCall(TsanFuncExit, {});
 512     }
 513     Res = true;
 514   }
 515   return Res;
 516 }
 517
 518 bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
 519                                             const DataLayout &DL) {
 520   IRBuilder<> IRB(I);
 521   bool IsWrite = isa<StoreInst>(*I);
 522   Value *Addr = IsWrite
 523       ? cast<StoreInst>(I)->getPointerOperand()
 524       : cast<LoadInst>(I)->getPointerOperand();
 525
 526   // swifterror memory addresses are mem2reg promoted by instruction selection.
 527   // As such they cannot have regular uses like an instrumentation function and
 528   // it makes no sense to track them as memory.
 529   if (Addr->isSwiftError())
 530     return false;
 531
 532   int Idx = getMemoryAccessFuncIndex(Addr, DL);
 533   if (Idx < 0)
 534     return false;
 535   if (IsWrite && isVtableAccess(I)) {
 536     LLVM_DEBUG(dbgs() << "  VPTR : " << *I << "\n");
 537     Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
 538     // StoredValue may be a vector type if we are storing several vptrs at once.
 539     // In this case, just take the first element of the vector since this is
 540     // enough to find vptr races.
 541     if (isa<VectorType>(StoredValue->getType()))
 542       StoredValue = IRB.CreateExtractElement(
 543           StoredValue, ConstantInt::get(IRB.getInt32Ty(), 0));
 544     if (StoredValue->getType()->isIntegerTy())
 545       StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
 546     // Call TsanVptrUpdate.
 547     IRB.CreateCall(TsanVptrUpdate,
 548                    {IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
 549                     IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy())});
 550     NumInstrumentedVtableWrites++;
 551     return true;
 552   }
 553   if (!IsWrite && isVtableAccess(I)) {
 554     IRB.CreateCall(TsanVptrLoad,
 555                    IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
 556     NumInstrumentedVtableReads++;
 557     return true;
 558   }
 559   const unsigned Alignment = IsWrite
 560       ? cast<StoreInst>(I)->getAlignment()
 561       : cast<LoadInst>(I)->getAlignment();
 562   Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
 563   const uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
 564   FunctionCallee OnAccessFunc = nullptr;
 565   if (Alignment == 0 || Alignment >= 8 || (Alignment % (TypeSize / 8)) == 0)
 566     OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
 567   else
 568     OnAccessFunc = IsWrite ? TsanUnalignedWrite[Idx] : TsanUnalignedRead[Idx];
 569   IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
 570   if (IsWrite) NumInstrumentedWrites++;
 571   else         NumInstrumentedReads++;
 572   return true;
 573 }
 574
 575 static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
 576   uint32_t v = 0;
 577   switch (ord) {
 578     case AtomicOrdering::NotAtomic:
 579       llvm_unreachable("unexpected atomic ordering!");
 580     case AtomicOrdering::Unordered:              LLVM_FALLTHROUGH;
 581     case AtomicOrdering::Monotonic:              v = 0; break;
 582     // Not specified yet:
 583     // case AtomicOrdering::Consume:                v = 1; break;
 584     case AtomicOrdering::Acquire:                v = 2; break;
 585     case AtomicOrdering::Release:                v = 3; break;
 586     case AtomicOrdering::AcquireRelease:         v = 4; break;
 587     case AtomicOrdering::SequentiallyConsistent: v = 5; break;
 588   }
 589   return IRB->getInt32(v);
 590 }
 591
 592 // If a memset intrinsic gets inlined by the code gen, we will miss races on it.
 593 // So, we either need to ensure the intrinsic is not inlined, or instrument it.
 594 // We do not instrument memset/memmove/memcpy intrinsics (too complicated),
 595 // instead we simply replace them with regular function calls, which are then
 596 // intercepted by the run-time.
 597 // Since tsan is running after everyone else, the calls should not be
 598 // replaced back with intrinsics. If that becomes wrong at some point,
 599 // we will need to call e.g. __tsan_memset to avoid the intrinsics.
 600 bool ThreadSanitizer::instrumentMemIntrinsic(Instruction *I) {
 601   IRBuilder<> IRB(I);
 602   if (MemSetInst *M = dyn_cast<MemSetInst>(I)) {
 603     IRB.CreateCall(
 604         MemsetFn,
 605         {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
 606          IRB.CreateIntCast(M->getArgOperand(1), IRB.getInt32Ty(), false),
 607          IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
 608     I->eraseFromParent();
 609   } else if (MemTransferInst *M = dyn_cast<MemTransferInst>(I)) {
 610     IRB.CreateCall(
 611         isa<MemCpyInst>(M) ? MemcpyFn : MemmoveFn,
 612         {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
 613          IRB.CreatePointerCast(M->getArgOperand(1), IRB.getInt8PtrTy()),
 614          IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
 615     I->eraseFromParent();
 616   }
 617   return false;
 618 }
 619
 620 // Both llvm and ThreadSanitizer atomic operations are based on C++11/C1x
 621 // standards.  For background see C++11 standard.  A slightly older, publicly
 622 // available draft of the standard (not entirely up-to-date, but close enough
 623 // for casual browsing) is available here:
 624 // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
 625 // The following page contains more background information:
 626 // http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/
 627
 628 bool ThreadSanitizer::instrumentAtomic(Instruction *I, const DataLayout &DL) {
 629   IRBuilder<> IRB(I);
 630   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
 631     Value *Addr = LI->getPointerOperand();
 632     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 633     if (Idx < 0)
 634       return false;
 635     const unsigned ByteSize = 1U << Idx;
 636     const unsigned BitSize = ByteSize * 8;
 637     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 638     Type *PtrTy = Ty->getPointerTo();
 639     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 640                      createOrdering(&IRB, LI->getOrdering())};
 641     Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
 642     Value *C = IRB.CreateCall(TsanAtomicLoad[Idx], Args);
 643     Value *Cast = IRB.CreateBitOrPointerCast(C, OrigTy);
 644     I->replaceAllUsesWith(Cast);
 645   } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
 646     Value *Addr = SI->getPointerOperand();
 647     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 648     if (Idx < 0)
 649       return false;
 650     const unsigned ByteSize = 1U << Idx;
 651     const unsigned BitSize = ByteSize * 8;
 652     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 653     Type *PtrTy = Ty->getPointerTo();
 654     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 655                      IRB.CreateBitOrPointerCast(SI->getValueOperand(), Ty),
 656                      createOrdering(&IRB, SI->getOrdering())};
 657     CallInst *C = CallInst::Create(TsanAtomicStore[Idx], Args);
 658     ReplaceInstWithInst(I, C);
 659   } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I)) {
 660     Value *Addr = RMWI->getPointerOperand();
 661     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 662     if (Idx < 0)
 663       return false;
 664     FunctionCallee F = TsanAtomicRMW[RMWI->getOperation()][Idx];
 665     if (!F)
 666       return false;
 667     const unsigned ByteSize = 1U << Idx;
 668     const unsigned BitSize = ByteSize * 8;
 669     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 670     Type *PtrTy = Ty->getPointerTo();
 671     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 672                      IRB.CreateIntCast(RMWI->getValOperand(), Ty, false),
 673                      createOrdering(&IRB, RMWI->getOrdering())};
 674     CallInst *C = CallInst::Create(F, Args);
 675     ReplaceInstWithInst(I, C);
 676   } else if (AtomicCmpXchgInst *CASI = dyn_cast<AtomicCmpXchgInst>(I)) {
 677     Value *Addr = CASI->getPointerOperand();
 678     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 679     if (Idx < 0)
 680       return false;
 681     const unsigned ByteSize = 1U << Idx;
 682     const unsigned BitSize = ByteSize * 8;
 683     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 684     Type *PtrTy = Ty->getPointerTo();
 685     Value *CmpOperand =
 686       IRB.CreateBitOrPointerCast(CASI->getCompareOperand(), Ty);
 687     Value *NewOperand =
 688       IRB.CreateBitOrPointerCast(CASI->getNewValOperand(), Ty);
 689     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 690                      CmpOperand,
 691                      NewOperand,
 692                      createOrdering(&IRB, CASI->getSuccessOrdering()),
 693                      createOrdering(&IRB, CASI->getFailureOrdering())};
 694     CallInst *C = IRB.CreateCall(TsanAtomicCAS[Idx], Args);
 695     Value *Success = IRB.CreateICmpEQ(C, CmpOperand);
 696     Value *OldVal = C;
 697     Type *OrigOldValTy = CASI->getNewValOperand()->getType();
 698     if (Ty != OrigOldValTy) {
 699       // The value is a pointer, so we need to cast the return value.
 700       OldVal = IRB.CreateIntToPtr(C, OrigOldValTy);
 701     }
 702
 703     Value *Res =
 704       IRB.CreateInsertValue(UndefValue::get(CASI->getType()), OldVal, 0);
 705     Res = IRB.CreateInsertValue(Res, Success, 1);
 706
 707     I->replaceAllUsesWith(Res);
 708     I->eraseFromParent();
 709   } else if (FenceInst *FI = dyn_cast<FenceInst>(I)) {
 710     Value *Args[] = {createOrdering(&IRB, FI->getOrdering())};
 711     FunctionCallee F = FI->getSyncScopeID() == SyncScope::SingleThread
 712                            ? TsanAtomicSignalFence
 713                            : TsanAtomicThreadFence;
 714     CallInst *C = CallInst::Create(F, Args);
 715     ReplaceInstWithInst(I, C);
 716   }
 717   return true;
 718 }
 719
 720 int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr,
 721                                               const DataLayout &DL) {
 722   Type *OrigPtrTy = Addr->getType();
 723   Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
 724   assert(OrigTy->isSized());
 725   uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
 726   if (TypeSize != 8  && TypeSize != 16 &&
 727       TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
 728     NumAccessesWithBadSize++;
 729     // Ignore all unusual sizes.
 730     return -1;
 731   }
 732   size_t Idx = countTrailingZeros(TypeSize / 8);
 733   assert(Idx < kNumberOfAccessSizes);
 734   return Idx;
 735 }