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