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/Analysis/ValueTracking.h"
30#include "llvm/IR/DataLayout.h"
31#include "llvm/IR/Function.h"
32#include "llvm/IR/IRBuilder.h"
33#include "llvm/IR/IntrinsicInst.h"
34#include "llvm/IR/Intrinsics.h"
35#include "llvm/IR/LLVMContext.h"
36#include "llvm/IR/Metadata.h"
37#include "llvm/IR/Module.h"
38#include "llvm/IR/Type.h"
39#include "llvm/InitializePasses.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/Local.h"
49#include "llvm/Transforms/Utils/ModuleUtils.h"
50
51using namespace llvm;
52
53#define DEBUG_TYPE "tsan"
54
55static cl::opt<bool>  ClInstrumentMemoryAccesses(
56    "tsan-instrument-memory-accesses", cl::init(true),
57    cl::desc("Instrument memory accesses"), cl::Hidden);
58static cl::opt<bool>  ClInstrumentFuncEntryExit(
59    "tsan-instrument-func-entry-exit", cl::init(true),
60    cl::desc("Instrument function entry and exit"), cl::Hidden);
61static cl::opt<bool>  ClHandleCxxExceptions(
62    "tsan-handle-cxx-exceptions", cl::init(true),
63    cl::desc("Handle C++ exceptions (insert cleanup blocks for unwinding)"),
64    cl::Hidden);
65static cl::opt<bool>  ClInstrumentAtomics(
66    "tsan-instrument-atomics", cl::init(true),
67    cl::desc("Instrument atomics"), cl::Hidden);
68static cl::opt<bool>  ClInstrumentMemIntrinsics(
69    "tsan-instrument-memintrinsics", cl::init(true),
70    cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
71static cl::opt<bool>  ClDistinguishVolatile(
72    "tsan-distinguish-volatile", cl::init(false),
73    cl::desc("Emit special instrumentation for accesses to volatiles"),
74    cl::Hidden);
75static cl::opt<bool>  ClInstrumentReadBeforeWrite(
76    "tsan-instrument-read-before-write", cl::init(false),
77    cl::desc("Do not eliminate read instrumentation for read-before-writes"),
78    cl::Hidden);
79
80STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
81STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
82STATISTIC(NumOmittedReadsBeforeWrite,
83          "Number of reads ignored due to following writes");
84STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
85STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
86STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
87STATISTIC(NumOmittedReadsFromConstantGlobals,
88          "Number of reads from constant globals");
89STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
90STATISTIC(NumOmittedNonCaptured, "Number of accesses ignored due to capturing");
91
92static const char *const kTsanModuleCtorName = "tsan.module_ctor";
93static const char *const kTsanInitName = "__tsan_init";
94
95namespace {
96
97/// ThreadSanitizer: instrument the code in module to find races.
98///
99/// Instantiating ThreadSanitizer inserts the tsan runtime library API function
100/// declarations into the module if they don't exist already. Instantiating
101/// ensures the __tsan_init function is in the list of global constructors for
102/// the module.
103struct ThreadSanitizer {
104  bool sanitizeFunction(Function &F, const TargetLibraryInfo &TLI);
105
106private:
107  void initialize(Module &M);
108  bool instrumentLoadOrStore(Instruction *I, const DataLayout &DL);
109  bool instrumentAtomic(Instruction *I, const DataLayout &DL);
110  bool instrumentMemIntrinsic(Instruction *I);
111  void chooseInstructionsToInstrument(SmallVectorImpl<Instruction *> &Local,
112                                      SmallVectorImpl<Instruction *> &All,
113                                      const DataLayout &DL);
114  bool addrPointsToConstantData(Value *Addr);
115  int getMemoryAccessFuncIndex(Value *Addr, const DataLayout &DL);
116  void InsertRuntimeIgnores(Function &F);
117
118  Type *IntptrTy;
119  FunctionCallee TsanFuncEntry;
120  FunctionCallee TsanFuncExit;
121  FunctionCallee TsanIgnoreBegin;
122  FunctionCallee TsanIgnoreEnd;
123  // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
124  static const size_t kNumberOfAccessSizes = 5;
125  FunctionCallee TsanRead[kNumberOfAccessSizes];
126  FunctionCallee TsanWrite[kNumberOfAccessSizes];
127  FunctionCallee TsanUnalignedRead[kNumberOfAccessSizes];
128  FunctionCallee TsanUnalignedWrite[kNumberOfAccessSizes];
129  FunctionCallee TsanVolatileRead[kNumberOfAccessSizes];
130  FunctionCallee TsanVolatileWrite[kNumberOfAccessSizes];
131  FunctionCallee TsanUnalignedVolatileRead[kNumberOfAccessSizes];
132  FunctionCallee TsanUnalignedVolatileWrite[kNumberOfAccessSizes];
133  FunctionCallee TsanAtomicLoad[kNumberOfAccessSizes];
134  FunctionCallee TsanAtomicStore[kNumberOfAccessSizes];
135  FunctionCallee TsanAtomicRMW[AtomicRMWInst::LAST_BINOP + 1]
136                              [kNumberOfAccessSizes];
137  FunctionCallee TsanAtomicCAS[kNumberOfAccessSizes];
138  FunctionCallee TsanAtomicThreadFence;
139  FunctionCallee TsanAtomicSignalFence;
140  FunctionCallee TsanVptrUpdate;
141  FunctionCallee TsanVptrLoad;
142  FunctionCallee MemmoveFn, MemcpyFn, MemsetFn;
143};
144
145struct ThreadSanitizerLegacyPass : FunctionPass {
146  ThreadSanitizerLegacyPass() : FunctionPass(ID) {
147    initializeThreadSanitizerLegacyPassPass(*PassRegistry::getPassRegistry());
148  }
149  StringRef getPassName() const override;
150  void getAnalysisUsage(AnalysisUsage &AU) const override;
151  bool runOnFunction(Function &F) override;
152  bool doInitialization(Module &M) override;
153  static char ID; // Pass identification, replacement for typeid.
154private:
155  Optional<ThreadSanitizer> TSan;
156};
157
158void insertModuleCtor(Module &M) {
159  getOrCreateSanitizerCtorAndInitFunctions(
160      M, kTsanModuleCtorName, kTsanInitName, /*InitArgTypes=*/{},
161      /*InitArgs=*/{},
162      // This callback is invoked when the functions are created the first
163      // time. Hook them into the global ctors list in that case:
164      [&](Function *Ctor, FunctionCallee) { appendToGlobalCtors(M, Ctor, 0); });
165}
166
167}  // namespace
168
169PreservedAnalyses ThreadSanitizerPass::run(Function &F,
170                                           FunctionAnalysisManager &FAM) {
171  ThreadSanitizer TSan;
172  if (TSan.sanitizeFunction(F, FAM.getResult<TargetLibraryAnalysis>(F)))
173    return PreservedAnalyses::none();
174  return PreservedAnalyses::all();
175}
176
177PreservedAnalyses ThreadSanitizerPass::run(Module &M,
178                                           ModuleAnalysisManager &MAM) {
179  insertModuleCtor(M);
180  return PreservedAnalyses::none();
181}
182
183char ThreadSanitizerLegacyPass::ID = 0;
184INITIALIZE_PASS_BEGIN(ThreadSanitizerLegacyPass, "tsan",
185                      "ThreadSanitizer: detects data races.", false, false)
186INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
187INITIALIZE_PASS_END(ThreadSanitizerLegacyPass, "tsan",
188                    "ThreadSanitizer: detects data races.", false, false)
189
190StringRef ThreadSanitizerLegacyPass::getPassName() const {
191  return "ThreadSanitizerLegacyPass";
192}
193
194void ThreadSanitizerLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
195  AU.addRequired<TargetLibraryInfoWrapperPass>();
196}
197
198bool ThreadSanitizerLegacyPass::doInitialization(Module &M) {
199  insertModuleCtor(M);
200  TSan.emplace();
201  return true;
202}
203
204bool ThreadSanitizerLegacyPass::runOnFunction(Function &F) {
205  auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
206  TSan->sanitizeFunction(F, TLI);
207  return true;
208}
209
210FunctionPass *llvm::createThreadSanitizerLegacyPassPass() {
211  return new ThreadSanitizerLegacyPass();
212}
213
214void ThreadSanitizer::initialize(Module &M) {
215  const DataLayout &DL = M.getDataLayout();
216  IntptrTy = DL.getIntPtrType(M.getContext());
217
218  IRBuilder<> IRB(M.getContext());
219  AttributeList Attr;
220  Attr = Attr.addAttribute(M.getContext(), AttributeList::FunctionIndex,
221                           Attribute::NoUnwind);
222  // Initialize the callbacks.
223  TsanFuncEntry = M.getOrInsertFunction("__tsan_func_entry", Attr,
224                                        IRB.getVoidTy(), IRB.getInt8PtrTy());
225  TsanFuncExit =
226      M.getOrInsertFunction("__tsan_func_exit", Attr, IRB.getVoidTy());
227  TsanIgnoreBegin = M.getOrInsertFunction("__tsan_ignore_thread_begin", Attr,
228                                          IRB.getVoidTy());
229  TsanIgnoreEnd =
230      M.getOrInsertFunction("__tsan_ignore_thread_end", Attr, IRB.getVoidTy());
231  IntegerType *OrdTy = IRB.getInt32Ty();
232  for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
233    const unsigned ByteSize = 1U << i;
234    const unsigned BitSize = ByteSize * 8;
235    std::string ByteSizeStr = utostr(ByteSize);
236    std::string BitSizeStr = utostr(BitSize);
237    SmallString<32> ReadName("__tsan_read" + ByteSizeStr);
238    TsanRead[i] = M.getOrInsertFunction(ReadName, Attr, IRB.getVoidTy(),
239                                        IRB.getInt8PtrTy());
240
241    SmallString<32> WriteName("__tsan_write" + ByteSizeStr);
242    TsanWrite[i] = M.getOrInsertFunction(WriteName, Attr, IRB.getVoidTy(),
243                                         IRB.getInt8PtrTy());
244
245    SmallString<64> UnalignedReadName("__tsan_unaligned_read" + ByteSizeStr);
246    TsanUnalignedRead[i] = M.getOrInsertFunction(
247        UnalignedReadName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
248
249    SmallString<64> UnalignedWriteName("__tsan_unaligned_write" + ByteSizeStr);
250    TsanUnalignedWrite[i] = M.getOrInsertFunction(
251        UnalignedWriteName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
252
253    SmallString<64> VolatileReadName("__tsan_volatile_read" + ByteSizeStr);
254    TsanVolatileRead[i] = M.getOrInsertFunction(
255        VolatileReadName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
256
257    SmallString<64> VolatileWriteName("__tsan_volatile_write" + ByteSizeStr);
258    TsanVolatileWrite[i] = M.getOrInsertFunction(
259        VolatileWriteName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
260
261    SmallString<64> UnalignedVolatileReadName("__tsan_unaligned_volatile_read" +
262                                              ByteSizeStr);
263    TsanUnalignedVolatileRead[i] = M.getOrInsertFunction(
264        UnalignedVolatileReadName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
265
266    SmallString<64> UnalignedVolatileWriteName(
267        "__tsan_unaligned_volatile_write" + ByteSizeStr);
268    TsanUnalignedVolatileWrite[i] = M.getOrInsertFunction(
269        UnalignedVolatileWriteName, Attr, IRB.getVoidTy(), IRB.getInt8PtrTy());
270
271    Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
272    Type *PtrTy = Ty->getPointerTo();
273    SmallString<32> AtomicLoadName("__tsan_atomic" + BitSizeStr + "_load");
274    TsanAtomicLoad[i] =
275        M.getOrInsertFunction(AtomicLoadName, Attr, Ty, PtrTy, OrdTy);
276
277    SmallString<32> AtomicStoreName("__tsan_atomic" + BitSizeStr + "_store");
278    TsanAtomicStore[i] = M.getOrInsertFunction(
279        AtomicStoreName, Attr, IRB.getVoidTy(), PtrTy, Ty, OrdTy);
280
281    for (unsigned Op = AtomicRMWInst::FIRST_BINOP;
282         Op <= AtomicRMWInst::LAST_BINOP; ++Op) {
283      TsanAtomicRMW[Op][i] = nullptr;
284      const char *NamePart = nullptr;
285      if (Op == AtomicRMWInst::Xchg)
286        NamePart = "_exchange";
287      else if (Op == AtomicRMWInst::Add)
288        NamePart = "_fetch_add";
289      else if (Op == AtomicRMWInst::Sub)
290        NamePart = "_fetch_sub";
291      else if (Op == AtomicRMWInst::And)
292        NamePart = "_fetch_and";
293      else if (Op == AtomicRMWInst::Or)
294        NamePart = "_fetch_or";
295      else if (Op == AtomicRMWInst::Xor)
296        NamePart = "_fetch_xor";
297      else if (Op == AtomicRMWInst::Nand)
298        NamePart = "_fetch_nand";
299      else
300        continue;
301      SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
302      TsanAtomicRMW[Op][i] =
303          M.getOrInsertFunction(RMWName, Attr, Ty, PtrTy, Ty, OrdTy);
304    }
305
306    SmallString<32> AtomicCASName("__tsan_atomic" + BitSizeStr +
307                                  "_compare_exchange_val");
308    TsanAtomicCAS[i] = M.getOrInsertFunction(AtomicCASName, Attr, Ty, PtrTy, Ty,
309                                             Ty, OrdTy, OrdTy);
310  }
311  TsanVptrUpdate =
312      M.getOrInsertFunction("__tsan_vptr_update", Attr, IRB.getVoidTy(),
313                            IRB.getInt8PtrTy(), IRB.getInt8PtrTy());
314  TsanVptrLoad = M.getOrInsertFunction("__tsan_vptr_read", Attr,
315                                       IRB.getVoidTy(), IRB.getInt8PtrTy());
316  TsanAtomicThreadFence = M.getOrInsertFunction("__tsan_atomic_thread_fence",
317                                                Attr, IRB.getVoidTy(), OrdTy);
318  TsanAtomicSignalFence = M.getOrInsertFunction("__tsan_atomic_signal_fence",
319                                                Attr, IRB.getVoidTy(), OrdTy);
320
321  MemmoveFn =
322      M.getOrInsertFunction("memmove", Attr, IRB.getInt8PtrTy(),
323                            IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy);
324  MemcpyFn =
325      M.getOrInsertFunction("memcpy", Attr, IRB.getInt8PtrTy(),
326                            IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy);
327  MemsetFn =
328      M.getOrInsertFunction("memset", Attr, IRB.getInt8PtrTy(),
329                            IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy);
330}
331
332static bool isVtableAccess(Instruction *I) {
333  if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
334    return Tag->isTBAAVtableAccess();
335  return false;
336}
337
338// Do not instrument known races/"benign races" that come from compiler
339// instrumentatin. The user has no way of suppressing them.
340static bool shouldInstrumentReadWriteFromAddress(const Module *M, Value *Addr) {
341  // Peel off GEPs and BitCasts.
342  Addr = Addr->stripInBoundsOffsets();
343
344  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
345    if (GV->hasSection()) {
346      StringRef SectionName = GV->getSection();
347      // Check if the global is in the PGO counters section.
348      auto OF = Triple(M->getTargetTriple()).getObjectFormat();
349      if (SectionName.endswith(
350              getInstrProfSectionName(IPSK_cnts, OF, /*AddSegmentInfo=*/false)))
351        return false;
352    }
353
354    // Check if the global is private gcov data.
355    if (GV->getName().startswith("__llvm_gcov") ||
356        GV->getName().startswith("__llvm_gcda"))
357      return false;
358  }
359
360  // Do not instrument acesses from different address spaces; we cannot deal
361  // with them.
362  if (Addr) {
363    Type *PtrTy = cast<PointerType>(Addr->getType()->getScalarType());
364    if (PtrTy->getPointerAddressSpace() != 0)
365      return false;
366  }
367
368  return true;
369}
370
371bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
372  // If this is a GEP, just analyze its pointer operand.
373  if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
374    Addr = GEP->getPointerOperand();
375
376  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
377    if (GV->isConstant()) {
378      // Reads from constant globals can not race with any writes.
379      NumOmittedReadsFromConstantGlobals++;
380      return true;
381    }
382  } else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
383    if (isVtableAccess(L)) {
384      // Reads from a vtable pointer can not race with any writes.
385      NumOmittedReadsFromVtable++;
386      return true;
387    }
388  }
389  return false;
390}
391
392// Instrumenting some of the accesses may be proven redundant.
393// Currently handled:
394//  - read-before-write (within same BB, no calls between)
395//  - not captured variables
396//
397// We do not handle some of the patterns that should not survive
398// after the classic compiler optimizations.
399// E.g. two reads from the same temp should be eliminated by CSE,
400// two writes should be eliminated by DSE, etc.
401//
402// 'Local' is a vector of insns within the same BB (no calls between).
403// 'All' is a vector of insns that will be instrumented.
404void ThreadSanitizer::chooseInstructionsToInstrument(
405    SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
406    const DataLayout &DL) {
407  SmallPtrSet<Value*, 8> WriteTargets;
408  // Iterate from the end.
409  for (Instruction *I : reverse(Local)) {
410    if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
411      Value *Addr = Store->getPointerOperand();
412      if (!shouldInstrumentReadWriteFromAddress(I->getModule(), Addr))
413        continue;
414      WriteTargets.insert(Addr);
415    } else {
416      LoadInst *Load = cast<LoadInst>(I);
417      Value *Addr = Load->getPointerOperand();
418      if (!shouldInstrumentReadWriteFromAddress(I->getModule(), Addr))
419        continue;
420      if (!ClInstrumentReadBeforeWrite && WriteTargets.count(Addr)) {
421        // We will write to this temp, so no reason to analyze the read.
422        NumOmittedReadsBeforeWrite++;
423        continue;
424      }
425      if (addrPointsToConstantData(Addr)) {
426        // Addr points to some constant data -- it can not race with any writes.
427        continue;
428      }
429    }
430    Value *Addr = isa<StoreInst>(*I)
431        ? cast<StoreInst>(I)->getPointerOperand()
432        : cast<LoadInst>(I)->getPointerOperand();
433    if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
434        !PointerMayBeCaptured(Addr, true, true)) {
435      // The variable is addressable but not captured, so it cannot be
436      // referenced from a different thread and participate in a data race
437      // (see llvm/Analysis/CaptureTracking.h for details).
438      NumOmittedNonCaptured++;
439      continue;
440    }
441    All.push_back(I);
442  }
443  Local.clear();
444}
445
446static bool isAtomic(Instruction *I) {
447  // TODO: Ask TTI whether synchronization scope is between threads.
448  if (LoadInst *LI = dyn_cast<LoadInst>(I))
449    return LI->isAtomic() && LI->getSyncScopeID() != SyncScope::SingleThread;
450  if (StoreInst *SI = dyn_cast<StoreInst>(I))
451    return SI->isAtomic() && SI->getSyncScopeID() != SyncScope::SingleThread;
452  if (isa<AtomicRMWInst>(I))
453    return true;
454  if (isa<AtomicCmpXchgInst>(I))
455    return true;
456  if (isa<FenceInst>(I))
457    return true;
458  return false;
459}
460
461void ThreadSanitizer::InsertRuntimeIgnores(Function &F) {
462  IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
463  IRB.CreateCall(TsanIgnoreBegin);
464  EscapeEnumerator EE(F, "tsan_ignore_cleanup", ClHandleCxxExceptions);
465  while (IRBuilder<> *AtExit = EE.Next()) {
466    AtExit->CreateCall(TsanIgnoreEnd);
467  }
468}
469
470bool ThreadSanitizer::sanitizeFunction(Function &F,
471                                       const TargetLibraryInfo &TLI) {
472  // This is required to prevent instrumenting call to __tsan_init from within
473  // the module constructor.
474  if (F.getName() == kTsanModuleCtorName)
475    return false;
476  // Naked functions can not have prologue/epilogue
477  // (__tsan_func_entry/__tsan_func_exit) generated, so don't instrument them at
478  // all.
479  if (F.hasFnAttribute(Attribute::Naked))
480    return false;
481  initialize(*F.getParent());
482  SmallVector<Instruction*, 8> AllLoadsAndStores;
483  SmallVector<Instruction*, 8> LocalLoadsAndStores;
484  SmallVector<Instruction*, 8> AtomicAccesses;
485  SmallVector<Instruction*, 8> MemIntrinCalls;
486  bool Res = false;
487  bool HasCalls = false;
488  bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeThread);
489  const DataLayout &DL = F.getParent()->getDataLayout();
490
491  // Traverse all instructions, collect loads/stores/returns, check for calls.
492  for (auto &BB : F) {
493    for (auto &Inst : BB) {
494      if (isAtomic(&Inst))
495        AtomicAccesses.push_back(&Inst);
496      else if (isa<LoadInst>(Inst) || isa<StoreInst>(Inst))
497        LocalLoadsAndStores.push_back(&Inst);
498      else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
499        if (CallInst *CI = dyn_cast<CallInst>(&Inst))
500          maybeMarkSanitizerLibraryCallNoBuiltin(CI, &TLI);
501        if (isa<MemIntrinsic>(Inst))
502          MemIntrinCalls.push_back(&Inst);
503        HasCalls = true;
504        chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores,
505                                       DL);
506      }
507    }
508    chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores, DL);
509  }
510
511  // We have collected all loads and stores.
512  // FIXME: many of these accesses do not need to be checked for races
513  // (e.g. variables that do not escape, etc).
514
515  // Instrument memory accesses only if we want to report bugs in the function.
516  if (ClInstrumentMemoryAccesses && SanitizeFunction)
517    for (auto Inst : AllLoadsAndStores) {
518      Res |= instrumentLoadOrStore(Inst, DL);
519    }
520
521  // Instrument atomic memory accesses in any case (they can be used to
522  // implement synchronization).
523  if (ClInstrumentAtomics)
524    for (auto Inst : AtomicAccesses) {
525      Res |= instrumentAtomic(Inst, DL);
526    }
527
528  if (ClInstrumentMemIntrinsics && SanitizeFunction)
529    for (auto Inst : MemIntrinCalls) {
530      Res |= instrumentMemIntrinsic(Inst);
531    }
532
533  if (F.hasFnAttribute("sanitize_thread_no_checking_at_run_time")) {
534    assert(!F.hasFnAttribute(Attribute::SanitizeThread));
535    if (HasCalls)
536      InsertRuntimeIgnores(F);
537  }
538
539  // Instrument function entry/exit points if there were instrumented accesses.
540  if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
541    IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
542    Value *ReturnAddress = IRB.CreateCall(
543        Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
544        IRB.getInt32(0));
545    IRB.CreateCall(TsanFuncEntry, ReturnAddress);
546
547    EscapeEnumerator EE(F, "tsan_cleanup", ClHandleCxxExceptions);
548    while (IRBuilder<> *AtExit = EE.Next()) {
549      AtExit->CreateCall(TsanFuncExit, {});
550    }
551    Res = true;
552  }
553  return Res;
554}
555
556bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
557                                            const DataLayout &DL) {
558  IRBuilder<> IRB(I);
559  bool IsWrite = isa<StoreInst>(*I);
560  Value *Addr = IsWrite
561      ? cast<StoreInst>(I)->getPointerOperand()
562      : cast<LoadInst>(I)->getPointerOperand();
563
564  // swifterror memory addresses are mem2reg promoted by instruction selection.
565  // As such they cannot have regular uses like an instrumentation function and
566  // it makes no sense to track them as memory.
567  if (Addr->isSwiftError())
568    return false;
569
570  int Idx = getMemoryAccessFuncIndex(Addr, DL);
571  if (Idx < 0)
572    return false;
573  if (IsWrite && isVtableAccess(I)) {
574    LLVM_DEBUG(dbgs() << "  VPTR : " << *I << "\n");
575    Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
576    // StoredValue may be a vector type if we are storing several vptrs at once.
577    // In this case, just take the first element of the vector since this is
578    // enough to find vptr races.
579    if (isa<VectorType>(StoredValue->getType()))
580      StoredValue = IRB.CreateExtractElement(
581          StoredValue, ConstantInt::get(IRB.getInt32Ty(), 0));
582    if (StoredValue->getType()->isIntegerTy())
583      StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
584    // Call TsanVptrUpdate.
585    IRB.CreateCall(TsanVptrUpdate,
586                   {IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
587                    IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy())});
588    NumInstrumentedVtableWrites++;
589    return true;
590  }
591  if (!IsWrite && isVtableAccess(I)) {
592    IRB.CreateCall(TsanVptrLoad,
593                   IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
594    NumInstrumentedVtableReads++;
595    return true;
596  }
597  const unsigned Alignment = IsWrite
598      ? cast<StoreInst>(I)->getAlignment()
599      : cast<LoadInst>(I)->getAlignment();
600  const bool IsVolatile =
601      ClDistinguishVolatile && (IsWrite ? cast<StoreInst>(I)->isVolatile()
602                                        : cast<LoadInst>(I)->isVolatile());
603  Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
604  const uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
605  FunctionCallee OnAccessFunc = nullptr;
606  if (Alignment == 0 || Alignment >= 8 || (Alignment % (TypeSize / 8)) == 0) {
607    if (IsVolatile)
608      OnAccessFunc = IsWrite ? TsanVolatileWrite[Idx] : TsanVolatileRead[Idx];
609    else
610      OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
611  } else {
612    if (IsVolatile)
613      OnAccessFunc = IsWrite ? TsanUnalignedVolatileWrite[Idx]
614                             : TsanUnalignedVolatileRead[Idx];
615    else
616      OnAccessFunc = IsWrite ? TsanUnalignedWrite[Idx] : TsanUnalignedRead[Idx];
617  }
618  IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
619  if (IsWrite) NumInstrumentedWrites++;
620  else         NumInstrumentedReads++;
621  return true;
622}
623
624static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
625  uint32_t v = 0;
626  switch (ord) {
627    case AtomicOrdering::NotAtomic:
628      llvm_unreachable("unexpected atomic ordering!");
629    case AtomicOrdering::Unordered:              LLVM_FALLTHROUGH;
630    case AtomicOrdering::Monotonic:              v = 0; break;
631    // Not specified yet:
632    // case AtomicOrdering::Consume:                v = 1; break;
633    case AtomicOrdering::Acquire:                v = 2; break;
634    case AtomicOrdering::Release:                v = 3; break;
635    case AtomicOrdering::AcquireRelease:         v = 4; break;
636    case AtomicOrdering::SequentiallyConsistent: v = 5; break;
637  }
638  return IRB->getInt32(v);
639}
640
641// If a memset intrinsic gets inlined by the code gen, we will miss races on it.
642// So, we either need to ensure the intrinsic is not inlined, or instrument it.
643// We do not instrument memset/memmove/memcpy intrinsics (too complicated),
644// instead we simply replace them with regular function calls, which are then
645// intercepted by the run-time.
646// Since tsan is running after everyone else, the calls should not be
647// replaced back with intrinsics. If that becomes wrong at some point,
648// we will need to call e.g. __tsan_memset to avoid the intrinsics.
649bool ThreadSanitizer::instrumentMemIntrinsic(Instruction *I) {
650  IRBuilder<> IRB(I);
651  if (MemSetInst *M = dyn_cast<MemSetInst>(I)) {
652    IRB.CreateCall(
653        MemsetFn,
654        {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
655         IRB.CreateIntCast(M->getArgOperand(1), IRB.getInt32Ty(), false),
656         IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
657    I->eraseFromParent();
658  } else if (MemTransferInst *M = dyn_cast<MemTransferInst>(I)) {
659    IRB.CreateCall(
660        isa<MemCpyInst>(M) ? MemcpyFn : MemmoveFn,
661        {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
662         IRB.CreatePointerCast(M->getArgOperand(1), IRB.getInt8PtrTy()),
663         IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
664    I->eraseFromParent();
665  }
666  return false;
667}
668
669// Both llvm and ThreadSanitizer atomic operations are based on C++11/C1x
670// standards.  For background see C++11 standard.  A slightly older, publicly
671// available draft of the standard (not entirely up-to-date, but close enough
672// for casual browsing) is available here:
673// http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
674// The following page contains more background information:
675// http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/
676
677bool ThreadSanitizer::instrumentAtomic(Instruction *I, const DataLayout &DL) {
678  IRBuilder<> IRB(I);
679  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
680    Value *Addr = LI->getPointerOperand();
681    int Idx = getMemoryAccessFuncIndex(Addr, DL);
682    if (Idx < 0)
683      return false;
684    const unsigned ByteSize = 1U << Idx;
685    const unsigned BitSize = ByteSize * 8;
686    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
687    Type *PtrTy = Ty->getPointerTo();
688    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
689                     createOrdering(&IRB, LI->getOrdering())};
690    Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
691    Value *C = IRB.CreateCall(TsanAtomicLoad[Idx], Args);
692    Value *Cast = IRB.CreateBitOrPointerCast(C, OrigTy);
693    I->replaceAllUsesWith(Cast);
694  } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
695    Value *Addr = SI->getPointerOperand();
696    int Idx = getMemoryAccessFuncIndex(Addr, DL);
697    if (Idx < 0)
698      return false;
699    const unsigned ByteSize = 1U << Idx;
700    const unsigned BitSize = ByteSize * 8;
701    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
702    Type *PtrTy = Ty->getPointerTo();
703    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
704                     IRB.CreateBitOrPointerCast(SI->getValueOperand(), Ty),
705                     createOrdering(&IRB, SI->getOrdering())};
706    CallInst *C = CallInst::Create(TsanAtomicStore[Idx], Args);
707    ReplaceInstWithInst(I, C);
708  } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I)) {
709    Value *Addr = RMWI->getPointerOperand();
710    int Idx = getMemoryAccessFuncIndex(Addr, DL);
711    if (Idx < 0)
712      return false;
713    FunctionCallee F = TsanAtomicRMW[RMWI->getOperation()][Idx];
714    if (!F)
715      return false;
716    const unsigned ByteSize = 1U << Idx;
717    const unsigned BitSize = ByteSize * 8;
718    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
719    Type *PtrTy = Ty->getPointerTo();
720    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
721                     IRB.CreateIntCast(RMWI->getValOperand(), Ty, false),
722                     createOrdering(&IRB, RMWI->getOrdering())};
723    CallInst *C = CallInst::Create(F, Args);
724    ReplaceInstWithInst(I, C);
725  } else if (AtomicCmpXchgInst *CASI = dyn_cast<AtomicCmpXchgInst>(I)) {
726    Value *Addr = CASI->getPointerOperand();
727    int Idx = getMemoryAccessFuncIndex(Addr, DL);
728    if (Idx < 0)
729      return false;
730    const unsigned ByteSize = 1U << Idx;
731    const unsigned BitSize = ByteSize * 8;
732    Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
733    Type *PtrTy = Ty->getPointerTo();
734    Value *CmpOperand =
735      IRB.CreateBitOrPointerCast(CASI->getCompareOperand(), Ty);
736    Value *NewOperand =
737      IRB.CreateBitOrPointerCast(CASI->getNewValOperand(), Ty);
738    Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
739                     CmpOperand,
740                     NewOperand,
741                     createOrdering(&IRB, CASI->getSuccessOrdering()),
742                     createOrdering(&IRB, CASI->getFailureOrdering())};
743    CallInst *C = IRB.CreateCall(TsanAtomicCAS[Idx], Args);
744    Value *Success = IRB.CreateICmpEQ(C, CmpOperand);
745    Value *OldVal = C;
746    Type *OrigOldValTy = CASI->getNewValOperand()->getType();
747    if (Ty != OrigOldValTy) {
748      // The value is a pointer, so we need to cast the return value.
749      OldVal = IRB.CreateIntToPtr(C, OrigOldValTy);
750    }
751
752    Value *Res =
753      IRB.CreateInsertValue(UndefValue::get(CASI->getType()), OldVal, 0);
754    Res = IRB.CreateInsertValue(Res, Success, 1);
755
756    I->replaceAllUsesWith(Res);
757    I->eraseFromParent();
758  } else if (FenceInst *FI = dyn_cast<FenceInst>(I)) {
759    Value *Args[] = {createOrdering(&IRB, FI->getOrdering())};
760    FunctionCallee F = FI->getSyncScopeID() == SyncScope::SingleThread
761                           ? TsanAtomicSignalFence
762                           : TsanAtomicThreadFence;
763    CallInst *C = CallInst::Create(F, Args);
764    ReplaceInstWithInst(I, C);
765  }
766  return true;
767}
768
769int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr,
770                                              const DataLayout &DL) {
771  Type *OrigPtrTy = Addr->getType();
772  Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
773  assert(OrigTy->isSized());
774  uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
775  if (TypeSize != 8  && TypeSize != 16 &&
776      TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
777    NumAccessesWithBadSize++;
778    // Ignore all unusual sizes.
779    return -1;
780  }
781  size_t Idx = countTrailingZeros(TypeSize / 8);
782  assert(Idx < kNumberOfAccessSizes);
783  return Idx;
784}
785