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