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