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 #define DEBUG_TYPE "tsan"
23 
24 #include "BlackList.h"
25 #include "llvm/Function.h"
26 #include "llvm/IRBuilder.h"
27 #include "llvm/Intrinsics.h"
28 #include "llvm/LLVMContext.h"
29 #include "llvm/Metadata.h"
30 #include "llvm/Module.h"
31 #include "llvm/Type.h"
32 #include "llvm/ADT/SmallSet.h"
33 #include "llvm/ADT/SmallString.h"
34 #include "llvm/ADT/SmallVector.h"
35 #include "llvm/ADT/Statistic.h"
36 #include "llvm/ADT/StringExtras.h"
37 #include "llvm/Support/CommandLine.h"
38 #include "llvm/Support/Debug.h"
39 #include "llvm/Support/MathExtras.h"
40 #include "llvm/Support/raw_ostream.h"
41 #include "llvm/DataLayout.h"
42 #include "llvm/Transforms/Instrumentation.h"
43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
44 #include "llvm/Transforms/Utils/ModuleUtils.h"
45 
46 using namespace llvm;
47 
48 static cl::opt<std::string>  ClBlackListFile("tsan-blacklist",
49        cl::desc("Blacklist file"), cl::Hidden);
50 static cl::opt<bool>  ClInstrumentMemoryAccesses(
51     "tsan-instrument-memory-accesses", cl::init(true),
52     cl::desc("Instrument memory accesses"), cl::Hidden);
53 static cl::opt<bool>  ClInstrumentFuncEntryExit(
54     "tsan-instrument-func-entry-exit", cl::init(true),
55     cl::desc("Instrument function entry and exit"), cl::Hidden);
56 static cl::opt<bool>  ClInstrumentAtomics(
57     "tsan-instrument-atomics", cl::init(true),
58     cl::desc("Instrument atomics"), cl::Hidden);
59 
60 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
61 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
62 STATISTIC(NumOmittedReadsBeforeWrite,
63           "Number of reads ignored due to following writes");
64 STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
65 STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
66 STATISTIC(NumOmittedReadsFromConstantGlobals,
67           "Number of reads from constant globals");
68 STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
69 
70 namespace {
71 
72 /// ThreadSanitizer: instrument the code in module to find races.
73 struct ThreadSanitizer : public FunctionPass {
74   ThreadSanitizer();
75   const char *getPassName() const;
76   bool runOnFunction(Function &F);
77   bool doInitialization(Module &M);
78   static char ID;  // Pass identification, replacement for typeid.
79 
80  private:
81   bool instrumentLoadOrStore(Instruction *I);
82   bool instrumentAtomic(Instruction *I);
83   void chooseInstructionsToInstrument(SmallVectorImpl<Instruction*> &Local,
84                                       SmallVectorImpl<Instruction*> &All);
85   bool addrPointsToConstantData(Value *Addr);
86   int getMemoryAccessFuncIndex(Value *Addr);
87 
88   DataLayout *TD;
89   OwningPtr<BlackList> BL;
90   IntegerType *OrdTy;
91   // Callbacks to run-time library are computed in doInitialization.
92   Function *TsanFuncEntry;
93   Function *TsanFuncExit;
94   // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
95   static const size_t kNumberOfAccessSizes = 5;
96   Function *TsanRead[kNumberOfAccessSizes];
97   Function *TsanWrite[kNumberOfAccessSizes];
98   Function *TsanAtomicLoad[kNumberOfAccessSizes];
99   Function *TsanAtomicStore[kNumberOfAccessSizes];
100   Function *TsanVptrUpdate;
101 };
102 }  // namespace
103 
104 char ThreadSanitizer::ID = 0;
105 INITIALIZE_PASS(ThreadSanitizer, "tsan",
106     "ThreadSanitizer: detects data races.",
107     false, false)
108 
109 const char *ThreadSanitizer::getPassName() const {
110   return "ThreadSanitizer";
111 }
112 
113 ThreadSanitizer::ThreadSanitizer()
114   : FunctionPass(ID),
115   TD(NULL) {
116 }
117 
118 FunctionPass *llvm::createThreadSanitizerPass() {
119   return new ThreadSanitizer();
120 }
121 
122 static Function *checkInterfaceFunction(Constant *FuncOrBitcast) {
123   if (Function *F = dyn_cast<Function>(FuncOrBitcast))
124      return F;
125   FuncOrBitcast->dump();
126   report_fatal_error("ThreadSanitizer interface function redefined");
127 }
128 
129 bool ThreadSanitizer::doInitialization(Module &M) {
130   TD = getAnalysisIfAvailable<DataLayout>();
131   if (!TD)
132     return false;
133   BL.reset(new BlackList(ClBlackListFile));
134 
135   // Always insert a call to __tsan_init into the module's CTORs.
136   IRBuilder<> IRB(M.getContext());
137   Value *TsanInit = M.getOrInsertFunction("__tsan_init",
138                                           IRB.getVoidTy(), NULL);
139   appendToGlobalCtors(M, cast<Function>(TsanInit), 0);
140 
141   // Initialize the callbacks.
142   TsanFuncEntry = checkInterfaceFunction(M.getOrInsertFunction(
143       "__tsan_func_entry", IRB.getVoidTy(), IRB.getInt8PtrTy(), NULL));
144   TsanFuncExit = checkInterfaceFunction(M.getOrInsertFunction(
145       "__tsan_func_exit", IRB.getVoidTy(), NULL));
146   OrdTy = IRB.getInt32Ty();
147   for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
148     const size_t ByteSize = 1 << i;
149     const size_t BitSize = ByteSize * 8;
150     SmallString<32> ReadName("__tsan_read" + itostr(ByteSize));
151     TsanRead[i] = checkInterfaceFunction(M.getOrInsertFunction(
152         ReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), NULL));
153 
154     SmallString<32> WriteName("__tsan_write" + itostr(ByteSize));
155     TsanWrite[i] = checkInterfaceFunction(M.getOrInsertFunction(
156         WriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), NULL));
157 
158     Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
159     Type *PtrTy = Ty->getPointerTo();
160     SmallString<32> AtomicLoadName("__tsan_atomic" + itostr(BitSize) +
161                                    "_load");
162     TsanAtomicLoad[i] = checkInterfaceFunction(M.getOrInsertFunction(
163         AtomicLoadName, Ty, PtrTy, OrdTy, NULL));
164 
165     SmallString<32> AtomicStoreName("__tsan_atomic" + itostr(BitSize) +
166                                     "_store");
167     TsanAtomicStore[i] = checkInterfaceFunction(M.getOrInsertFunction(
168         AtomicStoreName, IRB.getVoidTy(), PtrTy, Ty, OrdTy,
169         NULL));
170   }
171   TsanVptrUpdate = checkInterfaceFunction(M.getOrInsertFunction(
172       "__tsan_vptr_update", IRB.getVoidTy(), IRB.getInt8PtrTy(),
173       IRB.getInt8PtrTy(), NULL));
174   return true;
175 }
176 
177 static bool isVtableAccess(Instruction *I) {
178   if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa)) {
179     if (Tag->getNumOperands() < 1) return false;
180     if (MDString *Tag1 = dyn_cast<MDString>(Tag->getOperand(0))) {
181       if (Tag1->getString() == "vtable pointer") return true;
182     }
183   }
184   return false;
185 }
186 
187 bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
188   // If this is a GEP, just analyze its pointer operand.
189   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
190     Addr = GEP->getPointerOperand();
191 
192   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
193     if (GV->isConstant()) {
194       // Reads from constant globals can not race with any writes.
195       NumOmittedReadsFromConstantGlobals++;
196       return true;
197     }
198   } else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
199     if (isVtableAccess(L)) {
200       // Reads from a vtable pointer can not race with any writes.
201       NumOmittedReadsFromVtable++;
202       return true;
203     }
204   }
205   return false;
206 }
207 
208 // Instrumenting some of the accesses may be proven redundant.
209 // Currently handled:
210 //  - read-before-write (within same BB, no calls between)
211 //
212 // We do not handle some of the patterns that should not survive
213 // after the classic compiler optimizations.
214 // E.g. two reads from the same temp should be eliminated by CSE,
215 // two writes should be eliminated by DSE, etc.
216 //
217 // 'Local' is a vector of insns within the same BB (no calls between).
218 // 'All' is a vector of insns that will be instrumented.
219 void ThreadSanitizer::chooseInstructionsToInstrument(
220     SmallVectorImpl<Instruction*> &Local,
221     SmallVectorImpl<Instruction*> &All) {
222   SmallSet<Value*, 8> WriteTargets;
223   // Iterate from the end.
224   for (SmallVectorImpl<Instruction*>::reverse_iterator It = Local.rbegin(),
225        E = Local.rend(); It != E; ++It) {
226     Instruction *I = *It;
227     if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
228       WriteTargets.insert(Store->getPointerOperand());
229     } else {
230       LoadInst *Load = cast<LoadInst>(I);
231       Value *Addr = Load->getPointerOperand();
232       if (WriteTargets.count(Addr)) {
233         // We will write to this temp, so no reason to analyze the read.
234         NumOmittedReadsBeforeWrite++;
235         continue;
236       }
237       if (addrPointsToConstantData(Addr)) {
238         // Addr points to some constant data -- it can not race with any writes.
239         continue;
240       }
241     }
242     All.push_back(I);
243   }
244   Local.clear();
245 }
246 
247 static bool isAtomic(Instruction *I) {
248   if (LoadInst *LI = dyn_cast<LoadInst>(I))
249     return LI->isAtomic() && LI->getSynchScope() == CrossThread;
250   if (StoreInst *SI = dyn_cast<StoreInst>(I))
251     return SI->isAtomic() && SI->getSynchScope() == CrossThread;
252   if (isa<AtomicRMWInst>(I))
253     return true;
254   if (isa<AtomicCmpXchgInst>(I))
255     return true;
256   if (FenceInst *FI = dyn_cast<FenceInst>(I))
257     return FI->getSynchScope() == CrossThread;
258   return false;
259 }
260 
261 bool ThreadSanitizer::runOnFunction(Function &F) {
262   if (!TD) return false;
263   if (BL->isIn(F)) return false;
264   SmallVector<Instruction*, 8> RetVec;
265   SmallVector<Instruction*, 8> AllLoadsAndStores;
266   SmallVector<Instruction*, 8> LocalLoadsAndStores;
267   SmallVector<Instruction*, 8> AtomicAccesses;
268   bool Res = false;
269   bool HasCalls = false;
270 
271   // Traverse all instructions, collect loads/stores/returns, check for calls.
272   for (Function::iterator FI = F.begin(), FE = F.end();
273        FI != FE; ++FI) {
274     BasicBlock &BB = *FI;
275     for (BasicBlock::iterator BI = BB.begin(), BE = BB.end();
276          BI != BE; ++BI) {
277       if (isAtomic(BI))
278         AtomicAccesses.push_back(BI);
279       else if (isa<LoadInst>(BI) || isa<StoreInst>(BI))
280         LocalLoadsAndStores.push_back(BI);
281       else if (isa<ReturnInst>(BI))
282         RetVec.push_back(BI);
283       else if (isa<CallInst>(BI) || isa<InvokeInst>(BI)) {
284         HasCalls = true;
285         chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores);
286       }
287     }
288     chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores);
289   }
290 
291   // We have collected all loads and stores.
292   // FIXME: many of these accesses do not need to be checked for races
293   // (e.g. variables that do not escape, etc).
294 
295   // Instrument memory accesses.
296   if (ClInstrumentMemoryAccesses)
297     for (size_t i = 0, n = AllLoadsAndStores.size(); i < n; ++i) {
298       Res |= instrumentLoadOrStore(AllLoadsAndStores[i]);
299     }
300 
301   // Instrument atomic memory accesses.
302   if (ClInstrumentAtomics)
303     for (size_t i = 0, n = AtomicAccesses.size(); i < n; ++i) {
304       Res |= instrumentAtomic(AtomicAccesses[i]);
305     }
306 
307   // Instrument function entry/exit points if there were instrumented accesses.
308   if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
309     IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
310     Value *ReturnAddress = IRB.CreateCall(
311         Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
312         IRB.getInt32(0));
313     IRB.CreateCall(TsanFuncEntry, ReturnAddress);
314     for (size_t i = 0, n = RetVec.size(); i < n; ++i) {
315       IRBuilder<> IRBRet(RetVec[i]);
316       IRBRet.CreateCall(TsanFuncExit);
317     }
318     Res = true;
319   }
320   return Res;
321 }
322 
323 bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I) {
324   IRBuilder<> IRB(I);
325   bool IsWrite = isa<StoreInst>(*I);
326   Value *Addr = IsWrite
327       ? cast<StoreInst>(I)->getPointerOperand()
328       : cast<LoadInst>(I)->getPointerOperand();
329   int Idx = getMemoryAccessFuncIndex(Addr);
330   if (Idx < 0)
331     return false;
332   if (IsWrite && isVtableAccess(I)) {
333     DEBUG(dbgs() << "  VPTR : " << *I << "\n");
334     Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
335     // StoredValue does not necessary have a pointer type.
336     if (isa<IntegerType>(StoredValue->getType()))
337       StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
338     // Call TsanVptrUpdate.
339     IRB.CreateCall2(TsanVptrUpdate,
340                     IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
341                     IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy()));
342     NumInstrumentedVtableWrites++;
343     return true;
344   }
345   Value *OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
346   IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
347   if (IsWrite) NumInstrumentedWrites++;
348   else         NumInstrumentedReads++;
349   return true;
350 }
351 
352 static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
353   uint32_t v = 0;
354   switch (ord) {
355     case NotAtomic:              assert(false);
356     case Unordered:              // Fall-through.
357     case Monotonic:              v = 1 << 0; break;
358     // case Consume:                v = 1 << 1; break;  // Not specified yet.
359     case Acquire:                v = 1 << 2; break;
360     case Release:                v = 1 << 3; break;
361     case AcquireRelease:         v = 1 << 4; break;
362     case SequentiallyConsistent: v = 1 << 5; break;
363   }
364   // +100500 is temporal to migrate to new enum values.
365   return IRB->getInt32(v + 100500);
366 }
367 
368 bool ThreadSanitizer::instrumentAtomic(Instruction *I) {
369   IRBuilder<> IRB(I);
370   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
371     Value *Addr = LI->getPointerOperand();
372     int Idx = getMemoryAccessFuncIndex(Addr);
373     if (Idx < 0)
374       return false;
375     const size_t ByteSize = 1 << Idx;
376     const size_t BitSize = ByteSize * 8;
377     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
378     Type *PtrTy = Ty->getPointerTo();
379     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
380                      createOrdering(&IRB, LI->getOrdering())};
381     CallInst *C = CallInst::Create(TsanAtomicLoad[Idx],
382                                    ArrayRef<Value*>(Args));
383     ReplaceInstWithInst(I, C);
384 
385   } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
386     Value *Addr = SI->getPointerOperand();
387     int Idx = getMemoryAccessFuncIndex(Addr);
388     if (Idx < 0)
389       return false;
390     const size_t ByteSize = 1 << Idx;
391     const size_t BitSize = ByteSize * 8;
392     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
393     Type *PtrTy = Ty->getPointerTo();
394     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
395                      IRB.CreateIntCast(SI->getValueOperand(), Ty, false),
396                      createOrdering(&IRB, SI->getOrdering())};
397     CallInst *C = CallInst::Create(TsanAtomicStore[Idx],
398                                    ArrayRef<Value*>(Args));
399     ReplaceInstWithInst(I, C);
400   } else if (isa<AtomicRMWInst>(I)) {
401     // FIXME: Not yet supported.
402   } else if (isa<AtomicCmpXchgInst>(I)) {
403     // FIXME: Not yet supported.
404   } else if (isa<FenceInst>(I)) {
405     // FIXME: Not yet supported.
406   }
407   return true;
408 }
409 
410 int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr) {
411   Type *OrigPtrTy = Addr->getType();
412   Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
413   assert(OrigTy->isSized());
414   uint32_t TypeSize = TD->getTypeStoreSizeInBits(OrigTy);
415   if (TypeSize != 8  && TypeSize != 16 &&
416       TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
417     NumAccessesWithBadSize++;
418     // Ignore all unusual sizes.
419     return -1;
420   }
421   size_t Idx = CountTrailingZeros_32(TypeSize / 8);
422   assert(Idx < kNumberOfAccessSizes);
423   return Idx;
424 }
425