1 //===-- SanitizerCoverage.cpp - coverage instrumentation for sanitizers ---===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Coverage instrumentation that works with AddressSanitizer
11 // and potentially with other Sanitizers.
13 // We create a Guard variable with the same linkage
14 // as the function and inject this code into the entry block (SCK_Function)
15 // or all blocks (SCK_BB):
17 // __sanitizer_cov(&Guard);
19 // The accesses to Guard are atomic. The rest of the logic is
20 // in __sanitizer_cov (it's fine to call it more than once).
22 // With SCK_Edge we also split critical edges this effectively
23 // instrumenting all edges.
25 // This coverage implementation provides very limited data:
26 // it only tells if a given function (block) was ever executed. No counters.
27 // But for many use cases this is what we need and the added slowdown small.
29 //===----------------------------------------------------------------------===//
31 #include "llvm/Transforms/Instrumentation.h"
32 #include "llvm/ADT/ArrayRef.h"
33 #include "llvm/ADT/SmallVector.h"
34 #include "llvm/Analysis/LibCallSemantics.h"
35 #include "llvm/IR/CallSite.h"
36 #include "llvm/IR/DataLayout.h"
37 #include "llvm/IR/DebugInfo.h"
38 #include "llvm/IR/Function.h"
39 #include "llvm/IR/IRBuilder.h"
40 #include "llvm/IR/InlineAsm.h"
41 #include "llvm/IR/LLVMContext.h"
42 #include "llvm/IR/MDBuilder.h"
43 #include "llvm/IR/Module.h"
44 #include "llvm/IR/Type.h"
45 #include "llvm/Support/CommandLine.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include "llvm/Transforms/Scalar.h"
49 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
50 #include "llvm/Transforms/Utils/ModuleUtils.h"
54 #define DEBUG_TYPE "sancov"
56 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init";
57 static const char *const kSanCovName = "__sanitizer_cov";
58 static const char *const kSanCovWithCheckName = "__sanitizer_cov_with_check";
59 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16";
60 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter";
61 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block";
62 static const char *const kSanCovTraceCmp = "__sanitizer_cov_trace_cmp";
63 static const char *const kSanCovTraceSwitch = "__sanitizer_cov_trace_switch";
64 static const char *const kSanCovModuleCtorName = "sancov.module_ctor";
65 static const uint64_t kSanCtorAndDtorPriority = 2;
67 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level",
68 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
69 "3: all blocks and critical edges, "
70 "4: above plus indirect calls"),
71 cl::Hidden, cl::init(0));
73 static cl::opt<unsigned> ClCoverageBlockThreshold(
74 "sanitizer-coverage-block-threshold",
75 cl::desc("Use a callback with a guard check inside it if there are"
76 " more than this number of blocks."),
77 cl::Hidden, cl::init(500));
80 ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
81 cl::desc("Experimental basic-block tracing: insert "
82 "callbacks at every basic block"),
83 cl::Hidden, cl::init(false));
86 ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
87 cl::desc("Experimental tracing of CMP and similar "
89 cl::Hidden, cl::init(false));
91 // Experimental 8-bit counters used as an additional search heuristic during
92 // coverage-guided fuzzing.
93 // The counters are not thread-friendly:
94 // - contention on these counters may cause significant slowdown;
95 // - the counter updates are racy and the results may be inaccurate.
96 // They are also inaccurate due to 8-bit integer overflow.
97 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
98 cl::desc("Experimental 8-bit counters"),
99 cl::Hidden, cl::init(false));
103 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
104 SanitizerCoverageOptions Res;
105 switch (LegacyCoverageLevel) {
107 Res.CoverageType = SanitizerCoverageOptions::SCK_None;
110 Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
113 Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
116 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
119 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
120 Res.IndirectCalls = true;
126 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
127 // Sets CoverageType and IndirectCalls.
128 SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
129 Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
130 Options.IndirectCalls |= CLOpts.IndirectCalls;
131 Options.TraceBB |= ClExperimentalTracing;
132 Options.TraceCmp |= ClExperimentalCMPTracing;
133 Options.Use8bitCounters |= ClUse8bitCounters;
137 class SanitizerCoverageModule : public ModulePass {
139 SanitizerCoverageModule(
140 const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
141 : ModulePass(ID), Options(OverrideFromCL(Options)) {}
142 bool runOnModule(Module &M) override;
143 bool runOnFunction(Function &F);
144 static char ID; // Pass identification, replacement for typeid
145 const char *getPassName() const override {
146 return "SanitizerCoverageModule";
150 void InjectCoverageForIndirectCalls(Function &F,
151 ArrayRef<Instruction *> IndirCalls);
152 void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
153 void InjectTraceForSwitch(Function &F,
154 ArrayRef<Instruction *> SwitchTraceTargets);
155 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
156 void SetNoSanitizeMetadata(Instruction *I);
157 void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
158 unsigned NumberOfInstrumentedBlocks() {
159 return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses();
161 Function *SanCovFunction;
162 Function *SanCovWithCheckFunction;
163 Function *SanCovIndirCallFunction;
164 Function *SanCovTraceEnter, *SanCovTraceBB;
165 Function *SanCovTraceCmpFunction;
166 Function *SanCovTraceSwitchFunction;
168 Type *IntptrTy, *Int64Ty, *Int64PtrTy;
171 const DataLayout *DL;
173 GlobalVariable *GuardArray;
174 GlobalVariable *EightBitCounterArray;
176 SanitizerCoverageOptions Options;
181 bool SanitizerCoverageModule::runOnModule(Module &M) {
182 if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
184 C = &(M.getContext());
185 DL = &M.getDataLayout();
187 IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
188 Type *VoidTy = Type::getVoidTy(*C);
190 Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
191 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
192 Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
193 Int64Ty = IRB.getInt64Ty();
195 SanCovFunction = checkSanitizerInterfaceFunction(
196 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
197 SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
198 M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
199 SanCovIndirCallFunction =
200 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
201 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
202 SanCovTraceCmpFunction =
203 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
204 kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
205 SanCovTraceSwitchFunction =
206 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
207 kSanCovTraceSwitch, VoidTy, Int64Ty, Int64PtrTy, nullptr));
209 // We insert an empty inline asm after cov callbacks to avoid callback merge.
210 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
211 StringRef(""), StringRef(""),
212 /*hasSideEffects=*/true);
214 if (Options.TraceBB) {
215 SanCovTraceEnter = checkSanitizerInterfaceFunction(
216 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
217 SanCovTraceBB = checkSanitizerInterfaceFunction(
218 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
221 // At this point we create a dummy array of guards because we don't
222 // know how many elements we will need.
223 Type *Int32Ty = IRB.getInt32Ty();
224 Type *Int8Ty = IRB.getInt8Ty();
227 new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
228 nullptr, "__sancov_gen_cov_tmp");
229 if (Options.Use8bitCounters)
230 EightBitCounterArray =
231 new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
232 nullptr, "__sancov_gen_cov_tmp");
237 auto N = NumberOfInstrumentedBlocks();
239 // Now we know how many elements we need. Create an array of guards
240 // with one extra element at the beginning for the size.
241 Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
242 GlobalVariable *RealGuardArray = new GlobalVariable(
243 M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
244 Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
247 // Replace the dummy array with the real one.
248 GuardArray->replaceAllUsesWith(
249 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
250 GuardArray->eraseFromParent();
252 GlobalVariable *RealEightBitCounterArray;
253 if (Options.Use8bitCounters) {
254 // Make sure the array is 16-aligned.
255 static const int kCounterAlignment = 16;
257 ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
258 RealEightBitCounterArray = new GlobalVariable(
259 M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
260 Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
261 RealEightBitCounterArray->setAlignment(kCounterAlignment);
262 EightBitCounterArray->replaceAllUsesWith(
263 IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
264 EightBitCounterArray->eraseFromParent();
267 // Create variable for module (compilation unit) name
268 Constant *ModNameStrConst =
269 ConstantDataArray::getString(M.getContext(), M.getName(), true);
270 GlobalVariable *ModuleName =
271 new GlobalVariable(M, ModNameStrConst->getType(), true,
272 GlobalValue::PrivateLinkage, ModNameStrConst);
275 std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
276 M, kSanCovModuleCtorName, kSanCovModuleInitName,
277 {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
278 {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
279 ConstantInt::get(IntptrTy, N),
280 Options.Use8bitCounters
281 ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
282 : Constant::getNullValue(Int8PtrTy),
283 IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
285 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
290 bool SanitizerCoverageModule::runOnFunction(Function &F) {
291 if (F.empty()) return false;
292 if (F.getName().find(".module_ctor") != std::string::npos)
293 return false; // Should not instrument sanitizer init functions.
294 // Don't instrument functions using SEH for now. Splitting basic blocks like
295 // we do for coverage breaks WinEHPrepare.
296 // FIXME: Remove this when SEH no longer uses landingpad pattern matching.
297 if (F.hasPersonalityFn() &&
298 isAsynchronousEHPersonality(classifyEHPersonality(F.getPersonalityFn())))
300 if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
301 SplitAllCriticalEdges(F);
302 SmallVector<Instruction*, 8> IndirCalls;
303 SmallVector<BasicBlock*, 16> AllBlocks;
304 SmallVector<Instruction*, 8> CmpTraceTargets;
305 SmallVector<Instruction*, 8> SwitchTraceTargets;
307 AllBlocks.push_back(&BB);
308 for (auto &Inst : BB) {
309 if (Options.IndirectCalls) {
311 if (CS && !CS.getCalledFunction())
312 IndirCalls.push_back(&Inst);
314 if (Options.TraceCmp) {
315 if (isa<ICmpInst>(&Inst))
316 CmpTraceTargets.push_back(&Inst);
317 if (isa<SwitchInst>(&Inst))
318 SwitchTraceTargets.push_back(&Inst);
322 InjectCoverage(F, AllBlocks);
323 InjectCoverageForIndirectCalls(F, IndirCalls);
324 InjectTraceForCmp(F, CmpTraceTargets);
325 InjectTraceForSwitch(F, SwitchTraceTargets);
329 bool SanitizerCoverageModule::InjectCoverage(Function &F,
330 ArrayRef<BasicBlock *> AllBlocks) {
331 switch (Options.CoverageType) {
332 case SanitizerCoverageOptions::SCK_None:
334 case SanitizerCoverageOptions::SCK_Function:
335 InjectCoverageAtBlock(F, F.getEntryBlock(), false);
338 bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
339 for (auto BB : AllBlocks)
340 InjectCoverageAtBlock(F, *BB, UseCalls);
346 // On every indirect call we call a run-time function
347 // __sanitizer_cov_indir_call* with two parameters:
349 // - global cache array that contains kCacheSize pointers (zero-initialized).
350 // The cache is used to speed up recording the caller-callee pairs.
351 // The address of the caller is passed implicitly via caller PC.
352 // kCacheSize is encoded in the name of the run-time function.
353 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
354 Function &F, ArrayRef<Instruction *> IndirCalls) {
355 if (IndirCalls.empty()) return;
356 const int kCacheSize = 16;
357 const int kCacheAlignment = 64; // Align for better performance.
358 Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
359 for (auto I : IndirCalls) {
362 Value *Callee = CS.getCalledValue();
363 if (isa<InlineAsm>(Callee)) continue;
364 GlobalVariable *CalleeCache = new GlobalVariable(
365 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
366 Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
367 CalleeCache->setAlignment(kCacheAlignment);
368 IRB.CreateCall(SanCovIndirCallFunction,
369 {IRB.CreatePointerCast(Callee, IntptrTy),
370 IRB.CreatePointerCast(CalleeCache, IntptrTy)});
374 // For every switch statement we insert a call:
375 // __sanitizer_cov_trace_switch(CondValue,
376 // {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
378 void SanitizerCoverageModule::InjectTraceForSwitch(
379 Function &F, ArrayRef<Instruction *> SwitchTraceTargets) {
380 for (auto I : SwitchTraceTargets) {
381 if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
383 SmallVector<Constant *, 16> Initializers;
384 Value *Cond = SI->getCondition();
385 if (Cond->getType()->getScalarSizeInBits() >
386 Int64Ty->getScalarSizeInBits())
388 Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
389 Initializers.push_back(
390 ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
391 if (Cond->getType()->getScalarSizeInBits() <
392 Int64Ty->getScalarSizeInBits())
393 Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
394 for (auto It: SI->cases()) {
395 Constant *C = It.getCaseValue();
396 if (C->getType()->getScalarSizeInBits() <
397 Int64Ty->getScalarSizeInBits())
398 C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
399 Initializers.push_back(C);
401 ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
402 GlobalVariable *GV = new GlobalVariable(
403 *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
404 ConstantArray::get(ArrayOfInt64Ty, Initializers),
405 "__sancov_gen_cov_switch_values");
406 IRB.CreateCall(SanCovTraceSwitchFunction,
407 {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
413 void SanitizerCoverageModule::InjectTraceForCmp(
414 Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
415 for (auto I : CmpTraceTargets) {
416 if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
417 IRBuilder<> IRB(ICMP);
418 Value *A0 = ICMP->getOperand(0);
419 Value *A1 = ICMP->getOperand(1);
420 if (!A0->getType()->isIntegerTy()) continue;
421 uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
422 // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
424 SanCovTraceCmpFunction,
425 {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
426 IRB.CreateIntCast(A0, Int64Ty, true),
427 IRB.CreateIntCast(A1, Int64Ty, true)});
432 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
434 I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
435 MDNode::get(*C, None));
438 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
440 // Don't insert coverage for unreachable blocks: we will never call
441 // __sanitizer_cov() for them, so counting them in
442 // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
443 // percentage. Also, unreachable instructions frequently have no debug
445 if (isa<UnreachableInst>(BB.getTerminator()))
447 BasicBlock::iterator IP = BB.getFirstInsertionPt();
449 bool IsEntryBB = &BB == &F.getEntryBlock();
452 if (auto SP = getDISubprogram(&F))
453 EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
454 // Keep static allocas and llvm.localescape calls in the entry block. Even
455 // if we aren't splitting the block, it's nice for allocas to be before
457 IP = PrepareToSplitEntryBlock(BB, IP);
459 EntryLoc = IP->getDebugLoc();
462 IRBuilder<> IRB(&*IP);
463 IRB.SetCurrentDebugLocation(EntryLoc);
464 Value *GuardP = IRB.CreateAdd(
465 IRB.CreatePointerCast(GuardArray, IntptrTy),
466 ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
467 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
468 GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
470 IRB.CreateCall(SanCovWithCheckFunction, GuardP);
472 LoadInst *Load = IRB.CreateLoad(GuardP);
473 Load->setAtomic(Monotonic);
474 Load->setAlignment(4);
475 SetNoSanitizeMetadata(Load);
476 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
477 Instruction *Ins = SplitBlockAndInsertIfThen(
478 Cmp, &*IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
479 IRB.SetInsertPoint(Ins);
480 IRB.SetCurrentDebugLocation(EntryLoc);
481 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
482 IRB.CreateCall(SanCovFunction, GuardP);
483 IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
486 if (Options.Use8bitCounters) {
487 IRB.SetInsertPoint(&*IP);
488 Value *P = IRB.CreateAdd(
489 IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
490 ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
491 P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
492 LoadInst *LI = IRB.CreateLoad(P);
493 Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
494 StoreInst *SI = IRB.CreateStore(Inc, P);
495 SetNoSanitizeMetadata(LI);
496 SetNoSanitizeMetadata(SI);
499 if (Options.TraceBB) {
500 // Experimental support for tracing.
501 // Insert a callback with the same guard variable as used for coverage.
502 IRB.SetInsertPoint(&*IP);
503 IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
507 char SanitizerCoverageModule::ID = 0;
508 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
509 "SanitizerCoverage: TODO."
510 "ModulePass", false, false)
511 ModulePass *llvm::createSanitizerCoverageModulePass(
512 const SanitizerCoverageOptions &Options) {
513 return new SanitizerCoverageModule(Options);