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/IR/CallSite.h"
35 #include "llvm/IR/DataLayout.h"
36 #include "llvm/IR/DebugInfo.h"
37 #include "llvm/IR/Function.h"
38 #include "llvm/IR/IRBuilder.h"
39 #include "llvm/IR/InlineAsm.h"
40 #include "llvm/IR/LLVMContext.h"
41 #include "llvm/IR/MDBuilder.h"
42 #include "llvm/IR/Module.h"
43 #include "llvm/IR/Type.h"
44 #include "llvm/Support/CommandLine.h"
45 #include "llvm/Support/Debug.h"
46 #include "llvm/Support/raw_ostream.h"
47 #include "llvm/Transforms/Scalar.h"
48 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
49 #include "llvm/Transforms/Utils/ModuleUtils.h"
53 #define DEBUG_TYPE "sancov"
55 static const char *const kSanCovModuleInitName = "__sanitizer_cov_module_init";
56 static const char *const kSanCovName = "__sanitizer_cov";
57 static const char *const kSanCovWithCheckName = "__sanitizer_cov_with_check";
58 static const char *const kSanCovIndirCallName = "__sanitizer_cov_indir_call16";
59 static const char *const kSanCovTraceEnter = "__sanitizer_cov_trace_func_enter";
60 static const char *const kSanCovTraceBB = "__sanitizer_cov_trace_basic_block";
61 static const char *const kSanCovTraceCmp = "__sanitizer_cov_trace_cmp";
62 static const char *const kSanCovTraceSwitch = "__sanitizer_cov_trace_switch";
63 static const char *const kSanCovModuleCtorName = "sancov.module_ctor";
64 static const uint64_t kSanCtorAndDtorPriority = 2;
66 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level",
67 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
68 "3: all blocks and critical edges, "
69 "4: above plus indirect calls"),
70 cl::Hidden, cl::init(0));
72 static cl::opt<unsigned> ClCoverageBlockThreshold(
73 "sanitizer-coverage-block-threshold",
74 cl::desc("Use a callback with a guard check inside it if there are"
75 " more than this number of blocks."),
76 cl::Hidden, cl::init(500));
79 ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
80 cl::desc("Experimental basic-block tracing: insert "
81 "callbacks at every basic block"),
82 cl::Hidden, cl::init(false));
85 ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
86 cl::desc("Experimental tracing of CMP and similar "
88 cl::Hidden, cl::init(false));
90 // Experimental 8-bit counters used as an additional search heuristic during
91 // coverage-guided fuzzing.
92 // The counters are not thread-friendly:
93 // - contention on these counters may cause significant slowdown;
94 // - the counter updates are racy and the results may be inaccurate.
95 // They are also inaccurate due to 8-bit integer overflow.
96 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
97 cl::desc("Experimental 8-bit counters"),
98 cl::Hidden, cl::init(false));
102 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
103 SanitizerCoverageOptions Res;
104 switch (LegacyCoverageLevel) {
106 Res.CoverageType = SanitizerCoverageOptions::SCK_None;
109 Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
112 Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
115 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
118 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
119 Res.IndirectCalls = true;
125 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
126 // Sets CoverageType and IndirectCalls.
127 SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
128 Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
129 Options.IndirectCalls |= CLOpts.IndirectCalls;
130 Options.TraceBB |= ClExperimentalTracing;
131 Options.TraceCmp |= ClExperimentalCMPTracing;
132 Options.Use8bitCounters |= ClUse8bitCounters;
136 class SanitizerCoverageModule : public ModulePass {
138 SanitizerCoverageModule(
139 const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
140 : ModulePass(ID), Options(OverrideFromCL(Options)) {}
141 bool runOnModule(Module &M) override;
142 bool runOnFunction(Function &F);
143 static char ID; // Pass identification, replacement for typeid
144 const char *getPassName() const override {
145 return "SanitizerCoverageModule";
149 void InjectCoverageForIndirectCalls(Function &F,
150 ArrayRef<Instruction *> IndirCalls);
151 void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
152 void InjectTraceForSwitch(Function &F,
153 ArrayRef<Instruction *> SwitchTraceTargets);
154 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
155 void SetNoSanitizeMetadata(Instruction *I);
156 void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
157 unsigned NumberOfInstrumentedBlocks() {
158 return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses();
160 Function *SanCovFunction;
161 Function *SanCovWithCheckFunction;
162 Function *SanCovIndirCallFunction;
163 Function *SanCovTraceEnter, *SanCovTraceBB;
164 Function *SanCovTraceCmpFunction;
165 Function *SanCovTraceSwitchFunction;
167 Type *IntptrTy, *Int64Ty, *Int64PtrTy;
170 const DataLayout *DL;
172 GlobalVariable *GuardArray;
173 GlobalVariable *EightBitCounterArray;
175 SanitizerCoverageOptions Options;
180 bool SanitizerCoverageModule::runOnModule(Module &M) {
181 if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
183 C = &(M.getContext());
184 DL = &M.getDataLayout();
186 IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
187 Type *VoidTy = Type::getVoidTy(*C);
189 Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
190 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
191 Int64PtrTy = PointerType::getUnqual(IRB.getInt64Ty());
192 Int64Ty = IRB.getInt64Ty();
194 SanCovFunction = checkSanitizerInterfaceFunction(
195 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
196 SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
197 M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
198 SanCovIndirCallFunction =
199 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
200 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
201 SanCovTraceCmpFunction =
202 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
203 kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
204 SanCovTraceSwitchFunction =
205 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
206 kSanCovTraceSwitch, VoidTy, Int64Ty, Int64PtrTy, nullptr));
208 // We insert an empty inline asm after cov callbacks to avoid callback merge.
209 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
210 StringRef(""), StringRef(""),
211 /*hasSideEffects=*/true);
213 if (Options.TraceBB) {
214 SanCovTraceEnter = checkSanitizerInterfaceFunction(
215 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
216 SanCovTraceBB = checkSanitizerInterfaceFunction(
217 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
220 // At this point we create a dummy array of guards because we don't
221 // know how many elements we will need.
222 Type *Int32Ty = IRB.getInt32Ty();
223 Type *Int8Ty = IRB.getInt8Ty();
226 new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
227 nullptr, "__sancov_gen_cov_tmp");
228 if (Options.Use8bitCounters)
229 EightBitCounterArray =
230 new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
231 nullptr, "__sancov_gen_cov_tmp");
236 auto N = NumberOfInstrumentedBlocks();
238 // Now we know how many elements we need. Create an array of guards
239 // with one extra element at the beginning for the size.
240 Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
241 GlobalVariable *RealGuardArray = new GlobalVariable(
242 M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
243 Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
246 // Replace the dummy array with the real one.
247 GuardArray->replaceAllUsesWith(
248 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
249 GuardArray->eraseFromParent();
251 GlobalVariable *RealEightBitCounterArray;
252 if (Options.Use8bitCounters) {
253 // Make sure the array is 16-aligned.
254 static const int kCounterAlignment = 16;
256 ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
257 RealEightBitCounterArray = new GlobalVariable(
258 M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
259 Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
260 RealEightBitCounterArray->setAlignment(kCounterAlignment);
261 EightBitCounterArray->replaceAllUsesWith(
262 IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
263 EightBitCounterArray->eraseFromParent();
266 // Create variable for module (compilation unit) name
267 Constant *ModNameStrConst =
268 ConstantDataArray::getString(M.getContext(), M.getName(), true);
269 GlobalVariable *ModuleName =
270 new GlobalVariable(M, ModNameStrConst->getType(), true,
271 GlobalValue::PrivateLinkage, ModNameStrConst);
274 std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
275 M, kSanCovModuleCtorName, kSanCovModuleInitName,
276 {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
277 {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
278 ConstantInt::get(IntptrTy, N),
279 Options.Use8bitCounters
280 ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
281 : Constant::getNullValue(Int8PtrTy),
282 IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
284 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
289 bool SanitizerCoverageModule::runOnFunction(Function &F) {
290 if (F.empty()) return false;
291 if (F.getName().find(".module_ctor") != std::string::npos)
292 return false; // Should not instrument sanitizer init functions.
293 if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
294 SplitAllCriticalEdges(F);
295 SmallVector<Instruction*, 8> IndirCalls;
296 SmallVector<BasicBlock*, 16> AllBlocks;
297 SmallVector<Instruction*, 8> CmpTraceTargets;
298 SmallVector<Instruction*, 8> SwitchTraceTargets;
300 AllBlocks.push_back(&BB);
301 for (auto &Inst : BB) {
302 if (Options.IndirectCalls) {
304 if (CS && !CS.getCalledFunction())
305 IndirCalls.push_back(&Inst);
307 if (Options.TraceCmp) {
308 if (isa<ICmpInst>(&Inst))
309 CmpTraceTargets.push_back(&Inst);
310 if (isa<SwitchInst>(&Inst))
311 SwitchTraceTargets.push_back(&Inst);
315 InjectCoverage(F, AllBlocks);
316 InjectCoverageForIndirectCalls(F, IndirCalls);
317 InjectTraceForCmp(F, CmpTraceTargets);
318 InjectTraceForSwitch(F, SwitchTraceTargets);
322 bool SanitizerCoverageModule::InjectCoverage(Function &F,
323 ArrayRef<BasicBlock *> AllBlocks) {
324 switch (Options.CoverageType) {
325 case SanitizerCoverageOptions::SCK_None:
327 case SanitizerCoverageOptions::SCK_Function:
328 InjectCoverageAtBlock(F, F.getEntryBlock(), false);
331 bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
332 for (auto BB : AllBlocks)
333 InjectCoverageAtBlock(F, *BB, UseCalls);
339 // On every indirect call we call a run-time function
340 // __sanitizer_cov_indir_call* with two parameters:
342 // - global cache array that contains kCacheSize pointers (zero-initialized).
343 // The cache is used to speed up recording the caller-callee pairs.
344 // The address of the caller is passed implicitly via caller PC.
345 // kCacheSize is encoded in the name of the run-time function.
346 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
347 Function &F, ArrayRef<Instruction *> IndirCalls) {
348 if (IndirCalls.empty()) return;
349 const int kCacheSize = 16;
350 const int kCacheAlignment = 64; // Align for better performance.
351 Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
352 for (auto I : IndirCalls) {
355 Value *Callee = CS.getCalledValue();
356 if (isa<InlineAsm>(Callee)) continue;
357 GlobalVariable *CalleeCache = new GlobalVariable(
358 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
359 Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
360 CalleeCache->setAlignment(kCacheAlignment);
361 IRB.CreateCall(SanCovIndirCallFunction,
362 {IRB.CreatePointerCast(Callee, IntptrTy),
363 IRB.CreatePointerCast(CalleeCache, IntptrTy)});
367 // For every switch statement we insert a call:
368 // __sanitizer_cov_trace_switch(CondValue,
369 // {NumCases, ValueSizeInBits, Case0Value, Case1Value, Case2Value, ... })
371 void SanitizerCoverageModule::InjectTraceForSwitch(
372 Function &F, ArrayRef<Instruction *> SwitchTraceTargets) {
373 for (auto I : SwitchTraceTargets) {
374 if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
376 SmallVector<Constant *, 16> Initializers;
377 Value *Cond = SI->getCondition();
378 Initializers.push_back(ConstantInt::get(Int64Ty, SI->getNumCases()));
379 Initializers.push_back(
380 ConstantInt::get(Int64Ty, Cond->getType()->getScalarSizeInBits()));
381 if (Cond->getType()->getScalarSizeInBits() <
382 Int64Ty->getScalarSizeInBits())
383 Cond = IRB.CreateIntCast(Cond, Int64Ty, false);
384 for (auto It: SI->cases()) {
385 Constant *C = It.getCaseValue();
386 if (C->getType()->getScalarSizeInBits() <
387 Int64Ty->getScalarSizeInBits())
388 C = ConstantExpr::getCast(CastInst::ZExt, It.getCaseValue(), Int64Ty);
389 Initializers.push_back(C);
391 ArrayType *ArrayOfInt64Ty = ArrayType::get(Int64Ty, Initializers.size());
392 GlobalVariable *GV = new GlobalVariable(
393 *CurModule, ArrayOfInt64Ty, false, GlobalVariable::InternalLinkage,
394 ConstantArray::get(ArrayOfInt64Ty, Initializers),
395 "__sancov_gen_cov_switch_values");
396 IRB.CreateCall(SanCovTraceSwitchFunction,
397 {Cond, IRB.CreatePointerCast(GV, Int64PtrTy)});
403 void SanitizerCoverageModule::InjectTraceForCmp(
404 Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
405 for (auto I : CmpTraceTargets) {
406 if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
407 IRBuilder<> IRB(ICMP);
408 Value *A0 = ICMP->getOperand(0);
409 Value *A1 = ICMP->getOperand(1);
410 if (!A0->getType()->isIntegerTy()) continue;
411 uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
412 // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
414 SanCovTraceCmpFunction,
415 {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
416 IRB.CreateIntCast(A0, Int64Ty, true),
417 IRB.CreateIntCast(A1, Int64Ty, true)});
422 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
424 I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
425 MDNode::get(*C, None));
428 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
430 // Don't insert coverage for unreachable blocks: we will never call
431 // __sanitizer_cov() for them, so counting them in
432 // NumberOfInstrumentedBlocks() might complicate calculation of code coverage
433 // percentage. Also, unreachable instructions frequently have no debug
435 if (isa<UnreachableInst>(BB.getTerminator()))
437 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
438 // Skip static allocas at the top of the entry block so they don't become
439 // dynamic when we split the block. If we used our optimized stack layout,
440 // then there will only be one alloca and it will come first.
441 for (; IP != BE; ++IP) {
442 AllocaInst *AI = dyn_cast<AllocaInst>(IP);
443 if (!AI || !AI->isStaticAlloca())
447 bool IsEntryBB = &BB == &F.getEntryBlock();
450 if (auto SP = getDISubprogram(&F))
451 EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
453 EntryLoc = IP->getDebugLoc();
457 IRB.SetCurrentDebugLocation(EntryLoc);
458 Value *GuardP = IRB.CreateAdd(
459 IRB.CreatePointerCast(GuardArray, IntptrTy),
460 ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
461 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
462 GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
464 IRB.CreateCall(SanCovWithCheckFunction, GuardP);
466 LoadInst *Load = IRB.CreateLoad(GuardP);
467 Load->setAtomic(Monotonic);
468 Load->setAlignment(4);
469 SetNoSanitizeMetadata(Load);
470 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
471 Instruction *Ins = SplitBlockAndInsertIfThen(
472 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
473 IRB.SetInsertPoint(Ins);
474 IRB.SetCurrentDebugLocation(EntryLoc);
475 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
476 IRB.CreateCall(SanCovFunction, GuardP);
477 IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
480 if (Options.Use8bitCounters) {
481 IRB.SetInsertPoint(IP);
482 Value *P = IRB.CreateAdd(
483 IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
484 ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
485 P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
486 LoadInst *LI = IRB.CreateLoad(P);
487 Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
488 StoreInst *SI = IRB.CreateStore(Inc, P);
489 SetNoSanitizeMetadata(LI);
490 SetNoSanitizeMetadata(SI);
493 if (Options.TraceBB) {
494 // Experimental support for tracing.
495 // Insert a callback with the same guard variable as used for coverage.
496 IRB.SetInsertPoint(IP);
497 IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
501 char SanitizerCoverageModule::ID = 0;
502 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
503 "SanitizerCoverage: TODO."
504 "ModulePass", false, false)
505 ModulePass *llvm::createSanitizerCoverageModulePass(
506 const SanitizerCoverageOptions &Options) {
507 return new SanitizerCoverageModule(Options);