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 kSanCovModuleCtorName = "sancov.module_ctor";
63 static const uint64_t kSanCtorAndDtorPriority = 2;
65 static cl::opt<int> ClCoverageLevel("sanitizer-coverage-level",
66 cl::desc("Sanitizer Coverage. 0: none, 1: entry block, 2: all blocks, "
67 "3: all blocks and critical edges, "
68 "4: above plus indirect calls"),
69 cl::Hidden, cl::init(0));
71 static cl::opt<unsigned> ClCoverageBlockThreshold(
72 "sanitizer-coverage-block-threshold",
73 cl::desc("Use a callback with a guard check inside it if there are"
74 " more than this number of blocks."),
75 cl::Hidden, cl::init(500));
78 ClExperimentalTracing("sanitizer-coverage-experimental-tracing",
79 cl::desc("Experimental basic-block tracing: insert "
80 "callbacks at every basic block"),
81 cl::Hidden, cl::init(false));
84 ClExperimentalCMPTracing("sanitizer-coverage-experimental-trace-compares",
85 cl::desc("Experimental tracing of CMP and similar "
87 cl::Hidden, cl::init(false));
89 // Experimental 8-bit counters used as an additional search heuristic during
90 // coverage-guided fuzzing.
91 // The counters are not thread-friendly:
92 // - contention on these counters may cause significant slowdown;
93 // - the counter updates are racy and the results may be inaccurate.
94 // They are also inaccurate due to 8-bit integer overflow.
95 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
96 cl::desc("Experimental 8-bit counters"),
97 cl::Hidden, cl::init(false));
101 SanitizerCoverageOptions getOptions(int LegacyCoverageLevel) {
102 SanitizerCoverageOptions Res;
103 switch (LegacyCoverageLevel) {
105 Res.CoverageType = SanitizerCoverageOptions::SCK_None;
108 Res.CoverageType = SanitizerCoverageOptions::SCK_Function;
111 Res.CoverageType = SanitizerCoverageOptions::SCK_BB;
114 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
117 Res.CoverageType = SanitizerCoverageOptions::SCK_Edge;
118 Res.IndirectCalls = true;
124 SanitizerCoverageOptions OverrideFromCL(SanitizerCoverageOptions Options) {
125 // Sets CoverageType and IndirectCalls.
126 SanitizerCoverageOptions CLOpts = getOptions(ClCoverageLevel);
127 Options.CoverageType = std::max(Options.CoverageType, CLOpts.CoverageType);
128 Options.IndirectCalls |= CLOpts.IndirectCalls;
129 Options.TraceBB |= ClExperimentalTracing;
130 Options.TraceCmp |= ClExperimentalCMPTracing;
131 Options.Use8bitCounters |= ClUse8bitCounters;
135 class SanitizerCoverageModule : public ModulePass {
137 SanitizerCoverageModule(
138 const SanitizerCoverageOptions &Options = SanitizerCoverageOptions())
139 : ModulePass(ID), Options(OverrideFromCL(Options)) {}
140 bool runOnModule(Module &M) override;
141 bool runOnFunction(Function &F);
142 static char ID; // Pass identification, replacement for typeid
143 const char *getPassName() const override {
144 return "SanitizerCoverageModule";
148 void InjectCoverageForIndirectCalls(Function &F,
149 ArrayRef<Instruction *> IndirCalls);
150 void InjectTraceForCmp(Function &F, ArrayRef<Instruction *> CmpTraceTargets);
151 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks);
152 void SetNoSanitizeMetadata(Instruction *I);
153 void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
154 unsigned NumberOfInstrumentedBlocks() {
155 return SanCovFunction->getNumUses() + SanCovWithCheckFunction->getNumUses();
157 Function *SanCovFunction;
158 Function *SanCovWithCheckFunction;
159 Function *SanCovIndirCallFunction;
160 Function *SanCovTraceEnter, *SanCovTraceBB;
161 Function *SanCovTraceCmpFunction;
163 Type *IntptrTy, *Int64Ty;
165 const DataLayout *DL;
167 GlobalVariable *GuardArray;
168 GlobalVariable *EightBitCounterArray;
170 SanitizerCoverageOptions Options;
175 bool SanitizerCoverageModule::runOnModule(Module &M) {
176 if (Options.CoverageType == SanitizerCoverageOptions::SCK_None)
178 C = &(M.getContext());
179 DL = &M.getDataLayout();
180 IntptrTy = Type::getIntNTy(*C, DL->getPointerSizeInBits());
181 Type *VoidTy = Type::getVoidTy(*C);
183 Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
184 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
185 Int64Ty = IRB.getInt64Ty();
187 SanCovFunction = checkSanitizerInterfaceFunction(
188 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
189 SanCovWithCheckFunction = checkSanitizerInterfaceFunction(
190 M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
191 SanCovIndirCallFunction =
192 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
193 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
194 SanCovTraceCmpFunction =
195 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
196 kSanCovTraceCmp, VoidTy, Int64Ty, Int64Ty, Int64Ty, nullptr));
198 // We insert an empty inline asm after cov callbacks to avoid callback merge.
199 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
200 StringRef(""), StringRef(""),
201 /*hasSideEffects=*/true);
203 if (Options.TraceBB) {
204 SanCovTraceEnter = checkSanitizerInterfaceFunction(
205 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
206 SanCovTraceBB = checkSanitizerInterfaceFunction(
207 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
210 // At this point we create a dummy array of guards because we don't
211 // know how many elements we will need.
212 Type *Int32Ty = IRB.getInt32Ty();
213 Type *Int8Ty = IRB.getInt8Ty();
216 new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
217 nullptr, "__sancov_gen_cov_tmp");
218 if (Options.Use8bitCounters)
219 EightBitCounterArray =
220 new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
221 nullptr, "__sancov_gen_cov_tmp");
226 auto N = NumberOfInstrumentedBlocks();
228 // Now we know how many elements we need. Create an array of guards
229 // with one extra element at the beginning for the size.
230 Type *Int32ArrayNTy = ArrayType::get(Int32Ty, N + 1);
231 GlobalVariable *RealGuardArray = new GlobalVariable(
232 M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
233 Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
236 // Replace the dummy array with the real one.
237 GuardArray->replaceAllUsesWith(
238 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
239 GuardArray->eraseFromParent();
241 GlobalVariable *RealEightBitCounterArray;
242 if (Options.Use8bitCounters) {
243 // Make sure the array is 16-aligned.
244 static const int kCounterAlignment = 16;
246 ArrayType::get(Int8Ty, RoundUpToAlignment(N, kCounterAlignment));
247 RealEightBitCounterArray = new GlobalVariable(
248 M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
249 Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
250 RealEightBitCounterArray->setAlignment(kCounterAlignment);
251 EightBitCounterArray->replaceAllUsesWith(
252 IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
253 EightBitCounterArray->eraseFromParent();
256 // Create variable for module (compilation unit) name
257 Constant *ModNameStrConst =
258 ConstantDataArray::getString(M.getContext(), M.getName(), true);
259 GlobalVariable *ModuleName =
260 new GlobalVariable(M, ModNameStrConst->getType(), true,
261 GlobalValue::PrivateLinkage, ModNameStrConst);
264 std::tie(CtorFunc, std::ignore) = createSanitizerCtorAndInitFunctions(
265 M, kSanCovModuleCtorName, kSanCovModuleInitName,
266 {Int32PtrTy, IntptrTy, Int8PtrTy, Int8PtrTy},
267 {IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
268 ConstantInt::get(IntptrTy, N),
269 Options.Use8bitCounters
270 ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
271 : Constant::getNullValue(Int8PtrTy),
272 IRB.CreatePointerCast(ModuleName, Int8PtrTy)});
274 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
279 bool SanitizerCoverageModule::runOnFunction(Function &F) {
280 if (F.empty()) return false;
281 if (F.getName().find(".module_ctor") != std::string::npos)
282 return false; // Should not instrument sanitizer init functions.
283 if (Options.CoverageType >= SanitizerCoverageOptions::SCK_Edge)
284 SplitAllCriticalEdges(F);
285 SmallVector<Instruction*, 8> IndirCalls;
286 SmallVector<BasicBlock*, 16> AllBlocks;
287 SmallVector<Instruction*, 8> CmpTraceTargets;
289 AllBlocks.push_back(&BB);
290 for (auto &Inst : BB) {
291 if (Options.IndirectCalls) {
293 if (CS && !CS.getCalledFunction())
294 IndirCalls.push_back(&Inst);
296 if (Options.TraceCmp && isa<ICmpInst>(&Inst))
297 CmpTraceTargets.push_back(&Inst);
300 InjectCoverage(F, AllBlocks);
301 InjectCoverageForIndirectCalls(F, IndirCalls);
302 InjectTraceForCmp(F, CmpTraceTargets);
306 bool SanitizerCoverageModule::InjectCoverage(Function &F,
307 ArrayRef<BasicBlock *> AllBlocks) {
308 switch (Options.CoverageType) {
309 case SanitizerCoverageOptions::SCK_None:
311 case SanitizerCoverageOptions::SCK_Function:
312 InjectCoverageAtBlock(F, F.getEntryBlock(), false);
315 bool UseCalls = ClCoverageBlockThreshold < AllBlocks.size();
316 for (auto BB : AllBlocks)
317 InjectCoverageAtBlock(F, *BB, UseCalls);
323 // On every indirect call we call a run-time function
324 // __sanitizer_cov_indir_call* with two parameters:
326 // - global cache array that contains kCacheSize pointers (zero-initialized).
327 // The cache is used to speed up recording the caller-callee pairs.
328 // The address of the caller is passed implicitly via caller PC.
329 // kCacheSize is encoded in the name of the run-time function.
330 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
331 Function &F, ArrayRef<Instruction *> IndirCalls) {
332 if (IndirCalls.empty()) return;
333 const int kCacheSize = 16;
334 const int kCacheAlignment = 64; // Align for better performance.
335 Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
336 for (auto I : IndirCalls) {
339 Value *Callee = CS.getCalledValue();
340 if (isa<InlineAsm>(Callee)) continue;
341 GlobalVariable *CalleeCache = new GlobalVariable(
342 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
343 Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
344 CalleeCache->setAlignment(kCacheAlignment);
345 IRB.CreateCall(SanCovIndirCallFunction,
346 {IRB.CreatePointerCast(Callee, IntptrTy),
347 IRB.CreatePointerCast(CalleeCache, IntptrTy)});
351 void SanitizerCoverageModule::InjectTraceForCmp(
352 Function &F, ArrayRef<Instruction *> CmpTraceTargets) {
353 for (auto I : CmpTraceTargets) {
354 if (ICmpInst *ICMP = dyn_cast<ICmpInst>(I)) {
355 IRBuilder<> IRB(ICMP);
356 Value *A0 = ICMP->getOperand(0);
357 Value *A1 = ICMP->getOperand(1);
358 if (!A0->getType()->isIntegerTy()) continue;
359 uint64_t TypeSize = DL->getTypeStoreSizeInBits(A0->getType());
360 // __sanitizer_cov_trace_cmp((type_size << 32) | predicate, A0, A1);
362 SanCovTraceCmpFunction,
363 {ConstantInt::get(Int64Ty, (TypeSize << 32) | ICMP->getPredicate()),
364 IRB.CreateIntCast(A0, Int64Ty, true),
365 IRB.CreateIntCast(A1, Int64Ty, true)});
370 void SanitizerCoverageModule::SetNoSanitizeMetadata(Instruction *I) {
372 I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
373 MDNode::get(*C, None));
376 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
378 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
379 // Skip static allocas at the top of the entry block so they don't become
380 // dynamic when we split the block. If we used our optimized stack layout,
381 // then there will only be one alloca and it will come first.
382 for (; IP != BE; ++IP) {
383 AllocaInst *AI = dyn_cast<AllocaInst>(IP);
384 if (!AI || !AI->isStaticAlloca())
388 bool IsEntryBB = &BB == &F.getEntryBlock();
391 if (auto SP = getDISubprogram(&F))
392 EntryLoc = DebugLoc::get(SP->getScopeLine(), 0, SP);
394 EntryLoc = IP->getDebugLoc();
398 IRB.SetCurrentDebugLocation(EntryLoc);
399 SmallVector<Value *, 1> Indices;
400 Value *GuardP = IRB.CreateAdd(
401 IRB.CreatePointerCast(GuardArray, IntptrTy),
402 ConstantInt::get(IntptrTy, (1 + NumberOfInstrumentedBlocks()) * 4));
403 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
404 GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
406 IRB.CreateCall(SanCovWithCheckFunction, GuardP);
408 LoadInst *Load = IRB.CreateLoad(GuardP);
409 Load->setAtomic(Monotonic);
410 Load->setAlignment(4);
411 SetNoSanitizeMetadata(Load);
412 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
413 Instruction *Ins = SplitBlockAndInsertIfThen(
414 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
415 IRB.SetInsertPoint(Ins);
416 IRB.SetCurrentDebugLocation(EntryLoc);
417 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
418 IRB.CreateCall(SanCovFunction, GuardP);
419 IRB.CreateCall(EmptyAsm, {}); // Avoids callback merge.
422 if (Options.Use8bitCounters) {
423 IRB.SetInsertPoint(IP);
424 Value *P = IRB.CreateAdd(
425 IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
426 ConstantInt::get(IntptrTy, NumberOfInstrumentedBlocks() - 1));
427 P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
428 LoadInst *LI = IRB.CreateLoad(P);
429 Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
430 StoreInst *SI = IRB.CreateStore(Inc, P);
431 SetNoSanitizeMetadata(LI);
432 SetNoSanitizeMetadata(SI);
435 if (Options.TraceBB) {
436 // Experimental support for tracing.
437 // Insert a callback with the same guard variable as used for coverage.
438 IRB.SetInsertPoint(IP);
439 IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
443 char SanitizerCoverageModule::ID = 0;
444 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
445 "SanitizerCoverage: TODO."
446 "ModulePass", false, false)
447 ModulePass *llvm::createSanitizerCoverageModulePass(
448 const SanitizerCoverageOptions &Options) {
449 return new SanitizerCoverageModule(Options);