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 (CoverageLevel=1)
15 // or all blocks (CoverageLevel>=2):
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 CoverageLevel>=3 we also split critical edges this effectively
23 // instrumenting all edges.
25 // CoverageLevel>=4 add indirect call profiling implented as a function call.
27 // This coverage implementation provides very limited data:
28 // it only tells if a given function (block) was ever executed. No counters.
29 // But for many use cases this is what we need and the added slowdown small.
31 //===----------------------------------------------------------------------===//
33 #include "llvm/Transforms/Instrumentation.h"
34 #include "llvm/ADT/ArrayRef.h"
35 #include "llvm/ADT/SmallVector.h"
36 #include "llvm/IR/CallSite.h"
37 #include "llvm/IR/DataLayout.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 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));
83 // Experimental 8-bit counters used as an additional search heuristic during
84 // coverage-guided fuzzing.
85 // The counters are not thread-friendly:
86 // - contention on these counters may cause significant slowdown;
87 // - the counter updates are racy and the results may be inaccurate.
88 // They are also inaccurate due to 8-bit integer overflow.
89 static cl::opt<bool> ClUse8bitCounters("sanitizer-coverage-8bit-counters",
90 cl::desc("Experimental 8-bit counters"),
91 cl::Hidden, cl::init(false));
95 class SanitizerCoverageModule : public ModulePass {
97 SanitizerCoverageModule(int CoverageLevel = 0)
99 CoverageLevel(std::max(CoverageLevel, (int)ClCoverageLevel)) {}
100 bool runOnModule(Module &M) override;
101 bool runOnFunction(Function &F);
102 static char ID; // Pass identification, replacement for typeid
103 const char *getPassName() const override {
104 return "SanitizerCoverageModule";
108 void InjectCoverageForIndirectCalls(Function &F,
109 ArrayRef<Instruction *> IndirCalls);
110 bool InjectCoverage(Function &F, ArrayRef<BasicBlock *> AllBlocks,
111 ArrayRef<Instruction *> IndirCalls);
112 void SetNoSanitizeMetada(Instruction *I);
113 void InjectCoverageAtBlock(Function &F, BasicBlock &BB, bool UseCalls);
114 Function *SanCovFunction;
115 Function *SanCovWithCheckFunction;
116 Function *SanCovIndirCallFunction;
117 Function *SanCovModuleInit;
118 Function *SanCovTraceEnter, *SanCovTraceBB;
123 GlobalVariable *GuardArray;
124 GlobalVariable *EightBitCounterArray;
131 static Function *checkInterfaceFunction(Constant *FuncOrBitcast) {
132 if (Function *F = dyn_cast<Function>(FuncOrBitcast))
135 raw_string_ostream Stream(Err);
136 Stream << "SanitizerCoverage interface function redefined: "
138 report_fatal_error(Err);
141 bool SanitizerCoverageModule::runOnModule(Module &M) {
142 if (!CoverageLevel) return false;
143 C = &(M.getContext());
144 auto &DL = M.getDataLayout();
145 IntptrTy = Type::getIntNTy(*C, DL.getPointerSizeInBits());
146 Type *VoidTy = Type::getVoidTy(*C);
148 Type *Int8PtrTy = PointerType::getUnqual(IRB.getInt8Ty());
149 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
152 Function::Create(FunctionType::get(VoidTy, false),
153 GlobalValue::InternalLinkage, kSanCovModuleCtorName, &M);
154 ReturnInst::Create(*C, BasicBlock::Create(*C, "", CtorFunc));
155 appendToGlobalCtors(M, CtorFunc, kSanCtorAndDtorPriority);
157 SanCovFunction = checkInterfaceFunction(
158 M.getOrInsertFunction(kSanCovName, VoidTy, Int32PtrTy, nullptr));
159 SanCovWithCheckFunction = checkInterfaceFunction(
160 M.getOrInsertFunction(kSanCovWithCheckName, VoidTy, Int32PtrTy, nullptr));
161 SanCovIndirCallFunction = checkInterfaceFunction(M.getOrInsertFunction(
162 kSanCovIndirCallName, VoidTy, IntptrTy, IntptrTy, nullptr));
163 SanCovModuleInit = checkInterfaceFunction(M.getOrInsertFunction(
164 kSanCovModuleInitName, Type::getVoidTy(*C), Int32PtrTy, IntptrTy,
165 Int8PtrTy, Int8PtrTy, nullptr));
166 SanCovModuleInit->setLinkage(Function::ExternalLinkage);
167 // We insert an empty inline asm after cov callbacks to avoid callback merge.
168 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
169 StringRef(""), StringRef(""),
170 /*hasSideEffects=*/true);
172 if (ClExperimentalTracing) {
173 SanCovTraceEnter = checkInterfaceFunction(
174 M.getOrInsertFunction(kSanCovTraceEnter, VoidTy, Int32PtrTy, nullptr));
175 SanCovTraceBB = checkInterfaceFunction(
176 M.getOrInsertFunction(kSanCovTraceBB, VoidTy, Int32PtrTy, nullptr));
179 // At this point we create a dummy array of guards because we don't
180 // know how many elements we will need.
181 Type *Int32Ty = IRB.getInt32Ty();
182 Type *Int8Ty = IRB.getInt8Ty();
185 new GlobalVariable(M, Int32Ty, false, GlobalValue::ExternalLinkage,
186 nullptr, "__sancov_gen_cov_tmp");
187 if (ClUse8bitCounters)
188 EightBitCounterArray =
189 new GlobalVariable(M, Int8Ty, false, GlobalVariable::ExternalLinkage,
190 nullptr, "__sancov_gen_cov_tmp");
195 // Now we know how many elements we need. Create an array of guards
196 // with one extra element at the beginning for the size.
197 Type *Int32ArrayNTy =
198 ArrayType::get(Int32Ty, SanCovFunction->getNumUses() + 1);
199 GlobalVariable *RealGuardArray = new GlobalVariable(
200 M, Int32ArrayNTy, false, GlobalValue::PrivateLinkage,
201 Constant::getNullValue(Int32ArrayNTy), "__sancov_gen_cov");
204 // Replace the dummy array with the real one.
205 GuardArray->replaceAllUsesWith(
206 IRB.CreatePointerCast(RealGuardArray, Int32PtrTy));
207 GuardArray->eraseFromParent();
209 GlobalVariable *RealEightBitCounterArray;
210 if (ClUse8bitCounters) {
211 // Make sure the array is 16-aligned.
212 static const int kCounterAlignment = 16;
214 ArrayType::get(Int8Ty, RoundUpToAlignment(SanCovFunction->getNumUses(),
216 RealEightBitCounterArray = new GlobalVariable(
217 M, Int8ArrayNTy, false, GlobalValue::PrivateLinkage,
218 Constant::getNullValue(Int8ArrayNTy), "__sancov_gen_cov_counter");
219 RealEightBitCounterArray->setAlignment(kCounterAlignment);
220 EightBitCounterArray->replaceAllUsesWith(
221 IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy));
222 EightBitCounterArray->eraseFromParent();
225 // Create variable for module (compilation unit) name
226 Constant *ModNameStrConst =
227 ConstantDataArray::getString(M.getContext(), M.getName(), true);
228 GlobalVariable *ModuleName =
229 new GlobalVariable(M, ModNameStrConst->getType(), true,
230 GlobalValue::PrivateLinkage, ModNameStrConst);
232 // Call __sanitizer_cov_module_init
233 IRB.SetInsertPoint(CtorFunc->getEntryBlock().getTerminator());
235 SanCovModuleInit, IRB.CreatePointerCast(RealGuardArray, Int32PtrTy),
236 ConstantInt::get(IntptrTy, SanCovFunction->getNumUses()),
238 ? IRB.CreatePointerCast(RealEightBitCounterArray, Int8PtrTy)
239 : Constant::getNullValue(Int8PtrTy),
240 IRB.CreatePointerCast(ModuleName, Int8PtrTy));
244 bool SanitizerCoverageModule::runOnFunction(Function &F) {
245 if (F.empty()) return false;
246 if (F.getName().find(".module_ctor") != std::string::npos)
247 return false; // Should not instrument sanitizer init functions.
248 if (CoverageLevel >= 3)
249 SplitAllCriticalEdges(F);
250 SmallVector<Instruction*, 8> IndirCalls;
251 SmallVector<BasicBlock*, 16> AllBlocks;
253 AllBlocks.push_back(&BB);
254 if (CoverageLevel >= 4)
255 for (auto &Inst : BB) {
257 if (CS && !CS.getCalledFunction())
258 IndirCalls.push_back(&Inst);
261 InjectCoverage(F, AllBlocks, IndirCalls);
266 SanitizerCoverageModule::InjectCoverage(Function &F,
267 ArrayRef<BasicBlock *> AllBlocks,
268 ArrayRef<Instruction *> IndirCalls) {
269 if (!CoverageLevel) return false;
271 if (CoverageLevel == 1) {
272 InjectCoverageAtBlock(F, F.getEntryBlock(), false);
274 for (auto BB : AllBlocks)
275 InjectCoverageAtBlock(F, *BB,
276 ClCoverageBlockThreshold < AllBlocks.size());
278 InjectCoverageForIndirectCalls(F, IndirCalls);
282 // On every indirect call we call a run-time function
283 // __sanitizer_cov_indir_call* with two parameters:
285 // - global cache array that contains kCacheSize pointers (zero-initialized).
286 // The cache is used to speed up recording the caller-callee pairs.
287 // The address of the caller is passed implicitly via caller PC.
288 // kCacheSize is encoded in the name of the run-time function.
289 void SanitizerCoverageModule::InjectCoverageForIndirectCalls(
290 Function &F, ArrayRef<Instruction *> IndirCalls) {
291 if (IndirCalls.empty()) return;
292 const int kCacheSize = 16;
293 const int kCacheAlignment = 64; // Align for better performance.
294 Type *Ty = ArrayType::get(IntptrTy, kCacheSize);
295 for (auto I : IndirCalls) {
298 Value *Callee = CS.getCalledValue();
299 if (dyn_cast<InlineAsm>(Callee)) continue;
300 GlobalVariable *CalleeCache = new GlobalVariable(
301 *F.getParent(), Ty, false, GlobalValue::PrivateLinkage,
302 Constant::getNullValue(Ty), "__sancov_gen_callee_cache");
303 CalleeCache->setAlignment(kCacheAlignment);
304 IRB.CreateCall2(SanCovIndirCallFunction,
305 IRB.CreatePointerCast(Callee, IntptrTy),
306 IRB.CreatePointerCast(CalleeCache, IntptrTy));
310 void SanitizerCoverageModule::SetNoSanitizeMetada(Instruction *I) {
312 I->getParent()->getParent()->getParent()->getMDKindID("nosanitize"),
313 MDNode::get(*C, None));
316 void SanitizerCoverageModule::InjectCoverageAtBlock(Function &F, BasicBlock &BB,
318 BasicBlock::iterator IP = BB.getFirstInsertionPt(), BE = BB.end();
319 // Skip static allocas at the top of the entry block so they don't become
320 // dynamic when we split the block. If we used our optimized stack layout,
321 // then there will only be one alloca and it will come first.
322 for (; IP != BE; ++IP) {
323 AllocaInst *AI = dyn_cast<AllocaInst>(IP);
324 if (!AI || !AI->isStaticAlloca())
328 bool IsEntryBB = &BB == &F.getEntryBlock();
330 IsEntryBB ? IP->getDebugLoc().getFnDebugLoc(*C) : IP->getDebugLoc();
332 IRB.SetCurrentDebugLocation(EntryLoc);
333 SmallVector<Value *, 1> Indices;
334 Value *GuardP = IRB.CreateAdd(
335 IRB.CreatePointerCast(GuardArray, IntptrTy),
336 ConstantInt::get(IntptrTy, (1 + SanCovFunction->getNumUses()) * 4));
337 Type *Int32PtrTy = PointerType::getUnqual(IRB.getInt32Ty());
338 GuardP = IRB.CreateIntToPtr(GuardP, Int32PtrTy);
340 IRB.CreateCall(SanCovWithCheckFunction, GuardP);
342 LoadInst *Load = IRB.CreateLoad(GuardP);
343 Load->setAtomic(Monotonic);
344 Load->setAlignment(4);
345 SetNoSanitizeMetada(Load);
346 Value *Cmp = IRB.CreateICmpSGE(Constant::getNullValue(Load->getType()), Load);
347 Instruction *Ins = SplitBlockAndInsertIfThen(
348 Cmp, IP, false, MDBuilder(*C).createBranchWeights(1, 100000));
349 IRB.SetInsertPoint(Ins);
350 IRB.SetCurrentDebugLocation(EntryLoc);
351 // __sanitizer_cov gets the PC of the instruction using GET_CALLER_PC.
352 IRB.CreateCall(SanCovFunction, GuardP);
353 IRB.CreateCall(EmptyAsm); // Avoids callback merge.
356 if(ClUse8bitCounters) {
357 IRB.SetInsertPoint(IP);
358 Value *P = IRB.CreateAdd(
359 IRB.CreatePointerCast(EightBitCounterArray, IntptrTy),
360 ConstantInt::get(IntptrTy, SanCovFunction->getNumUses() - 1));
361 P = IRB.CreateIntToPtr(P, IRB.getInt8PtrTy());
362 LoadInst *LI = IRB.CreateLoad(P);
363 Value *Inc = IRB.CreateAdd(LI, ConstantInt::get(IRB.getInt8Ty(), 1));
364 StoreInst *SI = IRB.CreateStore(Inc, P);
365 SetNoSanitizeMetada(LI);
366 SetNoSanitizeMetada(SI);
369 if (ClExperimentalTracing) {
370 // Experimental support for tracing.
371 // Insert a callback with the same guard variable as used for coverage.
372 IRB.SetInsertPoint(IP);
373 IRB.CreateCall(IsEntryBB ? SanCovTraceEnter : SanCovTraceBB, GuardP);
377 char SanitizerCoverageModule::ID = 0;
378 INITIALIZE_PASS(SanitizerCoverageModule, "sancov",
379 "SanitizerCoverage: TODO."
380 "ModulePass", false, false)
381 ModulePass *llvm::createSanitizerCoverageModulePass(int CoverageLevel) {
382 return new SanitizerCoverageModule(CoverageLevel);