1 //===-- AddressSanitizer.cpp - memory error detector ------------*- C++ -*-===//
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 // This file is a part of AddressSanitizer, an address sanity checker.
11 // Details of the algorithm:
12 // http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Transforms/Instrumentation.h"
17 #include "llvm/ADT/ArrayRef.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/DenseSet.h"
20 #include "llvm/ADT/DepthFirstIterator.h"
21 #include "llvm/ADT/SmallSet.h"
22 #include "llvm/ADT/SmallString.h"
23 #include "llvm/ADT/SmallVector.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/ADT/StringExtras.h"
26 #include "llvm/ADT/Triple.h"
27 #include "llvm/Analysis/MemoryBuiltins.h"
28 #include "llvm/Analysis/TargetLibraryInfo.h"
29 #include "llvm/Analysis/ValueTracking.h"
30 #include "llvm/IR/CallSite.h"
31 #include "llvm/IR/DIBuilder.h"
32 #include "llvm/IR/DataLayout.h"
33 #include "llvm/IR/Dominators.h"
34 #include "llvm/IR/Function.h"
35 #include "llvm/IR/IRBuilder.h"
36 #include "llvm/IR/InlineAsm.h"
37 #include "llvm/IR/InstVisitor.h"
38 #include "llvm/IR/IntrinsicInst.h"
39 #include "llvm/IR/LLVMContext.h"
40 #include "llvm/IR/MDBuilder.h"
41 #include "llvm/IR/Module.h"
42 #include "llvm/IR/Type.h"
43 #include "llvm/MC/MCSectionMachO.h"
44 #include "llvm/Support/CommandLine.h"
45 #include "llvm/Support/DataTypes.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/Endian.h"
48 #include "llvm/Support/SwapByteOrder.h"
49 #include "llvm/Support/raw_ostream.h"
50 #include "llvm/Transforms/Scalar.h"
51 #include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
52 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
53 #include "llvm/Transforms/Utils/Cloning.h"
54 #include "llvm/Transforms/Utils/Local.h"
55 #include "llvm/Transforms/Utils/ModuleUtils.h"
56 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
59 #include <system_error>
63 #define DEBUG_TYPE "asan"
65 static const uint64_t kDefaultShadowScale = 3;
66 static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
67 static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
68 static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
69 static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000; // < 2G.
70 static const uint64_t kLinuxKasan_ShadowOffset64 = 0xdffffc0000000000;
71 static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
72 static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000;
73 static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 37;
74 static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36;
75 static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
76 static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
77 static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
79 static const size_t kMinStackMallocSize = 1 << 6; // 64B
80 static const size_t kMaxStackMallocSize = 1 << 16; // 64K
81 static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
82 static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
84 static const char *const kAsanModuleCtorName = "asan.module_ctor";
85 static const char *const kAsanModuleDtorName = "asan.module_dtor";
86 static const uint64_t kAsanCtorAndDtorPriority = 1;
87 static const char *const kAsanReportErrorTemplate = "__asan_report_";
88 static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
89 static const char *const kAsanUnregisterGlobalsName =
90 "__asan_unregister_globals";
91 static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
92 static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
93 static const char *const kAsanInitName = "__asan_init_v5";
94 static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
95 static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
96 static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
97 static const int kMaxAsanStackMallocSizeClass = 10;
98 static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
99 static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
100 static const char *const kAsanGenPrefix = "__asan_gen_";
101 static const char *const kSanCovGenPrefix = "__sancov_gen_";
102 static const char *const kAsanPoisonStackMemoryName =
103 "__asan_poison_stack_memory";
104 static const char *const kAsanUnpoisonStackMemoryName =
105 "__asan_unpoison_stack_memory";
107 static const char *const kAsanOptionDetectUAR =
108 "__asan_option_detect_stack_use_after_return";
110 static const char *const kAsanAllocaPoison = "__asan_alloca_poison";
111 static const char *const kAsanAllocasUnpoison = "__asan_allocas_unpoison";
113 // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
114 static const size_t kNumberOfAccessSizes = 5;
116 static const unsigned kAllocaRzSize = 32;
118 // Command-line flags.
119 static cl::opt<bool> ClEnableKasan(
120 "asan-kernel", cl::desc("Enable KernelAddressSanitizer instrumentation"),
121 cl::Hidden, cl::init(false));
123 // This flag may need to be replaced with -f[no-]asan-reads.
124 static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
125 cl::desc("instrument read instructions"),
126 cl::Hidden, cl::init(true));
127 static cl::opt<bool> ClInstrumentWrites(
128 "asan-instrument-writes", cl::desc("instrument write instructions"),
129 cl::Hidden, cl::init(true));
130 static cl::opt<bool> ClInstrumentAtomics(
131 "asan-instrument-atomics",
132 cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden,
134 static cl::opt<bool> ClAlwaysSlowPath(
135 "asan-always-slow-path",
136 cl::desc("use instrumentation with slow path for all accesses"), cl::Hidden,
138 // This flag limits the number of instructions to be instrumented
139 // in any given BB. Normally, this should be set to unlimited (INT_MAX),
140 // but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary
142 static cl::opt<int> ClMaxInsnsToInstrumentPerBB(
143 "asan-max-ins-per-bb", cl::init(10000),
144 cl::desc("maximal number of instructions to instrument in any given BB"),
146 // This flag may need to be replaced with -f[no]asan-stack.
147 static cl::opt<bool> ClStack("asan-stack", cl::desc("Handle stack memory"),
148 cl::Hidden, cl::init(true));
149 static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
150 cl::desc("Check return-after-free"),
151 cl::Hidden, cl::init(true));
152 // This flag may need to be replaced with -f[no]asan-globals.
153 static cl::opt<bool> ClGlobals("asan-globals",
154 cl::desc("Handle global objects"), cl::Hidden,
156 static cl::opt<bool> ClInitializers("asan-initialization-order",
157 cl::desc("Handle C++ initializer order"),
158 cl::Hidden, cl::init(true));
159 static cl::opt<bool> ClInvalidPointerPairs(
160 "asan-detect-invalid-pointer-pair",
161 cl::desc("Instrument <, <=, >, >=, - with pointer operands"), cl::Hidden,
163 static cl::opt<unsigned> ClRealignStack(
164 "asan-realign-stack",
165 cl::desc("Realign stack to the value of this flag (power of two)"),
166 cl::Hidden, cl::init(32));
167 static cl::opt<int> ClInstrumentationWithCallsThreshold(
168 "asan-instrumentation-with-call-threshold",
170 "If the function being instrumented contains more than "
171 "this number of memory accesses, use callbacks instead of "
172 "inline checks (-1 means never use callbacks)."),
173 cl::Hidden, cl::init(7000));
174 static cl::opt<std::string> ClMemoryAccessCallbackPrefix(
175 "asan-memory-access-callback-prefix",
176 cl::desc("Prefix for memory access callbacks"), cl::Hidden,
177 cl::init("__asan_"));
178 static cl::opt<bool> ClInstrumentAllocas("asan-instrument-allocas",
179 cl::desc("instrument dynamic allocas"),
180 cl::Hidden, cl::init(false));
181 static cl::opt<bool> ClSkipPromotableAllocas(
182 "asan-skip-promotable-allocas",
183 cl::desc("Do not instrument promotable allocas"), cl::Hidden,
186 // These flags allow to change the shadow mapping.
187 // The shadow mapping looks like
188 // Shadow = (Mem >> scale) + (1 << offset_log)
189 static cl::opt<int> ClMappingScale("asan-mapping-scale",
190 cl::desc("scale of asan shadow mapping"),
191 cl::Hidden, cl::init(0));
193 // Optimization flags. Not user visible, used mostly for testing
194 // and benchmarking the tool.
195 static cl::opt<bool> ClOpt("asan-opt", cl::desc("Optimize instrumentation"),
196 cl::Hidden, cl::init(true));
197 static cl::opt<bool> ClOptSameTemp(
198 "asan-opt-same-temp", cl::desc("Instrument the same temp just once"),
199 cl::Hidden, cl::init(true));
200 static cl::opt<bool> ClOptGlobals("asan-opt-globals",
201 cl::desc("Don't instrument scalar globals"),
202 cl::Hidden, cl::init(true));
203 static cl::opt<bool> ClOptStack(
204 "asan-opt-stack", cl::desc("Don't instrument scalar stack variables"),
205 cl::Hidden, cl::init(false));
207 static cl::opt<bool> ClCheckLifetime(
208 "asan-check-lifetime",
209 cl::desc("Use llvm.lifetime intrinsics to insert extra checks"), cl::Hidden,
212 static cl::opt<bool> ClDynamicAllocaStack(
213 "asan-stack-dynamic-alloca",
214 cl::desc("Use dynamic alloca to represent stack variables"), cl::Hidden,
217 static cl::opt<uint32_t> ClForceExperiment(
218 "asan-force-experiment",
219 cl::desc("Force optimization experiment (for testing)"), cl::Hidden,
223 static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
225 static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
226 cl::Hidden, cl::init(0));
227 static cl::opt<std::string> ClDebugFunc("asan-debug-func", cl::Hidden,
228 cl::desc("Debug func"));
229 static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
230 cl::Hidden, cl::init(-1));
231 static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"),
232 cl::Hidden, cl::init(-1));
234 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
235 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
236 STATISTIC(NumOptimizedAccessesToGlobalVar,
237 "Number of optimized accesses to global vars");
238 STATISTIC(NumOptimizedAccessesToStackVar,
239 "Number of optimized accesses to stack vars");
242 /// Frontend-provided metadata for source location.
243 struct LocationMetadata {
248 LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {}
250 bool empty() const { return Filename.empty(); }
252 void parse(MDNode *MDN) {
253 assert(MDN->getNumOperands() == 3);
254 MDString *DIFilename = cast<MDString>(MDN->getOperand(0));
255 Filename = DIFilename->getString();
257 mdconst::extract<ConstantInt>(MDN->getOperand(1))->getLimitedValue();
259 mdconst::extract<ConstantInt>(MDN->getOperand(2))->getLimitedValue();
263 /// Frontend-provided metadata for global variables.
264 class GlobalsMetadata {
267 Entry() : SourceLoc(), Name(), IsDynInit(false), IsBlacklisted(false) {}
268 LocationMetadata SourceLoc;
274 GlobalsMetadata() : inited_(false) {}
276 void init(Module &M) {
279 NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
280 if (!Globals) return;
281 for (auto MDN : Globals->operands()) {
282 // Metadata node contains the global and the fields of "Entry".
283 assert(MDN->getNumOperands() == 5);
284 auto *GV = mdconst::extract_or_null<GlobalVariable>(MDN->getOperand(0));
285 // The optimizer may optimize away a global entirely.
287 // We can already have an entry for GV if it was merged with another
289 Entry &E = Entries[GV];
290 if (auto *Loc = cast_or_null<MDNode>(MDN->getOperand(1)))
291 E.SourceLoc.parse(Loc);
292 if (auto *Name = cast_or_null<MDString>(MDN->getOperand(2)))
293 E.Name = Name->getString();
294 ConstantInt *IsDynInit =
295 mdconst::extract<ConstantInt>(MDN->getOperand(3));
296 E.IsDynInit |= IsDynInit->isOne();
297 ConstantInt *IsBlacklisted =
298 mdconst::extract<ConstantInt>(MDN->getOperand(4));
299 E.IsBlacklisted |= IsBlacklisted->isOne();
303 /// Returns metadata entry for a given global.
304 Entry get(GlobalVariable *G) const {
305 auto Pos = Entries.find(G);
306 return (Pos != Entries.end()) ? Pos->second : Entry();
311 DenseMap<GlobalVariable *, Entry> Entries;
314 /// This struct defines the shadow mapping using the rule:
315 /// shadow = (mem >> Scale) ADD-or-OR Offset.
316 struct ShadowMapping {
322 static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize,
324 bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
325 bool IsIOS = TargetTriple.isiOS();
326 bool IsFreeBSD = TargetTriple.isOSFreeBSD();
327 bool IsLinux = TargetTriple.isOSLinux();
328 bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 ||
329 TargetTriple.getArch() == llvm::Triple::ppc64le;
330 bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
331 bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips ||
332 TargetTriple.getArch() == llvm::Triple::mipsel;
333 bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 ||
334 TargetTriple.getArch() == llvm::Triple::mips64el;
335 bool IsAArch64 = TargetTriple.getArch() == llvm::Triple::aarch64;
336 bool IsWindows = TargetTriple.isOSWindows();
338 ShadowMapping Mapping;
341 // Android is always PIE, which means that the beginning of the address
342 // space is always available.
344 } else if (LongSize == 32) {
346 Mapping.Offset = kMIPS32_ShadowOffset32;
348 Mapping.Offset = kFreeBSD_ShadowOffset32;
350 Mapping.Offset = kIOSShadowOffset32;
352 Mapping.Offset = kWindowsShadowOffset32;
354 Mapping.Offset = kDefaultShadowOffset32;
355 } else { // LongSize == 64
357 Mapping.Offset = kPPC64_ShadowOffset64;
359 Mapping.Offset = kFreeBSD_ShadowOffset64;
360 else if (IsLinux && IsX86_64) {
362 Mapping.Offset = kLinuxKasan_ShadowOffset64;
364 Mapping.Offset = kSmallX86_64ShadowOffset;
366 Mapping.Offset = kMIPS64_ShadowOffset64;
368 Mapping.Offset = kAArch64_ShadowOffset64;
370 Mapping.Offset = kDefaultShadowOffset64;
373 Mapping.Scale = kDefaultShadowScale;
374 if (ClMappingScale) {
375 Mapping.Scale = ClMappingScale;
378 // OR-ing shadow offset if more efficient (at least on x86) if the offset
379 // is a power of two, but on ppc64 we have to use add since the shadow
380 // offset is not necessary 1/8-th of the address space.
381 Mapping.OrShadowOffset = !IsPPC64 && !(Mapping.Offset & (Mapping.Offset - 1));
386 static size_t RedzoneSizeForScale(int MappingScale) {
387 // Redzone used for stack and globals is at least 32 bytes.
388 // For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
389 return std::max(32U, 1U << MappingScale);
392 /// AddressSanitizer: instrument the code in module to find memory bugs.
393 struct AddressSanitizer : public FunctionPass {
394 explicit AddressSanitizer(bool CompileKernel = false)
395 : FunctionPass(ID), CompileKernel(CompileKernel || ClEnableKasan) {
396 initializeAddressSanitizerPass(*PassRegistry::getPassRegistry());
398 const char *getPassName() const override {
399 return "AddressSanitizerFunctionPass";
401 void getAnalysisUsage(AnalysisUsage &AU) const override {
402 AU.addRequired<DominatorTreeWrapperPass>();
403 AU.addRequired<TargetLibraryInfoWrapperPass>();
405 uint64_t getAllocaSizeInBytes(AllocaInst *AI) const {
406 Type *Ty = AI->getAllocatedType();
407 uint64_t SizeInBytes =
408 AI->getModule()->getDataLayout().getTypeAllocSize(Ty);
411 /// Check if we want (and can) handle this alloca.
412 bool isInterestingAlloca(AllocaInst &AI);
414 // Check if we have dynamic alloca.
415 bool isDynamicAlloca(AllocaInst &AI) const {
416 return AI.isArrayAllocation() || !AI.isStaticAlloca();
419 /// If it is an interesting memory access, return the PointerOperand
420 /// and set IsWrite/Alignment. Otherwise return nullptr.
421 Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
422 uint64_t *TypeSize, unsigned *Alignment);
423 void instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, Instruction *I,
424 bool UseCalls, const DataLayout &DL);
425 void instrumentPointerComparisonOrSubtraction(Instruction *I);
426 void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
427 Value *Addr, uint32_t TypeSize, bool IsWrite,
428 Value *SizeArgument, bool UseCalls, uint32_t Exp);
429 void instrumentUnusualSizeOrAlignment(Instruction *I, Value *Addr,
430 uint32_t TypeSize, bool IsWrite,
431 Value *SizeArgument, bool UseCalls,
433 Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
434 Value *ShadowValue, uint32_t TypeSize);
435 Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
436 bool IsWrite, size_t AccessSizeIndex,
437 Value *SizeArgument, uint32_t Exp);
438 void instrumentMemIntrinsic(MemIntrinsic *MI);
439 Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
440 bool runOnFunction(Function &F) override;
441 bool maybeInsertAsanInitAtFunctionEntry(Function &F);
442 void markEscapedLocalAllocas(Function &F);
443 bool doInitialization(Module &M) override;
444 static char ID; // Pass identification, replacement for typeid
446 DominatorTree &getDominatorTree() const { return *DT; }
449 void initializeCallbacks(Module &M);
451 bool LooksLikeCodeInBug11395(Instruction *I);
452 bool GlobalIsLinkerInitialized(GlobalVariable *G);
453 bool isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis, Value *Addr,
454 uint64_t TypeSize) const;
456 /// Helper to cleanup per-function state.
457 struct FunctionStateRAII {
458 AddressSanitizer *Pass;
459 FunctionStateRAII(AddressSanitizer *Pass) : Pass(Pass) {
460 assert(Pass->ProcessedAllocas.empty() &&
461 "last pass forgot to clear cache");
463 ~FunctionStateRAII() { Pass->ProcessedAllocas.clear(); }
471 ShadowMapping Mapping;
473 Function *AsanCtorFunction = nullptr;
474 Function *AsanInitFunction = nullptr;
475 Function *AsanHandleNoReturnFunc;
476 Function *AsanPtrCmpFunction, *AsanPtrSubFunction;
477 // This array is indexed by AccessIsWrite, Experiment and log2(AccessSize).
478 Function *AsanErrorCallback[2][2][kNumberOfAccessSizes];
479 Function *AsanMemoryAccessCallback[2][2][kNumberOfAccessSizes];
480 // This array is indexed by AccessIsWrite and Experiment.
481 Function *AsanErrorCallbackSized[2][2];
482 Function *AsanMemoryAccessCallbackSized[2][2];
483 Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
485 GlobalsMetadata GlobalsMD;
486 DenseMap<AllocaInst *, bool> ProcessedAllocas;
488 friend struct FunctionStackPoisoner;
491 class AddressSanitizerModule : public ModulePass {
493 explicit AddressSanitizerModule(bool CompileKernel = false)
494 : ModulePass(ID), CompileKernel(CompileKernel || ClEnableKasan) {}
495 bool runOnModule(Module &M) override;
496 static char ID; // Pass identification, replacement for typeid
497 const char *getPassName() const override { return "AddressSanitizerModule"; }
500 void initializeCallbacks(Module &M);
502 bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
503 bool ShouldInstrumentGlobal(GlobalVariable *G);
504 void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
505 void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
506 size_t MinRedzoneSizeForGlobal() const {
507 return RedzoneSizeForScale(Mapping.Scale);
510 GlobalsMetadata GlobalsMD;
515 ShadowMapping Mapping;
516 Function *AsanPoisonGlobals;
517 Function *AsanUnpoisonGlobals;
518 Function *AsanRegisterGlobals;
519 Function *AsanUnregisterGlobals;
522 // Stack poisoning does not play well with exception handling.
523 // When an exception is thrown, we essentially bypass the code
524 // that unpoisones the stack. This is why the run-time library has
525 // to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
526 // stack in the interceptor. This however does not work inside the
527 // actual function which catches the exception. Most likely because the
528 // compiler hoists the load of the shadow value somewhere too high.
529 // This causes asan to report a non-existing bug on 453.povray.
530 // It sounds like an LLVM bug.
531 struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
533 AddressSanitizer &ASan;
538 ShadowMapping Mapping;
540 SmallVector<AllocaInst *, 16> AllocaVec;
541 SmallVector<AllocaInst *, 16> NonInstrumentedStaticAllocaVec;
542 SmallVector<Instruction *, 8> RetVec;
543 unsigned StackAlignment;
545 Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
546 *AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
547 Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc;
548 Function *AsanAllocaPoisonFunc, *AsanAllocasUnpoisonFunc;
550 // Stores a place and arguments of poisoning/unpoisoning call for alloca.
551 struct AllocaPoisonCall {
552 IntrinsicInst *InsBefore;
557 SmallVector<AllocaPoisonCall, 8> AllocaPoisonCallVec;
559 SmallVector<AllocaInst *, 1> DynamicAllocaVec;
560 SmallVector<IntrinsicInst *, 1> StackRestoreVec;
561 AllocaInst *DynamicAllocaLayout = nullptr;
562 IntrinsicInst *LocalEscapeCall = nullptr;
564 // Maps Value to an AllocaInst from which the Value is originated.
565 typedef DenseMap<Value *, AllocaInst *> AllocaForValueMapTy;
566 AllocaForValueMapTy AllocaForValue;
568 bool HasNonEmptyInlineAsm;
569 std::unique_ptr<CallInst> EmptyInlineAsm;
571 FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
574 DIB(*F.getParent(), /*AllowUnresolved*/ false),
576 IntptrTy(ASan.IntptrTy),
577 IntptrPtrTy(PointerType::get(IntptrTy, 0)),
578 Mapping(ASan.Mapping),
579 StackAlignment(1 << Mapping.Scale),
580 HasNonEmptyInlineAsm(false),
581 EmptyInlineAsm(CallInst::Create(ASan.EmptyAsm)) {}
583 bool runOnFunction() {
584 if (!ClStack) return false;
585 // Collect alloca, ret, lifetime instructions etc.
586 for (BasicBlock *BB : depth_first(&F.getEntryBlock())) visit(*BB);
588 if (AllocaVec.empty() && DynamicAllocaVec.empty()) return false;
590 initializeCallbacks(*F.getParent());
600 // Finds all Alloca instructions and puts
601 // poisoned red zones around all of them.
602 // Then unpoison everything back before the function returns.
605 void createDynamicAllocasInitStorage();
607 // ----------------------- Visitors.
608 /// \brief Collect all Ret instructions.
609 void visitReturnInst(ReturnInst &RI) { RetVec.push_back(&RI); }
611 void unpoisonDynamicAllocasBeforeInst(Instruction *InstBefore,
613 IRBuilder<> IRB(InstBefore);
614 IRB.CreateCall(AsanAllocasUnpoisonFunc,
615 {IRB.CreateLoad(DynamicAllocaLayout),
616 IRB.CreatePtrToInt(SavedStack, IntptrTy)});
619 // Unpoison dynamic allocas redzones.
620 void unpoisonDynamicAllocas() {
621 for (auto &Ret : RetVec)
622 unpoisonDynamicAllocasBeforeInst(Ret, DynamicAllocaLayout);
624 for (auto &StackRestoreInst : StackRestoreVec)
625 unpoisonDynamicAllocasBeforeInst(StackRestoreInst,
626 StackRestoreInst->getOperand(0));
629 // Deploy and poison redzones around dynamic alloca call. To do this, we
630 // should replace this call with another one with changed parameters and
631 // replace all its uses with new address, so
632 // addr = alloca type, old_size, align
634 // new_size = (old_size + additional_size) * sizeof(type)
635 // tmp = alloca i8, new_size, max(align, 32)
636 // addr = tmp + 32 (first 32 bytes are for the left redzone).
637 // Additional_size is added to make new memory allocation contain not only
638 // requested memory, but also left, partial and right redzones.
639 void handleDynamicAllocaCall(AllocaInst *AI);
641 /// \brief Collect Alloca instructions we want (and can) handle.
642 void visitAllocaInst(AllocaInst &AI) {
643 if (!ASan.isInterestingAlloca(AI)) {
644 if (AI.isStaticAlloca()) NonInstrumentedStaticAllocaVec.push_back(&AI);
648 StackAlignment = std::max(StackAlignment, AI.getAlignment());
649 if (ASan.isDynamicAlloca(AI))
650 DynamicAllocaVec.push_back(&AI);
652 AllocaVec.push_back(&AI);
655 /// \brief Collect lifetime intrinsic calls to check for use-after-scope
657 void visitIntrinsicInst(IntrinsicInst &II) {
658 Intrinsic::ID ID = II.getIntrinsicID();
659 if (ID == Intrinsic::stackrestore) StackRestoreVec.push_back(&II);
660 if (ID == Intrinsic::localescape) LocalEscapeCall = &II;
661 if (!ClCheckLifetime) return;
662 if (ID != Intrinsic::lifetime_start && ID != Intrinsic::lifetime_end)
664 // Found lifetime intrinsic, add ASan instrumentation if necessary.
665 ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
666 // If size argument is undefined, don't do anything.
667 if (Size->isMinusOne()) return;
668 // Check that size doesn't saturate uint64_t and can
669 // be stored in IntptrTy.
670 const uint64_t SizeValue = Size->getValue().getLimitedValue();
671 if (SizeValue == ~0ULL ||
672 !ConstantInt::isValueValidForType(IntptrTy, SizeValue))
674 // Find alloca instruction that corresponds to llvm.lifetime argument.
675 AllocaInst *AI = findAllocaForValue(II.getArgOperand(1));
677 bool DoPoison = (ID == Intrinsic::lifetime_end);
678 AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};
679 AllocaPoisonCallVec.push_back(APC);
682 void visitCallInst(CallInst &CI) {
683 HasNonEmptyInlineAsm |=
684 CI.isInlineAsm() && !CI.isIdenticalTo(EmptyInlineAsm.get());
687 // ---------------------- Helpers.
688 void initializeCallbacks(Module &M);
690 bool doesDominateAllExits(const Instruction *I) const {
691 for (auto Ret : RetVec) {
692 if (!ASan.getDominatorTree().dominates(I, Ret)) return false;
697 /// Finds alloca where the value comes from.
698 AllocaInst *findAllocaForValue(Value *V);
699 void poisonRedZones(ArrayRef<uint8_t> ShadowBytes, IRBuilder<> &IRB,
700 Value *ShadowBase, bool DoPoison);
701 void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison);
703 void SetShadowToStackAfterReturnInlined(IRBuilder<> &IRB, Value *ShadowBase,
705 Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L,
707 PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue,
708 Instruction *ThenTerm, Value *ValueIfFalse);
713 char AddressSanitizer::ID = 0;
714 INITIALIZE_PASS_BEGIN(
715 AddressSanitizer, "asan",
716 "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
718 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
720 AddressSanitizer, "asan",
721 "AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
723 FunctionPass *llvm::createAddressSanitizerFunctionPass(bool CompileKernel) {
724 return new AddressSanitizer(CompileKernel);
727 char AddressSanitizerModule::ID = 0;
729 AddressSanitizerModule, "asan-module",
730 "AddressSanitizer: detects use-after-free and out-of-bounds bugs."
733 ModulePass *llvm::createAddressSanitizerModulePass(bool CompileKernel) {
734 return new AddressSanitizerModule(CompileKernel);
737 static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
738 size_t Res = countTrailingZeros(TypeSize / 8);
739 assert(Res < kNumberOfAccessSizes);
743 // \brief Create a constant for Str so that we can pass it to the run-time lib.
744 static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
746 Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
747 // We use private linkage for module-local strings. If they can be merged
748 // with another one, we set the unnamed_addr attribute.
750 new GlobalVariable(M, StrConst->getType(), true,
751 GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix);
752 if (AllowMerging) GV->setUnnamedAddr(true);
753 GV->setAlignment(1); // Strings may not be merged w/o setting align 1.
757 /// \brief Create a global describing a source location.
758 static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M,
759 LocationMetadata MD) {
760 Constant *LocData[] = {
761 createPrivateGlobalForString(M, MD.Filename, true),
762 ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo),
763 ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo),
765 auto LocStruct = ConstantStruct::getAnon(LocData);
766 auto GV = new GlobalVariable(M, LocStruct->getType(), true,
767 GlobalValue::PrivateLinkage, LocStruct,
769 GV->setUnnamedAddr(true);
773 static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
774 return G->getName().find(kAsanGenPrefix) == 0 ||
775 G->getName().find(kSanCovGenPrefix) == 0;
778 Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
780 Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
781 if (Mapping.Offset == 0) return Shadow;
782 // (Shadow >> scale) | offset
783 if (Mapping.OrShadowOffset)
784 return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
786 return IRB.CreateAdd(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
789 // Instrument memset/memmove/memcpy
790 void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
792 if (isa<MemTransferInst>(MI)) {
794 isa<MemMoveInst>(MI) ? AsanMemmove : AsanMemcpy,
795 {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
796 IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()),
797 IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
798 } else if (isa<MemSetInst>(MI)) {
801 {IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
802 IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
803 IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
805 MI->eraseFromParent();
808 /// Check if we want (and can) handle this alloca.
809 bool AddressSanitizer::isInterestingAlloca(AllocaInst &AI) {
810 auto PreviouslySeenAllocaInfo = ProcessedAllocas.find(&AI);
812 if (PreviouslySeenAllocaInfo != ProcessedAllocas.end())
813 return PreviouslySeenAllocaInfo->getSecond();
816 (AI.getAllocatedType()->isSized() &&
817 // alloca() may be called with 0 size, ignore it.
818 getAllocaSizeInBytes(&AI) > 0 &&
819 // We are only interested in allocas not promotable to registers.
820 // Promotable allocas are common under -O0.
821 (!ClSkipPromotableAllocas || !isAllocaPromotable(&AI) ||
822 isDynamicAlloca(AI)));
824 ProcessedAllocas[&AI] = IsInteresting;
825 return IsInteresting;
828 /// If I is an interesting memory access, return the PointerOperand
829 /// and set IsWrite/Alignment. Otherwise return nullptr.
830 Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I,
833 unsigned *Alignment) {
834 // Skip memory accesses inserted by another instrumentation.
835 if (I->getMetadata("nosanitize")) return nullptr;
837 Value *PtrOperand = nullptr;
838 const DataLayout &DL = I->getModule()->getDataLayout();
839 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
840 if (!ClInstrumentReads) return nullptr;
842 *TypeSize = DL.getTypeStoreSizeInBits(LI->getType());
843 *Alignment = LI->getAlignment();
844 PtrOperand = LI->getPointerOperand();
845 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
846 if (!ClInstrumentWrites) return nullptr;
848 *TypeSize = DL.getTypeStoreSizeInBits(SI->getValueOperand()->getType());
849 *Alignment = SI->getAlignment();
850 PtrOperand = SI->getPointerOperand();
851 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
852 if (!ClInstrumentAtomics) return nullptr;
854 *TypeSize = DL.getTypeStoreSizeInBits(RMW->getValOperand()->getType());
856 PtrOperand = RMW->getPointerOperand();
857 } else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
858 if (!ClInstrumentAtomics) return nullptr;
860 *TypeSize = DL.getTypeStoreSizeInBits(XCHG->getCompareOperand()->getType());
862 PtrOperand = XCHG->getPointerOperand();
865 // Treat memory accesses to promotable allocas as non-interesting since they
866 // will not cause memory violations. This greatly speeds up the instrumented
867 // executable at -O0.
868 if (ClSkipPromotableAllocas)
869 if (auto AI = dyn_cast_or_null<AllocaInst>(PtrOperand))
870 return isInterestingAlloca(*AI) ? AI : nullptr;
875 static bool isPointerOperand(Value *V) {
876 return V->getType()->isPointerTy() || isa<PtrToIntInst>(V);
879 // This is a rough heuristic; it may cause both false positives and
880 // false negatives. The proper implementation requires cooperation with
882 static bool isInterestingPointerComparisonOrSubtraction(Instruction *I) {
883 if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
884 if (!Cmp->isRelational()) return false;
885 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
886 if (BO->getOpcode() != Instruction::Sub) return false;
890 if (!isPointerOperand(I->getOperand(0)) ||
891 !isPointerOperand(I->getOperand(1)))
896 bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) {
897 // If a global variable does not have dynamic initialization we don't
898 // have to instrument it. However, if a global does not have initializer
899 // at all, we assume it has dynamic initializer (in other TU).
900 return G->hasInitializer() && !GlobalsMD.get(G).IsDynInit;
903 void AddressSanitizer::instrumentPointerComparisonOrSubtraction(
906 Function *F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction;
907 Value *Param[2] = {I->getOperand(0), I->getOperand(1)};
908 for (int i = 0; i < 2; i++) {
909 if (Param[i]->getType()->isPointerTy())
910 Param[i] = IRB.CreatePointerCast(Param[i], IntptrTy);
912 IRB.CreateCall(F, Param);
915 void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
916 Instruction *I, bool UseCalls,
917 const DataLayout &DL) {
918 bool IsWrite = false;
919 unsigned Alignment = 0;
920 uint64_t TypeSize = 0;
921 Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment);
924 // Optimization experiments.
925 // The experiments can be used to evaluate potential optimizations that remove
926 // instrumentation (assess false negatives). Instead of completely removing
927 // some instrumentation, you set Exp to a non-zero value (mask of optimization
928 // experiments that want to remove instrumentation of this instruction).
929 // If Exp is non-zero, this pass will emit special calls into runtime
930 // (e.g. __asan_report_exp_load1 instead of __asan_report_load1). These calls
931 // make runtime terminate the program in a special way (with a different
932 // exit status). Then you run the new compiler on a buggy corpus, collect
933 // the special terminations (ideally, you don't see them at all -- no false
934 // negatives) and make the decision on the optimization.
935 uint32_t Exp = ClForceExperiment;
937 if (ClOpt && ClOptGlobals) {
938 // If initialization order checking is disabled, a simple access to a
939 // dynamically initialized global is always valid.
940 GlobalVariable *G = dyn_cast<GlobalVariable>(GetUnderlyingObject(Addr, DL));
941 if (G != NULL && (!ClInitializers || GlobalIsLinkerInitialized(G)) &&
942 isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
943 NumOptimizedAccessesToGlobalVar++;
948 if (ClOpt && ClOptStack) {
949 // A direct inbounds access to a stack variable is always valid.
950 if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
951 isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
952 NumOptimizedAccessesToStackVar++;
958 NumInstrumentedWrites++;
960 NumInstrumentedReads++;
962 unsigned Granularity = 1 << Mapping.Scale;
963 // Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
964 // if the data is properly aligned.
965 if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
967 (Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
968 return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls,
970 instrumentUnusualSizeOrAlignment(I, Addr, TypeSize, IsWrite, nullptr,
974 Instruction *AddressSanitizer::generateCrashCode(Instruction *InsertBefore,
975 Value *Addr, bool IsWrite,
976 size_t AccessSizeIndex,
979 IRBuilder<> IRB(InsertBefore);
980 Value *ExpVal = Exp == 0 ? nullptr : ConstantInt::get(IRB.getInt32Ty(), Exp);
981 CallInst *Call = nullptr;
984 Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][0],
985 {Addr, SizeArgument});
987 Call = IRB.CreateCall(AsanErrorCallbackSized[IsWrite][1],
988 {Addr, SizeArgument, ExpVal});
992 IRB.CreateCall(AsanErrorCallback[IsWrite][0][AccessSizeIndex], Addr);
994 Call = IRB.CreateCall(AsanErrorCallback[IsWrite][1][AccessSizeIndex],
998 // We don't do Call->setDoesNotReturn() because the BB already has
999 // UnreachableInst at the end.
1000 // This EmptyAsm is required to avoid callback merge.
1001 IRB.CreateCall(EmptyAsm, {});
1005 Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
1007 uint32_t TypeSize) {
1008 size_t Granularity = 1 << Mapping.Scale;
1009 // Addr & (Granularity - 1)
1010 Value *LastAccessedByte =
1011 IRB.CreateAnd(AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
1012 // (Addr & (Granularity - 1)) + size - 1
1013 if (TypeSize / 8 > 1)
1014 LastAccessedByte = IRB.CreateAdd(
1015 LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
1016 // (uint8_t) ((Addr & (Granularity-1)) + size - 1)
1018 IRB.CreateIntCast(LastAccessedByte, ShadowValue->getType(), false);
1019 // ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
1020 return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
1023 void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
1024 Instruction *InsertBefore, Value *Addr,
1025 uint32_t TypeSize, bool IsWrite,
1026 Value *SizeArgument, bool UseCalls,
1028 IRBuilder<> IRB(InsertBefore);
1029 Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
1030 size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
1034 IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][0][AccessSizeIndex],
1037 IRB.CreateCall(AsanMemoryAccessCallback[IsWrite][1][AccessSizeIndex],
1038 {AddrLong, ConstantInt::get(IRB.getInt32Ty(), Exp)});
1043 IntegerType::get(*C, std::max(8U, TypeSize >> Mapping.Scale));
1044 Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
1045 Value *ShadowPtr = memToShadow(AddrLong, IRB);
1046 Value *CmpVal = Constant::getNullValue(ShadowTy);
1047 Value *ShadowValue =
1048 IRB.CreateLoad(IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
1050 Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
1051 size_t Granularity = 1 << Mapping.Scale;
1052 TerminatorInst *CrashTerm = nullptr;
1054 if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) {
1055 // We use branch weights for the slow path check, to indicate that the slow
1056 // path is rarely taken. This seems to be the case for SPEC benchmarks.
1057 TerminatorInst *CheckTerm = SplitBlockAndInsertIfThen(
1058 Cmp, InsertBefore, false, MDBuilder(*C).createBranchWeights(1, 100000));
1059 assert(cast<BranchInst>(CheckTerm)->isUnconditional());
1060 BasicBlock *NextBB = CheckTerm->getSuccessor(0);
1061 IRB.SetInsertPoint(CheckTerm);
1062 Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
1063 BasicBlock *CrashBlock =
1064 BasicBlock::Create(*C, "", NextBB->getParent(), NextBB);
1065 CrashTerm = new UnreachableInst(*C, CrashBlock);
1066 BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
1067 ReplaceInstWithInst(CheckTerm, NewTerm);
1069 CrashTerm = SplitBlockAndInsertIfThen(Cmp, InsertBefore, true);
1072 Instruction *Crash = generateCrashCode(CrashTerm, AddrLong, IsWrite,
1073 AccessSizeIndex, SizeArgument, Exp);
1074 Crash->setDebugLoc(OrigIns->getDebugLoc());
1077 // Instrument unusual size or unusual alignment.
1078 // We can not do it with a single check, so we do 1-byte check for the first
1079 // and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
1080 // to report the actual access size.
1081 void AddressSanitizer::instrumentUnusualSizeOrAlignment(
1082 Instruction *I, Value *Addr, uint32_t TypeSize, bool IsWrite,
1083 Value *SizeArgument, bool UseCalls, uint32_t Exp) {
1085 Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8);
1086 Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
1089 IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][0],
1092 IRB.CreateCall(AsanMemoryAccessCallbackSized[IsWrite][1],
1093 {AddrLong, Size, ConstantInt::get(IRB.getInt32Ty(), Exp)});
1095 Value *LastByte = IRB.CreateIntToPtr(
1096 IRB.CreateAdd(AddrLong, ConstantInt::get(IntptrTy, TypeSize / 8 - 1)),
1098 instrumentAddress(I, I, Addr, 8, IsWrite, Size, false, Exp);
1099 instrumentAddress(I, I, LastByte, 8, IsWrite, Size, false, Exp);
1103 void AddressSanitizerModule::poisonOneInitializer(Function &GlobalInit,
1104 GlobalValue *ModuleName) {
1105 // Set up the arguments to our poison/unpoison functions.
1106 IRBuilder<> IRB(GlobalInit.begin()->getFirstInsertionPt());
1108 // Add a call to poison all external globals before the given function starts.
1109 Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
1110 IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
1112 // Add calls to unpoison all globals before each return instruction.
1113 for (auto &BB : GlobalInit.getBasicBlockList())
1114 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB.getTerminator()))
1115 CallInst::Create(AsanUnpoisonGlobals, "", RI);
1118 void AddressSanitizerModule::createInitializerPoisonCalls(
1119 Module &M, GlobalValue *ModuleName) {
1120 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
1122 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
1123 for (Use &OP : CA->operands()) {
1124 if (isa<ConstantAggregateZero>(OP)) continue;
1125 ConstantStruct *CS = cast<ConstantStruct>(OP);
1127 // Must have a function or null ptr.
1128 if (Function *F = dyn_cast<Function>(CS->getOperand(1))) {
1129 if (F->getName() == kAsanModuleCtorName) continue;
1130 ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
1131 // Don't instrument CTORs that will run before asan.module_ctor.
1132 if (Priority->getLimitedValue() <= kAsanCtorAndDtorPriority) continue;
1133 poisonOneInitializer(*F, ModuleName);
1138 bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
1139 Type *Ty = cast<PointerType>(G->getType())->getElementType();
1140 DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
1142 if (GlobalsMD.get(G).IsBlacklisted) return false;
1143 if (!Ty->isSized()) return false;
1144 if (!G->hasInitializer()) return false;
1145 if (GlobalWasGeneratedByAsan(G)) return false; // Our own global.
1146 // Touch only those globals that will not be defined in other modules.
1147 // Don't handle ODR linkage types and COMDATs since other modules may be built
1149 if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
1150 G->getLinkage() != GlobalVariable::PrivateLinkage &&
1151 G->getLinkage() != GlobalVariable::InternalLinkage)
1153 if (G->hasComdat()) return false;
1154 // Two problems with thread-locals:
1155 // - The address of the main thread's copy can't be computed at link-time.
1156 // - Need to poison all copies, not just the main thread's one.
1157 if (G->isThreadLocal()) return false;
1158 // For now, just ignore this Global if the alignment is large.
1159 if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
1161 if (G->hasSection()) {
1162 StringRef Section(G->getSection());
1164 // Globals from llvm.metadata aren't emitted, do not instrument them.
1165 if (Section == "llvm.metadata") return false;
1166 // Do not instrument globals from special LLVM sections.
1167 if (Section.find("__llvm") != StringRef::npos) return false;
1169 // Callbacks put into the CRT initializer/terminator sections
1170 // should not be instrumented.
1171 // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
1172 // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
1173 if (Section.startswith(".CRT")) {
1174 DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
1178 if (TargetTriple.isOSBinFormatMachO()) {
1179 StringRef ParsedSegment, ParsedSection;
1180 unsigned TAA = 0, StubSize = 0;
1182 std::string ErrorCode = MCSectionMachO::ParseSectionSpecifier(
1183 Section, ParsedSegment, ParsedSection, TAA, TAAParsed, StubSize);
1184 if (!ErrorCode.empty()) {
1185 assert(false && "Invalid section specifier.");
1189 // Ignore the globals from the __OBJC section. The ObjC runtime assumes
1190 // those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
1192 if (ParsedSegment == "__OBJC" ||
1193 (ParsedSegment == "__DATA" && ParsedSection.startswith("__objc_"))) {
1194 DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G << "\n");
1197 // See http://code.google.com/p/address-sanitizer/issues/detail?id=32
1198 // Constant CFString instances are compiled in the following way:
1199 // -- the string buffer is emitted into
1200 // __TEXT,__cstring,cstring_literals
1201 // -- the constant NSConstantString structure referencing that buffer
1202 // is placed into __DATA,__cfstring
1203 // Therefore there's no point in placing redzones into __DATA,__cfstring.
1204 // Moreover, it causes the linker to crash on OS X 10.7
1205 if (ParsedSegment == "__DATA" && ParsedSection == "__cfstring") {
1206 DEBUG(dbgs() << "Ignoring CFString: " << *G << "\n");
1209 // The linker merges the contents of cstring_literals and removes the
1211 if (ParsedSegment == "__TEXT" && (TAA & MachO::S_CSTRING_LITERALS)) {
1212 DEBUG(dbgs() << "Ignoring a cstring literal: " << *G << "\n");
1221 void AddressSanitizerModule::initializeCallbacks(Module &M) {
1222 IRBuilder<> IRB(*C);
1223 // Declare our poisoning and unpoisoning functions.
1224 AsanPoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1225 kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, nullptr));
1226 AsanPoisonGlobals->setLinkage(Function::ExternalLinkage);
1227 AsanUnpoisonGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1228 kAsanUnpoisonGlobalsName, IRB.getVoidTy(), nullptr));
1229 AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
1230 // Declare functions that register/unregister globals.
1231 AsanRegisterGlobals = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1232 kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1233 AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
1234 AsanUnregisterGlobals = checkSanitizerInterfaceFunction(
1235 M.getOrInsertFunction(kAsanUnregisterGlobalsName, IRB.getVoidTy(),
1236 IntptrTy, IntptrTy, nullptr));
1237 AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
1240 // This function replaces all global variables with new variables that have
1241 // trailing redzones. It also creates a function that poisons
1242 // redzones and inserts this function into llvm.global_ctors.
1243 bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
1246 SmallVector<GlobalVariable *, 16> GlobalsToChange;
1248 for (auto &G : M.globals()) {
1249 if (ShouldInstrumentGlobal(&G)) GlobalsToChange.push_back(&G);
1252 size_t n = GlobalsToChange.size();
1253 if (n == 0) return false;
1255 // A global is described by a structure
1258 // size_t size_with_redzone;
1259 // const char *name;
1260 // const char *module_name;
1261 // size_t has_dynamic_init;
1262 // void *source_location;
1263 // We initialize an array of such structures and pass it to a run-time call.
1264 StructType *GlobalStructTy =
1265 StructType::get(IntptrTy, IntptrTy, IntptrTy, IntptrTy, IntptrTy,
1266 IntptrTy, IntptrTy, nullptr);
1267 SmallVector<Constant *, 16> Initializers(n);
1269 bool HasDynamicallyInitializedGlobals = false;
1271 // We shouldn't merge same module names, as this string serves as unique
1272 // module ID in runtime.
1273 GlobalVariable *ModuleName = createPrivateGlobalForString(
1274 M, M.getModuleIdentifier(), /*AllowMerging*/ false);
1276 auto &DL = M.getDataLayout();
1277 for (size_t i = 0; i < n; i++) {
1278 static const uint64_t kMaxGlobalRedzone = 1 << 18;
1279 GlobalVariable *G = GlobalsToChange[i];
1281 auto MD = GlobalsMD.get(G);
1282 // Create string holding the global name (use global name from metadata
1283 // if it's available, otherwise just write the name of global variable).
1284 GlobalVariable *Name = createPrivateGlobalForString(
1285 M, MD.Name.empty() ? G->getName() : MD.Name,
1286 /*AllowMerging*/ true);
1288 PointerType *PtrTy = cast<PointerType>(G->getType());
1289 Type *Ty = PtrTy->getElementType();
1290 uint64_t SizeInBytes = DL.getTypeAllocSize(Ty);
1291 uint64_t MinRZ = MinRedzoneSizeForGlobal();
1292 // MinRZ <= RZ <= kMaxGlobalRedzone
1293 // and trying to make RZ to be ~ 1/4 of SizeInBytes.
1294 uint64_t RZ = std::max(
1295 MinRZ, std::min(kMaxGlobalRedzone, (SizeInBytes / MinRZ / 4) * MinRZ));
1296 uint64_t RightRedzoneSize = RZ;
1297 // Round up to MinRZ
1298 if (SizeInBytes % MinRZ) RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
1299 assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
1300 Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
1302 StructType *NewTy = StructType::get(Ty, RightRedZoneTy, nullptr);
1303 Constant *NewInitializer =
1304 ConstantStruct::get(NewTy, G->getInitializer(),
1305 Constant::getNullValue(RightRedZoneTy), nullptr);
1307 // Create a new global variable with enough space for a redzone.
1308 GlobalValue::LinkageTypes Linkage = G->getLinkage();
1309 if (G->isConstant() && Linkage == GlobalValue::PrivateLinkage)
1310 Linkage = GlobalValue::InternalLinkage;
1311 GlobalVariable *NewGlobal =
1312 new GlobalVariable(M, NewTy, G->isConstant(), Linkage, NewInitializer,
1313 "", G, G->getThreadLocalMode());
1314 NewGlobal->copyAttributesFrom(G);
1315 NewGlobal->setAlignment(MinRZ);
1318 Indices2[0] = IRB.getInt32(0);
1319 Indices2[1] = IRB.getInt32(0);
1321 G->replaceAllUsesWith(
1322 ConstantExpr::getGetElementPtr(NewTy, NewGlobal, Indices2, true));
1323 NewGlobal->takeName(G);
1324 G->eraseFromParent();
1326 Constant *SourceLoc;
1327 if (!MD.SourceLoc.empty()) {
1328 auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc);
1329 SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy);
1331 SourceLoc = ConstantInt::get(IntptrTy, 0);
1334 Initializers[i] = ConstantStruct::get(
1335 GlobalStructTy, ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
1336 ConstantInt::get(IntptrTy, SizeInBytes),
1337 ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
1338 ConstantExpr::getPointerCast(Name, IntptrTy),
1339 ConstantExpr::getPointerCast(ModuleName, IntptrTy),
1340 ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc, nullptr);
1342 if (ClInitializers && MD.IsDynInit) HasDynamicallyInitializedGlobals = true;
1344 DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
1347 ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
1348 GlobalVariable *AllGlobals = new GlobalVariable(
1349 M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
1350 ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
1352 // Create calls for poisoning before initializers run and unpoisoning after.
1353 if (HasDynamicallyInitializedGlobals)
1354 createInitializerPoisonCalls(M, ModuleName);
1355 IRB.CreateCall(AsanRegisterGlobals,
1356 {IRB.CreatePointerCast(AllGlobals, IntptrTy),
1357 ConstantInt::get(IntptrTy, n)});
1359 // We also need to unregister globals at the end, e.g. when a shared library
1361 Function *AsanDtorFunction =
1362 Function::Create(FunctionType::get(Type::getVoidTy(*C), false),
1363 GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
1364 BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
1365 IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
1366 IRB_Dtor.CreateCall(AsanUnregisterGlobals,
1367 {IRB.CreatePointerCast(AllGlobals, IntptrTy),
1368 ConstantInt::get(IntptrTy, n)});
1369 appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndDtorPriority);
1375 bool AddressSanitizerModule::runOnModule(Module &M) {
1376 C = &(M.getContext());
1377 int LongSize = M.getDataLayout().getPointerSizeInBits();
1378 IntptrTy = Type::getIntNTy(*C, LongSize);
1379 TargetTriple = Triple(M.getTargetTriple());
1380 Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
1381 initializeCallbacks(M);
1383 bool Changed = false;
1385 // TODO(glider): temporarily disabled globals instrumentation for KASan.
1386 if (ClGlobals && !CompileKernel) {
1387 Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
1389 IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
1390 Changed |= InstrumentGlobals(IRB, M);
1396 void AddressSanitizer::initializeCallbacks(Module &M) {
1397 IRBuilder<> IRB(*C);
1398 // Create __asan_report* callbacks.
1399 // IsWrite, TypeSize and Exp are encoded in the function name.
1400 for (int Exp = 0; Exp < 2; Exp++) {
1401 for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
1402 const std::string TypeStr = AccessIsWrite ? "store" : "load";
1403 const std::string ExpStr = Exp ? "exp_" : "";
1404 const std::string SuffixStr = CompileKernel ? "N" : "_n";
1405 const std::string EndingStr = CompileKernel ? "_noabort" : "";
1406 const Type *ExpType = Exp ? Type::getInt32Ty(*C) : nullptr;
1407 // TODO(glider): for KASan builds add _noabort to error reporting
1408 // functions and make them actually noabort (remove the UnreachableInst).
1409 AsanErrorCallbackSized[AccessIsWrite][Exp] =
1410 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1411 kAsanReportErrorTemplate + ExpStr + TypeStr + SuffixStr,
1412 IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr));
1413 AsanMemoryAccessCallbackSized[AccessIsWrite][Exp] =
1414 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1415 ClMemoryAccessCallbackPrefix + ExpStr + TypeStr + "N" + EndingStr,
1416 IRB.getVoidTy(), IntptrTy, IntptrTy, ExpType, nullptr));
1417 for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
1418 AccessSizeIndex++) {
1419 const std::string Suffix = TypeStr + itostr(1 << AccessSizeIndex);
1420 AsanErrorCallback[AccessIsWrite][Exp][AccessSizeIndex] =
1421 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1422 kAsanReportErrorTemplate + ExpStr + Suffix,
1423 IRB.getVoidTy(), IntptrTy, ExpType, nullptr));
1424 AsanMemoryAccessCallback[AccessIsWrite][Exp][AccessSizeIndex] =
1425 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1426 ClMemoryAccessCallbackPrefix + ExpStr + Suffix + EndingStr,
1427 IRB.getVoidTy(), IntptrTy, ExpType, nullptr));
1432 const std::string MemIntrinCallbackPrefix =
1433 CompileKernel ? std::string("") : ClMemoryAccessCallbackPrefix;
1434 AsanMemmove = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1435 MemIntrinCallbackPrefix + "memmove", IRB.getInt8PtrTy(),
1436 IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
1437 AsanMemcpy = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1438 MemIntrinCallbackPrefix + "memcpy", IRB.getInt8PtrTy(),
1439 IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), IntptrTy, nullptr));
1440 AsanMemset = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1441 MemIntrinCallbackPrefix + "memset", IRB.getInt8PtrTy(),
1442 IRB.getInt8PtrTy(), IRB.getInt32Ty(), IntptrTy, nullptr));
1444 AsanHandleNoReturnFunc = checkSanitizerInterfaceFunction(
1445 M.getOrInsertFunction(kAsanHandleNoReturnName, IRB.getVoidTy(), nullptr));
1447 AsanPtrCmpFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1448 kAsanPtrCmp, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1449 AsanPtrSubFunction = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1450 kAsanPtrSub, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1451 // We insert an empty inline asm after __asan_report* to avoid callback merge.
1452 EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
1453 StringRef(""), StringRef(""),
1454 /*hasSideEffects=*/true);
1458 bool AddressSanitizer::doInitialization(Module &M) {
1459 // Initialize the private fields. No one has accessed them before.
1463 C = &(M.getContext());
1464 LongSize = M.getDataLayout().getPointerSizeInBits();
1465 IntptrTy = Type::getIntNTy(*C, LongSize);
1466 TargetTriple = Triple(M.getTargetTriple());
1468 if (!CompileKernel) {
1469 std::tie(AsanCtorFunction, AsanInitFunction) =
1470 createSanitizerCtorAndInitFunctions(M, kAsanModuleCtorName, kAsanInitName,
1471 /*InitArgTypes=*/{},
1473 appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndDtorPriority);
1475 Mapping = getShadowMapping(TargetTriple, LongSize, CompileKernel);
1479 bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
1480 // For each NSObject descendant having a +load method, this method is invoked
1481 // by the ObjC runtime before any of the static constructors is called.
1482 // Therefore we need to instrument such methods with a call to __asan_init
1483 // at the beginning in order to initialize our runtime before any access to
1484 // the shadow memory.
1485 // We cannot just ignore these methods, because they may call other
1486 // instrumented functions.
1487 if (F.getName().find(" load]") != std::string::npos) {
1488 IRBuilder<> IRB(F.begin()->begin());
1489 IRB.CreateCall(AsanInitFunction, {});
1495 void AddressSanitizer::markEscapedLocalAllocas(Function &F) {
1496 // Find the one possible call to llvm.localescape and pre-mark allocas passed
1497 // to it as uninteresting. This assumes we haven't started processing allocas
1498 // yet. This check is done up front because iterating the use list in
1499 // isInterestingAlloca would be algorithmically slower.
1500 assert(ProcessedAllocas.empty() && "must process localescape before allocas");
1502 // Try to get the declaration of llvm.localescape. If it's not in the module,
1503 // we can exit early.
1504 if (!F.getParent()->getFunction("llvm.localescape")) return;
1506 // Look for a call to llvm.localescape call in the entry block. It can't be in
1508 for (Instruction &I : F.getEntryBlock()) {
1509 IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
1510 if (II && II->getIntrinsicID() == Intrinsic::localescape) {
1511 // We found a call. Mark all the allocas passed in as uninteresting.
1512 for (Value *Arg : II->arg_operands()) {
1513 AllocaInst *AI = dyn_cast<AllocaInst>(Arg->stripPointerCasts());
1514 assert(AI && AI->isStaticAlloca() &&
1515 "non-static alloca arg to localescape");
1516 ProcessedAllocas[AI] = false;
1523 bool AddressSanitizer::runOnFunction(Function &F) {
1524 if (&F == AsanCtorFunction) return false;
1525 if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
1526 DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
1527 initializeCallbacks(*F.getParent());
1529 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1531 // If needed, insert __asan_init before checking for SanitizeAddress attr.
1532 maybeInsertAsanInitAtFunctionEntry(F);
1534 if (!F.hasFnAttribute(Attribute::SanitizeAddress)) return false;
1536 if (!ClDebugFunc.empty() && ClDebugFunc != F.getName()) return false;
1538 FunctionStateRAII CleanupObj(this);
1540 // We can't instrument allocas used with llvm.localescape. Only static allocas
1541 // can be passed to that intrinsic.
1542 markEscapedLocalAllocas(F);
1544 // We want to instrument every address only once per basic block (unless there
1545 // are calls between uses).
1546 SmallSet<Value *, 16> TempsToInstrument;
1547 SmallVector<Instruction *, 16> ToInstrument;
1548 SmallVector<Instruction *, 8> NoReturnCalls;
1549 SmallVector<BasicBlock *, 16> AllBlocks;
1550 SmallVector<Instruction *, 16> PointerComparisonsOrSubtracts;
1556 // Fill the set of memory operations to instrument.
1557 for (auto &BB : F) {
1558 AllBlocks.push_back(&BB);
1559 TempsToInstrument.clear();
1560 int NumInsnsPerBB = 0;
1561 for (auto &Inst : BB) {
1562 if (LooksLikeCodeInBug11395(&Inst)) return false;
1563 if (Value *Addr = isInterestingMemoryAccess(&Inst, &IsWrite, &TypeSize,
1565 if (ClOpt && ClOptSameTemp) {
1566 if (!TempsToInstrument.insert(Addr).second)
1567 continue; // We've seen this temp in the current BB.
1569 } else if (ClInvalidPointerPairs &&
1570 isInterestingPointerComparisonOrSubtraction(&Inst)) {
1571 PointerComparisonsOrSubtracts.push_back(&Inst);
1573 } else if (isa<MemIntrinsic>(Inst)) {
1576 if (isa<AllocaInst>(Inst)) NumAllocas++;
1579 // A call inside BB.
1580 TempsToInstrument.clear();
1581 if (CS.doesNotReturn()) NoReturnCalls.push_back(CS.getInstruction());
1585 ToInstrument.push_back(&Inst);
1587 if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB) break;
1593 (ClInstrumentationWithCallsThreshold >= 0 &&
1594 ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold);
1595 const TargetLibraryInfo *TLI =
1596 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
1597 const DataLayout &DL = F.getParent()->getDataLayout();
1598 ObjectSizeOffsetVisitor ObjSizeVis(DL, TLI, F.getContext(),
1599 /*RoundToAlign=*/true);
1602 int NumInstrumented = 0;
1603 for (auto Inst : ToInstrument) {
1604 if (ClDebugMin < 0 || ClDebugMax < 0 ||
1605 (NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
1606 if (isInterestingMemoryAccess(Inst, &IsWrite, &TypeSize, &Alignment))
1607 instrumentMop(ObjSizeVis, Inst, UseCalls,
1608 F.getParent()->getDataLayout());
1610 instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
1615 FunctionStackPoisoner FSP(F, *this);
1616 bool ChangedStack = FSP.runOnFunction();
1618 // We must unpoison the stack before every NoReturn call (throw, _exit, etc).
1619 // See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
1620 for (auto CI : NoReturnCalls) {
1621 IRBuilder<> IRB(CI);
1622 IRB.CreateCall(AsanHandleNoReturnFunc, {});
1625 for (auto Inst : PointerComparisonsOrSubtracts) {
1626 instrumentPointerComparisonOrSubtraction(Inst);
1630 bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
1632 DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n");
1637 // Workaround for bug 11395: we don't want to instrument stack in functions
1638 // with large assembly blobs (32-bit only), otherwise reg alloc may crash.
1639 // FIXME: remove once the bug 11395 is fixed.
1640 bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
1641 if (LongSize != 32) return false;
1642 CallInst *CI = dyn_cast<CallInst>(I);
1643 if (!CI || !CI->isInlineAsm()) return false;
1644 if (CI->getNumArgOperands() <= 5) return false;
1645 // We have inline assembly with quite a few arguments.
1649 void FunctionStackPoisoner::initializeCallbacks(Module &M) {
1650 IRBuilder<> IRB(*C);
1651 for (int i = 0; i <= kMaxAsanStackMallocSizeClass; i++) {
1652 std::string Suffix = itostr(i);
1653 AsanStackMallocFunc[i] = checkSanitizerInterfaceFunction(
1654 M.getOrInsertFunction(kAsanStackMallocNameTemplate + Suffix, IntptrTy,
1655 IntptrTy, nullptr));
1656 AsanStackFreeFunc[i] = checkSanitizerInterfaceFunction(
1657 M.getOrInsertFunction(kAsanStackFreeNameTemplate + Suffix,
1658 IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1660 AsanPoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
1661 M.getOrInsertFunction(kAsanPoisonStackMemoryName, IRB.getVoidTy(),
1662 IntptrTy, IntptrTy, nullptr));
1663 AsanUnpoisonStackMemoryFunc = checkSanitizerInterfaceFunction(
1664 M.getOrInsertFunction(kAsanUnpoisonStackMemoryName, IRB.getVoidTy(),
1665 IntptrTy, IntptrTy, nullptr));
1666 AsanAllocaPoisonFunc = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1667 kAsanAllocaPoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1668 AsanAllocasUnpoisonFunc =
1669 checkSanitizerInterfaceFunction(M.getOrInsertFunction(
1670 kAsanAllocasUnpoison, IRB.getVoidTy(), IntptrTy, IntptrTy, nullptr));
1673 void FunctionStackPoisoner::poisonRedZones(ArrayRef<uint8_t> ShadowBytes,
1674 IRBuilder<> &IRB, Value *ShadowBase,
1676 size_t n = ShadowBytes.size();
1678 // We need to (un)poison n bytes of stack shadow. Poison as many as we can
1679 // using 64-bit stores (if we are on 64-bit arch), then poison the rest
1680 // with 32-bit stores, then with 16-byte stores, then with 8-byte stores.
1681 for (size_t LargeStoreSizeInBytes = ASan.LongSize / 8;
1682 LargeStoreSizeInBytes != 0; LargeStoreSizeInBytes /= 2) {
1683 for (; i + LargeStoreSizeInBytes - 1 < n; i += LargeStoreSizeInBytes) {
1685 for (size_t j = 0; j < LargeStoreSizeInBytes; j++) {
1686 if (F.getParent()->getDataLayout().isLittleEndian())
1687 Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
1689 Val = (Val << 8) | ShadowBytes[i + j];
1692 Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
1693 Type *StoreTy = Type::getIntNTy(*C, LargeStoreSizeInBytes * 8);
1694 Value *Poison = ConstantInt::get(StoreTy, DoPoison ? Val : 0);
1695 IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, StoreTy->getPointerTo()));
1700 // Fake stack allocator (asan_fake_stack.h) has 11 size classes
1701 // for every power of 2 from kMinStackMallocSize to kMaxAsanStackMallocSizeClass
1702 static int StackMallocSizeClass(uint64_t LocalStackSize) {
1703 assert(LocalStackSize <= kMaxStackMallocSize);
1704 uint64_t MaxSize = kMinStackMallocSize;
1705 for (int i = 0;; i++, MaxSize *= 2)
1706 if (LocalStackSize <= MaxSize) return i;
1707 llvm_unreachable("impossible LocalStackSize");
1710 // Set Size bytes starting from ShadowBase to kAsanStackAfterReturnMagic.
1711 // We can not use MemSet intrinsic because it may end up calling the actual
1712 // memset. Size is a multiple of 8.
1713 // Currently this generates 8-byte stores on x86_64; it may be better to
1714 // generate wider stores.
1715 void FunctionStackPoisoner::SetShadowToStackAfterReturnInlined(
1716 IRBuilder<> &IRB, Value *ShadowBase, int Size) {
1717 assert(!(Size % 8));
1719 // kAsanStackAfterReturnMagic is 0xf5.
1720 const uint64_t kAsanStackAfterReturnMagic64 = 0xf5f5f5f5f5f5f5f5ULL;
1722 for (int i = 0; i < Size; i += 8) {
1723 Value *p = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
1725 ConstantInt::get(IRB.getInt64Ty(), kAsanStackAfterReturnMagic64),
1726 IRB.CreateIntToPtr(p, IRB.getInt64Ty()->getPointerTo()));
1730 PHINode *FunctionStackPoisoner::createPHI(IRBuilder<> &IRB, Value *Cond,
1732 Instruction *ThenTerm,
1733 Value *ValueIfFalse) {
1734 PHINode *PHI = IRB.CreatePHI(IntptrTy, 2);
1735 BasicBlock *CondBlock = cast<Instruction>(Cond)->getParent();
1736 PHI->addIncoming(ValueIfFalse, CondBlock);
1737 BasicBlock *ThenBlock = ThenTerm->getParent();
1738 PHI->addIncoming(ValueIfTrue, ThenBlock);
1742 Value *FunctionStackPoisoner::createAllocaForLayout(
1743 IRBuilder<> &IRB, const ASanStackFrameLayout &L, bool Dynamic) {
1746 Alloca = IRB.CreateAlloca(IRB.getInt8Ty(),
1747 ConstantInt::get(IRB.getInt64Ty(), L.FrameSize),
1750 Alloca = IRB.CreateAlloca(ArrayType::get(IRB.getInt8Ty(), L.FrameSize),
1751 nullptr, "MyAlloca");
1752 assert(Alloca->isStaticAlloca());
1754 assert((ClRealignStack & (ClRealignStack - 1)) == 0);
1755 size_t FrameAlignment = std::max(L.FrameAlignment, (size_t)ClRealignStack);
1756 Alloca->setAlignment(FrameAlignment);
1757 return IRB.CreatePointerCast(Alloca, IntptrTy);
1760 void FunctionStackPoisoner::createDynamicAllocasInitStorage() {
1761 BasicBlock &FirstBB = *F.begin();
1762 IRBuilder<> IRB(dyn_cast<Instruction>(FirstBB.begin()));
1763 DynamicAllocaLayout = IRB.CreateAlloca(IntptrTy, nullptr);
1764 IRB.CreateStore(Constant::getNullValue(IntptrTy), DynamicAllocaLayout);
1765 DynamicAllocaLayout->setAlignment(32);
1768 void FunctionStackPoisoner::poisonStack() {
1769 assert(AllocaVec.size() > 0 || DynamicAllocaVec.size() > 0);
1771 if (ClInstrumentAllocas && DynamicAllocaVec.size() > 0) {
1772 // Handle dynamic allocas.
1773 createDynamicAllocasInitStorage();
1774 for (auto &AI : DynamicAllocaVec) handleDynamicAllocaCall(AI);
1776 unpoisonDynamicAllocas();
1779 if (AllocaVec.size() == 0) return;
1781 int StackMallocIdx = -1;
1782 DebugLoc EntryDebugLocation;
1783 if (auto SP = getDISubprogram(&F))
1784 EntryDebugLocation = DebugLoc::get(SP->getScopeLine(), 0, SP);
1786 Instruction *InsBefore = AllocaVec[0];
1787 IRBuilder<> IRB(InsBefore);
1788 IRB.SetCurrentDebugLocation(EntryDebugLocation);
1790 // Make sure non-instrumented allocas stay in the first basic block.
1791 // Otherwise, debug info is broken, because only first-basic-block allocas are
1792 // treated as regular stack slots.
1793 for (auto *AI : NonInstrumentedStaticAllocaVec) AI->moveBefore(InsBefore);
1795 // If we have a call to llvm.localescape, keep it in the entry block.
1796 if (LocalEscapeCall) LocalEscapeCall->moveBefore(InsBefore);
1798 SmallVector<ASanStackVariableDescription, 16> SVD;
1799 SVD.reserve(AllocaVec.size());
1800 for (AllocaInst *AI : AllocaVec) {
1801 ASanStackVariableDescription D = {AI->getName().data(),
1802 ASan.getAllocaSizeInBytes(AI),
1803 AI->getAlignment(), AI, 0};
1806 // Minimal header size (left redzone) is 4 pointers,
1807 // i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms.
1808 size_t MinHeaderSize = ASan.LongSize / 2;
1809 ASanStackFrameLayout L;
1810 ComputeASanStackFrameLayout(SVD, 1UL << Mapping.Scale, MinHeaderSize, &L);
1811 DEBUG(dbgs() << L.DescriptionString << " --- " << L.FrameSize << "\n");
1812 uint64_t LocalStackSize = L.FrameSize;
1813 bool DoStackMalloc = ClUseAfterReturn && !ASan.CompileKernel &&
1814 LocalStackSize <= kMaxStackMallocSize;
1815 // Don't do dynamic alloca or stack malloc in presence of inline asm:
1816 // too often it makes assumptions on which registers are available.
1817 bool DoDynamicAlloca = ClDynamicAllocaStack && !HasNonEmptyInlineAsm;
1818 DoStackMalloc &= !HasNonEmptyInlineAsm;
1820 Value *StaticAlloca =
1821 DoDynamicAlloca ? nullptr : createAllocaForLayout(IRB, L, false);
1824 Value *LocalStackBase;
1826 if (DoStackMalloc) {
1827 // void *FakeStack = __asan_option_detect_stack_use_after_return
1828 // ? __asan_stack_malloc_N(LocalStackSize)
1830 // void *LocalStackBase = (FakeStack) ? FakeStack : alloca(LocalStackSize);
1831 Constant *OptionDetectUAR = F.getParent()->getOrInsertGlobal(
1832 kAsanOptionDetectUAR, IRB.getInt32Ty());
1833 Value *UARIsEnabled =
1834 IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUAR),
1835 Constant::getNullValue(IRB.getInt32Ty()));
1837 SplitBlockAndInsertIfThen(UARIsEnabled, InsBefore, false);
1838 IRBuilder<> IRBIf(Term);
1839 IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
1840 StackMallocIdx = StackMallocSizeClass(LocalStackSize);
1841 assert(StackMallocIdx <= kMaxAsanStackMallocSizeClass);
1842 Value *FakeStackValue =
1843 IRBIf.CreateCall(AsanStackMallocFunc[StackMallocIdx],
1844 ConstantInt::get(IntptrTy, LocalStackSize));
1845 IRB.SetInsertPoint(InsBefore);
1846 IRB.SetCurrentDebugLocation(EntryDebugLocation);
1847 FakeStack = createPHI(IRB, UARIsEnabled, FakeStackValue, Term,
1848 ConstantInt::get(IntptrTy, 0));
1850 Value *NoFakeStack =
1851 IRB.CreateICmpEQ(FakeStack, Constant::getNullValue(IntptrTy));
1852 Term = SplitBlockAndInsertIfThen(NoFakeStack, InsBefore, false);
1853 IRBIf.SetInsertPoint(Term);
1854 IRBIf.SetCurrentDebugLocation(EntryDebugLocation);
1855 Value *AllocaValue =
1856 DoDynamicAlloca ? createAllocaForLayout(IRBIf, L, true) : StaticAlloca;
1857 IRB.SetInsertPoint(InsBefore);
1858 IRB.SetCurrentDebugLocation(EntryDebugLocation);
1859 LocalStackBase = createPHI(IRB, NoFakeStack, AllocaValue, Term, FakeStack);
1861 // void *FakeStack = nullptr;
1862 // void *LocalStackBase = alloca(LocalStackSize);
1863 FakeStack = ConstantInt::get(IntptrTy, 0);
1865 DoDynamicAlloca ? createAllocaForLayout(IRB, L, true) : StaticAlloca;
1868 // Insert poison calls for lifetime intrinsics for alloca.
1869 bool HavePoisonedAllocas = false;
1870 for (const auto &APC : AllocaPoisonCallVec) {
1871 assert(APC.InsBefore);
1873 IRBuilder<> IRB(APC.InsBefore);
1874 poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison);
1875 HavePoisonedAllocas |= APC.DoPoison;
1878 // Replace Alloca instructions with base+offset.
1879 for (const auto &Desc : SVD) {
1880 AllocaInst *AI = Desc.AI;
1881 Value *NewAllocaPtr = IRB.CreateIntToPtr(
1882 IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Desc.Offset)),
1884 replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB, /*Deref=*/true);
1885 AI->replaceAllUsesWith(NewAllocaPtr);
1888 // The left-most redzone has enough space for at least 4 pointers.
1889 // Write the Magic value to redzone[0].
1890 Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
1891 IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
1893 // Write the frame description constant to redzone[1].
1894 Value *BasePlus1 = IRB.CreateIntToPtr(
1895 IRB.CreateAdd(LocalStackBase,
1896 ConstantInt::get(IntptrTy, ASan.LongSize / 8)),
1898 GlobalVariable *StackDescriptionGlobal =
1899 createPrivateGlobalForString(*F.getParent(), L.DescriptionString,
1900 /*AllowMerging*/ true);
1901 Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal, IntptrTy);
1902 IRB.CreateStore(Description, BasePlus1);
1903 // Write the PC to redzone[2].
1904 Value *BasePlus2 = IRB.CreateIntToPtr(
1905 IRB.CreateAdd(LocalStackBase,
1906 ConstantInt::get(IntptrTy, 2 * ASan.LongSize / 8)),
1908 IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
1910 // Poison the stack redzones at the entry.
1911 Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
1912 poisonRedZones(L.ShadowBytes, IRB, ShadowBase, true);
1914 // (Un)poison the stack before all ret instructions.
1915 for (auto Ret : RetVec) {
1916 IRBuilder<> IRBRet(Ret);
1917 // Mark the current frame as retired.
1918 IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
1920 if (DoStackMalloc) {
1921 assert(StackMallocIdx >= 0);
1922 // if FakeStack != 0 // LocalStackBase == FakeStack
1923 // // In use-after-return mode, poison the whole stack frame.
1924 // if StackMallocIdx <= 4
1925 // // For small sizes inline the whole thing:
1926 // memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize);
1927 // **SavedFlagPtr(FakeStack) = 0
1929 // __asan_stack_free_N(FakeStack, LocalStackSize)
1931 // <This is not a fake stack; unpoison the redzones>
1933 IRBRet.CreateICmpNE(FakeStack, Constant::getNullValue(IntptrTy));
1934 TerminatorInst *ThenTerm, *ElseTerm;
1935 SplitBlockAndInsertIfThenElse(Cmp, Ret, &ThenTerm, &ElseTerm);
1937 IRBuilder<> IRBPoison(ThenTerm);
1938 if (StackMallocIdx <= 4) {
1939 int ClassSize = kMinStackMallocSize << StackMallocIdx;
1940 SetShadowToStackAfterReturnInlined(IRBPoison, ShadowBase,
1941 ClassSize >> Mapping.Scale);
1942 Value *SavedFlagPtrPtr = IRBPoison.CreateAdd(
1944 ConstantInt::get(IntptrTy, ClassSize - ASan.LongSize / 8));
1945 Value *SavedFlagPtr = IRBPoison.CreateLoad(
1946 IRBPoison.CreateIntToPtr(SavedFlagPtrPtr, IntptrPtrTy));
1947 IRBPoison.CreateStore(
1948 Constant::getNullValue(IRBPoison.getInt8Ty()),
1949 IRBPoison.CreateIntToPtr(SavedFlagPtr, IRBPoison.getInt8PtrTy()));
1951 // For larger frames call __asan_stack_free_*.
1952 IRBPoison.CreateCall(
1953 AsanStackFreeFunc[StackMallocIdx],
1954 {FakeStack, ConstantInt::get(IntptrTy, LocalStackSize)});
1957 IRBuilder<> IRBElse(ElseTerm);
1958 poisonRedZones(L.ShadowBytes, IRBElse, ShadowBase, false);
1959 } else if (HavePoisonedAllocas) {
1960 // If we poisoned some allocas in llvm.lifetime analysis,
1961 // unpoison whole stack frame now.
1962 poisonAlloca(LocalStackBase, LocalStackSize, IRBRet, false);
1964 poisonRedZones(L.ShadowBytes, IRBRet, ShadowBase, false);
1968 // We are done. Remove the old unused alloca instructions.
1969 for (auto AI : AllocaVec) AI->eraseFromParent();
1972 void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size,
1973 IRBuilder<> &IRB, bool DoPoison) {
1974 // For now just insert the call to ASan runtime.
1975 Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy);
1976 Value *SizeArg = ConstantInt::get(IntptrTy, Size);
1978 DoPoison ? AsanPoisonStackMemoryFunc : AsanUnpoisonStackMemoryFunc,
1979 {AddrArg, SizeArg});
1982 // Handling llvm.lifetime intrinsics for a given %alloca:
1983 // (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca.
1984 // (2) if %size is constant, poison memory for llvm.lifetime.end (to detect
1985 // invalid accesses) and unpoison it for llvm.lifetime.start (the memory
1986 // could be poisoned by previous llvm.lifetime.end instruction, as the
1987 // variable may go in and out of scope several times, e.g. in loops).
1988 // (3) if we poisoned at least one %alloca in a function,
1989 // unpoison the whole stack frame at function exit.
1991 AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
1992 if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
1993 // We're intested only in allocas we can handle.
1994 return ASan.isInterestingAlloca(*AI) ? AI : nullptr;
1995 // See if we've already calculated (or started to calculate) alloca for a
1997 AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
1998 if (I != AllocaForValue.end()) return I->second;
1999 // Store 0 while we're calculating alloca for value V to avoid
2000 // infinite recursion if the value references itself.
2001 AllocaForValue[V] = nullptr;
2002 AllocaInst *Res = nullptr;
2003 if (CastInst *CI = dyn_cast<CastInst>(V))
2004 Res = findAllocaForValue(CI->getOperand(0));
2005 else if (PHINode *PN = dyn_cast<PHINode>(V)) {
2006 for (Value *IncValue : PN->incoming_values()) {
2007 // Allow self-referencing phi-nodes.
2008 if (IncValue == PN) continue;
2009 AllocaInst *IncValueAI = findAllocaForValue(IncValue);
2010 // AI for incoming values should exist and should all be equal.
2011 if (IncValueAI == nullptr || (Res != nullptr && IncValueAI != Res))
2016 if (Res) AllocaForValue[V] = Res;
2020 void FunctionStackPoisoner::handleDynamicAllocaCall(AllocaInst *AI) {
2021 IRBuilder<> IRB(AI);
2023 const unsigned Align = std::max(kAllocaRzSize, AI->getAlignment());
2024 const uint64_t AllocaRedzoneMask = kAllocaRzSize - 1;
2026 Value *Zero = Constant::getNullValue(IntptrTy);
2027 Value *AllocaRzSize = ConstantInt::get(IntptrTy, kAllocaRzSize);
2028 Value *AllocaRzMask = ConstantInt::get(IntptrTy, AllocaRedzoneMask);
2030 // Since we need to extend alloca with additional memory to locate
2031 // redzones, and OldSize is number of allocated blocks with
2032 // ElementSize size, get allocated memory size in bytes by
2033 // OldSize * ElementSize.
2034 const unsigned ElementSize =
2035 F.getParent()->getDataLayout().getTypeAllocSize(AI->getAllocatedType());
2037 IRB.CreateMul(IRB.CreateIntCast(AI->getArraySize(), IntptrTy, false),
2038 ConstantInt::get(IntptrTy, ElementSize));
2040 // PartialSize = OldSize % 32
2041 Value *PartialSize = IRB.CreateAnd(OldSize, AllocaRzMask);
2043 // Misalign = kAllocaRzSize - PartialSize;
2044 Value *Misalign = IRB.CreateSub(AllocaRzSize, PartialSize);
2046 // PartialPadding = Misalign != kAllocaRzSize ? Misalign : 0;
2047 Value *Cond = IRB.CreateICmpNE(Misalign, AllocaRzSize);
2048 Value *PartialPadding = IRB.CreateSelect(Cond, Misalign, Zero);
2050 // AdditionalChunkSize = Align + PartialPadding + kAllocaRzSize
2051 // Align is added to locate left redzone, PartialPadding for possible
2052 // partial redzone and kAllocaRzSize for right redzone respectively.
2053 Value *AdditionalChunkSize = IRB.CreateAdd(
2054 ConstantInt::get(IntptrTy, Align + kAllocaRzSize), PartialPadding);
2056 Value *NewSize = IRB.CreateAdd(OldSize, AdditionalChunkSize);
2058 // Insert new alloca with new NewSize and Align params.
2059 AllocaInst *NewAlloca = IRB.CreateAlloca(IRB.getInt8Ty(), NewSize);
2060 NewAlloca->setAlignment(Align);
2062 // NewAddress = Address + Align
2063 Value *NewAddress = IRB.CreateAdd(IRB.CreatePtrToInt(NewAlloca, IntptrTy),
2064 ConstantInt::get(IntptrTy, Align));
2066 // Insert __asan_alloca_poison call for new created alloca.
2067 IRB.CreateCall(AsanAllocaPoisonFunc, {NewAddress, OldSize});
2069 // Store the last alloca's address to DynamicAllocaLayout. We'll need this
2070 // for unpoisoning stuff.
2071 IRB.CreateStore(IRB.CreatePtrToInt(NewAlloca, IntptrTy), DynamicAllocaLayout);
2073 Value *NewAddressPtr = IRB.CreateIntToPtr(NewAddress, AI->getType());
2075 // Replace all uses of AddessReturnedByAlloca with NewAddressPtr.
2076 AI->replaceAllUsesWith(NewAddressPtr);
2078 // We are done. Erase old alloca from parent.
2079 AI->eraseFromParent();
2082 // isSafeAccess returns true if Addr is always inbounds with respect to its
2083 // base object. For example, it is a field access or an array access with
2084 // constant inbounds index.
2085 bool AddressSanitizer::isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis,
2086 Value *Addr, uint64_t TypeSize) const {
2087 SizeOffsetType SizeOffset = ObjSizeVis.compute(Addr);
2088 if (!ObjSizeVis.bothKnown(SizeOffset)) return false;
2089 uint64_t Size = SizeOffset.first.getZExtValue();
2090 int64_t Offset = SizeOffset.second.getSExtValue();
2091 // Three checks are required to ensure safety:
2092 // . Offset >= 0 (since the offset is given from the base ptr)
2093 // . Size >= Offset (unsigned)
2094 // . Size - Offset >= NeededSize (unsigned)
2095 return Offset >= 0 && Size >= uint64_t(Offset) &&
2096 Size - uint64_t(Offset) >= TypeSize / 8;