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AddressSanitizer.cpp
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AddressSanitizer.cpp
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//===-- AddressSanitizer.cpp - memory error detector ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of AddressSanitizer, an address sanity checker.
// Details of the algorithm:
// http://code.google.com/p/address-sanitizer/wiki/AddressSanitizerAlgorithm
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/SwapByteOrder.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/ASanStackFrameLayout.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <algorithm>
#include <string>
#include <system_error>
using namespace llvm;
#define DEBUG_TYPE "asan"
static const uint64_t kDefaultShadowScale = 3;
static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000; // < 2G.
static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000;
static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 37;
static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36;
static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
static const size_t kMinStackMallocSize = 1 << 6; // 64B
static const size_t kMaxStackMallocSize = 1 << 16; // 64K
static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
static const char *const kAsanModuleCtorName = "asan.module_ctor";
static const char *const kAsanModuleDtorName = "asan.module_dtor";
static const uint64_t kAsanCtorAndDtorPriority = 1;
static const char *const kAsanReportErrorTemplate = "__asan_report_";
static const char *const kAsanRegisterGlobalsName = "__asan_register_globals";
static const char *const kAsanUnregisterGlobalsName =
"__asan_unregister_globals";
static const char *const kAsanPoisonGlobalsName = "__asan_before_dynamic_init";
static const char *const kAsanUnpoisonGlobalsName = "__asan_after_dynamic_init";
static const char *const kAsanInitName = "__asan_init_v5";
static const char *const kAsanPtrCmp = "__sanitizer_ptr_cmp";
static const char *const kAsanPtrSub = "__sanitizer_ptr_sub";
static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
static const int kMaxAsanStackMallocSizeClass = 10;
static const char *const kAsanStackMallocNameTemplate = "__asan_stack_malloc_";
static const char *const kAsanStackFreeNameTemplate = "__asan_stack_free_";
static const char *const kAsanGenPrefix = "__asan_gen_";
static const char *const kSanCovGenPrefix = "__sancov_gen_";
static const char *const kAsanPoisonStackMemoryName =
"__asan_poison_stack_memory";
static const char *const kAsanUnpoisonStackMemoryName =
"__asan_unpoison_stack_memory";
static const char *const kAsanOptionDetectUAR =
"__asan_option_detect_stack_use_after_return";
// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
static const size_t kNumberOfAccessSizes = 5;
static const unsigned kAllocaRzSize = 32;
static const unsigned kAsanAllocaLeftMagic = 0xcacacacaU;
static const unsigned kAsanAllocaRightMagic = 0xcbcbcbcbU;
static const unsigned kAsanAllocaPartialVal1 = 0xcbcbcb00U;
static const unsigned kAsanAllocaPartialVal2 = 0x000000cbU;
// Command-line flags.
// This flag may need to be replaced with -f[no-]asan-reads.
static cl::opt<bool> ClInstrumentReads("asan-instrument-reads",
cl::desc("instrument read instructions"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentWrites(
"asan-instrument-writes", cl::desc("instrument write instructions"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClInstrumentAtomics(
"asan-instrument-atomics",
cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden,
cl::init(true));
static cl::opt<bool> ClAlwaysSlowPath(
"asan-always-slow-path",
cl::desc("use instrumentation with slow path for all accesses"), cl::Hidden,
cl::init(false));
// This flag limits the number of instructions to be instrumented
// in any given BB. Normally, this should be set to unlimited (INT_MAX),
// but due to http://llvm.org/bugs/show_bug.cgi?id=12652 we temporary
// set it to 10000.
static cl::opt<int> ClMaxInsnsToInstrumentPerBB(
"asan-max-ins-per-bb", cl::init(10000),
cl::desc("maximal number of instructions to instrument in any given BB"),
cl::Hidden);
// This flag may need to be replaced with -f[no]asan-stack.
static cl::opt<bool> ClStack("asan-stack", cl::desc("Handle stack memory"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
cl::desc("Check return-after-free"),
cl::Hidden, cl::init(true));
// This flag may need to be replaced with -f[no]asan-globals.
static cl::opt<bool> ClGlobals("asan-globals",
cl::desc("Handle global objects"), cl::Hidden,
cl::init(true));
static cl::opt<bool> ClInitializers("asan-initialization-order",
cl::desc("Handle C++ initializer order"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClInvalidPointerPairs(
"asan-detect-invalid-pointer-pair",
cl::desc("Instrument <, <=, >, >=, - with pointer operands"), cl::Hidden,
cl::init(false));
static cl::opt<unsigned> ClRealignStack(
"asan-realign-stack",
cl::desc("Realign stack to the value of this flag (power of two)"),
cl::Hidden, cl::init(32));
static cl::opt<int> ClInstrumentationWithCallsThreshold(
"asan-instrumentation-with-call-threshold",
cl::desc(
"If the function being instrumented contains more than "
"this number of memory accesses, use callbacks instead of "
"inline checks (-1 means never use callbacks)."),
cl::Hidden, cl::init(7000));
static cl::opt<std::string> ClMemoryAccessCallbackPrefix(
"asan-memory-access-callback-prefix",
cl::desc("Prefix for memory access callbacks"), cl::Hidden,
cl::init("__asan_"));
static cl::opt<bool> ClInstrumentAllocas("asan-instrument-allocas",
cl::desc("instrument dynamic allocas"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClSkipPromotableAllocas(
"asan-skip-promotable-allocas",
cl::desc("Do not instrument promotable allocas"), cl::Hidden,
cl::init(true));
// These flags allow to change the shadow mapping.
// The shadow mapping looks like
// Shadow = (Mem >> scale) + (1 << offset_log)
static cl::opt<int> ClMappingScale("asan-mapping-scale",
cl::desc("scale of asan shadow mapping"),
cl::Hidden, cl::init(0));
// Optimization flags. Not user visible, used mostly for testing
// and benchmarking the tool.
static cl::opt<bool> ClOpt("asan-opt", cl::desc("Optimize instrumentation"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClOptSameTemp(
"asan-opt-same-temp", cl::desc("Instrument the same temp just once"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClOptGlobals("asan-opt-globals",
cl::desc("Don't instrument scalar globals"),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClOptStack(
"asan-opt-stack", cl::desc("Don't instrument scalar stack variables"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClCheckLifetime(
"asan-check-lifetime",
cl::desc("Use llvm.lifetime intrinsics to insert extra checks"), cl::Hidden,
cl::init(false));
static cl::opt<bool> ClDynamicAllocaStack(
"asan-stack-dynamic-alloca",
cl::desc("Use dynamic alloca to represent stack variables"), cl::Hidden,
cl::init(true));
static cl::opt<uint32_t> ClForceExperiment(
"asan-force-experiment",
cl::desc("Force optimization experiment (for testing)"), cl::Hidden,
cl::init(0));
// Debug flags.
static cl::opt<int> ClDebug("asan-debug", cl::desc("debug"), cl::Hidden,
cl::init(0));
static cl::opt<int> ClDebugStack("asan-debug-stack", cl::desc("debug stack"),
cl::Hidden, cl::init(0));
static cl::opt<std::string> ClDebugFunc("asan-debug-func", cl::Hidden,
cl::desc("Debug func"));
static cl::opt<int> ClDebugMin("asan-debug-min", cl::desc("Debug min inst"),
cl::Hidden, cl::init(-1));
static cl::opt<int> ClDebugMax("asan-debug-max", cl::desc("Debug man inst"),
cl::Hidden, cl::init(-1));
STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
STATISTIC(NumInstrumentedDynamicAllocas,
"Number of instrumented dynamic allocas");
STATISTIC(NumOptimizedAccessesToGlobalVar,
"Number of optimized accesses to global vars");
STATISTIC(NumOptimizedAccessesToStackVar,
"Number of optimized accesses to stack vars");
namespace {
/// Frontend-provided metadata for source location.
struct LocationMetadata {
StringRef Filename;
int LineNo;
int ColumnNo;
LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {}
bool empty() const { return Filename.empty(); }
void parse(MDNode *MDN) {
assert(MDN->getNumOperands() == 3);
MDString *MDFilename = cast<MDString>(MDN->getOperand(0));
Filename = MDFilename->getString();
LineNo =
mdconst::extract<ConstantInt>(MDN->getOperand(1))->getLimitedValue();
ColumnNo =
mdconst::extract<ConstantInt>(MDN->getOperand(2))->getLimitedValue();
}
};
/// Frontend-provided metadata for global variables.
class GlobalsMetadata {
public:
struct Entry {
Entry() : SourceLoc(), Name(), IsDynInit(false), IsBlacklisted(false) {}
LocationMetadata SourceLoc;
StringRef Name;
bool IsDynInit;
bool IsBlacklisted;
};
GlobalsMetadata() : inited_(false) {}
void init(Module &M) {
assert(!inited_);
inited_ = true;
NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
if (!Globals) return;
for (auto MDN : Globals->operands()) {
// Metadata node contains the global and the fields of "Entry".
assert(MDN->getNumOperands() == 5);
auto *GV = mdconst::extract_or_null<GlobalVariable>(MDN->getOperand(0));
// The optimizer may optimize away a global entirely.
if (!GV) continue;
// We can already have an entry for GV if it was merged with another
// global.
Entry &E = Entries[GV];
if (auto *Loc = cast_or_null<MDNode>(MDN->getOperand(1)))
E.SourceLoc.parse(Loc);
if (auto *Name = cast_or_null<MDString>(MDN->getOperand(2)))
E.Name = Name->getString();
ConstantInt *IsDynInit =
mdconst::extract<ConstantInt>(MDN->getOperand(3));
E.IsDynInit |= IsDynInit->isOne();
ConstantInt *IsBlacklisted =
mdconst::extract<ConstantInt>(MDN->getOperand(4));
E.IsBlacklisted |= IsBlacklisted->isOne();
}
}
/// Returns metadata entry for a given global.
Entry get(GlobalVariable *G) const {
auto Pos = Entries.find(G);
return (Pos != Entries.end()) ? Pos->second : Entry();
}
private:
bool inited_;
DenseMap<GlobalVariable *, Entry> Entries;
};
/// This struct defines the shadow mapping using the rule:
/// shadow = (mem >> Scale) ADD-or-OR Offset.
struct ShadowMapping {
int Scale;
uint64_t Offset;
bool OrShadowOffset;
};
static ShadowMapping getShadowMapping(Triple &TargetTriple, int LongSize) {
bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
bool IsIOS = TargetTriple.isiOS();
bool IsFreeBSD = TargetTriple.isOSFreeBSD();
bool IsLinux = TargetTriple.isOSLinux();
bool IsPPC64 = TargetTriple.getArch() == llvm::Triple::ppc64 ||
TargetTriple.getArch() == llvm::Triple::ppc64le;
bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
bool IsMIPS32 = TargetTriple.getArch() == llvm::Triple::mips ||
TargetTriple.getArch() == llvm::Triple::mipsel;
bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 ||
TargetTriple.getArch() == llvm::Triple::mips64el;
bool IsAArch64 = TargetTriple.getArch() == llvm::Triple::aarch64;
bool IsWindows = TargetTriple.isOSWindows();
ShadowMapping Mapping;
if (LongSize == 32) {
if (IsAndroid)
Mapping.Offset = 0;
else if (IsMIPS32)
Mapping.Offset = kMIPS32_ShadowOffset32;
else if (IsFreeBSD)
Mapping.Offset = kFreeBSD_ShadowOffset32;
else if (IsIOS)
Mapping.Offset = kIOSShadowOffset32;
else if (IsWindows)
Mapping.Offset = kWindowsShadowOffset32;
else
Mapping.Offset = kDefaultShadowOffset32;
} else { // LongSize == 64
if (IsPPC64)
Mapping.Offset = kPPC64_ShadowOffset64;
else if (IsFreeBSD)
Mapping.Offset = kFreeBSD_ShadowOffset64;
else if (IsLinux && IsX86_64)
Mapping.Offset = kSmallX86_64ShadowOffset;
else if (IsMIPS64)
Mapping.Offset = kMIPS64_ShadowOffset64;
else if (IsAArch64)
Mapping.Offset = kAArch64_ShadowOffset64;
else
Mapping.Offset = kDefaultShadowOffset64;
}
Mapping.Scale = kDefaultShadowScale;
if (ClMappingScale) {
Mapping.Scale = ClMappingScale;
}
// OR-ing shadow offset if more efficient (at least on x86) if the offset
// is a power of two, but on ppc64 we have to use add since the shadow
// offset is not necessary 1/8-th of the address space.
Mapping.OrShadowOffset = !IsPPC64 && !(Mapping.Offset & (Mapping.Offset - 1));
return Mapping;
}
static size_t RedzoneSizeForScale(int MappingScale) {
// Redzone used for stack and globals is at least 32 bytes.
// For scales 6 and 7, the redzone has to be 64 and 128 bytes respectively.
return std::max(32U, 1U << MappingScale);
}
/// AddressSanitizer: instrument the code in module to find memory bugs.
struct AddressSanitizer : public FunctionPass {
AddressSanitizer() : FunctionPass(ID) {
initializeAddressSanitizerPass(*PassRegistry::getPassRegistry());
}
const char *getPassName() const override {
return "AddressSanitizerFunctionPass";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
}
uint64_t getAllocaSizeInBytes(AllocaInst *AI) const {
Type *Ty = AI->getAllocatedType();
uint64_t SizeInBytes =
AI->getModule()->getDataLayout().getTypeAllocSize(Ty);
return SizeInBytes;
}
/// Check if we want (and can) handle this alloca.
bool isInterestingAlloca(AllocaInst &AI);
/// If it is an interesting memory access, return the PointerOperand
/// and set IsWrite/Alignment. Otherwise return nullptr.
Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite,
uint64_t *TypeSize,
unsigned *Alignment);
void instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis, Instruction *I,
bool UseCalls, const DataLayout &DL);
void instrumentPointerComparisonOrSubtraction(Instruction *I);
void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
Value *Addr, uint32_t TypeSize, bool IsWrite,
Value *SizeArgument, bool UseCalls, uint32_t Exp);
void instrumentUnusualSizeOrAlignment(Instruction *I, Value *Addr,
uint32_t TypeSize, bool IsWrite,
Value *SizeArgument, bool UseCalls,
uint32_t Exp);
Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
Value *ShadowValue, uint32_t TypeSize);
Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
bool IsWrite, size_t AccessSizeIndex,
Value *SizeArgument, uint32_t Exp);
void instrumentMemIntrinsic(MemIntrinsic *MI);
Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
bool runOnFunction(Function &F) override;
bool maybeInsertAsanInitAtFunctionEntry(Function &F);
bool doInitialization(Module &M) override;
static char ID; // Pass identification, replacement for typeid
DominatorTree &getDominatorTree() const { return *DT; }
private:
void initializeCallbacks(Module &M);
bool LooksLikeCodeInBug11395(Instruction *I);
bool GlobalIsLinkerInitialized(GlobalVariable *G);
bool isSafeAccess(ObjectSizeOffsetVisitor &ObjSizeVis, Value *Addr,
uint64_t TypeSize) const;
LLVMContext *C;
Triple TargetTriple;
int LongSize;
Type *IntptrTy;
ShadowMapping Mapping;
DominatorTree *DT;
Function *AsanCtorFunction;
Function *AsanInitFunction;
Function *AsanHandleNoReturnFunc;
Function *AsanPtrCmpFunction, *AsanPtrSubFunction;
// This array is indexed by AccessIsWrite, Experiment and log2(AccessSize).
Function *AsanErrorCallback[2][2][kNumberOfAccessSizes];
Function *AsanMemoryAccessCallback[2][2][kNumberOfAccessSizes];
// This array is indexed by AccessIsWrite and Experiment.
Function *AsanErrorCallbackSized[2][2];
Function *AsanMemoryAccessCallbackSized[2][2];
Function *AsanMemmove, *AsanMemcpy, *AsanMemset;
InlineAsm *EmptyAsm;
GlobalsMetadata GlobalsMD;
DenseMap<AllocaInst *, bool> ProcessedAllocas;
friend struct FunctionStackPoisoner;
};
class AddressSanitizerModule : public ModulePass {
public:
AddressSanitizerModule() : ModulePass(ID) {}
bool runOnModule(Module &M) override;
static char ID; // Pass identification, replacement for typeid
const char *getPassName() const override { return "AddressSanitizerModule"; }
private:
void initializeCallbacks(Module &M);
bool InstrumentGlobals(IRBuilder<> &IRB, Module &M);
bool ShouldInstrumentGlobal(GlobalVariable *G);
void poisonOneInitializer(Function &GlobalInit, GlobalValue *ModuleName);
void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
size_t MinRedzoneSizeForGlobal() const {
return RedzoneSizeForScale(Mapping.Scale);
}
GlobalsMetadata GlobalsMD;
Type *IntptrTy;
LLVMContext *C;
Triple TargetTriple;
ShadowMapping Mapping;
Function *AsanPoisonGlobals;
Function *AsanUnpoisonGlobals;
Function *AsanRegisterGlobals;
Function *AsanUnregisterGlobals;
};
// Stack poisoning does not play well with exception handling.
// When an exception is thrown, we essentially bypass the code
// that unpoisones the stack. This is why the run-time library has
// to intercept __cxa_throw (as well as longjmp, etc) and unpoison the entire
// stack in the interceptor. This however does not work inside the
// actual function which catches the exception. Most likely because the
// compiler hoists the load of the shadow value somewhere too high.
// This causes asan to report a non-existing bug on 453.povray.
// It sounds like an LLVM bug.
struct FunctionStackPoisoner : public InstVisitor<FunctionStackPoisoner> {
Function &F;
AddressSanitizer &ASan;
DIBuilder DIB;
LLVMContext *C;
Type *IntptrTy;
Type *IntptrPtrTy;
ShadowMapping Mapping;
SmallVector<AllocaInst *, 16> AllocaVec;
SmallVector<Instruction *, 8> RetVec;
unsigned StackAlignment;
Function *AsanStackMallocFunc[kMaxAsanStackMallocSizeClass + 1],
*AsanStackFreeFunc[kMaxAsanStackMallocSizeClass + 1];
Function *AsanPoisonStackMemoryFunc, *AsanUnpoisonStackMemoryFunc;
// Stores a place and arguments of poisoning/unpoisoning call for alloca.
struct AllocaPoisonCall {
IntrinsicInst *InsBefore;
AllocaInst *AI;
uint64_t Size;
bool DoPoison;
};
SmallVector<AllocaPoisonCall, 8> AllocaPoisonCallVec;
// Stores left and right redzone shadow addresses for dynamic alloca
// and pointer to alloca instruction itself.
// LeftRzAddr is a shadow address for alloca left redzone.
// RightRzAddr is a shadow address for alloca right redzone.
struct DynamicAllocaCall {
AllocaInst *AI;
Value *LeftRzAddr;
Value *RightRzAddr;
bool Poison;
explicit DynamicAllocaCall(AllocaInst *AI, Value *LeftRzAddr = nullptr,
Value *RightRzAddr = nullptr)
: AI(AI),
LeftRzAddr(LeftRzAddr),
RightRzAddr(RightRzAddr),
Poison(true) {}
};
SmallVector<DynamicAllocaCall, 1> DynamicAllocaVec;
// Maps Value to an AllocaInst from which the Value is originated.
typedef DenseMap<Value *, AllocaInst *> AllocaForValueMapTy;
AllocaForValueMapTy AllocaForValue;
bool HasNonEmptyInlineAsm;
std::unique_ptr<CallInst> EmptyInlineAsm;
FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
: F(F),
ASan(ASan),
DIB(*F.getParent(), /*AllowUnresolved*/ false),
C(ASan.C),
IntptrTy(ASan.IntptrTy),
IntptrPtrTy(PointerType::get(IntptrTy, 0)),
Mapping(ASan.Mapping),
StackAlignment(1 << Mapping.Scale),
HasNonEmptyInlineAsm(false),
EmptyInlineAsm(CallInst::Create(ASan.EmptyAsm)) {}
bool runOnFunction() {
if (!ClStack) return false;
// Collect alloca, ret, lifetime instructions etc.
for (BasicBlock *BB : depth_first(&F.getEntryBlock())) visit(*BB);
if (AllocaVec.empty() && DynamicAllocaVec.empty()) return false;
initializeCallbacks(*F.getParent());
poisonStack();
if (ClDebugStack) {
DEBUG(dbgs() << F);
}
return true;
}
// Finds all Alloca instructions and puts
// poisoned red zones around all of them.
// Then unpoison everything back before the function returns.
void poisonStack();
// ----------------------- Visitors.
/// \brief Collect all Ret instructions.
void visitReturnInst(ReturnInst &RI) { RetVec.push_back(&RI); }
// Unpoison dynamic allocas redzones.
void unpoisonDynamicAlloca(DynamicAllocaCall &AllocaCall) {
if (!AllocaCall.Poison) return;
for (auto Ret : RetVec) {
IRBuilder<> IRBRet(Ret);
PointerType *Int32PtrTy = PointerType::getUnqual(IRBRet.getInt32Ty());
Value *Zero = Constant::getNullValue(IRBRet.getInt32Ty());
Value *PartialRzAddr = IRBRet.CreateSub(AllocaCall.RightRzAddr,
ConstantInt::get(IntptrTy, 4));
IRBRet.CreateStore(
Zero, IRBRet.CreateIntToPtr(AllocaCall.LeftRzAddr, Int32PtrTy));
IRBRet.CreateStore(Zero,
IRBRet.CreateIntToPtr(PartialRzAddr, Int32PtrTy));
IRBRet.CreateStore(
Zero, IRBRet.CreateIntToPtr(AllocaCall.RightRzAddr, Int32PtrTy));
}
}
// Right shift for BigEndian and left shift for LittleEndian.
Value *shiftAllocaMagic(Value *Val, IRBuilder<> &IRB, Value *Shift) {
auto &DL = F.getParent()->getDataLayout();
return DL.isLittleEndian() ? IRB.CreateShl(Val, Shift)
: IRB.CreateLShr(Val, Shift);
}
// Compute PartialRzMagic for dynamic alloca call. Since we don't know the
// size of requested memory until runtime, we should compute it dynamically.
// If PartialSize is 0, PartialRzMagic would contain kAsanAllocaRightMagic,
// otherwise it would contain the value that we will use to poison the
// partial redzone for alloca call.
Value *computePartialRzMagic(Value *PartialSize, IRBuilder<> &IRB);
// Deploy and poison redzones around dynamic alloca call. To do this, we
// should replace this call with another one with changed parameters and
// replace all its uses with new address, so
// addr = alloca type, old_size, align
// is replaced by
// new_size = (old_size + additional_size) * sizeof(type)
// tmp = alloca i8, new_size, max(align, 32)
// addr = tmp + 32 (first 32 bytes are for the left redzone).
// Additional_size is added to make new memory allocation contain not only
// requested memory, but also left, partial and right redzones.
// After that, we should poison redzones:
// (1) Left redzone with kAsanAllocaLeftMagic.
// (2) Partial redzone with the value, computed in runtime by
// computePartialRzMagic function.
// (3) Right redzone with kAsanAllocaRightMagic.
void handleDynamicAllocaCall(DynamicAllocaCall &AllocaCall);
/// \brief Collect Alloca instructions we want (and can) handle.
void visitAllocaInst(AllocaInst &AI) {
if (!ASan.isInterestingAlloca(AI)) return;
StackAlignment = std::max(StackAlignment, AI.getAlignment());
if (isDynamicAlloca(AI))
DynamicAllocaVec.push_back(DynamicAllocaCall(&AI));
else
AllocaVec.push_back(&AI);
}
/// \brief Collect lifetime intrinsic calls to check for use-after-scope
/// errors.
void visitIntrinsicInst(IntrinsicInst &II) {
if (!ClCheckLifetime) return;
Intrinsic::ID ID = II.getIntrinsicID();
if (ID != Intrinsic::lifetime_start && ID != Intrinsic::lifetime_end)
return;
// Found lifetime intrinsic, add ASan instrumentation if necessary.
ConstantInt *Size = dyn_cast<ConstantInt>(II.getArgOperand(0));
// If size argument is undefined, don't do anything.
if (Size->isMinusOne()) return;
// Check that size doesn't saturate uint64_t and can
// be stored in IntptrTy.
const uint64_t SizeValue = Size->getValue().getLimitedValue();
if (SizeValue == ~0ULL ||
!ConstantInt::isValueValidForType(IntptrTy, SizeValue))
return;
// Find alloca instruction that corresponds to llvm.lifetime argument.
AllocaInst *AI = findAllocaForValue(II.getArgOperand(1));
if (!AI) return;
bool DoPoison = (ID == Intrinsic::lifetime_end);
AllocaPoisonCall APC = {&II, AI, SizeValue, DoPoison};
AllocaPoisonCallVec.push_back(APC);
}
void visitCallInst(CallInst &CI) {
HasNonEmptyInlineAsm |=
CI.isInlineAsm() && !CI.isIdenticalTo(EmptyInlineAsm.get());
}
// ---------------------- Helpers.
void initializeCallbacks(Module &M);
bool doesDominateAllExits(const Instruction *I) const {
for (auto Ret : RetVec) {
if (!ASan.getDominatorTree().dominates(I, Ret)) return false;
}
return true;
}
bool isDynamicAlloca(AllocaInst &AI) const {
return AI.isArrayAllocation() || !AI.isStaticAlloca();
}
/// Finds alloca where the value comes from.
AllocaInst *findAllocaForValue(Value *V);
void poisonRedZones(ArrayRef<uint8_t> ShadowBytes, IRBuilder<> &IRB,
Value *ShadowBase, bool DoPoison);
void poisonAlloca(Value *V, uint64_t Size, IRBuilder<> &IRB, bool DoPoison);
void SetShadowToStackAfterReturnInlined(IRBuilder<> &IRB, Value *ShadowBase,
int Size);
Value *createAllocaForLayout(IRBuilder<> &IRB, const ASanStackFrameLayout &L,
bool Dynamic);
PHINode *createPHI(IRBuilder<> &IRB, Value *Cond, Value *ValueIfTrue,
Instruction *ThenTerm, Value *ValueIfFalse);
};
} // namespace
char AddressSanitizer::ID = 0;
INITIALIZE_PASS_BEGIN(
AddressSanitizer, "asan",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(
AddressSanitizer, "asan",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs.", false,
false)
FunctionPass *llvm::createAddressSanitizerFunctionPass() {
return new AddressSanitizer();
}
char AddressSanitizerModule::ID = 0;
INITIALIZE_PASS(
AddressSanitizerModule, "asan-module",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs."
"ModulePass",
false, false)
ModulePass *llvm::createAddressSanitizerModulePass() {
return new AddressSanitizerModule();
}
static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
size_t Res = countTrailingZeros(TypeSize / 8);
assert(Res < kNumberOfAccessSizes);
return Res;
}
// \brief Create a constant for Str so that we can pass it to the run-time lib.
static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str,
bool AllowMerging) {
Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
// We use private linkage for module-local strings. If they can be merged
// with another one, we set the unnamed_addr attribute.
GlobalVariable *GV =
new GlobalVariable(M, StrConst->getType(), true,
GlobalValue::PrivateLinkage, StrConst, kAsanGenPrefix);
if (AllowMerging) GV->setUnnamedAddr(true);
GV->setAlignment(1); // Strings may not be merged w/o setting align 1.
return GV;
}
/// \brief Create a global describing a source location.
static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M,
LocationMetadata MD) {
Constant *LocData[] = {
createPrivateGlobalForString(M, MD.Filename, true),
ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo),
ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo),
};
auto LocStruct = ConstantStruct::getAnon(LocData);
auto GV = new GlobalVariable(M, LocStruct->getType(), true,
GlobalValue::PrivateLinkage, LocStruct,
kAsanGenPrefix);
GV->setUnnamedAddr(true);
return GV;
}
static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
return G->getName().find(kAsanGenPrefix) == 0 ||
G->getName().find(kSanCovGenPrefix) == 0;
}
Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
// Shadow >> scale
Shadow = IRB.CreateLShr(Shadow, Mapping.Scale);
if (Mapping.Offset == 0) return Shadow;
// (Shadow >> scale) | offset
if (Mapping.OrShadowOffset)
return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
else
return IRB.CreateAdd(Shadow, ConstantInt::get(IntptrTy, Mapping.Offset));
}
// Instrument memset/memmove/memcpy
void AddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
IRBuilder<> IRB(MI);
if (isa<MemTransferInst>(MI)) {
IRB.CreateCall3(
isa<MemMoveInst>(MI) ? AsanMemmove : AsanMemcpy,
IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false));
} else if (isa<MemSetInst>(MI)) {
IRB.CreateCall3(
AsanMemset,
IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false));
}
MI->eraseFromParent();
}
/// Check if we want (and can) handle this alloca.
bool AddressSanitizer::isInterestingAlloca(AllocaInst &AI) {
auto PreviouslySeenAllocaInfo = ProcessedAllocas.find(&AI);
if (PreviouslySeenAllocaInfo != ProcessedAllocas.end())
return PreviouslySeenAllocaInfo->getSecond();
bool IsInteresting = (AI.getAllocatedType()->isSized() &&
// alloca() may be called with 0 size, ignore it.
getAllocaSizeInBytes(&AI) > 0 &&
// We are only interested in allocas not promotable to registers.
// Promotable allocas are common under -O0.
(!ClSkipPromotableAllocas || !isAllocaPromotable(&AI)));
ProcessedAllocas[&AI] = IsInteresting;
return IsInteresting;
}
/// If I is an interesting memory access, return the PointerOperand
/// and set IsWrite/Alignment. Otherwise return nullptr.
Value *AddressSanitizer::isInterestingMemoryAccess(Instruction *I,
bool *IsWrite,
uint64_t *TypeSize,
unsigned *Alignment) {
// Skip memory accesses inserted by another instrumentation.
if (I->getMetadata("nosanitize")) return nullptr;
Value *PtrOperand = nullptr;
const DataLayout &DL = I->getModule()->getDataLayout();
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!ClInstrumentReads) return nullptr;
*IsWrite = false;
*TypeSize = DL.getTypeStoreSizeInBits(LI->getType());
*Alignment = LI->getAlignment();
PtrOperand = LI->getPointerOperand();
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (!ClInstrumentWrites) return nullptr;
*IsWrite = true;
*TypeSize = DL.getTypeStoreSizeInBits(SI->getValueOperand()->getType());
*Alignment = SI->getAlignment();
PtrOperand = SI->getPointerOperand();
} else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
*TypeSize = DL.getTypeStoreSizeInBits(RMW->getValOperand()->getType());
*Alignment = 0;
PtrOperand = RMW->getPointerOperand();
} else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!ClInstrumentAtomics) return nullptr;
*IsWrite = true;
*TypeSize = DL.getTypeStoreSizeInBits(XCHG->getCompareOperand()->getType());
*Alignment = 0;
PtrOperand = XCHG->getPointerOperand();
}
// Treat memory accesses to promotable allocas as non-interesting since they
// will not cause memory violations. This greatly speeds up the instrumented
// executable at -O0.
if (ClSkipPromotableAllocas)
if (auto AI = dyn_cast_or_null<AllocaInst>(PtrOperand))
return isInterestingAlloca(*AI) ? AI : nullptr;
return PtrOperand;
}
static bool isPointerOperand(Value *V) {
return V->getType()->isPointerTy() || isa<PtrToIntInst>(V);
}
// This is a rough heuristic; it may cause both false positives and
// false negatives. The proper implementation requires cooperation with
// the frontend.
static bool isInterestingPointerComparisonOrSubtraction(Instruction *I) {
if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
if (!Cmp->isRelational()) return false;
} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
if (BO->getOpcode() != Instruction::Sub) return false;
} else {
return false;
}
if (!isPointerOperand(I->getOperand(0)) ||
!isPointerOperand(I->getOperand(1)))
return false;
return true;
}
bool AddressSanitizer::GlobalIsLinkerInitialized(GlobalVariable *G) {
// If a global variable does not have dynamic initialization we don't
// have to instrument it. However, if a global does not have initializer
// at all, we assume it has dynamic initializer (in other TU).
return G->hasInitializer() && !GlobalsMD.get(G).IsDynInit;
}
void AddressSanitizer::instrumentPointerComparisonOrSubtraction(
Instruction *I) {
IRBuilder<> IRB(I);
Function *F = isa<ICmpInst>(I) ? AsanPtrCmpFunction : AsanPtrSubFunction;
Value *Param[2] = {I->getOperand(0), I->getOperand(1)};
for (int i = 0; i < 2; i++) {
if (Param[i]->getType()->isPointerTy())
Param[i] = IRB.CreatePointerCast(Param[i], IntptrTy);
}
IRB.CreateCall2(F, Param[0], Param[1]);
}
void AddressSanitizer::instrumentMop(ObjectSizeOffsetVisitor &ObjSizeVis,
Instruction *I, bool UseCalls,
const DataLayout &DL) {
bool IsWrite = false;
unsigned Alignment = 0;
uint64_t TypeSize = 0;
Value *Addr = isInterestingMemoryAccess(I, &IsWrite, &TypeSize, &Alignment);
assert(Addr);
// Optimization experiments.
// The experiments can be used to evaluate potential optimizations that remove
// instrumentation (assess false negatives). Instead of completely removing
// some instrumentation, you set Exp to a non-zero value (mask of optimization
// experiments that want to remove instrumentation of this instruction).
// If Exp is non-zero, this pass will emit special calls into runtime
// (e.g. __asan_report_exp_load1 instead of __asan_report_load1). These calls
// make runtime terminate the program in a special way (with a different
// exit status). Then you run the new compiler on a buggy corpus, collect
// the special terminations (ideally, you don't see them at all -- no false
// negatives) and make the decision on the optimization.
uint32_t Exp = ClForceExperiment;
if (ClOpt && ClOptGlobals) {
// If initialization order checking is disabled, a simple access to a
// dynamically initialized global is always valid.
GlobalVariable *G = dyn_cast<GlobalVariable>(GetUnderlyingObject(Addr, DL));
if (G != NULL && (!ClInitializers || GlobalIsLinkerInitialized(G)) &&
isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
NumOptimizedAccessesToGlobalVar++;
return;
}
}
if (ClOpt && ClOptStack) {
// A direct inbounds access to a stack variable is always valid.
if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
isSafeAccess(ObjSizeVis, Addr, TypeSize)) {
NumOptimizedAccessesToStackVar++;
return;
}
}
if (IsWrite)
NumInstrumentedWrites++;
else
NumInstrumentedReads++;
unsigned Granularity = 1 << Mapping.Scale;
// Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check
// if the data is properly aligned.
if ((TypeSize == 8 || TypeSize == 16 || TypeSize == 32 || TypeSize == 64 ||
TypeSize == 128) &&
(Alignment >= Granularity || Alignment == 0 || Alignment >= TypeSize / 8))
return instrumentAddress(I, I, Addr, TypeSize, IsWrite, nullptr, UseCalls,
Exp);
instrumentUnusualSizeOrAlignment(I, Addr, TypeSize, IsWrite, nullptr,
UseCalls, Exp);
}
Instruction *AddressSanitizer::generateCrashCode(Instruction *InsertBefore,
Value *Addr, bool IsWrite,
size_t AccessSizeIndex,
Value *SizeArgument,
uint32_t Exp) {
IRBuilder<> IRB(InsertBefore);
Value *ExpVal = Exp == 0 ? nullptr : ConstantInt::get(IRB.getInt32Ty(), Exp);
CallInst *Call = nullptr;
if (SizeArgument) {
if (Exp == 0)
Call = IRB.CreateCall2(AsanErrorCallbackSized[IsWrite][0], Addr,
SizeArgument);
else
Call = IRB.CreateCall3(AsanErrorCallbackSized[IsWrite][1], Addr,
SizeArgument, ExpVal);
} else {
if (Exp == 0)
Call =
IRB.CreateCall(AsanErrorCallback[IsWrite][0][AccessSizeIndex], Addr);
else
Call = IRB.CreateCall2(AsanErrorCallback[IsWrite][1][AccessSizeIndex],
Addr, ExpVal);
}
// We don't do Call->setDoesNotReturn() because the BB already has
// UnreachableInst at the end.
// This EmptyAsm is required to avoid callback merge.
IRB.CreateCall(EmptyAsm);
return Call;
}