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llvm-project/llvm/lib/Transforms/Instrumentation/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
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "asan"
#include "FunctionBlackList.h"
#include "llvm/Function.h"
#include "llvm/IRBuilder.h"
#include "llvm/InlineAsm.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Type.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/system_error.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include <string>
#include <algorithm>
using namespace llvm;
static const uint64_t kDefaultShadowScale = 3;
static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
static const uint64_t kDefaultShadowOffsetAndroid = 0;
static const size_t kMaxStackMallocSize = 1 << 16; // 64K
static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;
static const char *kAsanModuleCtorName = "asan.module_ctor";
static const char *kAsanModuleDtorName = "asan.module_dtor";
static const int kAsanCtorAndCtorPriority = 1;
static const char *kAsanReportErrorTemplate = "__asan_report_";
static const char *kAsanRegisterGlobalsName = "__asan_register_globals";
static const char *kAsanUnregisterGlobalsName = "__asan_unregister_globals";
static const char *kAsanInitName = "__asan_init";
static const char *kAsanHandleNoReturnName = "__asan_handle_no_return";
static const char *kAsanMappingOffsetName = "__asan_mapping_offset";
static const char *kAsanMappingScaleName = "__asan_mapping_scale";
static const char *kAsanStackMallocName = "__asan_stack_malloc";
static const char *kAsanStackFreeName = "__asan_stack_free";
static const int kAsanStackLeftRedzoneMagic = 0xf1;
static const int kAsanStackMidRedzoneMagic = 0xf2;
static const int kAsanStackRightRedzoneMagic = 0xf3;
static const int kAsanStackPartialRedzoneMagic = 0xf4;
// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
static const size_t kNumberOfAccessSizes = 5;
// 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> ClMergeCallbacks("asan-merge-callbacks",
cl::desc("merge __asan_report_ callbacks to create fewer BBs"),
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));
// This flag may need to be replaced with -f[no]asan-use-after-return.
static cl::opt<bool> ClUseAfterReturn("asan-use-after-return",
cl::desc("Check return-after-free"), cl::Hidden, cl::init(false));
// 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> ClMemIntrin("asan-memintrin",
cl::desc("Handle memset/memcpy/memmove"), cl::Hidden, cl::init(true));
// This flag may need to be replaced with -fasan-blacklist.
static cl::opt<std::string> ClBlackListFile("asan-blacklist",
cl::desc("File containing the list of functions to ignore "
"during instrumentation"), cl::Hidden);
// 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));
static cl::opt<int> ClMappingOffsetLog("asan-mapping-offset-log",
cl::desc("offset of asan shadow mapping"), cl::Hidden, cl::init(-1));
// 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));
// 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));
namespace {
/// When the crash callbacks are merged, they receive some amount of arguments
/// that are merged in a PHI node. This struct represents arguments from one
/// call site.
struct CrashArg {
Value *Arg1;
Value *Arg2;
};
/// An object of this type is created while instrumenting every function.
struct AsanFunctionContext {
AsanFunctionContext(Function &Function) : F(Function), CrashBlock() { }
Function &F;
// These are initially zero. If we require at least one call to
// __asan_report_{read,write}{1,2,4,8,16}, an appropriate BB is created.
BasicBlock *CrashBlock[2][kNumberOfAccessSizes];
typedef SmallVector<CrashArg, 8> CrashArgsVec;
CrashArgsVec CrashArgs[2][kNumberOfAccessSizes];
};
/// AddressSanitizer: instrument the code in module to find memory bugs.
struct AddressSanitizer : public ModulePass {
AddressSanitizer();
virtual const char *getPassName() const;
void instrumentMop(AsanFunctionContext &AFC, Instruction *I);
void instrumentAddress(AsanFunctionContext &AFC,
Instruction *OrigIns, IRBuilder<> &IRB,
Value *Addr, uint32_t TypeSize, bool IsWrite);
Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
Value *ShadowValue, uint32_t TypeSize);
Instruction *generateCrashCode(BasicBlock *BB, Value *Addr, Value *PC,
bool IsWrite, size_t AccessSizeIndex);
bool instrumentMemIntrinsic(AsanFunctionContext &AFC, MemIntrinsic *MI);
void instrumentMemIntrinsicParam(AsanFunctionContext &AFC,
Instruction *OrigIns, Value *Addr,
Value *Size,
Instruction *InsertBefore, bool IsWrite);
Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
bool handleFunction(Module &M, Function &F);
bool maybeInsertAsanInitAtFunctionEntry(Function &F);
bool poisonStackInFunction(Module &M, Function &F);
virtual bool runOnModule(Module &M);
bool insertGlobalRedzones(Module &M);
static char ID; // Pass identification, replacement for typeid
private:
uint64_t getAllocaSizeInBytes(AllocaInst *AI) {
Type *Ty = AI->getAllocatedType();
uint64_t SizeInBytes = TD->getTypeAllocSize(Ty);
return SizeInBytes;
}
uint64_t getAlignedSize(uint64_t SizeInBytes) {
return ((SizeInBytes + RedzoneSize - 1)
/ RedzoneSize) * RedzoneSize;
}
uint64_t getAlignedAllocaSize(AllocaInst *AI) {
uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
return getAlignedSize(SizeInBytes);
}
Function *checkInterfaceFunction(Constant *FuncOrBitcast);
void PoisonStack(const ArrayRef<AllocaInst*> &AllocaVec, IRBuilder<> IRB,
Value *ShadowBase, bool DoPoison);
bool LooksLikeCodeInBug11395(Instruction *I);
LLVMContext *C;
TargetData *TD;
uint64_t MappingOffset;
int MappingScale;
size_t RedzoneSize;
int LongSize;
Type *IntptrTy;
Type *IntptrPtrTy;
Function *AsanCtorFunction;
Function *AsanInitFunction;
Instruction *CtorInsertBefore;
OwningPtr<FunctionBlackList> BL;
// This array is indexed by AccessIsWrite and log2(AccessSize).
Function *AsanErrorCallback[2][kNumberOfAccessSizes];
InlineAsm *EmptyAsm;
};
} // namespace
char AddressSanitizer::ID = 0;
INITIALIZE_PASS(AddressSanitizer, "asan",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs.",
false, false)
AddressSanitizer::AddressSanitizer() : ModulePass(ID) { }
ModulePass *llvm::createAddressSanitizerPass() {
return new AddressSanitizer();
}
const char *AddressSanitizer::getPassName() const {
return "AddressSanitizer";
}
static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
size_t Res = CountTrailingZeros_32(TypeSize / 8);
assert(Res < kNumberOfAccessSizes);
return Res;
}
// Create a constant for Str so that we can pass it to the run-time lib.
static GlobalVariable *createPrivateGlobalForString(Module &M, StringRef Str) {
Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
return new GlobalVariable(M, StrConst->getType(), true,
GlobalValue::PrivateLinkage, StrConst, "");
}
// Split the basic block and insert an if-then code.
// Before:
// Head
// Cmp
// Tail
// After:
// Head
// if (Cmp)
// ThenBlock
// Tail
//
// If ThenBlock is zero, a new block is created and its terminator is returned.
// Otherwize 0 is returned.
static BranchInst *splitBlockAndInsertIfThen(Value *Cmp,
BasicBlock *ThenBlock = 0) {
Instruction *SplitBefore = cast<Instruction>(Cmp)->getNextNode();
BasicBlock *Head = SplitBefore->getParent();
BasicBlock *Tail = Head->splitBasicBlock(SplitBefore);
TerminatorInst *HeadOldTerm = Head->getTerminator();
BranchInst *CheckTerm = 0;
if (!ThenBlock) {
LLVMContext &C = Head->getParent()->getParent()->getContext();
ThenBlock = BasicBlock::Create(C, "", Head->getParent(), Tail);
CheckTerm = BranchInst::Create(Tail, ThenBlock);
}
BranchInst *HeadNewTerm =
BranchInst::Create(/*ifTrue*/ThenBlock, /*ifFalse*/Tail, Cmp);
ReplaceInstWithInst(HeadOldTerm, HeadNewTerm);
return CheckTerm;
}
Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
// Shadow >> scale
Shadow = IRB.CreateLShr(Shadow, MappingScale);
if (MappingOffset == 0)
return Shadow;
// (Shadow >> scale) | offset
return IRB.CreateOr(Shadow, ConstantInt::get(IntptrTy,
MappingOffset));
}
void AddressSanitizer::instrumentMemIntrinsicParam(
AsanFunctionContext &AFC, Instruction *OrigIns,
Value *Addr, Value *Size, Instruction *InsertBefore, bool IsWrite) {
// Check the first byte.
{
IRBuilder<> IRB(InsertBefore);
instrumentAddress(AFC, OrigIns, IRB, Addr, 8, IsWrite);
}
// Check the last byte.
{
IRBuilder<> IRB(InsertBefore);
Value *SizeMinusOne = IRB.CreateSub(
Size, ConstantInt::get(Size->getType(), 1));
SizeMinusOne = IRB.CreateIntCast(SizeMinusOne, IntptrTy, false);
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
Value *AddrPlusSizeMinisOne = IRB.CreateAdd(AddrLong, SizeMinusOne);
instrumentAddress(AFC, OrigIns, IRB, AddrPlusSizeMinisOne, 8, IsWrite);
}
}
// Instrument memset/memmove/memcpy
bool AddressSanitizer::instrumentMemIntrinsic(AsanFunctionContext &AFC,
MemIntrinsic *MI) {
Value *Dst = MI->getDest();
MemTransferInst *MemTran = dyn_cast<MemTransferInst>(MI);
Value *Src = MemTran ? MemTran->getSource() : 0;
Value *Length = MI->getLength();
Constant *ConstLength = dyn_cast<Constant>(Length);
Instruction *InsertBefore = MI;
if (ConstLength) {
if (ConstLength->isNullValue()) return false;
} else {
// The size is not a constant so it could be zero -- check at run-time.
IRBuilder<> IRB(InsertBefore);
Value *Cmp = IRB.CreateICmpNE(Length,
Constant::getNullValue(Length->getType()));
InsertBefore = splitBlockAndInsertIfThen(Cmp);
}
instrumentMemIntrinsicParam(AFC, MI, Dst, Length, InsertBefore, true);
if (Src)
instrumentMemIntrinsicParam(AFC, MI, Src, Length, InsertBefore, false);
return true;
}
// If I is an interesting memory access, return the PointerOperand
// and set IsWrite. Otherwise return NULL.
static Value *isInterestingMemoryAccess(Instruction *I, bool *IsWrite) {
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!ClInstrumentReads) return NULL;
*IsWrite = false;
return LI->getPointerOperand();
}
if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (!ClInstrumentWrites) return NULL;
*IsWrite = true;
return SI->getPointerOperand();
}
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
if (!ClInstrumentAtomics) return NULL;
*IsWrite = true;
return RMW->getPointerOperand();
}
if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!ClInstrumentAtomics) return NULL;
*IsWrite = true;
return XCHG->getPointerOperand();
}
return NULL;
}
void AddressSanitizer::instrumentMop(AsanFunctionContext &AFC, Instruction *I) {
bool IsWrite;
Value *Addr = isInterestingMemoryAccess(I, &IsWrite);
assert(Addr);
if (ClOpt && ClOptGlobals && isa<GlobalVariable>(Addr)) {
// We are accessing a global scalar variable. Nothing to catch here.
return;
}
Type *OrigPtrTy = Addr->getType();
Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
assert(OrigTy->isSized());
uint32_t TypeSize = TD->getTypeStoreSizeInBits(OrigTy);
if (TypeSize != 8 && TypeSize != 16 &&
TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
// Ignore all unusual sizes.
return;
}
IRBuilder<> IRB(I);
instrumentAddress(AFC, I, IRB, Addr, TypeSize, IsWrite);
}
// Validate the result of Module::getOrInsertFunction called for an interface
// function of AddressSanitizer. If the instrumented module defines a function
// with the same name, their prototypes must match, otherwise
// getOrInsertFunction returns a bitcast.
Function *AddressSanitizer::checkInterfaceFunction(Constant *FuncOrBitcast) {
if (isa<Function>(FuncOrBitcast)) return cast<Function>(FuncOrBitcast);
FuncOrBitcast->dump();
report_fatal_error("trying to redefine an AddressSanitizer "
"interface function");
}
Instruction *AddressSanitizer::generateCrashCode(
BasicBlock *BB, Value *Addr, Value *PC,
bool IsWrite, size_t AccessSizeIndex) {
IRBuilder<> IRB(BB->getFirstNonPHI());
CallInst *Call;
if (PC)
Call = IRB.CreateCall2(AsanErrorCallback[IsWrite][AccessSizeIndex],
Addr, PC);
else
Call = IRB.CreateCall(AsanErrorCallback[IsWrite][AccessSizeIndex], Addr);
// 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;
}
Value *AddressSanitizer::createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
Value *ShadowValue,
uint32_t TypeSize) {
size_t Granularity = 1 << MappingScale;
// Addr & (Granularity - 1)
Value *LastAccessedByte = IRB.CreateAnd(
AddrLong, ConstantInt::get(IntptrTy, Granularity - 1));
// (Addr & (Granularity - 1)) + size - 1
if (TypeSize / 8 > 1)
LastAccessedByte = IRB.CreateAdd(
LastAccessedByte, ConstantInt::get(IntptrTy, TypeSize / 8 - 1));
// (uint8_t) ((Addr & (Granularity-1)) + size - 1)
LastAccessedByte = IRB.CreateIntCast(
LastAccessedByte, IRB.getInt8Ty(), false);
// ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
}
void AddressSanitizer::instrumentAddress(AsanFunctionContext &AFC,
Instruction *OrigIns,
IRBuilder<> &IRB, Value *Addr,
uint32_t TypeSize, bool IsWrite) {
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
Type *ShadowTy = IntegerType::get(
*C, std::max(8U, TypeSize >> MappingScale));
Type *ShadowPtrTy = PointerType::get(ShadowTy, 0);
Value *ShadowPtr = memToShadow(AddrLong, IRB);
Value *CmpVal = Constant::getNullValue(ShadowTy);
Value *ShadowValue = IRB.CreateLoad(
IRB.CreateIntToPtr(ShadowPtr, ShadowPtrTy));
Value *Cmp = IRB.CreateICmpNE(ShadowValue, CmpVal);
BasicBlock *CrashBlock = 0;
if (ClMergeCallbacks) {
size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
BasicBlock **Cached = &AFC.CrashBlock[IsWrite][AccessSizeIndex];
if (!*Cached) {
std::string BBName("crash_bb-");
BBName += (IsWrite ? "w-" : "r-") + itostr(1 << AccessSizeIndex);
BasicBlock *BB = BasicBlock::Create(*C, BBName, &AFC.F);
new UnreachableInst(*C, BB);
*Cached = BB;
}
CrashBlock = *Cached;
// We need to pass the PC as the second parameter to __asan_report_*.
// There are few problems:
// - Some architectures (e.g. x86_32) don't have a cheap way to get the PC.
// - LLVM doesn't have the appropriate intrinsic.
// For now, put a random number into the PC, just to allow experiments.
Value *PC = ConstantInt::get(IntptrTy, rand());
CrashArg Arg = {AddrLong, PC};
AFC.CrashArgs[IsWrite][AccessSizeIndex].push_back(Arg);
} else {
CrashBlock = BasicBlock::Create(*C, "crash_bb", &AFC.F);
new UnreachableInst(*C, CrashBlock);
size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
Instruction *Crash =
generateCrashCode(CrashBlock, AddrLong, 0, IsWrite, AccessSizeIndex);
Crash->setDebugLoc(OrigIns->getDebugLoc());
}
size_t Granularity = 1 << MappingScale;
if (TypeSize < 8 * Granularity) {
BranchInst *CheckTerm = splitBlockAndInsertIfThen(Cmp);
assert(CheckTerm->isUnconditional());
BasicBlock *NextBB = CheckTerm->getSuccessor(0);
IRB.SetInsertPoint(CheckTerm);
Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
ReplaceInstWithInst(CheckTerm, NewTerm);
} else {
splitBlockAndInsertIfThen(Cmp, CrashBlock);
}
}
// This function replaces all global variables with new variables that have
// trailing redzones. It also creates a function that poisons
// redzones and inserts this function into llvm.global_ctors.
bool AddressSanitizer::insertGlobalRedzones(Module &M) {
SmallVector<GlobalVariable *, 16> GlobalsToChange;
for (Module::GlobalListType::iterator G = M.getGlobalList().begin(),
E = M.getGlobalList().end(); G != E; ++G) {
Type *Ty = cast<PointerType>(G->getType())->getElementType();
DEBUG(dbgs() << "GLOBAL: " << *G);
if (!Ty->isSized()) continue;
if (!G->hasInitializer()) continue;
// Touch only those globals that will not be defined in other modules.
// Don't handle ODR type linkages since other modules may be built w/o asan.
if (G->getLinkage() != GlobalVariable::ExternalLinkage &&
G->getLinkage() != GlobalVariable::PrivateLinkage &&
G->getLinkage() != GlobalVariable::InternalLinkage)
continue;
// Two problems with thread-locals:
// - The address of the main thread's copy can't be computed at link-time.
// - Need to poison all copies, not just the main thread's one.
if (G->isThreadLocal())
continue;
// For now, just ignore this Alloca if the alignment is large.
if (G->getAlignment() > RedzoneSize) continue;
// Ignore all the globals with the names starting with "\01L_OBJC_".
// Many of those are put into the .cstring section. The linker compresses
// that section by removing the spare \0s after the string terminator, so
// our redzones get broken.
if ((G->getName().find("\01L_OBJC_") == 0) ||
(G->getName().find("\01l_OBJC_") == 0)) {
DEBUG(dbgs() << "Ignoring \\01L_OBJC_* global: " << *G);
continue;
}
if (G->hasSection()) {
StringRef Section(G->getSection());
// Ignore the globals from the __OBJC section. The ObjC runtime assumes
// those conform to /usr/lib/objc/runtime.h, so we can't add redzones to
// them.
if ((Section.find("__OBJC,") == 0) ||
(Section.find("__DATA, __objc_") == 0)) {
DEBUG(dbgs() << "Ignoring ObjC runtime global: " << *G);
continue;
}
// See http://code.google.com/p/address-sanitizer/issues/detail?id=32
// Constant CFString instances are compiled in the following way:
// -- the string buffer is emitted into
// __TEXT,__cstring,cstring_literals
// -- the constant NSConstantString structure referencing that buffer
// is placed into __DATA,__cfstring
// Therefore there's no point in placing redzones into __DATA,__cfstring.
// Moreover, it causes the linker to crash on OS X 10.7
if (Section.find("__DATA,__cfstring") == 0) {
DEBUG(dbgs() << "Ignoring CFString: " << *G);
continue;
}
}
GlobalsToChange.push_back(G);
}
size_t n = GlobalsToChange.size();
if (n == 0) return false;
// A global is described by a structure
// size_t beg;
// size_t size;
// size_t size_with_redzone;
// const char *name;
// We initialize an array of such structures and pass it to a run-time call.
StructType *GlobalStructTy = StructType::get(IntptrTy, IntptrTy,
IntptrTy, IntptrTy, NULL);
SmallVector<Constant *, 16> Initializers(n);
IRBuilder<> IRB(CtorInsertBefore);
for (size_t i = 0; i < n; i++) {
GlobalVariable *G = GlobalsToChange[i];
PointerType *PtrTy = cast<PointerType>(G->getType());
Type *Ty = PtrTy->getElementType();
uint64_t SizeInBytes = TD->getTypeAllocSize(Ty);
uint64_t RightRedzoneSize = RedzoneSize +
(RedzoneSize - (SizeInBytes % RedzoneSize));
Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
StructType *NewTy = StructType::get(Ty, RightRedZoneTy, NULL);
Constant *NewInitializer = ConstantStruct::get(
NewTy, G->getInitializer(),
Constant::getNullValue(RightRedZoneTy), NULL);
SmallString<2048> DescriptionOfGlobal = G->getName();
DescriptionOfGlobal += " (";
DescriptionOfGlobal += M.getModuleIdentifier();
DescriptionOfGlobal += ")";
GlobalVariable *Name = createPrivateGlobalForString(M, DescriptionOfGlobal);
// Create a new global variable with enough space for a redzone.
GlobalVariable *NewGlobal = new GlobalVariable(
M, NewTy, G->isConstant(), G->getLinkage(),
NewInitializer, "", G, G->getThreadLocalMode());
NewGlobal->copyAttributesFrom(G);
NewGlobal->setAlignment(RedzoneSize);
Value *Indices2[2];
Indices2[0] = IRB.getInt32(0);
Indices2[1] = IRB.getInt32(0);
G->replaceAllUsesWith(
ConstantExpr::getGetElementPtr(NewGlobal, Indices2, true));
NewGlobal->takeName(G);
G->eraseFromParent();
Initializers[i] = ConstantStruct::get(
GlobalStructTy,
ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
ConstantInt::get(IntptrTy, SizeInBytes),
ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
ConstantExpr::getPointerCast(Name, IntptrTy),
NULL);
DEBUG(dbgs() << "NEW GLOBAL:\n" << *NewGlobal);
}
ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
GlobalVariable *AllGlobals = new GlobalVariable(
M, ArrayOfGlobalStructTy, false, GlobalVariable::PrivateLinkage,
ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
Function *AsanRegisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
IRB.CreateCall2(AsanRegisterGlobals,
IRB.CreatePointerCast(AllGlobals, IntptrTy),
ConstantInt::get(IntptrTy, n));
// We also need to unregister globals at the end, e.g. when a shared library
// gets closed.
Function *AsanDtorFunction = Function::Create(
FunctionType::get(Type::getVoidTy(*C), false),
GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
Function *AsanUnregisterGlobals =
checkInterfaceFunction(M.getOrInsertFunction(
kAsanUnregisterGlobalsName,
IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
IRB_Dtor.CreateCall2(AsanUnregisterGlobals,
IRB.CreatePointerCast(AllGlobals, IntptrTy),
ConstantInt::get(IntptrTy, n));
appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndCtorPriority);
DEBUG(dbgs() << M);
return true;
}
// virtual
bool AddressSanitizer::runOnModule(Module &M) {
// Initialize the private fields. No one has accessed them before.
TD = getAnalysisIfAvailable<TargetData>();
if (!TD)
return false;
BL.reset(new FunctionBlackList(ClBlackListFile));
C = &(M.getContext());
LongSize = TD->getPointerSizeInBits();
IntptrTy = Type::getIntNTy(*C, LongSize);
IntptrPtrTy = PointerType::get(IntptrTy, 0);
AsanCtorFunction = Function::Create(
FunctionType::get(Type::getVoidTy(*C), false),
GlobalValue::InternalLinkage, kAsanModuleCtorName, &M);
BasicBlock *AsanCtorBB = BasicBlock::Create(*C, "", AsanCtorFunction);
CtorInsertBefore = ReturnInst::Create(*C, AsanCtorBB);
// call __asan_init in the module ctor.
IRBuilder<> IRB(CtorInsertBefore);
AsanInitFunction = checkInterfaceFunction(
M.getOrInsertFunction(kAsanInitName, IRB.getVoidTy(), NULL));
AsanInitFunction->setLinkage(Function::ExternalLinkage);
IRB.CreateCall(AsanInitFunction);
// Create __asan_report* callbacks.
for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
AccessSizeIndex++) {
// IsWrite and TypeSize are encoded in the function name.
std::string FunctionName = std::string(kAsanReportErrorTemplate) +
(AccessIsWrite ? "store" : "load") + itostr(1 << AccessSizeIndex);
// If we are merging crash callbacks, they have two parameters.
if (ClMergeCallbacks)
AsanErrorCallback[AccessIsWrite][AccessSizeIndex] = cast<Function>(
M.getOrInsertFunction(FunctionName, IRB.getVoidTy(), IntptrTy,
IntptrTy, NULL));
else
AsanErrorCallback[AccessIsWrite][AccessSizeIndex] = cast<Function>(
M.getOrInsertFunction(FunctionName, IRB.getVoidTy(), IntptrTy, NULL));
}
}
// We insert an empty inline asm after __asan_report* to avoid callback merge.
EmptyAsm = InlineAsm::get(FunctionType::get(IRB.getVoidTy(), false),
StringRef(""), StringRef(""),
/*hasSideEffects=*/true);
llvm::Triple targetTriple(M.getTargetTriple());
bool isAndroid = targetTriple.getEnvironment() == llvm::Triple::ANDROIDEABI;
MappingOffset = isAndroid ? kDefaultShadowOffsetAndroid :
(LongSize == 32 ? kDefaultShadowOffset32 : kDefaultShadowOffset64);
if (ClMappingOffsetLog >= 0) {
if (ClMappingOffsetLog == 0) {
// special case
MappingOffset = 0;
} else {
MappingOffset = 1ULL << ClMappingOffsetLog;
}
}
MappingScale = kDefaultShadowScale;
if (ClMappingScale) {
MappingScale = ClMappingScale;
}
// 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.
RedzoneSize = std::max(32, (int)(1 << MappingScale));
bool Res = false;
if (ClGlobals)
Res |= insertGlobalRedzones(M);
if (ClMappingOffsetLog >= 0) {
// Tell the run-time the current values of mapping offset and scale.
GlobalValue *asan_mapping_offset =
new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
ConstantInt::get(IntptrTy, MappingOffset),
kAsanMappingOffsetName);
// Read the global, otherwise it may be optimized away.
IRB.CreateLoad(asan_mapping_offset, true);
}
if (ClMappingScale) {
GlobalValue *asan_mapping_scale =
new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
ConstantInt::get(IntptrTy, MappingScale),
kAsanMappingScaleName);
// Read the global, otherwise it may be optimized away.
IRB.CreateLoad(asan_mapping_scale, true);
}
for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
if (F->isDeclaration()) continue;
Res |= handleFunction(M, *F);
}
appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndCtorPriority);
return Res;
}
bool AddressSanitizer::maybeInsertAsanInitAtFunctionEntry(Function &F) {
// For each NSObject descendant having a +load method, this method is invoked
// by the ObjC runtime before any of the static constructors is called.
// Therefore we need to instrument such methods with a call to __asan_init
// at the beginning in order to initialize our runtime before any access to
// the shadow memory.
// We cannot just ignore these methods, because they may call other
// instrumented functions.
if (F.getName().find(" load]") != std::string::npos) {
IRBuilder<> IRB(F.begin()->begin());
IRB.CreateCall(AsanInitFunction);
return true;
}
return false;
}
bool AddressSanitizer::handleFunction(Module &M, Function &F) {
if (BL->isIn(F)) return false;
if (&F == AsanCtorFunction) return false;
// If needed, insert __asan_init before checking for AddressSafety attr.
maybeInsertAsanInitAtFunctionEntry(F);
if (!F.hasFnAttr(Attribute::AddressSafety)) return false;
if (!ClDebugFunc.empty() && ClDebugFunc != F.getName())
return false;
// We want to instrument every address only once per basic block
// (unless there are calls between uses).
SmallSet<Value*, 16> TempsToInstrument;
SmallVector<Instruction*, 16> ToInstrument;
SmallVector<Instruction*, 8> NoReturnCalls;
bool IsWrite;
// Fill the set of memory operations to instrument.
for (Function::iterator FI = F.begin(), FE = F.end();
FI != FE; ++FI) {
TempsToInstrument.clear();
int NumInsnsPerBB = 0;
for (BasicBlock::iterator BI = FI->begin(), BE = FI->end();
BI != BE; ++BI) {
if (LooksLikeCodeInBug11395(BI)) return false;
if (Value *Addr = isInterestingMemoryAccess(BI, &IsWrite)) {
if (ClOpt && ClOptSameTemp) {
if (!TempsToInstrument.insert(Addr))
continue; // We've seen this temp in the current BB.
}
} else if (isa<MemIntrinsic>(BI) && ClMemIntrin) {
// ok, take it.
} else {
if (CallInst *CI = dyn_cast<CallInst>(BI)) {
// A call inside BB.
TempsToInstrument.clear();
if (CI->doesNotReturn()) {
NoReturnCalls.push_back(CI);
}
}
continue;
}
ToInstrument.push_back(BI);
NumInsnsPerBB++;
if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB)
break;
}
}
AsanFunctionContext AFC(F);
// Instrument.
int NumInstrumented = 0;
for (size_t i = 0, n = ToInstrument.size(); i != n; i++) {
Instruction *Inst = ToInstrument[i];
if (ClDebugMin < 0 || ClDebugMax < 0 ||
(NumInstrumented >= ClDebugMin && NumInstrumented <= ClDebugMax)) {
if (isInterestingMemoryAccess(Inst, &IsWrite))
instrumentMop(AFC, Inst);
else
instrumentMemIntrinsic(AFC, cast<MemIntrinsic>(Inst));
}
NumInstrumented++;
}
// Create PHI nodes and crash callbacks if we are merging crash callbacks.
if (NumInstrumented) {
for (size_t IsWrite = 0; IsWrite <= 1; IsWrite++) {
for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
AccessSizeIndex++) {
BasicBlock *BB = AFC.CrashBlock[IsWrite][AccessSizeIndex];
if (!BB) continue;
assert(ClMergeCallbacks);
AsanFunctionContext::CrashArgsVec &Args =
AFC.CrashArgs[IsWrite][AccessSizeIndex];
IRBuilder<> IRB(BB->getFirstNonPHI());
size_t n = Args.size();
PHINode *PN1 = IRB.CreatePHI(IntptrTy, n);
PHINode *PN2 = IRB.CreatePHI(IntptrTy, n);
// We need to match crash parameters and the predecessors.
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
PI != PE; ++PI) {
n--;
PN1->addIncoming(Args[n].Arg1, *PI);
PN2->addIncoming(Args[n].Arg2, *PI);
}
assert(n == 0);
generateCrashCode(BB, PN1, PN2, IsWrite, AccessSizeIndex);
}
}
}
DEBUG(dbgs() << F);
bool ChangedStack = poisonStackInFunction(M, F);
// We must unpoison the stack before every NoReturn call (throw, _exit, etc).
// See e.g. http://code.google.com/p/address-sanitizer/issues/detail?id=37
for (size_t i = 0, n = NoReturnCalls.size(); i != n; i++) {
Instruction *CI = NoReturnCalls[i];
IRBuilder<> IRB(CI);
IRB.CreateCall(M.getOrInsertFunction(kAsanHandleNoReturnName,
IRB.getVoidTy(), NULL));
}
return NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
}
static uint64_t ValueForPoison(uint64_t PoisonByte, size_t ShadowRedzoneSize) {
if (ShadowRedzoneSize == 1) return PoisonByte;
if (ShadowRedzoneSize == 2) return (PoisonByte << 8) + PoisonByte;
if (ShadowRedzoneSize == 4)
return (PoisonByte << 24) + (PoisonByte << 16) +
(PoisonByte << 8) + (PoisonByte);
llvm_unreachable("ShadowRedzoneSize is either 1, 2 or 4");
}
static void PoisonShadowPartialRightRedzone(uint8_t *Shadow,
size_t Size,
size_t RedzoneSize,
size_t ShadowGranularity,
uint8_t Magic) {
for (size_t i = 0; i < RedzoneSize;
i+= ShadowGranularity, Shadow++) {
if (i + ShadowGranularity <= Size) {
*Shadow = 0; // fully addressable
} else if (i >= Size) {
*Shadow = Magic; // unaddressable
} else {
*Shadow = Size - i; // first Size-i bytes are addressable
}
}
}
void AddressSanitizer::PoisonStack(const ArrayRef<AllocaInst*> &AllocaVec,
IRBuilder<> IRB,
Value *ShadowBase, bool DoPoison) {
size_t ShadowRZSize = RedzoneSize >> MappingScale;
assert(ShadowRZSize >= 1 && ShadowRZSize <= 4);
Type *RZTy = Type::getIntNTy(*C, ShadowRZSize * 8);
Type *RZPtrTy = PointerType::get(RZTy, 0);
Value *PoisonLeft = ConstantInt::get(RZTy,
ValueForPoison(DoPoison ? kAsanStackLeftRedzoneMagic : 0LL, ShadowRZSize));
Value *PoisonMid = ConstantInt::get(RZTy,
ValueForPoison(DoPoison ? kAsanStackMidRedzoneMagic : 0LL, ShadowRZSize));
Value *PoisonRight = ConstantInt::get(RZTy,
ValueForPoison(DoPoison ? kAsanStackRightRedzoneMagic : 0LL, ShadowRZSize));
// poison the first red zone.
IRB.CreateStore(PoisonLeft, IRB.CreateIntToPtr(ShadowBase, RZPtrTy));
// poison all other red zones.
uint64_t Pos = RedzoneSize;
for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
AllocaInst *AI = AllocaVec[i];
uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
uint64_t AlignedSize = getAlignedAllocaSize(AI);
assert(AlignedSize - SizeInBytes < RedzoneSize);
Value *Ptr = NULL;
Pos += AlignedSize;
assert(ShadowBase->getType() == IntptrTy);
if (SizeInBytes < AlignedSize) {
// Poison the partial redzone at right
Ptr = IRB.CreateAdd(
ShadowBase, ConstantInt::get(IntptrTy,
(Pos >> MappingScale) - ShadowRZSize));
size_t AddressableBytes = RedzoneSize - (AlignedSize - SizeInBytes);
uint32_t Poison = 0;
if (DoPoison) {
PoisonShadowPartialRightRedzone((uint8_t*)&Poison, AddressableBytes,
RedzoneSize,
1ULL << MappingScale,
kAsanStackPartialRedzoneMagic);
}
Value *PartialPoison = ConstantInt::get(RZTy, Poison);
IRB.CreateStore(PartialPoison, IRB.CreateIntToPtr(Ptr, RZPtrTy));
}
// Poison the full redzone at right.
Ptr = IRB.CreateAdd(ShadowBase,
ConstantInt::get(IntptrTy, Pos >> MappingScale));
Value *Poison = i == AllocaVec.size() - 1 ? PoisonRight : PoisonMid;
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, RZPtrTy));
Pos += RedzoneSize;
}
}
// Workaround for bug 11395: we don't want to instrument stack in functions
// with large assembly blobs (32-bit only), otherwise reg alloc may crash.
// FIXME: remove once the bug 11395 is fixed.
bool AddressSanitizer::LooksLikeCodeInBug11395(Instruction *I) {
if (LongSize != 32) return false;
CallInst *CI = dyn_cast<CallInst>(I);
if (!CI || !CI->isInlineAsm()) return false;
if (CI->getNumArgOperands() <= 5) return false;
// We have inline assembly with quite a few arguments.
return true;
}
// Find all static Alloca instructions and put
// poisoned red zones around all of them.
// Then unpoison everything back before the function returns.
//
// 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.
bool AddressSanitizer::poisonStackInFunction(Module &M, Function &F) {
if (!ClStack) return false;
SmallVector<AllocaInst*, 16> AllocaVec;
SmallVector<Instruction*, 8> RetVec;
uint64_t TotalSize = 0;
// Filter out Alloca instructions we want (and can) handle.
// Collect Ret instructions.
for (Function::iterator FI = F.begin(), FE = F.end();
FI != FE; ++FI) {
BasicBlock &BB = *FI;
for (BasicBlock::iterator BI = BB.begin(), BE = BB.end();
BI != BE; ++BI) {
if (isa<ReturnInst>(BI)) {
RetVec.push_back(BI);
continue;
}
AllocaInst *AI = dyn_cast<AllocaInst>(BI);
if (!AI) continue;
if (AI->isArrayAllocation()) continue;
if (!AI->isStaticAlloca()) continue;
if (!AI->getAllocatedType()->isSized()) continue;
if (AI->getAlignment() > RedzoneSize) continue;
AllocaVec.push_back(AI);
uint64_t AlignedSize = getAlignedAllocaSize(AI);
TotalSize += AlignedSize;
}
}
if (AllocaVec.empty()) return false;
uint64_t LocalStackSize = TotalSize + (AllocaVec.size() + 1) * RedzoneSize;
bool DoStackMalloc = ClUseAfterReturn
&& LocalStackSize <= kMaxStackMallocSize;
Instruction *InsBefore = AllocaVec[0];
IRBuilder<> IRB(InsBefore);
Type *ByteArrayTy = ArrayType::get(IRB.getInt8Ty(), LocalStackSize);
AllocaInst *MyAlloca =
new AllocaInst(ByteArrayTy, "MyAlloca", InsBefore);
MyAlloca->setAlignment(RedzoneSize);
assert(MyAlloca->isStaticAlloca());
Value *OrigStackBase = IRB.CreatePointerCast(MyAlloca, IntptrTy);
Value *LocalStackBase = OrigStackBase;
if (DoStackMalloc) {
Value *AsanStackMallocFunc = M.getOrInsertFunction(
kAsanStackMallocName, IntptrTy, IntptrTy, IntptrTy, NULL);
LocalStackBase = IRB.CreateCall2(AsanStackMallocFunc,
ConstantInt::get(IntptrTy, LocalStackSize), OrigStackBase);
}
// This string will be parsed by the run-time (DescribeStackAddress).
SmallString<2048> StackDescriptionStorage;
raw_svector_ostream StackDescription(StackDescriptionStorage);
StackDescription << F.getName() << " " << AllocaVec.size() << " ";
uint64_t Pos = RedzoneSize;
// Replace Alloca instructions with base+offset.
for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
AllocaInst *AI = AllocaVec[i];
uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
StringRef Name = AI->getName();
StackDescription << Pos << " " << SizeInBytes << " "
<< Name.size() << " " << Name << " ";
uint64_t AlignedSize = getAlignedAllocaSize(AI);
assert((AlignedSize % RedzoneSize) == 0);
AI->replaceAllUsesWith(
IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Pos)),
AI->getType()));
Pos += AlignedSize + RedzoneSize;
}
assert(Pos == LocalStackSize);
// Write the Magic value and the frame description constant to the redzone.
Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
BasePlus0);
Value *BasePlus1 = IRB.CreateAdd(LocalStackBase,
ConstantInt::get(IntptrTy, LongSize/8));
BasePlus1 = IRB.CreateIntToPtr(BasePlus1, IntptrPtrTy);
Value *Description = IRB.CreatePointerCast(
createPrivateGlobalForString(M, StackDescription.str()),
IntptrTy);
IRB.CreateStore(Description, BasePlus1);
// Poison the stack redzones at the entry.
Value *ShadowBase = memToShadow(LocalStackBase, IRB);
PoisonStack(ArrayRef<AllocaInst*>(AllocaVec), IRB, ShadowBase, true);
Value *AsanStackFreeFunc = NULL;
if (DoStackMalloc) {
AsanStackFreeFunc = M.getOrInsertFunction(
kAsanStackFreeName, IRB.getVoidTy(),
IntptrTy, IntptrTy, IntptrTy, NULL);
}
// Unpoison the stack before all ret instructions.
for (size_t i = 0, n = RetVec.size(); i < n; i++) {
Instruction *Ret = RetVec[i];
IRBuilder<> IRBRet(Ret);
// Mark the current frame as retired.
IRBRet.CreateStore(ConstantInt::get(IntptrTy, kRetiredStackFrameMagic),
BasePlus0);
// Unpoison the stack.
PoisonStack(ArrayRef<AllocaInst*>(AllocaVec), IRBRet, ShadowBase, false);
if (DoStackMalloc) {
IRBRet.CreateCall3(AsanStackFreeFunc, LocalStackBase,
ConstantInt::get(IntptrTy, LocalStackSize),
OrigStackBase);
}
}
if (ClDebugStack) {
DEBUG(dbgs() << F);
}
return true;
}
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