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llvm-6502/lib/Transforms/Instrumentation/AddressSanitizer.cpp
Evgeniy Stepanov a7eb2b83ba Add an explicit insert point argument to SplitBlockAndInsertIfThen. 
Currently SplitBlockAndInsertIfThen requires that branch condition is an
Instruction itself, which is very inconvenient, because it is sometimes an
Operator, or even a Constant.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197677 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-19 13:29:56 +00:00

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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 "llvm/Transforms/Instrumentation.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/OwningPtr.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/DIBuilder.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/InstVisitor.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/system_error.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/SpecialCaseList.h"
#include <algorithm>
#include <string>
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 kDefaultShort64bitShadowOffset = 0x7FFF8000; // < 2G.
static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa8000;
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 int kAsanCtorAndCtorPriority = 1;
static const char *const kAsanReportErrorTemplate = "__asan_report_";
static const char *const kAsanReportLoadN = "__asan_report_load_n";
static const char *const kAsanReportStoreN = "__asan_report_store_n";
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_v3";
static const char *const kAsanCovName = "__sanitizer_cov";
static const char *const kAsanHandleNoReturnName = "__asan_handle_no_return";
static const char *const kAsanMappingOffsetName = "__asan_mapping_offset";
static const char *const kAsanMappingScaleName = "__asan_mapping_scale";
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 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";
#ifndef NDEBUG
static const int kAsanStackAfterReturnMagic = 0xf5;
#endif
// 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> 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));
// 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> ClCoverage("asan-coverage",
cl::desc("ASan coverage"), cl::Hidden, cl::init(false));
static cl::opt<bool> ClInitializers("asan-initialization-order",
cl::desc("Handle C++ initializer order"), cl::Hidden, cl::init(false));
static cl::opt<bool> ClMemIntrin("asan-memintrin",
cl::desc("Handle memset/memcpy/memmove"), cl::Hidden, cl::init(true));
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<std::string> ClBlacklistFile("asan-blacklist",
cl::desc("File containing the list of objects to ignore "
"during instrumentation"), cl::Hidden);
// This is an experimental feature that will allow to choose between
// instrumented and non-instrumented code at link-time.
// If this option is on, just before instrumenting a function we create its
// clone; if the function is not changed by asan the clone is deleted.
// If we end up with a clone, we put the instrumented function into a section
// called "ASAN" and the uninstrumented function into a section called "NOASAN".
//
// This is still a prototype, we need to figure out a way to keep two copies of
// a function so that the linker can easily choose one of them.
static cl::opt<bool> ClKeepUninstrumented("asan-keep-uninstrumented-functions",
cl::desc("Keep uninstrumented copies of functions"),
cl::Hidden, cl::init(false));
// 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));
static cl::opt<bool> ClShort64BitOffset("asan-short-64bit-mapping-offset",
cl::desc("Use short immediate constant as the mapping offset for 64bit"),
cl::Hidden, cl::init(true));
// 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> ClCheckLifetime("asan-check-lifetime",
cl::desc("Use llvm.lifetime intrinsics to insert extra checks"),
cl::Hidden, cl::init(false));
// 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(NumOptimizedAccessesToGlobalArray,
"Number of optimized accesses to global arrays");
STATISTIC(NumOptimizedAccessesToGlobalVar,
"Number of optimized accesses to global vars");
namespace {
/// A set of dynamically initialized globals extracted from metadata.
class SetOfDynamicallyInitializedGlobals {
public:
void Init(Module& M) {
// Clang generates metadata identifying all dynamically initialized globals.
NamedMDNode *DynamicGlobals =
M.getNamedMetadata("llvm.asan.dynamically_initialized_globals");
if (!DynamicGlobals)
return;
for (int i = 0, n = DynamicGlobals->getNumOperands(); i < n; ++i) {
MDNode *MDN = DynamicGlobals->getOperand(i);
assert(MDN->getNumOperands() == 1);
Value *VG = MDN->getOperand(0);
// The optimizer may optimize away a global entirely, in which case we
// cannot instrument access to it.
if (!VG)
continue;
DynInitGlobals.insert(cast<GlobalVariable>(VG));
}
}
bool Contains(GlobalVariable *G) { return DynInitGlobals.count(G) != 0; }
private:
SmallSet<GlobalValue*, 32> DynInitGlobals;
};
/// 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(const Module &M, int LongSize,
bool ZeroBaseShadow) {
llvm::Triple TargetTriple(M.getTargetTriple());
bool IsAndroid = TargetTriple.getEnvironment() == llvm::Triple::Android;
bool IsMacOSX = TargetTriple.getOS() == llvm::Triple::MacOSX;
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;
ShadowMapping Mapping;
// OR-ing shadow offset if more efficient (at least on x86),
// but on ppc64 we have to use add since the shadow offset is not neccesary
// 1/8-th of the address space.
Mapping.OrShadowOffset = !IsPPC64 && !ClShort64BitOffset;
Mapping.Offset = (IsAndroid || ZeroBaseShadow) ? 0 :
(LongSize == 32 ?
(IsMIPS32 ? kMIPS32_ShadowOffset32 : kDefaultShadowOffset32) :
IsPPC64 ? kPPC64_ShadowOffset64 : kDefaultShadowOffset64);
if (!ZeroBaseShadow && ClShort64BitOffset && IsX86_64 && !IsMacOSX) {
assert(LongSize == 64);
Mapping.Offset = kDefaultShort64bitShadowOffset;
}
if (!ZeroBaseShadow && ClMappingOffsetLog >= 0) {
// Zero offset log is the special case.
Mapping.Offset = (ClMappingOffsetLog == 0) ? 0 : 1ULL << ClMappingOffsetLog;
}
Mapping.Scale = kDefaultShadowScale;
if (ClMappingScale) {
Mapping.Scale = ClMappingScale;
}
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(bool CheckInitOrder = true,
bool CheckUseAfterReturn = false,
bool CheckLifetime = false,
StringRef BlacklistFile = StringRef(),
bool ZeroBaseShadow = false)
: FunctionPass(ID),
CheckInitOrder(CheckInitOrder || ClInitializers),
CheckUseAfterReturn(CheckUseAfterReturn || ClUseAfterReturn),
CheckLifetime(CheckLifetime || ClCheckLifetime),
BlacklistFile(BlacklistFile.empty() ? ClBlacklistFile
: BlacklistFile),
ZeroBaseShadow(ZeroBaseShadow) {}
virtual const char *getPassName() const {
return "AddressSanitizerFunctionPass";
}
void instrumentMop(Instruction *I);
void instrumentAddress(Instruction *OrigIns, Instruction *InsertBefore,
Value *Addr, uint32_t TypeSize, bool IsWrite,
Value *SizeArgument);
Value *createSlowPathCmp(IRBuilder<> &IRB, Value *AddrLong,
Value *ShadowValue, uint32_t TypeSize);
Instruction *generateCrashCode(Instruction *InsertBefore, Value *Addr,
bool IsWrite, size_t AccessSizeIndex,
Value *SizeArgument);
bool instrumentMemIntrinsic(MemIntrinsic *MI);
void instrumentMemIntrinsicParam(Instruction *OrigIns, Value *Addr,
Value *Size,
Instruction *InsertBefore, bool IsWrite);
Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
bool runOnFunction(Function &F);
bool maybeInsertAsanInitAtFunctionEntry(Function &F);
void emitShadowMapping(Module &M, IRBuilder<> &IRB) const;
virtual bool doInitialization(Module &M);
static char ID; // Pass identification, replacement for typeid
private:
void initializeCallbacks(Module &M);
bool ShouldInstrumentGlobal(GlobalVariable *G);
bool LooksLikeCodeInBug11395(Instruction *I);
void FindDynamicInitializers(Module &M);
bool GlobalIsLinkerInitialized(GlobalVariable *G);
bool InjectCoverage(Function &F);
bool CheckInitOrder;
bool CheckUseAfterReturn;
bool CheckLifetime;
SmallString<64> BlacklistFile;
bool ZeroBaseShadow;
LLVMContext *C;
DataLayout *TD;
int LongSize;
Type *IntptrTy;
ShadowMapping Mapping;
Function *AsanCtorFunction;
Function *AsanInitFunction;
Function *AsanHandleNoReturnFunc;
Function *AsanCovFunction;
OwningPtr<SpecialCaseList> BL;
// This array is indexed by AccessIsWrite and log2(AccessSize).
Function *AsanErrorCallback[2][kNumberOfAccessSizes];
// This array is indexed by AccessIsWrite.
Function *AsanErrorCallbackSized[2];
InlineAsm *EmptyAsm;
SetOfDynamicallyInitializedGlobals DynamicallyInitializedGlobals;
friend struct FunctionStackPoisoner;
};
class AddressSanitizerModule : public ModulePass {
public:
AddressSanitizerModule(bool CheckInitOrder = true,
StringRef BlacklistFile = StringRef(),
bool ZeroBaseShadow = false)
: ModulePass(ID),
CheckInitOrder(CheckInitOrder || ClInitializers),
BlacklistFile(BlacklistFile.empty() ? ClBlacklistFile
: BlacklistFile),
ZeroBaseShadow(ZeroBaseShadow) {}
bool runOnModule(Module &M);
static char ID; // Pass identification, replacement for typeid
virtual const char *getPassName() const {
return "AddressSanitizerModule";
}
private:
void initializeCallbacks(Module &M);
bool ShouldInstrumentGlobal(GlobalVariable *G);
void createInitializerPoisonCalls(Module &M, GlobalValue *ModuleName);
size_t MinRedzoneSizeForGlobal() const {
return RedzoneSizeForScale(Mapping.Scale);
}
bool CheckInitOrder;
SmallString<64> BlacklistFile;
bool ZeroBaseShadow;
OwningPtr<SpecialCaseList> BL;
SetOfDynamicallyInitializedGlobals DynamicallyInitializedGlobals;
Type *IntptrTy;
LLVMContext *C;
DataLayout *TD;
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;
// Maps Value to an AllocaInst from which the Value is originated.
typedef DenseMap<Value*, AllocaInst*> AllocaForValueMapTy;
AllocaForValueMapTy AllocaForValue;
FunctionStackPoisoner(Function &F, AddressSanitizer &ASan)
: F(F), ASan(ASan), DIB(*F.getParent()), C(ASan.C),
IntptrTy(ASan.IntptrTy), IntptrPtrTy(PointerType::get(IntptrTy, 0)),
Mapping(ASan.Mapping),
StackAlignment(1 << Mapping.Scale) {}
bool runOnFunction() {
if (!ClStack) return false;
// Collect alloca, ret, lifetime instructions etc.
for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()),
DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) {
BasicBlock *BB = *DI;
visit(*BB);
}
if (AllocaVec.empty()) return false;
initializeCallbacks(*F.getParent());
poisonStack();
if (ClDebugStack) {
DEBUG(dbgs() << F);
}
return true;
}
// Finds all static 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);
}
/// \brief Collect Alloca instructions we want (and can) handle.
void visitAllocaInst(AllocaInst &AI) {
if (!isInterestingAlloca(AI)) return;
StackAlignment = std::max(StackAlignment, AI.getAlignment());
AllocaVec.push_back(&AI);
}
/// \brief Collect lifetime intrinsic calls to check for use-after-scope
/// errors.
void visitIntrinsicInst(IntrinsicInst &II) {
if (!ASan.CheckLifetime) 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);
}
// ---------------------- Helpers.
void initializeCallbacks(Module &M);
// Check if we want (and can) handle this alloca.
bool isInterestingAlloca(AllocaInst &AI) const {
return (!AI.isArrayAllocation() && AI.isStaticAlloca() &&
AI.getAllocatedType()->isSized() &&
// alloca() may be called with 0 size, ignore it.
getAllocaSizeInBytes(&AI) > 0);
}
uint64_t getAllocaSizeInBytes(AllocaInst *AI) const {
Type *Ty = AI->getAllocatedType();
uint64_t SizeInBytes = ASan.TD->getTypeAllocSize(Ty);
return SizeInBytes;
}
/// Finds alloca where the value comes from.
AllocaInst *findAllocaForValue(Value *V);
void poisonRedZones(const 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);
};
} // namespace
char AddressSanitizer::ID = 0;
INITIALIZE_PASS(AddressSanitizer, "asan",
"AddressSanitizer: detects use-after-free and out-of-bounds bugs.",
false, false)
FunctionPass *llvm::createAddressSanitizerFunctionPass(
bool CheckInitOrder, bool CheckUseAfterReturn, bool CheckLifetime,
StringRef BlacklistFile, bool ZeroBaseShadow) {
return new AddressSanitizer(CheckInitOrder, CheckUseAfterReturn,
CheckLifetime, BlacklistFile, ZeroBaseShadow);
}
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(
bool CheckInitOrder, StringRef BlacklistFile, bool ZeroBaseShadow) {
return new AddressSanitizerModule(CheckInitOrder, BlacklistFile,
ZeroBaseShadow);
}
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) {
Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str);
GlobalVariable *GV = new GlobalVariable(M, StrConst->getType(), true,
GlobalValue::InternalLinkage, StrConst,
kAsanGenPrefix);
GV->setUnnamedAddr(true); // Ok to merge these.
GV->setAlignment(1); // Strings may not be merged w/o setting align 1.
return GV;
}
static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
return G->getName().find(kAsanGenPrefix) == 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));
}
void AddressSanitizer::instrumentMemIntrinsicParam(
Instruction *OrigIns,
Value *Addr, Value *Size, Instruction *InsertBefore, bool IsWrite) {
IRBuilder<> IRB(InsertBefore);
if (Size->getType() != IntptrTy)
Size = IRB.CreateIntCast(Size, IntptrTy, false);
// Check the first byte.
instrumentAddress(OrigIns, InsertBefore, Addr, 8, IsWrite, Size);
// Check the last byte.
IRB.SetInsertPoint(InsertBefore);
Value *SizeMinusOne = IRB.CreateSub(Size, ConstantInt::get(IntptrTy, 1));
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
Value *AddrLast = IRB.CreateAdd(AddrLong, SizeMinusOne);
instrumentAddress(OrigIns, InsertBefore, AddrLast, 8, IsWrite, Size);
}
// Instrument memset/memmove/memcpy
bool AddressSanitizer::instrumentMemIntrinsic(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, InsertBefore, false);
}
instrumentMemIntrinsicParam(MI, Dst, Length, InsertBefore, true);
if (Src)
instrumentMemIntrinsicParam(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;
}
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() && !DynamicallyInitializedGlobals.Contains(G);
}
void AddressSanitizer::instrumentMop(Instruction *I) {
bool IsWrite = false;
Value *Addr = isInterestingMemoryAccess(I, &IsWrite);
assert(Addr);
if (ClOpt && ClOptGlobals) {
if (GlobalVariable *G = dyn_cast<GlobalVariable>(Addr)) {
// If initialization order checking is disabled, a simple access to a
// dynamically initialized global is always valid.
if (!CheckInitOrder || GlobalIsLinkerInitialized(G)) {
NumOptimizedAccessesToGlobalVar++;
return;
}
}
ConstantExpr *CE = dyn_cast<ConstantExpr>(Addr);
if (CE && CE->isGEPWithNoNotionalOverIndexing()) {
if (GlobalVariable *G = dyn_cast<GlobalVariable>(CE->getOperand(0))) {
if (CE->getOperand(1)->isNullValue() && GlobalIsLinkerInitialized(G)) {
NumOptimizedAccessesToGlobalArray++;
return;
}
}
}
}
Type *OrigPtrTy = Addr->getType();
Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
assert(OrigTy->isSized());
uint32_t TypeSize = TD->getTypeStoreSizeInBits(OrigTy);
assert((TypeSize % 8) == 0);
if (IsWrite)
NumInstrumentedWrites++;
else
NumInstrumentedReads++;
// Instrument a 1-, 2-, 4-, 8-, or 16- byte access with one check.
if (TypeSize == 8 || TypeSize == 16 ||
TypeSize == 32 || TypeSize == 64 || TypeSize == 128)
return instrumentAddress(I, I, Addr, TypeSize, IsWrite, 0);
// Instrument unusual size (but still multiple of 8).
// We can not do it with a single check, so we do 1-byte check for the first
// and the last bytes. We call __asan_report_*_n(addr, real_size) to be able
// to report the actual access size.
IRBuilder<> IRB(I);
Value *LastByte = IRB.CreateIntToPtr(
IRB.CreateAdd(IRB.CreatePointerCast(Addr, IntptrTy),
ConstantInt::get(IntptrTy, TypeSize / 8 - 1)),
OrigPtrTy);
Value *Size = ConstantInt::get(IntptrTy, TypeSize / 8);
instrumentAddress(I, I, Addr, 8, IsWrite, Size);
instrumentAddress(I, I, LastByte, 8, IsWrite, Size);
}
// 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.
static Function *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(
Instruction *InsertBefore, Value *Addr,
bool IsWrite, size_t AccessSizeIndex, Value *SizeArgument) {
IRBuilder<> IRB(InsertBefore);
CallInst *Call = SizeArgument
? IRB.CreateCall2(AsanErrorCallbackSized[IsWrite], Addr, SizeArgument)
: 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 << Mapping.Scale;
// 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, ShadowValue->getType(), false);
// ((uint8_t) ((Addr & (Granularity-1)) + size - 1)) >= ShadowValue
return IRB.CreateICmpSGE(LastAccessedByte, ShadowValue);
}
void AddressSanitizer::instrumentAddress(Instruction *OrigIns,
Instruction *InsertBefore,
Value *Addr, uint32_t TypeSize,
bool IsWrite, Value *SizeArgument) {
IRBuilder<> IRB(InsertBefore);
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
Type *ShadowTy = IntegerType::get(
*C, std::max(8U, TypeSize >> Mapping.Scale));
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);
size_t AccessSizeIndex = TypeSizeToSizeIndex(TypeSize);
size_t Granularity = 1 << Mapping.Scale;
TerminatorInst *CrashTerm = 0;
if (ClAlwaysSlowPath || (TypeSize < 8 * Granularity)) {
TerminatorInst *CheckTerm =
SplitBlockAndInsertIfThen(Cmp, InsertBefore, false);
assert(dyn_cast<BranchInst>(CheckTerm)->isUnconditional());
BasicBlock *NextBB = CheckTerm->getSuccessor(0);
IRB.SetInsertPoint(CheckTerm);
Value *Cmp2 = createSlowPathCmp(IRB, AddrLong, ShadowValue, TypeSize);
BasicBlock *CrashBlock =
BasicBlock::Create(*C, "", NextBB->getParent(), NextBB);
CrashTerm = new UnreachableInst(*C, CrashBlock);
BranchInst *NewTerm = BranchInst::Create(CrashBlock, NextBB, Cmp2);
ReplaceInstWithInst(CheckTerm, NewTerm);
} else {
CrashTerm = SplitBlockAndInsertIfThen(Cmp, InsertBefore, true);
}
Instruction *Crash = generateCrashCode(
CrashTerm, AddrLong, IsWrite, AccessSizeIndex, SizeArgument);
Crash->setDebugLoc(OrigIns->getDebugLoc());
}
void AddressSanitizerModule::createInitializerPoisonCalls(
Module &M, GlobalValue *ModuleName) {
// We do all of our poisoning and unpoisoning within _GLOBAL__I_a.
Function *GlobalInit = M.getFunction("_GLOBAL__I_a");
// If that function is not present, this TU contains no globals, or they have
// all been optimized away
if (!GlobalInit)
return;
// Set up the arguments to our poison/unpoison functions.
IRBuilder<> IRB(GlobalInit->begin()->getFirstInsertionPt());
// Add a call to poison all external globals before the given function starts.
Value *ModuleNameAddr = ConstantExpr::getPointerCast(ModuleName, IntptrTy);
IRB.CreateCall(AsanPoisonGlobals, ModuleNameAddr);
// Add calls to unpoison all globals before each return instruction.
for (Function::iterator I = GlobalInit->begin(), E = GlobalInit->end();
I != E; ++I) {
if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator())) {
CallInst::Create(AsanUnpoisonGlobals, "", RI);
}
}
}
bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
Type *Ty = cast<PointerType>(G->getType())->getElementType();
DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
if (BL->isIn(*G)) return false;
if (!Ty->isSized()) return false;
if (!G->hasInitializer()) return false;
if (GlobalWasGeneratedByAsan(G)) return false; // Our own global.
// 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)
return false;
// 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())
return false;
// For now, just ignore this Global if the alignment is large.
if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
// 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);
return false;
}
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);
return false;
}
// 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);
return false;
}
}
return true;
}
void AddressSanitizerModule::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
// Declare our poisoning and unpoisoning functions.
AsanPoisonGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanPoisonGlobalsName, IRB.getVoidTy(), IntptrTy, NULL));
AsanPoisonGlobals->setLinkage(Function::ExternalLinkage);
AsanUnpoisonGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanUnpoisonGlobalsName, IRB.getVoidTy(), NULL));
AsanUnpoisonGlobals->setLinkage(Function::ExternalLinkage);
// Declare functions that register/unregister globals.
AsanRegisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanRegisterGlobalsName, IRB.getVoidTy(),
IntptrTy, IntptrTy, NULL));
AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);
AsanUnregisterGlobals = checkInterfaceFunction(M.getOrInsertFunction(
kAsanUnregisterGlobalsName,
IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);
}
// 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 AddressSanitizerModule::runOnModule(Module &M) {
if (!ClGlobals) return false;
TD = getAnalysisIfAvailable<DataLayout>();
if (!TD)
return false;
BL.reset(SpecialCaseList::createOrDie(BlacklistFile));
if (BL->isIn(M)) return false;
C = &(M.getContext());
int LongSize = TD->getPointerSizeInBits();
IntptrTy = Type::getIntNTy(*C, LongSize);
Mapping = getShadowMapping(M, LongSize, ZeroBaseShadow);
initializeCallbacks(M);
DynamicallyInitializedGlobals.Init(M);
SmallVector<GlobalVariable *, 16> GlobalsToChange;
for (Module::GlobalListType::iterator G = M.global_begin(),
E = M.global_end(); G != E; ++G) {
if (ShouldInstrumentGlobal(G))
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;
// const char *module_name;
// size_t has_dynamic_init;
// We initialize an array of such structures and pass it to a run-time call.
StructType *GlobalStructTy = StructType::get(IntptrTy, IntptrTy,
IntptrTy, IntptrTy,
IntptrTy, IntptrTy, NULL);
SmallVector<Constant *, 16> Initializers(n);
Function *CtorFunc = M.getFunction(kAsanModuleCtorName);
assert(CtorFunc);
IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());
bool HasDynamicallyInitializedGlobals = false;
GlobalVariable *ModuleName = createPrivateGlobalForString(
M, M.getModuleIdentifier());
// We shouldn't merge same module names, as this string serves as unique
// module ID in runtime.
ModuleName->setUnnamedAddr(false);
for (size_t i = 0; i < n; i++) {
static const uint64_t kMaxGlobalRedzone = 1 << 18;
GlobalVariable *G = GlobalsToChange[i];
PointerType *PtrTy = cast<PointerType>(G->getType());
Type *Ty = PtrTy->getElementType();
uint64_t SizeInBytes = TD->getTypeAllocSize(Ty);
uint64_t MinRZ = MinRedzoneSizeForGlobal();
// MinRZ <= RZ <= kMaxGlobalRedzone
// and trying to make RZ to be ~ 1/4 of SizeInBytes.
uint64_t RZ = std::max(MinRZ,
std::min(kMaxGlobalRedzone,
(SizeInBytes / MinRZ / 4) * MinRZ));
uint64_t RightRedzoneSize = RZ;
// Round up to MinRZ
if (SizeInBytes % MinRZ)
RightRedzoneSize += MinRZ - (SizeInBytes % MinRZ);
assert(((RightRedzoneSize + SizeInBytes) % MinRZ) == 0);
Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);
// Determine whether this global should be poisoned in initialization.
bool GlobalHasDynamicInitializer =
DynamicallyInitializedGlobals.Contains(G);
// Don't check initialization order if this global is blacklisted.
GlobalHasDynamicInitializer &= !BL->isIn(*G, "init");
StructType *NewTy = StructType::get(Ty, RightRedZoneTy, NULL);
Constant *NewInitializer = ConstantStruct::get(
NewTy, G->getInitializer(),
Constant::getNullValue(RightRedZoneTy), NULL);
GlobalVariable *Name = createPrivateGlobalForString(M, G->getName());
// Create a new global variable with enough space for a redzone.
GlobalValue::LinkageTypes Linkage = G->getLinkage();
if (G->isConstant() && Linkage == GlobalValue::PrivateLinkage)
Linkage = GlobalValue::InternalLinkage;
GlobalVariable *NewGlobal = new GlobalVariable(
M, NewTy, G->isConstant(), Linkage,
NewInitializer, "", G, G->getThreadLocalMode());
NewGlobal->copyAttributesFrom(G);
NewGlobal->setAlignment(MinRZ);
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),
ConstantExpr::getPointerCast(ModuleName, IntptrTy),
ConstantInt::get(IntptrTy, GlobalHasDynamicInitializer),
NULL);
// Populate the first and last globals declared in this TU.
if (CheckInitOrder && GlobalHasDynamicInitializer)
HasDynamicallyInitializedGlobals = true;
DEBUG(dbgs() << "NEW GLOBAL: " << *NewGlobal << "\n");
}
ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
GlobalVariable *AllGlobals = new GlobalVariable(
M, ArrayOfGlobalStructTy, false, GlobalVariable::InternalLinkage,
ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");
// Create calls for poisoning before initializers run and unpoisoning after.
if (CheckInitOrder && HasDynamicallyInitializedGlobals)
createInitializerPoisonCalls(M, ModuleName);
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));
IRB_Dtor.CreateCall2(AsanUnregisterGlobals,
IRB.CreatePointerCast(AllGlobals, IntptrTy),
ConstantInt::get(IntptrTy, n));
appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndCtorPriority);
DEBUG(dbgs() << M);
return true;
}
void AddressSanitizer::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
// 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.
AsanErrorCallback[AccessIsWrite][AccessSizeIndex] =
checkInterfaceFunction(M.getOrInsertFunction(
FunctionName, IRB.getVoidTy(), IntptrTy, NULL));
}
}
AsanErrorCallbackSized[0] = checkInterfaceFunction(M.getOrInsertFunction(
kAsanReportLoadN, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
AsanErrorCallbackSized[1] = checkInterfaceFunction(M.getOrInsertFunction(
kAsanReportStoreN, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
AsanHandleNoReturnFunc = checkInterfaceFunction(M.getOrInsertFunction(
kAsanHandleNoReturnName, IRB.getVoidTy(), NULL));
AsanCovFunction = checkInterfaceFunction(M.getOrInsertFunction(
kAsanCovName, 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);
}
void AddressSanitizer::emitShadowMapping(Module &M, IRBuilder<> &IRB) const {
// Tell the values of mapping offset and scale to the run-time.
GlobalValue *asan_mapping_offset =
new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
ConstantInt::get(IntptrTy, Mapping.Offset),
kAsanMappingOffsetName);
// Read the global, otherwise it may be optimized away.
IRB.CreateLoad(asan_mapping_offset, true);
GlobalValue *asan_mapping_scale =
new GlobalVariable(M, IntptrTy, true, GlobalValue::LinkOnceODRLinkage,
ConstantInt::get(IntptrTy, Mapping.Scale),
kAsanMappingScaleName);
// Read the global, otherwise it may be optimized away.
IRB.CreateLoad(asan_mapping_scale, true);
}
// virtual
bool AddressSanitizer::doInitialization(Module &M) {
// Initialize the private fields. No one has accessed them before.
TD = getAnalysisIfAvailable<DataLayout>();
if (!TD)
return false;
BL.reset(SpecialCaseList::createOrDie(BlacklistFile));
DynamicallyInitializedGlobals.Init(M);
C = &(M.getContext());
LongSize = TD->getPointerSizeInBits();
IntptrTy = Type::getIntNTy(*C, LongSize);
AsanCtorFunction = Function::Create(
FunctionType::get(Type::getVoidTy(*C), false),
GlobalValue::InternalLinkage, kAsanModuleCtorName, &M);
BasicBlock *AsanCtorBB = BasicBlock::Create(*C, "", AsanCtorFunction);
// call __asan_init in the module ctor.
IRBuilder<> IRB(ReturnInst::Create(*C, AsanCtorBB));
AsanInitFunction = checkInterfaceFunction(
M.getOrInsertFunction(kAsanInitName, IRB.getVoidTy(), NULL));
AsanInitFunction->setLinkage(Function::ExternalLinkage);
IRB.CreateCall(AsanInitFunction);
Mapping = getShadowMapping(M, LongSize, ZeroBaseShadow);
emitShadowMapping(M, IRB);
appendToGlobalCtors(M, AsanCtorFunction, kAsanCtorAndCtorPriority);
return true;
}
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;
}
// Poor man's coverage that works with ASan.
// We create a Guard boolean variable with the same linkage
// as the function and inject this code into the entry block:
// if (*Guard) {
// __sanitizer_cov(&F);
// *Guard = 1;
// }
// The accesses to Guard are atomic. The rest of the logic is
// in __sanitizer_cov (it's fine to call it more than once).
//
// This coverage implementation provides very limited data:
// it only tells if a given function was ever executed.
// No counters, no per-basic-block or per-edge data.
// But for many use cases this is what we need and the added slowdown
// is negligible. This simple implementation will probably be obsoleted
// by the upcoming Clang-based coverage implementation.
// By having it here and now we hope to
// a) get the functionality to users earlier and
// b) collect usage statistics to help improve Clang coverage design.
bool AddressSanitizer::InjectCoverage(Function &F) {
if (!ClCoverage) return false;
// Skip static allocas at the top of the entry block so they don't become
// dynamic when we split the block. If we used our optimized stack layout,
// then there will only be one alloca and it will come first.
BasicBlock &Entry = F.getEntryBlock();
BasicBlock::iterator IP = Entry.getFirstInsertionPt(), BE = Entry.end();
for (; IP != BE; ++IP) {
AllocaInst *AI = dyn_cast<AllocaInst>(IP);
if (!AI || !AI->isStaticAlloca())
break;
}
IRBuilder<> IRB(IP);
Type *Int8Ty = IRB.getInt8Ty();
GlobalVariable *Guard = new GlobalVariable(
*F.getParent(), Int8Ty, false, GlobalValue::PrivateLinkage,
Constant::getNullValue(Int8Ty), "__asan_gen_cov_" + F.getName());
LoadInst *Load = IRB.CreateLoad(Guard);
Load->setAtomic(Monotonic);
Load->setAlignment(1);
Value *Cmp = IRB.CreateICmpEQ(Constant::getNullValue(Int8Ty), Load);
Instruction *Ins = SplitBlockAndInsertIfThen(Cmp, IP, false);
IRB.SetInsertPoint(Ins);
// We pass &F to __sanitizer_cov. We could avoid this and rely on
// GET_CALLER_PC, but having the PC of the first instruction is just nice.
IRB.CreateCall(AsanCovFunction, IRB.CreatePointerCast(&F, IntptrTy));
StoreInst *Store = IRB.CreateStore(ConstantInt::get(Int8Ty, 1), Guard);
Store->setAtomic(Monotonic);
Store->setAlignment(1);
return true;
}
bool AddressSanitizer::runOnFunction(Function &F) {
if (BL->isIn(F)) return false;
if (&F == AsanCtorFunction) return false;
if (F.getLinkage() == GlobalValue::AvailableExternallyLinkage) return false;
DEBUG(dbgs() << "ASAN instrumenting:\n" << F << "\n");
initializeCallbacks(*F.getParent());
// If needed, insert __asan_init before checking for SanitizeAddress attr.
maybeInsertAsanInitAtFunctionEntry(F);
if (!F.hasFnAttribute(Attribute::SanitizeAddress))
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;
int NumAllocas = 0;
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 (isa<AllocaInst>(BI))
NumAllocas++;
CallSite CS(BI);
if (CS) {
// A call inside BB.
TempsToInstrument.clear();
if (CS.doesNotReturn())
NoReturnCalls.push_back(CS.getInstruction());
}
continue;
}
ToInstrument.push_back(BI);
NumInsnsPerBB++;
if (NumInsnsPerBB >= ClMaxInsnsToInstrumentPerBB)
break;
}
}
Function *UninstrumentedDuplicate = 0;
bool LikelyToInstrument =
!NoReturnCalls.empty() || !ToInstrument.empty() || (NumAllocas > 0);
if (ClKeepUninstrumented && LikelyToInstrument) {
ValueToValueMapTy VMap;
UninstrumentedDuplicate = CloneFunction(&F, VMap, false);
UninstrumentedDuplicate->removeFnAttr(Attribute::SanitizeAddress);
UninstrumentedDuplicate->setName("NOASAN_" + F.getName());
F.getParent()->getFunctionList().push_back(UninstrumentedDuplicate);
}
// 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(Inst);
else
instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
}
NumInstrumented++;
}
FunctionStackPoisoner FSP(F, *this);
bool ChangedStack = FSP.runOnFunction();
// 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(AsanHandleNoReturnFunc);
}
bool res = NumInstrumented > 0 || ChangedStack || !NoReturnCalls.empty();
if (InjectCoverage(F))
res = true;
DEBUG(dbgs() << "ASAN done instrumenting: " << res << " " << F << "\n");
if (ClKeepUninstrumented) {
if (!res) {
// No instrumentation is done, no need for the duplicate.
if (UninstrumentedDuplicate)
UninstrumentedDuplicate->eraseFromParent();
} else {
// The function was instrumented. We must have the duplicate.
assert(UninstrumentedDuplicate);
UninstrumentedDuplicate->setSection("NOASAN");
assert(!F.hasSection());
F.setSection("ASAN");
}
}
return res;
}
// 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;
}
void FunctionStackPoisoner::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
for (int i = 0; i <= kMaxAsanStackMallocSizeClass; i++) {
std::string Suffix = itostr(i);
AsanStackMallocFunc[i] = checkInterfaceFunction(
M.getOrInsertFunction(kAsanStackMallocNameTemplate + Suffix, IntptrTy,
IntptrTy, IntptrTy, NULL));
AsanStackFreeFunc[i] = checkInterfaceFunction(M.getOrInsertFunction(
kAsanStackFreeNameTemplate + Suffix, IRB.getVoidTy(), IntptrTy,
IntptrTy, IntptrTy, NULL));
}
AsanPoisonStackMemoryFunc = checkInterfaceFunction(M.getOrInsertFunction(
kAsanPoisonStackMemoryName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
AsanUnpoisonStackMemoryFunc = checkInterfaceFunction(M.getOrInsertFunction(
kAsanUnpoisonStackMemoryName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
}
void
FunctionStackPoisoner::poisonRedZones(const ArrayRef<uint8_t> ShadowBytes,
IRBuilder<> &IRB, Value *ShadowBase,
bool DoPoison) {
size_t n = ShadowBytes.size();
size_t LargeStoreSize = ASan.LongSize / 8;
size_t i;
for (i = 0; i + LargeStoreSize - 1 < n; i += LargeStoreSize) {
uint64_t Val = 0;
for (size_t j = 0; j < LargeStoreSize; j++) {
if (ASan.TD->isLittleEndian())
Val |= (uint64_t)ShadowBytes[i + j] << (8 * j);
else
Val = (Val << 8) | ShadowBytes[i + j];
}
if (!Val) continue;
Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
Value *Poison = ConstantInt::get(IntptrTy, DoPoison ? Val : 0);
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, IntptrPtrTy));
}
for (; i < n; i++) {
uint8_t Val = ShadowBytes[i];
if (!Val) continue;
Value *Ptr = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
Value *Poison = ConstantInt::get(IRB.getInt8Ty(), DoPoison ? Val : 0);
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, IRB.getInt8PtrTy()));
}
}
// Fake stack allocator (asan_fake_stack.h) has 11 size classes
// for every power of 2 from kMinStackMallocSize to kMaxAsanStackMallocSizeClass
static int StackMallocSizeClass(uint64_t LocalStackSize) {
assert(LocalStackSize <= kMaxStackMallocSize);
uint64_t MaxSize = kMinStackMallocSize;
for (int i = 0; ; i++, MaxSize *= 2)
if (LocalStackSize <= MaxSize)
return i;
llvm_unreachable("impossible LocalStackSize");
}
// Set Size bytes starting from ShadowBase to kAsanStackAfterReturnMagic.
// We can not use MemSet intrinsic because it may end up calling the actual
// memset. Size is a multiple of 8.
// Currently this generates 8-byte stores on x86_64; it may be better to
// generate wider stores.
void FunctionStackPoisoner::SetShadowToStackAfterReturnInlined(
IRBuilder<> &IRB, Value *ShadowBase, int Size) {
assert(!(Size % 8));
assert(kAsanStackAfterReturnMagic == 0xf5);
for (int i = 0; i < Size; i += 8) {
Value *p = IRB.CreateAdd(ShadowBase, ConstantInt::get(IntptrTy, i));
IRB.CreateStore(ConstantInt::get(IRB.getInt64Ty(), 0xf5f5f5f5f5f5f5f5ULL),
IRB.CreateIntToPtr(p, IRB.getInt64Ty()->getPointerTo()));
}
}
void FunctionStackPoisoner::poisonStack() {
int StackMallocIdx = -1;
assert(AllocaVec.size() > 0);
Instruction *InsBefore = AllocaVec[0];
IRBuilder<> IRB(InsBefore);
SmallVector<ASanStackVariableDescription, 16> SVD;
SVD.reserve(AllocaVec.size());
for (size_t i = 0, n = AllocaVec.size(); i < n; i++) {
AllocaInst *AI = AllocaVec[i];
ASanStackVariableDescription D = { AI->getName().data(),
getAllocaSizeInBytes(AI),
AI->getAlignment(), AI, 0};
SVD.push_back(D);
}
// Minimal header size (left redzone) is 4 pointers,
// i.e. 32 bytes on 64-bit platforms and 16 bytes in 32-bit platforms.
size_t MinHeaderSize = ASan.LongSize / 2;
ASanStackFrameLayout L;
ComputeASanStackFrameLayout(SVD, 1UL << Mapping.Scale, MinHeaderSize, &L);
DEBUG(dbgs() << L.DescriptionString << " --- " << L.FrameSize << "\n");
uint64_t LocalStackSize = L.FrameSize;
bool DoStackMalloc =
ASan.CheckUseAfterReturn && LocalStackSize <= kMaxStackMallocSize;
Type *ByteArrayTy = ArrayType::get(IRB.getInt8Ty(), LocalStackSize);
AllocaInst *MyAlloca =
new AllocaInst(ByteArrayTy, "MyAlloca", InsBefore);
assert((ClRealignStack & (ClRealignStack - 1)) == 0);
size_t FrameAlignment = std::max(L.FrameAlignment, (size_t)ClRealignStack);
MyAlloca->setAlignment(FrameAlignment);
assert(MyAlloca->isStaticAlloca());
Value *OrigStackBase = IRB.CreatePointerCast(MyAlloca, IntptrTy);
Value *LocalStackBase = OrigStackBase;
if (DoStackMalloc) {
// LocalStackBase = OrigStackBase
// if (__asan_option_detect_stack_use_after_return)
// LocalStackBase = __asan_stack_malloc_N(LocalStackBase, OrigStackBase);
StackMallocIdx = StackMallocSizeClass(LocalStackSize);
assert(StackMallocIdx <= kMaxAsanStackMallocSizeClass);
Constant *OptionDetectUAR = F.getParent()->getOrInsertGlobal(
kAsanOptionDetectUAR, IRB.getInt32Ty());
Value *Cmp = IRB.CreateICmpNE(IRB.CreateLoad(OptionDetectUAR),
Constant::getNullValue(IRB.getInt32Ty()));
Instruction *Term = SplitBlockAndInsertIfThen(Cmp, InsBefore, false);
BasicBlock *CmpBlock = cast<Instruction>(Cmp)->getParent();
IRBuilder<> IRBIf(Term);
LocalStackBase = IRBIf.CreateCall2(
AsanStackMallocFunc[StackMallocIdx],
ConstantInt::get(IntptrTy, LocalStackSize), OrigStackBase);
BasicBlock *SetBlock = cast<Instruction>(LocalStackBase)->getParent();
IRB.SetInsertPoint(InsBefore);
PHINode *Phi = IRB.CreatePHI(IntptrTy, 2);
Phi->addIncoming(OrigStackBase, CmpBlock);
Phi->addIncoming(LocalStackBase, SetBlock);
LocalStackBase = Phi;
}
// Insert poison calls for lifetime intrinsics for alloca.
bool HavePoisonedAllocas = false;
for (size_t i = 0, n = AllocaPoisonCallVec.size(); i < n; i++) {
const AllocaPoisonCall &APC = AllocaPoisonCallVec[i];
assert(APC.InsBefore);
assert(APC.AI);
IRBuilder<> IRB(APC.InsBefore);
poisonAlloca(APC.AI, APC.Size, IRB, APC.DoPoison);
HavePoisonedAllocas |= APC.DoPoison;
}
// Replace Alloca instructions with base+offset.
for (size_t i = 0, n = SVD.size(); i < n; i++) {
AllocaInst *AI = SVD[i].AI;
Value *NewAllocaPtr = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase,
ConstantInt::get(IntptrTy, SVD[i].Offset)),
AI->getType());
replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB);
AI->replaceAllUsesWith(NewAllocaPtr);
}
// The left-most redzone has enough space for at least 4 pointers.
// Write the Magic value to redzone[0].
Value *BasePlus0 = IRB.CreateIntToPtr(LocalStackBase, IntptrPtrTy);
IRB.CreateStore(ConstantInt::get(IntptrTy, kCurrentStackFrameMagic),
BasePlus0);
// Write the frame description constant to redzone[1].
Value *BasePlus1 = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, ASan.LongSize/8)),
IntptrPtrTy);
GlobalVariable *StackDescriptionGlobal =
createPrivateGlobalForString(*F.getParent(), L.DescriptionString);
Value *Description = IRB.CreatePointerCast(StackDescriptionGlobal,
IntptrTy);
IRB.CreateStore(Description, BasePlus1);
// Write the PC to redzone[2].
Value *BasePlus2 = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy,
2 * ASan.LongSize/8)),
IntptrPtrTy);
IRB.CreateStore(IRB.CreatePointerCast(&F, IntptrTy), BasePlus2);
// Poison the stack redzones at the entry.
Value *ShadowBase = ASan.memToShadow(LocalStackBase, IRB);
poisonRedZones(L.ShadowBytes, IRB, ShadowBase, true);
// 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.
poisonRedZones(L.ShadowBytes, IRBRet, ShadowBase, false);
if (DoStackMalloc) {
assert(StackMallocIdx >= 0);
// In use-after-return mode, mark the whole stack frame unaddressable.
if (StackMallocIdx <= 4) {
// For small sizes inline the whole thing:
// if LocalStackBase != OrigStackBase:
// memset(ShadowBase, kAsanStackAfterReturnMagic, ShadowSize);
// **SavedFlagPtr(LocalStackBase) = 0
// FIXME: if LocalStackBase != OrigStackBase don't call poisonRedZones.
Value *Cmp = IRBRet.CreateICmpNE(LocalStackBase, OrigStackBase);
TerminatorInst *PoisonTerm = SplitBlockAndInsertIfThen(Cmp, Ret, false);
IRBuilder<> IRBPoison(PoisonTerm);
int ClassSize = kMinStackMallocSize << StackMallocIdx;
SetShadowToStackAfterReturnInlined(IRBPoison, ShadowBase,
ClassSize >> Mapping.Scale);
Value *SavedFlagPtrPtr = IRBPoison.CreateAdd(
LocalStackBase,
ConstantInt::get(IntptrTy, ClassSize - ASan.LongSize / 8));
Value *SavedFlagPtr = IRBPoison.CreateLoad(
IRBPoison.CreateIntToPtr(SavedFlagPtrPtr, IntptrPtrTy));
IRBPoison.CreateStore(
Constant::getNullValue(IRBPoison.getInt8Ty()),
IRBPoison.CreateIntToPtr(SavedFlagPtr, IRBPoison.getInt8PtrTy()));
} else {
// For larger frames call __asan_stack_free_*.
IRBRet.CreateCall3(AsanStackFreeFunc[StackMallocIdx], LocalStackBase,
ConstantInt::get(IntptrTy, LocalStackSize),
OrigStackBase);
}
} else if (HavePoisonedAllocas) {
// If we poisoned some allocas in llvm.lifetime analysis,
// unpoison whole stack frame now.
assert(LocalStackBase == OrigStackBase);
poisonAlloca(LocalStackBase, LocalStackSize, IRBRet, false);
}
}
// We are done. Remove the old unused alloca instructions.
for (size_t i = 0, n = AllocaVec.size(); i < n; i++)
AllocaVec[i]->eraseFromParent();
}
void FunctionStackPoisoner::poisonAlloca(Value *V, uint64_t Size,
IRBuilder<> &IRB, bool DoPoison) {
// For now just insert the call to ASan runtime.
Value *AddrArg = IRB.CreatePointerCast(V, IntptrTy);
Value *SizeArg = ConstantInt::get(IntptrTy, Size);
IRB.CreateCall2(DoPoison ? AsanPoisonStackMemoryFunc
: AsanUnpoisonStackMemoryFunc,
AddrArg, SizeArg);
}
// Handling llvm.lifetime intrinsics for a given %alloca:
// (1) collect all llvm.lifetime.xxx(%size, %value) describing the alloca.
// (2) if %size is constant, poison memory for llvm.lifetime.end (to detect
// invalid accesses) and unpoison it for llvm.lifetime.start (the memory
// could be poisoned by previous llvm.lifetime.end instruction, as the
// variable may go in and out of scope several times, e.g. in loops).
// (3) if we poisoned at least one %alloca in a function,
// unpoison the whole stack frame at function exit.
AllocaInst *FunctionStackPoisoner::findAllocaForValue(Value *V) {
if (AllocaInst *AI = dyn_cast<AllocaInst>(V))
// We're intested only in allocas we can handle.
return isInterestingAlloca(*AI) ? AI : 0;
// See if we've already calculated (or started to calculate) alloca for a
// given value.
AllocaForValueMapTy::iterator I = AllocaForValue.find(V);
if (I != AllocaForValue.end())
return I->second;
// Store 0 while we're calculating alloca for value V to avoid
// infinite recursion if the value references itself.
AllocaForValue[V] = 0;
AllocaInst *Res = 0;
if (CastInst *CI = dyn_cast<CastInst>(V))
Res = findAllocaForValue(CI->getOperand(0));
else if (PHINode *PN = dyn_cast<PHINode>(V)) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *IncValue = PN->getIncomingValue(i);
// Allow self-referencing phi-nodes.
if (IncValue == PN) continue;
AllocaInst *IncValueAI = findAllocaForValue(IncValue);
// AI for incoming values should exist and should all be equal.
if (IncValueAI == 0 || (Res != 0 && IncValueAI != Res))
return 0;
Res = IncValueAI;
}
}
if (Res != 0)
AllocaForValue[V] = Res;
return Res;
}
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