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llvm-6502/lib/Transforms/Instrumentation/AddressSanitizer.cpp
Kostya Serebryany 3386d25257 [asan] Optimize accesses to global arrays with constant index 
Summary:
Given a global array G[N], which is declared in this CU and has static initializer
avoid instrumenting accesses like G[i], where 'i' is a constant and 0<=i<N.
Also add a bit of stats.

This eliminates ~1% of instrumentations on SPEC2006
and also partially helps when asan is being run together with coverage.

Reviewers: samsonov

Reviewed By: samsonov

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1947

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192794 91177308-0d34-0410-b5e6-96231b3b80d8
2013-10-16 14:06:14 +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/raw_ostream.h"
#include "llvm/Support/system_error.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 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";
// These constants must match the definitions in the run-time library.
static const int kAsanStackLeftRedzoneMagic = 0xf1;
static const int kAsanStackMidRedzoneMagic = 0xf2;
static const int kAsanStackRightRedzoneMagic = 0xf3;
static const int kAsanStackPartialRedzoneMagic = 0xf4;
#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> 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<bool> ClRealignStack("asan-realign-stack",
cl::desc("Realign stack to 32"), cl::Hidden, cl::init(true));
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 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;
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 RedzoneSize() 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;
uint64_t TotalStackSize;
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;
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),
TotalStackSize(0), 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);
uint64_t AlignedSize = getAlignedAllocaSize(&AI);
TotalStackSize += AlignedSize;
}
/// \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, 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.getAlignment() <= RedzoneSize() &&
AI.getAllocatedType()->isSized());
}
size_t RedzoneSize() const {
return RedzoneSizeForScale(Mapping.Scale);
}
uint64_t getAllocaSizeInBytes(AllocaInst *AI) const {
Type *Ty = AI->getAllocatedType();
uint64_t SizeInBytes = ASan.TD->getTypeAllocSize(Ty);
return SizeInBytes;
}
uint64_t getAlignedSize(uint64_t SizeInBytes) const {
size_t RZ = RedzoneSize();
return ((SizeInBytes + RZ - 1) / RZ) * RZ;
}
uint64_t getAlignedAllocaSize(AllocaInst *AI) const {
uint64_t SizeInBytes = getAllocaSizeInBytes(AI);
return getAlignedSize(SizeInBytes);
}
/// Finds alloca where the value comes from.
AllocaInst *findAllocaForValue(Value *V);
void poisonRedZones(const ArrayRef<AllocaInst*> &AllocaVec, 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(cast<Instruction>(Cmp), 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(cast<Instruction>(Cmp), 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(cast<Instruction>(Cmp), 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 Alloca if the alignment is large.
if (G->getAlignment() > RedzoneSize()) 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 = RedzoneSize();
// 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));
// 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;
}
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();
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;
}
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 RZSize,
size_t ShadowGranularity,
uint8_t Magic) {
for (size_t i = 0; i < RZSize;
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
}
}
}
// 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<AllocaInst*> &AllocaVec, IRBuilder<> &IRB, Value *ShadowBase,
bool DoPoison) {
size_t ShadowRZSize = RedzoneSize() >> Mapping.Scale;
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 >> Mapping.Scale) - ShadowRZSize));
size_t AddressableBytes = RedzoneSize() - (AlignedSize - SizeInBytes);
uint32_t Poison = 0;
if (DoPoison) {
PoisonShadowPartialRightRedzone((uint8_t*)&Poison, AddressableBytes,
RedzoneSize(),
1ULL << Mapping.Scale,
kAsanStackPartialRedzoneMagic);
Poison =
ASan.TD->isLittleEndian()
? support::endian::byte_swap<uint32_t, support::little>(Poison)
: support::endian::byte_swap<uint32_t, support::big>(Poison);
}
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 >> Mapping.Scale));
bool LastAlloca = (i == AllocaVec.size() - 1);
Value *Poison = LastAlloca ? PoisonRight : PoisonMid;
IRB.CreateStore(Poison, IRB.CreateIntToPtr(Ptr, RZPtrTy));
Pos += RedzoneSize();
}
}
// 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() {
uint64_t LocalStackSize = TotalStackSize +
(AllocaVec.size() + 1) * RedzoneSize();
bool DoStackMalloc = ASan.CheckUseAfterReturn
&& LocalStackSize <= kMaxStackMallocSize;
int StackMallocIdx = -1;
assert(AllocaVec.size() > 0);
Instruction *InsBefore = AllocaVec[0];
IRBuilder<> IRB(InsBefore);
Type *ByteArrayTy = ArrayType::get(IRB.getInt8Ty(), LocalStackSize);
AllocaInst *MyAlloca =
new AllocaInst(ByteArrayTy, "MyAlloca", InsBefore);
if (ClRealignStack && StackAlignment < RedzoneSize())
StackAlignment = RedzoneSize();
MyAlloca->setAlignment(StackAlignment);
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(cast<Instruction>(Cmp), 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;
}
// This string will be parsed by the run-time (DescribeAddressIfStack).
SmallString<2048> StackDescriptionStorage;
raw_svector_ostream StackDescription(StackDescriptionStorage);
StackDescription << AllocaVec.size() << " ";
// 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];
IntrinsicInst *II = APC.InsBefore;
AllocaInst *AI = findAllocaForValue(II->getArgOperand(1));
assert(AI);
IRBuilder<> IRB(II);
poisonAlloca(AI, APC.Size, IRB, APC.DoPoison);
HavePoisonedAllocas |= APC.DoPoison;
}
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);
Value *NewAllocaPtr = IRB.CreateIntToPtr(
IRB.CreateAdd(LocalStackBase, ConstantInt::get(IntptrTy, Pos)),
AI->getType());
replaceDbgDeclareForAlloca(AI, NewAllocaPtr, DIB);
AI->replaceAllUsesWith(NewAllocaPtr);
Pos += AlignedSize + RedzoneSize();
}
assert(Pos == LocalStackSize);
// 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(), StackDescription.str());
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(AllocaVec, 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(AllocaVec, 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(cast<Instruction>(Cmp), 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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