RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-25 04:02:41 +01:00
Code Issues Projects Releases Wiki Activity
fa5973a54d
llvm-mirror/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
Florian Mayer fa5973a54d [hwasan] Use stack safety analysis. 
This avoids unnecessary instrumentation.

Reviewed By: eugenis, vitalybuka

Differential Revision: https://reviews.llvm.org/D105703
2021-07-22 12:04:54 +01:00

1697 lines
66 KiB
C++
Raw Blame History

//===- HWAddressSanitizer.cpp - detector of uninitialized reads -------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// This file is a part of HWAddressSanitizer, an address sanity checker
/// based on tagged addressing.
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Instrumentation/HWAddressSanitizer.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/StackSafetyAnalysis.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Instrumentation/AddressSanitizerCommon.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <sstream>
using namespace llvm;
#define DEBUG_TYPE "hwasan"
const char kHwasanModuleCtorName[] = "hwasan.module_ctor";
const char kHwasanNoteName[] = "hwasan.note";
const char kHwasanInitName[] = "__hwasan_init";
const char kHwasanPersonalityThunkName[] = "__hwasan_personality_thunk";
const char kHwasanShadowMemoryDynamicAddress[] =
"__hwasan_shadow_memory_dynamic_address";
// Accesses sizes are powers of two: 1, 2, 4, 8, 16.
static const size_t kNumberOfAccessSizes = 5;
static const size_t kDefaultShadowScale = 4;
static const uint64_t kDynamicShadowSentinel =
std::numeric_limits<uint64_t>::max();
static const unsigned kShadowBaseAlignment = 32;
static cl::opt<std::string>
ClMemoryAccessCallbackPrefix("hwasan-memory-access-callback-prefix",
cl::desc("Prefix for memory access callbacks"),
cl::Hidden, cl::init("__hwasan_"));
static cl::opt<bool> ClInstrumentWithCalls(
"hwasan-instrument-with-calls",
cl::desc("instrument reads and writes with callbacks"), cl::Hidden,
cl::init(false));
static cl::opt<bool> ClInstrumentReads("hwasan-instrument-reads",
cl::desc("instrument read instructions"),
cl::Hidden, cl::init(true));
static cl::opt<bool>
ClInstrumentWrites("hwasan-instrument-writes",
cl::desc("instrument write instructions"), cl::Hidden,
cl::init(true));
static cl::opt<bool> ClInstrumentAtomics(
"hwasan-instrument-atomics",
cl::desc("instrument atomic instructions (rmw, cmpxchg)"), cl::Hidden,
cl::init(true));
static cl::opt<bool> ClInstrumentByval("hwasan-instrument-byval",
cl::desc("instrument byval arguments"),
cl::Hidden, cl::init(true));
static cl::opt<bool>
ClRecover("hwasan-recover",
cl::desc("Enable recovery mode (continue-after-error)."),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClInstrumentStack("hwasan-instrument-stack",
cl::desc("instrument stack (allocas)"),
cl::Hidden, cl::init(true));
static cl::opt<bool>
ClUseStackSafety("hwasan-use-stack-safety", cl::Hidden, cl::init(true),
cl::Hidden, cl::desc("Use Stack Safety analysis results"),
cl::Optional);
static cl::opt<bool> ClUARRetagToZero(
"hwasan-uar-retag-to-zero",
cl::desc("Clear alloca tags before returning from the function to allow "
"non-instrumented and instrumented function calls mix. When set "
"to false, allocas are retagged before returning from the "
"function to detect use after return."),
cl::Hidden, cl::init(true));
static cl::opt<bool> ClGenerateTagsWithCalls(
"hwasan-generate-tags-with-calls",
cl::desc("generate new tags with runtime library calls"), cl::Hidden,
cl::init(false));
static cl::opt<bool> ClGlobals("hwasan-globals", cl::desc("Instrument globals"),
cl::Hidden, cl::init(false), cl::ZeroOrMore);
static cl::opt<int> ClMatchAllTag(
"hwasan-match-all-tag",
cl::desc("don't report bad accesses via pointers with this tag"),
cl::Hidden, cl::init(-1));
static cl::opt<bool>
ClEnableKhwasan("hwasan-kernel",
cl::desc("Enable KernelHWAddressSanitizer instrumentation"),
cl::Hidden, cl::init(false));
// These flags allow to change the shadow mapping and control how shadow memory
// is accessed. The shadow mapping looks like:
// Shadow = (Mem >> scale) + offset
static cl::opt<uint64_t>
ClMappingOffset("hwasan-mapping-offset",
cl::desc("HWASan shadow mapping offset [EXPERIMENTAL]"),
cl::Hidden, cl::init(0));
static cl::opt<bool>
ClWithIfunc("hwasan-with-ifunc",
cl::desc("Access dynamic shadow through an ifunc global on "
"platforms that support this"),
cl::Hidden, cl::init(false));
static cl::opt<bool> ClWithTls(
"hwasan-with-tls",
cl::desc("Access dynamic shadow through an thread-local pointer on "
"platforms that support this"),
cl::Hidden, cl::init(true));
static cl::opt<bool>
ClRecordStackHistory("hwasan-record-stack-history",
cl::desc("Record stack frames with tagged allocations "
"in a thread-local ring buffer"),
cl::Hidden, cl::init(true));
static cl::opt<bool>
ClInstrumentMemIntrinsics("hwasan-instrument-mem-intrinsics",
cl::desc("instrument memory intrinsics"),
cl::Hidden, cl::init(true));
static cl::opt<bool>
ClInstrumentLandingPads("hwasan-instrument-landing-pads",
cl::desc("instrument landing pads"), cl::Hidden,
cl::init(false), cl::ZeroOrMore);
static cl::opt<bool> ClUseShortGranules(
"hwasan-use-short-granules",
cl::desc("use short granules in allocas and outlined checks"), cl::Hidden,
cl::init(false), cl::ZeroOrMore);
static cl::opt<bool> ClInstrumentPersonalityFunctions(
"hwasan-instrument-personality-functions",
cl::desc("instrument personality functions"), cl::Hidden, cl::init(false),
cl::ZeroOrMore);
static cl::opt<bool> ClInlineAllChecks("hwasan-inline-all-checks",
cl::desc("inline all checks"),
cl::Hidden, cl::init(false));
// Enabled from clang by "-fsanitize-hwaddress-experimental-aliasing".
static cl::opt<bool> ClUsePageAliases("hwasan-experimental-use-page-aliases",
cl::desc("Use page aliasing in HWASan"),
cl::Hidden, cl::init(false));
namespace {
bool shouldUsePageAliases(const Triple &TargetTriple) {
return ClUsePageAliases && TargetTriple.getArch() == Triple::x86_64;
}
bool shouldInstrumentStack(const Triple &TargetTriple) {
return !shouldUsePageAliases(TargetTriple) && ClInstrumentStack;
}
bool shouldInstrumentWithCalls(const Triple &TargetTriple) {
return ClInstrumentWithCalls || TargetTriple.getArch() == Triple::x86_64;
}
bool mightUseStackSafetyAnalysis(bool DisableOptimization) {
return ClUseStackSafety.getNumOccurrences() ? ClUseStackSafety
: !DisableOptimization;
}
bool shouldUseStackSafetyAnalysis(const Triple &TargetTriple,
bool DisableOptimization) {
return shouldInstrumentStack(TargetTriple) &&
mightUseStackSafetyAnalysis(DisableOptimization);
}
/// An instrumentation pass implementing detection of addressability bugs
/// using tagged pointers.
class HWAddressSanitizer {
public:
HWAddressSanitizer(Module &M, bool CompileKernel, bool Recover,
const StackSafetyGlobalInfo *SSI)
: M(M), SSI(SSI) {
this->Recover = ClRecover.getNumOccurrences() > 0 ? ClRecover : Recover;
this->CompileKernel = ClEnableKhwasan.getNumOccurrences() > 0
? ClEnableKhwasan
: CompileKernel;
initializeModule();
}
void setSSI(const StackSafetyGlobalInfo *S) { SSI = S; }
bool sanitizeFunction(Function &F);
void initializeModule();
void createHwasanCtorComdat();
void initializeCallbacks(Module &M);
Value *getOpaqueNoopCast(IRBuilder<> &IRB, Value *Val);
Value *getDynamicShadowIfunc(IRBuilder<> &IRB);
Value *getShadowNonTls(IRBuilder<> &IRB);
void untagPointerOperand(Instruction *I, Value *Addr);
Value *memToShadow(Value *Shadow, IRBuilder<> &IRB);
void instrumentMemAccessInline(Value *Ptr, bool IsWrite,
unsigned AccessSizeIndex,
Instruction *InsertBefore);
void instrumentMemIntrinsic(MemIntrinsic *MI);
bool instrumentMemAccess(InterestingMemoryOperand &O);
bool ignoreAccess(Value *Ptr);
void getInterestingMemoryOperands(
Instruction *I, SmallVectorImpl<InterestingMemoryOperand> &Interesting);
bool isInterestingAlloca(const AllocaInst &AI);
bool tagAlloca(IRBuilder<> &IRB, AllocaInst *AI, Value *Tag, size_t Size);
Value *tagPointer(IRBuilder<> &IRB, Type *Ty, Value *PtrLong, Value *Tag);
Value *untagPointer(IRBuilder<> &IRB, Value *PtrLong);
bool instrumentStack(
SmallVectorImpl<AllocaInst *> &Allocas,
DenseMap<AllocaInst *, std::vector<DbgVariableIntrinsic *>> &AllocaDbgMap,
SmallVectorImpl<Instruction *> &RetVec, Value *StackTag);
Value *readRegister(IRBuilder<> &IRB, StringRef Name);
bool instrumentLandingPads(SmallVectorImpl<Instruction *> &RetVec);
Value *getNextTagWithCall(IRBuilder<> &IRB);
Value *getStackBaseTag(IRBuilder<> &IRB);
Value *getAllocaTag(IRBuilder<> &IRB, Value *StackTag, AllocaInst *AI,
unsigned AllocaNo);
Value *getUARTag(IRBuilder<> &IRB, Value *StackTag);
Value *getHwasanThreadSlotPtr(IRBuilder<> &IRB, Type *Ty);
Value *applyTagMask(IRBuilder<> &IRB, Value *OldTag);
unsigned retagMask(unsigned AllocaNo);
void emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord);
void instrumentGlobal(GlobalVariable *GV, uint8_t Tag);
void instrumentGlobals();
void instrumentPersonalityFunctions();
private:
LLVMContext *C;
Module &M;
const StackSafetyGlobalInfo *SSI;
Triple TargetTriple;
FunctionCallee HWAsanMemmove, HWAsanMemcpy, HWAsanMemset;
FunctionCallee HWAsanHandleVfork;
/// This struct defines the shadow mapping using the rule:
/// shadow = (mem >> Scale) + Offset.
/// If InGlobal is true, then
/// extern char __hwasan_shadow[];
/// shadow = (mem >> Scale) + &__hwasan_shadow
/// If InTls is true, then
/// extern char *__hwasan_tls;
/// shadow = (mem>>Scale) + align_up(__hwasan_shadow, kShadowBaseAlignment)
///
/// If WithFrameRecord is true, then __hwasan_tls will be used to access the
/// ring buffer for storing stack allocations on targets that support it.
struct ShadowMapping {
int Scale;
uint64_t Offset;
bool InGlobal;
bool InTls;
bool WithFrameRecord;
void init(Triple &TargetTriple, bool InstrumentWithCalls);
unsigned getObjectAlignment() const { return 1U << Scale; }
};
ShadowMapping Mapping;
Type *VoidTy = Type::getVoidTy(M.getContext());
Type *IntptrTy;
Type *Int8PtrTy;
Type *Int8Ty;
Type *Int32Ty;
Type *Int64Ty = Type::getInt64Ty(M.getContext());
bool CompileKernel;
bool Recover;
bool OutlinedChecks;
bool UseShortGranules;
bool InstrumentLandingPads;
bool InstrumentWithCalls;
bool InstrumentStack;
bool UsePageAliases;
bool HasMatchAllTag = false;
uint8_t MatchAllTag = 0;
unsigned PointerTagShift;
uint64_t TagMaskByte;
Function *HwasanCtorFunction;
FunctionCallee HwasanMemoryAccessCallback[2][kNumberOfAccessSizes];
FunctionCallee HwasanMemoryAccessCallbackSized[2];
FunctionCallee HwasanTagMemoryFunc;
FunctionCallee HwasanGenerateTagFunc;
Constant *ShadowGlobal;
Value *ShadowBase = nullptr;
Value *StackBaseTag = nullptr;
GlobalValue *ThreadPtrGlobal = nullptr;
};
class HWAddressSanitizerLegacyPass : public FunctionPass {
public:
// Pass identification, replacement for typeid.
static char ID;
explicit HWAddressSanitizerLegacyPass(bool CompileKernel = false,
bool Recover = false,
bool DisableOptimization = false)
: FunctionPass(ID), CompileKernel(CompileKernel), Recover(Recover) {
initializeHWAddressSanitizerLegacyPassPass(
*PassRegistry::getPassRegistry());
}
StringRef getPassName() const override { return "HWAddressSanitizer"; }
bool doInitialization(Module &M) override {
HWASan = std::make_unique<HWAddressSanitizer>(M, CompileKernel, Recover,
/*SSI=*/nullptr);
return true;
}
bool runOnFunction(Function &F) override {
if (shouldUseStackSafetyAnalysis(Triple(F.getParent()->getTargetTriple()),
DisableOptimization)) {
// We cannot call getAnalysis in doInitialization, that would cause a
// crash as the required analyses are not initialized yet.
HWASan->setSSI(
&getAnalysis<StackSafetyGlobalInfoWrapperPass>().getResult());
}
return HWASan->sanitizeFunction(F);
}
bool doFinalization(Module &M) override {
HWASan.reset();
return false;
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
// This is an over-estimation of, in case we are building for an
// architecture that doesn't allow stack tagging we will still load the
// analysis.
// This is so we don't need to plumb TargetTriple all the way to here.
if (mightUseStackSafetyAnalysis(DisableOptimization))
AU.addRequired<StackSafetyGlobalInfoWrapperPass>();
}
private:
std::unique_ptr<HWAddressSanitizer> HWASan;
bool CompileKernel;
bool Recover;
bool DisableOptimization;
};
} // end anonymous namespace
char HWAddressSanitizerLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(
HWAddressSanitizerLegacyPass, "hwasan",
"HWAddressSanitizer: detect memory bugs using tagged addressing.", false,
false)
INITIALIZE_PASS_END(
HWAddressSanitizerLegacyPass, "hwasan",
"HWAddressSanitizer: detect memory bugs using tagged addressing.", false,
false)
FunctionPass *
llvm::createHWAddressSanitizerLegacyPassPass(bool CompileKernel, bool Recover,
bool DisableOptimization) {
assert(!CompileKernel || Recover);
return new HWAddressSanitizerLegacyPass(CompileKernel, Recover,
DisableOptimization);
}
HWAddressSanitizerPass::HWAddressSanitizerPass(bool CompileKernel, bool Recover,
bool DisableOptimization)
: CompileKernel(CompileKernel), Recover(Recover),
DisableOptimization(DisableOptimization) {}
PreservedAnalyses HWAddressSanitizerPass::run(Module &M,
ModuleAnalysisManager &MAM) {
const StackSafetyGlobalInfo *SSI = nullptr;
if (shouldUseStackSafetyAnalysis(llvm::Triple(M.getTargetTriple()),
DisableOptimization))
SSI = &MAM.getResult<StackSafetyGlobalAnalysis>(M);
HWAddressSanitizer HWASan(M, CompileKernel, Recover, SSI);
bool Modified = false;
for (Function &F : M)
Modified |= HWASan.sanitizeFunction(F);
if (Modified)
return PreservedAnalyses::none();
return PreservedAnalyses::all();
}
void HWAddressSanitizer::createHwasanCtorComdat() {
std::tie(HwasanCtorFunction, std::ignore) =
getOrCreateSanitizerCtorAndInitFunctions(
M, kHwasanModuleCtorName, kHwasanInitName,
/*InitArgTypes=*/{},
/*InitArgs=*/{},
// This callback is invoked when the functions are created the first
// time. Hook them into the global ctors list in that case:
[&](Function *Ctor, FunctionCallee) {
Comdat *CtorComdat = M.getOrInsertComdat(kHwasanModuleCtorName);
Ctor->setComdat(CtorComdat);
appendToGlobalCtors(M, Ctor, 0, Ctor);
});
// Create a note that contains pointers to the list of global
// descriptors. Adding a note to the output file will cause the linker to
// create a PT_NOTE program header pointing to the note that we can use to
// find the descriptor list starting from the program headers. A function
// provided by the runtime initializes the shadow memory for the globals by
// accessing the descriptor list via the note. The dynamic loader needs to
// call this function whenever a library is loaded.
//
// The reason why we use a note for this instead of a more conventional
// approach of having a global constructor pass a descriptor list pointer to
// the runtime is because of an order of initialization problem. With
// constructors we can encounter the following problematic scenario:
//
// 1) library A depends on library B and also interposes one of B's symbols
// 2) B's constructors are called before A's (as required for correctness)
// 3) during construction, B accesses one of its "own" globals (actually
// interposed by A) and triggers a HWASAN failure due to the initialization
// for A not having happened yet
//
// Even without interposition it is possible to run into similar situations in
// cases where two libraries mutually depend on each other.
//
// We only need one note per binary, so put everything for the note in a
// comdat. This needs to be a comdat with an .init_array section to prevent
// newer versions of lld from discarding the note.
//
// Create the note even if we aren't instrumenting globals. This ensures that
// binaries linked from object files with both instrumented and
// non-instrumented globals will end up with a note, even if a comdat from an
// object file with non-instrumented globals is selected. The note is harmless
// if the runtime doesn't support it, since it will just be ignored.
Comdat *NoteComdat = M.getOrInsertComdat(kHwasanModuleCtorName);
Type *Int8Arr0Ty = ArrayType::get(Int8Ty, 0);
auto Start =
new GlobalVariable(M, Int8Arr0Ty, true, GlobalVariable::ExternalLinkage,
nullptr, "__start_hwasan_globals");
Start->setVisibility(GlobalValue::HiddenVisibility);
Start->setDSOLocal(true);
auto Stop =
new GlobalVariable(M, Int8Arr0Ty, true, GlobalVariable::ExternalLinkage,
nullptr, "__stop_hwasan_globals");
Stop->setVisibility(GlobalValue::HiddenVisibility);
Stop->setDSOLocal(true);
// Null-terminated so actually 8 bytes, which are required in order to align
// the note properly.
auto *Name = ConstantDataArray::get(*C, "LLVM\0\0\0");
auto *NoteTy = StructType::get(Int32Ty, Int32Ty, Int32Ty, Name->getType(),
Int32Ty, Int32Ty);
auto *Note =
new GlobalVariable(M, NoteTy, /*isConstant=*/true,
GlobalValue::PrivateLinkage, nullptr, kHwasanNoteName);
Note->setSection(".note.hwasan.globals");
Note->setComdat(NoteComdat);
Note->setAlignment(Align(4));
Note->setDSOLocal(true);
// The pointers in the note need to be relative so that the note ends up being
// placed in rodata, which is the standard location for notes.
auto CreateRelPtr = [&](Constant *Ptr) {
return ConstantExpr::getTrunc(
ConstantExpr::getSub(ConstantExpr::getPtrToInt(Ptr, Int64Ty),
ConstantExpr::getPtrToInt(Note, Int64Ty)),
Int32Ty);
};
Note->setInitializer(ConstantStruct::getAnon(
{ConstantInt::get(Int32Ty, 8), // n_namesz
ConstantInt::get(Int32Ty, 8), // n_descsz
ConstantInt::get(Int32Ty, ELF::NT_LLVM_HWASAN_GLOBALS), // n_type
Name, CreateRelPtr(Start), CreateRelPtr(Stop)}));
appendToCompilerUsed(M, Note);
// Create a zero-length global in hwasan_globals so that the linker will
// always create start and stop symbols.
auto Dummy = new GlobalVariable(
M, Int8Arr0Ty, /*isConstantGlobal*/ true, GlobalVariable::PrivateLinkage,
Constant::getNullValue(Int8Arr0Ty), "hwasan.dummy.global");
Dummy->setSection("hwasan_globals");
Dummy->setComdat(NoteComdat);
Dummy->setMetadata(LLVMContext::MD_associated,
MDNode::get(*C, ValueAsMetadata::get(Note)));
appendToCompilerUsed(M, Dummy);
}
/// Module-level initialization.
///
/// inserts a call to __hwasan_init to the module's constructor list.
void HWAddressSanitizer::initializeModule() {
LLVM_DEBUG(dbgs() << "Init " << M.getName() << "\n");
auto &DL = M.getDataLayout();
TargetTriple = Triple(M.getTargetTriple());
// x86_64 currently has two modes:
// - Intel LAM (default)
// - pointer aliasing (heap only)
bool IsX86_64 = TargetTriple.getArch() == Triple::x86_64;
UsePageAliases = shouldUsePageAliases(TargetTriple);
InstrumentWithCalls = shouldInstrumentWithCalls(TargetTriple);
InstrumentStack = shouldInstrumentStack(TargetTriple);
PointerTagShift = IsX86_64 ? 57 : 56;
TagMaskByte = IsX86_64 ? 0x3F : 0xFF;
Mapping.init(TargetTriple, InstrumentWithCalls);
C = &(M.getContext());
IRBuilder<> IRB(*C);
IntptrTy = IRB.getIntPtrTy(DL);
Int8PtrTy = IRB.getInt8PtrTy();
Int8Ty = IRB.getInt8Ty();
Int32Ty = IRB.getInt32Ty();
HwasanCtorFunction = nullptr;
// Older versions of Android do not have the required runtime support for
// short granules, global or personality function instrumentation. On other
// platforms we currently require using the latest version of the runtime.
bool NewRuntime =
!TargetTriple.isAndroid() || !TargetTriple.isAndroidVersionLT(30);
UseShortGranules =
ClUseShortGranules.getNumOccurrences() ? ClUseShortGranules : NewRuntime;
OutlinedChecks =
TargetTriple.isAArch64() && TargetTriple.isOSBinFormatELF() &&
(ClInlineAllChecks.getNumOccurrences() ? !ClInlineAllChecks : !Recover);
if (ClMatchAllTag.getNumOccurrences()) {
if (ClMatchAllTag != -1) {
HasMatchAllTag = true;
MatchAllTag = ClMatchAllTag & 0xFF;
}
} else if (CompileKernel) {
HasMatchAllTag = true;
MatchAllTag = 0xFF;
}
// If we don't have personality function support, fall back to landing pads.
InstrumentLandingPads = ClInstrumentLandingPads.getNumOccurrences()
? ClInstrumentLandingPads
: !NewRuntime;
if (!CompileKernel) {
createHwasanCtorComdat();
bool InstrumentGlobals =
ClGlobals.getNumOccurrences() ? ClGlobals : NewRuntime;
if (InstrumentGlobals && !UsePageAliases)
instrumentGlobals();
bool InstrumentPersonalityFunctions =
ClInstrumentPersonalityFunctions.getNumOccurrences()
? ClInstrumentPersonalityFunctions
: NewRuntime;
if (InstrumentPersonalityFunctions)
instrumentPersonalityFunctions();
}
if (!TargetTriple.isAndroid()) {
Constant *C = M.getOrInsertGlobal("__hwasan_tls", IntptrTy, [&] {
auto *GV = new GlobalVariable(M, IntptrTy, /*isConstant=*/false,
GlobalValue::ExternalLinkage, nullptr,
"__hwasan_tls", nullptr,
GlobalVariable::InitialExecTLSModel);
appendToCompilerUsed(M, GV);
return GV;
});
ThreadPtrGlobal = cast<GlobalVariable>(C);
}
}
void HWAddressSanitizer::initializeCallbacks(Module &M) {
IRBuilder<> IRB(*C);
for (size_t AccessIsWrite = 0; AccessIsWrite <= 1; AccessIsWrite++) {
const std::string TypeStr = AccessIsWrite ? "store" : "load";
const std::string EndingStr = Recover ? "_noabort" : "";
HwasanMemoryAccessCallbackSized[AccessIsWrite] = M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + TypeStr + "N" + EndingStr,
FunctionType::get(IRB.getVoidTy(), {IntptrTy, IntptrTy}, false));
for (size_t AccessSizeIndex = 0; AccessSizeIndex < kNumberOfAccessSizes;
AccessSizeIndex++) {
HwasanMemoryAccessCallback[AccessIsWrite][AccessSizeIndex] =
M.getOrInsertFunction(
ClMemoryAccessCallbackPrefix + TypeStr +
itostr(1ULL << AccessSizeIndex) + EndingStr,
FunctionType::get(IRB.getVoidTy(), {IntptrTy}, false));
}
}
HwasanTagMemoryFunc = M.getOrInsertFunction(
"__hwasan_tag_memory", IRB.getVoidTy(), Int8PtrTy, Int8Ty, IntptrTy);
HwasanGenerateTagFunc =
M.getOrInsertFunction("__hwasan_generate_tag", Int8Ty);
ShadowGlobal = M.getOrInsertGlobal("__hwasan_shadow",
ArrayType::get(IRB.getInt8Ty(), 0));
const std::string MemIntrinCallbackPrefix =
CompileKernel ? std::string("") : ClMemoryAccessCallbackPrefix;
HWAsanMemmove = M.getOrInsertFunction(MemIntrinCallbackPrefix + "memmove",
IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IntptrTy);
HWAsanMemcpy = M.getOrInsertFunction(MemIntrinCallbackPrefix + "memcpy",
IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt8PtrTy(), IntptrTy);
HWAsanMemset = M.getOrInsertFunction(MemIntrinCallbackPrefix + "memset",
IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
IRB.getInt32Ty(), IntptrTy);
HWAsanHandleVfork =
M.getOrInsertFunction("__hwasan_handle_vfork", IRB.getVoidTy(), IntptrTy);
}
Value *HWAddressSanitizer::getOpaqueNoopCast(IRBuilder<> &IRB, Value *Val) {
// An empty inline asm with input reg == output reg.
// An opaque no-op cast, basically.
// This prevents code bloat as a result of rematerializing trivial definitions
// such as constants or global addresses at every load and store.
InlineAsm *Asm =
InlineAsm::get(FunctionType::get(Int8PtrTy, {Val->getType()}, false),
StringRef(""), StringRef("=r,0"),
/*hasSideEffects=*/false);
return IRB.CreateCall(Asm, {Val}, ".hwasan.shadow");
}
Value *HWAddressSanitizer::getDynamicShadowIfunc(IRBuilder<> &IRB) {
return getOpaqueNoopCast(IRB, ShadowGlobal);
}
Value *HWAddressSanitizer::getShadowNonTls(IRBuilder<> &IRB) {
if (Mapping.Offset != kDynamicShadowSentinel)
return getOpaqueNoopCast(
IRB, ConstantExpr::getIntToPtr(
ConstantInt::get(IntptrTy, Mapping.Offset), Int8PtrTy));
if (Mapping.InGlobal) {
return getDynamicShadowIfunc(IRB);
} else {
Value *GlobalDynamicAddress =
IRB.GetInsertBlock()->getParent()->getParent()->getOrInsertGlobal(
kHwasanShadowMemoryDynamicAddress, Int8PtrTy);
return IRB.CreateLoad(Int8PtrTy, GlobalDynamicAddress);
}
}
bool HWAddressSanitizer::ignoreAccess(Value *Ptr) {
// Do not instrument acesses from different address spaces; we cannot deal
// with them.
Type *PtrTy = cast<PointerType>(Ptr->getType()->getScalarType());
if (PtrTy->getPointerAddressSpace() != 0)
return true;
// Ignore swifterror addresses.
// swifterror memory addresses are mem2reg promoted by instruction
// selection. As such they cannot have regular uses like an instrumentation
// function and it makes no sense to track them as memory.
if (Ptr->isSwiftError())
return true;
return false;
}
void HWAddressSanitizer::getInterestingMemoryOperands(
Instruction *I, SmallVectorImpl<InterestingMemoryOperand> &Interesting) {
// Skip memory accesses inserted by another instrumentation.
if (I->hasMetadata("nosanitize"))
return;
// Do not instrument the load fetching the dynamic shadow address.
if (ShadowBase == I)
return;
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (!ClInstrumentReads || ignoreAccess(LI->getPointerOperand()))
return;
Interesting.emplace_back(I, LI->getPointerOperandIndex(), false,
LI->getType(), LI->getAlign());
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (!ClInstrumentWrites || ignoreAccess(SI->getPointerOperand()))
return;
Interesting.emplace_back(I, SI->getPointerOperandIndex(), true,
SI->getValueOperand()->getType(), SI->getAlign());
} else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I)) {
if (!ClInstrumentAtomics || ignoreAccess(RMW->getPointerOperand()))
return;
Interesting.emplace_back(I, RMW->getPointerOperandIndex(), true,
RMW->getValOperand()->getType(), None);
} else if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!ClInstrumentAtomics || ignoreAccess(XCHG->getPointerOperand()))
return;
Interesting.emplace_back(I, XCHG->getPointerOperandIndex(), true,
XCHG->getCompareOperand()->getType(), None);
} else if (auto CI = dyn_cast<CallInst>(I)) {
for (unsigned ArgNo = 0; ArgNo < CI->getNumArgOperands(); ArgNo++) {
if (!ClInstrumentByval || !CI->isByValArgument(ArgNo) ||
ignoreAccess(CI->getArgOperand(ArgNo)))
continue;
Type *Ty = CI->getParamByValType(ArgNo);
Interesting.emplace_back(I, ArgNo, false, Ty, Align(1));
}
}
}
static unsigned getPointerOperandIndex(Instruction *I) {
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return LI->getPointerOperandIndex();
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->getPointerOperandIndex();
if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(I))
return RMW->getPointerOperandIndex();
if (AtomicCmpXchgInst *XCHG = dyn_cast<AtomicCmpXchgInst>(I))
return XCHG->getPointerOperandIndex();
report_fatal_error("Unexpected instruction");
return -1;
}
static size_t TypeSizeToSizeIndex(uint32_t TypeSize) {
size_t Res = countTrailingZeros(TypeSize / 8);
assert(Res < kNumberOfAccessSizes);
return Res;
}
void HWAddressSanitizer::untagPointerOperand(Instruction *I, Value *Addr) {
if (TargetTriple.isAArch64() || TargetTriple.getArch() == Triple::x86_64)
return;
IRBuilder<> IRB(I);
Value *AddrLong = IRB.CreatePointerCast(Addr, IntptrTy);
Value *UntaggedPtr =
IRB.CreateIntToPtr(untagPointer(IRB, AddrLong), Addr->getType());
I->setOperand(getPointerOperandIndex(I), UntaggedPtr);
}
Value *HWAddressSanitizer::memToShadow(Value *Mem, IRBuilder<> &IRB) {
// Mem >> Scale
Value *Shadow = IRB.CreateLShr(Mem, Mapping.Scale);
if (Mapping.Offset == 0)
return IRB.CreateIntToPtr(Shadow, Int8PtrTy);
// (Mem >> Scale) + Offset
return IRB.CreateGEP(Int8Ty, ShadowBase, Shadow);
}
void HWAddressSanitizer::instrumentMemAccessInline(Value *Ptr, bool IsWrite,
unsigned AccessSizeIndex,
Instruction *InsertBefore) {
assert(!UsePageAliases);
const int64_t AccessInfo =
(CompileKernel << HWASanAccessInfo::CompileKernelShift) +
(HasMatchAllTag << HWASanAccessInfo::HasMatchAllShift) +
(MatchAllTag << HWASanAccessInfo::MatchAllShift) +
(Recover << HWASanAccessInfo::RecoverShift) +
(IsWrite << HWASanAccessInfo::IsWriteShift) +
(AccessSizeIndex << HWASanAccessInfo::AccessSizeShift);
IRBuilder<> IRB(InsertBefore);
if (OutlinedChecks) {
Module *M = IRB.GetInsertBlock()->getParent()->getParent();
Ptr = IRB.CreateBitCast(Ptr, Int8PtrTy);
IRB.CreateCall(Intrinsic::getDeclaration(
M, UseShortGranules
? Intrinsic::hwasan_check_memaccess_shortgranules
: Intrinsic::hwasan_check_memaccess),
{ShadowBase, Ptr, ConstantInt::get(Int32Ty, AccessInfo)});
return;
}
Value *PtrLong = IRB.CreatePointerCast(Ptr, IntptrTy);
Value *PtrTag = IRB.CreateTrunc(IRB.CreateLShr(PtrLong, PointerTagShift),
IRB.getInt8Ty());
Value *AddrLong = untagPointer(IRB, PtrLong);
Value *Shadow = memToShadow(AddrLong, IRB);
Value *MemTag = IRB.CreateLoad(Int8Ty, Shadow);
Value *TagMismatch = IRB.CreateICmpNE(PtrTag, MemTag);
if (HasMatchAllTag) {
Value *TagNotIgnored = IRB.CreateICmpNE(
PtrTag, ConstantInt::get(PtrTag->getType(), MatchAllTag));
TagMismatch = IRB.CreateAnd(TagMismatch, TagNotIgnored);
}
Instruction *CheckTerm =
SplitBlockAndInsertIfThen(TagMismatch, InsertBefore, false,
MDBuilder(*C).createBranchWeights(1, 100000));
IRB.SetInsertPoint(CheckTerm);
Value *OutOfShortGranuleTagRange =
IRB.CreateICmpUGT(MemTag, ConstantInt::get(Int8Ty, 15));
Instruction *CheckFailTerm =
SplitBlockAndInsertIfThen(OutOfShortGranuleTagRange, CheckTerm, !Recover,
MDBuilder(*C).createBranchWeights(1, 100000));
IRB.SetInsertPoint(CheckTerm);
Value *PtrLowBits = IRB.CreateTrunc(IRB.CreateAnd(PtrLong, 15), Int8Ty);
PtrLowBits = IRB.CreateAdd(
PtrLowBits, ConstantInt::get(Int8Ty, (1 << AccessSizeIndex) - 1));
Value *PtrLowBitsOOB = IRB.CreateICmpUGE(PtrLowBits, MemTag);
SplitBlockAndInsertIfThen(PtrLowBitsOOB, CheckTerm, false,
MDBuilder(*C).createBranchWeights(1, 100000),
(DomTreeUpdater *)nullptr, nullptr,
CheckFailTerm->getParent());
IRB.SetInsertPoint(CheckTerm);
Value *InlineTagAddr = IRB.CreateOr(AddrLong, 15);
InlineTagAddr = IRB.CreateIntToPtr(InlineTagAddr, Int8PtrTy);
Value *InlineTag = IRB.CreateLoad(Int8Ty, InlineTagAddr);
Value *InlineTagMismatch = IRB.CreateICmpNE(PtrTag, InlineTag);
SplitBlockAndInsertIfThen(InlineTagMismatch, CheckTerm, false,
MDBuilder(*C).createBranchWeights(1, 100000),
(DomTreeUpdater *)nullptr, nullptr,
CheckFailTerm->getParent());
IRB.SetInsertPoint(CheckFailTerm);
InlineAsm *Asm;
switch (TargetTriple.getArch()) {
case Triple::x86_64:
// The signal handler will find the data address in rdi.
Asm = InlineAsm::get(
FunctionType::get(IRB.getVoidTy(), {PtrLong->getType()}, false),
"int3\nnopl " +
itostr(0x40 + (AccessInfo & HWASanAccessInfo::RuntimeMask)) +
"(%rax)",
"{rdi}",
/*hasSideEffects=*/true);
break;
case Triple::aarch64:
case Triple::aarch64_be:
// The signal handler will find the data address in x0.
Asm = InlineAsm::get(
FunctionType::get(IRB.getVoidTy(), {PtrLong->getType()}, false),
"brk #" + itostr(0x900 + (AccessInfo & HWASanAccessInfo::RuntimeMask)),
"{x0}",
/*hasSideEffects=*/true);
break;
default:
report_fatal_error("unsupported architecture");
}
IRB.CreateCall(Asm, PtrLong);
if (Recover)
cast<BranchInst>(CheckFailTerm)->setSuccessor(0, CheckTerm->getParent());
}
void HWAddressSanitizer::instrumentMemIntrinsic(MemIntrinsic *MI) {
IRBuilder<> IRB(MI);
if (isa<MemTransferInst>(MI)) {
IRB.CreateCall(
isa<MemMoveInst>(MI) ? HWAsanMemmove : HWAsanMemcpy,
{IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
IRB.CreatePointerCast(MI->getOperand(1), IRB.getInt8PtrTy()),
IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
} else if (isa<MemSetInst>(MI)) {
IRB.CreateCall(
HWAsanMemset,
{IRB.CreatePointerCast(MI->getOperand(0), IRB.getInt8PtrTy()),
IRB.CreateIntCast(MI->getOperand(1), IRB.getInt32Ty(), false),
IRB.CreateIntCast(MI->getOperand(2), IntptrTy, false)});
}
MI->eraseFromParent();
}
bool HWAddressSanitizer::instrumentMemAccess(InterestingMemoryOperand &O) {
Value *Addr = O.getPtr();
LLVM_DEBUG(dbgs() << "Instrumenting: " << O.getInsn() << "\n");
if (O.MaybeMask)
return false; // FIXME
IRBuilder<> IRB(O.getInsn());
if (isPowerOf2_64(O.TypeSize) &&
(O.TypeSize / 8 <= (1ULL << (kNumberOfAccessSizes - 1))) &&
(!O.Alignment || *O.Alignment >= (1ULL << Mapping.Scale) ||
*O.Alignment >= O.TypeSize / 8)) {
size_t AccessSizeIndex = TypeSizeToSizeIndex(O.TypeSize);
if (InstrumentWithCalls) {
IRB.CreateCall(HwasanMemoryAccessCallback[O.IsWrite][AccessSizeIndex],
IRB.CreatePointerCast(Addr, IntptrTy));
} else {
instrumentMemAccessInline(Addr, O.IsWrite, AccessSizeIndex, O.getInsn());
}
} else {
IRB.CreateCall(HwasanMemoryAccessCallbackSized[O.IsWrite],
{IRB.CreatePointerCast(Addr, IntptrTy),
ConstantInt::get(IntptrTy, O.TypeSize / 8)});
}
untagPointerOperand(O.getInsn(), Addr);
return true;
}
static uint64_t getAllocaSizeInBytes(const AllocaInst &AI) {
uint64_t ArraySize = 1;
if (AI.isArrayAllocation()) {
const ConstantInt *CI = dyn_cast<ConstantInt>(AI.getArraySize());
assert(CI && "non-constant array size");
ArraySize = CI->getZExtValue();
}
Type *Ty = AI.getAllocatedType();
uint64_t SizeInBytes = AI.getModule()->getDataLayout().getTypeAllocSize(Ty);
return SizeInBytes * ArraySize;
}
bool HWAddressSanitizer::tagAlloca(IRBuilder<> &IRB, AllocaInst *AI, Value *Tag,
size_t Size) {
size_t AlignedSize = alignTo(Size, Mapping.getObjectAlignment());
if (!UseShortGranules)
Size = AlignedSize;
Value *JustTag = IRB.CreateTrunc(Tag, IRB.getInt8Ty());
if (InstrumentWithCalls) {
IRB.CreateCall(HwasanTagMemoryFunc,
{IRB.CreatePointerCast(AI, Int8PtrTy), JustTag,
ConstantInt::get(IntptrTy, AlignedSize)});
} else {
size_t ShadowSize = Size >> Mapping.Scale;
Value *ShadowPtr = memToShadow(IRB.CreatePointerCast(AI, IntptrTy), IRB);
// If this memset is not inlined, it will be intercepted in the hwasan
// runtime library. That's OK, because the interceptor skips the checks if
// the address is in the shadow region.
// FIXME: the interceptor is not as fast as real memset. Consider lowering
// llvm.memset right here into either a sequence of stores, or a call to
// hwasan_tag_memory.
if (ShadowSize)
IRB.CreateMemSet(ShadowPtr, JustTag, ShadowSize, Align(1));
if (Size != AlignedSize) {
IRB.CreateStore(
ConstantInt::get(Int8Ty, Size % Mapping.getObjectAlignment()),
IRB.CreateConstGEP1_32(Int8Ty, ShadowPtr, ShadowSize));
IRB.CreateStore(JustTag, IRB.CreateConstGEP1_32(
Int8Ty, IRB.CreateBitCast(AI, Int8PtrTy),
AlignedSize - 1));
}
}
return true;
}
unsigned HWAddressSanitizer::retagMask(unsigned AllocaNo) {
if (TargetTriple.getArch() == Triple::x86_64)
return AllocaNo & TagMaskByte;
// A list of 8-bit numbers that have at most one run of non-zero bits.
// x = x ^ (mask << 56) can be encoded as a single armv8 instruction for these
// masks.
// The list does not include the value 255, which is used for UAR.
//
// Because we are more likely to use earlier elements of this list than later
// ones, it is sorted in increasing order of probability of collision with a
// mask allocated (temporally) nearby. The program that generated this list
// can be found at:
// https://github.com/google/sanitizers/blob/master/hwaddress-sanitizer/sort_masks.py
static unsigned FastMasks[] = {0, 128, 64, 192, 32, 96, 224, 112, 240,
48, 16, 120, 248, 56, 24, 8, 124, 252,
60, 28, 12, 4, 126, 254, 62, 30, 14,
6, 2, 127, 63, 31, 15, 7, 3, 1};
return FastMasks[AllocaNo % (sizeof(FastMasks) / sizeof(FastMasks[0]))];
}
Value *HWAddressSanitizer::applyTagMask(IRBuilder<> &IRB, Value *OldTag) {
if (TargetTriple.getArch() == Triple::x86_64) {
Constant *TagMask = ConstantInt::get(IntptrTy, TagMaskByte);
Value *NewTag = IRB.CreateAnd(OldTag, TagMask);
return NewTag;
}
// aarch64 uses 8-bit tags, so no mask is needed.
return OldTag;
}
Value *HWAddressSanitizer::getNextTagWithCall(IRBuilder<> &IRB) {
return IRB.CreateZExt(IRB.CreateCall(HwasanGenerateTagFunc), IntptrTy);
}
Value *HWAddressSanitizer::getStackBaseTag(IRBuilder<> &IRB) {
if (ClGenerateTagsWithCalls)
return getNextTagWithCall(IRB);
if (StackBaseTag)
return StackBaseTag;
// FIXME: use addressofreturnaddress (but implement it in aarch64 backend
// first).
Module *M = IRB.GetInsertBlock()->getParent()->getParent();
auto GetStackPointerFn = Intrinsic::getDeclaration(
M, Intrinsic::frameaddress,
IRB.getInt8PtrTy(M->getDataLayout().getAllocaAddrSpace()));
Value *StackPointer = IRB.CreateCall(
GetStackPointerFn, {Constant::getNullValue(IRB.getInt32Ty())});
// Extract some entropy from the stack pointer for the tags.
// Take bits 20..28 (ASLR entropy) and xor with bits 0..8 (these differ
// between functions).
Value *StackPointerLong = IRB.CreatePointerCast(StackPointer, IntptrTy);
Value *StackTag =
applyTagMask(IRB, IRB.CreateXor(StackPointerLong,
IRB.CreateLShr(StackPointerLong, 20)));
StackTag->setName("hwasan.stack.base.tag");
return StackTag;
}
Value *HWAddressSanitizer::getAllocaTag(IRBuilder<> &IRB, Value *StackTag,
AllocaInst *AI, unsigned AllocaNo) {
if (ClGenerateTagsWithCalls)
return getNextTagWithCall(IRB);
return IRB.CreateXor(StackTag,
ConstantInt::get(IntptrTy, retagMask(AllocaNo)));
}
Value *HWAddressSanitizer::getUARTag(IRBuilder<> &IRB, Value *StackTag) {
if (ClUARRetagToZero)
return ConstantInt::get(IntptrTy, 0);
if (ClGenerateTagsWithCalls)
return getNextTagWithCall(IRB);
return IRB.CreateXor(StackTag, ConstantInt::get(IntptrTy, TagMaskByte));
}
// Add a tag to an address.
Value *HWAddressSanitizer::tagPointer(IRBuilder<> &IRB, Type *Ty,
Value *PtrLong, Value *Tag) {
assert(!UsePageAliases);
Value *TaggedPtrLong;
if (CompileKernel) {
// Kernel addresses have 0xFF in the most significant byte.
Value *ShiftedTag =
IRB.CreateOr(IRB.CreateShl(Tag, PointerTagShift),
ConstantInt::get(IntptrTy, (1ULL << PointerTagShift) - 1));
TaggedPtrLong = IRB.CreateAnd(PtrLong, ShiftedTag);
} else {
// Userspace can simply do OR (tag << PointerTagShift);
Value *ShiftedTag = IRB.CreateShl(Tag, PointerTagShift);
TaggedPtrLong = IRB.CreateOr(PtrLong, ShiftedTag);
}
return IRB.CreateIntToPtr(TaggedPtrLong, Ty);
}
// Remove tag from an address.
Value *HWAddressSanitizer::untagPointer(IRBuilder<> &IRB, Value *PtrLong) {
assert(!UsePageAliases);
Value *UntaggedPtrLong;
if (CompileKernel) {
// Kernel addresses have 0xFF in the most significant byte.
UntaggedPtrLong =
IRB.CreateOr(PtrLong, ConstantInt::get(PtrLong->getType(),
0xFFULL << PointerTagShift));
} else {
// Userspace addresses have 0x00.
UntaggedPtrLong =
IRB.CreateAnd(PtrLong, ConstantInt::get(PtrLong->getType(),
~(0xFFULL << PointerTagShift)));
}
return UntaggedPtrLong;
}
Value *HWAddressSanitizer::getHwasanThreadSlotPtr(IRBuilder<> &IRB, Type *Ty) {
Module *M = IRB.GetInsertBlock()->getParent()->getParent();
if (TargetTriple.isAArch64() && TargetTriple.isAndroid()) {
// Android provides a fixed TLS slot for sanitizers. See TLS_SLOT_SANITIZER
// in Bionic's libc/private/bionic_tls.h.
Function *ThreadPointerFunc =
Intrinsic::getDeclaration(M, Intrinsic::thread_pointer);
Value *SlotPtr = IRB.CreatePointerCast(
IRB.CreateConstGEP1_32(IRB.getInt8Ty(),
IRB.CreateCall(ThreadPointerFunc), 0x30),
Ty->getPointerTo(0));
return SlotPtr;
}
if (ThreadPtrGlobal)
return ThreadPtrGlobal;
return nullptr;
}
void HWAddressSanitizer::emitPrologue(IRBuilder<> &IRB, bool WithFrameRecord) {
if (!Mapping.InTls)
ShadowBase = getShadowNonTls(IRB);
else if (!WithFrameRecord && TargetTriple.isAndroid())
ShadowBase = getDynamicShadowIfunc(IRB);
if (!WithFrameRecord && ShadowBase)
return;
Value *SlotPtr = getHwasanThreadSlotPtr(IRB, IntptrTy);
assert(SlotPtr);
Value *ThreadLong = IRB.CreateLoad(IntptrTy, SlotPtr);
// Extract the address field from ThreadLong. Unnecessary on AArch64 with TBI.
Value *ThreadLongMaybeUntagged =
TargetTriple.isAArch64() ? ThreadLong : untagPointer(IRB, ThreadLong);
if (WithFrameRecord) {
Function *F = IRB.GetInsertBlock()->getParent();
StackBaseTag = IRB.CreateAShr(ThreadLong, 3);
// Prepare ring buffer data.
Value *PC;
if (TargetTriple.getArch() == Triple::aarch64)
PC = readRegister(IRB, "pc");
else
PC = IRB.CreatePtrToInt(F, IntptrTy);
Module *M = F->getParent();
auto GetStackPointerFn = Intrinsic::getDeclaration(
M, Intrinsic::frameaddress,
IRB.getInt8PtrTy(M->getDataLayout().getAllocaAddrSpace()));
Value *SP = IRB.CreatePtrToInt(
IRB.CreateCall(GetStackPointerFn,
{Constant::getNullValue(IRB.getInt32Ty())}),
IntptrTy);
// Mix SP and PC.
// Assumptions:
// PC is 0x0000PPPPPPPPPPPP (48 bits are meaningful, others are zero)
// SP is 0xsssssssssssSSSS0 (4 lower bits are zero)
// We only really need ~20 lower non-zero bits (SSSS), so we mix like this:
// 0xSSSSPPPPPPPPPPPP
SP = IRB.CreateShl(SP, 44);
// Store data to ring buffer.
Value *RecordPtr =
IRB.CreateIntToPtr(ThreadLongMaybeUntagged, IntptrTy->getPointerTo(0));
IRB.CreateStore(IRB.CreateOr(PC, SP), RecordPtr);
// Update the ring buffer. Top byte of ThreadLong defines the size of the
// buffer in pages, it must be a power of two, and the start of the buffer
// must be aligned by twice that much. Therefore wrap around of the ring
// buffer is simply Addr &= ~((ThreadLong >> 56) << 12).
// The use of AShr instead of LShr is due to
// https://bugs.llvm.org/show_bug.cgi?id=39030
// Runtime library makes sure not to use the highest bit.
Value *WrapMask = IRB.CreateXor(
IRB.CreateShl(IRB.CreateAShr(ThreadLong, 56), 12, "", true, true),
ConstantInt::get(IntptrTy, (uint64_t)-1));
Value *ThreadLongNew = IRB.CreateAnd(
IRB.CreateAdd(ThreadLong, ConstantInt::get(IntptrTy, 8)), WrapMask);
IRB.CreateStore(ThreadLongNew, SlotPtr);
}
if (!ShadowBase) {
// Get shadow base address by aligning RecordPtr up.
// Note: this is not correct if the pointer is already aligned.
// Runtime library will make sure this never happens.
ShadowBase = IRB.CreateAdd(
IRB.CreateOr(
ThreadLongMaybeUntagged,
ConstantInt::get(IntptrTy, (1ULL << kShadowBaseAlignment) - 1)),
ConstantInt::get(IntptrTy, 1), "hwasan.shadow");
ShadowBase = IRB.CreateIntToPtr(ShadowBase, Int8PtrTy);
}
}
Value *HWAddressSanitizer::readRegister(IRBuilder<> &IRB, StringRef Name) {
Module *M = IRB.GetInsertBlock()->getParent()->getParent();
Function *ReadRegister =
Intrinsic::getDeclaration(M, Intrinsic::read_register, IntptrTy);
MDNode *MD = MDNode::get(*C, {MDString::get(*C, Name)});
Value *Args[] = {MetadataAsValue::get(*C, MD)};
return IRB.CreateCall(ReadRegister, Args);
}
bool HWAddressSanitizer::instrumentLandingPads(
SmallVectorImpl<Instruction *> &LandingPadVec) {
for (auto *LP : LandingPadVec) {
IRBuilder<> IRB(LP->getNextNode());
IRB.CreateCall(
HWAsanHandleVfork,
{readRegister(IRB, (TargetTriple.getArch() == Triple::x86_64) ? "rsp"
: "sp")});
}
return true;
}
bool HWAddressSanitizer::instrumentStack(
SmallVectorImpl<AllocaInst *> &Allocas,
DenseMap<AllocaInst *, std::vector<DbgVariableIntrinsic *>> &AllocaDbgMap,
SmallVectorImpl<Instruction *> &RetVec, Value *StackTag) {
// Ideally, we want to calculate tagged stack base pointer, and rewrite all
// alloca addresses using that. Unfortunately, offsets are not known yet
// (unless we use ASan-style mega-alloca). Instead we keep the base tag in a
// temp, shift-OR it into each alloca address and xor with the retag mask.
// This generates one extra instruction per alloca use.
for (unsigned N = 0; N < Allocas.size(); ++N) {
auto *AI = Allocas[N];
IRBuilder<> IRB(AI->getNextNode());
// Replace uses of the alloca with tagged address.
Value *Tag = getAllocaTag(IRB, StackTag, AI, N);
Value *AILong = IRB.CreatePointerCast(AI, IntptrTy);
Value *Replacement = tagPointer(IRB, AI->getType(), AILong, Tag);
std::string Name =
AI->hasName() ? AI->getName().str() : "alloca." + itostr(N);
Replacement->setName(Name + ".hwasan");
AI->replaceUsesWithIf(Replacement,
[AILong](Use &U) { return U.getUser() != AILong; });
for (auto *DDI : AllocaDbgMap.lookup(AI)) {
// Prepend "tag_offset, N" to the dwarf expression.
// Tag offset logically applies to the alloca pointer, and it makes sense
// to put it at the beginning of the expression.
SmallVector<uint64_t, 8> NewOps = {dwarf::DW_OP_LLVM_tag_offset,
retagMask(N)};
for (size_t LocNo = 0; LocNo < DDI->getNumVariableLocationOps(); ++LocNo)
if (DDI->getVariableLocationOp(LocNo) == AI)
DDI->setExpression(DIExpression::appendOpsToArg(DDI->getExpression(),
NewOps, LocNo));
}
size_t Size = getAllocaSizeInBytes(*AI);
tagAlloca(IRB, AI, Tag, Size);
for (auto RI : RetVec) {
IRB.SetInsertPoint(RI);
// Re-tag alloca memory with the special UAR tag.
Value *Tag = getUARTag(IRB, StackTag);
tagAlloca(IRB, AI, Tag, alignTo(Size, Mapping.getObjectAlignment()));
}
}
return true;
}
bool HWAddressSanitizer::isInterestingAlloca(const AllocaInst &AI) {
return (AI.getAllocatedType()->isSized() &&
// FIXME: instrument dynamic allocas, too
AI.isStaticAlloca() &&
// alloca() may be called with 0 size, ignore it.
getAllocaSizeInBytes(AI) > 0 &&
// We are only interested in allocas not promotable to registers.
// Promotable allocas are common under -O0.
!isAllocaPromotable(&AI) &&
// inalloca allocas are not treated as static, and we don't want
// dynamic alloca instrumentation for them as well.
!AI.isUsedWithInAlloca() &&
// swifterror allocas are register promoted by ISel
!AI.isSwiftError()) &&
// safe allocas are not interesting
!(SSI && SSI->isSafe(AI));
}
bool HWAddressSanitizer::sanitizeFunction(Function &F) {
if (&F == HwasanCtorFunction)
return false;
if (!F.hasFnAttribute(Attribute::SanitizeHWAddress))
return false;
LLVM_DEBUG(dbgs() << "Function: " << F.getName() << "\n");
SmallVector<InterestingMemoryOperand, 16> OperandsToInstrument;
SmallVector<MemIntrinsic *, 16> IntrinToInstrument;
SmallVector<AllocaInst *, 8> AllocasToInstrument;
SmallVector<Instruction *, 8> RetVec;
SmallVector<Instruction *, 8> LandingPadVec;
DenseMap<AllocaInst *, std::vector<DbgVariableIntrinsic *>> AllocaDbgMap;
for (auto &BB : F) {
for (auto &Inst : BB) {
if (InstrumentStack)
if (AllocaInst *AI = dyn_cast<AllocaInst>(&Inst)) {
if (isInterestingAlloca(*AI))
AllocasToInstrument.push_back(AI);
continue;
}
if (isa<ReturnInst>(Inst) || isa<ResumeInst>(Inst) ||
isa<CleanupReturnInst>(Inst))
RetVec.push_back(&Inst);
if (auto *DVI = dyn_cast<DbgVariableIntrinsic>(&Inst)) {
for (Value *V : DVI->location_ops()) {
if (auto *Alloca = dyn_cast_or_null<AllocaInst>(V))
if (!AllocaDbgMap.count(Alloca) ||
AllocaDbgMap[Alloca].back() != DVI)
AllocaDbgMap[Alloca].push_back(DVI);
}
}
if (InstrumentLandingPads && isa<LandingPadInst>(Inst))
LandingPadVec.push_back(&Inst);
getInterestingMemoryOperands(&Inst, OperandsToInstrument);
if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(&Inst))
IntrinToInstrument.push_back(MI);
}
}
initializeCallbacks(*F.getParent());
bool Changed = false;
if (!LandingPadVec.empty())
Changed |= instrumentLandingPads(LandingPadVec);
if (AllocasToInstrument.empty() && F.hasPersonalityFn() &&
F.getPersonalityFn()->getName() == kHwasanPersonalityThunkName) {
// __hwasan_personality_thunk is a no-op for functions without an
// instrumented stack, so we can drop it.
F.setPersonalityFn(nullptr);
Changed = true;
}
if (AllocasToInstrument.empty() && OperandsToInstrument.empty() &&
IntrinToInstrument.empty())
return Changed;
assert(!ShadowBase);
Instruction *InsertPt = &*F.getEntryBlock().begin();
IRBuilder<> EntryIRB(InsertPt);
emitPrologue(EntryIRB,
/*WithFrameRecord*/ ClRecordStackHistory &&
Mapping.WithFrameRecord && !AllocasToInstrument.empty());
if (!AllocasToInstrument.empty()) {
Value *StackTag =
ClGenerateTagsWithCalls ? nullptr : getStackBaseTag(EntryIRB);
instrumentStack(AllocasToInstrument, AllocaDbgMap, RetVec, StackTag);
}
// Pad and align each of the allocas that we instrumented to stop small
// uninteresting allocas from hiding in instrumented alloca's padding and so
// that we have enough space to store real tags for short granules.
DenseMap<AllocaInst *, AllocaInst *> AllocaToPaddedAllocaMap;
for (AllocaInst *AI : AllocasToInstrument) {
uint64_t Size = getAllocaSizeInBytes(*AI);
uint64_t AlignedSize = alignTo(Size, Mapping.getObjectAlignment());
AI->setAlignment(
Align(std::max(AI->getAlignment(), Mapping.getObjectAlignment())));
if (Size != AlignedSize) {
Type *AllocatedType = AI->getAllocatedType();
if (AI->isArrayAllocation()) {
uint64_t ArraySize =
cast<ConstantInt>(AI->getArraySize())->getZExtValue();
AllocatedType = ArrayType::get(AllocatedType, ArraySize);
}
Type *TypeWithPadding = StructType::get(
AllocatedType, ArrayType::get(Int8Ty, AlignedSize - Size));
auto *NewAI = new AllocaInst(
TypeWithPadding, AI->getType()->getAddressSpace(), nullptr, "", AI);
NewAI->takeName(AI);
NewAI->setAlignment(AI->getAlign());
NewAI->setUsedWithInAlloca(AI->isUsedWithInAlloca());
NewAI->setSwiftError(AI->isSwiftError());
NewAI->copyMetadata(*AI);
auto *Bitcast = new BitCastInst(NewAI, AI->getType(), "", AI);
AI->replaceAllUsesWith(Bitcast);
AllocaToPaddedAllocaMap[AI] = NewAI;
}
}
if (!AllocaToPaddedAllocaMap.empty()) {
for (auto &BB : F) {
for (auto &Inst : BB) {
if (auto *DVI = dyn_cast<DbgVariableIntrinsic>(&Inst)) {
SmallDenseSet<Value *> LocationOps(DVI->location_ops().begin(),
DVI->location_ops().end());
for (Value *V : LocationOps) {
if (auto *AI = dyn_cast_or_null<AllocaInst>(V)) {
if (auto *NewAI = AllocaToPaddedAllocaMap.lookup(AI))
DVI->replaceVariableLocationOp(V, NewAI);
}
}
}
}
}
for (auto &P : AllocaToPaddedAllocaMap)
P.first->eraseFromParent();
}
// If we split the entry block, move any allocas that were originally in the
// entry block back into the entry block so that they aren't treated as
// dynamic allocas.
if (EntryIRB.GetInsertBlock() != &F.getEntryBlock()) {
InsertPt = &*F.getEntryBlock().begin();
for (auto II = EntryIRB.GetInsertBlock()->begin(),
IE = EntryIRB.GetInsertBlock()->end();
II != IE;) {
Instruction *I = &*II++;
if (auto *AI = dyn_cast<AllocaInst>(I))
if (isa<ConstantInt>(AI->getArraySize()))
I->moveBefore(InsertPt);
}
}
for (auto &Operand : OperandsToInstrument)
instrumentMemAccess(Operand);
if (ClInstrumentMemIntrinsics && !IntrinToInstrument.empty()) {
for (auto Inst : IntrinToInstrument)
instrumentMemIntrinsic(cast<MemIntrinsic>(Inst));
}
ShadowBase = nullptr;
StackBaseTag = nullptr;
return true;
}
void HWAddressSanitizer::instrumentGlobal(GlobalVariable *GV, uint8_t Tag) {
assert(!UsePageAliases);
Constant *Initializer = GV->getInitializer();
uint64_t SizeInBytes =
M.getDataLayout().getTypeAllocSize(Initializer->getType());
uint64_t NewSize = alignTo(SizeInBytes, Mapping.getObjectAlignment());
if (SizeInBytes != NewSize) {
// Pad the initializer out to the next multiple of 16 bytes and add the
// required short granule tag.
std::vector<uint8_t> Init(NewSize - SizeInBytes, 0);
Init.back() = Tag;
Constant *Padding = ConstantDataArray::get(*C, Init);
Initializer = ConstantStruct::getAnon({Initializer, Padding});
}
auto *NewGV = new GlobalVariable(M, Initializer->getType(), GV->isConstant(),
GlobalValue::ExternalLinkage, Initializer,
GV->getName() + ".hwasan");
NewGV->copyAttributesFrom(GV);
NewGV->setLinkage(GlobalValue::PrivateLinkage);
NewGV->copyMetadata(GV, 0);
NewGV->setAlignment(
MaybeAlign(std::max(GV->getAlignment(), Mapping.getObjectAlignment())));
// It is invalid to ICF two globals that have different tags. In the case
// where the size of the global is a multiple of the tag granularity the
// contents of the globals may be the same but the tags (i.e. symbol values)
// may be different, and the symbols are not considered during ICF. In the
// case where the size is not a multiple of the granularity, the short granule
// tags would discriminate two globals with different tags, but there would
// otherwise be nothing stopping such a global from being incorrectly ICF'd
// with an uninstrumented (i.e. tag 0) global that happened to have the short
// granule tag in the last byte.
NewGV->setUnnamedAddr(GlobalValue::UnnamedAddr::None);
// Descriptor format (assuming little-endian):
// bytes 0-3: relative address of global
// bytes 4-6: size of global (16MB ought to be enough for anyone, but in case
// it isn't, we create multiple descriptors)
// byte 7: tag
auto *DescriptorTy = StructType::get(Int32Ty, Int32Ty);
const uint64_t MaxDescriptorSize = 0xfffff0;
for (uint64_t DescriptorPos = 0; DescriptorPos < SizeInBytes;
DescriptorPos += MaxDescriptorSize) {
auto *Descriptor =
new GlobalVariable(M, DescriptorTy, true, GlobalValue::PrivateLinkage,
nullptr, GV->getName() + ".hwasan.descriptor");
auto *GVRelPtr = ConstantExpr::getTrunc(
ConstantExpr::getAdd(
ConstantExpr::getSub(
ConstantExpr::getPtrToInt(NewGV, Int64Ty),
ConstantExpr::getPtrToInt(Descriptor, Int64Ty)),
ConstantInt::get(Int64Ty, DescriptorPos)),
Int32Ty);
uint32_t Size = std::min(SizeInBytes - DescriptorPos, MaxDescriptorSize);
auto *SizeAndTag = ConstantInt::get(Int32Ty, Size | (uint32_t(Tag) << 24));
Descriptor->setComdat(NewGV->getComdat());
Descriptor->setInitializer(ConstantStruct::getAnon({GVRelPtr, SizeAndTag}));
Descriptor->setSection("hwasan_globals");
Descriptor->setMetadata(LLVMContext::MD_associated,
MDNode::get(*C, ValueAsMetadata::get(NewGV)));
appendToCompilerUsed(M, Descriptor);
}
Constant *Aliasee = ConstantExpr::getIntToPtr(
ConstantExpr::getAdd(
ConstantExpr::getPtrToInt(NewGV, Int64Ty),
ConstantInt::get(Int64Ty, uint64_t(Tag) << PointerTagShift)),
GV->getType());
auto *Alias = GlobalAlias::create(GV->getValueType(), GV->getAddressSpace(),
GV->getLinkage(), "", Aliasee, &M);
Alias->setVisibility(GV->getVisibility());
Alias->takeName(GV);
GV->replaceAllUsesWith(Alias);
GV->eraseFromParent();
}
static DenseSet<GlobalVariable *> getExcludedGlobals(Module &M) {
NamedMDNode *Globals = M.getNamedMetadata("llvm.asan.globals");
if (!Globals)
return DenseSet<GlobalVariable *>();
DenseSet<GlobalVariable *> Excluded(Globals->getNumOperands());
for (auto MDN : Globals->operands()) {
// Metadata node contains the global and the fields of "Entry".
assert(MDN->getNumOperands() == 5);
auto *V = mdconst::extract_or_null<Constant>(MDN->getOperand(0));
// The optimizer may optimize away a global entirely.
if (!V)
continue;
auto *StrippedV = V->stripPointerCasts();
auto *GV = dyn_cast<GlobalVariable>(StrippedV);
if (!GV)
continue;
ConstantInt *IsExcluded = mdconst::extract<ConstantInt>(MDN->getOperand(4));
if (IsExcluded->isOne())
Excluded.insert(GV);
}
return Excluded;
}
void HWAddressSanitizer::instrumentGlobals() {
std::vector<GlobalVariable *> Globals;
auto ExcludedGlobals = getExcludedGlobals(M);
for (GlobalVariable &GV : M.globals()) {
if (ExcludedGlobals.count(&GV))
continue;
if (GV.isDeclarationForLinker() || GV.getName().startswith("llvm.") ||
GV.isThreadLocal())
continue;
// Common symbols can't have aliases point to them, so they can't be tagged.
if (GV.hasCommonLinkage())
continue;
// Globals with custom sections may be used in __start_/__stop_ enumeration,
// which would be broken both by adding tags and potentially by the extra
// padding/alignment that we insert.
if (GV.hasSection())
continue;
Globals.push_back(&GV);
}
MD5 Hasher;
Hasher.update(M.getSourceFileName());
MD5::MD5Result Hash;
Hasher.final(Hash);
uint8_t Tag = Hash[0] & TagMaskByte;
for (GlobalVariable *GV : Globals) {
// Skip tag 0 in order to avoid collisions with untagged memory.
if (Tag == 0)
Tag = 1;
instrumentGlobal(GV, Tag++);
}
}
void HWAddressSanitizer::instrumentPersonalityFunctions() {
// We need to untag stack frames as we unwind past them. That is the job of
// the personality function wrapper, which either wraps an existing
// personality function or acts as a personality function on its own. Each
// function that has a personality function or that can be unwound past has
// its personality function changed to a thunk that calls the personality
// function wrapper in the runtime.
MapVector<Constant *, std::vector<Function *>> PersonalityFns;
for (Function &F : M) {
if (F.isDeclaration() || !F.hasFnAttribute(Attribute::SanitizeHWAddress))
continue;
if (F.hasPersonalityFn()) {
PersonalityFns[F.getPersonalityFn()->stripPointerCasts()].push_back(&F);
} else if (!F.hasFnAttribute(Attribute::NoUnwind)) {
PersonalityFns[nullptr].push_back(&F);
}
}
if (PersonalityFns.empty())
return;
FunctionCallee HwasanPersonalityWrapper = M.getOrInsertFunction(
"__hwasan_personality_wrapper", Int32Ty, Int32Ty, Int32Ty, Int64Ty,
Int8PtrTy, Int8PtrTy, Int8PtrTy, Int8PtrTy, Int8PtrTy);
FunctionCallee UnwindGetGR = M.getOrInsertFunction("_Unwind_GetGR", VoidTy);
FunctionCallee UnwindGetCFA = M.getOrInsertFunction("_Unwind_GetCFA", VoidTy);
for (auto &P : PersonalityFns) {
std::string ThunkName = kHwasanPersonalityThunkName;
if (P.first)
ThunkName += ("." + P.first->getName()).str();
FunctionType *ThunkFnTy = FunctionType::get(
Int32Ty, {Int32Ty, Int32Ty, Int64Ty, Int8PtrTy, Int8PtrTy}, false);
bool IsLocal = P.first && (!isa<GlobalValue>(P.first) ||
cast<GlobalValue>(P.first)->hasLocalLinkage());
auto *ThunkFn = Function::Create(ThunkFnTy,
IsLocal ? GlobalValue::InternalLinkage
: GlobalValue::LinkOnceODRLinkage,
ThunkName, &M);
if (!IsLocal) {
ThunkFn->setVisibility(GlobalValue::HiddenVisibility);
ThunkFn->setComdat(M.getOrInsertComdat(ThunkName));
}
auto *BB = BasicBlock::Create(*C, "entry", ThunkFn);
IRBuilder<> IRB(BB);
CallInst *WrapperCall = IRB.CreateCall(
HwasanPersonalityWrapper,
{ThunkFn->getArg(0), ThunkFn->getArg(1), ThunkFn->getArg(2),
ThunkFn->getArg(3), ThunkFn->getArg(4),
P.first ? IRB.CreateBitCast(P.first, Int8PtrTy)
: Constant::getNullValue(Int8PtrTy),
IRB.CreateBitCast(UnwindGetGR.getCallee(), Int8PtrTy),
IRB.CreateBitCast(UnwindGetCFA.getCallee(), Int8PtrTy)});
WrapperCall->setTailCall();
IRB.CreateRet(WrapperCall);
for (Function *F : P.second)
F->setPersonalityFn(ThunkFn);
}
}
void HWAddressSanitizer::ShadowMapping::init(Triple &TargetTriple,
bool InstrumentWithCalls) {
Scale = kDefaultShadowScale;
if (TargetTriple.isOSFuchsia()) {
// Fuchsia is always PIE, which means that the beginning of the address
// space is always available.
InGlobal = false;
InTls = false;
Offset = 0;
WithFrameRecord = true;
} else if (ClMappingOffset.getNumOccurrences() > 0) {
InGlobal = false;
InTls = false;
Offset = ClMappingOffset;
WithFrameRecord = false;
} else if (ClEnableKhwasan || InstrumentWithCalls) {
InGlobal = false;
InTls = false;
Offset = 0;
WithFrameRecord = false;
} else if (ClWithIfunc) {
InGlobal = true;
InTls = false;
Offset = kDynamicShadowSentinel;
WithFrameRecord = false;
} else if (ClWithTls) {
InGlobal = false;
InTls = true;
Offset = kDynamicShadowSentinel;
WithFrameRecord = true;
} else {
InGlobal = false;
InTls = false;
Offset = kDynamicShadowSentinel;
WithFrameRecord = false;
}
}
Reference in New Issue View Git Blame Copy Permalink