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//===- AArch64StackTagging.cpp - Stack tagging in IR --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
#include "AArch64.h"
#include "AArch64InstrInfo.h"
#include "AArch64Subtarget.h"
#include "AArch64TargetMachine.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/LiveRegUnits.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Metadata.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cassert>
#include <iterator>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "stack-tagging"
static constexpr unsigned kTagGranuleSize = 16;
namespace {
class AArch64StackTagging : public FunctionPass {
struct AllocaInfo {
AllocaInst *AI;
SmallVector<IntrinsicInst *, 2> LifetimeStart;
SmallVector<IntrinsicInst *, 2> LifetimeEnd;
SmallVector<DbgVariableIntrinsic *, 2> DbgVariableIntrinsics;
int Tag; // -1 for non-tagged allocations
};
public:
static char ID; // Pass ID, replacement for typeid
AArch64StackTagging() : FunctionPass(ID) {
initializeAArch64StackTaggingPass(*PassRegistry::getPassRegistry());
}
bool isInterestingAlloca(const AllocaInst &AI);
void alignAndPadAlloca(AllocaInfo &Info);
void tagAlloca(AllocaInst *AI, Instruction *InsertBefore, Value *Ptr,
uint64_t Size);
void untagAlloca(AllocaInst *AI, Instruction *InsertBefore, uint64_t Size);
Instruction *
insertBaseTaggedPointer(const MapVector<AllocaInst *, AllocaInfo> &Allocas,
const DominatorTree *DT);
bool runOnFunction(Function &F) override;
StringRef getPassName() const override { return "AArch64 Stack Tagging"; }
private:
Function *F;
Function *SetTagFunc;
const DataLayout *DL;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
}
};
} // end anonymous namespace
char AArch64StackTagging::ID = 0;
INITIALIZE_PASS_BEGIN(AArch64StackTagging, DEBUG_TYPE, "AArch64 Stack Tagging",
false, false)
INITIALIZE_PASS_END(AArch64StackTagging, DEBUG_TYPE, "AArch64 Stack Tagging",
false, false)
FunctionPass *llvm::createAArch64StackTaggingPass() {
return new AArch64StackTagging();
}
bool AArch64StackTagging::isInterestingAlloca(const AllocaInst &AI) {
// FIXME: support dynamic allocas
bool IsInteresting =
AI.getAllocatedType()->isSized() && AI.isStaticAlloca() &&
// alloca() may be called with 0 size, ignore it.
AI.getAllocationSizeInBits(*DL).getValue() > 0 &&
// 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();
return IsInteresting;
}
void AArch64StackTagging::tagAlloca(AllocaInst *AI, Instruction *InsertBefore,
Value *Ptr, uint64_t Size) {
IRBuilder<> IRB(InsertBefore);
IRB.CreateCall(SetTagFunc, {Ptr, ConstantInt::get(IRB.getInt64Ty(), Size)});
}
void AArch64StackTagging::untagAlloca(AllocaInst *AI, Instruction *InsertBefore,
uint64_t Size) {
IRBuilder<> IRB(InsertBefore);
IRB.CreateCall(SetTagFunc, {IRB.CreatePointerCast(AI, IRB.getInt8PtrTy()),
ConstantInt::get(IRB.getInt64Ty(), Size)});
}
Instruction *AArch64StackTagging::insertBaseTaggedPointer(
const MapVector<AllocaInst *, AllocaInfo> &Allocas,
const DominatorTree *DT) {
BasicBlock *PrologueBB = nullptr;
// Try sinking IRG as deep as possible to avoid hurting shrink wrap.
for (auto &I : Allocas) {
const AllocaInfo &Info = I.second;
AllocaInst *AI = Info.AI;
if (Info.Tag < 0)
continue;
if (!PrologueBB) {
PrologueBB = AI->getParent();
continue;
}
PrologueBB = DT->findNearestCommonDominator(PrologueBB, AI->getParent());
}
assert(PrologueBB);
IRBuilder<> IRB(&PrologueBB->front());
Function *IRG_SP =
Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_irg_sp);
Instruction *Base =
IRB.CreateCall(IRG_SP, {Constant::getNullValue(IRB.getInt64Ty())});
Base->setName("basetag");
return Base;
}
void AArch64StackTagging::alignAndPadAlloca(AllocaInfo &Info) {
unsigned NewAlignment = std::max(Info.AI->getAlignment(), kTagGranuleSize);
Info.AI->setAlignment(NewAlignment);
uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
uint64_t AlignedSize = alignTo(Size, kTagGranuleSize);
if (Size == AlignedSize)
return;
// Add padding to the alloca.
Type *AllocatedType =
Info.AI->isArrayAllocation()
? ArrayType::get(
Info.AI->getAllocatedType(),
dyn_cast<ConstantInt>(Info.AI->getArraySize())->getZExtValue())
: Info.AI->getAllocatedType();
Type *PaddingType =
ArrayType::get(Type::getInt8Ty(F->getContext()), AlignedSize - Size);
Type *TypeWithPadding = StructType::get(AllocatedType, PaddingType);
auto *NewAI = new AllocaInst(
TypeWithPadding, Info.AI->getType()->getAddressSpace(), nullptr, "", Info.AI);
NewAI->takeName(Info.AI);
NewAI->setAlignment(Info.AI->getAlignment());
NewAI->setUsedWithInAlloca(Info.AI->isUsedWithInAlloca());
NewAI->setSwiftError(Info.AI->isSwiftError());
NewAI->copyMetadata(*Info.AI);
auto *NewPtr = new BitCastInst(NewAI, Info.AI->getType(), "", Info.AI);
Info.AI->replaceAllUsesWith(NewPtr);
Info.AI->eraseFromParent();
Info.AI = NewAI;
}
// FIXME: check for MTE extension
bool AArch64StackTagging::runOnFunction(Function &Fn) {
if (!Fn.hasFnAttribute(Attribute::SanitizeMemTag))
return false;
F = &Fn;
DL = &Fn.getParent()->getDataLayout();
MapVector<AllocaInst *, AllocaInfo> Allocas; // need stable iteration order
SmallVector<Instruction *, 8> RetVec;
DenseMap<Value *, AllocaInst *> AllocaForValue;
SmallVector<Instruction *, 4> UnrecognizedLifetimes;
for (auto &BB : *F) {
for (BasicBlock::iterator IT = BB.begin(); IT != BB.end(); ++IT) {
Instruction *I = &*IT;
if (auto *AI = dyn_cast<AllocaInst>(I)) {
Allocas[AI].AI = AI;
continue;
}
if (auto *DVI = dyn_cast<DbgVariableIntrinsic>(I)) {
if (auto *AI =
dyn_cast_or_null<AllocaInst>(DVI->getVariableLocation())) {
Allocas[AI].DbgVariableIntrinsics.push_back(DVI);
}
continue;
}
auto *II = dyn_cast<IntrinsicInst>(I);
if (II && (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end)) {
AllocaInst *AI =
llvm::findAllocaForValue(II->getArgOperand(1), AllocaForValue);
if (!AI) {
UnrecognizedLifetimes.push_back(I);
continue;
}
if (II->getIntrinsicID() == Intrinsic::lifetime_start)
Allocas[AI].LifetimeStart.push_back(II);
else
Allocas[AI].LifetimeEnd.push_back(II);
}
if (isa<ReturnInst>(I) || isa<ResumeInst>(I) || isa<CleanupReturnInst>(I))
RetVec.push_back(I);
}
}
if (Allocas.empty())
return false;
int NextTag = 0;
int NumInterestingAllocas = 0;
for (auto &I : Allocas) {
AllocaInfo &Info = I.second;
assert(Info.AI);
if (!isInterestingAlloca(*Info.AI)) {
Info.Tag = -1;
continue;
}
alignAndPadAlloca(Info);
NumInterestingAllocas++;
Info.Tag = NextTag;
NextTag = (NextTag + 1) % 16;
}
if (NumInterestingAllocas == 0)
return true;
SetTagFunc =
Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_settag);
// Compute DT only if the function has the attribute, there are more than 1
// interesting allocas, and it is not available for free.
Instruction *Base;
if (NumInterestingAllocas > 1) {
auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>();
if (DTWP) {
Base = insertBaseTaggedPointer(Allocas, &DTWP->getDomTree());
} else {
DominatorTree DT(*F);
Base = insertBaseTaggedPointer(Allocas, &DT);
}
} else {
Base = insertBaseTaggedPointer(Allocas, nullptr);
}
for (auto &I : Allocas) {
const AllocaInfo &Info = I.second;
AllocaInst *AI = Info.AI;
if (Info.Tag < 0)
continue;
// Replace alloca with tagp(alloca).
IRBuilder<> IRB(Info.AI->getNextNode());
Function *TagP = Intrinsic::getDeclaration(
F->getParent(), Intrinsic::aarch64_tagp, {Info.AI->getType()});
Instruction *TagPCall =
IRB.CreateCall(TagP, {Constant::getNullValue(Info.AI->getType()), Base,
ConstantInt::get(IRB.getInt64Ty(), Info.Tag)});
if (Info.AI->hasName())
TagPCall->setName(Info.AI->getName() + ".tag");
Info.AI->replaceAllUsesWith(TagPCall);
TagPCall->setOperand(0, Info.AI);
if (UnrecognizedLifetimes.empty() && Info.LifetimeStart.size() == 1 &&
Info.LifetimeEnd.size() == 1) {
IntrinsicInst *Start = Info.LifetimeStart[0];
uint64_t Size =
dyn_cast<ConstantInt>(Start->getArgOperand(0))->getZExtValue();
Size = alignTo(Size, kTagGranuleSize);
tagAlloca(AI, Start->getNextNode(), Start->getArgOperand(1), Size);
untagAlloca(AI, Info.LifetimeEnd[0], Size);
} else {
uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
Value *Ptr = IRB.CreatePointerCast(TagPCall, IRB.getInt8PtrTy());
tagAlloca(AI, &*IRB.GetInsertPoint(), Ptr, Size);
for (auto &RI : RetVec) {
untagAlloca(AI, RI, Size);
}
// We may have inserted tag/untag outside of any lifetime interval.
// Remove all lifetime intrinsics for this alloca.
for (auto &II : Info.LifetimeStart)
II->eraseFromParent();
for (auto &II : Info.LifetimeEnd)
II->eraseFromParent();
}
// Fixup debug intrinsics to point to the new alloca.
for (auto DVI : Info.DbgVariableIntrinsics)
DVI->setArgOperand(
0,
MetadataAsValue::get(F->getContext(), LocalAsMetadata::get(Info.AI)));
}
// If we have instrumented at least one alloca, all unrecognized lifetime
// instrinsics have to go.
for (auto &I : UnrecognizedLifetimes)
I->eraseFromParent();
return true;
}