Bug Summary

File:llvm/lib/Target/AArch64/AArch64StackTagging.cpp
Warning:line 476, column 18
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name AArch64StackTagging.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -ffunction-sections -fdata-sections -fcoverage-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/build-llvm -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I lib/Target/AArch64 -I /build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Target/AArch64 -I include -I /build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/include -D NDEBUG -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/x86_64-linux-gnu/c++/10 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/backward -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/10/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-command-line-argument -Wno-unknown-warning-option -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir=/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/build-llvm -ferror-limit 19 -fvisibility hidden -fvisibility-inlines-hidden -fgnuc-version=4.2.1 -fcolor-diagnostics -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/scan-build-2021-09-26-234817-15343-1 -x c++ /build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Target/AArch64/AArch64StackTagging.cpp
1//===- AArch64StackTagging.cpp - Stack tagging in IR --===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//===----------------------------------------------------------------------===//
9
10#include "AArch64.h"
11#include "AArch64InstrInfo.h"
12#include "AArch64Subtarget.h"
13#include "AArch64TargetMachine.h"
14#include "llvm/ADT/DenseMap.h"
15#include "llvm/ADT/DepthFirstIterator.h"
16#include "llvm/ADT/MapVector.h"
17#include "llvm/ADT/None.h"
18#include "llvm/ADT/Optional.h"
19#include "llvm/ADT/SmallVector.h"
20#include "llvm/ADT/Statistic.h"
21#include "llvm/Analysis/AliasAnalysis.h"
22#include "llvm/Analysis/CFG.h"
23#include "llvm/Analysis/LoopInfo.h"
24#include "llvm/Analysis/PostDominators.h"
25#include "llvm/Analysis/ScalarEvolution.h"
26#include "llvm/Analysis/ScalarEvolutionExpressions.h"
27#include "llvm/Analysis/StackSafetyAnalysis.h"
28#include "llvm/Analysis/ValueTracking.h"
29#include "llvm/CodeGen/LiveRegUnits.h"
30#include "llvm/CodeGen/MachineBasicBlock.h"
31#include "llvm/CodeGen/MachineFunction.h"
32#include "llvm/CodeGen/MachineFunctionPass.h"
33#include "llvm/CodeGen/MachineInstr.h"
34#include "llvm/CodeGen/MachineInstrBuilder.h"
35#include "llvm/CodeGen/MachineLoopInfo.h"
36#include "llvm/CodeGen/MachineOperand.h"
37#include "llvm/CodeGen/MachineRegisterInfo.h"
38#include "llvm/CodeGen/TargetPassConfig.h"
39#include "llvm/CodeGen/TargetRegisterInfo.h"
40#include "llvm/IR/DebugLoc.h"
41#include "llvm/IR/Dominators.h"
42#include "llvm/IR/Function.h"
43#include "llvm/IR/GetElementPtrTypeIterator.h"
44#include "llvm/IR/IRBuilder.h"
45#include "llvm/IR/Instruction.h"
46#include "llvm/IR/Instructions.h"
47#include "llvm/IR/IntrinsicInst.h"
48#include "llvm/IR/IntrinsicsAArch64.h"
49#include "llvm/IR/Metadata.h"
50#include "llvm/InitializePasses.h"
51#include "llvm/Pass.h"
52#include "llvm/Support/Casting.h"
53#include "llvm/Support/Debug.h"
54#include "llvm/Support/raw_ostream.h"
55#include "llvm/Transforms/Instrumentation/AddressSanitizerCommon.h"
56#include "llvm/Transforms/Utils/Local.h"
57#include <cassert>
58#include <iterator>
59#include <utility>
60
61using namespace llvm;
62
63#define DEBUG_TYPE"aarch64-stack-tagging" "aarch64-stack-tagging"
64
65static cl::opt<bool> ClMergeInit(
66 "stack-tagging-merge-init", cl::Hidden, cl::init(true), cl::ZeroOrMore,
67 cl::desc("merge stack variable initializers with tagging when possible"));
68
69static cl::opt<bool>
70 ClUseStackSafety("stack-tagging-use-stack-safety", cl::Hidden,
71 cl::init(true), cl::ZeroOrMore,
72 cl::desc("Use Stack Safety analysis results"));
73
74static cl::opt<unsigned> ClScanLimit("stack-tagging-merge-init-scan-limit",
75 cl::init(40), cl::Hidden);
76
77static cl::opt<unsigned>
78 ClMergeInitSizeLimit("stack-tagging-merge-init-size-limit", cl::init(272),
79 cl::Hidden);
80
81static const Align kTagGranuleSize = Align(16);
82
83namespace {
84
85class InitializerBuilder {
86 uint64_t Size;
87 const DataLayout *DL;
88 Value *BasePtr;
89 Function *SetTagFn;
90 Function *SetTagZeroFn;
91 Function *StgpFn;
92
93 // List of initializers sorted by start offset.
94 struct Range {
95 uint64_t Start, End;
96 Instruction *Inst;
97 };
98 SmallVector<Range, 4> Ranges;
99 // 8-aligned offset => 8-byte initializer
100 // Missing keys are zero initialized.
101 std::map<uint64_t, Value *> Out;
102
103public:
104 InitializerBuilder(uint64_t Size, const DataLayout *DL, Value *BasePtr,
105 Function *SetTagFn, Function *SetTagZeroFn,
106 Function *StgpFn)
107 : Size(Size), DL(DL), BasePtr(BasePtr), SetTagFn(SetTagFn),
108 SetTagZeroFn(SetTagZeroFn), StgpFn(StgpFn) {}
109
110 bool addRange(uint64_t Start, uint64_t End, Instruction *Inst) {
111 auto I =
112 llvm::lower_bound(Ranges, Start, [](const Range &LHS, uint64_t RHS) {
113 return LHS.End <= RHS;
114 });
115 if (I != Ranges.end() && End > I->Start) {
116 // Overlap - bail.
117 return false;
118 }
119 Ranges.insert(I, {Start, End, Inst});
120 return true;
121 }
122
123 bool addStore(uint64_t Offset, StoreInst *SI, const DataLayout *DL) {
124 int64_t StoreSize = DL->getTypeStoreSize(SI->getOperand(0)->getType());
125 if (!addRange(Offset, Offset + StoreSize, SI))
126 return false;
127 IRBuilder<> IRB(SI);
128 applyStore(IRB, Offset, Offset + StoreSize, SI->getOperand(0));
129 return true;
130 }
131
132 bool addMemSet(uint64_t Offset, MemSetInst *MSI) {
133 uint64_t StoreSize = cast<ConstantInt>(MSI->getLength())->getZExtValue();
134 if (!addRange(Offset, Offset + StoreSize, MSI))
135 return false;
136 IRBuilder<> IRB(MSI);
137 applyMemSet(IRB, Offset, Offset + StoreSize,
138 cast<ConstantInt>(MSI->getValue()));
139 return true;
140 }
141
142 void applyMemSet(IRBuilder<> &IRB, int64_t Start, int64_t End,
143 ConstantInt *V) {
144 // Out[] does not distinguish between zero and undef, and we already know
145 // that this memset does not overlap with any other initializer. Nothing to
146 // do for memset(0).
147 if (V->isZero())
148 return;
149 for (int64_t Offset = Start - Start % 8; Offset < End; Offset += 8) {
150 uint64_t Cst = 0x0101010101010101UL;
151 int LowBits = Offset < Start ? (Start - Offset) * 8 : 0;
152 if (LowBits)
153 Cst = (Cst >> LowBits) << LowBits;
154 int HighBits = End - Offset < 8 ? (8 - (End - Offset)) * 8 : 0;
155 if (HighBits)
156 Cst = (Cst << HighBits) >> HighBits;
157 ConstantInt *C =
158 ConstantInt::get(IRB.getInt64Ty(), Cst * V->getZExtValue());
159
160 Value *&CurrentV = Out[Offset];
161 if (!CurrentV) {
162 CurrentV = C;
163 } else {
164 CurrentV = IRB.CreateOr(CurrentV, C);
165 }
166 }
167 }
168
169 // Take a 64-bit slice of the value starting at the given offset (in bytes).
170 // Offset can be negative. Pad with zeroes on both sides when necessary.
171 Value *sliceValue(IRBuilder<> &IRB, Value *V, int64_t Offset) {
172 if (Offset > 0) {
173 V = IRB.CreateLShr(V, Offset * 8);
174 V = IRB.CreateZExtOrTrunc(V, IRB.getInt64Ty());
175 } else if (Offset < 0) {
176 V = IRB.CreateZExtOrTrunc(V, IRB.getInt64Ty());
177 V = IRB.CreateShl(V, -Offset * 8);
178 } else {
179 V = IRB.CreateZExtOrTrunc(V, IRB.getInt64Ty());
180 }
181 return V;
182 }
183
184 void applyStore(IRBuilder<> &IRB, int64_t Start, int64_t End,
185 Value *StoredValue) {
186 StoredValue = flatten(IRB, StoredValue);
187 for (int64_t Offset = Start - Start % 8; Offset < End; Offset += 8) {
188 Value *V = sliceValue(IRB, StoredValue, Offset - Start);
189 Value *&CurrentV = Out[Offset];
190 if (!CurrentV) {
191 CurrentV = V;
192 } else {
193 CurrentV = IRB.CreateOr(CurrentV, V);
194 }
195 }
196 }
197
198 void generate(IRBuilder<> &IRB) {
199 LLVM_DEBUG(dbgs() << "Combined initializer\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << "Combined initializer\n"
; } } while (false)
;
200 // No initializers => the entire allocation is undef.
201 if (Ranges.empty()) {
202 emitUndef(IRB, 0, Size);
203 return;
204 }
205
206 // Look through 8-byte initializer list 16 bytes at a time;
207 // If one of the two 8-byte halfs is non-zero non-undef, emit STGP.
208 // Otherwise, emit zeroes up to next available item.
209 uint64_t LastOffset = 0;
210 for (uint64_t Offset = 0; Offset < Size; Offset += 16) {
211 auto I1 = Out.find(Offset);
212 auto I2 = Out.find(Offset + 8);
213 if (I1 == Out.end() && I2 == Out.end())
214 continue;
215
216 if (Offset > LastOffset)
217 emitZeroes(IRB, LastOffset, Offset - LastOffset);
218
219 Value *Store1 = I1 == Out.end() ? Constant::getNullValue(IRB.getInt64Ty())
220 : I1->second;
221 Value *Store2 = I2 == Out.end() ? Constant::getNullValue(IRB.getInt64Ty())
222 : I2->second;
223 emitPair(IRB, Offset, Store1, Store2);
224 LastOffset = Offset + 16;
225 }
226
227 // memset(0) does not update Out[], therefore the tail can be either undef
228 // or zero.
229 if (LastOffset < Size)
230 emitZeroes(IRB, LastOffset, Size - LastOffset);
231
232 for (const auto &R : Ranges) {
233 R.Inst->eraseFromParent();
234 }
235 }
236
237 void emitZeroes(IRBuilder<> &IRB, uint64_t Offset, uint64_t Size) {
238 LLVM_DEBUG(dbgs() << " [" << Offset << ", " << Offset + Sizedo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << " [" << Offset
<< ", " << Offset + Size << ") zero\n"; } }
while (false)
239 << ") zero\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << " [" << Offset
<< ", " << Offset + Size << ") zero\n"; } }
while (false)
;
240 Value *Ptr = BasePtr;
241 if (Offset)
242 Ptr = IRB.CreateConstGEP1_32(IRB.getInt8Ty(), Ptr, Offset);
243 IRB.CreateCall(SetTagZeroFn,
244 {Ptr, ConstantInt::get(IRB.getInt64Ty(), Size)});
245 }
246
247 void emitUndef(IRBuilder<> &IRB, uint64_t Offset, uint64_t Size) {
248 LLVM_DEBUG(dbgs() << " [" << Offset << ", " << Offset + Sizedo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << " [" << Offset
<< ", " << Offset + Size << ") undef\n"; }
} while (false)
249 << ") undef\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << " [" << Offset
<< ", " << Offset + Size << ") undef\n"; }
} while (false)
;
250 Value *Ptr = BasePtr;
251 if (Offset)
252 Ptr = IRB.CreateConstGEP1_32(IRB.getInt8Ty(), Ptr, Offset);
253 IRB.CreateCall(SetTagFn, {Ptr, ConstantInt::get(IRB.getInt64Ty(), Size)});
254 }
255
256 void emitPair(IRBuilder<> &IRB, uint64_t Offset, Value *A, Value *B) {
257 LLVM_DEBUG(dbgs() << " [" << Offset << ", " << Offset + 16 << "):\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << " [" << Offset
<< ", " << Offset + 16 << "):\n"; } } while
(false)
;
258 LLVM_DEBUG(dbgs() << " " << *A << "\n " << *B << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << " " << *
A << "\n " << *B << "\n"; } } while (false
)
;
259 Value *Ptr = BasePtr;
260 if (Offset)
261 Ptr = IRB.CreateConstGEP1_32(IRB.getInt8Ty(), Ptr, Offset);
262 IRB.CreateCall(StgpFn, {Ptr, A, B});
263 }
264
265 Value *flatten(IRBuilder<> &IRB, Value *V) {
266 if (V->getType()->isIntegerTy())
267 return V;
268 // vector of pointers -> vector of ints
269 if (VectorType *VecTy = dyn_cast<VectorType>(V->getType())) {
270 LLVMContext &Ctx = IRB.getContext();
271 Type *EltTy = VecTy->getElementType();
272 if (EltTy->isPointerTy()) {
273 uint32_t EltSize = DL->getTypeSizeInBits(EltTy);
274 auto *NewTy = FixedVectorType::get(
275 IntegerType::get(Ctx, EltSize),
276 cast<FixedVectorType>(VecTy)->getNumElements());
277 V = IRB.CreatePointerCast(V, NewTy);
278 }
279 }
280 return IRB.CreateBitOrPointerCast(
281 V, IRB.getIntNTy(DL->getTypeStoreSize(V->getType()) * 8));
282 }
283};
284
285class AArch64StackTagging : public FunctionPass {
286 struct AllocaInfo {
287 AllocaInst *AI;
288 TrackingVH<Instruction> OldAI; // Track through RAUW to replace debug uses.
289 SmallVector<IntrinsicInst *, 2> LifetimeStart;
290 SmallVector<IntrinsicInst *, 2> LifetimeEnd;
291 SmallVector<DbgVariableIntrinsic *, 2> DbgVariableIntrinsics;
292 int Tag; // -1 for non-tagged allocations
293 };
294
295 const bool MergeInit;
296 const bool UseStackSafety;
297
298public:
299 static char ID; // Pass ID, replacement for typeid
300
301 AArch64StackTagging(bool IsOptNone = false)
302 : FunctionPass(ID),
303 MergeInit(ClMergeInit.getNumOccurrences() ? ClMergeInit : !IsOptNone),
304 UseStackSafety(ClUseStackSafety.getNumOccurrences() ? ClUseStackSafety
305 : !IsOptNone) {
306 initializeAArch64StackTaggingPass(*PassRegistry::getPassRegistry());
307 }
308
309 bool isInterestingAlloca(const AllocaInst &AI);
310 void alignAndPadAlloca(AllocaInfo &Info);
311
312 void tagAlloca(AllocaInst *AI, Instruction *InsertBefore, Value *Ptr,
313 uint64_t Size);
314 void untagAlloca(AllocaInst *AI, Instruction *InsertBefore, uint64_t Size);
315
316 Instruction *collectInitializers(Instruction *StartInst, Value *StartPtr,
317 uint64_t Size, InitializerBuilder &IB);
318
319 Instruction *
320 insertBaseTaggedPointer(const MapVector<AllocaInst *, AllocaInfo> &Allocas,
321 const DominatorTree *DT);
322 bool runOnFunction(Function &F) override;
323
324 StringRef getPassName() const override { return "AArch64 Stack Tagging"; }
325
326private:
327 Function *F = nullptr;
328 Function *SetTagFunc = nullptr;
329 const DataLayout *DL = nullptr;
330 AAResults *AA = nullptr;
331 const StackSafetyGlobalInfo *SSI = nullptr;
332
333 void getAnalysisUsage(AnalysisUsage &AU) const override {
334 AU.setPreservesCFG();
335 if (UseStackSafety)
336 AU.addRequired<StackSafetyGlobalInfoWrapperPass>();
337 if (MergeInit)
338 AU.addRequired<AAResultsWrapperPass>();
339 }
340};
341
342} // end anonymous namespace
343
344char AArch64StackTagging::ID = 0;
345
346INITIALIZE_PASS_BEGIN(AArch64StackTagging, DEBUG_TYPE, "AArch64 Stack Tagging",static void *initializeAArch64StackTaggingPassOnce(PassRegistry
&Registry) {
347 false, false)static void *initializeAArch64StackTaggingPassOnce(PassRegistry
&Registry) {
348INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)initializeAAResultsWrapperPassPass(Registry);
349INITIALIZE_PASS_DEPENDENCY(StackSafetyGlobalInfoWrapperPass)initializeStackSafetyGlobalInfoWrapperPassPass(Registry);
350INITIALIZE_PASS_END(AArch64StackTagging, DEBUG_TYPE, "AArch64 Stack Tagging",PassInfo *PI = new PassInfo( "AArch64 Stack Tagging", "aarch64-stack-tagging"
, &AArch64StackTagging::ID, PassInfo::NormalCtor_t(callDefaultCtor
<AArch64StackTagging>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeAArch64StackTaggingPassFlag
; void llvm::initializeAArch64StackTaggingPass(PassRegistry &
Registry) { llvm::call_once(InitializeAArch64StackTaggingPassFlag
, initializeAArch64StackTaggingPassOnce, std::ref(Registry));
}
351 false, false)PassInfo *PI = new PassInfo( "AArch64 Stack Tagging", "aarch64-stack-tagging"
, &AArch64StackTagging::ID, PassInfo::NormalCtor_t(callDefaultCtor
<AArch64StackTagging>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeAArch64StackTaggingPassFlag
; void llvm::initializeAArch64StackTaggingPass(PassRegistry &
Registry) { llvm::call_once(InitializeAArch64StackTaggingPassFlag
, initializeAArch64StackTaggingPassOnce, std::ref(Registry));
}
352
353FunctionPass *llvm::createAArch64StackTaggingPass(bool IsOptNone) {
354 return new AArch64StackTagging(IsOptNone);
355}
356
357Instruction *AArch64StackTagging::collectInitializers(Instruction *StartInst,
358 Value *StartPtr,
359 uint64_t Size,
360 InitializerBuilder &IB) {
361 MemoryLocation AllocaLoc{StartPtr, Size};
362 Instruction *LastInst = StartInst;
363 BasicBlock::iterator BI(StartInst);
364
365 unsigned Count = 0;
366 for (; Count < ClScanLimit && !BI->isTerminator(); ++BI) {
367 if (!isa<DbgInfoIntrinsic>(*BI))
368 ++Count;
369
370 if (isNoModRef(AA->getModRefInfo(&*BI, AllocaLoc)))
371 continue;
372
373 if (!isa<StoreInst>(BI) && !isa<MemSetInst>(BI)) {
374 // If the instruction is readnone, ignore it, otherwise bail out. We
375 // don't even allow readonly here because we don't want something like:
376 // A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
377 if (BI->mayWriteToMemory() || BI->mayReadFromMemory())
378 break;
379 continue;
380 }
381
382 if (StoreInst *NextStore = dyn_cast<StoreInst>(BI)) {
383 if (!NextStore->isSimple())
384 break;
385
386 // Check to see if this store is to a constant offset from the start ptr.
387 Optional<int64_t> Offset =
388 isPointerOffset(StartPtr, NextStore->getPointerOperand(), *DL);
389 if (!Offset)
390 break;
391
392 if (!IB.addStore(*Offset, NextStore, DL))
393 break;
394 LastInst = NextStore;
395 } else {
396 MemSetInst *MSI = cast<MemSetInst>(BI);
397
398 if (MSI->isVolatile() || !isa<ConstantInt>(MSI->getLength()))
399 break;
400
401 if (!isa<ConstantInt>(MSI->getValue()))
402 break;
403
404 // Check to see if this store is to a constant offset from the start ptr.
405 Optional<int64_t> Offset = isPointerOffset(StartPtr, MSI->getDest(), *DL);
406 if (!Offset)
407 break;
408
409 if (!IB.addMemSet(*Offset, MSI))
410 break;
411 LastInst = MSI;
412 }
413 }
414 return LastInst;
415}
416
417bool AArch64StackTagging::isInterestingAlloca(const AllocaInst &AI) {
418 // FIXME: support dynamic allocas
419 bool IsInteresting =
420 AI.getAllocatedType()->isSized() && AI.isStaticAlloca() &&
421 // alloca() may be called with 0 size, ignore it.
422 AI.getAllocationSizeInBits(*DL).getValue() > 0 &&
423 // inalloca allocas are not treated as static, and we don't want
424 // dynamic alloca instrumentation for them as well.
425 !AI.isUsedWithInAlloca() &&
426 // swifterror allocas are register promoted by ISel
427 !AI.isSwiftError() &&
428 // safe allocas are not interesting
429 !(SSI && SSI->isSafe(AI));
430 return IsInteresting;
431}
432
433void AArch64StackTagging::tagAlloca(AllocaInst *AI, Instruction *InsertBefore,
434 Value *Ptr, uint64_t Size) {
435 auto SetTagZeroFunc =
436 Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_settag_zero);
437 auto StgpFunc =
438 Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_stgp);
439
440 InitializerBuilder IB(Size, DL, Ptr, SetTagFunc, SetTagZeroFunc, StgpFunc);
441 bool LittleEndian =
442 Triple(AI->getModule()->getTargetTriple()).isLittleEndian();
443 // Current implementation of initializer merging assumes little endianness.
444 if (MergeInit && !F->hasOptNone() && LittleEndian &&
445 Size < ClMergeInitSizeLimit) {
446 LLVM_DEBUG(dbgs() << "collecting initializers for " << *AIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << "collecting initializers for "
<< *AI << ", size = " << Size << "\n"
; } } while (false)
447 << ", size = " << Size << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("aarch64-stack-tagging")) { dbgs() << "collecting initializers for "
<< *AI << ", size = " << Size << "\n"
; } } while (false)
;
448 InsertBefore = collectInitializers(InsertBefore, Ptr, Size, IB);
449 }
450
451 IRBuilder<> IRB(InsertBefore);
452 IB.generate(IRB);
453}
454
455void AArch64StackTagging::untagAlloca(AllocaInst *AI, Instruction *InsertBefore,
456 uint64_t Size) {
457 IRBuilder<> IRB(InsertBefore);
458 IRB.CreateCall(SetTagFunc, {IRB.CreatePointerCast(AI, IRB.getInt8PtrTy()),
459 ConstantInt::get(IRB.getInt64Ty(), Size)});
460}
461
462Instruction *AArch64StackTagging::insertBaseTaggedPointer(
463 const MapVector<AllocaInst *, AllocaInfo> &Allocas,
464 const DominatorTree *DT) {
465 BasicBlock *PrologueBB = nullptr;
466 // Try sinking IRG as deep as possible to avoid hurting shrink wrap.
467 for (auto &I : Allocas) {
468 const AllocaInfo &Info = I.second;
469 AllocaInst *AI = Info.AI;
470 if (Info.Tag < 0)
28
Assuming field 'Tag' is >= 0
29
Taking false branch
32
Assuming field 'Tag' is >= 0
33
Taking false branch
471 continue;
472 if (!PrologueBB
29.1
'PrologueBB' is null
) {
30
Taking true branch
34
Assuming 'PrologueBB' is non-null
35
Taking false branch
473 PrologueBB = AI->getParent();
474 continue;
31
Execution continues on line 467
475 }
476 PrologueBB = DT->findNearestCommonDominator(PrologueBB, AI->getParent());
36
Called C++ object pointer is null
477 }
478 assert(PrologueBB)(static_cast <bool> (PrologueBB) ? void (0) : __assert_fail
("PrologueBB", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Target/AArch64/AArch64StackTagging.cpp"
, 478, __extension__ __PRETTY_FUNCTION__))
;
479
480 IRBuilder<> IRB(&PrologueBB->front());
481 Function *IRG_SP =
482 Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_irg_sp);
483 Instruction *Base =
484 IRB.CreateCall(IRG_SP, {Constant::getNullValue(IRB.getInt64Ty())});
485 Base->setName("basetag");
486 return Base;
487}
488
489void AArch64StackTagging::alignAndPadAlloca(AllocaInfo &Info) {
490 const Align NewAlignment =
491 max(MaybeAlign(Info.AI->getAlignment()), kTagGranuleSize);
492 Info.AI->setAlignment(NewAlignment);
493
494 uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
495 uint64_t AlignedSize = alignTo(Size, kTagGranuleSize);
496 if (Size == AlignedSize)
497 return;
498
499 // Add padding to the alloca.
500 Type *AllocatedType =
501 Info.AI->isArrayAllocation()
502 ? ArrayType::get(
503 Info.AI->getAllocatedType(),
504 cast<ConstantInt>(Info.AI->getArraySize())->getZExtValue())
505 : Info.AI->getAllocatedType();
506 Type *PaddingType =
507 ArrayType::get(Type::getInt8Ty(F->getContext()), AlignedSize - Size);
508 Type *TypeWithPadding = StructType::get(AllocatedType, PaddingType);
509 auto *NewAI = new AllocaInst(
510 TypeWithPadding, Info.AI->getType()->getAddressSpace(), nullptr, "", Info.AI);
511 NewAI->takeName(Info.AI);
512 NewAI->setAlignment(Info.AI->getAlign());
513 NewAI->setUsedWithInAlloca(Info.AI->isUsedWithInAlloca());
514 NewAI->setSwiftError(Info.AI->isSwiftError());
515 NewAI->copyMetadata(*Info.AI);
516
517 auto *NewPtr = new BitCastInst(NewAI, Info.AI->getType(), "", Info.AI);
518 Info.AI->replaceAllUsesWith(NewPtr);
519 Info.AI->eraseFromParent();
520 Info.AI = NewAI;
521}
522
523// FIXME: check for MTE extension
524bool AArch64StackTagging::runOnFunction(Function &Fn) {
525 if (!Fn.hasFnAttribute(Attribute::SanitizeMemTag))
1
Assuming the condition is false
2
Taking false branch
526 return false;
527
528 if (UseStackSafety)
3
Assuming field 'UseStackSafety' is false
4
Taking false branch
529 SSI = &getAnalysis<StackSafetyGlobalInfoWrapperPass>().getResult();
530 F = &Fn;
531 DL = &Fn.getParent()->getDataLayout();
532 if (MergeInit)
5
Assuming field 'MergeInit' is false
6
Taking false branch
533 AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
534
535 MapVector<AllocaInst *, AllocaInfo> Allocas; // need stable iteration order
536 SmallVector<Instruction *, 8> RetVec;
537 SmallVector<Instruction *, 4> UnrecognizedLifetimes;
538
539 for (auto &BB : *F) {
540 for (BasicBlock::iterator IT = BB.begin(); IT != BB.end(); ++IT) {
541 Instruction *I = &*IT;
542 if (auto *AI = dyn_cast<AllocaInst>(I)) {
543 Allocas[AI].AI = AI;
544 Allocas[AI].OldAI = AI;
545 continue;
546 }
547
548 if (auto *DVI = dyn_cast<DbgVariableIntrinsic>(I)) {
549 for (Value *V : DVI->location_ops())
550 if (auto *AI = dyn_cast_or_null<AllocaInst>(V))
551 if (Allocas[AI].DbgVariableIntrinsics.empty() ||
552 Allocas[AI].DbgVariableIntrinsics.back() != DVI)
553 Allocas[AI].DbgVariableIntrinsics.push_back(DVI);
554 continue;
555 }
556
557 auto *II = dyn_cast<IntrinsicInst>(I);
558 if (II && (II->getIntrinsicID() == Intrinsic::lifetime_start ||
559 II->getIntrinsicID() == Intrinsic::lifetime_end)) {
560 AllocaInst *AI = findAllocaForValue(II->getArgOperand(1));
561 if (!AI) {
562 UnrecognizedLifetimes.push_back(I);
563 continue;
564 }
565 if (II->getIntrinsicID() == Intrinsic::lifetime_start)
566 Allocas[AI].LifetimeStart.push_back(II);
567 else
568 Allocas[AI].LifetimeEnd.push_back(II);
569 }
570
571 if (isa<ReturnInst>(I) || isa<ResumeInst>(I) || isa<CleanupReturnInst>(I))
572 RetVec.push_back(I);
573 }
574 }
575
576 if (Allocas.empty())
7
Assuming the condition is false
8
Taking false branch
577 return false;
578
579 int NextTag = 0;
580 int NumInterestingAllocas = 0;
581 for (auto &I : Allocas) {
582 AllocaInfo &Info = I.second;
583 assert(Info.AI)(static_cast <bool> (Info.AI) ? void (0) : __assert_fail
("Info.AI", "/build/llvm-toolchain-snapshot-14~++20210926122410+d23fd8ae8906/llvm/lib/Target/AArch64/AArch64StackTagging.cpp"
, 583, __extension__ __PRETTY_FUNCTION__))
;
9
Assuming field 'AI' is non-null
10
'?' condition is true
13
Assuming field 'AI' is non-null
14
'?' condition is true
17
Assuming field 'AI' is non-null
18
'?' condition is true
584
585 if (!isInterestingAlloca(*Info.AI)) {
11
Taking true branch
15
Taking true branch
19
Taking false branch
586 Info.Tag = -1;
587 continue;
12
Execution continues on line 581
16
Execution continues on line 581
588 }
589
590 alignAndPadAlloca(Info);
591 NumInterestingAllocas++;
592 Info.Tag = NextTag;
593 NextTag = (NextTag + 1) % 16;
594 }
595
596 if (NumInterestingAllocas
19.1
'NumInterestingAllocas' is not equal to 0
== 0)
20
Taking false branch
597 return true;
598
599 std::unique_ptr<DominatorTree> DeleteDT;
600 DominatorTree *DT = nullptr;
21
'DT' initialized to a null pointer value
601 if (auto *P
21.1
'P' is null
= getAnalysisIfAvailable<DominatorTreeWrapperPass>())
602 DT = &P->getDomTree();
603
604 if (DT == nullptr && (NumInterestingAllocas
21.2
'NumInterestingAllocas' is <= 1
> 1 ||
23
Taking false branch
605 !F->hasFnAttribute(Attribute::OptimizeNone))) {
22
Assuming the condition is false
606 DeleteDT = std::make_unique<DominatorTree>(*F);
607 DT = DeleteDT.get();
608 }
609
610 std::unique_ptr<PostDominatorTree> DeletePDT;
611 PostDominatorTree *PDT = nullptr;
612 if (auto *P
23.1
'P' is null
= getAnalysisIfAvailable<PostDominatorTreeWrapperPass>())
613 PDT = &P->getPostDomTree();
614
615 if (PDT == nullptr && !F->hasFnAttribute(Attribute::OptimizeNone)) {
24
Assuming the condition is false
25
Taking false branch
616 DeletePDT = std::make_unique<PostDominatorTree>(*F);
617 PDT = DeletePDT.get();
618 }
619
620 SetTagFunc =
621 Intrinsic::getDeclaration(F->getParent(), Intrinsic::aarch64_settag);
622
623 Instruction *Base = insertBaseTaggedPointer(Allocas, DT);
26
Passing null pointer value via 2nd parameter 'DT'
27
Calling 'AArch64StackTagging::insertBaseTaggedPointer'
624
625 for (auto &I : Allocas) {
626 const AllocaInfo &Info = I.second;
627 AllocaInst *AI = Info.AI;
628 if (Info.Tag < 0)
629 continue;
630
631 // Replace alloca with tagp(alloca).
632 IRBuilder<> IRB(Info.AI->getNextNode());
633 Function *TagP = Intrinsic::getDeclaration(
634 F->getParent(), Intrinsic::aarch64_tagp, {Info.AI->getType()});
635 Instruction *TagPCall =
636 IRB.CreateCall(TagP, {Constant::getNullValue(Info.AI->getType()), Base,
637 ConstantInt::get(IRB.getInt64Ty(), Info.Tag)});
638 if (Info.AI->hasName())
639 TagPCall->setName(Info.AI->getName() + ".tag");
640 Info.AI->replaceAllUsesWith(TagPCall);
641 TagPCall->setOperand(0, Info.AI);
642
643 if (UnrecognizedLifetimes.empty() && Info.LifetimeStart.size() == 1 &&
644 Info.LifetimeEnd.size() == 1) {
645 IntrinsicInst *Start = Info.LifetimeStart[0];
646 IntrinsicInst *End = Info.LifetimeEnd[0];
647 uint64_t Size =
648 cast<ConstantInt>(Start->getArgOperand(0))->getZExtValue();
649 Size = alignTo(Size, kTagGranuleSize);
650 tagAlloca(AI, Start->getNextNode(), Start->getArgOperand(1), Size);
651
652 auto TagEnd = [&](Instruction *Node) { untagAlloca(AI, Node, Size); };
653 if (!DT || !PDT ||
654 !forAllReachableExits(*DT, *PDT, Start, Info.LifetimeEnd, RetVec,
655 TagEnd))
656 End->eraseFromParent();
657 } else {
658 uint64_t Size = Info.AI->getAllocationSizeInBits(*DL).getValue() / 8;
659 Value *Ptr = IRB.CreatePointerCast(TagPCall, IRB.getInt8PtrTy());
660 tagAlloca(AI, &*IRB.GetInsertPoint(), Ptr, Size);
661 for (auto &RI : RetVec) {
662 untagAlloca(AI, RI, Size);
663 }
664 // We may have inserted tag/untag outside of any lifetime interval.
665 // Remove all lifetime intrinsics for this alloca.
666 for (auto &II : Info.LifetimeStart)
667 II->eraseFromParent();
668 for (auto &II : Info.LifetimeEnd)
669 II->eraseFromParent();
670 }
671
672 // Fixup debug intrinsics to point to the new alloca.
673 for (auto DVI : Info.DbgVariableIntrinsics)
674 DVI->replaceVariableLocationOp(Info.OldAI, Info.AI);
675 }
676
677 // If we have instrumented at least one alloca, all unrecognized lifetime
678 // instrinsics have to go.
679 for (auto &I : UnrecognizedLifetimes)
680 I->eraseFromParent();
681
682 return true;
683}