DataFlowSanitizer.cpp revision fdb1a6c341c0e289f3f900cdab87f831262c0e93 
1//===-- DataFlowSanitizer.cpp - dynamic data flow analysis ----------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9/// \file
10/// This file is a part of DataFlowSanitizer, a generalised dynamic data flow
11/// analysis.
12///
13/// Unlike other Sanitizer tools, this tool is not designed to detect a specific
14/// class of bugs on its own.  Instead, it provides a generic dynamic data flow
15/// analysis framework to be used by clients to help detect application-specific
16/// issues within their own code.
17///
18/// The analysis is based on automatic propagation of data flow labels (also
19/// known as taint labels) through a program as it performs computation.  Each
20/// byte of application memory is backed by two bytes of shadow memory which
21/// hold the label.  On Linux/x86_64, memory is laid out as follows:
22///
23/// +--------------------+ 0x800000000000 (top of memory)
24/// | application memory |
25/// +--------------------+ 0x700000008000 (kAppAddr)
26/// |                    |
27/// |       unused       |
28/// |                    |
29/// +--------------------+ 0x200200000000 (kUnusedAddr)
30/// |    union table     |
31/// +--------------------+ 0x200000000000 (kUnionTableAddr)
32/// |   shadow memory    |
33/// +--------------------+ 0x000000010000 (kShadowAddr)
34/// | reserved by kernel |
35/// +--------------------+ 0x000000000000
36///
37/// To derive a shadow memory address from an application memory address,
38/// bits 44-46 are cleared to bring the address into the range
39/// [0x000000008000,0x100000000000).  Then the address is shifted left by 1 to
40/// account for the double byte representation of shadow labels and move the
41/// address into the shadow memory range.  See the function
42/// DataFlowSanitizer::getShadowAddress below.
43///
44/// For more information, please refer to the design document:
45/// http://clang.llvm.org/docs/DataFlowSanitizerDesign.html
46
47#include "llvm/Transforms/Instrumentation.h"
48#include "llvm/ADT/DenseMap.h"
49#include "llvm/ADT/DenseSet.h"
50#include "llvm/ADT/DepthFirstIterator.h"
51#include "llvm/Analysis/ValueTracking.h"
52#include "llvm/IR/InlineAsm.h"
53#include "llvm/IR/IRBuilder.h"
54#include "llvm/IR/LLVMContext.h"
55#include "llvm/IR/MDBuilder.h"
56#include "llvm/IR/Type.h"
57#include "llvm/IR/Value.h"
58#include "llvm/InstVisitor.h"
59#include "llvm/Pass.h"
60#include "llvm/Support/CommandLine.h"
61#include "llvm/Transforms/Utils/BasicBlockUtils.h"
62#include "llvm/Transforms/Utils/Local.h"
63#include "llvm/Transforms/Utils/SpecialCaseList.h"
64#include <iterator>
65
66using namespace llvm;
67
68// The -dfsan-preserve-alignment flag controls whether this pass assumes that
69// alignment requirements provided by the input IR are correct.  For example,
70// if the input IR contains a load with alignment 8, this flag will cause
71// the shadow load to have alignment 16.  This flag is disabled by default as
72// we have unfortunately encountered too much code (including Clang itself;
73// see PR14291) which performs misaligned access.
74static cl::opt<bool> ClPreserveAlignment(
75    "dfsan-preserve-alignment",
76    cl::desc("respect alignment requirements provided by input IR"), cl::Hidden,
77    cl::init(false));
78
79// The ABI list file controls how shadow parameters are passed.  The pass treats
80// every function labelled "uninstrumented" in the ABI list file as conforming
81// to the "native" (i.e. unsanitized) ABI.  Unless the ABI list contains
82// additional annotations for those functions, a call to one of those functions
83// will produce a warning message, as the labelling behaviour of the function is
84// unknown.  The other supported annotations are "functional" and "discard",
85// which are described below under DataFlowSanitizer::WrapperKind.
86static cl::opt<std::string> ClABIListFile(
87    "dfsan-abilist",
88    cl::desc("File listing native ABI functions and how the pass treats them"),
89    cl::Hidden);
90
91// Controls whether the pass uses IA_Args or IA_TLS as the ABI for instrumented
92// functions (see DataFlowSanitizer::InstrumentedABI below).
93static cl::opt<bool> ClArgsABI(
94    "dfsan-args-abi",
95    cl::desc("Use the argument ABI rather than the TLS ABI"),
96    cl::Hidden);
97
98namespace {
99
100class DataFlowSanitizer : public ModulePass {
101  friend struct DFSanFunction;
102  friend class DFSanVisitor;
103
104  enum {
105    ShadowWidth = 16
106  };
107
108  /// Which ABI should be used for instrumented functions?
109  enum InstrumentedABI {
110    /// Argument and return value labels are passed through additional
111    /// arguments and by modifying the return type.
112    IA_Args,
113
114    /// Argument and return value labels are passed through TLS variables
115    /// __dfsan_arg_tls and __dfsan_retval_tls.
116    IA_TLS
117  };
118
119  /// How should calls to uninstrumented functions be handled?
120  enum WrapperKind {
121    /// This function is present in an uninstrumented form but we don't know
122    /// how it should be handled.  Print a warning and call the function anyway.
123    /// Don't label the return value.
124    WK_Warning,
125
126    /// This function does not write to (user-accessible) memory, and its return
127    /// value is unlabelled.
128    WK_Discard,
129
130    /// This function does not write to (user-accessible) memory, and the label
131    /// of its return value is the union of the label of its arguments.
132    WK_Functional,
133
134    /// Instead of calling the function, a custom wrapper __dfsw_F is called,
135    /// where F is the name of the function.  This function may wrap the
136    /// original function or provide its own implementation.  This is similar to
137    /// the IA_Args ABI, except that IA_Args uses a struct return type to
138    /// pass the return value shadow in a register, while WK_Custom uses an
139    /// extra pointer argument to return the shadow.  This allows the wrapped
140    /// form of the function type to be expressed in C.
141    WK_Custom
142  };
143
144  DataLayout *DL;
145  Module *Mod;
146  LLVMContext *Ctx;
147  IntegerType *ShadowTy;
148  PointerType *ShadowPtrTy;
149  IntegerType *IntptrTy;
150  ConstantInt *ZeroShadow;
151  ConstantInt *ShadowPtrMask;
152  ConstantInt *ShadowPtrMul;
153  Constant *ArgTLS;
154  Constant *RetvalTLS;
155  void *(*GetArgTLSPtr)();
156  void *(*GetRetvalTLSPtr)();
157  Constant *GetArgTLS;
158  Constant *GetRetvalTLS;
159  FunctionType *DFSanUnionFnTy;
160  FunctionType *DFSanUnionLoadFnTy;
161  FunctionType *DFSanUnimplementedFnTy;
162  Constant *DFSanUnionFn;
163  Constant *DFSanUnionLoadFn;
164  Constant *DFSanUnimplementedFn;
165  MDNode *ColdCallWeights;
166  OwningPtr<SpecialCaseList> ABIList;
167  DenseMap<Value *, Function *> UnwrappedFnMap;
168  AttributeSet ReadOnlyNoneAttrs;
169
170  Value *getShadowAddress(Value *Addr, Instruction *Pos);
171  Value *combineShadows(Value *V1, Value *V2, Instruction *Pos);
172  bool isInstrumented(Function *F);
173  FunctionType *getArgsFunctionType(FunctionType *T);
174  FunctionType *getCustomFunctionType(FunctionType *T);
175  InstrumentedABI getInstrumentedABI();
176  WrapperKind getWrapperKind(Function *F);
177
178 public:
179  DataFlowSanitizer(StringRef ABIListFile = StringRef(),
180                    void *(*getArgTLS)() = 0, void *(*getRetValTLS)() = 0);
181  static char ID;
182  bool doInitialization(Module &M);
183  bool runOnModule(Module &M);
184};
185
186struct DFSanFunction {
187  DataFlowSanitizer &DFS;
188  Function *F;
189  DataFlowSanitizer::InstrumentedABI IA;
190  bool IsNativeABI;
191  Value *ArgTLSPtr;
192  Value *RetvalTLSPtr;
193  AllocaInst *LabelReturnAlloca;
194  DenseMap<Value *, Value *> ValShadowMap;
195  DenseMap<AllocaInst *, AllocaInst *> AllocaShadowMap;
196  std::vector<std::pair<PHINode *, PHINode *> > PHIFixups;
197  DenseSet<Instruction *> SkipInsts;
198
199  DFSanFunction(DataFlowSanitizer &DFS, Function *F, bool IsNativeABI)
200      : DFS(DFS), F(F), IA(DFS.getInstrumentedABI()),
201        IsNativeABI(IsNativeABI), ArgTLSPtr(0), RetvalTLSPtr(0),
202        LabelReturnAlloca(0) {}
203  Value *getArgTLSPtr();
204  Value *getArgTLS(unsigned Index, Instruction *Pos);
205  Value *getRetvalTLS();
206  Value *getShadow(Value *V);
207  void setShadow(Instruction *I, Value *Shadow);
208  Value *combineOperandShadows(Instruction *Inst);
209  Value *loadShadow(Value *ShadowAddr, uint64_t Size, uint64_t Align,
210                    Instruction *Pos);
211  void storeShadow(Value *Addr, uint64_t Size, uint64_t Align, Value *Shadow,
212                   Instruction *Pos);
213};
214
215class DFSanVisitor : public InstVisitor<DFSanVisitor> {
216 public:
217  DFSanFunction &DFSF;
218  DFSanVisitor(DFSanFunction &DFSF) : DFSF(DFSF) {}
219
220  void visitOperandShadowInst(Instruction &I);
221
222  void visitBinaryOperator(BinaryOperator &BO);
223  void visitCastInst(CastInst &CI);
224  void visitCmpInst(CmpInst &CI);
225  void visitGetElementPtrInst(GetElementPtrInst &GEPI);
226  void visitLoadInst(LoadInst &LI);
227  void visitStoreInst(StoreInst &SI);
228  void visitReturnInst(ReturnInst &RI);
229  void visitCallSite(CallSite CS);
230  void visitPHINode(PHINode &PN);
231  void visitExtractElementInst(ExtractElementInst &I);
232  void visitInsertElementInst(InsertElementInst &I);
233  void visitShuffleVectorInst(ShuffleVectorInst &I);
234  void visitExtractValueInst(ExtractValueInst &I);
235  void visitInsertValueInst(InsertValueInst &I);
236  void visitAllocaInst(AllocaInst &I);
237  void visitSelectInst(SelectInst &I);
238  void visitMemTransferInst(MemTransferInst &I);
239};
240
241}
242
243char DataFlowSanitizer::ID;
244INITIALIZE_PASS(DataFlowSanitizer, "dfsan",
245                "DataFlowSanitizer: dynamic data flow analysis.", false, false)
246
247ModulePass *llvm::createDataFlowSanitizerPass(StringRef ABIListFile,
248                                              void *(*getArgTLS)(),
249                                              void *(*getRetValTLS)()) {
250  return new DataFlowSanitizer(ABIListFile, getArgTLS, getRetValTLS);
251}
252
253DataFlowSanitizer::DataFlowSanitizer(StringRef ABIListFile,
254                                     void *(*getArgTLS)(),
255                                     void *(*getRetValTLS)())
256    : ModulePass(ID), GetArgTLSPtr(getArgTLS), GetRetvalTLSPtr(getRetValTLS),
257      ABIList(SpecialCaseList::createOrDie(ABIListFile.empty() ? ClABIListFile
258                                                               : ABIListFile)) {
259}
260
261FunctionType *DataFlowSanitizer::getArgsFunctionType(FunctionType *T) {
262  llvm::SmallVector<Type *, 4> ArgTypes;
263  std::copy(T->param_begin(), T->param_end(), std::back_inserter(ArgTypes));
264  for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
265    ArgTypes.push_back(ShadowTy);
266  if (T->isVarArg())
267    ArgTypes.push_back(ShadowPtrTy);
268  Type *RetType = T->getReturnType();
269  if (!RetType->isVoidTy())
270    RetType = StructType::get(RetType, ShadowTy, (Type *)0);
271  return FunctionType::get(RetType, ArgTypes, T->isVarArg());
272}
273
274FunctionType *DataFlowSanitizer::getCustomFunctionType(FunctionType *T) {
275  assert(!T->isVarArg());
276  llvm::SmallVector<Type *, 4> ArgTypes;
277  std::copy(T->param_begin(), T->param_end(), std::back_inserter(ArgTypes));
278  for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
279    ArgTypes.push_back(ShadowTy);
280  Type *RetType = T->getReturnType();
281  if (!RetType->isVoidTy())
282    ArgTypes.push_back(ShadowPtrTy);
283  return FunctionType::get(T->getReturnType(), ArgTypes, false);
284}
285
286bool DataFlowSanitizer::doInitialization(Module &M) {
287  DL = getAnalysisIfAvailable<DataLayout>();
288  if (!DL)
289    return false;
290
291  Mod = &M;
292  Ctx = &M.getContext();
293  ShadowTy = IntegerType::get(*Ctx, ShadowWidth);
294  ShadowPtrTy = PointerType::getUnqual(ShadowTy);
295  IntptrTy = DL->getIntPtrType(*Ctx);
296  ZeroShadow = ConstantInt::getSigned(ShadowTy, 0);
297  ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0x700000000000LL);
298  ShadowPtrMul = ConstantInt::getSigned(IntptrTy, ShadowWidth / 8);
299
300  Type *DFSanUnionArgs[2] = { ShadowTy, ShadowTy };
301  DFSanUnionFnTy =
302      FunctionType::get(ShadowTy, DFSanUnionArgs, /*isVarArg=*/ false);
303  Type *DFSanUnionLoadArgs[2] = { ShadowPtrTy, IntptrTy };
304  DFSanUnionLoadFnTy =
305      FunctionType::get(ShadowTy, DFSanUnionLoadArgs, /*isVarArg=*/ false);
306  DFSanUnimplementedFnTy = FunctionType::get(
307      Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);
308
309  if (GetArgTLSPtr) {
310    Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
311    ArgTLS = 0;
312    GetArgTLS = ConstantExpr::getIntToPtr(
313        ConstantInt::get(IntptrTy, uintptr_t(GetArgTLSPtr)),
314        PointerType::getUnqual(
315            FunctionType::get(PointerType::getUnqual(ArgTLSTy), (Type *)0)));
316  }
317  if (GetRetvalTLSPtr) {
318    RetvalTLS = 0;
319    GetRetvalTLS = ConstantExpr::getIntToPtr(
320        ConstantInt::get(IntptrTy, uintptr_t(GetRetvalTLSPtr)),
321        PointerType::getUnqual(
322            FunctionType::get(PointerType::getUnqual(ShadowTy), (Type *)0)));
323  }
324
325  ColdCallWeights = MDBuilder(*Ctx).createBranchWeights(1, 1000);
326  return true;
327}
328
329bool DataFlowSanitizer::isInstrumented(Function *F) {
330  return !ABIList->isIn(*F, "uninstrumented");
331}
332
333DataFlowSanitizer::InstrumentedABI DataFlowSanitizer::getInstrumentedABI() {
334  return ClArgsABI ? IA_Args : IA_TLS;
335}
336
337DataFlowSanitizer::WrapperKind DataFlowSanitizer::getWrapperKind(Function *F) {
338  if (ABIList->isIn(*F, "functional"))
339    return WK_Functional;
340  if (ABIList->isIn(*F, "discard"))
341    return WK_Discard;
342  if (ABIList->isIn(*F, "custom"))
343    return WK_Custom;
344
345  return WK_Warning;
346}
347
348bool DataFlowSanitizer::runOnModule(Module &M) {
349  if (!DL)
350    return false;
351
352  if (ABIList->isIn(M, "skip"))
353    return false;
354
355  if (!GetArgTLSPtr) {
356    Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
357    ArgTLS = Mod->getOrInsertGlobal("__dfsan_arg_tls", ArgTLSTy);
358    if (GlobalVariable *G = dyn_cast<GlobalVariable>(ArgTLS))
359      G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
360  }
361  if (!GetRetvalTLSPtr) {
362    RetvalTLS = Mod->getOrInsertGlobal("__dfsan_retval_tls", ShadowTy);
363    if (GlobalVariable *G = dyn_cast<GlobalVariable>(RetvalTLS))
364      G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
365  }
366
367  DFSanUnionFn = Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy);
368  if (Function *F = dyn_cast<Function>(DFSanUnionFn)) {
369    F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
370    F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
371    F->addAttribute(1, Attribute::ZExt);
372    F->addAttribute(2, Attribute::ZExt);
373  }
374  DFSanUnionLoadFn =
375      Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy);
376  if (Function *F = dyn_cast<Function>(DFSanUnionLoadFn)) {
377    F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
378  }
379  DFSanUnimplementedFn =
380      Mod->getOrInsertFunction("__dfsan_unimplemented", DFSanUnimplementedFnTy);
381
382  std::vector<Function *> FnsToInstrument;
383  llvm::SmallPtrSet<Function *, 2> FnsWithNativeABI;
384  for (Module::iterator i = M.begin(), e = M.end(); i != e; ++i) {
385    if (!i->isIntrinsic() &&
386        i != DFSanUnionFn &&
387        i != DFSanUnionLoadFn &&
388        i != DFSanUnimplementedFn)
389      FnsToInstrument.push_back(&*i);
390  }
391
392  AttrBuilder B;
393  B.addAttribute(Attribute::ReadOnly).addAttribute(Attribute::ReadNone);
394  ReadOnlyNoneAttrs = AttributeSet::get(*Ctx, AttributeSet::FunctionIndex, B);
395
396  // First, change the ABI of every function in the module.  ABI-listed
397  // functions keep their original ABI and get a wrapper function.
398  for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
399                                         e = FnsToInstrument.end();
400       i != e; ++i) {
401    Function &F = **i;
402    FunctionType *FT = F.getFunctionType();
403
404    if (FT->getNumParams() == 0 && !FT->isVarArg() &&
405        FT->getReturnType()->isVoidTy())
406      continue;
407
408    if (isInstrumented(&F)) {
409      if (getInstrumentedABI() == IA_Args) {
410        FunctionType *NewFT = getArgsFunctionType(FT);
411        Function *NewF = Function::Create(NewFT, F.getLinkage(), "", &M);
412        NewF->copyAttributesFrom(&F);
413        NewF->removeAttributes(
414            AttributeSet::ReturnIndex,
415            AttributeFuncs::typeIncompatible(NewFT->getReturnType(),
416                                             AttributeSet::ReturnIndex));
417        for (Function::arg_iterator FArg = F.arg_begin(),
418                                    NewFArg = NewF->arg_begin(),
419                                    FArgEnd = F.arg_end();
420             FArg != FArgEnd; ++FArg, ++NewFArg) {
421          FArg->replaceAllUsesWith(NewFArg);
422        }
423        NewF->getBasicBlockList().splice(NewF->begin(), F.getBasicBlockList());
424
425        for (Function::use_iterator ui = F.use_begin(), ue = F.use_end();
426             ui != ue;) {
427          BlockAddress *BA = dyn_cast<BlockAddress>(ui.getUse().getUser());
428          ++ui;
429          if (BA) {
430            BA->replaceAllUsesWith(
431                BlockAddress::get(NewF, BA->getBasicBlock()));
432            delete BA;
433          }
434        }
435        F.replaceAllUsesWith(
436            ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT)));
437        NewF->takeName(&F);
438        F.eraseFromParent();
439        *i = NewF;
440      }
441               // Hopefully, nobody will try to indirectly call a vararg
442               // function... yet.
443    } else if (FT->isVarArg()) {
444      UnwrappedFnMap[&F] = &F;
445      *i = 0;
446    } else {
447      // Build a wrapper function for F.  The wrapper simply calls F, and is
448      // added to FnsToInstrument so that any instrumentation according to its
449      // WrapperKind is done in the second pass below.
450      FunctionType *NewFT = getInstrumentedABI() == IA_Args
451                                ? getArgsFunctionType(FT)
452                                : FT;
453      Function *NewF =
454          Function::Create(NewFT, GlobalValue::LinkOnceODRLinkage,
455                           std::string("dfsw$") + F.getName(), &M);
456      NewF->copyAttributesFrom(&F);
457      NewF->removeAttributes(
458              AttributeSet::ReturnIndex,
459              AttributeFuncs::typeIncompatible(NewFT->getReturnType(),
460                                               AttributeSet::ReturnIndex));
461      if (getInstrumentedABI() == IA_TLS)
462        NewF->removeAttributes(AttributeSet::FunctionIndex,
463                               ReadOnlyNoneAttrs);
464
465      BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", NewF);
466      std::vector<Value *> Args;
467      unsigned n = FT->getNumParams();
468      for (Function::arg_iterator ai = NewF->arg_begin(); n != 0; ++ai, --n)
469        Args.push_back(&*ai);
470      CallInst *CI = CallInst::Create(&F, Args, "", BB);
471      if (FT->getReturnType()->isVoidTy())
472        ReturnInst::Create(*Ctx, BB);
473      else
474        ReturnInst::Create(*Ctx, CI, BB);
475
476      Value *WrappedFnCst =
477          ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT));
478      F.replaceAllUsesWith(WrappedFnCst);
479      UnwrappedFnMap[WrappedFnCst] = &F;
480      *i = NewF;
481
482      if (!F.isDeclaration()) {
483        // This function is probably defining an interposition of an
484        // uninstrumented function and hence needs to keep the original ABI.
485        // But any functions it may call need to use the instrumented ABI, so
486        // we instrument it in a mode which preserves the original ABI.
487        FnsWithNativeABI.insert(&F);
488
489        // This code needs to rebuild the iterators, as they may be invalidated
490        // by the push_back, taking care that the new range does not include
491        // any functions added by this code.
492        size_t N = i - FnsToInstrument.begin(),
493               Count = e - FnsToInstrument.begin();
494        FnsToInstrument.push_back(&F);
495        i = FnsToInstrument.begin() + N;
496        e = FnsToInstrument.begin() + Count;
497      }
498    }
499  }
500
501  for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
502                                         e = FnsToInstrument.end();
503       i != e; ++i) {
504    if (!*i || (*i)->isDeclaration())
505      continue;
506
507    removeUnreachableBlocks(**i);
508
509    DFSanFunction DFSF(*this, *i, FnsWithNativeABI.count(*i));
510
511    // DFSanVisitor may create new basic blocks, which confuses df_iterator.
512    // Build a copy of the list before iterating over it.
513    llvm::SmallVector<BasicBlock *, 4> BBList;
514    std::copy(df_begin(&(*i)->getEntryBlock()), df_end(&(*i)->getEntryBlock()),
515              std::back_inserter(BBList));
516
517    for (llvm::SmallVector<BasicBlock *, 4>::iterator i = BBList.begin(),
518                                                      e = BBList.end();
519         i != e; ++i) {
520      Instruction *Inst = &(*i)->front();
521      while (1) {
522        // DFSanVisitor may split the current basic block, changing the current
523        // instruction's next pointer and moving the next instruction to the
524        // tail block from which we should continue.
525        Instruction *Next = Inst->getNextNode();
526        // DFSanVisitor may delete Inst, so keep track of whether it was a
527        // terminator.
528        bool IsTerminator = isa<TerminatorInst>(Inst);
529        if (!DFSF.SkipInsts.count(Inst))
530          DFSanVisitor(DFSF).visit(Inst);
531        if (IsTerminator)
532          break;
533        Inst = Next;
534      }
535    }
536
537    // We will not necessarily be able to compute the shadow for every phi node
538    // until we have visited every block.  Therefore, the code that handles phi
539    // nodes adds them to the PHIFixups list so that they can be properly
540    // handled here.
541    for (std::vector<std::pair<PHINode *, PHINode *> >::iterator
542             i = DFSF.PHIFixups.begin(),
543             e = DFSF.PHIFixups.end();
544         i != e; ++i) {
545      for (unsigned val = 0, n = i->first->getNumIncomingValues(); val != n;
546           ++val) {
547        i->second->setIncomingValue(
548            val, DFSF.getShadow(i->first->getIncomingValue(val)));
549      }
550    }
551  }
552
553  return false;
554}
555
556Value *DFSanFunction::getArgTLSPtr() {
557  if (ArgTLSPtr)
558    return ArgTLSPtr;
559  if (DFS.ArgTLS)
560    return ArgTLSPtr = DFS.ArgTLS;
561
562  IRBuilder<> IRB(F->getEntryBlock().begin());
563  return ArgTLSPtr = IRB.CreateCall(DFS.GetArgTLS);
564}
565
566Value *DFSanFunction::getRetvalTLS() {
567  if (RetvalTLSPtr)
568    return RetvalTLSPtr;
569  if (DFS.RetvalTLS)
570    return RetvalTLSPtr = DFS.RetvalTLS;
571
572  IRBuilder<> IRB(F->getEntryBlock().begin());
573  return RetvalTLSPtr = IRB.CreateCall(DFS.GetRetvalTLS);
574}
575
576Value *DFSanFunction::getArgTLS(unsigned Idx, Instruction *Pos) {
577  IRBuilder<> IRB(Pos);
578  return IRB.CreateConstGEP2_64(getArgTLSPtr(), 0, Idx);
579}
580
581Value *DFSanFunction::getShadow(Value *V) {
582  if (!isa<Argument>(V) && !isa<Instruction>(V))
583    return DFS.ZeroShadow;
584  Value *&Shadow = ValShadowMap[V];
585  if (!Shadow) {
586    if (Argument *A = dyn_cast<Argument>(V)) {
587      if (IsNativeABI)
588        return DFS.ZeroShadow;
589      switch (IA) {
590      case DataFlowSanitizer::IA_TLS: {
591        Value *ArgTLSPtr = getArgTLSPtr();
592        Instruction *ArgTLSPos =
593            DFS.ArgTLS ? &*F->getEntryBlock().begin()
594                       : cast<Instruction>(ArgTLSPtr)->getNextNode();
595        IRBuilder<> IRB(ArgTLSPos);
596        Shadow = IRB.CreateLoad(getArgTLS(A->getArgNo(), ArgTLSPos));
597        break;
598      }
599      case DataFlowSanitizer::IA_Args: {
600        unsigned ArgIdx = A->getArgNo() + F->getArgumentList().size() / 2;
601        Function::arg_iterator i = F->arg_begin();
602        while (ArgIdx--)
603          ++i;
604        Shadow = i;
605        assert(Shadow->getType() == DFS.ShadowTy);
606        break;
607      }
608      }
609    } else {
610      Shadow = DFS.ZeroShadow;
611    }
612  }
613  return Shadow;
614}
615
616void DFSanFunction::setShadow(Instruction *I, Value *Shadow) {
617  assert(!ValShadowMap.count(I));
618  assert(Shadow->getType() == DFS.ShadowTy);
619  ValShadowMap[I] = Shadow;
620}
621
622Value *DataFlowSanitizer::getShadowAddress(Value *Addr, Instruction *Pos) {
623  assert(Addr != RetvalTLS && "Reinstrumenting?");
624  IRBuilder<> IRB(Pos);
625  return IRB.CreateIntToPtr(
626      IRB.CreateMul(
627          IRB.CreateAnd(IRB.CreatePtrToInt(Addr, IntptrTy), ShadowPtrMask),
628          ShadowPtrMul),
629      ShadowPtrTy);
630}
631
632// Generates IR to compute the union of the two given shadows, inserting it
633// before Pos.  Returns the computed union Value.
634Value *DataFlowSanitizer::combineShadows(Value *V1, Value *V2,
635                                         Instruction *Pos) {
636  if (V1 == ZeroShadow)
637    return V2;
638  if (V2 == ZeroShadow)
639    return V1;
640  if (V1 == V2)
641    return V1;
642  IRBuilder<> IRB(Pos);
643  BasicBlock *Head = Pos->getParent();
644  Value *Ne = IRB.CreateICmpNE(V1, V2);
645  Instruction *NeInst = dyn_cast<Instruction>(Ne);
646  if (NeInst) {
647    BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
648        NeInst, /*Unreachable=*/ false, ColdCallWeights));
649    IRBuilder<> ThenIRB(BI);
650    CallInst *Call = ThenIRB.CreateCall2(DFSanUnionFn, V1, V2);
651    Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
652    Call->addAttribute(1, Attribute::ZExt);
653    Call->addAttribute(2, Attribute::ZExt);
654
655    BasicBlock *Tail = BI->getSuccessor(0);
656    PHINode *Phi = PHINode::Create(ShadowTy, 2, "", Tail->begin());
657    Phi->addIncoming(Call, Call->getParent());
658    Phi->addIncoming(ZeroShadow, Head);
659    Pos = Phi;
660    return Phi;
661  } else {
662    assert(0 && "todo");
663    return 0;
664  }
665}
666
667// A convenience function which folds the shadows of each of the operands
668// of the provided instruction Inst, inserting the IR before Inst.  Returns
669// the computed union Value.
670Value *DFSanFunction::combineOperandShadows(Instruction *Inst) {
671  if (Inst->getNumOperands() == 0)
672    return DFS.ZeroShadow;
673
674  Value *Shadow = getShadow(Inst->getOperand(0));
675  for (unsigned i = 1, n = Inst->getNumOperands(); i != n; ++i) {
676    Shadow = DFS.combineShadows(Shadow, getShadow(Inst->getOperand(i)), Inst);
677  }
678  return Shadow;
679}
680
681void DFSanVisitor::visitOperandShadowInst(Instruction &I) {
682  Value *CombinedShadow = DFSF.combineOperandShadows(&I);
683  DFSF.setShadow(&I, CombinedShadow);
684}
685
686// Generates IR to load shadow corresponding to bytes [Addr, Addr+Size), where
687// Addr has alignment Align, and take the union of each of those shadows.
688Value *DFSanFunction::loadShadow(Value *Addr, uint64_t Size, uint64_t Align,
689                                 Instruction *Pos) {
690  if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
691    llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
692        AllocaShadowMap.find(AI);
693    if (i != AllocaShadowMap.end()) {
694      IRBuilder<> IRB(Pos);
695      return IRB.CreateLoad(i->second);
696    }
697  }
698
699  uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
700  SmallVector<Value *, 2> Objs;
701  GetUnderlyingObjects(Addr, Objs, DFS.DL);
702  bool AllConstants = true;
703  for (SmallVector<Value *, 2>::iterator i = Objs.begin(), e = Objs.end();
704       i != e; ++i) {
705    if (isa<Function>(*i) || isa<BlockAddress>(*i))
706      continue;
707    if (isa<GlobalVariable>(*i) && cast<GlobalVariable>(*i)->isConstant())
708      continue;
709
710    AllConstants = false;
711    break;
712  }
713  if (AllConstants)
714    return DFS.ZeroShadow;
715
716  Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
717  switch (Size) {
718  case 0:
719    return DFS.ZeroShadow;
720  case 1: {
721    LoadInst *LI = new LoadInst(ShadowAddr, "", Pos);
722    LI->setAlignment(ShadowAlign);
723    return LI;
724  }
725  case 2: {
726    IRBuilder<> IRB(Pos);
727    Value *ShadowAddr1 =
728        IRB.CreateGEP(ShadowAddr, ConstantInt::get(DFS.IntptrTy, 1));
729    return DFS.combineShadows(IRB.CreateAlignedLoad(ShadowAddr, ShadowAlign),
730                              IRB.CreateAlignedLoad(ShadowAddr1, ShadowAlign),
731                              Pos);
732  }
733  }
734  if (Size % (64 / DFS.ShadowWidth) == 0) {
735    // Fast path for the common case where each byte has identical shadow: load
736    // shadow 64 bits at a time, fall out to a __dfsan_union_load call if any
737    // shadow is non-equal.
738    BasicBlock *FallbackBB = BasicBlock::Create(*DFS.Ctx, "", F);
739    IRBuilder<> FallbackIRB(FallbackBB);
740    CallInst *FallbackCall = FallbackIRB.CreateCall2(
741        DFS.DFSanUnionLoadFn, ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size));
742    FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
743
744    // Compare each of the shadows stored in the loaded 64 bits to each other,
745    // by computing (WideShadow rotl ShadowWidth) == WideShadow.
746    IRBuilder<> IRB(Pos);
747    Value *WideAddr =
748        IRB.CreateBitCast(ShadowAddr, Type::getInt64PtrTy(*DFS.Ctx));
749    Value *WideShadow = IRB.CreateAlignedLoad(WideAddr, ShadowAlign);
750    Value *TruncShadow = IRB.CreateTrunc(WideShadow, DFS.ShadowTy);
751    Value *ShlShadow = IRB.CreateShl(WideShadow, DFS.ShadowWidth);
752    Value *ShrShadow = IRB.CreateLShr(WideShadow, 64 - DFS.ShadowWidth);
753    Value *RotShadow = IRB.CreateOr(ShlShadow, ShrShadow);
754    Value *ShadowsEq = IRB.CreateICmpEQ(WideShadow, RotShadow);
755
756    BasicBlock *Head = Pos->getParent();
757    BasicBlock *Tail = Head->splitBasicBlock(Pos);
758    // In the following code LastBr will refer to the previous basic block's
759    // conditional branch instruction, whose true successor is fixed up to point
760    // to the next block during the loop below or to the tail after the final
761    // iteration.
762    BranchInst *LastBr = BranchInst::Create(FallbackBB, FallbackBB, ShadowsEq);
763    ReplaceInstWithInst(Head->getTerminator(), LastBr);
764
765    for (uint64_t Ofs = 64 / DFS.ShadowWidth; Ofs != Size;
766         Ofs += 64 / DFS.ShadowWidth) {
767      BasicBlock *NextBB = BasicBlock::Create(*DFS.Ctx, "", F);
768      IRBuilder<> NextIRB(NextBB);
769      WideAddr = NextIRB.CreateGEP(WideAddr, ConstantInt::get(DFS.IntptrTy, 1));
770      Value *NextWideShadow = NextIRB.CreateAlignedLoad(WideAddr, ShadowAlign);
771      ShadowsEq = NextIRB.CreateICmpEQ(WideShadow, NextWideShadow);
772      LastBr->setSuccessor(0, NextBB);
773      LastBr = NextIRB.CreateCondBr(ShadowsEq, FallbackBB, FallbackBB);
774    }
775
776    LastBr->setSuccessor(0, Tail);
777    FallbackIRB.CreateBr(Tail);
778    PHINode *Shadow = PHINode::Create(DFS.ShadowTy, 2, "", &Tail->front());
779    Shadow->addIncoming(FallbackCall, FallbackBB);
780    Shadow->addIncoming(TruncShadow, LastBr->getParent());
781    return Shadow;
782  }
783
784  IRBuilder<> IRB(Pos);
785  CallInst *FallbackCall = IRB.CreateCall2(
786      DFS.DFSanUnionLoadFn, ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size));
787  FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
788  return FallbackCall;
789}
790
791void DFSanVisitor::visitLoadInst(LoadInst &LI) {
792  uint64_t Size = DFSF.DFS.DL->getTypeStoreSize(LI.getType());
793  uint64_t Align;
794  if (ClPreserveAlignment) {
795    Align = LI.getAlignment();
796    if (Align == 0)
797      Align = DFSF.DFS.DL->getABITypeAlignment(LI.getType());
798  } else {
799    Align = 1;
800  }
801  IRBuilder<> IRB(&LI);
802  Value *LoadedShadow =
803      DFSF.loadShadow(LI.getPointerOperand(), Size, Align, &LI);
804  Value *PtrShadow = DFSF.getShadow(LI.getPointerOperand());
805  DFSF.setShadow(&LI, DFSF.DFS.combineShadows(LoadedShadow, PtrShadow, &LI));
806}
807
808void DFSanFunction::storeShadow(Value *Addr, uint64_t Size, uint64_t Align,
809                                Value *Shadow, Instruction *Pos) {
810  if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
811    llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
812        AllocaShadowMap.find(AI);
813    if (i != AllocaShadowMap.end()) {
814      IRBuilder<> IRB(Pos);
815      IRB.CreateStore(Shadow, i->second);
816      return;
817    }
818  }
819
820  uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
821  IRBuilder<> IRB(Pos);
822  Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
823  if (Shadow == DFS.ZeroShadow) {
824    IntegerType *ShadowTy = IntegerType::get(*DFS.Ctx, Size * DFS.ShadowWidth);
825    Value *ExtZeroShadow = ConstantInt::get(ShadowTy, 0);
826    Value *ExtShadowAddr =
827        IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowTy));
828    IRB.CreateAlignedStore(ExtZeroShadow, ExtShadowAddr, ShadowAlign);
829    return;
830  }
831
832  const unsigned ShadowVecSize = 128 / DFS.ShadowWidth;
833  uint64_t Offset = 0;
834  if (Size >= ShadowVecSize) {
835    VectorType *ShadowVecTy = VectorType::get(DFS.ShadowTy, ShadowVecSize);
836    Value *ShadowVec = UndefValue::get(ShadowVecTy);
837    for (unsigned i = 0; i != ShadowVecSize; ++i) {
838      ShadowVec = IRB.CreateInsertElement(
839          ShadowVec, Shadow, ConstantInt::get(Type::getInt32Ty(*DFS.Ctx), i));
840    }
841    Value *ShadowVecAddr =
842        IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowVecTy));
843    do {
844      Value *CurShadowVecAddr = IRB.CreateConstGEP1_32(ShadowVecAddr, Offset);
845      IRB.CreateAlignedStore(ShadowVec, CurShadowVecAddr, ShadowAlign);
846      Size -= ShadowVecSize;
847      ++Offset;
848    } while (Size >= ShadowVecSize);
849    Offset *= ShadowVecSize;
850  }
851  while (Size > 0) {
852    Value *CurShadowAddr = IRB.CreateConstGEP1_32(ShadowAddr, Offset);
853    IRB.CreateAlignedStore(Shadow, CurShadowAddr, ShadowAlign);
854    --Size;
855    ++Offset;
856  }
857}
858
859void DFSanVisitor::visitStoreInst(StoreInst &SI) {
860  uint64_t Size =
861      DFSF.DFS.DL->getTypeStoreSize(SI.getValueOperand()->getType());
862  uint64_t Align;
863  if (ClPreserveAlignment) {
864    Align = SI.getAlignment();
865    if (Align == 0)
866      Align = DFSF.DFS.DL->getABITypeAlignment(SI.getValueOperand()->getType());
867  } else {
868    Align = 1;
869  }
870  DFSF.storeShadow(SI.getPointerOperand(), Size, Align,
871                   DFSF.getShadow(SI.getValueOperand()), &SI);
872}
873
874void DFSanVisitor::visitBinaryOperator(BinaryOperator &BO) {
875  visitOperandShadowInst(BO);
876}
877
878void DFSanVisitor::visitCastInst(CastInst &CI) { visitOperandShadowInst(CI); }
879
880void DFSanVisitor::visitCmpInst(CmpInst &CI) { visitOperandShadowInst(CI); }
881
882void DFSanVisitor::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
883  visitOperandShadowInst(GEPI);
884}
885
886void DFSanVisitor::visitExtractElementInst(ExtractElementInst &I) {
887  visitOperandShadowInst(I);
888}
889
890void DFSanVisitor::visitInsertElementInst(InsertElementInst &I) {
891  visitOperandShadowInst(I);
892}
893
894void DFSanVisitor::visitShuffleVectorInst(ShuffleVectorInst &I) {
895  visitOperandShadowInst(I);
896}
897
898void DFSanVisitor::visitExtractValueInst(ExtractValueInst &I) {
899  visitOperandShadowInst(I);
900}
901
902void DFSanVisitor::visitInsertValueInst(InsertValueInst &I) {
903  visitOperandShadowInst(I);
904}
905
906void DFSanVisitor::visitAllocaInst(AllocaInst &I) {
907  bool AllLoadsStores = true;
908  for (Instruction::use_iterator i = I.use_begin(), e = I.use_end(); i != e;
909       ++i) {
910    if (isa<LoadInst>(*i))
911      continue;
912
913    if (StoreInst *SI = dyn_cast<StoreInst>(*i)) {
914      if (SI->getPointerOperand() == &I)
915        continue;
916    }
917
918    AllLoadsStores = false;
919    break;
920  }
921  if (AllLoadsStores) {
922    IRBuilder<> IRB(&I);
923    DFSF.AllocaShadowMap[&I] = IRB.CreateAlloca(DFSF.DFS.ShadowTy);
924  }
925  DFSF.setShadow(&I, DFSF.DFS.ZeroShadow);
926}
927
928void DFSanVisitor::visitSelectInst(SelectInst &I) {
929  Value *CondShadow = DFSF.getShadow(I.getCondition());
930  Value *TrueShadow = DFSF.getShadow(I.getTrueValue());
931  Value *FalseShadow = DFSF.getShadow(I.getFalseValue());
932
933  if (isa<VectorType>(I.getCondition()->getType())) {
934    DFSF.setShadow(
935        &I, DFSF.DFS.combineShadows(
936                CondShadow,
937                DFSF.DFS.combineShadows(TrueShadow, FalseShadow, &I), &I));
938  } else {
939    Value *ShadowSel;
940    if (TrueShadow == FalseShadow) {
941      ShadowSel = TrueShadow;
942    } else {
943      ShadowSel =
944          SelectInst::Create(I.getCondition(), TrueShadow, FalseShadow, "", &I);
945    }
946    DFSF.setShadow(&I, DFSF.DFS.combineShadows(CondShadow, ShadowSel, &I));
947  }
948}
949
950void DFSanVisitor::visitMemTransferInst(MemTransferInst &I) {
951  IRBuilder<> IRB(&I);
952  Value *DestShadow = DFSF.DFS.getShadowAddress(I.getDest(), &I);
953  Value *SrcShadow = DFSF.DFS.getShadowAddress(I.getSource(), &I);
954  Value *LenShadow = IRB.CreateMul(
955      I.getLength(),
956      ConstantInt::get(I.getLength()->getType(), DFSF.DFS.ShadowWidth / 8));
957  Value *AlignShadow;
958  if (ClPreserveAlignment) {
959    AlignShadow = IRB.CreateMul(I.getAlignmentCst(),
960                                ConstantInt::get(I.getAlignmentCst()->getType(),
961                                                 DFSF.DFS.ShadowWidth / 8));
962  } else {
963    AlignShadow = ConstantInt::get(I.getAlignmentCst()->getType(),
964                                   DFSF.DFS.ShadowWidth / 8);
965  }
966  Type *Int8Ptr = Type::getInt8PtrTy(*DFSF.DFS.Ctx);
967  DestShadow = IRB.CreateBitCast(DestShadow, Int8Ptr);
968  SrcShadow = IRB.CreateBitCast(SrcShadow, Int8Ptr);
969  IRB.CreateCall5(I.getCalledValue(), DestShadow, SrcShadow, LenShadow,
970                  AlignShadow, I.getVolatileCst());
971}
972
973void DFSanVisitor::visitReturnInst(ReturnInst &RI) {
974  if (!DFSF.IsNativeABI && RI.getReturnValue()) {
975    switch (DFSF.IA) {
976    case DataFlowSanitizer::IA_TLS: {
977      Value *S = DFSF.getShadow(RI.getReturnValue());
978      IRBuilder<> IRB(&RI);
979      IRB.CreateStore(S, DFSF.getRetvalTLS());
980      break;
981    }
982    case DataFlowSanitizer::IA_Args: {
983      IRBuilder<> IRB(&RI);
984      Type *RT = DFSF.F->getFunctionType()->getReturnType();
985      Value *InsVal =
986          IRB.CreateInsertValue(UndefValue::get(RT), RI.getReturnValue(), 0);
987      Value *InsShadow =
988          IRB.CreateInsertValue(InsVal, DFSF.getShadow(RI.getReturnValue()), 1);
989      RI.setOperand(0, InsShadow);
990      break;
991    }
992    }
993  }
994}
995
996void DFSanVisitor::visitCallSite(CallSite CS) {
997  Function *F = CS.getCalledFunction();
998  if ((F && F->isIntrinsic()) || isa<InlineAsm>(CS.getCalledValue())) {
999    visitOperandShadowInst(*CS.getInstruction());
1000    return;
1001  }
1002
1003  IRBuilder<> IRB(CS.getInstruction());
1004
1005  DenseMap<Value *, Function *>::iterator i =
1006      DFSF.DFS.UnwrappedFnMap.find(CS.getCalledValue());
1007  if (i != DFSF.DFS.UnwrappedFnMap.end()) {
1008    Function *F = i->second;
1009    switch (DFSF.DFS.getWrapperKind(F)) {
1010    case DataFlowSanitizer::WK_Warning: {
1011      CS.setCalledFunction(F);
1012      IRB.CreateCall(DFSF.DFS.DFSanUnimplementedFn,
1013                     IRB.CreateGlobalStringPtr(F->getName()));
1014      DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
1015      return;
1016    }
1017    case DataFlowSanitizer::WK_Discard: {
1018      CS.setCalledFunction(F);
1019      DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
1020      return;
1021    }
1022    case DataFlowSanitizer::WK_Functional: {
1023      CS.setCalledFunction(F);
1024      visitOperandShadowInst(*CS.getInstruction());
1025      return;
1026    }
1027    case DataFlowSanitizer::WK_Custom: {
1028      // Don't try to handle invokes of custom functions, it's too complicated.
1029      // Instead, invoke the dfsw$ wrapper, which will in turn call the __dfsw_
1030      // wrapper.
1031      if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction())) {
1032        FunctionType *FT = F->getFunctionType();
1033        FunctionType *CustomFT = DFSF.DFS.getCustomFunctionType(FT);
1034        std::string CustomFName = "__dfsw_";
1035        CustomFName += F->getName();
1036        Constant *CustomF =
1037            DFSF.DFS.Mod->getOrInsertFunction(CustomFName, CustomFT);
1038        if (Function *CustomFn = dyn_cast<Function>(CustomF)) {
1039          CustomFn->copyAttributesFrom(F);
1040
1041          // Custom functions returning non-void will write to the return label.
1042          if (!FT->getReturnType()->isVoidTy()) {
1043            CustomFn->removeAttributes(AttributeSet::FunctionIndex,
1044                                       DFSF.DFS.ReadOnlyNoneAttrs);
1045          }
1046        }
1047
1048        std::vector<Value *> Args;
1049
1050        CallSite::arg_iterator i = CS.arg_begin();
1051        for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1052          Args.push_back(*i);
1053
1054        i = CS.arg_begin();
1055        for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1056          Args.push_back(DFSF.getShadow(*i));
1057
1058        if (!FT->getReturnType()->isVoidTy()) {
1059          if (!DFSF.LabelReturnAlloca) {
1060            DFSF.LabelReturnAlloca =
1061                new AllocaInst(DFSF.DFS.ShadowTy, "labelreturn",
1062                               DFSF.F->getEntryBlock().begin());
1063          }
1064          Args.push_back(DFSF.LabelReturnAlloca);
1065        }
1066
1067        CallInst *CustomCI = IRB.CreateCall(CustomF, Args);
1068        CustomCI->setCallingConv(CI->getCallingConv());
1069        CustomCI->setAttributes(CI->getAttributes());
1070
1071        if (!FT->getReturnType()->isVoidTy()) {
1072          LoadInst *LabelLoad = IRB.CreateLoad(DFSF.LabelReturnAlloca);
1073          DFSF.setShadow(CustomCI, LabelLoad);
1074        }
1075
1076        CI->replaceAllUsesWith(CustomCI);
1077        CI->eraseFromParent();
1078        return;
1079      }
1080      break;
1081    }
1082    }
1083  }
1084
1085  FunctionType *FT = cast<FunctionType>(
1086      CS.getCalledValue()->getType()->getPointerElementType());
1087  if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
1088    for (unsigned i = 0, n = FT->getNumParams(); i != n; ++i) {
1089      IRB.CreateStore(DFSF.getShadow(CS.getArgument(i)),
1090                      DFSF.getArgTLS(i, CS.getInstruction()));
1091    }
1092  }
1093
1094  Instruction *Next = 0;
1095  if (!CS.getType()->isVoidTy()) {
1096    if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
1097      if (II->getNormalDest()->getSinglePredecessor()) {
1098        Next = II->getNormalDest()->begin();
1099      } else {
1100        BasicBlock *NewBB =
1101            SplitEdge(II->getParent(), II->getNormalDest(), &DFSF.DFS);
1102        Next = NewBB->begin();
1103      }
1104    } else {
1105      Next = CS->getNextNode();
1106    }
1107
1108    if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
1109      IRBuilder<> NextIRB(Next);
1110      LoadInst *LI = NextIRB.CreateLoad(DFSF.getRetvalTLS());
1111      DFSF.SkipInsts.insert(LI);
1112      DFSF.setShadow(CS.getInstruction(), LI);
1113    }
1114  }
1115
1116  // Do all instrumentation for IA_Args down here to defer tampering with the
1117  // CFG in a way that SplitEdge may be able to detect.
1118  if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_Args) {
1119    FunctionType *NewFT = DFSF.DFS.getArgsFunctionType(FT);
1120    Value *Func =
1121        IRB.CreateBitCast(CS.getCalledValue(), PointerType::getUnqual(NewFT));
1122    std::vector<Value *> Args;
1123
1124    CallSite::arg_iterator i = CS.arg_begin(), e = CS.arg_end();
1125    for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1126      Args.push_back(*i);
1127
1128    i = CS.arg_begin();
1129    for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1130      Args.push_back(DFSF.getShadow(*i));
1131
1132    if (FT->isVarArg()) {
1133      unsigned VarArgSize = CS.arg_size() - FT->getNumParams();
1134      ArrayType *VarArgArrayTy = ArrayType::get(DFSF.DFS.ShadowTy, VarArgSize);
1135      AllocaInst *VarArgShadow =
1136          new AllocaInst(VarArgArrayTy, "", DFSF.F->getEntryBlock().begin());
1137      Args.push_back(IRB.CreateConstGEP2_32(VarArgShadow, 0, 0));
1138      for (unsigned n = 0; i != e; ++i, ++n) {
1139        IRB.CreateStore(DFSF.getShadow(*i),
1140                        IRB.CreateConstGEP2_32(VarArgShadow, 0, n));
1141        Args.push_back(*i);
1142      }
1143    }
1144
1145    CallSite NewCS;
1146    if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
1147      NewCS = IRB.CreateInvoke(Func, II->getNormalDest(), II->getUnwindDest(),
1148                               Args);
1149    } else {
1150      NewCS = IRB.CreateCall(Func, Args);
1151    }
1152    NewCS.setCallingConv(CS.getCallingConv());
1153    NewCS.setAttributes(CS.getAttributes().removeAttributes(
1154        *DFSF.DFS.Ctx, AttributeSet::ReturnIndex,
1155        AttributeFuncs::typeIncompatible(NewCS.getInstruction()->getType(),
1156                                         AttributeSet::ReturnIndex)));
1157
1158    if (Next) {
1159      ExtractValueInst *ExVal =
1160          ExtractValueInst::Create(NewCS.getInstruction(), 0, "", Next);
1161      DFSF.SkipInsts.insert(ExVal);
1162      ExtractValueInst *ExShadow =
1163          ExtractValueInst::Create(NewCS.getInstruction(), 1, "", Next);
1164      DFSF.SkipInsts.insert(ExShadow);
1165      DFSF.setShadow(ExVal, ExShadow);
1166
1167      CS.getInstruction()->replaceAllUsesWith(ExVal);
1168    }
1169
1170    CS.getInstruction()->eraseFromParent();
1171  }
1172}
1173
1174void DFSanVisitor::visitPHINode(PHINode &PN) {
1175  PHINode *ShadowPN =
1176      PHINode::Create(DFSF.DFS.ShadowTy, PN.getNumIncomingValues(), "", &PN);
1177
1178  // Give the shadow phi node valid predecessors to fool SplitEdge into working.
1179  Value *UndefShadow = UndefValue::get(DFSF.DFS.ShadowTy);
1180  for (PHINode::block_iterator i = PN.block_begin(), e = PN.block_end(); i != e;
1181       ++i) {
1182    ShadowPN->addIncoming(UndefShadow, *i);
1183  }
1184
1185  DFSF.PHIFixups.push_back(std::make_pair(&PN, ShadowPN));
1186  DFSF.setShadow(&PN, ShadowPN);
1187}
1188