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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/ADT/StringExtras.h"
52 #include "llvm/ADT/Triple.h"
53 #include "llvm/Analysis/ValueTracking.h"
54 #include "llvm/IR/Dominators.h"
55 #include "llvm/IR/DebugInfo.h"
56 #include "llvm/IR/IRBuilder.h"
57 #include "llvm/IR/InlineAsm.h"
58 #include "llvm/IR/InstVisitor.h"
59 #include "llvm/IR/LLVMContext.h"
60 #include "llvm/IR/MDBuilder.h"
61 #include "llvm/IR/Type.h"
62 #include "llvm/IR/Value.h"
63 #include "llvm/Pass.h"
64 #include "llvm/Support/CommandLine.h"
65 #include "llvm/Support/SpecialCaseList.h"
66 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
67 #include "llvm/Transforms/Utils/Local.h"
68 #include <algorithm>
69 #include <iterator>
70 #include <set>
71 #include <utility>
72 
73 using namespace llvm;
74 
75 // External symbol to be used when generating the shadow address for
76 // architectures with multiple VMAs. Instead of using a constant integer
77 // the runtime will set the external mask based on the VMA range.
78 static const char *const kDFSanExternShadowPtrMask = "__dfsan_shadow_ptr_mask";
79 
80 // The -dfsan-preserve-alignment flag controls whether this pass assumes that
81 // alignment requirements provided by the input IR are correct.  For example,
82 // if the input IR contains a load with alignment 8, this flag will cause
83 // the shadow load to have alignment 16.  This flag is disabled by default as
84 // we have unfortunately encountered too much code (including Clang itself;
85 // see PR14291) which performs misaligned access.
86 static cl::opt<bool> ClPreserveAlignment(
87     "dfsan-preserve-alignment",
88     cl::desc("respect alignment requirements provided by input IR"), cl::Hidden,
89     cl::init(false));
90 
91 // The ABI list files control how shadow parameters are passed. The pass treats
92 // every function labelled "uninstrumented" in the ABI list file as conforming
93 // to the "native" (i.e. unsanitized) ABI.  Unless the ABI list contains
94 // additional annotations for those functions, a call to one of those functions
95 // will produce a warning message, as the labelling behaviour of the function is
96 // unknown.  The other supported annotations are "functional" and "discard",
97 // which are described below under DataFlowSanitizer::WrapperKind.
98 static cl::list<std::string> ClABIListFiles(
99     "dfsan-abilist",
100     cl::desc("File listing native ABI functions and how the pass treats them"),
101     cl::Hidden);
102 
103 // Controls whether the pass uses IA_Args or IA_TLS as the ABI for instrumented
104 // functions (see DataFlowSanitizer::InstrumentedABI below).
105 static cl::opt<bool> ClArgsABI(
106     "dfsan-args-abi",
107     cl::desc("Use the argument ABI rather than the TLS ABI"),
108     cl::Hidden);
109 
110 // Controls whether the pass includes or ignores the labels of pointers in load
111 // instructions.
112 static cl::opt<bool> ClCombinePointerLabelsOnLoad(
113     "dfsan-combine-pointer-labels-on-load",
114     cl::desc("Combine the label of the pointer with the label of the data when "
115              "loading from memory."),
116     cl::Hidden, cl::init(true));
117 
118 // Controls whether the pass includes or ignores the labels of pointers in
119 // stores instructions.
120 static cl::opt<bool> ClCombinePointerLabelsOnStore(
121     "dfsan-combine-pointer-labels-on-store",
122     cl::desc("Combine the label of the pointer with the label of the data when "
123              "storing in memory."),
124     cl::Hidden, cl::init(false));
125 
126 static cl::opt<bool> ClDebugNonzeroLabels(
127     "dfsan-debug-nonzero-labels",
128     cl::desc("Insert calls to __dfsan_nonzero_label on observing a parameter, "
129              "load or return with a nonzero label"),
130     cl::Hidden);
131 
132 
133 namespace {
134 
GetGlobalTypeString(const GlobalValue & G)135 StringRef GetGlobalTypeString(const GlobalValue &G) {
136   // Types of GlobalVariables are always pointer types.
137   Type *GType = G.getValueType();
138   // For now we support blacklisting struct types only.
139   if (StructType *SGType = dyn_cast<StructType>(GType)) {
140     if (!SGType->isLiteral())
141       return SGType->getName();
142   }
143   return "<unknown type>";
144 }
145 
146 class DFSanABIList {
147   std::unique_ptr<SpecialCaseList> SCL;
148 
149  public:
DFSanABIList()150   DFSanABIList() {}
151 
set(std::unique_ptr<SpecialCaseList> List)152   void set(std::unique_ptr<SpecialCaseList> List) { SCL = std::move(List); }
153 
154   /// Returns whether either this function or its source file are listed in the
155   /// given category.
isIn(const Function & F,StringRef Category) const156   bool isIn(const Function &F, StringRef Category) const {
157     return isIn(*F.getParent(), Category) ||
158            SCL->inSection("fun", F.getName(), Category);
159   }
160 
161   /// Returns whether this global alias is listed in the given category.
162   ///
163   /// If GA aliases a function, the alias's name is matched as a function name
164   /// would be.  Similarly, aliases of globals are matched like globals.
isIn(const GlobalAlias & GA,StringRef Category) const165   bool isIn(const GlobalAlias &GA, StringRef Category) const {
166     if (isIn(*GA.getParent(), Category))
167       return true;
168 
169     if (isa<FunctionType>(GA.getValueType()))
170       return SCL->inSection("fun", GA.getName(), Category);
171 
172     return SCL->inSection("global", GA.getName(), Category) ||
173            SCL->inSection("type", GetGlobalTypeString(GA), Category);
174   }
175 
176   /// Returns whether this module is listed in the given category.
isIn(const Module & M,StringRef Category) const177   bool isIn(const Module &M, StringRef Category) const {
178     return SCL->inSection("src", M.getModuleIdentifier(), Category);
179   }
180 };
181 
182 class DataFlowSanitizer : public ModulePass {
183   friend struct DFSanFunction;
184   friend class DFSanVisitor;
185 
186   enum {
187     ShadowWidth = 16
188   };
189 
190   /// Which ABI should be used for instrumented functions?
191   enum InstrumentedABI {
192     /// Argument and return value labels are passed through additional
193     /// arguments and by modifying the return type.
194     IA_Args,
195 
196     /// Argument and return value labels are passed through TLS variables
197     /// __dfsan_arg_tls and __dfsan_retval_tls.
198     IA_TLS
199   };
200 
201   /// How should calls to uninstrumented functions be handled?
202   enum WrapperKind {
203     /// This function is present in an uninstrumented form but we don't know
204     /// how it should be handled.  Print a warning and call the function anyway.
205     /// Don't label the return value.
206     WK_Warning,
207 
208     /// This function does not write to (user-accessible) memory, and its return
209     /// value is unlabelled.
210     WK_Discard,
211 
212     /// This function does not write to (user-accessible) memory, and the label
213     /// of its return value is the union of the label of its arguments.
214     WK_Functional,
215 
216     /// Instead of calling the function, a custom wrapper __dfsw_F is called,
217     /// where F is the name of the function.  This function may wrap the
218     /// original function or provide its own implementation.  This is similar to
219     /// the IA_Args ABI, except that IA_Args uses a struct return type to
220     /// pass the return value shadow in a register, while WK_Custom uses an
221     /// extra pointer argument to return the shadow.  This allows the wrapped
222     /// form of the function type to be expressed in C.
223     WK_Custom
224   };
225 
226   Module *Mod;
227   LLVMContext *Ctx;
228   IntegerType *ShadowTy;
229   PointerType *ShadowPtrTy;
230   IntegerType *IntptrTy;
231   ConstantInt *ZeroShadow;
232   ConstantInt *ShadowPtrMask;
233   ConstantInt *ShadowPtrMul;
234   Constant *ArgTLS;
235   Constant *RetvalTLS;
236   void *(*GetArgTLSPtr)();
237   void *(*GetRetvalTLSPtr)();
238   Constant *GetArgTLS;
239   Constant *GetRetvalTLS;
240   Constant *ExternalShadowMask;
241   FunctionType *DFSanUnionFnTy;
242   FunctionType *DFSanUnionLoadFnTy;
243   FunctionType *DFSanUnimplementedFnTy;
244   FunctionType *DFSanSetLabelFnTy;
245   FunctionType *DFSanNonzeroLabelFnTy;
246   FunctionType *DFSanVarargWrapperFnTy;
247   Constant *DFSanUnionFn;
248   Constant *DFSanCheckedUnionFn;
249   Constant *DFSanUnionLoadFn;
250   Constant *DFSanUnimplementedFn;
251   Constant *DFSanSetLabelFn;
252   Constant *DFSanNonzeroLabelFn;
253   Constant *DFSanVarargWrapperFn;
254   MDNode *ColdCallWeights;
255   DFSanABIList ABIList;
256   DenseMap<Value *, Function *> UnwrappedFnMap;
257   AttributeSet ReadOnlyNoneAttrs;
258   bool DFSanRuntimeShadowMask;
259 
260   Value *getShadowAddress(Value *Addr, Instruction *Pos);
261   bool isInstrumented(const Function *F);
262   bool isInstrumented(const GlobalAlias *GA);
263   FunctionType *getArgsFunctionType(FunctionType *T);
264   FunctionType *getTrampolineFunctionType(FunctionType *T);
265   FunctionType *getCustomFunctionType(FunctionType *T);
266   InstrumentedABI getInstrumentedABI();
267   WrapperKind getWrapperKind(Function *F);
268   void addGlobalNamePrefix(GlobalValue *GV);
269   Function *buildWrapperFunction(Function *F, StringRef NewFName,
270                                  GlobalValue::LinkageTypes NewFLink,
271                                  FunctionType *NewFT);
272   Constant *getOrBuildTrampolineFunction(FunctionType *FT, StringRef FName);
273 
274  public:
275   DataFlowSanitizer(
276       const std::vector<std::string> &ABIListFiles = std::vector<std::string>(),
277       void *(*getArgTLS)() = nullptr, void *(*getRetValTLS)() = nullptr);
278   static char ID;
279   bool doInitialization(Module &M) override;
280   bool runOnModule(Module &M) override;
281 };
282 
283 struct DFSanFunction {
284   DataFlowSanitizer &DFS;
285   Function *F;
286   DominatorTree DT;
287   DataFlowSanitizer::InstrumentedABI IA;
288   bool IsNativeABI;
289   Value *ArgTLSPtr;
290   Value *RetvalTLSPtr;
291   AllocaInst *LabelReturnAlloca;
292   DenseMap<Value *, Value *> ValShadowMap;
293   DenseMap<AllocaInst *, AllocaInst *> AllocaShadowMap;
294   std::vector<std::pair<PHINode *, PHINode *> > PHIFixups;
295   DenseSet<Instruction *> SkipInsts;
296   std::vector<Value *> NonZeroChecks;
297   bool AvoidNewBlocks;
298 
299   struct CachedCombinedShadow {
300     BasicBlock *Block;
301     Value *Shadow;
302   };
303   DenseMap<std::pair<Value *, Value *>, CachedCombinedShadow>
304       CachedCombinedShadows;
305   DenseMap<Value *, std::set<Value *>> ShadowElements;
306 
DFSanFunction__anon267cbafd0111::DFSanFunction307   DFSanFunction(DataFlowSanitizer &DFS, Function *F, bool IsNativeABI)
308       : DFS(DFS), F(F), IA(DFS.getInstrumentedABI()),
309         IsNativeABI(IsNativeABI), ArgTLSPtr(nullptr), RetvalTLSPtr(nullptr),
310         LabelReturnAlloca(nullptr) {
311     DT.recalculate(*F);
312     // FIXME: Need to track down the register allocator issue which causes poor
313     // performance in pathological cases with large numbers of basic blocks.
314     AvoidNewBlocks = F->size() > 1000;
315   }
316   Value *getArgTLSPtr();
317   Value *getArgTLS(unsigned Index, Instruction *Pos);
318   Value *getRetvalTLS();
319   Value *getShadow(Value *V);
320   void setShadow(Instruction *I, Value *Shadow);
321   Value *combineShadows(Value *V1, Value *V2, Instruction *Pos);
322   Value *combineOperandShadows(Instruction *Inst);
323   Value *loadShadow(Value *ShadowAddr, uint64_t Size, uint64_t Align,
324                     Instruction *Pos);
325   void storeShadow(Value *Addr, uint64_t Size, uint64_t Align, Value *Shadow,
326                    Instruction *Pos);
327 };
328 
329 class DFSanVisitor : public InstVisitor<DFSanVisitor> {
330  public:
331   DFSanFunction &DFSF;
DFSanVisitor(DFSanFunction & DFSF)332   DFSanVisitor(DFSanFunction &DFSF) : DFSF(DFSF) {}
333 
334   void visitOperandShadowInst(Instruction &I);
335 
336   void visitBinaryOperator(BinaryOperator &BO);
337   void visitCastInst(CastInst &CI);
338   void visitCmpInst(CmpInst &CI);
339   void visitGetElementPtrInst(GetElementPtrInst &GEPI);
340   void visitLoadInst(LoadInst &LI);
341   void visitStoreInst(StoreInst &SI);
342   void visitReturnInst(ReturnInst &RI);
343   void visitCallSite(CallSite CS);
344   void visitPHINode(PHINode &PN);
345   void visitExtractElementInst(ExtractElementInst &I);
346   void visitInsertElementInst(InsertElementInst &I);
347   void visitShuffleVectorInst(ShuffleVectorInst &I);
348   void visitExtractValueInst(ExtractValueInst &I);
349   void visitInsertValueInst(InsertValueInst &I);
350   void visitAllocaInst(AllocaInst &I);
351   void visitSelectInst(SelectInst &I);
352   void visitMemSetInst(MemSetInst &I);
353   void visitMemTransferInst(MemTransferInst &I);
354 };
355 
356 }
357 
358 char DataFlowSanitizer::ID;
359 INITIALIZE_PASS(DataFlowSanitizer, "dfsan",
360                 "DataFlowSanitizer: dynamic data flow analysis.", false, false)
361 
362 ModulePass *
createDataFlowSanitizerPass(const std::vector<std::string> & ABIListFiles,void * (* getArgTLS)(),void * (* getRetValTLS)())363 llvm::createDataFlowSanitizerPass(const std::vector<std::string> &ABIListFiles,
364                                   void *(*getArgTLS)(),
365                                   void *(*getRetValTLS)()) {
366   return new DataFlowSanitizer(ABIListFiles, getArgTLS, getRetValTLS);
367 }
368 
DataFlowSanitizer(const std::vector<std::string> & ABIListFiles,void * (* getArgTLS)(),void * (* getRetValTLS)())369 DataFlowSanitizer::DataFlowSanitizer(
370     const std::vector<std::string> &ABIListFiles, void *(*getArgTLS)(),
371     void *(*getRetValTLS)())
372     : ModulePass(ID), GetArgTLSPtr(getArgTLS), GetRetvalTLSPtr(getRetValTLS),
373       DFSanRuntimeShadowMask(false) {
374   std::vector<std::string> AllABIListFiles(std::move(ABIListFiles));
375   AllABIListFiles.insert(AllABIListFiles.end(), ClABIListFiles.begin(),
376                          ClABIListFiles.end());
377   ABIList.set(SpecialCaseList::createOrDie(AllABIListFiles));
378 }
379 
getArgsFunctionType(FunctionType * T)380 FunctionType *DataFlowSanitizer::getArgsFunctionType(FunctionType *T) {
381   llvm::SmallVector<Type *, 4> ArgTypes(T->param_begin(), T->param_end());
382   ArgTypes.append(T->getNumParams(), ShadowTy);
383   if (T->isVarArg())
384     ArgTypes.push_back(ShadowPtrTy);
385   Type *RetType = T->getReturnType();
386   if (!RetType->isVoidTy())
387     RetType = StructType::get(RetType, ShadowTy, (Type *)nullptr);
388   return FunctionType::get(RetType, ArgTypes, T->isVarArg());
389 }
390 
getTrampolineFunctionType(FunctionType * T)391 FunctionType *DataFlowSanitizer::getTrampolineFunctionType(FunctionType *T) {
392   assert(!T->isVarArg());
393   llvm::SmallVector<Type *, 4> ArgTypes;
394   ArgTypes.push_back(T->getPointerTo());
395   ArgTypes.append(T->param_begin(), T->param_end());
396   ArgTypes.append(T->getNumParams(), ShadowTy);
397   Type *RetType = T->getReturnType();
398   if (!RetType->isVoidTy())
399     ArgTypes.push_back(ShadowPtrTy);
400   return FunctionType::get(T->getReturnType(), ArgTypes, false);
401 }
402 
getCustomFunctionType(FunctionType * T)403 FunctionType *DataFlowSanitizer::getCustomFunctionType(FunctionType *T) {
404   llvm::SmallVector<Type *, 4> ArgTypes;
405   for (FunctionType::param_iterator i = T->param_begin(), e = T->param_end();
406        i != e; ++i) {
407     FunctionType *FT;
408     if (isa<PointerType>(*i) && (FT = dyn_cast<FunctionType>(cast<PointerType>(
409                                      *i)->getElementType()))) {
410       ArgTypes.push_back(getTrampolineFunctionType(FT)->getPointerTo());
411       ArgTypes.push_back(Type::getInt8PtrTy(*Ctx));
412     } else {
413       ArgTypes.push_back(*i);
414     }
415   }
416   for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
417     ArgTypes.push_back(ShadowTy);
418   if (T->isVarArg())
419     ArgTypes.push_back(ShadowPtrTy);
420   Type *RetType = T->getReturnType();
421   if (!RetType->isVoidTy())
422     ArgTypes.push_back(ShadowPtrTy);
423   return FunctionType::get(T->getReturnType(), ArgTypes, T->isVarArg());
424 }
425 
doInitialization(Module & M)426 bool DataFlowSanitizer::doInitialization(Module &M) {
427   llvm::Triple TargetTriple(M.getTargetTriple());
428   bool IsX86_64 = TargetTriple.getArch() == llvm::Triple::x86_64;
429   bool IsMIPS64 = TargetTriple.getArch() == llvm::Triple::mips64 ||
430                   TargetTriple.getArch() == llvm::Triple::mips64el;
431   bool IsAArch64 = TargetTriple.getArch() == llvm::Triple::aarch64 ||
432                    TargetTriple.getArch() == llvm::Triple::aarch64_be;
433 
434   const DataLayout &DL = M.getDataLayout();
435 
436   Mod = &M;
437   Ctx = &M.getContext();
438   ShadowTy = IntegerType::get(*Ctx, ShadowWidth);
439   ShadowPtrTy = PointerType::getUnqual(ShadowTy);
440   IntptrTy = DL.getIntPtrType(*Ctx);
441   ZeroShadow = ConstantInt::getSigned(ShadowTy, 0);
442   ShadowPtrMul = ConstantInt::getSigned(IntptrTy, ShadowWidth / 8);
443   if (IsX86_64)
444     ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0x700000000000LL);
445   else if (IsMIPS64)
446     ShadowPtrMask = ConstantInt::getSigned(IntptrTy, ~0xF000000000LL);
447   // AArch64 supports multiple VMAs and the shadow mask is set at runtime.
448   else if (IsAArch64)
449     DFSanRuntimeShadowMask = true;
450   else
451     report_fatal_error("unsupported triple");
452 
453   Type *DFSanUnionArgs[2] = { ShadowTy, ShadowTy };
454   DFSanUnionFnTy =
455       FunctionType::get(ShadowTy, DFSanUnionArgs, /*isVarArg=*/ false);
456   Type *DFSanUnionLoadArgs[2] = { ShadowPtrTy, IntptrTy };
457   DFSanUnionLoadFnTy =
458       FunctionType::get(ShadowTy, DFSanUnionLoadArgs, /*isVarArg=*/ false);
459   DFSanUnimplementedFnTy = FunctionType::get(
460       Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);
461   Type *DFSanSetLabelArgs[3] = { ShadowTy, Type::getInt8PtrTy(*Ctx), IntptrTy };
462   DFSanSetLabelFnTy = FunctionType::get(Type::getVoidTy(*Ctx),
463                                         DFSanSetLabelArgs, /*isVarArg=*/false);
464   DFSanNonzeroLabelFnTy = FunctionType::get(
465       Type::getVoidTy(*Ctx), None, /*isVarArg=*/false);
466   DFSanVarargWrapperFnTy = FunctionType::get(
467       Type::getVoidTy(*Ctx), Type::getInt8PtrTy(*Ctx), /*isVarArg=*/false);
468 
469   if (GetArgTLSPtr) {
470     Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
471     ArgTLS = nullptr;
472     GetArgTLS = ConstantExpr::getIntToPtr(
473         ConstantInt::get(IntptrTy, uintptr_t(GetArgTLSPtr)),
474         PointerType::getUnqual(
475             FunctionType::get(PointerType::getUnqual(ArgTLSTy),
476                               (Type *)nullptr)));
477   }
478   if (GetRetvalTLSPtr) {
479     RetvalTLS = nullptr;
480     GetRetvalTLS = ConstantExpr::getIntToPtr(
481         ConstantInt::get(IntptrTy, uintptr_t(GetRetvalTLSPtr)),
482         PointerType::getUnqual(
483             FunctionType::get(PointerType::getUnqual(ShadowTy),
484                               (Type *)nullptr)));
485   }
486 
487   ColdCallWeights = MDBuilder(*Ctx).createBranchWeights(1, 1000);
488   return true;
489 }
490 
isInstrumented(const Function * F)491 bool DataFlowSanitizer::isInstrumented(const Function *F) {
492   return !ABIList.isIn(*F, "uninstrumented");
493 }
494 
isInstrumented(const GlobalAlias * GA)495 bool DataFlowSanitizer::isInstrumented(const GlobalAlias *GA) {
496   return !ABIList.isIn(*GA, "uninstrumented");
497 }
498 
getInstrumentedABI()499 DataFlowSanitizer::InstrumentedABI DataFlowSanitizer::getInstrumentedABI() {
500   return ClArgsABI ? IA_Args : IA_TLS;
501 }
502 
getWrapperKind(Function * F)503 DataFlowSanitizer::WrapperKind DataFlowSanitizer::getWrapperKind(Function *F) {
504   if (ABIList.isIn(*F, "functional"))
505     return WK_Functional;
506   if (ABIList.isIn(*F, "discard"))
507     return WK_Discard;
508   if (ABIList.isIn(*F, "custom"))
509     return WK_Custom;
510 
511   return WK_Warning;
512 }
513 
addGlobalNamePrefix(GlobalValue * GV)514 void DataFlowSanitizer::addGlobalNamePrefix(GlobalValue *GV) {
515   std::string GVName = GV->getName(), Prefix = "dfs$";
516   GV->setName(Prefix + GVName);
517 
518   // Try to change the name of the function in module inline asm.  We only do
519   // this for specific asm directives, currently only ".symver", to try to avoid
520   // corrupting asm which happens to contain the symbol name as a substring.
521   // Note that the substitution for .symver assumes that the versioned symbol
522   // also has an instrumented name.
523   std::string Asm = GV->getParent()->getModuleInlineAsm();
524   std::string SearchStr = ".symver " + GVName + ",";
525   size_t Pos = Asm.find(SearchStr);
526   if (Pos != std::string::npos) {
527     Asm.replace(Pos, SearchStr.size(),
528                 ".symver " + Prefix + GVName + "," + Prefix);
529     GV->getParent()->setModuleInlineAsm(Asm);
530   }
531 }
532 
533 Function *
buildWrapperFunction(Function * F,StringRef NewFName,GlobalValue::LinkageTypes NewFLink,FunctionType * NewFT)534 DataFlowSanitizer::buildWrapperFunction(Function *F, StringRef NewFName,
535                                         GlobalValue::LinkageTypes NewFLink,
536                                         FunctionType *NewFT) {
537   FunctionType *FT = F->getFunctionType();
538   Function *NewF = Function::Create(NewFT, NewFLink, NewFName,
539                                     F->getParent());
540   NewF->copyAttributesFrom(F);
541   NewF->removeAttributes(
542     AttributeSet::ReturnIndex,
543     AttributeSet::get(F->getContext(), AttributeSet::ReturnIndex,
544                     AttributeFuncs::typeIncompatible(NewFT->getReturnType())));
545 
546   BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", NewF);
547   if (F->isVarArg()) {
548     NewF->removeAttributes(
549         AttributeSet::FunctionIndex,
550         AttributeSet().addAttribute(*Ctx, AttributeSet::FunctionIndex,
551                                     "split-stack"));
552     CallInst::Create(DFSanVarargWrapperFn,
553                      IRBuilder<>(BB).CreateGlobalStringPtr(F->getName()), "",
554                      BB);
555     new UnreachableInst(*Ctx, BB);
556   } else {
557     std::vector<Value *> Args;
558     unsigned n = FT->getNumParams();
559     for (Function::arg_iterator ai = NewF->arg_begin(); n != 0; ++ai, --n)
560       Args.push_back(&*ai);
561     CallInst *CI = CallInst::Create(F, Args, "", BB);
562     if (FT->getReturnType()->isVoidTy())
563       ReturnInst::Create(*Ctx, BB);
564     else
565       ReturnInst::Create(*Ctx, CI, BB);
566   }
567 
568   return NewF;
569 }
570 
getOrBuildTrampolineFunction(FunctionType * FT,StringRef FName)571 Constant *DataFlowSanitizer::getOrBuildTrampolineFunction(FunctionType *FT,
572                                                           StringRef FName) {
573   FunctionType *FTT = getTrampolineFunctionType(FT);
574   Constant *C = Mod->getOrInsertFunction(FName, FTT);
575   Function *F = dyn_cast<Function>(C);
576   if (F && F->isDeclaration()) {
577     F->setLinkage(GlobalValue::LinkOnceODRLinkage);
578     BasicBlock *BB = BasicBlock::Create(*Ctx, "entry", F);
579     std::vector<Value *> Args;
580     Function::arg_iterator AI = F->arg_begin(); ++AI;
581     for (unsigned N = FT->getNumParams(); N != 0; ++AI, --N)
582       Args.push_back(&*AI);
583     CallInst *CI =
584         CallInst::Create(&F->getArgumentList().front(), Args, "", BB);
585     ReturnInst *RI;
586     if (FT->getReturnType()->isVoidTy())
587       RI = ReturnInst::Create(*Ctx, BB);
588     else
589       RI = ReturnInst::Create(*Ctx, CI, BB);
590 
591     DFSanFunction DFSF(*this, F, /*IsNativeABI=*/true);
592     Function::arg_iterator ValAI = F->arg_begin(), ShadowAI = AI; ++ValAI;
593     for (unsigned N = FT->getNumParams(); N != 0; ++ValAI, ++ShadowAI, --N)
594       DFSF.ValShadowMap[&*ValAI] = &*ShadowAI;
595     DFSanVisitor(DFSF).visitCallInst(*CI);
596     if (!FT->getReturnType()->isVoidTy())
597       new StoreInst(DFSF.getShadow(RI->getReturnValue()),
598                     &F->getArgumentList().back(), RI);
599   }
600 
601   return C;
602 }
603 
runOnModule(Module & M)604 bool DataFlowSanitizer::runOnModule(Module &M) {
605   if (ABIList.isIn(M, "skip"))
606     return false;
607 
608   if (!GetArgTLSPtr) {
609     Type *ArgTLSTy = ArrayType::get(ShadowTy, 64);
610     ArgTLS = Mod->getOrInsertGlobal("__dfsan_arg_tls", ArgTLSTy);
611     if (GlobalVariable *G = dyn_cast<GlobalVariable>(ArgTLS))
612       G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
613   }
614   if (!GetRetvalTLSPtr) {
615     RetvalTLS = Mod->getOrInsertGlobal("__dfsan_retval_tls", ShadowTy);
616     if (GlobalVariable *G = dyn_cast<GlobalVariable>(RetvalTLS))
617       G->setThreadLocalMode(GlobalVariable::InitialExecTLSModel);
618   }
619 
620   ExternalShadowMask =
621       Mod->getOrInsertGlobal(kDFSanExternShadowPtrMask, IntptrTy);
622 
623   DFSanUnionFn = Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy);
624   if (Function *F = dyn_cast<Function>(DFSanUnionFn)) {
625     F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
626     F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
627     F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
628     F->addAttribute(1, Attribute::ZExt);
629     F->addAttribute(2, Attribute::ZExt);
630   }
631   DFSanCheckedUnionFn = Mod->getOrInsertFunction("dfsan_union", DFSanUnionFnTy);
632   if (Function *F = dyn_cast<Function>(DFSanCheckedUnionFn)) {
633     F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
634     F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
635     F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
636     F->addAttribute(1, Attribute::ZExt);
637     F->addAttribute(2, Attribute::ZExt);
638   }
639   DFSanUnionLoadFn =
640       Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy);
641   if (Function *F = dyn_cast<Function>(DFSanUnionLoadFn)) {
642     F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
643     F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadOnly);
644     F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
645   }
646   DFSanUnimplementedFn =
647       Mod->getOrInsertFunction("__dfsan_unimplemented", DFSanUnimplementedFnTy);
648   DFSanSetLabelFn =
649       Mod->getOrInsertFunction("__dfsan_set_label", DFSanSetLabelFnTy);
650   if (Function *F = dyn_cast<Function>(DFSanSetLabelFn)) {
651     F->addAttribute(1, Attribute::ZExt);
652   }
653   DFSanNonzeroLabelFn =
654       Mod->getOrInsertFunction("__dfsan_nonzero_label", DFSanNonzeroLabelFnTy);
655   DFSanVarargWrapperFn = Mod->getOrInsertFunction("__dfsan_vararg_wrapper",
656                                                   DFSanVarargWrapperFnTy);
657 
658   std::vector<Function *> FnsToInstrument;
659   llvm::SmallPtrSet<Function *, 2> FnsWithNativeABI;
660   for (Function &i : M) {
661     if (!i.isIntrinsic() &&
662         &i != DFSanUnionFn &&
663         &i != DFSanCheckedUnionFn &&
664         &i != DFSanUnionLoadFn &&
665         &i != DFSanUnimplementedFn &&
666         &i != DFSanSetLabelFn &&
667         &i != DFSanNonzeroLabelFn &&
668         &i != DFSanVarargWrapperFn)
669       FnsToInstrument.push_back(&i);
670   }
671 
672   // Give function aliases prefixes when necessary, and build wrappers where the
673   // instrumentedness is inconsistent.
674   for (Module::alias_iterator i = M.alias_begin(), e = M.alias_end(); i != e;) {
675     GlobalAlias *GA = &*i;
676     ++i;
677     // Don't stop on weak.  We assume people aren't playing games with the
678     // instrumentedness of overridden weak aliases.
679     if (auto F = dyn_cast<Function>(GA->getBaseObject())) {
680       bool GAInst = isInstrumented(GA), FInst = isInstrumented(F);
681       if (GAInst && FInst) {
682         addGlobalNamePrefix(GA);
683       } else if (GAInst != FInst) {
684         // Non-instrumented alias of an instrumented function, or vice versa.
685         // Replace the alias with a native-ABI wrapper of the aliasee.  The pass
686         // below will take care of instrumenting it.
687         Function *NewF =
688             buildWrapperFunction(F, "", GA->getLinkage(), F->getFunctionType());
689         GA->replaceAllUsesWith(ConstantExpr::getBitCast(NewF, GA->getType()));
690         NewF->takeName(GA);
691         GA->eraseFromParent();
692         FnsToInstrument.push_back(NewF);
693       }
694     }
695   }
696 
697   AttrBuilder B;
698   B.addAttribute(Attribute::ReadOnly).addAttribute(Attribute::ReadNone);
699   ReadOnlyNoneAttrs = AttributeSet::get(*Ctx, AttributeSet::FunctionIndex, B);
700 
701   // First, change the ABI of every function in the module.  ABI-listed
702   // functions keep their original ABI and get a wrapper function.
703   for (std::vector<Function *>::iterator i = FnsToInstrument.begin(),
704                                          e = FnsToInstrument.end();
705        i != e; ++i) {
706     Function &F = **i;
707     FunctionType *FT = F.getFunctionType();
708 
709     bool IsZeroArgsVoidRet = (FT->getNumParams() == 0 && !FT->isVarArg() &&
710                               FT->getReturnType()->isVoidTy());
711 
712     if (isInstrumented(&F)) {
713       // Instrumented functions get a 'dfs$' prefix.  This allows us to more
714       // easily identify cases of mismatching ABIs.
715       if (getInstrumentedABI() == IA_Args && !IsZeroArgsVoidRet) {
716         FunctionType *NewFT = getArgsFunctionType(FT);
717         Function *NewF = Function::Create(NewFT, F.getLinkage(), "", &M);
718         NewF->copyAttributesFrom(&F);
719         NewF->removeAttributes(
720           AttributeSet::ReturnIndex,
721           AttributeSet::get(NewF->getContext(), AttributeSet::ReturnIndex,
722                     AttributeFuncs::typeIncompatible(NewFT->getReturnType())));
723         for (Function::arg_iterator FArg = F.arg_begin(),
724                                     NewFArg = NewF->arg_begin(),
725                                     FArgEnd = F.arg_end();
726              FArg != FArgEnd; ++FArg, ++NewFArg) {
727           FArg->replaceAllUsesWith(&*NewFArg);
728         }
729         NewF->getBasicBlockList().splice(NewF->begin(), F.getBasicBlockList());
730 
731         for (Function::user_iterator UI = F.user_begin(), UE = F.user_end();
732              UI != UE;) {
733           BlockAddress *BA = dyn_cast<BlockAddress>(*UI);
734           ++UI;
735           if (BA) {
736             BA->replaceAllUsesWith(
737                 BlockAddress::get(NewF, BA->getBasicBlock()));
738             delete BA;
739           }
740         }
741         F.replaceAllUsesWith(
742             ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT)));
743         NewF->takeName(&F);
744         F.eraseFromParent();
745         *i = NewF;
746         addGlobalNamePrefix(NewF);
747       } else {
748         addGlobalNamePrefix(&F);
749       }
750     } else if (!IsZeroArgsVoidRet || getWrapperKind(&F) == WK_Custom) {
751       // Build a wrapper function for F.  The wrapper simply calls F, and is
752       // added to FnsToInstrument so that any instrumentation according to its
753       // WrapperKind is done in the second pass below.
754       FunctionType *NewFT = getInstrumentedABI() == IA_Args
755                                 ? getArgsFunctionType(FT)
756                                 : FT;
757       Function *NewF = buildWrapperFunction(
758           &F, std::string("dfsw$") + std::string(F.getName()),
759           GlobalValue::LinkOnceODRLinkage, NewFT);
760       if (getInstrumentedABI() == IA_TLS)
761         NewF->removeAttributes(AttributeSet::FunctionIndex, ReadOnlyNoneAttrs);
762 
763       Value *WrappedFnCst =
764           ConstantExpr::getBitCast(NewF, PointerType::getUnqual(FT));
765       F.replaceAllUsesWith(WrappedFnCst);
766 
767       UnwrappedFnMap[WrappedFnCst] = &F;
768       *i = NewF;
769 
770       if (!F.isDeclaration()) {
771         // This function is probably defining an interposition of an
772         // uninstrumented function and hence needs to keep the original ABI.
773         // But any functions it may call need to use the instrumented ABI, so
774         // we instrument it in a mode which preserves the original ABI.
775         FnsWithNativeABI.insert(&F);
776 
777         // This code needs to rebuild the iterators, as they may be invalidated
778         // by the push_back, taking care that the new range does not include
779         // any functions added by this code.
780         size_t N = i - FnsToInstrument.begin(),
781                Count = e - FnsToInstrument.begin();
782         FnsToInstrument.push_back(&F);
783         i = FnsToInstrument.begin() + N;
784         e = FnsToInstrument.begin() + Count;
785       }
786                // Hopefully, nobody will try to indirectly call a vararg
787                // function... yet.
788     } else if (FT->isVarArg()) {
789       UnwrappedFnMap[&F] = &F;
790       *i = nullptr;
791     }
792   }
793 
794   for (Function *i : FnsToInstrument) {
795     if (!i || i->isDeclaration())
796       continue;
797 
798     removeUnreachableBlocks(*i);
799 
800     DFSanFunction DFSF(*this, i, FnsWithNativeABI.count(i));
801 
802     // DFSanVisitor may create new basic blocks, which confuses df_iterator.
803     // Build a copy of the list before iterating over it.
804     llvm::SmallVector<BasicBlock *, 4> BBList(depth_first(&i->getEntryBlock()));
805 
806     for (BasicBlock *i : BBList) {
807       Instruction *Inst = &i->front();
808       while (1) {
809         // DFSanVisitor may split the current basic block, changing the current
810         // instruction's next pointer and moving the next instruction to the
811         // tail block from which we should continue.
812         Instruction *Next = Inst->getNextNode();
813         // DFSanVisitor may delete Inst, so keep track of whether it was a
814         // terminator.
815         bool IsTerminator = isa<TerminatorInst>(Inst);
816         if (!DFSF.SkipInsts.count(Inst))
817           DFSanVisitor(DFSF).visit(Inst);
818         if (IsTerminator)
819           break;
820         Inst = Next;
821       }
822     }
823 
824     // We will not necessarily be able to compute the shadow for every phi node
825     // until we have visited every block.  Therefore, the code that handles phi
826     // nodes adds them to the PHIFixups list so that they can be properly
827     // handled here.
828     for (std::vector<std::pair<PHINode *, PHINode *> >::iterator
829              i = DFSF.PHIFixups.begin(),
830              e = DFSF.PHIFixups.end();
831          i != e; ++i) {
832       for (unsigned val = 0, n = i->first->getNumIncomingValues(); val != n;
833            ++val) {
834         i->second->setIncomingValue(
835             val, DFSF.getShadow(i->first->getIncomingValue(val)));
836       }
837     }
838 
839     // -dfsan-debug-nonzero-labels will split the CFG in all kinds of crazy
840     // places (i.e. instructions in basic blocks we haven't even begun visiting
841     // yet).  To make our life easier, do this work in a pass after the main
842     // instrumentation.
843     if (ClDebugNonzeroLabels) {
844       for (Value *V : DFSF.NonZeroChecks) {
845         Instruction *Pos;
846         if (Instruction *I = dyn_cast<Instruction>(V))
847           Pos = I->getNextNode();
848         else
849           Pos = &DFSF.F->getEntryBlock().front();
850         while (isa<PHINode>(Pos) || isa<AllocaInst>(Pos))
851           Pos = Pos->getNextNode();
852         IRBuilder<> IRB(Pos);
853         Value *Ne = IRB.CreateICmpNE(V, DFSF.DFS.ZeroShadow);
854         BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
855             Ne, Pos, /*Unreachable=*/false, ColdCallWeights));
856         IRBuilder<> ThenIRB(BI);
857         ThenIRB.CreateCall(DFSF.DFS.DFSanNonzeroLabelFn, {});
858       }
859     }
860   }
861 
862   return false;
863 }
864 
getArgTLSPtr()865 Value *DFSanFunction::getArgTLSPtr() {
866   if (ArgTLSPtr)
867     return ArgTLSPtr;
868   if (DFS.ArgTLS)
869     return ArgTLSPtr = DFS.ArgTLS;
870 
871   IRBuilder<> IRB(&F->getEntryBlock().front());
872   return ArgTLSPtr = IRB.CreateCall(DFS.GetArgTLS, {});
873 }
874 
getRetvalTLS()875 Value *DFSanFunction::getRetvalTLS() {
876   if (RetvalTLSPtr)
877     return RetvalTLSPtr;
878   if (DFS.RetvalTLS)
879     return RetvalTLSPtr = DFS.RetvalTLS;
880 
881   IRBuilder<> IRB(&F->getEntryBlock().front());
882   return RetvalTLSPtr = IRB.CreateCall(DFS.GetRetvalTLS, {});
883 }
884 
getArgTLS(unsigned Idx,Instruction * Pos)885 Value *DFSanFunction::getArgTLS(unsigned Idx, Instruction *Pos) {
886   IRBuilder<> IRB(Pos);
887   return IRB.CreateConstGEP2_64(getArgTLSPtr(), 0, Idx);
888 }
889 
getShadow(Value * V)890 Value *DFSanFunction::getShadow(Value *V) {
891   if (!isa<Argument>(V) && !isa<Instruction>(V))
892     return DFS.ZeroShadow;
893   Value *&Shadow = ValShadowMap[V];
894   if (!Shadow) {
895     if (Argument *A = dyn_cast<Argument>(V)) {
896       if (IsNativeABI)
897         return DFS.ZeroShadow;
898       switch (IA) {
899       case DataFlowSanitizer::IA_TLS: {
900         Value *ArgTLSPtr = getArgTLSPtr();
901         Instruction *ArgTLSPos =
902             DFS.ArgTLS ? &*F->getEntryBlock().begin()
903                        : cast<Instruction>(ArgTLSPtr)->getNextNode();
904         IRBuilder<> IRB(ArgTLSPos);
905         Shadow = IRB.CreateLoad(getArgTLS(A->getArgNo(), ArgTLSPos));
906         break;
907       }
908       case DataFlowSanitizer::IA_Args: {
909         unsigned ArgIdx = A->getArgNo() + F->getArgumentList().size() / 2;
910         Function::arg_iterator i = F->arg_begin();
911         while (ArgIdx--)
912           ++i;
913         Shadow = &*i;
914         assert(Shadow->getType() == DFS.ShadowTy);
915         break;
916       }
917       }
918       NonZeroChecks.push_back(Shadow);
919     } else {
920       Shadow = DFS.ZeroShadow;
921     }
922   }
923   return Shadow;
924 }
925 
setShadow(Instruction * I,Value * Shadow)926 void DFSanFunction::setShadow(Instruction *I, Value *Shadow) {
927   assert(!ValShadowMap.count(I));
928   assert(Shadow->getType() == DFS.ShadowTy);
929   ValShadowMap[I] = Shadow;
930 }
931 
getShadowAddress(Value * Addr,Instruction * Pos)932 Value *DataFlowSanitizer::getShadowAddress(Value *Addr, Instruction *Pos) {
933   assert(Addr != RetvalTLS && "Reinstrumenting?");
934   IRBuilder<> IRB(Pos);
935   Value *ShadowPtrMaskValue;
936   if (DFSanRuntimeShadowMask)
937     ShadowPtrMaskValue = IRB.CreateLoad(IntptrTy, ExternalShadowMask);
938   else
939     ShadowPtrMaskValue = ShadowPtrMask;
940   return IRB.CreateIntToPtr(
941       IRB.CreateMul(
942           IRB.CreateAnd(IRB.CreatePtrToInt(Addr, IntptrTy),
943                         IRB.CreatePtrToInt(ShadowPtrMaskValue, IntptrTy)),
944           ShadowPtrMul),
945       ShadowPtrTy);
946 }
947 
948 // Generates IR to compute the union of the two given shadows, inserting it
949 // before Pos.  Returns the computed union Value.
combineShadows(Value * V1,Value * V2,Instruction * Pos)950 Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
951   if (V1 == DFS.ZeroShadow)
952     return V2;
953   if (V2 == DFS.ZeroShadow)
954     return V1;
955   if (V1 == V2)
956     return V1;
957 
958   auto V1Elems = ShadowElements.find(V1);
959   auto V2Elems = ShadowElements.find(V2);
960   if (V1Elems != ShadowElements.end() && V2Elems != ShadowElements.end()) {
961     if (std::includes(V1Elems->second.begin(), V1Elems->second.end(),
962                       V2Elems->second.begin(), V2Elems->second.end())) {
963       return V1;
964     } else if (std::includes(V2Elems->second.begin(), V2Elems->second.end(),
965                              V1Elems->second.begin(), V1Elems->second.end())) {
966       return V2;
967     }
968   } else if (V1Elems != ShadowElements.end()) {
969     if (V1Elems->second.count(V2))
970       return V1;
971   } else if (V2Elems != ShadowElements.end()) {
972     if (V2Elems->second.count(V1))
973       return V2;
974   }
975 
976   auto Key = std::make_pair(V1, V2);
977   if (V1 > V2)
978     std::swap(Key.first, Key.second);
979   CachedCombinedShadow &CCS = CachedCombinedShadows[Key];
980   if (CCS.Block && DT.dominates(CCS.Block, Pos->getParent()))
981     return CCS.Shadow;
982 
983   IRBuilder<> IRB(Pos);
984   if (AvoidNewBlocks) {
985     CallInst *Call = IRB.CreateCall(DFS.DFSanCheckedUnionFn, {V1, V2});
986     Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
987     Call->addAttribute(1, Attribute::ZExt);
988     Call->addAttribute(2, Attribute::ZExt);
989 
990     CCS.Block = Pos->getParent();
991     CCS.Shadow = Call;
992   } else {
993     BasicBlock *Head = Pos->getParent();
994     Value *Ne = IRB.CreateICmpNE(V1, V2);
995     BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
996         Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
997     IRBuilder<> ThenIRB(BI);
998     CallInst *Call = ThenIRB.CreateCall(DFS.DFSanUnionFn, {V1, V2});
999     Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
1000     Call->addAttribute(1, Attribute::ZExt);
1001     Call->addAttribute(2, Attribute::ZExt);
1002 
1003     BasicBlock *Tail = BI->getSuccessor(0);
1004     PHINode *Phi = PHINode::Create(DFS.ShadowTy, 2, "", &Tail->front());
1005     Phi->addIncoming(Call, Call->getParent());
1006     Phi->addIncoming(V1, Head);
1007 
1008     CCS.Block = Tail;
1009     CCS.Shadow = Phi;
1010   }
1011 
1012   std::set<Value *> UnionElems;
1013   if (V1Elems != ShadowElements.end()) {
1014     UnionElems = V1Elems->second;
1015   } else {
1016     UnionElems.insert(V1);
1017   }
1018   if (V2Elems != ShadowElements.end()) {
1019     UnionElems.insert(V2Elems->second.begin(), V2Elems->second.end());
1020   } else {
1021     UnionElems.insert(V2);
1022   }
1023   ShadowElements[CCS.Shadow] = std::move(UnionElems);
1024 
1025   return CCS.Shadow;
1026 }
1027 
1028 // A convenience function which folds the shadows of each of the operands
1029 // of the provided instruction Inst, inserting the IR before Inst.  Returns
1030 // the computed union Value.
combineOperandShadows(Instruction * Inst)1031 Value *DFSanFunction::combineOperandShadows(Instruction *Inst) {
1032   if (Inst->getNumOperands() == 0)
1033     return DFS.ZeroShadow;
1034 
1035   Value *Shadow = getShadow(Inst->getOperand(0));
1036   for (unsigned i = 1, n = Inst->getNumOperands(); i != n; ++i) {
1037     Shadow = combineShadows(Shadow, getShadow(Inst->getOperand(i)), Inst);
1038   }
1039   return Shadow;
1040 }
1041 
visitOperandShadowInst(Instruction & I)1042 void DFSanVisitor::visitOperandShadowInst(Instruction &I) {
1043   Value *CombinedShadow = DFSF.combineOperandShadows(&I);
1044   DFSF.setShadow(&I, CombinedShadow);
1045 }
1046 
1047 // Generates IR to load shadow corresponding to bytes [Addr, Addr+Size), where
1048 // Addr has alignment Align, and take the union of each of those shadows.
loadShadow(Value * Addr,uint64_t Size,uint64_t Align,Instruction * Pos)1049 Value *DFSanFunction::loadShadow(Value *Addr, uint64_t Size, uint64_t Align,
1050                                  Instruction *Pos) {
1051   if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
1052     llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
1053         AllocaShadowMap.find(AI);
1054     if (i != AllocaShadowMap.end()) {
1055       IRBuilder<> IRB(Pos);
1056       return IRB.CreateLoad(i->second);
1057     }
1058   }
1059 
1060   uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
1061   SmallVector<Value *, 2> Objs;
1062   GetUnderlyingObjects(Addr, Objs, Pos->getModule()->getDataLayout());
1063   bool AllConstants = true;
1064   for (Value *Obj : Objs) {
1065     if (isa<Function>(Obj) || isa<BlockAddress>(Obj))
1066       continue;
1067     if (isa<GlobalVariable>(Obj) && cast<GlobalVariable>(Obj)->isConstant())
1068       continue;
1069 
1070     AllConstants = false;
1071     break;
1072   }
1073   if (AllConstants)
1074     return DFS.ZeroShadow;
1075 
1076   Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
1077   switch (Size) {
1078   case 0:
1079     return DFS.ZeroShadow;
1080   case 1: {
1081     LoadInst *LI = new LoadInst(ShadowAddr, "", Pos);
1082     LI->setAlignment(ShadowAlign);
1083     return LI;
1084   }
1085   case 2: {
1086     IRBuilder<> IRB(Pos);
1087     Value *ShadowAddr1 = IRB.CreateGEP(DFS.ShadowTy, ShadowAddr,
1088                                        ConstantInt::get(DFS.IntptrTy, 1));
1089     return combineShadows(IRB.CreateAlignedLoad(ShadowAddr, ShadowAlign),
1090                           IRB.CreateAlignedLoad(ShadowAddr1, ShadowAlign), Pos);
1091   }
1092   }
1093   if (!AvoidNewBlocks && Size % (64 / DFS.ShadowWidth) == 0) {
1094     // Fast path for the common case where each byte has identical shadow: load
1095     // shadow 64 bits at a time, fall out to a __dfsan_union_load call if any
1096     // shadow is non-equal.
1097     BasicBlock *FallbackBB = BasicBlock::Create(*DFS.Ctx, "", F);
1098     IRBuilder<> FallbackIRB(FallbackBB);
1099     CallInst *FallbackCall = FallbackIRB.CreateCall(
1100         DFS.DFSanUnionLoadFn,
1101         {ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size)});
1102     FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
1103 
1104     // Compare each of the shadows stored in the loaded 64 bits to each other,
1105     // by computing (WideShadow rotl ShadowWidth) == WideShadow.
1106     IRBuilder<> IRB(Pos);
1107     Value *WideAddr =
1108         IRB.CreateBitCast(ShadowAddr, Type::getInt64PtrTy(*DFS.Ctx));
1109     Value *WideShadow = IRB.CreateAlignedLoad(WideAddr, ShadowAlign);
1110     Value *TruncShadow = IRB.CreateTrunc(WideShadow, DFS.ShadowTy);
1111     Value *ShlShadow = IRB.CreateShl(WideShadow, DFS.ShadowWidth);
1112     Value *ShrShadow = IRB.CreateLShr(WideShadow, 64 - DFS.ShadowWidth);
1113     Value *RotShadow = IRB.CreateOr(ShlShadow, ShrShadow);
1114     Value *ShadowsEq = IRB.CreateICmpEQ(WideShadow, RotShadow);
1115 
1116     BasicBlock *Head = Pos->getParent();
1117     BasicBlock *Tail = Head->splitBasicBlock(Pos->getIterator());
1118 
1119     if (DomTreeNode *OldNode = DT.getNode(Head)) {
1120       std::vector<DomTreeNode *> Children(OldNode->begin(), OldNode->end());
1121 
1122       DomTreeNode *NewNode = DT.addNewBlock(Tail, Head);
1123       for (auto Child : Children)
1124         DT.changeImmediateDominator(Child, NewNode);
1125     }
1126 
1127     // In the following code LastBr will refer to the previous basic block's
1128     // conditional branch instruction, whose true successor is fixed up to point
1129     // to the next block during the loop below or to the tail after the final
1130     // iteration.
1131     BranchInst *LastBr = BranchInst::Create(FallbackBB, FallbackBB, ShadowsEq);
1132     ReplaceInstWithInst(Head->getTerminator(), LastBr);
1133     DT.addNewBlock(FallbackBB, Head);
1134 
1135     for (uint64_t Ofs = 64 / DFS.ShadowWidth; Ofs != Size;
1136          Ofs += 64 / DFS.ShadowWidth) {
1137       BasicBlock *NextBB = BasicBlock::Create(*DFS.Ctx, "", F);
1138       DT.addNewBlock(NextBB, LastBr->getParent());
1139       IRBuilder<> NextIRB(NextBB);
1140       WideAddr = NextIRB.CreateGEP(Type::getInt64Ty(*DFS.Ctx), WideAddr,
1141                                    ConstantInt::get(DFS.IntptrTy, 1));
1142       Value *NextWideShadow = NextIRB.CreateAlignedLoad(WideAddr, ShadowAlign);
1143       ShadowsEq = NextIRB.CreateICmpEQ(WideShadow, NextWideShadow);
1144       LastBr->setSuccessor(0, NextBB);
1145       LastBr = NextIRB.CreateCondBr(ShadowsEq, FallbackBB, FallbackBB);
1146     }
1147 
1148     LastBr->setSuccessor(0, Tail);
1149     FallbackIRB.CreateBr(Tail);
1150     PHINode *Shadow = PHINode::Create(DFS.ShadowTy, 2, "", &Tail->front());
1151     Shadow->addIncoming(FallbackCall, FallbackBB);
1152     Shadow->addIncoming(TruncShadow, LastBr->getParent());
1153     return Shadow;
1154   }
1155 
1156   IRBuilder<> IRB(Pos);
1157   CallInst *FallbackCall = IRB.CreateCall(
1158       DFS.DFSanUnionLoadFn, {ShadowAddr, ConstantInt::get(DFS.IntptrTy, Size)});
1159   FallbackCall->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
1160   return FallbackCall;
1161 }
1162 
visitLoadInst(LoadInst & LI)1163 void DFSanVisitor::visitLoadInst(LoadInst &LI) {
1164   auto &DL = LI.getModule()->getDataLayout();
1165   uint64_t Size = DL.getTypeStoreSize(LI.getType());
1166   if (Size == 0) {
1167     DFSF.setShadow(&LI, DFSF.DFS.ZeroShadow);
1168     return;
1169   }
1170 
1171   uint64_t Align;
1172   if (ClPreserveAlignment) {
1173     Align = LI.getAlignment();
1174     if (Align == 0)
1175       Align = DL.getABITypeAlignment(LI.getType());
1176   } else {
1177     Align = 1;
1178   }
1179   IRBuilder<> IRB(&LI);
1180   Value *Shadow = DFSF.loadShadow(LI.getPointerOperand(), Size, Align, &LI);
1181   if (ClCombinePointerLabelsOnLoad) {
1182     Value *PtrShadow = DFSF.getShadow(LI.getPointerOperand());
1183     Shadow = DFSF.combineShadows(Shadow, PtrShadow, &LI);
1184   }
1185   if (Shadow != DFSF.DFS.ZeroShadow)
1186     DFSF.NonZeroChecks.push_back(Shadow);
1187 
1188   DFSF.setShadow(&LI, Shadow);
1189 }
1190 
storeShadow(Value * Addr,uint64_t Size,uint64_t Align,Value * Shadow,Instruction * Pos)1191 void DFSanFunction::storeShadow(Value *Addr, uint64_t Size, uint64_t Align,
1192                                 Value *Shadow, Instruction *Pos) {
1193   if (AllocaInst *AI = dyn_cast<AllocaInst>(Addr)) {
1194     llvm::DenseMap<AllocaInst *, AllocaInst *>::iterator i =
1195         AllocaShadowMap.find(AI);
1196     if (i != AllocaShadowMap.end()) {
1197       IRBuilder<> IRB(Pos);
1198       IRB.CreateStore(Shadow, i->second);
1199       return;
1200     }
1201   }
1202 
1203   uint64_t ShadowAlign = Align * DFS.ShadowWidth / 8;
1204   IRBuilder<> IRB(Pos);
1205   Value *ShadowAddr = DFS.getShadowAddress(Addr, Pos);
1206   if (Shadow == DFS.ZeroShadow) {
1207     IntegerType *ShadowTy = IntegerType::get(*DFS.Ctx, Size * DFS.ShadowWidth);
1208     Value *ExtZeroShadow = ConstantInt::get(ShadowTy, 0);
1209     Value *ExtShadowAddr =
1210         IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowTy));
1211     IRB.CreateAlignedStore(ExtZeroShadow, ExtShadowAddr, ShadowAlign);
1212     return;
1213   }
1214 
1215   const unsigned ShadowVecSize = 128 / DFS.ShadowWidth;
1216   uint64_t Offset = 0;
1217   if (Size >= ShadowVecSize) {
1218     VectorType *ShadowVecTy = VectorType::get(DFS.ShadowTy, ShadowVecSize);
1219     Value *ShadowVec = UndefValue::get(ShadowVecTy);
1220     for (unsigned i = 0; i != ShadowVecSize; ++i) {
1221       ShadowVec = IRB.CreateInsertElement(
1222           ShadowVec, Shadow, ConstantInt::get(Type::getInt32Ty(*DFS.Ctx), i));
1223     }
1224     Value *ShadowVecAddr =
1225         IRB.CreateBitCast(ShadowAddr, PointerType::getUnqual(ShadowVecTy));
1226     do {
1227       Value *CurShadowVecAddr =
1228           IRB.CreateConstGEP1_32(ShadowVecTy, ShadowVecAddr, Offset);
1229       IRB.CreateAlignedStore(ShadowVec, CurShadowVecAddr, ShadowAlign);
1230       Size -= ShadowVecSize;
1231       ++Offset;
1232     } while (Size >= ShadowVecSize);
1233     Offset *= ShadowVecSize;
1234   }
1235   while (Size > 0) {
1236     Value *CurShadowAddr =
1237         IRB.CreateConstGEP1_32(DFS.ShadowTy, ShadowAddr, Offset);
1238     IRB.CreateAlignedStore(Shadow, CurShadowAddr, ShadowAlign);
1239     --Size;
1240     ++Offset;
1241   }
1242 }
1243 
visitStoreInst(StoreInst & SI)1244 void DFSanVisitor::visitStoreInst(StoreInst &SI) {
1245   auto &DL = SI.getModule()->getDataLayout();
1246   uint64_t Size = DL.getTypeStoreSize(SI.getValueOperand()->getType());
1247   if (Size == 0)
1248     return;
1249 
1250   uint64_t Align;
1251   if (ClPreserveAlignment) {
1252     Align = SI.getAlignment();
1253     if (Align == 0)
1254       Align = DL.getABITypeAlignment(SI.getValueOperand()->getType());
1255   } else {
1256     Align = 1;
1257   }
1258 
1259   Value* Shadow = DFSF.getShadow(SI.getValueOperand());
1260   if (ClCombinePointerLabelsOnStore) {
1261     Value *PtrShadow = DFSF.getShadow(SI.getPointerOperand());
1262     Shadow = DFSF.combineShadows(Shadow, PtrShadow, &SI);
1263   }
1264   DFSF.storeShadow(SI.getPointerOperand(), Size, Align, Shadow, &SI);
1265 }
1266 
visitBinaryOperator(BinaryOperator & BO)1267 void DFSanVisitor::visitBinaryOperator(BinaryOperator &BO) {
1268   visitOperandShadowInst(BO);
1269 }
1270 
visitCastInst(CastInst & CI)1271 void DFSanVisitor::visitCastInst(CastInst &CI) { visitOperandShadowInst(CI); }
1272 
visitCmpInst(CmpInst & CI)1273 void DFSanVisitor::visitCmpInst(CmpInst &CI) { visitOperandShadowInst(CI); }
1274 
visitGetElementPtrInst(GetElementPtrInst & GEPI)1275 void DFSanVisitor::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
1276   visitOperandShadowInst(GEPI);
1277 }
1278 
visitExtractElementInst(ExtractElementInst & I)1279 void DFSanVisitor::visitExtractElementInst(ExtractElementInst &I) {
1280   visitOperandShadowInst(I);
1281 }
1282 
visitInsertElementInst(InsertElementInst & I)1283 void DFSanVisitor::visitInsertElementInst(InsertElementInst &I) {
1284   visitOperandShadowInst(I);
1285 }
1286 
visitShuffleVectorInst(ShuffleVectorInst & I)1287 void DFSanVisitor::visitShuffleVectorInst(ShuffleVectorInst &I) {
1288   visitOperandShadowInst(I);
1289 }
1290 
visitExtractValueInst(ExtractValueInst & I)1291 void DFSanVisitor::visitExtractValueInst(ExtractValueInst &I) {
1292   visitOperandShadowInst(I);
1293 }
1294 
visitInsertValueInst(InsertValueInst & I)1295 void DFSanVisitor::visitInsertValueInst(InsertValueInst &I) {
1296   visitOperandShadowInst(I);
1297 }
1298 
visitAllocaInst(AllocaInst & I)1299 void DFSanVisitor::visitAllocaInst(AllocaInst &I) {
1300   bool AllLoadsStores = true;
1301   for (User *U : I.users()) {
1302     if (isa<LoadInst>(U))
1303       continue;
1304 
1305     if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1306       if (SI->getPointerOperand() == &I)
1307         continue;
1308     }
1309 
1310     AllLoadsStores = false;
1311     break;
1312   }
1313   if (AllLoadsStores) {
1314     IRBuilder<> IRB(&I);
1315     DFSF.AllocaShadowMap[&I] = IRB.CreateAlloca(DFSF.DFS.ShadowTy);
1316   }
1317   DFSF.setShadow(&I, DFSF.DFS.ZeroShadow);
1318 }
1319 
visitSelectInst(SelectInst & I)1320 void DFSanVisitor::visitSelectInst(SelectInst &I) {
1321   Value *CondShadow = DFSF.getShadow(I.getCondition());
1322   Value *TrueShadow = DFSF.getShadow(I.getTrueValue());
1323   Value *FalseShadow = DFSF.getShadow(I.getFalseValue());
1324 
1325   if (isa<VectorType>(I.getCondition()->getType())) {
1326     DFSF.setShadow(
1327         &I,
1328         DFSF.combineShadows(
1329             CondShadow, DFSF.combineShadows(TrueShadow, FalseShadow, &I), &I));
1330   } else {
1331     Value *ShadowSel;
1332     if (TrueShadow == FalseShadow) {
1333       ShadowSel = TrueShadow;
1334     } else {
1335       ShadowSel =
1336           SelectInst::Create(I.getCondition(), TrueShadow, FalseShadow, "", &I);
1337     }
1338     DFSF.setShadow(&I, DFSF.combineShadows(CondShadow, ShadowSel, &I));
1339   }
1340 }
1341 
visitMemSetInst(MemSetInst & I)1342 void DFSanVisitor::visitMemSetInst(MemSetInst &I) {
1343   IRBuilder<> IRB(&I);
1344   Value *ValShadow = DFSF.getShadow(I.getValue());
1345   IRB.CreateCall(DFSF.DFS.DFSanSetLabelFn,
1346                  {ValShadow, IRB.CreateBitCast(I.getDest(), Type::getInt8PtrTy(
1347                                                                 *DFSF.DFS.Ctx)),
1348                   IRB.CreateZExtOrTrunc(I.getLength(), DFSF.DFS.IntptrTy)});
1349 }
1350 
visitMemTransferInst(MemTransferInst & I)1351 void DFSanVisitor::visitMemTransferInst(MemTransferInst &I) {
1352   IRBuilder<> IRB(&I);
1353   Value *DestShadow = DFSF.DFS.getShadowAddress(I.getDest(), &I);
1354   Value *SrcShadow = DFSF.DFS.getShadowAddress(I.getSource(), &I);
1355   Value *LenShadow = IRB.CreateMul(
1356       I.getLength(),
1357       ConstantInt::get(I.getLength()->getType(), DFSF.DFS.ShadowWidth / 8));
1358   Value *AlignShadow;
1359   if (ClPreserveAlignment) {
1360     AlignShadow = IRB.CreateMul(I.getAlignmentCst(),
1361                                 ConstantInt::get(I.getAlignmentCst()->getType(),
1362                                                  DFSF.DFS.ShadowWidth / 8));
1363   } else {
1364     AlignShadow = ConstantInt::get(I.getAlignmentCst()->getType(),
1365                                    DFSF.DFS.ShadowWidth / 8);
1366   }
1367   Type *Int8Ptr = Type::getInt8PtrTy(*DFSF.DFS.Ctx);
1368   DestShadow = IRB.CreateBitCast(DestShadow, Int8Ptr);
1369   SrcShadow = IRB.CreateBitCast(SrcShadow, Int8Ptr);
1370   IRB.CreateCall(I.getCalledValue(), {DestShadow, SrcShadow, LenShadow,
1371                                       AlignShadow, I.getVolatileCst()});
1372 }
1373 
visitReturnInst(ReturnInst & RI)1374 void DFSanVisitor::visitReturnInst(ReturnInst &RI) {
1375   if (!DFSF.IsNativeABI && RI.getReturnValue()) {
1376     switch (DFSF.IA) {
1377     case DataFlowSanitizer::IA_TLS: {
1378       Value *S = DFSF.getShadow(RI.getReturnValue());
1379       IRBuilder<> IRB(&RI);
1380       IRB.CreateStore(S, DFSF.getRetvalTLS());
1381       break;
1382     }
1383     case DataFlowSanitizer::IA_Args: {
1384       IRBuilder<> IRB(&RI);
1385       Type *RT = DFSF.F->getFunctionType()->getReturnType();
1386       Value *InsVal =
1387           IRB.CreateInsertValue(UndefValue::get(RT), RI.getReturnValue(), 0);
1388       Value *InsShadow =
1389           IRB.CreateInsertValue(InsVal, DFSF.getShadow(RI.getReturnValue()), 1);
1390       RI.setOperand(0, InsShadow);
1391       break;
1392     }
1393     }
1394   }
1395 }
1396 
visitCallSite(CallSite CS)1397 void DFSanVisitor::visitCallSite(CallSite CS) {
1398   Function *F = CS.getCalledFunction();
1399   if ((F && F->isIntrinsic()) || isa<InlineAsm>(CS.getCalledValue())) {
1400     visitOperandShadowInst(*CS.getInstruction());
1401     return;
1402   }
1403 
1404   // Calls to this function are synthesized in wrappers, and we shouldn't
1405   // instrument them.
1406   if (F == DFSF.DFS.DFSanVarargWrapperFn)
1407     return;
1408 
1409   IRBuilder<> IRB(CS.getInstruction());
1410 
1411   DenseMap<Value *, Function *>::iterator i =
1412       DFSF.DFS.UnwrappedFnMap.find(CS.getCalledValue());
1413   if (i != DFSF.DFS.UnwrappedFnMap.end()) {
1414     Function *F = i->second;
1415     switch (DFSF.DFS.getWrapperKind(F)) {
1416     case DataFlowSanitizer::WK_Warning: {
1417       CS.setCalledFunction(F);
1418       IRB.CreateCall(DFSF.DFS.DFSanUnimplementedFn,
1419                      IRB.CreateGlobalStringPtr(F->getName()));
1420       DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
1421       return;
1422     }
1423     case DataFlowSanitizer::WK_Discard: {
1424       CS.setCalledFunction(F);
1425       DFSF.setShadow(CS.getInstruction(), DFSF.DFS.ZeroShadow);
1426       return;
1427     }
1428     case DataFlowSanitizer::WK_Functional: {
1429       CS.setCalledFunction(F);
1430       visitOperandShadowInst(*CS.getInstruction());
1431       return;
1432     }
1433     case DataFlowSanitizer::WK_Custom: {
1434       // Don't try to handle invokes of custom functions, it's too complicated.
1435       // Instead, invoke the dfsw$ wrapper, which will in turn call the __dfsw_
1436       // wrapper.
1437       if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction())) {
1438         FunctionType *FT = F->getFunctionType();
1439         FunctionType *CustomFT = DFSF.DFS.getCustomFunctionType(FT);
1440         std::string CustomFName = "__dfsw_";
1441         CustomFName += F->getName();
1442         Constant *CustomF =
1443             DFSF.DFS.Mod->getOrInsertFunction(CustomFName, CustomFT);
1444         if (Function *CustomFn = dyn_cast<Function>(CustomF)) {
1445           CustomFn->copyAttributesFrom(F);
1446 
1447           // Custom functions returning non-void will write to the return label.
1448           if (!FT->getReturnType()->isVoidTy()) {
1449             CustomFn->removeAttributes(AttributeSet::FunctionIndex,
1450                                        DFSF.DFS.ReadOnlyNoneAttrs);
1451           }
1452         }
1453 
1454         std::vector<Value *> Args;
1455 
1456         CallSite::arg_iterator i = CS.arg_begin();
1457         for (unsigned n = FT->getNumParams(); n != 0; ++i, --n) {
1458           Type *T = (*i)->getType();
1459           FunctionType *ParamFT;
1460           if (isa<PointerType>(T) &&
1461               (ParamFT = dyn_cast<FunctionType>(
1462                    cast<PointerType>(T)->getElementType()))) {
1463             std::string TName = "dfst";
1464             TName += utostr(FT->getNumParams() - n);
1465             TName += "$";
1466             TName += F->getName();
1467             Constant *T = DFSF.DFS.getOrBuildTrampolineFunction(ParamFT, TName);
1468             Args.push_back(T);
1469             Args.push_back(
1470                 IRB.CreateBitCast(*i, Type::getInt8PtrTy(*DFSF.DFS.Ctx)));
1471           } else {
1472             Args.push_back(*i);
1473           }
1474         }
1475 
1476         i = CS.arg_begin();
1477         for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1478           Args.push_back(DFSF.getShadow(*i));
1479 
1480         if (FT->isVarArg()) {
1481           auto *LabelVATy = ArrayType::get(DFSF.DFS.ShadowTy,
1482                                            CS.arg_size() - FT->getNumParams());
1483           auto *LabelVAAlloca = new AllocaInst(
1484               LabelVATy, "labelva", &DFSF.F->getEntryBlock().front());
1485 
1486           for (unsigned n = 0; i != CS.arg_end(); ++i, ++n) {
1487             auto LabelVAPtr = IRB.CreateStructGEP(LabelVATy, LabelVAAlloca, n);
1488             IRB.CreateStore(DFSF.getShadow(*i), LabelVAPtr);
1489           }
1490 
1491           Args.push_back(IRB.CreateStructGEP(LabelVATy, LabelVAAlloca, 0));
1492         }
1493 
1494         if (!FT->getReturnType()->isVoidTy()) {
1495           if (!DFSF.LabelReturnAlloca) {
1496             DFSF.LabelReturnAlloca =
1497                 new AllocaInst(DFSF.DFS.ShadowTy, "labelreturn",
1498                                &DFSF.F->getEntryBlock().front());
1499           }
1500           Args.push_back(DFSF.LabelReturnAlloca);
1501         }
1502 
1503         for (i = CS.arg_begin() + FT->getNumParams(); i != CS.arg_end(); ++i)
1504           Args.push_back(*i);
1505 
1506         CallInst *CustomCI = IRB.CreateCall(CustomF, Args);
1507         CustomCI->setCallingConv(CI->getCallingConv());
1508         CustomCI->setAttributes(CI->getAttributes());
1509 
1510         if (!FT->getReturnType()->isVoidTy()) {
1511           LoadInst *LabelLoad = IRB.CreateLoad(DFSF.LabelReturnAlloca);
1512           DFSF.setShadow(CustomCI, LabelLoad);
1513         }
1514 
1515         CI->replaceAllUsesWith(CustomCI);
1516         CI->eraseFromParent();
1517         return;
1518       }
1519       break;
1520     }
1521     }
1522   }
1523 
1524   FunctionType *FT = cast<FunctionType>(
1525       CS.getCalledValue()->getType()->getPointerElementType());
1526   if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
1527     for (unsigned i = 0, n = FT->getNumParams(); i != n; ++i) {
1528       IRB.CreateStore(DFSF.getShadow(CS.getArgument(i)),
1529                       DFSF.getArgTLS(i, CS.getInstruction()));
1530     }
1531   }
1532 
1533   Instruction *Next = nullptr;
1534   if (!CS.getType()->isVoidTy()) {
1535     if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
1536       if (II->getNormalDest()->getSinglePredecessor()) {
1537         Next = &II->getNormalDest()->front();
1538       } else {
1539         BasicBlock *NewBB =
1540             SplitEdge(II->getParent(), II->getNormalDest(), &DFSF.DT);
1541         Next = &NewBB->front();
1542       }
1543     } else {
1544       assert(CS->getIterator() != CS->getParent()->end());
1545       Next = CS->getNextNode();
1546     }
1547 
1548     if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_TLS) {
1549       IRBuilder<> NextIRB(Next);
1550       LoadInst *LI = NextIRB.CreateLoad(DFSF.getRetvalTLS());
1551       DFSF.SkipInsts.insert(LI);
1552       DFSF.setShadow(CS.getInstruction(), LI);
1553       DFSF.NonZeroChecks.push_back(LI);
1554     }
1555   }
1556 
1557   // Do all instrumentation for IA_Args down here to defer tampering with the
1558   // CFG in a way that SplitEdge may be able to detect.
1559   if (DFSF.DFS.getInstrumentedABI() == DataFlowSanitizer::IA_Args) {
1560     FunctionType *NewFT = DFSF.DFS.getArgsFunctionType(FT);
1561     Value *Func =
1562         IRB.CreateBitCast(CS.getCalledValue(), PointerType::getUnqual(NewFT));
1563     std::vector<Value *> Args;
1564 
1565     CallSite::arg_iterator i = CS.arg_begin(), e = CS.arg_end();
1566     for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1567       Args.push_back(*i);
1568 
1569     i = CS.arg_begin();
1570     for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
1571       Args.push_back(DFSF.getShadow(*i));
1572 
1573     if (FT->isVarArg()) {
1574       unsigned VarArgSize = CS.arg_size() - FT->getNumParams();
1575       ArrayType *VarArgArrayTy = ArrayType::get(DFSF.DFS.ShadowTy, VarArgSize);
1576       AllocaInst *VarArgShadow =
1577           new AllocaInst(VarArgArrayTy, "", &DFSF.F->getEntryBlock().front());
1578       Args.push_back(IRB.CreateConstGEP2_32(VarArgArrayTy, VarArgShadow, 0, 0));
1579       for (unsigned n = 0; i != e; ++i, ++n) {
1580         IRB.CreateStore(
1581             DFSF.getShadow(*i),
1582             IRB.CreateConstGEP2_32(VarArgArrayTy, VarArgShadow, 0, n));
1583         Args.push_back(*i);
1584       }
1585     }
1586 
1587     CallSite NewCS;
1588     if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
1589       NewCS = IRB.CreateInvoke(Func, II->getNormalDest(), II->getUnwindDest(),
1590                                Args);
1591     } else {
1592       NewCS = IRB.CreateCall(Func, Args);
1593     }
1594     NewCS.setCallingConv(CS.getCallingConv());
1595     NewCS.setAttributes(CS.getAttributes().removeAttributes(
1596         *DFSF.DFS.Ctx, AttributeSet::ReturnIndex,
1597         AttributeFuncs::typeIncompatible(NewCS.getInstruction()->getType())));
1598 
1599     if (Next) {
1600       ExtractValueInst *ExVal =
1601           ExtractValueInst::Create(NewCS.getInstruction(), 0, "", Next);
1602       DFSF.SkipInsts.insert(ExVal);
1603       ExtractValueInst *ExShadow =
1604           ExtractValueInst::Create(NewCS.getInstruction(), 1, "", Next);
1605       DFSF.SkipInsts.insert(ExShadow);
1606       DFSF.setShadow(ExVal, ExShadow);
1607       DFSF.NonZeroChecks.push_back(ExShadow);
1608 
1609       CS.getInstruction()->replaceAllUsesWith(ExVal);
1610     }
1611 
1612     CS.getInstruction()->eraseFromParent();
1613   }
1614 }
1615 
visitPHINode(PHINode & PN)1616 void DFSanVisitor::visitPHINode(PHINode &PN) {
1617   PHINode *ShadowPN =
1618       PHINode::Create(DFSF.DFS.ShadowTy, PN.getNumIncomingValues(), "", &PN);
1619 
1620   // Give the shadow phi node valid predecessors to fool SplitEdge into working.
1621   Value *UndefShadow = UndefValue::get(DFSF.DFS.ShadowTy);
1622   for (PHINode::block_iterator i = PN.block_begin(), e = PN.block_end(); i != e;
1623        ++i) {
1624     ShadowPN->addIncoming(UndefShadow, *i);
1625   }
1626 
1627   DFSF.PHIFixups.push_back(std::make_pair(&PN, ShadowPN));
1628   DFSF.setShadow(&PN, ShadowPN);
1629 }
1630