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StackProtector.h
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1 //===-- StackProtector.h - Stack Protector Insertion ----------------------===//
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 //
10 // This pass inserts stack protectors into functions which need them. A variable
11 // with a random value in it is stored onto the stack before the local variables
12 // are allocated. Upon exiting the block, the stored value is checked. If it's
13 // changed, then there was some sort of violation and the program aborts.
14 //
15 //===----------------------------------------------------------------------===//
16 
17 #ifndef LLVM_CODEGEN_STACKPROTECTOR_H
18 #define LLVM_CODEGEN_STACKPROTECTOR_H
19 
20 #include "llvm/ADT/SmallPtrSet.h"
21 #include "llvm/ADT/Triple.h"
22 #include "llvm/ADT/ValueMap.h"
23 #include "llvm/Pass.h"
25 
26 namespace llvm {
27 class DominatorTree;
28 class Function;
29 class Module;
30 class PHINode;
31 
32 class StackProtector : public FunctionPass {
33 public:
34  /// SSPLayoutKind. Stack Smashing Protection (SSP) rules require that
35  /// vulnerable stack allocations are located close the stack protector.
37  SSPLK_None, ///< Did not trigger a stack protector. No effect on data
38  ///< layout.
39  SSPLK_LargeArray, ///< Array or nested array >= SSP-buffer-size. Closest
40  ///< to the stack protector.
41  SSPLK_SmallArray, ///< Array or nested array < SSP-buffer-size. 2nd closest
42  ///< to the stack protector.
43  SSPLK_AddrOf ///< The address of this allocation is exposed and
44  ///< triggered protection. 3rd closest to the protector.
45  };
46 
47  /// A mapping of AllocaInsts to their required SSP layout.
49 
50 private:
51  const TargetMachine *TM;
52 
53  /// TLI - Keep a pointer of a TargetLowering to consult for determining
54  /// target type sizes.
55  const TargetLoweringBase *TLI;
56  const Triple Trip;
57 
58  Function *F;
59  Module *M;
60 
61  DominatorTree *DT;
62 
63  /// Layout - Mapping of allocations to the required SSPLayoutKind.
64  /// StackProtector analysis will update this map when determining if an
65  /// AllocaInst triggers a stack protector.
66  SSPLayoutMap Layout;
67 
68  /// \brief The minimum size of buffers that will receive stack smashing
69  /// protection when -fstack-protection is used.
70  unsigned SSPBufferSize;
71 
72  /// VisitedPHIs - The set of PHI nodes visited when determining
73  /// if a variable's reference has been taken. This set
74  /// is maintained to ensure we don't visit the same PHI node multiple
75  /// times.
77 
78  /// InsertStackProtectors - Insert code into the prologue and epilogue of
79  /// the function.
80  ///
81  /// - The prologue code loads and stores the stack guard onto the stack.
82  /// - The epilogue checks the value stored in the prologue against the
83  /// original value. It calls __stack_chk_fail if they differ.
84  bool InsertStackProtectors();
85 
86  /// CreateFailBB - Create a basic block to jump to when the stack protector
87  /// check fails.
88  BasicBlock *CreateFailBB();
89 
90  /// ContainsProtectableArray - Check whether the type either is an array or
91  /// contains an array of sufficient size so that we need stack protectors
92  /// for it.
93  /// \param [out] IsLarge is set to true if a protectable array is found and
94  /// it is "large" ( >= ssp-buffer-size). In the case of a structure with
95  /// multiple arrays, this gets set if any of them is large.
96  bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,
97  bool InStruct = false) const;
98 
99  /// \brief Check whether a stack allocation has its address taken.
100  bool HasAddressTaken(const Instruction *AI);
101 
102  /// RequiresStackProtector - Check whether or not this function needs a
103  /// stack protector based upon the stack protector level.
104  bool RequiresStackProtector();
105 
106 public:
107  static char ID; // Pass identification, replacement for typeid.
108  StackProtector() : FunctionPass(ID), TM(0), TLI(0), SSPBufferSize(0) {
110  }
112  : FunctionPass(ID), TM(TM), TLI(0), Trip(TM->getTargetTriple()),
113  SSPBufferSize(8) {
115  }
116 
117  virtual void getAnalysisUsage(AnalysisUsage &AU) const {
119  }
120 
121  SSPLayoutKind getSSPLayout(const AllocaInst *AI) const;
122 
123  virtual bool runOnFunction(Function &Fn);
124 };
125 } // end namespace llvm
126 
127 #endif // LLVM_CODEGEN_STACKPROTECTOR_H
virtual bool runOnFunction(Function &Fn)
AnalysisUsage & addPreserved()
static PassRegistry * getPassRegistry()
The main container class for the LLVM Intermediate Representation.
Definition: Module.h:112
LLVM Basic Block Representation.
Definition: BasicBlock.h:72
SSPLayoutKind getSSPLayout(const AllocaInst *AI) const
void initializeStackProtectorPass(PassRegistry &)
ValueMap< const AllocaInst *, SSPLayoutKind > SSPLayoutMap
A mapping of AllocaInsts to their required SSP layout.
virtual void getAnalysisUsage(AnalysisUsage &AU) const
StackProtector(const TargetMachine *TM)