include/llvm/CodeGen/StackProtector.h

   1 //===- StackProtector.h - Stack Protector Insertion -------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This pass inserts stack protectors into functions which need them. A variable
  10 // with a random value in it is stored onto the stack before the local variables
  11 // are allocated. Upon exiting the block, the stored value is checked. If it's
  12 // changed, then there was some sort of violation and the program aborts.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #ifndef LLVM_CODEGEN_STACKPROTECTOR_H
  17 #define LLVM_CODEGEN_STACKPROTECTOR_H
  18
  19 #include "llvm/ADT/SmallPtrSet.h"
  20 #include "llvm/ADT/Triple.h"
  21 #include "llvm/CodeGen/MachineFrameInfo.h"
  22 #include "llvm/IR/Instructions.h"
  23 #include "llvm/IR/ValueMap.h"
  24 #include "llvm/Pass.h"
  25
  26 namespace llvm {
  27
  28 class BasicBlock;
  29 class DominatorTree;
  30 class Function;
  31 class Instruction;
  32 class Module;
  33 class TargetLoweringBase;
  34 class TargetMachine;
  35 class Type;
  36
  37 class StackProtector : public FunctionPass {
  38 private:
  39   /// A mapping of AllocaInsts to their required SSP layout.
  40   using SSPLayoutMap = DenseMap<const AllocaInst *,
  41                                 MachineFrameInfo::SSPLayoutKind>;
  42
  43   const TargetMachine *TM = nullptr;
  44
  45   /// TLI - Keep a pointer of a TargetLowering to consult for determining
  46   /// target type sizes.
  47   const TargetLoweringBase *TLI = nullptr;
  48   Triple Trip;
  49
  50   Function *F;
  51   Module *M;
  52
  53   DominatorTree *DT;
  54
  55   /// Layout - Mapping of allocations to the required SSPLayoutKind.
  56   /// StackProtector analysis will update this map when determining if an
  57   /// AllocaInst triggers a stack protector.
  58   SSPLayoutMap Layout;
  59
  60   /// The minimum size of buffers that will receive stack smashing
  61   /// protection when -fstack-protection is used.
  62   unsigned SSPBufferSize = 0;
  63
  64   /// VisitedPHIs - The set of PHI nodes visited when determining
  65   /// if a variable's reference has been taken.  This set
  66   /// is maintained to ensure we don't visit the same PHI node multiple
  67   /// times.
  68   SmallPtrSet<const PHINode *, 16> VisitedPHIs;
  69
  70   // A prologue is generated.
  71   bool HasPrologue = false;
  72
  73   // IR checking code is generated.
  74   bool HasIRCheck = false;
  75
  76   /// InsertStackProtectors - Insert code into the prologue and epilogue of
  77   /// the function.
  78   ///
  79   ///  - The prologue code loads and stores the stack guard onto the stack.
  80   ///  - The epilogue checks the value stored in the prologue against the
  81   ///    original value. It calls __stack_chk_fail if they differ.
  82   bool InsertStackProtectors();
  83
  84   /// CreateFailBB - Create a basic block to jump to when the stack protector
  85   /// check fails.
  86   BasicBlock *CreateFailBB();
  87
  88   /// ContainsProtectableArray - Check whether the type either is an array or
  89   /// contains an array of sufficient size so that we need stack protectors
  90   /// for it.
  91   /// \param [out] IsLarge is set to true if a protectable array is found and
  92   /// it is "large" ( >= ssp-buffer-size).  In the case of a structure with
  93   /// multiple arrays, this gets set if any of them is large.
  94   bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,
  95                                 bool InStruct = false) const;
  96
  97   /// Check whether a stack allocation has its address taken.
  98   bool HasAddressTaken(const Instruction *AI);
  99
 100   /// RequiresStackProtector - Check whether or not this function needs a
 101   /// stack protector based upon the stack protector level.
 102   bool RequiresStackProtector();
 103
 104 public:
 105   static char ID; // Pass identification, replacement for typeid.
 106
 107   StackProtector() : FunctionPass(ID), SSPBufferSize(8) {
 108     initializeStackProtectorPass(*PassRegistry::getPassRegistry());
 109   }
 110
 111   void getAnalysisUsage(AnalysisUsage &AU) const override;
 112
 113   // Return true if StackProtector is supposed to be handled by SelectionDAG.
 114   bool shouldEmitSDCheck(const BasicBlock &BB) const;
 115
 116   bool runOnFunction(Function &Fn) override;
 117
 118   void copyToMachineFrameInfo(MachineFrameInfo &MFI) const;
 119 };
 120
 121 } // end namespace llvm
 122
 123 #endif // LLVM_CODEGEN_STACKPROTECTOR_H