Line data    Source code

       1             : //===- StackProtector.h - Stack Protector Insertion -------------*- C++ -*-===//
       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/CodeGen/MachineFrameInfo.h"
      23             : #include "llvm/IR/Instructions.h"
      24             : #include "llvm/IR/ValueMap.h"
      25             : #include "llvm/Pass.h"
      26             : 
      27             : namespace llvm {
      28             : 
      29             : class BasicBlock;
      30             : class DominatorTree;
      31             : class Function;
      32             : class Instruction;
      33             : class Module;
      34             : class TargetLoweringBase;
      35             : class TargetMachine;
      36             : class Type;
      37             : 
      38             : class StackProtector : public FunctionPass {
      39             : private:
      40             :   /// A mapping of AllocaInsts to their required SSP layout.
      41             :   using SSPLayoutMap = DenseMap<const AllocaInst *,
      42             :                                 MachineFrameInfo::SSPLayoutKind>;
      43             : 
      44             :   const TargetMachine *TM = nullptr;
      45             : 
      46             :   /// TLI - Keep a pointer of a TargetLowering to consult for determining
      47             :   /// target type sizes.
      48             :   const TargetLoweringBase *TLI = nullptr;
      49             :   Triple Trip;
      50             : 
      51             :   Function *F;
      52             :   Module *M;
      53             : 
      54             :   DominatorTree *DT;
      55             : 
      56             :   /// Layout - Mapping of allocations to the required SSPLayoutKind.
      57             :   /// StackProtector analysis will update this map when determining if an
      58             :   /// AllocaInst triggers a stack protector.
      59             :   SSPLayoutMap Layout;
      60             : 
      61             :   /// The minimum size of buffers that will receive stack smashing
      62             :   /// protection when -fstack-protection is used.
      63             :   unsigned SSPBufferSize = 0;
      64             : 
      65             :   /// VisitedPHIs - The set of PHI nodes visited when determining
      66             :   /// if a variable's reference has been taken.  This set
      67             :   /// is maintained to ensure we don't visit the same PHI node multiple
      68             :   /// times.
      69             :   SmallPtrSet<const PHINode *, 16> VisitedPHIs;
      70             : 
      71             :   // A prologue is generated.
      72             :   bool HasPrologue = false;
      73             : 
      74             :   // IR checking code is generated.
      75             :   bool HasIRCheck = false;
      76             : 
      77             :   /// InsertStackProtectors - Insert code into the prologue and epilogue of
      78             :   /// the function.
      79             :   ///
      80             :   ///  - The prologue code loads and stores the stack guard onto the stack.
      81             :   ///  - The epilogue checks the value stored in the prologue against the
      82             :   ///    original value. It calls __stack_chk_fail if they differ.
      83             :   bool InsertStackProtectors();
      84             : 
      85             :   /// CreateFailBB - Create a basic block to jump to when the stack protector
      86             :   /// check fails.
      87             :   BasicBlock *CreateFailBB();
      88             : 
      89             :   /// ContainsProtectableArray - Check whether the type either is an array or
      90             :   /// contains an array of sufficient size so that we need stack protectors
      91             :   /// for it.
      92             :   /// \param [out] IsLarge is set to true if a protectable array is found and
      93             :   /// it is "large" ( >= ssp-buffer-size).  In the case of a structure with
      94             :   /// multiple arrays, this gets set if any of them is large.
      95             :   bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,
      96             :                                 bool InStruct = false) const;
      97             : 
      98             :   /// Check whether a stack allocation has its address taken.
      99             :   bool HasAddressTaken(const Instruction *AI);
     100             : 
     101             :   /// RequiresStackProtector - Check whether or not this function needs a
     102             :   /// stack protector based upon the stack protector level.
     103             :   bool RequiresStackProtector();
     104             : 
     105             : public:
     106             :   static char ID; // Pass identification, replacement for typeid.
     107             : 
     108       82371 :   StackProtector() : FunctionPass(ID), SSPBufferSize(8) {
     109       27457 :     initializeStackProtectorPass(*PassRegistry::getPassRegistry());
     110       27457 :   }
     111             : 
     112             :   void getAnalysisUsage(AnalysisUsage &AU) const override;
     113             : 
     114             :   // Return true if StackProtector is supposed to be handled by SelectionDAG.
     115             :   bool shouldEmitSDCheck(const BasicBlock &BB) const;
     116             : 
     117             :   bool runOnFunction(Function &Fn) override;
     118             : 
     119             :   void copyToMachineFrameInfo(MachineFrameInfo &MFI) const;
     120             : };
     121             : 
     122             : } // end namespace llvm
     123             : 
     124             : #endif // LLVM_CODEGEN_STACKPROTECTOR_H