Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- StackProtector.h - Stack Protector Insertion -------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This pass inserts stack protectors into functions which need them. A variable

// with a random value in it is stored onto the stack before the local variables

// are allocated. Upon exiting the block, the stored value is checked. If it's

// changed, then there was some sort of violation and the program aborts.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_STACKPROTECTOR_H

#define LLVM_CODEGEN_STACKPROTECTOR_H

#include "llvm/ADT/SmallPtrSet.h"

#include "llvm/ADT/Triple.h"

#include "llvm/Analysis/DomTreeUpdater.h"

#include "llvm/CodeGen/MachineFrameInfo.h"

#include "llvm/IR/Instructions.h"

#include "llvm/Pass.h"

namespace llvm {

class BasicBlock;

class DominatorTree;

class Function;

class Instruction;

class Module;

class TargetLoweringBase;

class TargetMachine;

class Type;

class StackProtector : public FunctionPass {

private:

  static constexpr unsigned DefaultSSPBufferSize = 8;

  /// A mapping of AllocaInsts to their required SSP layout.

  using SSPLayoutMap = DenseMap<const AllocaInst *,

                                MachineFrameInfo::SSPLayoutKind>;

  const TargetMachine *TM = nullptr;

  /// TLI - Keep a pointer of a TargetLowering to consult for determining

  /// target type sizes.

  const TargetLoweringBase *TLI = nullptr;

  Triple Trip;

  Function *F;

  Module *M;

  std::optional<DomTreeUpdater> DTU;

  /// Layout - Mapping of allocations to the required SSPLayoutKind.

  /// StackProtector analysis will update this map when determining if an

  /// AllocaInst triggers a stack protector.

  SSPLayoutMap Layout;

  /// The minimum size of buffers that will receive stack smashing

  /// protection when -fstack-protection is used.

  unsigned SSPBufferSize = DefaultSSPBufferSize;

  /// VisitedPHIs - The set of PHI nodes visited when determining

  /// if a variable's reference has been taken.  This set

  /// is maintained to ensure we don't visit the same PHI node multiple

  /// times.

  SmallPtrSet<const PHINode *, 16> VisitedPHIs;

  // A prologue is generated.

  bool HasPrologue = false;

  // IR checking code is generated.

  bool HasIRCheck = false;

  /// InsertStackProtectors - Insert code into the prologue and epilogue of

  /// the function.

  ///

  ///  - The prologue code loads and stores the stack guard onto the stack.

  ///  - The epilogue checks the value stored in the prologue against the

  ///    original value. It calls __stack_chk_fail if they differ.

  bool InsertStackProtectors();

  /// CreateFailBB - Create a basic block to jump to when the stack protector

  /// check fails.

  BasicBlock *CreateFailBB();

  /// ContainsProtectableArray - Check whether the type either is an array or

  /// contains an array of sufficient size so that we need stack protectors

  /// for it.

  /// \param [out] IsLarge is set to true if a protectable array is found and

  /// it is "large" ( >= ssp-buffer-size).  In the case of a structure with

  /// multiple arrays, this gets set if any of them is large.

  bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,

                                bool InStruct = false) const;

  /// Check whether a stack allocation has its address taken.

  bool HasAddressTaken(const Instruction *AI, TypeSize AllocSize);

  /// RequiresStackProtector - Check whether or not this function needs a

  /// stack protector based upon the stack protector level.

  bool RequiresStackProtector();

public:

  static char ID; // Pass identification, replacement for typeid.

  StackProtector();

  void getAnalysisUsage(AnalysisUsage &AU) const override;

  // Return true if StackProtector is supposed to be handled by SelectionDAG.

  bool shouldEmitSDCheck(const BasicBlock &BB) const;

  bool runOnFunction(Function &Fn) override;

  void copyToMachineFrameInfo(MachineFrameInfo &MFI) const;

};

} // end namespace llvm

#endif // LLVM_CODEGEN_STACKPROTECTOR_H