Coverage Report

Created: 2019-02-21 13:17

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/CodeGen/StackProtector.h
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//===- StackProtector.h - Stack Protector Insertion -------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass inserts stack protectors into functions which need them. A variable
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// with a random value in it is stored onto the stack before the local variables
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// are allocated. Upon exiting the block, the stored value is checked. If it's
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// changed, then there was some sort of violation and the program aborts.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_STACKPROTECTOR_H
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#define LLVM_CODEGEN_STACKPROTECTOR_H
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Triple.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/ValueMap.h"
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#include "llvm/Pass.h"
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namespace llvm {
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class BasicBlock;
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class DominatorTree;
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class Function;
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class Instruction;
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class Module;
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class TargetLoweringBase;
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class TargetMachine;
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class Type;
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class StackProtector : public FunctionPass {
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private:
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  /// A mapping of AllocaInsts to their required SSP layout.
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  using SSPLayoutMap = DenseMap<const AllocaInst *,
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                                MachineFrameInfo::SSPLayoutKind>;
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  const TargetMachine *TM = nullptr;
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  /// TLI - Keep a pointer of a TargetLowering to consult for determining
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  /// target type sizes.
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  const TargetLoweringBase *TLI = nullptr;
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  Triple Trip;
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  Function *F;
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  Module *M;
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  DominatorTree *DT;
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  /// Layout - Mapping of allocations to the required SSPLayoutKind.
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  /// StackProtector analysis will update this map when determining if an
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  /// AllocaInst triggers a stack protector.
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  SSPLayoutMap Layout;
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  /// The minimum size of buffers that will receive stack smashing
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  /// protection when -fstack-protection is used.
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  unsigned SSPBufferSize = 0;
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  /// VisitedPHIs - The set of PHI nodes visited when determining
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  /// if a variable's reference has been taken.  This set
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  /// is maintained to ensure we don't visit the same PHI node multiple
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  /// times.
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  SmallPtrSet<const PHINode *, 16> VisitedPHIs;
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  // A prologue is generated.
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  bool HasPrologue = false;
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  // IR checking code is generated.
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  bool HasIRCheck = false;
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  /// InsertStackProtectors - Insert code into the prologue and epilogue of
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  /// the function.
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  ///
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  ///  - The prologue code loads and stores the stack guard onto the stack.
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  ///  - The epilogue checks the value stored in the prologue against the
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  ///    original value. It calls __stack_chk_fail if they differ.
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  bool InsertStackProtectors();
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  /// CreateFailBB - Create a basic block to jump to when the stack protector
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  /// check fails.
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  BasicBlock *CreateFailBB();
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  /// ContainsProtectableArray - Check whether the type either is an array or
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  /// contains an array of sufficient size so that we need stack protectors
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  /// for it.
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  /// \param [out] IsLarge is set to true if a protectable array is found and
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  /// it is "large" ( >= ssp-buffer-size).  In the case of a structure with
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  /// multiple arrays, this gets set if any of them is large.
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  bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,
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                                bool InStruct = false) const;
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  /// Check whether a stack allocation has its address taken.
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  bool HasAddressTaken(const Instruction *AI);
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  /// RequiresStackProtector - Check whether or not this function needs a
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  /// stack protector based upon the stack protector level.
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  bool RequiresStackProtector();
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public:
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  static char ID; // Pass identification, replacement for typeid.
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  StackProtector() : FunctionPass(ID), SSPBufferSize(8) {
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    initializeStackProtectorPass(*PassRegistry::getPassRegistry());
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  }
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  void getAnalysisUsage(AnalysisUsage &AU) const override;
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  // Return true if StackProtector is supposed to be handled by SelectionDAG.
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  bool shouldEmitSDCheck(const BasicBlock &BB) const;
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  bool runOnFunction(Function &Fn) override;
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  void copyToMachineFrameInfo(MachineFrameInfo &MFI) const;
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};
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} // end namespace llvm
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#endif // LLVM_CODEGEN_STACKPROTECTOR_H