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/Analysis/DomTreeUpdater.h" 20 #include "llvm/CodeGen/MachineFrameInfo.h" 21 #include "llvm/IR/Instructions.h" 22 #include "llvm/Pass.h" 23 #include "llvm/TargetParser/Triple.h" 24 25 namespace llvm { 26 27 class BasicBlock; 28 class Function; 29 class Module; 30 class TargetLoweringBase; 31 class TargetMachine; 32 33 class StackProtector : public FunctionPass { 34 private: 35 static constexpr unsigned DefaultSSPBufferSize = 8; 36 37 /// A mapping of AllocaInsts to their required SSP layout. 38 using SSPLayoutMap = DenseMap<const AllocaInst *, 39 MachineFrameInfo::SSPLayoutKind>; 40 41 const TargetMachine *TM = nullptr; 42 43 /// TLI - Keep a pointer of a TargetLowering to consult for determining 44 /// target type sizes. 45 const TargetLoweringBase *TLI = nullptr; 46 Triple Trip; 47 48 Function *F = nullptr; 49 Module *M = nullptr; 50 51 std::optional<DomTreeUpdater> DTU; 52 53 /// Layout - Mapping of allocations to the required SSPLayoutKind. 54 /// StackProtector analysis will update this map when determining if an 55 /// AllocaInst triggers a stack protector. 56 SSPLayoutMap Layout; 57 58 /// The minimum size of buffers that will receive stack smashing 59 /// protection when -fstack-protection is used. 60 unsigned SSPBufferSize = DefaultSSPBufferSize; 61 62 // A prologue is generated. 63 bool HasPrologue = false; 64 65 // IR checking code is generated. 66 bool HasIRCheck = false; 67 68 /// InsertStackProtectors - Insert code into the prologue and epilogue of 69 /// the function. 70 /// 71 /// - The prologue code loads and stores the stack guard onto the stack. 72 /// - The epilogue checks the value stored in the prologue against the 73 /// original value. It calls __stack_chk_fail if they differ. 74 bool InsertStackProtectors(); 75 76 /// CreateFailBB - Create a basic block to jump to when the stack protector 77 /// check fails. 78 BasicBlock *CreateFailBB(); 79 80 public: 81 static char ID; // Pass identification, replacement for typeid. 82 83 StackProtector(); 84 85 void getAnalysisUsage(AnalysisUsage &AU) const override; 86 87 // Return true if StackProtector is supposed to be handled by SelectionDAG. 88 bool shouldEmitSDCheck(const BasicBlock &BB) const; 89 90 bool runOnFunction(Function &Fn) override; 91 92 void copyToMachineFrameInfo(MachineFrameInfo &MFI) const; 93 94 /// Check whether or not \p F needs a stack protector based upon the stack 95 /// protector level. 96 static bool requiresStackProtector(Function *F, SSPLayoutMap *Layout = nullptr); 97 98 }; 99 100 } // end namespace llvm 101 102 #endif // LLVM_CODEGEN_STACKPROTECTOR_H 103