1 //===- FileAnalysis.h -------------------------------------------*- 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 #ifndef LLVM_CFI_VERIFY_FILE_ANALYSIS_H 10 #define LLVM_CFI_VERIFY_FILE_ANALYSIS_H 11 12 #include "llvm/ADT/DenseMap.h" 13 #include "llvm/ADT/SmallSet.h" 14 #include "llvm/BinaryFormat/ELF.h" 15 #include "llvm/DebugInfo/Symbolize/Symbolize.h" 16 #include "llvm/MC/MCAsmInfo.h" 17 #include "llvm/MC/MCContext.h" 18 #include "llvm/MC/MCDisassembler/MCDisassembler.h" 19 #include "llvm/MC/MCInst.h" 20 #include "llvm/MC/MCInstPrinter.h" 21 #include "llvm/MC/MCInstrAnalysis.h" 22 #include "llvm/MC/MCInstrDesc.h" 23 #include "llvm/MC/MCInstrInfo.h" 24 #include "llvm/MC/MCObjectFileInfo.h" 25 #include "llvm/MC/MCRegisterInfo.h" 26 #include "llvm/MC/MCSubtargetInfo.h" 27 #include "llvm/MC/TargetRegistry.h" 28 #include "llvm/Object/Binary.h" 29 #include "llvm/Object/COFF.h" 30 #include "llvm/Object/ELFObjectFile.h" 31 #include "llvm/Object/ObjectFile.h" 32 #include "llvm/Support/Casting.h" 33 #include "llvm/Support/CommandLine.h" 34 #include "llvm/Support/Error.h" 35 #include "llvm/Support/MemoryBuffer.h" 36 #include "llvm/Support/TargetSelect.h" 37 #include "llvm/Support/raw_ostream.h" 38 39 #include <functional> 40 #include <set> 41 #include <string> 42 43 namespace llvm { 44 namespace cfi_verify { 45 46 struct GraphResult; 47 48 extern bool IgnoreDWARFFlag; 49 50 enum class CFIProtectionStatus { 51 // This instruction is protected by CFI. 52 PROTECTED, 53 // The instruction is not an indirect control flow instruction, and thus 54 // shouldn't be protected. 55 FAIL_NOT_INDIRECT_CF, 56 // There is a path to the instruction that was unexpected. 57 FAIL_ORPHANS, 58 // There is a path to the instruction from a conditional branch that does not 59 // properly check the destination for this vcall/icall. 60 FAIL_BAD_CONDITIONAL_BRANCH, 61 // One of the operands of the indirect CF instruction is modified between the 62 // CFI-check and execution. 63 FAIL_REGISTER_CLOBBERED, 64 // The instruction referenced does not exist. This normally indicates an 65 // error in the program, where you try and validate a graph that was created 66 // in a different FileAnalysis object. 67 FAIL_INVALID_INSTRUCTION, 68 }; 69 70 StringRef stringCFIProtectionStatus(CFIProtectionStatus Status); 71 72 // Disassembler and analysis tool for machine code files. Keeps track of non- 73 // sequential control flows, including indirect control flow instructions. 74 class FileAnalysis { 75 public: 76 // A metadata struct for an instruction. 77 struct Instr { 78 uint64_t VMAddress; // Virtual memory address of this instruction. 79 MCInst Instruction; // Instruction. 80 uint64_t InstructionSize; // Size of this instruction. 81 bool Valid; // Is this a valid instruction? If false, Instr::Instruction is 82 // undefined. 83 }; 84 85 // Construct a FileAnalysis from a file path. 86 static Expected<FileAnalysis> Create(StringRef Filename); 87 88 // Construct and take ownership of the supplied object. Do not use this 89 // constructor, prefer to use FileAnalysis::Create instead. 90 FileAnalysis(object::OwningBinary<object::Binary> Binary); 91 FileAnalysis() = delete; 92 FileAnalysis(const FileAnalysis &) = delete; 93 FileAnalysis(FileAnalysis &&Other) = default; 94 95 // Returns the instruction at the provided address. Returns nullptr if there 96 // is no instruction at the provided address. 97 const Instr *getInstruction(uint64_t Address) const; 98 99 // Returns the instruction at the provided adress, dying if the instruction is 100 // not found. 101 const Instr &getInstructionOrDie(uint64_t Address) const; 102 103 // Returns a pointer to the previous/next instruction in sequence, 104 // respectively. Returns nullptr if the next/prev instruction doesn't exist, 105 // or if the provided instruction doesn't exist. 106 const Instr *getPrevInstructionSequential(const Instr &InstrMeta) const; 107 const Instr *getNextInstructionSequential(const Instr &InstrMeta) const; 108 109 // Returns whether this instruction is used by CFI to trap the program. 110 bool isCFITrap(const Instr &InstrMeta) const; 111 112 // Returns whether this instruction is a call to a function that will trap on 113 // CFI violations (i.e., it serves as a trap in this instance). 114 bool willTrapOnCFIViolation(const Instr &InstrMeta) const; 115 116 // Returns whether this function can fall through to the next instruction. 117 // Undefined (and bad) instructions cannot fall through, and instruction that 118 // modify the control flow can only fall through if they are conditional 119 // branches or calls. 120 bool canFallThrough(const Instr &InstrMeta) const; 121 122 // Returns the definitive next instruction. This is different from the next 123 // instruction sequentially as it will follow unconditional branches (assuming 124 // they can be resolved at compile time, i.e. not indirect). This method 125 // returns nullptr if the provided instruction does not transfer control flow 126 // to exactly one instruction that is known deterministically at compile time. 127 // Also returns nullptr if the deterministic target does not exist in this 128 // file. 129 const Instr *getDefiniteNextInstruction(const Instr &InstrMeta) const; 130 131 // Get a list of deterministic control flows that lead to the provided 132 // instruction. This list includes all static control flow cross-references as 133 // well as the previous instruction if it can fall through. 134 std::set<const Instr *> 135 getDirectControlFlowXRefs(const Instr &InstrMeta) const; 136 137 // Returns whether this instruction uses a register operand. 138 bool usesRegisterOperand(const Instr &InstrMeta) const; 139 140 // Returns the list of indirect instructions. 141 const std::set<object::SectionedAddress> &getIndirectInstructions() const; 142 143 const MCRegisterInfo *getRegisterInfo() const; 144 const MCInstrInfo *getMCInstrInfo() const; 145 const MCInstrAnalysis *getMCInstrAnalysis() const; 146 147 // Returns the inlining information for the provided address. 148 Expected<DIInliningInfo> 149 symbolizeInlinedCode(object::SectionedAddress Address); 150 151 // Returns whether the provided Graph represents a protected indirect control 152 // flow instruction in this file. 153 CFIProtectionStatus validateCFIProtection(const GraphResult &Graph) const; 154 155 // Returns the first place the operand register is clobbered between the CFI- 156 // check and the indirect CF instruction execution. We do this by walking 157 // backwards from the indirect CF and ensuring there is at most one load 158 // involving the operand register (which is the indirect CF itself on x86). 159 // If the register is not modified, returns the address of the indirect CF 160 // instruction. The result is undefined if the provided graph does not fall 161 // under either the FAIL_REGISTER_CLOBBERED or PROTECTED status (see 162 // CFIProtectionStatus). 163 uint64_t indirectCFOperandClobber(const GraphResult& Graph) const; 164 165 // Prints an instruction to the provided stream using this object's pretty- 166 // printers. 167 void printInstruction(const Instr &InstrMeta, raw_ostream &OS) const; 168 169 protected: 170 // Construct a blank object with the provided triple and features. Used in 171 // testing, where a sub class will dependency inject protected methods to 172 // allow analysis of raw binary, without requiring a fully valid ELF file. 173 FileAnalysis(const Triple &ObjectTriple, const SubtargetFeatures &Features); 174 175 // Add an instruction to this object. 176 void addInstruction(const Instr &Instruction); 177 178 // Disassemble and parse the provided bytes into this object. Instruction 179 // address calculation is done relative to the provided SectionAddress. 180 void parseSectionContents(ArrayRef<uint8_t> SectionBytes, 181 object::SectionedAddress Address); 182 183 // Constructs and initialises members required for disassembly. 184 Error initialiseDisassemblyMembers(); 185 186 // Parses code sections from the internal object file. Saves them into the 187 // internal members. Should only be called once by Create(). 188 Error parseCodeSections(); 189 190 // Parses the symbol table to look for the addresses of functions that will 191 // trap on CFI violations. 192 Error parseSymbolTable(); 193 194 private: 195 // Members that describe the input file. 196 object::OwningBinary<object::Binary> Binary; 197 const object::ObjectFile *Object = nullptr; 198 Triple ObjectTriple; 199 std::string ArchName; 200 std::string MCPU; 201 const Target *ObjectTarget = nullptr; 202 SubtargetFeatures Features; 203 204 // Members required for disassembly. 205 std::unique_ptr<const MCRegisterInfo> RegisterInfo; 206 std::unique_ptr<const MCAsmInfo> AsmInfo; 207 std::unique_ptr<MCSubtargetInfo> SubtargetInfo; 208 std::unique_ptr<const MCInstrInfo> MII; 209 std::unique_ptr<MCContext> Context; 210 std::unique_ptr<const MCDisassembler> Disassembler; 211 std::unique_ptr<const MCInstrAnalysis> MIA; 212 std::unique_ptr<MCInstPrinter> Printer; 213 214 // Symbolizer used for debug information parsing. 215 std::unique_ptr<symbolize::LLVMSymbolizer> Symbolizer; 216 217 // A mapping between the virtual memory address to the instruction metadata 218 // struct. TODO(hctim): Reimplement this as a sorted vector to avoid per- 219 // insertion allocation. 220 std::map<uint64_t, Instr> Instructions; 221 222 // Contains a mapping between a specific address, and a list of instructions 223 // that use this address as a branch target (including call instructions). 224 DenseMap<uint64_t, std::vector<uint64_t>> StaticBranchTargetings; 225 226 // A list of addresses of indirect control flow instructions. 227 std::set<object::SectionedAddress> IndirectInstructions; 228 229 // The addresses of functions that will trap on CFI violations. 230 SmallSet<uint64_t, 4> TrapOnFailFunctionAddresses; 231 }; 232 233 class UnsupportedDisassembly : public ErrorInfo<UnsupportedDisassembly> { 234 public: 235 static char ID; 236 std::string Text; 237 238 UnsupportedDisassembly(StringRef Text); 239 240 void log(raw_ostream &OS) const override; 241 std::error_code convertToErrorCode() const override; 242 }; 243 244 } // namespace cfi_verify 245 } // namespace llvm 246 247 #endif // LLVM_CFI_VERIFY_FILE_ANALYSIS_H 248