1 //===- llvm/MC/MCDisassembler.h - Disassembler interface --------*- 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_MC_MCDISASSEMBLER_MCDISASSEMBLER_H 10 #define LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H 11 12 #include "llvm/MC/MCDisassembler/MCSymbolizer.h" 13 #include <cstdint> 14 #include <memory> 15 16 namespace llvm { 17 18 template <typename T> class ArrayRef; 19 class StringRef; 20 class MCContext; 21 class MCInst; 22 class MCSubtargetInfo; 23 class raw_ostream; 24 25 /// Superclass for all disassemblers. Consumes a memory region and provides an 26 /// array of assembly instructions. 27 class MCDisassembler { 28 public: 29 /// Ternary decode status. Most backends will just use Fail and 30 /// Success, however some have a concept of an instruction with 31 /// understandable semantics but which is architecturally 32 /// incorrect. An example of this is ARM UNPREDICTABLE instructions 33 /// which are disassemblable but cause undefined behaviour. 34 /// 35 /// Because it makes sense to disassemble these instructions, there 36 /// is a "soft fail" failure mode that indicates the MCInst& is 37 /// valid but architecturally incorrect. 38 /// 39 /// The enum numbers are deliberately chosen such that reduction 40 /// from Success->SoftFail ->Fail can be done with a simple 41 /// bitwise-AND: 42 /// 43 /// LEFT & TOP = | Success Unpredictable Fail 44 /// --------------+----------------------------------- 45 /// Success | Success Unpredictable Fail 46 /// Unpredictable | Unpredictable Unpredictable Fail 47 /// Fail | Fail Fail Fail 48 /// 49 /// An easy way of encoding this is as 0b11, 0b01, 0b00 for 50 /// Success, SoftFail, Fail respectively. 51 enum DecodeStatus { 52 Fail = 0, 53 SoftFail = 1, 54 Success = 3 55 }; 56 57 MCDisassembler(const MCSubtargetInfo &STI, MCContext &Ctx) 58 : Ctx(Ctx), STI(STI) {} 59 60 virtual ~MCDisassembler(); 61 62 /// Returns the disassembly of a single instruction. 63 /// 64 /// \param Instr - An MCInst to populate with the contents of the 65 /// instruction. 66 /// \param Size - A value to populate with the size of the instruction, or 67 /// the number of bytes consumed while attempting to decode 68 /// an invalid instruction. 69 /// \param Address - The address, in the memory space of region, of the first 70 /// byte of the instruction. 71 /// \param Bytes - A reference to the actual bytes of the instruction. 72 /// \param CStream - The stream to print comments and annotations on. 73 /// \return - MCDisassembler::Success if the instruction is valid, 74 /// MCDisassembler::SoftFail if the instruction was 75 /// disassemblable but invalid, 76 /// MCDisassembler::Fail if the instruction was invalid. 77 virtual DecodeStatus getInstruction(MCInst &Instr, uint64_t &Size, 78 ArrayRef<uint8_t> Bytes, uint64_t Address, 79 raw_ostream &CStream) const = 0; 80 81 /// May parse any prelude that precedes instructions after the start of a 82 /// symbol. Needed for some targets, e.g. WebAssembly. 83 /// 84 /// \param Name - The name of the symbol. 85 /// \param Size - The number of bytes consumed. 86 /// \param Address - The address, in the memory space of region, of the first 87 /// byte of the symbol. 88 /// \param Bytes - A reference to the actual bytes at the symbol location. 89 /// \param CStream - The stream to print comments and annotations on. 90 /// \return - MCDisassembler::Success if the bytes are valid, 91 /// MCDisassembler::Fail if the bytes were invalid. 92 virtual DecodeStatus onSymbolStart(StringRef Name, uint64_t &Size, 93 ArrayRef<uint8_t> Bytes, uint64_t Address, 94 raw_ostream &CStream) const; 95 96 private: 97 MCContext &Ctx; 98 99 protected: 100 // Subtarget information, for instruction decoding predicates if required. 101 const MCSubtargetInfo &STI; 102 std::unique_ptr<MCSymbolizer> Symbolizer; 103 104 public: 105 // Helpers around MCSymbolizer 106 bool tryAddingSymbolicOperand(MCInst &Inst, 107 int64_t Value, 108 uint64_t Address, bool IsBranch, 109 uint64_t Offset, uint64_t InstSize) const; 110 111 void tryAddingPcLoadReferenceComment(int64_t Value, uint64_t Address) const; 112 113 /// Set \p Symzer as the current symbolizer. 114 /// This takes ownership of \p Symzer, and deletes the previously set one. 115 void setSymbolizer(std::unique_ptr<MCSymbolizer> Symzer); 116 117 MCContext& getContext() const { return Ctx; } 118 119 const MCSubtargetInfo& getSubtargetInfo() const { return STI; } 120 121 // Marked mutable because we cache it inside the disassembler, rather than 122 // having to pass it around as an argument through all the autogenerated code. 123 mutable raw_ostream *CommentStream = nullptr; 124 }; 125 126 } // end namespace llvm 127 128 #endif // LLVM_MC_MCDISASSEMBLER_MCDISASSEMBLER_H 129