1 //===- X86Disassembler.h - Disassembler for x86 and x86_64 ------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // The X86 disassembler is a table-driven disassembler for the 16-, 32-, and 11 // 64-bit X86 instruction sets. The main decode sequence for an assembly 12 // instruction in this disassembler is: 13 // 14 // 1. Read the prefix bytes and determine the attributes of the instruction. 15 // These attributes, recorded in enum attributeBits 16 // (X86DisassemblerDecoderCommon.h), form a bitmask. The table CONTEXTS_SYM 17 // provides a mapping from bitmasks to contexts, which are represented by 18 // enum InstructionContext (ibid.). 19 // 20 // 2. Read the opcode, and determine what kind of opcode it is. The 21 // disassembler distinguishes four kinds of opcodes, which are enumerated in 22 // OpcodeType (X86DisassemblerDecoderCommon.h): one-byte (0xnn), two-byte 23 // (0x0f 0xnn), three-byte-38 (0x0f 0x38 0xnn), or three-byte-3a 24 // (0x0f 0x3a 0xnn). Mandatory prefixes are treated as part of the context. 25 // 26 // 3. Depending on the opcode type, look in one of four ClassDecision structures 27 // (X86DisassemblerDecoderCommon.h). Use the opcode class to determine which 28 // OpcodeDecision (ibid.) to look the opcode in. Look up the opcode, to get 29 // a ModRMDecision (ibid.). 30 // 31 // 4. Some instructions, such as escape opcodes or extended opcodes, or even 32 // instructions that have ModRM*Reg / ModRM*Mem forms in LLVM, need the 33 // ModR/M byte to complete decode. The ModRMDecision's type is an entry from 34 // ModRMDecisionType (X86DisassemblerDecoderCommon.h) that indicates if the 35 // ModR/M byte is required and how to interpret it. 36 // 37 // 5. After resolving the ModRMDecision, the disassembler has a unique ID 38 // of type InstrUID (X86DisassemblerDecoderCommon.h). Looking this ID up in 39 // INSTRUCTIONS_SYM yields the name of the instruction and the encodings and 40 // meanings of its operands. 41 // 42 // 6. For each operand, its encoding is an entry from OperandEncoding 43 // (X86DisassemblerDecoderCommon.h) and its type is an entry from 44 // OperandType (ibid.). The encoding indicates how to read it from the 45 // instruction; the type indicates how to interpret the value once it has 46 // been read. For example, a register operand could be stored in the R/M 47 // field of the ModR/M byte, the REG field of the ModR/M byte, or added to 48 // the main opcode. This is orthogonal from its meaning (an GPR or an XMM 49 // register, for instance). Given this information, the operands can be 50 // extracted and interpreted. 51 // 52 // 7. As the last step, the disassembler translates the instruction information 53 // and operands into a format understandable by the client - in this case, an 54 // MCInst for use by the MC infrastructure. 55 // 56 // The disassembler is broken broadly into two parts: the table emitter that 57 // emits the instruction decode tables discussed above during compilation, and 58 // the disassembler itself. The table emitter is documented in more detail in 59 // utils/TableGen/X86DisassemblerEmitter.h. 60 // 61 // X86Disassembler.h contains the public interface for the disassembler, 62 // adhering to the MCDisassembler interface. 63 // X86Disassembler.cpp contains the code responsible for step 7, and for 64 // invoking the decoder to execute steps 1-6. 65 // X86DisassemblerDecoderCommon.h contains the definitions needed by both the 66 // table emitter and the disassembler. 67 // X86DisassemblerDecoder.h contains the public interface of the decoder, 68 // factored out into C for possible use by other projects. 69 // X86DisassemblerDecoder.c contains the source code of the decoder, which is 70 // responsible for steps 1-6. 71 // 72 //===----------------------------------------------------------------------===// 73 74 #ifndef X86DISASSEMBLER_H 75 #define X86DISASSEMBLER_H 76 77 #define INSTRUCTION_SPECIFIER_FIELDS \ 78 const char* name; 79 80 #define INSTRUCTION_IDS \ 81 const InstrUID *instructionIDs; 82 83 #include "X86DisassemblerDecoderCommon.h" 84 85 #undef INSTRUCTION_SPECIFIER_FIELDS 86 #undef INSTRUCTION_IDS 87 88 #include "llvm/MC/MCDisassembler.h" 89 90 struct InternalInstruction; 91 92 namespace llvm { 93 94 class MCInst; 95 class MemoryObject; 96 class raw_ostream; 97 98 struct EDInstInfo; 99 100 namespace X86Disassembler { 101 102 /// X86GenericDisassembler - Generic disassembler for all X86 platforms. 103 /// All each platform class should have to do is subclass the constructor, and 104 /// provide a different disassemblerMode value. 105 class X86GenericDisassembler : public MCDisassembler { 106 protected: 107 /// Constructor - Initializes the disassembler. 108 /// 109 /// @param mode - The X86 architecture mode to decode for. 110 X86GenericDisassembler(DisassemblerMode mode); 111 public: 112 ~X86GenericDisassembler(); 113 114 /// getInstruction - See MCDisassembler. 115 bool getInstruction(MCInst &instr, 116 uint64_t &size, 117 const MemoryObject ®ion, 118 uint64_t address, 119 raw_ostream &vStream) const; 120 121 /// getEDInfo - See MCDisassembler. 122 EDInstInfo *getEDInfo() const; 123 private: 124 DisassemblerMode fMode; 125 }; 126 127 /// X86_16Disassembler - 16-bit X86 disassembler. 128 class X86_16Disassembler : public X86GenericDisassembler { 129 public: 130 X86_16Disassembler() : 131 X86GenericDisassembler(MODE_16BIT) { 132 } 133 }; 134 135 /// X86_16Disassembler - 32-bit X86 disassembler. 136 class X86_32Disassembler : public X86GenericDisassembler { 137 public: 138 X86_32Disassembler() : 139 X86GenericDisassembler(MODE_32BIT) { 140 } 141 }; 142 143 /// X86_16Disassembler - 64-bit X86 disassembler. 144 class X86_64Disassembler : public X86GenericDisassembler { 145 public: 146 X86_64Disassembler() : 147 X86GenericDisassembler(MODE_64BIT) { 148 } 149 }; 150 151 } // namespace X86Disassembler 152 153 } // namespace llvm 154 155 #endif 156
