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 uint16_t operands; 79 80#define INSTRUCTION_IDS \ 81 uint16_t instructionIDs; 82 83#include "X86DisassemblerDecoderCommon.h" 84 85#undef INSTRUCTION_SPECIFIER_FIELDS 86#undef INSTRUCTION_IDS 87 88#include "llvm/MC/MCDisassembler.h" 89 90namespace llvm { 91 92class MCInst; 93class MCInstrInfo; 94class MCSubtargetInfo; 95class MemoryObject; 96class raw_ostream; 97 98struct EDInstInfo; 99 100namespace 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. 105class X86GenericDisassembler : public MCDisassembler { 106 const MCInstrInfo *MII; 107public: 108 /// Constructor - Initializes the disassembler. 109 /// 110 /// @param mode - The X86 architecture mode to decode for. 111 X86GenericDisassembler(const MCSubtargetInfo &STI, DisassemblerMode mode, 112 const MCInstrInfo *MII); 113private: 114 ~X86GenericDisassembler(); 115public: 116 117 /// getInstruction - See MCDisassembler. 118 DecodeStatus getInstruction(MCInst &instr, 119 uint64_t &size, 120 const MemoryObject ®ion, 121 uint64_t address, 122 raw_ostream &vStream, 123 raw_ostream &cStream) const; 124 125 /// getEDInfo - See MCDisassembler. 126 const EDInstInfo *getEDInfo() const; 127private: 128 DisassemblerMode fMode; 129}; 130 131} // namespace X86Disassembler 132 133} // namespace llvm 134 135#endif 136