1 //===- X86ModRMFilters.h - Disassembler ModR/M filterss ---------*- 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 // This file is part of the X86 Disassembler Emitter. 11 // It contains ModR/M filters that determine which values of the ModR/M byte 12 // are valid for a partiuclar instruction. 13 // Documentation for the disassembler emitter in general can be found in 14 // X86DisasemblerEmitter.h. 15 // 16 //===----------------------------------------------------------------------===// 17 18 #ifndef X86MODRMFILTERS_H 19 #define X86MODRMFILTERS_H 20 21 #include "llvm/Support/DataTypes.h" 22 23 namespace llvm { 24 25 namespace X86Disassembler { 26 27 /// ModRMFilter - Abstract base class for clases that recognize patterns in 28 /// ModR/M bytes. 29 class ModRMFilter { 30 virtual void anchor(); 31 public: 32 /// Destructor - Override as necessary. ~ModRMFilter()33 virtual ~ModRMFilter() { } 34 35 /// isDumb - Indicates whether this filter returns the same value for 36 /// any value of the ModR/M byte. 37 /// 38 /// @result - True if the filter returns the same value for any ModR/M 39 /// byte; false if not. isDumb()40 virtual bool isDumb() const { return false; } 41 42 /// accepts - Indicates whether the filter accepts a particular ModR/M 43 /// byte value. 44 /// 45 /// @result - True if the filter accepts the ModR/M byte; false if not. 46 virtual bool accepts(uint8_t modRM) const = 0; 47 }; 48 49 /// DumbFilter - Accepts any ModR/M byte. Used for instructions that do not 50 /// require a ModR/M byte or instructions where the entire ModR/M byte is used 51 /// for operands. 52 class DumbFilter : public ModRMFilter { 53 void anchor() override; 54 public: isDumb()55 bool isDumb() const override { 56 return true; 57 } 58 accepts(uint8_t modRM)59 bool accepts(uint8_t modRM) const override { 60 return true; 61 } 62 }; 63 64 /// ModFilter - Filters based on the mod bits [bits 7-6] of the ModR/M byte. 65 /// Some instructions are classified based on whether they are 11 or anything 66 /// else. This filter performs that classification. 67 class ModFilter : public ModRMFilter { 68 void anchor() override; 69 bool R; 70 public: 71 /// Constructor 72 /// 73 /// \param r True if the mod bits of the ModR/M byte must be 11; false 74 /// otherwise. The name r derives from the fact that the mod 75 /// bits indicate whether the R/M bits [bits 2-0] signify a 76 /// register or a memory operand. ModFilter(bool r)77 ModFilter(bool r) : 78 ModRMFilter(), 79 R(r) { 80 } 81 accepts(uint8_t modRM)82 bool accepts(uint8_t modRM) const override { 83 return (R == ((modRM & 0xc0) == 0xc0)); 84 } 85 }; 86 87 /// ExtendedFilter - Extended opcodes are classified based on the value of the 88 /// mod field [bits 7-6] and the value of the nnn field [bits 5-3]. 89 class ExtendedFilter : public ModRMFilter { 90 void anchor() override; 91 bool R; 92 uint8_t NNN; 93 public: 94 /// Constructor 95 /// 96 /// \param r True if the mod field must be set to 11; false otherwise. 97 /// The name is explained at ModFilter. 98 /// \param nnn The required value of the nnn field. ExtendedFilter(bool r,uint8_t nnn)99 ExtendedFilter(bool r, uint8_t nnn) : 100 ModRMFilter(), 101 R(r), 102 NNN(nnn) { 103 } 104 accepts(uint8_t modRM)105 bool accepts(uint8_t modRM) const override { 106 return (((R && ((modRM & 0xc0) == 0xc0)) || 107 (!R && ((modRM & 0xc0) != 0xc0))) && 108 (((modRM & 0x38) >> 3) == NNN)); 109 } 110 }; 111 112 /// ExactFilter - The occasional extended opcode (such as VMCALL or MONITOR) 113 /// requires the ModR/M byte to have a specific value. 114 class ExactFilter : public ModRMFilter { 115 void anchor() override; 116 uint8_t ModRM; 117 public: 118 /// Constructor 119 /// 120 /// \param modRM The required value of the full ModR/M byte. ExactFilter(uint8_t modRM)121 ExactFilter(uint8_t modRM) : 122 ModRMFilter(), 123 ModRM(modRM) { 124 } 125 accepts(uint8_t modRM)126 bool accepts(uint8_t modRM) const override { 127 return (ModRM == modRM); 128 } 129 }; 130 131 } // namespace X86Disassembler 132 133 } // namespace llvm 134 135 #endif 136