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14 | pmbaty | 1 | //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===// |
2 | // |
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3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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4 | // See https://llvm.org/LICENSE.txt for license information. |
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5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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6 | // |
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7 | //===----------------------------------------------------------------------===// |
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8 | |||
9 | #ifndef LLVM_MC_MCFIXUP_H |
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10 | #define LLVM_MC_MCFIXUP_H |
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11 | |||
12 | #include "llvm/Support/DataTypes.h" |
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13 | #include "llvm/Support/ErrorHandling.h" |
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14 | #include "llvm/Support/SMLoc.h" |
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15 | #include <cassert> |
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16 | |||
17 | namespace llvm { |
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18 | class MCExpr; |
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19 | |||
20 | /// Extensible enumeration to represent the type of a fixup. |
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21 | enum MCFixupKind { |
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22 | FK_NONE = 0, ///< A no-op fixup. |
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23 | FK_Data_1, ///< A one-byte fixup. |
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24 | FK_Data_2, ///< A two-byte fixup. |
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25 | FK_Data_4, ///< A four-byte fixup. |
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26 | FK_Data_8, ///< A eight-byte fixup. |
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27 | FK_Data_6b, ///< A six-bits fixup. |
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28 | FK_PCRel_1, ///< A one-byte pc relative fixup. |
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29 | FK_PCRel_2, ///< A two-byte pc relative fixup. |
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30 | FK_PCRel_4, ///< A four-byte pc relative fixup. |
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31 | FK_PCRel_8, ///< A eight-byte pc relative fixup. |
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32 | FK_GPRel_1, ///< A one-byte gp relative fixup. |
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33 | FK_GPRel_2, ///< A two-byte gp relative fixup. |
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34 | FK_GPRel_4, ///< A four-byte gp relative fixup. |
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35 | FK_GPRel_8, ///< A eight-byte gp relative fixup. |
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36 | FK_DTPRel_4, ///< A four-byte dtp relative fixup. |
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37 | FK_DTPRel_8, ///< A eight-byte dtp relative fixup. |
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38 | FK_TPRel_4, ///< A four-byte tp relative fixup. |
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39 | FK_TPRel_8, ///< A eight-byte tp relative fixup. |
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40 | FK_SecRel_1, ///< A one-byte section relative fixup. |
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41 | FK_SecRel_2, ///< A two-byte section relative fixup. |
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42 | FK_SecRel_4, ///< A four-byte section relative fixup. |
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43 | FK_SecRel_8, ///< A eight-byte section relative fixup. |
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44 | |||
45 | FirstTargetFixupKind = 128, |
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46 | |||
47 | /// The range [FirstLiteralRelocationKind, MaxTargetFixupKind) is used for |
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48 | /// relocations coming from .reloc directive. Fixup kind |
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49 | /// FirstLiteralRelocationKind+V represents the relocation type with number V. |
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50 | FirstLiteralRelocationKind = 256, |
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51 | |||
52 | /// Set limit to accommodate the highest reloc type in use for all Targets, |
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53 | /// currently R_AARCH64_IRELATIVE at 1032, including room for expansion. |
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54 | MaxFixupKind = FirstLiteralRelocationKind + 1032 + 32, |
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55 | }; |
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56 | |||
57 | /// Encode information on a single operation to perform on a byte |
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58 | /// sequence (e.g., an encoded instruction) which requires assemble- or run- |
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59 | /// time patching. |
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60 | /// |
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61 | /// Fixups are used any time the target instruction encoder needs to represent |
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62 | /// some value in an instruction which is not yet concrete. The encoder will |
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63 | /// encode the instruction assuming the value is 0, and emit a fixup which |
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64 | /// communicates to the assembler backend how it should rewrite the encoded |
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65 | /// value. |
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66 | /// |
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67 | /// During the process of relaxation, the assembler will apply fixups as |
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68 | /// symbolic values become concrete. When relaxation is complete, any remaining |
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69 | /// fixups become relocations in the object file (or errors, if the fixup cannot |
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70 | /// be encoded on the target). |
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71 | class MCFixup { |
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72 | /// The value to put into the fixup location. The exact interpretation of the |
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73 | /// expression is target dependent, usually it will be one of the operands to |
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74 | /// an instruction or an assembler directive. |
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75 | const MCExpr *Value = nullptr; |
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76 | |||
77 | /// The byte index of start of the relocation inside the MCFragment. |
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78 | uint32_t Offset = 0; |
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79 | |||
80 | /// The target dependent kind of fixup item this is. The kind is used to |
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81 | /// determine how the operand value should be encoded into the instruction. |
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82 | MCFixupKind Kind = FK_NONE; |
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83 | |||
84 | /// The source location which gave rise to the fixup, if any. |
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85 | SMLoc Loc; |
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86 | public: |
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87 | static MCFixup create(uint32_t Offset, const MCExpr *Value, |
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88 | MCFixupKind Kind, SMLoc Loc = SMLoc()) { |
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89 | assert(Kind <= MaxFixupKind && "Kind out of range!"); |
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90 | MCFixup FI; |
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91 | FI.Value = Value; |
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92 | FI.Offset = Offset; |
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93 | FI.Kind = Kind; |
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94 | FI.Loc = Loc; |
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95 | return FI; |
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96 | } |
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97 | |||
98 | MCFixupKind getKind() const { return Kind; } |
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99 | |||
100 | unsigned getTargetKind() const { return Kind; } |
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101 | |||
102 | uint32_t getOffset() const { return Offset; } |
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103 | void setOffset(uint32_t Value) { Offset = Value; } |
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104 | |||
105 | const MCExpr *getValue() const { return Value; } |
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106 | |||
107 | /// Return the generic fixup kind for a value with the given size. It |
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108 | /// is an error to pass an unsupported size. |
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109 | static MCFixupKind getKindForSize(unsigned Size, bool IsPCRel) { |
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110 | switch (Size) { |
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111 | default: llvm_unreachable("Invalid generic fixup size!"); |
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112 | case 1: |
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113 | return IsPCRel ? FK_PCRel_1 : FK_Data_1; |
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114 | case 2: |
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115 | return IsPCRel ? FK_PCRel_2 : FK_Data_2; |
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116 | case 4: |
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117 | return IsPCRel ? FK_PCRel_4 : FK_Data_4; |
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118 | case 8: |
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119 | return IsPCRel ? FK_PCRel_8 : FK_Data_8; |
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120 | } |
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121 | } |
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122 | |||
123 | /// Return the generic fixup kind for a value with the given size in bits. |
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124 | /// It is an error to pass an unsupported size. |
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125 | static MCFixupKind getKindForSizeInBits(unsigned Size, bool IsPCRel) { |
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126 | switch (Size) { |
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127 | default: |
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128 | llvm_unreachable("Invalid generic fixup size!"); |
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129 | case 6: |
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130 | assert(!IsPCRel && "Invalid pc-relative fixup size!"); |
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131 | return FK_Data_6b; |
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132 | case 8: |
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133 | return IsPCRel ? FK_PCRel_1 : FK_Data_1; |
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134 | case 16: |
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135 | return IsPCRel ? FK_PCRel_2 : FK_Data_2; |
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136 | case 32: |
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137 | return IsPCRel ? FK_PCRel_4 : FK_Data_4; |
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138 | case 64: |
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139 | return IsPCRel ? FK_PCRel_8 : FK_Data_8; |
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140 | } |
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141 | } |
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142 | |||
143 | SMLoc getLoc() const { return Loc; } |
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144 | }; |
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145 | |||
146 | } // End llvm namespace |
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147 | |||
148 | #endif |