1 | //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- 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_MCFIXUP_H |
10 | #define LLVM_MC_MCFIXUP_H |
11 | |
12 | #include "llvm/Support/DataTypes.h" |
13 | #include "llvm/Support/ErrorHandling.h" |
14 | #include "llvm/Support/SMLoc.h" |
15 | #include <cassert> |
16 | |
17 | namespace llvm { |
18 | class MCExpr; |
19 | |
20 | /// Extensible enumeration to represent the type of a fixup. |
21 | enum MCFixupKind { |
22 | FK_NONE = 0, ///< A no-op fixup. |
23 | FK_Data_1, ///< A one-byte fixup. |
24 | FK_Data_2, ///< A two-byte fixup. |
25 | FK_Data_4, ///< A four-byte fixup. |
26 | FK_Data_8, ///< A eight-byte fixup. |
27 | FK_Data_leb128, ///< A leb128 fixup. |
28 | FK_PCRel_1, ///< A one-byte pc relative fixup. |
29 | FK_PCRel_2, ///< A two-byte pc relative fixup. |
30 | FK_PCRel_4, ///< A four-byte pc relative fixup. |
31 | FK_PCRel_8, ///< A eight-byte pc relative fixup. |
32 | FK_GPRel_1, ///< A one-byte gp relative fixup. |
33 | FK_GPRel_2, ///< A two-byte gp relative fixup. |
34 | FK_GPRel_4, ///< A four-byte gp relative fixup. |
35 | FK_GPRel_8, ///< A eight-byte gp relative fixup. |
36 | FK_DTPRel_4, ///< A four-byte dtp relative fixup. |
37 | FK_DTPRel_8, ///< A eight-byte dtp relative fixup. |
38 | FK_TPRel_4, ///< A four-byte tp relative fixup. |
39 | FK_TPRel_8, ///< A eight-byte tp relative fixup. |
40 | FK_SecRel_1, ///< A one-byte section relative fixup. |
41 | FK_SecRel_2, ///< A two-byte section relative fixup. |
42 | FK_SecRel_4, ///< A four-byte section relative fixup. |
43 | FK_SecRel_8, ///< A eight-byte section relative fixup. |
44 | |
45 | FirstTargetFixupKind = 128, |
46 | |
47 | /// The range [FirstLiteralRelocationKind, MaxTargetFixupKind) is used for |
48 | /// relocations coming from .reloc directive. Fixup kind |
49 | /// FirstLiteralRelocationKind+V represents the relocation type with number V. |
50 | FirstLiteralRelocationKind = 256, |
51 | |
52 | /// Set limit to accommodate the highest reloc type in use for all Targets, |
53 | /// currently R_AARCH64_IRELATIVE at 1032, including room for expansion. |
54 | MaxFixupKind = FirstLiteralRelocationKind + 1032 + 32, |
55 | }; |
56 | |
57 | /// Encode information on a single operation to perform on a byte |
58 | /// sequence (e.g., an encoded instruction) which requires assemble- or run- |
59 | /// time patching. |
60 | /// |
61 | /// Fixups are used any time the target instruction encoder needs to represent |
62 | /// some value in an instruction which is not yet concrete. The encoder will |
63 | /// encode the instruction assuming the value is 0, and emit a fixup which |
64 | /// communicates to the assembler backend how it should rewrite the encoded |
65 | /// value. |
66 | /// |
67 | /// During the process of relaxation, the assembler will apply fixups as |
68 | /// symbolic values become concrete. When relaxation is complete, any remaining |
69 | /// fixups become relocations in the object file (or errors, if the fixup cannot |
70 | /// be encoded on the target). |
71 | class MCFixup { |
72 | /// The value to put into the fixup location. The exact interpretation of the |
73 | /// expression is target dependent, usually it will be one of the operands to |
74 | /// an instruction or an assembler directive. |
75 | const MCExpr *Value = nullptr; |
76 | |
77 | /// The byte index of start of the relocation inside the MCFragment. |
78 | uint32_t Offset = 0; |
79 | |
80 | /// The target dependent kind of fixup item this is. The kind is used to |
81 | /// determine how the operand value should be encoded into the instruction. |
82 | MCFixupKind Kind = FK_NONE; |
83 | |
84 | /// The source location which gave rise to the fixup, if any. |
85 | SMLoc Loc; |
86 | public: |
87 | static MCFixup create(uint32_t Offset, const MCExpr *Value, |
88 | MCFixupKind Kind, SMLoc Loc = SMLoc()) { |
89 | assert(Kind <= MaxFixupKind && "Kind out of range!" ); |
90 | MCFixup FI; |
91 | FI.Value = Value; |
92 | FI.Offset = Offset; |
93 | FI.Kind = Kind; |
94 | FI.Loc = Loc; |
95 | return FI; |
96 | } |
97 | |
98 | MCFixupKind getKind() const { return Kind; } |
99 | |
100 | unsigned getTargetKind() const { return Kind; } |
101 | |
102 | uint32_t getOffset() const { return Offset; } |
103 | void setOffset(uint32_t Value) { Offset = Value; } |
104 | |
105 | const MCExpr *getValue() const { return Value; } |
106 | |
107 | /// Return the generic fixup kind for a value with the given size. It |
108 | /// is an error to pass an unsupported size. |
109 | static MCFixupKind getKindForSize(unsigned Size, bool IsPCRel) { |
110 | switch (Size) { |
111 | default: llvm_unreachable("Invalid generic fixup size!" ); |
112 | case 1: |
113 | return IsPCRel ? FK_PCRel_1 : FK_Data_1; |
114 | case 2: |
115 | return IsPCRel ? FK_PCRel_2 : FK_Data_2; |
116 | case 4: |
117 | return IsPCRel ? FK_PCRel_4 : FK_Data_4; |
118 | case 8: |
119 | return IsPCRel ? FK_PCRel_8 : FK_Data_8; |
120 | } |
121 | } |
122 | |
123 | SMLoc getLoc() const { return Loc; } |
124 | }; |
125 | |
126 | } // End llvm namespace |
127 | |
128 | #endif |
129 | |