1 //===- Relocations.h -------------------------------------------*- 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 LLD_ELF_RELOCATIONS_H
10 #define LLD_ELF_RELOCATIONS_H
11
12 #include "lld/Common/LLVM.h"
13 #include "llvm/ADT/DenseMap.h"
14 #include <map>
15 #include <vector>
16
17 namespace lld {
18 namespace elf {
19 class Symbol;
20 class InputSection;
21 class InputSectionBase;
22 class OutputSection;
23 class SectionBase;
24
25 // Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL.
26 using RelType = uint32_t;
27
28 // List of target-independent relocation types. Relocations read
29 // from files are converted to these types so that the main code
30 // doesn't have to know about architecture-specific details.
31 enum RelExpr {
32 R_ABS,
33 R_ADDEND,
34 R_DTPREL,
35 R_GOT,
36 R_GOT_OFF,
37 R_GOT_PC,
38 R_GOTONLY_PC,
39 R_GOTPLTONLY_PC,
40 R_GOTPLT,
41 R_GOTPLTREL,
42 R_GOTREL,
43 R_NEG_TLS,
44 R_NONE,
45 R_PC,
46 R_PLT,
47 R_PLT_PC,
48 R_RELAX_GOT_PC,
49 R_RELAX_GOT_PC_NOPIC,
50 R_RELAX_TLS_GD_TO_IE,
51 R_RELAX_TLS_GD_TO_IE_ABS,
52 R_RELAX_TLS_GD_TO_IE_GOT_OFF,
53 R_RELAX_TLS_GD_TO_IE_GOTPLT,
54 R_RELAX_TLS_GD_TO_LE,
55 R_RELAX_TLS_GD_TO_LE_NEG,
56 R_RELAX_TLS_IE_TO_LE,
57 R_RELAX_TLS_LD_TO_LE,
58 R_RELAX_TLS_LD_TO_LE_ABS,
59 R_SIZE,
60 R_TLS,
61 R_TLSDESC,
62 R_TLSDESC_CALL,
63 R_TLSDESC_PC,
64 R_TLSGD_GOT,
65 R_TLSGD_GOTPLT,
66 R_TLSGD_PC,
67 R_TLSIE_HINT,
68 R_TLSLD_GOT,
69 R_TLSLD_GOTPLT,
70 R_TLSLD_GOT_OFF,
71 R_TLSLD_HINT,
72 R_TLSLD_PC,
73
74 // The following is abstract relocation types used for only one target.
75 //
76 // Even though RelExpr is intended to be a target-neutral representation
77 // of a relocation type, there are some relocations whose semantics are
78 // unique to a target. Such relocation are marked with R_<TARGET_NAME>.
79 R_AARCH64_GOT_PAGE_PC,
80 R_AARCH64_PAGE_PC,
81 R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
82 R_AARCH64_TLSDESC_PAGE,
83 R_ARM_SBREL,
84 R_MIPS_GOTREL,
85 R_MIPS_GOT_GP,
86 R_MIPS_GOT_GP_PC,
87 R_MIPS_GOT_LOCAL_PAGE,
88 R_MIPS_GOT_OFF,
89 R_MIPS_GOT_OFF32,
90 R_MIPS_TLSGD,
91 R_MIPS_TLSLD,
92 R_PPC32_PLTREL,
93 R_PPC64_CALL,
94 R_PPC64_CALL_PLT,
95 R_PPC64_RELAX_TOC,
96 R_PPC64_TOCBASE,
97 R_RISCV_ADD,
98 R_RISCV_PC_INDIRECT,
99 };
100
101 // Architecture-neutral representation of relocation.
102 struct Relocation {
103 RelExpr expr;
104 RelType type;
105 uint64_t offset;
106 int64_t addend;
107 Symbol *sym;
108 };
109
110 // This function writes undefined symbol diagnostics to an internal buffer.
111 // Call reportUndefinedSymbols() after calling scanRelocations() to emit
112 // the diagnostics.
113 template <class ELFT> void scanRelocations(InputSectionBase &);
114
115 template <class ELFT> void reportUndefinedSymbols();
116
117 class ThunkSection;
118 class Thunk;
119 struct InputSectionDescription;
120
121 class ThunkCreator {
122 public:
123 // Return true if Thunks have been added to OutputSections
124 bool createThunks(ArrayRef<OutputSection *> outputSections);
125
126 // The number of completed passes of createThunks this permits us
127 // to do one time initialization on Pass 0 and put a limit on the
128 // number of times it can be called to prevent infinite loops.
129 uint32_t pass = 0;
130
131 private:
132 void mergeThunks(ArrayRef<OutputSection *> outputSections);
133
134 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
135 InputSectionDescription *isd, uint32_t type,
136 uint64_t src);
137
138 ThunkSection *getISThunkSec(InputSection *isec);
139
140 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
141
142 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
143 uint64_t src);
144
145 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
146 uint64_t off);
147
148 bool normalizeExistingThunk(Relocation &rel, uint64_t src);
149
150 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
151 // is represented as a (section, offset) pair. There may be multiple
152 // relocations sharing the same (section, offset + addend) pair. We may revert
153 // a relocation back to its original non-Thunk target, and restore the
154 // original addend, so we cannot fold offset + addend. A nested pair is used
155 // because DenseMapInfo is not specialized for std::tuple.
156 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
157 std::vector<Thunk *>>
158 thunkedSymbolsBySectionAndAddend;
159 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
160 thunkedSymbols;
161
162 // Find a Thunk from the Thunks symbol definition, we can use this to find
163 // the Thunk from a relocation to the Thunks symbol definition.
164 llvm::DenseMap<Symbol *, Thunk *> thunks;
165
166 // Track InputSections that have an inline ThunkSection placed in front
167 // an inline ThunkSection may have control fall through to the section below
168 // so we need to make sure that there is only one of them.
169 // The Mips LA25 Thunk is an example of an inline ThunkSection.
170 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
171 };
172
173 // Return a int64_t to make sure we get the sign extension out of the way as
174 // early as possible.
175 template <class ELFT>
getAddend(const typename ELFT::Rel & rel)176 static inline int64_t getAddend(const typename ELFT::Rel &rel) {
177 return 0;
178 }
179 template <class ELFT>
getAddend(const typename ELFT::Rela & rel)180 static inline int64_t getAddend(const typename ELFT::Rela &rel) {
181 return rel.r_addend;
182 }
183 } // namespace elf
184 } // namespace lld
185
186 #endif
187