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 using JumpModType = uint32_t;
28
29 // List of target-independent relocation types. Relocations read
30 // from files are converted to these types so that the main code
31 // doesn't have to know about architecture-specific details.
32 enum RelExpr {
33 R_ABS,
34 R_ADDEND,
35 R_DTPREL,
36 R_GOT,
37 R_GOT_OFF,
38 R_GOT_PC,
39 R_GOTONLY_PC,
40 R_GOTPLTONLY_PC,
41 R_GOTPLT,
42 R_GOTPLTREL,
43 R_GOTREL,
44 R_NEG_TLS,
45 R_NONE,
46 R_PC,
47 R_PLT,
48 R_PLT_PC,
49 R_RELAX_GOT_PC,
50 R_RELAX_GOT_PC_NOPIC,
51 R_RELAX_TLS_GD_TO_IE,
52 R_RELAX_TLS_GD_TO_IE_ABS,
53 R_RELAX_TLS_GD_TO_IE_GOT_OFF,
54 R_RELAX_TLS_GD_TO_IE_GOTPLT,
55 R_RELAX_TLS_GD_TO_LE,
56 R_RELAX_TLS_GD_TO_LE_NEG,
57 R_RELAX_TLS_IE_TO_LE,
58 R_RELAX_TLS_LD_TO_LE,
59 R_RELAX_TLS_LD_TO_LE_ABS,
60 R_SIZE,
61 R_TLS,
62 R_TLSDESC,
63 R_TLSDESC_CALL,
64 R_TLSDESC_PC,
65 R_TLSGD_GOT,
66 R_TLSGD_GOTPLT,
67 R_TLSGD_PC,
68 R_TLSIE_HINT,
69 R_TLSLD_GOT,
70 R_TLSLD_GOTPLT,
71 R_TLSLD_GOT_OFF,
72 R_TLSLD_HINT,
73 R_TLSLD_PC,
74
75 // The following is abstract relocation types used for only one target.
76 //
77 // Even though RelExpr is intended to be a target-neutral representation
78 // of a relocation type, there are some relocations whose semantics are
79 // unique to a target. Such relocation are marked with R_<TARGET_NAME>.
80 R_AARCH64_GOT_PAGE_PC,
81 R_AARCH64_PAGE_PC,
82 R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
83 R_AARCH64_TLSDESC_PAGE,
84 R_ARM_PCA,
85 R_ARM_SBREL,
86 R_MIPS_GOTREL,
87 R_MIPS_GOT_GP,
88 R_MIPS_GOT_GP_PC,
89 R_MIPS_GOT_LOCAL_PAGE,
90 R_MIPS_GOT_OFF,
91 R_MIPS_GOT_OFF32,
92 R_MIPS_TLSGD,
93 R_MIPS_TLSLD,
94 R_PPC32_PLTREL,
95 R_PPC64_CALL,
96 R_PPC64_CALL_PLT,
97 R_PPC64_RELAX_TOC,
98 R_PPC64_TOCBASE,
99 R_RISCV_ADD,
100 R_RISCV_PC_INDIRECT,
101 R_CHERI_CAPABILITY_TABLE_INDEX,
102 R_CHERI_CAPABILITY_TABLE_INDEX_SMALL_IMMEDIATE,
103 R_CHERI_CAPABILITY_TABLE_INDEX_CALL,
104 R_CHERI_CAPABILITY_TABLE_INDEX_CALL_SMALL_IMMEDIATE,
105 R_CHERI_CAPABILITY_TABLE_ENTRY_PC,
106 R_CHERI_CAPABILITY_TABLE_TLSGD_ENTRY_PC,
107 R_CHERI_CAPABILITY_TABLE_TLSIE_ENTRY_PC,
108 R_CHERI_CAPABILITY_TABLE_REL, // relative offset to _CHERI_CAPABILITY_TABLE_
109 R_MIPS_CHERI_CAPTAB_TLSGD,
110 R_MIPS_CHERI_CAPTAB_TLSLD,
111 R_MIPS_CHERI_CAPTAB_TPREL,
112 R_CHERI_CAPABILITY
113 };
114
115 // Architecture-neutral representation of relocation.
116 struct Relocation {
117 RelExpr expr;
118 RelType type;
119 uint64_t offset;
120 int64_t addend;
121 Symbol *sym;
122 };
123
124 // Manipulate jump instructions with these modifiers. These are used to relax
125 // jump instruction opcodes at basic block boundaries and are particularly
126 // useful when basic block sections are enabled.
127 struct JumpInstrMod {
128 JumpModType original;
129 uint64_t offset;
130 unsigned size;
131 };
132
133 // This function writes undefined symbol diagnostics to an internal buffer.
134 // Call reportUndefinedSymbols() after calling scanRelocations() to emit
135 // the diagnostics.
136 template <class ELFT> void scanRelocations(InputSectionBase &);
137
138 template <class ELFT> void reportUndefinedSymbols();
139
140 void hexagonTLSSymbolUpdate(ArrayRef<OutputSection *> outputSections);
141 bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections);
142
143 class ThunkSection;
144 class Thunk;
145 struct InputSectionDescription;
146
147 class ThunkCreator {
148 public:
149 // Return true if Thunks have been added to OutputSections
150 bool createThunks(ArrayRef<OutputSection *> outputSections);
151
152 // The number of completed passes of createThunks this permits us
153 // to do one time initialization on Pass 0 and put a limit on the
154 // number of times it can be called to prevent infinite loops.
155 uint32_t pass = 0;
156
157 private:
158 void mergeThunks(ArrayRef<OutputSection *> outputSections);
159
160 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
161 InputSectionDescription *isd, uint32_t type,
162 uint64_t src);
163
164 ThunkSection *getISThunkSec(InputSection *isec);
165
166 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
167
168 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
169 uint64_t src);
170
171 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
172 uint64_t off);
173
174 bool normalizeExistingThunk(Relocation &rel, uint64_t src);
175
176 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
177 // is represented as a (section, offset) pair. There may be multiple
178 // relocations sharing the same (section, offset + addend) pair. We may revert
179 // a relocation back to its original non-Thunk target, and restore the
180 // original addend, so we cannot fold offset + addend. A nested pair is used
181 // because DenseMapInfo is not specialized for std::tuple.
182 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
183 std::vector<Thunk *>>
184 thunkedSymbolsBySectionAndAddend;
185 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
186 thunkedSymbols;
187
188 // Find a Thunk from the Thunks symbol definition, we can use this to find
189 // the Thunk from a relocation to the Thunks symbol definition.
190 llvm::DenseMap<Symbol *, Thunk *> thunks;
191
192 // Track InputSections that have an inline ThunkSection placed in front
193 // an inline ThunkSection may have control fall through to the section below
194 // so we need to make sure that there is only one of them.
195 // The Mips LA25 Thunk is an example of an inline ThunkSection.
196 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
197 };
198
199 // Return a int64_t to make sure we get the sign extension out of the way as
200 // early as possible.
201 template <class ELFT>
getAddend(const typename ELFT::Rel & rel)202 static inline int64_t getAddend(const typename ELFT::Rel &rel) {
203 return 0;
204 }
205 template <class ELFT>
getAddend(const typename ELFT::Rela & rel)206 static inline int64_t getAddend(const typename ELFT::Rela &rel) {
207 return rel.r_addend;
208 }
209
210 std::string getLocationMessage(const InputSectionBase &s, const Symbol &sym,
211 uint64_t off);
212
213 } // namespace elf
214 } // namespace lld
215
216 #endif
217