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 "llvm/ADT/STLExtras.h"
15 #include <vector>
16
17 namespace lld::elf {
18 class Symbol;
19 class InputSection;
20 class InputSectionBase;
21 class OutputSection;
22 class SectionBase;
23
24 // Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL.
25 using RelType = uint32_t;
26 using JumpModType = 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_GOTPLT_GOTREL,
44 R_GOTPLT_PC,
45 R_NONE,
46 R_PC,
47 R_PLT,
48 R_PLT_PC,
49 R_PLT_GOTPLT,
50 R_PLT_GOTREL,
51 R_RELAX_HINT,
52 R_RELAX_GOT_PC,
53 R_RELAX_GOT_PC_NOPIC,
54 R_RELAX_TLS_GD_TO_IE,
55 R_RELAX_TLS_GD_TO_IE_ABS,
56 R_RELAX_TLS_GD_TO_IE_GOT_OFF,
57 R_RELAX_TLS_GD_TO_IE_GOTPLT,
58 R_RELAX_TLS_GD_TO_LE,
59 R_RELAX_TLS_GD_TO_LE_NEG,
60 R_RELAX_TLS_IE_TO_LE,
61 R_RELAX_TLS_LD_TO_LE,
62 R_RELAX_TLS_LD_TO_LE_ABS,
63 R_SIZE,
64 R_TPREL,
65 R_TPREL_NEG,
66 R_TLSDESC,
67 R_TLSDESC_CALL,
68 R_TLSDESC_PC,
69 R_TLSDESC_GOTPLT,
70 R_TLSGD_GOT,
71 R_TLSGD_GOTPLT,
72 R_TLSGD_PC,
73 R_TLSIE_HINT,
74 R_TLSLD_GOT,
75 R_TLSLD_GOTPLT,
76 R_TLSLD_GOT_OFF,
77 R_TLSLD_HINT,
78 R_TLSLD_PC,
79
80 // The following is abstract relocation types used for only one target.
81 //
82 // Even though RelExpr is intended to be a target-neutral representation
83 // of a relocation type, there are some relocations whose semantics are
84 // unique to a target. Such relocation are marked with R_<TARGET_NAME>.
85 R_AARCH64_GOT_PAGE_PC,
86 R_AARCH64_GOT_PAGE,
87 R_AARCH64_PAGE_PC,
88 R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
89 R_AARCH64_TLSDESC_PAGE,
90 R_ARM_PCA,
91 R_ARM_SBREL,
92 R_MIPS_GOTREL,
93 R_MIPS_GOT_GP,
94 R_MIPS_GOT_GP_PC,
95 R_MIPS_GOT_LOCAL_PAGE,
96 R_MIPS_GOT_OFF,
97 R_MIPS_GOT_OFF32,
98 R_MIPS_TLSGD,
99 R_MIPS_TLSLD,
100 R_PPC32_PLTREL,
101 R_PPC64_CALL,
102 R_PPC64_CALL_PLT,
103 R_PPC64_RELAX_TOC,
104 R_PPC64_TOCBASE,
105 R_PPC64_RELAX_GOT_PC,
106 R_RISCV_ADD,
107 R_RISCV_LEB128,
108 R_RISCV_PC_INDIRECT,
109 // Same as R_PC but with page-aligned semantics.
110 R_LOONGARCH_PAGE_PC,
111 // Same as R_PLT_PC but with page-aligned semantics.
112 R_LOONGARCH_PLT_PAGE_PC,
113 // In addition to having page-aligned semantics, LoongArch GOT relocs are
114 // also reused for TLS, making the semantics differ from other architectures.
115 R_LOONGARCH_GOT,
116 R_LOONGARCH_GOT_PAGE_PC,
117 R_LOONGARCH_TLSGD_PAGE_PC,
118 };
119
120 // Architecture-neutral representation of relocation.
121 struct Relocation {
122 RelExpr expr;
123 RelType type;
124 uint64_t offset;
125 int64_t addend;
126 Symbol *sym;
127 };
128
129 // Manipulate jump instructions with these modifiers. These are used to relax
130 // jump instruction opcodes at basic block boundaries and are particularly
131 // useful when basic block sections are enabled.
132 struct JumpInstrMod {
133 uint64_t offset;
134 JumpModType original;
135 unsigned size;
136 };
137
138 // This function writes undefined symbol diagnostics to an internal buffer.
139 // Call reportUndefinedSymbols() after calling scanRelocations() to emit
140 // the diagnostics.
141 template <class ELFT> void scanRelocations();
142 void reportUndefinedSymbols();
143 void postScanRelocations();
144 void addGotEntry(Symbol &sym);
145
146 void hexagonTLSSymbolUpdate(ArrayRef<OutputSection *> outputSections);
147 bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections);
148
149 class ThunkSection;
150 class Thunk;
151 class InputSectionDescription;
152
153 class ThunkCreator {
154 public:
155 // Return true if Thunks have been added to OutputSections
156 bool createThunks(uint32_t pass, ArrayRef<OutputSection *> outputSections);
157
158 private:
159 void mergeThunks(ArrayRef<OutputSection *> outputSections);
160
161 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
162 InputSectionDescription *isd,
163 const Relocation &rel, uint64_t src);
164
165 ThunkSection *getISThunkSec(InputSection *isec);
166
167 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
168
169 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
170 uint64_t src);
171
172 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
173 uint64_t off);
174
175 bool normalizeExistingThunk(Relocation &rel, uint64_t src);
176
177 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
178 // is represented as a (section, offset) pair. There may be multiple
179 // relocations sharing the same (section, offset + addend) pair. We may revert
180 // a relocation back to its original non-Thunk target, and restore the
181 // original addend, so we cannot fold offset + addend. A nested pair is used
182 // because DenseMapInfo is not specialized for std::tuple.
183 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
184 std::vector<Thunk *>>
185 thunkedSymbolsBySectionAndAddend;
186 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
187 thunkedSymbols;
188
189 // Find a Thunk from the Thunks symbol definition, we can use this to find
190 // the Thunk from a relocation to the Thunks symbol definition.
191 llvm::DenseMap<Symbol *, Thunk *> thunks;
192
193 // Track InputSections that have an inline ThunkSection placed in front
194 // an inline ThunkSection may have control fall through to the section below
195 // so we need to make sure that there is only one of them.
196 // The Mips LA25 Thunk is an example of an inline ThunkSection.
197 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
198
199 // The number of completed passes of createThunks this permits us
200 // to do one time initialization on Pass 0 and put a limit on the
201 // number of times it can be called to prevent infinite loops.
202 uint32_t pass = 0;
203 };
204
205 // Return a int64_t to make sure we get the sign extension out of the way as
206 // early as possible.
207 template <class ELFT>
getAddend(const typename ELFT::Rel & rel)208 static inline int64_t getAddend(const typename ELFT::Rel &rel) {
209 return 0;
210 }
211 template <class ELFT>
getAddend(const typename ELFT::Rela & rel)212 static inline int64_t getAddend(const typename ELFT::Rela &rel) {
213 return rel.r_addend;
214 }
215
216 template <typename RelTy>
sortRels(ArrayRef<RelTy> rels,SmallVector<RelTy,0> & storage)217 ArrayRef<RelTy> sortRels(ArrayRef<RelTy> rels, SmallVector<RelTy, 0> &storage) {
218 auto cmp = [](const RelTy &a, const RelTy &b) {
219 return a.r_offset < b.r_offset;
220 };
221 if (!llvm::is_sorted(rels, cmp)) {
222 storage.assign(rels.begin(), rels.end());
223 llvm::stable_sort(storage, cmp);
224 rels = storage;
225 }
226 return rels;
227 }
228
229 // Returns true if Expr refers a GOT entry. Note that this function returns
230 // false for TLS variables even though they need GOT, because TLS variables uses
231 // GOT differently than the regular variables.
232 bool needsGot(RelExpr expr);
233 } // namespace lld::elf
234
235 #endif
236