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
17namespace lld::elf {
18class Symbol;
19class InputSection;
20class InputSectionBase;
21class OutputSection;
22class SectionBase;
23
24// Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL.
25using RelType = uint32_t;
26using 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.
31enum 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_AARCH64_AUTH,
91 R_ARM_PCA,
92 R_ARM_SBREL,
93 R_MIPS_GOTREL,
94 R_MIPS_GOT_GP,
95 R_MIPS_GOT_GP_PC,
96 R_MIPS_GOT_LOCAL_PAGE,
97 R_MIPS_GOT_OFF,
98 R_MIPS_GOT_OFF32,
99 R_MIPS_TLSGD,
100 R_MIPS_TLSLD,
101 R_PPC32_PLTREL,
102 R_PPC64_CALL,
103 R_PPC64_CALL_PLT,
104 R_PPC64_RELAX_TOC,
105 R_PPC64_TOCBASE,
106 R_PPC64_RELAX_GOT_PC,
107 R_RISCV_ADD,
108 R_RISCV_LEB128,
109 R_RISCV_PC_INDIRECT,
110 // Same as R_PC but with page-aligned semantics.
111 R_LOONGARCH_PAGE_PC,
112 // Same as R_PLT_PC but with page-aligned semantics.
113 R_LOONGARCH_PLT_PAGE_PC,
114 // In addition to having page-aligned semantics, LoongArch GOT relocs are
115 // also reused for TLS, making the semantics differ from other architectures.
116 R_LOONGARCH_GOT,
117 R_LOONGARCH_GOT_PAGE_PC,
118 R_LOONGARCH_TLSGD_PAGE_PC,
119};
120
121// Architecture-neutral representation of relocation.
122struct Relocation {
123 RelExpr expr;
124 RelType type;
125 uint64_t offset;
126 int64_t addend;
127 Symbol *sym;
128};
129
130// Manipulate jump instructions with these modifiers. These are used to relax
131// jump instruction opcodes at basic block boundaries and are particularly
132// useful when basic block sections are enabled.
133struct JumpInstrMod {
134 uint64_t offset;
135 JumpModType original;
136 unsigned size;
137};
138
139// This function writes undefined symbol diagnostics to an internal buffer.
140// Call reportUndefinedSymbols() after calling scanRelocations() to emit
141// the diagnostics.
142template <class ELFT> void scanRelocations();
143void reportUndefinedSymbols();
144void postScanRelocations();
145void addGotEntry(Symbol &sym);
146
147void hexagonTLSSymbolUpdate(ArrayRef<OutputSection *> outputSections);
148bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections);
149
150class ThunkSection;
151class Thunk;
152class InputSectionDescription;
153
154class ThunkCreator {
155public:
156 // Return true if Thunks have been added to OutputSections
157 bool createThunks(uint32_t pass, ArrayRef<OutputSection *> outputSections);
158
159private:
160 void mergeThunks(ArrayRef<OutputSection *> outputSections);
161
162 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
163 InputSectionDescription *isd,
164 const Relocation &rel, uint64_t src);
165
166 ThunkSection *getISThunkSec(InputSection *isec);
167
168 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
169
170 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
171 uint64_t src);
172
173 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
174 uint64_t off);
175
176 bool normalizeExistingThunk(Relocation &rel, uint64_t src);
177
178 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
179 // is represented as a (section, offset) pair. There may be multiple
180 // relocations sharing the same (section, offset + addend) pair. We may revert
181 // a relocation back to its original non-Thunk target, and restore the
182 // original addend, so we cannot fold offset + addend. A nested pair is used
183 // because DenseMapInfo is not specialized for std::tuple.
184 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
185 std::vector<Thunk *>>
186 thunkedSymbolsBySectionAndAddend;
187 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
188 thunkedSymbols;
189
190 // Find a Thunk from the Thunks symbol definition, we can use this to find
191 // the Thunk from a relocation to the Thunks symbol definition.
192 llvm::DenseMap<Symbol *, Thunk *> thunks;
193
194 // Track InputSections that have an inline ThunkSection placed in front
195 // an inline ThunkSection may have control fall through to the section below
196 // so we need to make sure that there is only one of them.
197 // The Mips LA25 Thunk is an example of an inline ThunkSection.
198 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
199
200 // The number of completed passes of createThunks this permits us
201 // to do one time initialization on Pass 0 and put a limit on the
202 // number of times it can be called to prevent infinite loops.
203 uint32_t pass = 0;
204};
205
206// Return a int64_t to make sure we get the sign extension out of the way as
207// early as possible.
208template <class ELFT>
209static inline int64_t getAddend(const typename ELFT::Rel &rel) {
210 return 0;
211}
212template <class ELFT>
213static inline int64_t getAddend(const typename ELFT::Rela &rel) {
214 return rel.r_addend;
215}
216
217template <typename RelTy>
218ArrayRef<RelTy> sortRels(ArrayRef<RelTy> rels, SmallVector<RelTy, 0> &storage) {
219 auto cmp = [](const RelTy &a, const RelTy &b) {
220 return a.r_offset < b.r_offset;
221 };
222 if (!llvm::is_sorted(rels, cmp)) {
223 storage.assign(rels.begin(), rels.end());
224 llvm::stable_sort(storage, cmp);
225 rels = storage;
226 }
227 return rels;
228}
229
230// Returns true if Expr refers a GOT entry. Note that this function returns
231// false for TLS variables even though they need GOT, because TLS variables uses
232// GOT differently than the regular variables.
233bool needsGot(RelExpr expr);
234} // namespace lld::elf
235
236#endif
237

source code of lld/ELF/Relocations.h