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