xref: /openbsd/gnu/llvm/lld/ELF/Relocations.h (revision dfe94b16)
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