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[binutils.git] / gold / copy-relocs.h
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1 // copy-relocs.h -- handle COPY relocations for gold -*- C++ -*-
3 // Copyright 2006, 2007, 2008 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 3 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the Free Software
20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
21 // MA 02110-1301, USA.
23 #ifndef GOLD_COPY_RELOCS_H
24 #define GOLD_COPY_RELOCS_H
26 #include "elfcpp.h"
27 #include "reloc-types.h"
28 #include "output.h"
30 namespace gold
33 // This class is used to manage COPY relocations. We try to avoid
34 // them when possible. A COPY relocation may be required when an
35 // executable refers to a variable defined in a shared library. COPY
36 // relocations are problematic because they tie the executable to the
37 // exact size of the variable in the shared library. We can avoid
38 // them if all the references to the variable are in a writeable
39 // section. In that case we can simply use dynamic relocations.
40 // However, when scanning relocs, we don't know when we see the
41 // relocation whether we will be forced to use a COPY relocation or
42 // not. So we have to save the relocation during the reloc scanning,
43 // and then emit it as a dynamic relocation if necessary. This class
44 // implements that. It is used by the target specific code.
46 // The template parameter SH_TYPE is the type of the reloc section to
47 // be used for COPY relocs: elfcpp::SHT_REL or elfcpp::SHT_RELA.
49 template<int sh_type, int size, bool big_endian>
50 class Copy_relocs
52 private:
53 typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reloc;
55 public:
56 Copy_relocs(unsigned int copy_reloc_type)
57 : copy_reloc_type_(copy_reloc_type), dynbss_(NULL), entries_()
58 { }
60 // This is called while scanning relocs if we see a relocation
61 // against a symbol which may force us to generate a COPY reloc.
62 // SYM is the symbol. OBJECT is the object whose relocs we are
63 // scanning. The relocation is being applied to section SHNDX in
64 // OBJECT. OUTPUT_SECTION is the output section where section SHNDX
65 // will wind up. REL is the reloc itself. The Output_data_reloc
66 // section is where the dynamic relocs are put.
67 void
68 copy_reloc(Symbol_table*, Layout*, Sized_symbol<size>* sym,
69 Sized_relobj<size, big_endian>* object,
70 unsigned int shndx, Output_section* output_section,
71 const Reloc& rel,
72 Output_data_reloc<sh_type, true, size, big_endian>*);
74 // Return whether there are any saved relocations.
75 bool
76 any_saved_relocs() const
77 { return !this->entries_.empty(); }
79 // Emit any saved relocations which turn out to be needed. This is
80 // called after all the relocs have been scanned.
81 void
82 emit(Output_data_reloc<sh_type, true, size, big_endian>*);
84 private:
85 typedef typename elfcpp::Elf_types<size>::Elf_Addr Address;
86 typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend;
88 // This POD class holds the relocations we are saving. We will emit
89 // these relocations if it turns out that the symbol does not
90 // require a COPY relocation.
91 class Copy_reloc_entry
93 public:
94 Copy_reloc_entry(Symbol* sym, unsigned int reloc_type,
95 Sized_relobj<size, big_endian>* relobj,
96 unsigned int shndx,
97 Output_section* output_section,
98 Address address, Addend addend)
99 : sym_(sym), reloc_type_(reloc_type), relobj_(relobj),
100 shndx_(shndx), output_section_(output_section),
101 address_(address), addend_(addend)
104 // Emit this reloc if appropriate. This is called after we have
105 // scanned all the relocations, so we know whether we emitted a
106 // COPY relocation for SYM_.
107 void
108 emit(Output_data_reloc<sh_type, true, size, big_endian>*);
110 private:
111 Symbol* sym_;
112 unsigned int reloc_type_;
113 Sized_relobj<size, big_endian>* relobj_;
114 unsigned int shndx_;
115 Output_section* output_section_;
116 Address address_;
117 Addend addend_;
120 // A list of relocs to be saved.
121 typedef std::vector<Copy_reloc_entry> Copy_reloc_entries;
123 // Return whether we need a COPY reloc.
124 bool
125 need_copy_reloc(Sized_symbol<size>* gsym,
126 Sized_relobj<size, big_endian>* object,
127 unsigned int shndx) const;
129 // Emit a COPY reloc.
130 void
131 emit_copy_reloc(Symbol_table*, Layout*, Sized_symbol<size>*,
132 Output_data_reloc<sh_type, true, size, big_endian>*);
134 // Add a COPY reloc to the dynamic reloc section.
135 void
136 add_copy_reloc(Symbol*, section_size_type,
137 Output_data_reloc<sh_type, true, size, big_endian>*);
139 // Save a reloc against SYM for possible emission later.
140 void
141 save(Symbol*, Sized_relobj<size, big_endian>*, unsigned int shndx,
142 Output_section*, const Reloc& rel);
144 // The target specific relocation type of the COPY relocation.
145 const unsigned int copy_reloc_type_;
146 // The dynamic BSS data which goes into the .bss section. This is
147 // where variables which require COPY relocations are placed.
148 Output_data_space* dynbss_;
149 // The list of relocs we are saving.
150 Copy_reloc_entries entries_;
153 } // End namespace gold.
155 #endif // !defined(GOLD_COPY_RELOCS_H)