| 1 | // gc.h -- garbage collection of unused sections |
| 2 | |
| 3 | // Copyright 2009 Free Software Foundation, Inc. |
| 4 | // Written by Sriraman Tallam <tmsriram@google.com>. |
| 5 | |
| 6 | // This file is part of gold. |
| 7 | |
| 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. |
| 12 | |
| 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. |
| 17 | |
| 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. |
| 22 | |
| 23 | #ifndef GOLD_GC_H |
| 24 | #define GOLD_GC_H |
| 25 | |
| 26 | #include <queue> |
| 27 | |
| 28 | #include "elfcpp.h" |
| 29 | #include "symtab.h" |
| 30 | |
| 31 | namespace gold |
| 32 | { |
| 33 | |
| 34 | class Object; |
| 35 | |
| 36 | template<int size, bool big_endian> |
| 37 | class Sized_relobj; |
| 38 | |
| 39 | template<int sh_type, int size, bool big_endian> |
| 40 | class Reloc_types; |
| 41 | |
| 42 | class Output_section; |
| 43 | class General_options; |
| 44 | class Layout; |
| 45 | |
| 46 | typedef std::pair<Object *, unsigned int> Section_id; |
| 47 | |
| 48 | class Garbage_collection |
| 49 | { |
| 50 | struct Section_id_hash |
| 51 | { |
| 52 | size_t operator()(const Section_id& loc) const |
| 53 | { return reinterpret_cast<uintptr_t>(loc.first) ^ loc.second; } |
| 54 | }; |
| 55 | |
| 56 | typedef Unordered_set<Section_id, Section_id_hash> Sections_reachable; |
| 57 | typedef std::map<Section_id, Sections_reachable> Section_ref; |
| 58 | typedef std::queue<Section_id> Worklist_type; |
| 59 | |
| 60 | public : |
| 61 | Garbage_collection() |
| 62 | :is_worklist_ready_(false) |
| 63 | { } |
| 64 | |
| 65 | // Accessor methods for the private members. |
| 66 | |
| 67 | Sections_reachable& |
| 68 | referenced_list() |
| 69 | { return referenced_list_; } |
| 70 | |
| 71 | Section_ref& |
| 72 | section_reloc_map() |
| 73 | { return section_reloc_map_; } |
| 74 | |
| 75 | Worklist_type& |
| 76 | worklist() |
| 77 | { return work_list_; } |
| 78 | |
| 79 | bool |
| 80 | is_worklist_ready() |
| 81 | { return is_worklist_ready_; } |
| 82 | |
| 83 | void |
| 84 | worklist_ready() |
| 85 | { is_worklist_ready_ = true; } |
| 86 | |
| 87 | void |
| 88 | do_transitive_closure(); |
| 89 | |
| 90 | private : |
| 91 | Worklist_type work_list_; |
| 92 | bool is_worklist_ready_; |
| 93 | Section_ref section_reloc_map_; |
| 94 | Sections_reachable referenced_list_; |
| 95 | }; |
| 96 | |
| 97 | // Data to pass between successive invocations of do_layout |
| 98 | // in object.cc while garbage collecting. This data structure |
| 99 | // is filled by using the data from Read_symbols_data. |
| 100 | |
| 101 | struct Symbols_data |
| 102 | { |
| 103 | // Section headers. |
| 104 | unsigned char* section_headers_data; |
| 105 | // Section names. |
| 106 | unsigned char* section_names_data; |
| 107 | // Size of section name data in bytes. |
| 108 | section_size_type section_names_size; |
| 109 | // Symbol data. |
| 110 | unsigned char* symbols_data; |
| 111 | // Size of symbol data in bytes. |
| 112 | section_size_type symbols_size; |
| 113 | // Offset of external symbols within symbol data. This structure |
| 114 | // sometimes contains only external symbols, in which case this will |
| 115 | // be zero. Sometimes it contains all symbols. |
| 116 | section_offset_type external_symbols_offset; |
| 117 | // Symbol names. |
| 118 | unsigned char* symbol_names_data; |
| 119 | // Size of symbol name data in bytes. |
| 120 | section_size_type symbol_names_size; |
| 121 | }; |
| 122 | |
| 123 | // This function implements the the generic part of reloc |
| 124 | // processing to map a section to all the sections it |
| 125 | // references through relocs. It is used only during garbage |
| 126 | // collection. |
| 127 | |
| 128 | template<int size, bool big_endian, typename Target_type, int sh_type, |
| 129 | typename Scan> |
| 130 | inline void |
| 131 | gc_process_relocs( |
| 132 | const General_options& , |
| 133 | Symbol_table* symtab, |
| 134 | Layout*, |
| 135 | Target_type* , |
| 136 | Sized_relobj<size, big_endian>* object, |
| 137 | unsigned int data_shndx, |
| 138 | const unsigned char* prelocs, |
| 139 | size_t reloc_count, |
| 140 | Output_section*, |
| 141 | bool , |
| 142 | size_t local_count, |
| 143 | const unsigned char* plocal_syms) |
| 144 | { |
| 145 | Object *src_obj, *dst_obj; |
| 146 | unsigned int src_indx, dst_indx; |
| 147 | |
| 148 | src_obj = object; |
| 149 | src_indx = data_shndx; |
| 150 | |
| 151 | typedef typename Reloc_types<sh_type, size, big_endian>::Reloc Reltype; |
| 152 | const int reloc_size = Reloc_types<sh_type, size, big_endian>::reloc_size; |
| 153 | const int sym_size = elfcpp::Elf_sizes<size>::sym_size; |
| 154 | |
| 155 | for (size_t i = 0; i < reloc_count; ++i, prelocs += reloc_size) |
| 156 | { |
| 157 | Reltype reloc(prelocs); |
| 158 | typename elfcpp::Elf_types<size>::Elf_WXword r_info = reloc.get_r_info(); |
| 159 | unsigned int r_sym = elfcpp::elf_r_sym<size>(r_info); |
| 160 | |
| 161 | if (r_sym < local_count) |
| 162 | { |
| 163 | gold_assert(plocal_syms != NULL); |
| 164 | typename elfcpp::Sym<size, big_endian> lsym(plocal_syms |
| 165 | + r_sym * sym_size); |
| 166 | unsigned int shndx = lsym.get_st_shndx(); |
| 167 | bool is_ordinary; |
| 168 | shndx = object->adjust_sym_shndx(r_sym, shndx, &is_ordinary); |
| 169 | if (!is_ordinary) |
| 170 | continue; |
| 171 | dst_obj = src_obj; |
| 172 | if (shndx == src_indx) |
| 173 | continue; |
| 174 | dst_indx = shndx; |
| 175 | } |
| 176 | else |
| 177 | { |
| 178 | Symbol* gsym = object->global_symbol(r_sym); |
| 179 | gold_assert(gsym != NULL); |
| 180 | if (gsym->is_forwarder()) |
| 181 | gsym = symtab->resolve_forwards(gsym); |
| 182 | if (gsym->source() != Symbol::FROM_OBJECT) |
| 183 | continue; |
| 184 | bool is_ordinary; |
| 185 | dst_obj = gsym->object(); |
| 186 | dst_indx = gsym->shndx(&is_ordinary); |
| 187 | if (!is_ordinary) |
| 188 | continue; |
| 189 | } |
| 190 | Section_id p1(src_obj, src_indx); |
| 191 | Section_id p2(dst_obj, dst_indx); |
| 192 | Garbage_collection::Section_ref::iterator map_it; |
| 193 | map_it = symtab->gc()->section_reloc_map().find(p1); |
| 194 | if (map_it == symtab->gc()->section_reloc_map().end()) |
| 195 | { |
| 196 | symtab->gc()->section_reloc_map()[p1].insert(p2); |
| 197 | } |
| 198 | else |
| 199 | { |
| 200 | Garbage_collection::Sections_reachable& v(map_it->second); |
| 201 | v.insert(p2); |
| 202 | } |
| 203 | } |
| 204 | return; |
| 205 | } |
| 206 | |
| 207 | } // End of namespace gold. |
| 208 | |
| 209 | #endif |