1 // copy-relocs.cc -- handle COPY relocations for gold. 2 3 // Copyright (C) 2006-2016 Free Software Foundation, Inc. 4 // Written by Ian Lance Taylor <iant@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 #include "gold.h" 24 25 #include "symtab.h" 26 #include "copy-relocs.h" 27 28 namespace gold 29 { 30 31 // Copy_relocs methods. 32 33 // Handle a relocation against a symbol which may force us to generate 34 // a COPY reloc. 35 36 template<int sh_type, int size, bool big_endian> 37 void 38 Copy_relocs<sh_type, size, big_endian>::copy_reloc( 39 Symbol_table* symtab, 40 Layout* layout, 41 Sized_symbol<size>* sym, 42 Sized_relobj_file<size, big_endian>* object, 43 unsigned int shndx, 44 Output_section* output_section, 45 unsigned int r_type, 46 typename elfcpp::Elf_types<size>::Elf_Addr r_offset, 47 typename elfcpp::Elf_types<size>::Elf_Swxword r_addend, 48 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 49 { 50 if (this->need_copy_reloc(sym, object, shndx)) 51 this->make_copy_reloc(symtab, layout, sym, object, reloc_section); 52 else 53 { 54 // We may not need a COPY relocation. Save this relocation to 55 // possibly be emitted later. 56 this->save(sym, object, shndx, output_section, 57 r_type, r_offset, r_addend); 58 } 59 } 60 61 // Return whether we need a COPY reloc for a relocation against SYM. 62 // The relocation is begin applied to section SHNDX in OBJECT. 63 64 template<int sh_type, int size, bool big_endian> 65 bool 66 Copy_relocs<sh_type, size, big_endian>::need_copy_reloc( 67 Sized_symbol<size>* sym, 68 Sized_relobj_file<size, big_endian>* object, 69 unsigned int shndx) const 70 { 71 if (!parameters->options().copyreloc()) 72 return false; 73 74 if (sym->symsize() == 0) 75 return false; 76 77 // If this is a readonly section, then we need a COPY reloc. 78 // Otherwise we can use a dynamic reloc. Note that calling 79 // section_flags here can be slow, as the information is not cached; 80 // fortunately we shouldn't see too many potential COPY relocs. 81 if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0) 82 return true; 83 84 return false; 85 } 86 87 // Emit a COPY relocation for SYM. 88 89 template<int sh_type, int size, bool big_endian> 90 void 91 Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc( 92 Symbol_table* symtab, 93 Sized_symbol<size>* sym, 94 Output_data* posd, 95 off_t offset, 96 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 97 { 98 // Define the symbol as being copied. 99 symtab->define_with_copy_reloc(sym, posd, offset); 100 101 // Add the COPY relocation to the dynamic reloc section. 102 reloc_section->add_global_generic(sym, this->copy_reloc_type_, posd, 103 offset, 0); 104 } 105 106 // Make a COPY relocation for SYM and emit it. 107 108 template<int sh_type, int size, bool big_endian> 109 void 110 Copy_relocs<sh_type, size, big_endian>::make_copy_reloc( 111 Symbol_table* symtab, 112 Layout* layout, 113 Sized_symbol<size>* sym, 114 Sized_relobj_file<size, big_endian>* object, 115 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 116 { 117 // We should not be here if -z nocopyreloc is given. 118 gold_assert(parameters->options().copyreloc()); 119 120 gold_assert(sym->is_from_dynobj()); 121 122 // The symbol must not have protected visibility. 123 if (sym->is_protected()) 124 { 125 gold_error(_("%s: cannot make copy relocation for " 126 "protected symbol '%s', defined in %s"), 127 object->name().c_str(), 128 sym->name(), 129 sym->object()->name().c_str()); 130 } 131 132 typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize(); 133 134 // There is no defined way to determine the required alignment of 135 // the symbol. We know that the symbol is defined in a dynamic 136 // object. We start with the alignment of the section in which it 137 // is defined; presumably we do not require an alignment larger than 138 // that. Then we reduce that alignment if the symbol is not aligned 139 // within the section. 140 bool is_ordinary; 141 unsigned int shndx = sym->shndx(&is_ordinary); 142 gold_assert(is_ordinary); 143 typename elfcpp::Elf_types<size>::Elf_WXword addralign; 144 145 { 146 // Lock the object so we can read from it. This is only called 147 // single-threaded from scan_relocs, so it is OK to lock. 148 // Unfortunately we have no way to pass in a Task token. 149 const Task* dummy_task = reinterpret_cast<const Task*>(-1); 150 Object* obj = sym->object(); 151 Task_lock_obj<Object> tl(dummy_task, obj); 152 addralign = obj->section_addralign(shndx); 153 } 154 155 typename Sized_symbol<size>::Value_type value = sym->value(); 156 while ((value & (addralign - 1)) != 0) 157 addralign >>= 1; 158 159 // Mark the dynamic object as needed for the --as-needed option. 160 sym->object()->set_is_needed(); 161 162 if (this->dynbss_ == NULL) 163 { 164 this->dynbss_ = new Output_data_space(addralign, "** dynbss"); 165 layout->add_output_section_data(".bss", 166 elfcpp::SHT_NOBITS, 167 elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE, 168 this->dynbss_, ORDER_BSS, false); 169 } 170 171 Output_data_space* dynbss = this->dynbss_; 172 173 if (addralign > dynbss->addralign()) 174 dynbss->set_space_alignment(addralign); 175 176 section_size_type dynbss_size = 177 convert_to_section_size_type(dynbss->current_data_size()); 178 dynbss_size = align_address(dynbss_size, addralign); 179 section_size_type offset = dynbss_size; 180 dynbss->set_current_data_size(dynbss_size + symsize); 181 182 this->emit_copy_reloc(symtab, sym, dynbss, offset, reloc_section); 183 } 184 185 // Save a relocation to possibly be emitted later. 186 187 template<int sh_type, int size, bool big_endian> 188 void 189 Copy_relocs<sh_type, size, big_endian>::save( 190 Symbol* sym, 191 Sized_relobj_file<size, big_endian>* object, 192 unsigned int shndx, 193 Output_section* output_section, 194 unsigned int r_type, 195 typename elfcpp::Elf_types<size>::Elf_Addr r_offset, 196 typename elfcpp::Elf_types<size>::Elf_Swxword r_addend) 197 { 198 this->entries_.push_back(Copy_reloc_entry(sym, r_type, object, shndx, 199 output_section, r_offset, 200 r_addend)); 201 } 202 203 // Emit any saved relocs. 204 205 template<int sh_type, int size, bool big_endian> 206 void 207 Copy_relocs<sh_type, size, big_endian>::emit( 208 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 209 { 210 for (typename Copy_reloc_entries::iterator p = this->entries_.begin(); 211 p != this->entries_.end(); 212 ++p) 213 { 214 Copy_reloc_entry& entry = *p; 215 216 // If the symbol is no longer defined in a dynamic object, then we 217 // emitted a COPY relocation, and we do not want to emit this 218 // dynamic relocation. 219 if (entry.sym_->is_from_dynobj()) 220 reloc_section->add_global_generic(entry.sym_, entry.reloc_type_, 221 entry.output_section_, entry.relobj_, 222 entry.shndx_, entry.address_, 223 entry.addend_); 224 } 225 226 // We no longer need the saved information. 227 this->entries_.clear(); 228 } 229 230 // Instantiate the templates we need. 231 232 #ifdef HAVE_TARGET_32_LITTLE 233 template 234 class Copy_relocs<elfcpp::SHT_REL, 32, false>; 235 236 template 237 class Copy_relocs<elfcpp::SHT_RELA, 32, false>; 238 #endif 239 240 #ifdef HAVE_TARGET_32_BIG 241 template 242 class Copy_relocs<elfcpp::SHT_REL, 32, true>; 243 244 template 245 class Copy_relocs<elfcpp::SHT_RELA, 32, true>; 246 #endif 247 248 #ifdef HAVE_TARGET_64_LITTLE 249 template 250 class Copy_relocs<elfcpp::SHT_REL, 64, false>; 251 252 template 253 class Copy_relocs<elfcpp::SHT_RELA, 64, false>; 254 #endif 255 256 #ifdef HAVE_TARGET_64_BIG 257 template 258 class Copy_relocs<elfcpp::SHT_REL, 64, true>; 259 260 template 261 class Copy_relocs<elfcpp::SHT_RELA, 64, true>; 262 #endif 263 264 } // End namespace gold. 265