1 // copy-relocs.cc -- handle COPY relocations for gold. 2 3 // Copyright 2006, 2007, 2008, 2009, 2010 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::Copy_reloc_entry methods. 32 33 // Emit the reloc if appropriate. 34 35 template<int sh_type, int size, bool big_endian> 36 void 37 Copy_relocs<sh_type, size, big_endian>::Copy_reloc_entry::emit( 38 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 39 { 40 // If the symbol is no longer defined in a dynamic object, then we 41 // emitted a COPY relocation, and we do not want to emit this 42 // dynamic relocation. 43 if (this->sym_->is_from_dynobj()) 44 reloc_section->add_global(this->sym_, this->reloc_type_, 45 this->output_section_, this->relobj_, 46 this->shndx_, this->address_, 47 this->addend_); 48 } 49 50 // Copy_relocs methods. 51 52 // Handle a relocation against a symbol which may force us to generate 53 // a COPY reloc. 54 55 template<int sh_type, int size, bool big_endian> 56 void 57 Copy_relocs<sh_type, size, big_endian>::copy_reloc( 58 Symbol_table* symtab, 59 Layout* layout, 60 Sized_symbol<size>* sym, 61 Sized_relobj<size, big_endian>* object, 62 unsigned int shndx, 63 Output_section* output_section, 64 const Reloc& rel, 65 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 66 { 67 if (this->need_copy_reloc(sym, object, shndx)) 68 this->emit_copy_reloc(symtab, layout, sym, reloc_section); 69 else 70 { 71 // We may not need a COPY relocation. Save this relocation to 72 // possibly be emitted later. 73 this->save(sym, object, shndx, output_section, rel); 74 } 75 } 76 77 // Return whether we need a COPY reloc for a relocation against SYM. 78 // The relocation is begin applied to section SHNDX in OBJECT. 79 80 template<int sh_type, int size, bool big_endian> 81 bool 82 Copy_relocs<sh_type, size, big_endian>::need_copy_reloc( 83 Sized_symbol<size>* sym, 84 Sized_relobj<size, big_endian>* object, 85 unsigned int shndx) const 86 { 87 if (!parameters->options().copyreloc()) 88 return false; 89 90 if (sym->symsize() == 0) 91 return false; 92 93 // If this is a readonly section, then we need a COPY reloc. 94 // Otherwise we can use a dynamic reloc. Note that calling 95 // section_flags here can be slow, as the information is not cached; 96 // fortunately we shouldn't see too many potential COPY relocs. 97 if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0) 98 return true; 99 100 return false; 101 } 102 103 // Emit a COPY relocation for SYM. 104 105 template<int sh_type, int size, bool big_endian> 106 void 107 Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc( 108 Symbol_table* symtab, 109 Layout* layout, 110 Sized_symbol<size>* sym, 111 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 112 { 113 // We should not be here if -z nocopyreloc is given. 114 gold_assert(parameters->options().copyreloc()); 115 116 typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize(); 117 118 // There is no defined way to determine the required alignment of 119 // the symbol. We know that the symbol is defined in a dynamic 120 // object. We start with the alignment of the section in which it 121 // is defined; presumably we do not require an alignment larger than 122 // that. Then we reduce that alignment if the symbol is not aligned 123 // within the section. 124 gold_assert(sym->is_from_dynobj()); 125 bool is_ordinary; 126 unsigned int shndx = sym->shndx(&is_ordinary); 127 gold_assert(is_ordinary); 128 typename elfcpp::Elf_types<size>::Elf_WXword addralign; 129 130 { 131 // Lock the object so we can read from it. This is only called 132 // single-threaded from scan_relocs, so it is OK to lock. 133 // Unfortunately we have no way to pass in a Task token. 134 const Task* dummy_task = reinterpret_cast<const Task*>(-1); 135 Object* obj = sym->object(); 136 Task_lock_obj<Object> tl(dummy_task, obj); 137 addralign = obj->section_addralign(shndx); 138 } 139 140 typename Sized_symbol<size>::Value_type value = sym->value(); 141 while ((value & (addralign - 1)) != 0) 142 addralign >>= 1; 143 144 // Mark the dynamic object as needed for the --as-needed option. 145 sym->object()->set_is_needed(); 146 147 if (this->dynbss_ == NULL) 148 { 149 this->dynbss_ = new Output_data_space(addralign, "** dynbss"); 150 layout->add_output_section_data(".bss", 151 elfcpp::SHT_NOBITS, 152 elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE, 153 this->dynbss_, ORDER_BSS, false); 154 } 155 156 Output_data_space* dynbss = this->dynbss_; 157 158 if (addralign > dynbss->addralign()) 159 dynbss->set_space_alignment(addralign); 160 161 section_size_type dynbss_size = 162 convert_to_section_size_type(dynbss->current_data_size()); 163 dynbss_size = align_address(dynbss_size, addralign); 164 section_size_type offset = dynbss_size; 165 dynbss->set_current_data_size(dynbss_size + symsize); 166 167 // Define the symbol as being copied. 168 symtab->define_with_copy_reloc(sym, dynbss, offset); 169 170 // Add the COPY relocation to the dynamic reloc section. 171 this->add_copy_reloc(sym, offset, reloc_section); 172 } 173 174 // Add a COPY relocation for SYM to RELOC_SECTION. 175 176 template<int sh_type, int size, bool big_endian> 177 void 178 Copy_relocs<sh_type, size, big_endian>::add_copy_reloc( 179 Symbol* sym, 180 section_size_type offset, 181 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 182 { 183 reloc_section->add_global(sym, this->copy_reloc_type_, this->dynbss_, 184 offset, 0); 185 } 186 187 // Save a relocation to possibly be emitted later. 188 189 template<int sh_type, int size, bool big_endian> 190 void 191 Copy_relocs<sh_type, size, big_endian>::save( 192 Symbol* sym, 193 Sized_relobj<size, big_endian>* object, 194 unsigned int shndx, 195 Output_section* output_section, 196 const Reloc& rel) 197 { 198 unsigned int reloc_type = elfcpp::elf_r_type<size>(rel.get_r_info()); 199 typename elfcpp::Elf_types<size>::Elf_Addr addend = 200 Reloc_types<sh_type, size, big_endian>::get_reloc_addend_noerror(&rel); 201 this->entries_.push_back(Copy_reloc_entry(sym, reloc_type, object, shndx, 202 output_section, rel.get_r_offset(), 203 addend)); 204 } 205 206 // Emit any saved relocs. 207 208 template<int sh_type, int size, bool big_endian> 209 void 210 Copy_relocs<sh_type, size, big_endian>::emit( 211 Output_data_reloc<sh_type, true, size, big_endian>* reloc_section) 212 { 213 for (typename Copy_reloc_entries::iterator p = this->entries_.begin(); 214 p != this->entries_.end(); 215 ++p) 216 p->emit(reloc_section); 217 218 // We no longer need the saved information. 219 this->entries_.clear(); 220 } 221 222 // Instantiate the templates we need. 223 224 #ifdef HAVE_TARGET_32_LITTLE 225 template 226 class Copy_relocs<elfcpp::SHT_REL, 32, false>; 227 228 template 229 class Copy_relocs<elfcpp::SHT_RELA, 32, false>; 230 #endif 231 232 #ifdef HAVE_TARGET_32_BIG 233 template 234 class Copy_relocs<elfcpp::SHT_REL, 32, true>; 235 236 template 237 class Copy_relocs<elfcpp::SHT_RELA, 32, true>; 238 #endif 239 240 #ifdef HAVE_TARGET_64_LITTLE 241 template 242 class Copy_relocs<elfcpp::SHT_REL, 64, false>; 243 244 template 245 class Copy_relocs<elfcpp::SHT_RELA, 64, false>; 246 #endif 247 248 #ifdef HAVE_TARGET_64_BIG 249 template 250 class Copy_relocs<elfcpp::SHT_REL, 64, true>; 251 252 template 253 class Copy_relocs<elfcpp::SHT_RELA, 64, true>; 254 #endif 255 256 } // End namespace gold. 257