| 1 | // reloc.h -- relocate input files for gold -*- C++ -*- |
| 2 | |
| 3 | #ifndef GOLD_RELOC_H |
| 4 | #define GOLD_RELOC_H |
| 5 | |
| 6 | #include <byteswap.h> |
| 7 | |
| 8 | #include "workqueue.h" |
| 9 | |
| 10 | namespace gold |
| 11 | { |
| 12 | |
| 13 | class General_options; |
| 14 | class Relobj; |
| 15 | class Read_relocs_data; |
| 16 | class Stringpool; |
| 17 | class Symbol; |
| 18 | class Layout; |
| 19 | |
| 20 | template<int size> |
| 21 | class Sized_symbol; |
| 22 | |
| 23 | template<int sh_type, bool dynamic, int size, bool big_endian> |
| 24 | class Output_data_reloc; |
| 25 | |
| 26 | // A class to read the relocations for an object file, and then queue |
| 27 | // up a task to see if they require any GOT/PLT/COPY relocations in |
| 28 | // the symbol table. |
| 29 | |
| 30 | class Read_relocs : public Task |
| 31 | { |
| 32 | public: |
| 33 | // SYMTAB_LOCK is used to lock the symbol table. BLOCKER should be |
| 34 | // unblocked when the Scan_relocs task completes. |
| 35 | Read_relocs(const General_options& options, Symbol_table* symtab, |
| 36 | Layout* layout, Relobj* object, Task_token* symtab_lock, |
| 37 | Task_token* blocker) |
| 38 | : options_(options), symtab_(symtab), layout_(layout), object_(object), |
| 39 | symtab_lock_(symtab_lock), blocker_(blocker) |
| 40 | { } |
| 41 | |
| 42 | // The standard Task methods. |
| 43 | |
| 44 | Is_runnable_type |
| 45 | is_runnable(Workqueue*); |
| 46 | |
| 47 | Task_locker* |
| 48 | locks(Workqueue*); |
| 49 | |
| 50 | void |
| 51 | run(Workqueue*); |
| 52 | |
| 53 | private: |
| 54 | const General_options& options_; |
| 55 | Symbol_table* symtab_; |
| 56 | Layout* layout_; |
| 57 | Relobj* object_; |
| 58 | Task_token* symtab_lock_; |
| 59 | Task_token* blocker_; |
| 60 | }; |
| 61 | |
| 62 | // Scan the relocations for an object to see if they require any |
| 63 | // GOT/PLT/COPY relocations. |
| 64 | |
| 65 | class Scan_relocs : public Task |
| 66 | { |
| 67 | public: |
| 68 | // SYMTAB_LOCK is used to lock the symbol table. BLOCKER should be |
| 69 | // unblocked when the task completes. |
| 70 | Scan_relocs(const General_options& options, Symbol_table* symtab, |
| 71 | Layout* layout, Relobj* object, Read_relocs_data* rd, |
| 72 | Task_token* symtab_lock, Task_token* blocker) |
| 73 | : options_(options), symtab_(symtab), layout_(layout), object_(object), |
| 74 | rd_(rd), symtab_lock_(symtab_lock), blocker_(blocker) |
| 75 | { } |
| 76 | |
| 77 | // The standard Task methods. |
| 78 | |
| 79 | Is_runnable_type |
| 80 | is_runnable(Workqueue*); |
| 81 | |
| 82 | Task_locker* |
| 83 | locks(Workqueue*); |
| 84 | |
| 85 | void |
| 86 | run(Workqueue*); |
| 87 | |
| 88 | private: |
| 89 | class Scan_relocs_locker; |
| 90 | |
| 91 | const General_options& options_; |
| 92 | Symbol_table* symtab_; |
| 93 | Layout* layout_; |
| 94 | Relobj* object_; |
| 95 | Read_relocs_data* rd_; |
| 96 | Task_token* symtab_lock_; |
| 97 | Task_token* blocker_; |
| 98 | }; |
| 99 | |
| 100 | // A class to perform all the relocations for an object file. |
| 101 | |
| 102 | class Relocate_task : public Task |
| 103 | { |
| 104 | public: |
| 105 | Relocate_task(const General_options& options, const Symbol_table* symtab, |
| 106 | const Layout* layout, Relobj* object, Output_file* of, |
| 107 | Task_token* final_blocker) |
| 108 | : options_(options), symtab_(symtab), layout_(layout), object_(object), |
| 109 | of_(of), final_blocker_(final_blocker) |
| 110 | { } |
| 111 | |
| 112 | // The standard Task methods. |
| 113 | |
| 114 | Is_runnable_type |
| 115 | is_runnable(Workqueue*); |
| 116 | |
| 117 | Task_locker* |
| 118 | locks(Workqueue*); |
| 119 | |
| 120 | void |
| 121 | run(Workqueue*); |
| 122 | |
| 123 | private: |
| 124 | class Relocate_locker; |
| 125 | |
| 126 | const General_options& options_; |
| 127 | const Symbol_table* symtab_; |
| 128 | const Layout* layout_; |
| 129 | Relobj* object_; |
| 130 | Output_file* of_; |
| 131 | Task_token* final_blocker_; |
| 132 | }; |
| 133 | |
| 134 | // Standard relocation routines which are used on many targets. Here |
| 135 | // SIZE and BIG_ENDIAN refer to the target, not the relocation type. |
| 136 | |
| 137 | template<int size, bool big_endian> |
| 138 | class Relocate_functions |
| 139 | { |
| 140 | private: |
| 141 | // Do a simple relocation with the addend in the section contents. |
| 142 | // VALSIZE is the size of the value. |
| 143 | template<int valsize> |
| 144 | static inline void |
| 145 | rel(unsigned char* view, |
| 146 | typename elfcpp::Swap<valsize, big_endian>::Valtype value) |
| 147 | { |
| 148 | typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype; |
| 149 | Valtype* wv = reinterpret_cast<Valtype*>(view); |
| 150 | Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv); |
| 151 | elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value); |
| 152 | } |
| 153 | |
| 154 | // Do a simple PC relative relocation with the addend in the section |
| 155 | // contents. VALSIZE is the size of the value. |
| 156 | template<int valsize> |
| 157 | static inline void |
| 158 | pcrel(unsigned char* view, |
| 159 | typename elfcpp::Swap<valsize, big_endian>::Valtype value, |
| 160 | typename elfcpp::Elf_types<size>::Elf_Addr address) |
| 161 | { |
| 162 | typedef typename elfcpp::Swap<valsize, big_endian>::Valtype Valtype; |
| 163 | Valtype* wv = reinterpret_cast<Valtype*>(view); |
| 164 | Valtype x = elfcpp::Swap<valsize, big_endian>::readval(wv); |
| 165 | elfcpp::Swap<valsize, big_endian>::writeval(wv, x + value - address); |
| 166 | } |
| 167 | |
| 168 | typedef Relocate_functions<size, big_endian> This; |
| 169 | |
| 170 | public: |
| 171 | // Do a simple 8-bit REL relocation with the addend in the object |
| 172 | // file data. |
| 173 | static inline void |
| 174 | rel8(unsigned char* view, unsigned char value) |
| 175 | { |
| 176 | This::template rel<8>(view, value); |
| 177 | } |
| 178 | |
| 179 | // Do a simple 8-bit PC relative relocation with the addend in the |
| 180 | // object file data. |
| 181 | static inline void |
| 182 | pcrel8(unsigned char* view, unsigned char value, |
| 183 | typename elfcpp::Elf_types<size>::Elf_Addr address) |
| 184 | { |
| 185 | This::template pcrel<8>(view, value, address); |
| 186 | } |
| 187 | |
| 188 | // Do a simple 16-bit REL relocation with the addend in the object |
| 189 | // file data. |
| 190 | static inline void |
| 191 | rel16(unsigned char* view, elfcpp::Elf_Half value) |
| 192 | { |
| 193 | This::template rel<16>(view, value); |
| 194 | } |
| 195 | |
| 196 | // Do a simple 32-bit PC relative REL relocation with the addend in |
| 197 | // the object file data. |
| 198 | static inline void |
| 199 | pcrel16(unsigned char* view, elfcpp::Elf_Word value, |
| 200 | typename elfcpp::Elf_types<size>::Elf_Addr address) |
| 201 | { |
| 202 | This::template pcrel<16>(view, value, address); |
| 203 | } |
| 204 | |
| 205 | // Do a simple 32-bit REL relocation with the addend in the section |
| 206 | // contents. |
| 207 | static inline void |
| 208 | rel32(unsigned char* view, elfcpp::Elf_Word value) |
| 209 | { |
| 210 | This::template rel<32>(view, value); |
| 211 | } |
| 212 | |
| 213 | // Do a simple 32-bit PC relative REL relocation with the addend in |
| 214 | // the section contents. |
| 215 | static inline void |
| 216 | pcrel32(unsigned char* view, elfcpp::Elf_Word value, |
| 217 | typename elfcpp::Elf_types<size>::Elf_Addr address) |
| 218 | { |
| 219 | This::template pcrel<32>(view, value, address); |
| 220 | } |
| 221 | |
| 222 | // Do a simple 64-bit REL relocation with the addend in the section |
| 223 | // contents. |
| 224 | static inline void |
| 225 | rel64(unsigned char* view, elfcpp::Elf_Xword value) |
| 226 | { |
| 227 | This::template rel<64>(view, value); |
| 228 | } |
| 229 | |
| 230 | // Do a simple 64-bit PC relative REL relocation with the addend in |
| 231 | // the section contents. |
| 232 | static inline void |
| 233 | pcrel64(unsigned char* view, elfcpp::Elf_Xword value, |
| 234 | typename elfcpp::Elf_types<size>::Elf_Addr address) |
| 235 | { |
| 236 | This::template pcrel<64>(view, value, address); |
| 237 | } |
| 238 | }; |
| 239 | |
| 240 | // We try to avoid COPY relocations when possible. A COPY relocation |
| 241 | // may be required when an executable refers to a variable defined in |
| 242 | // a shared library. COPY relocations are problematic because they |
| 243 | // tie the executable to the exact size of the variable in the shared |
| 244 | // library. We can avoid them if all the references to the variable |
| 245 | // are in a writeable section. In that case we can simply use dynamic |
| 246 | // relocations. However, when scanning relocs, we don't know when we |
| 247 | // see the relocation whether we will be forced to use a COPY |
| 248 | // relocation or not. So we have to save the relocation during the |
| 249 | // reloc scanning, and then emit it as a dynamic relocation if |
| 250 | // necessary. This class implements that. It is used by the target |
| 251 | // specific code. |
| 252 | |
| 253 | template<int size, bool big_endian> |
| 254 | class Copy_relocs |
| 255 | { |
| 256 | public: |
| 257 | Copy_relocs() |
| 258 | : entries_() |
| 259 | { } |
| 260 | |
| 261 | // Return whether we need a COPY reloc for a reloc against GSYM, |
| 262 | // which is being applied to section SHNDX in OBJECT. |
| 263 | static bool |
| 264 | need_copy_reloc(const General_options*, Relobj* object, unsigned int shndx, |
| 265 | Sized_symbol<size>* gsym); |
| 266 | |
| 267 | // Save a Rel against SYM for possible emission later. SHNDX is the |
| 268 | // index of the section to which the reloc is being applied. |
| 269 | void |
| 270 | save(Symbol* sym, Relobj*, unsigned int shndx, |
| 271 | const elfcpp::Rel<size, big_endian>&); |
| 272 | |
| 273 | // Save a Rela against SYM for possible emission later. |
| 274 | void |
| 275 | save(Symbol* sym, Relobj*, unsigned int shndx, |
| 276 | const elfcpp::Rela<size, big_endian>&); |
| 277 | |
| 278 | // Return whether there are any relocs to emit. This also discards |
| 279 | // entries which need not be emitted. |
| 280 | bool |
| 281 | any_to_emit(); |
| 282 | |
| 283 | // Emit relocs for each symbol which did not get a COPY reloc (i.e., |
| 284 | // is still defined in the dynamic object). |
| 285 | template<int sh_type> |
| 286 | void |
| 287 | emit(Output_data_reloc<sh_type, true, size, big_endian>*); |
| 288 | |
| 289 | private: |
| 290 | typedef typename elfcpp::Elf_types<size>::Elf_Addr Address; |
| 291 | typedef typename elfcpp::Elf_types<size>::Elf_Addr Addend; |
| 292 | |
| 293 | // This POD class holds the entries we are saving. |
| 294 | class Copy_reloc_entry |
| 295 | { |
| 296 | public: |
| 297 | Copy_reloc_entry(Symbol* sym, unsigned int reloc_type, |
| 298 | Relobj* relobj, unsigned int shndx, |
| 299 | Address address, Addend addend) |
| 300 | : sym_(sym), reloc_type_(reloc_type), relobj_(relobj), |
| 301 | shndx_(shndx), address_(address), addend_(addend) |
| 302 | { } |
| 303 | |
| 304 | // Return whether we should emit this reloc. If we should not |
| 305 | // emit, we clear it. |
| 306 | bool |
| 307 | should_emit(); |
| 308 | |
| 309 | // Emit this reloc. |
| 310 | |
| 311 | void |
| 312 | emit(Output_data_reloc<elfcpp::SHT_REL, true, size, big_endian>*); |
| 313 | |
| 314 | void |
| 315 | emit(Output_data_reloc<elfcpp::SHT_RELA, true, size, big_endian>*); |
| 316 | |
| 317 | private: |
| 318 | Symbol* sym_; |
| 319 | unsigned int reloc_type_; |
| 320 | Relobj* relobj_; |
| 321 | unsigned int shndx_; |
| 322 | Address address_; |
| 323 | Addend addend_; |
| 324 | }; |
| 325 | |
| 326 | // A list of relocs to be saved. |
| 327 | typedef std::vector<Copy_reloc_entry> Copy_reloc_entries; |
| 328 | |
| 329 | // The list of relocs we are saving. |
| 330 | Copy_reloc_entries entries_; |
| 331 | }; |
| 332 | |
| 333 | } // End namespace gold. |
| 334 | |
| 335 | #endif // !defined(GOLD_RELOC_H) |