| 1 | // target.h -- target support for gold -*- C++ -*- |
| 2 | |
| 3 | // Copyright 2006, 2007, 2008, 2009 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 | // The abstract class Target is the interface for target specific |
| 24 | // support. It defines abstract methods which each target must |
| 25 | // implement. Typically there will be one target per processor, but |
| 26 | // in some cases it may be necessary to have subclasses. |
| 27 | |
| 28 | // For speed and consistency we want to use inline functions to handle |
| 29 | // relocation processing. So besides implementations of the abstract |
| 30 | // methods, each target is expected to define a template |
| 31 | // specialization of the relocation functions. |
| 32 | |
| 33 | #ifndef GOLD_TARGET_H |
| 34 | #define GOLD_TARGET_H |
| 35 | |
| 36 | #include "elfcpp.h" |
| 37 | #include "options.h" |
| 38 | #include "parameters.h" |
| 39 | |
| 40 | namespace gold |
| 41 | { |
| 42 | |
| 43 | class General_options; |
| 44 | class Object; |
| 45 | template<int size, bool big_endian> |
| 46 | class Sized_relobj; |
| 47 | class Relocatable_relocs; |
| 48 | template<int size, bool big_endian> |
| 49 | class Relocate_info; |
| 50 | class Symbol; |
| 51 | template<int size> |
| 52 | class Sized_symbol; |
| 53 | class Symbol_table; |
| 54 | class Output_section; |
| 55 | |
| 56 | // The abstract class for target specific handling. |
| 57 | |
| 58 | class Target |
| 59 | { |
| 60 | public: |
| 61 | virtual ~Target() |
| 62 | { } |
| 63 | |
| 64 | // Return the bit size that this target implements. This should |
| 65 | // return 32 or 64. |
| 66 | int |
| 67 | get_size() const |
| 68 | { return this->pti_->size; } |
| 69 | |
| 70 | // Return whether this target is big-endian. |
| 71 | bool |
| 72 | is_big_endian() const |
| 73 | { return this->pti_->is_big_endian; } |
| 74 | |
| 75 | // Machine code to store in e_machine field of ELF header. |
| 76 | elfcpp::EM |
| 77 | machine_code() const |
| 78 | { return this->pti_->machine_code; } |
| 79 | |
| 80 | // Whether this target has a specific make_symbol function. |
| 81 | bool |
| 82 | has_make_symbol() const |
| 83 | { return this->pti_->has_make_symbol; } |
| 84 | |
| 85 | // Whether this target has a specific resolve function. |
| 86 | bool |
| 87 | has_resolve() const |
| 88 | { return this->pti_->has_resolve; } |
| 89 | |
| 90 | // Whether this target has a specific code fill function. |
| 91 | bool |
| 92 | has_code_fill() const |
| 93 | { return this->pti_->has_code_fill; } |
| 94 | |
| 95 | // Return the default name of the dynamic linker. |
| 96 | const char* |
| 97 | dynamic_linker() const |
| 98 | { return this->pti_->dynamic_linker; } |
| 99 | |
| 100 | // Return the default address to use for the text segment. |
| 101 | uint64_t |
| 102 | default_text_segment_address() const |
| 103 | { return this->pti_->default_text_segment_address; } |
| 104 | |
| 105 | // Return the ABI specified page size. |
| 106 | uint64_t |
| 107 | abi_pagesize() const |
| 108 | { |
| 109 | if (parameters->options().max_page_size() > 0) |
| 110 | return parameters->options().max_page_size(); |
| 111 | else |
| 112 | return this->pti_->abi_pagesize; |
| 113 | } |
| 114 | |
| 115 | // Return the common page size used on actual systems. |
| 116 | uint64_t |
| 117 | common_pagesize() const |
| 118 | { |
| 119 | if (parameters->options().common_page_size() > 0) |
| 120 | return std::min(parameters->options().common_page_size(), |
| 121 | this->abi_pagesize()); |
| 122 | else |
| 123 | return std::min(this->pti_->common_pagesize, |
| 124 | this->abi_pagesize()); |
| 125 | } |
| 126 | |
| 127 | // If we see some object files with .note.GNU-stack sections, and |
| 128 | // some objects files without them, this returns whether we should |
| 129 | // consider the object files without them to imply that the stack |
| 130 | // should be executable. |
| 131 | bool |
| 132 | is_default_stack_executable() const |
| 133 | { return this->pti_->is_default_stack_executable; } |
| 134 | |
| 135 | // Return a character which may appear as a prefix for a wrap |
| 136 | // symbol. If this character appears, we strip it when checking for |
| 137 | // wrapping and add it back when forming the final symbol name. |
| 138 | // This should be '\0' if not special prefix is required, which is |
| 139 | // the normal case. |
| 140 | char |
| 141 | wrap_char() const |
| 142 | { return this->pti_->wrap_char; } |
| 143 | |
| 144 | // This is called to tell the target to complete any sections it is |
| 145 | // handling. After this all sections must have their final size. |
| 146 | void |
| 147 | finalize_sections(Layout* layout) |
| 148 | { return this->do_finalize_sections(layout); } |
| 149 | |
| 150 | // Return the value to use for a global symbol which needs a special |
| 151 | // value in the dynamic symbol table. This will only be called if |
| 152 | // the backend first calls symbol->set_needs_dynsym_value(). |
| 153 | uint64_t |
| 154 | dynsym_value(const Symbol* sym) const |
| 155 | { return this->do_dynsym_value(sym); } |
| 156 | |
| 157 | // Return a string to use to fill out a code section. This is |
| 158 | // basically one or more NOPS which must fill out the specified |
| 159 | // length in bytes. |
| 160 | std::string |
| 161 | code_fill(section_size_type length) const |
| 162 | { return this->do_code_fill(length); } |
| 163 | |
| 164 | // Return whether SYM is known to be defined by the ABI. This is |
| 165 | // used to avoid inappropriate warnings about undefined symbols. |
| 166 | bool |
| 167 | is_defined_by_abi(const Symbol* sym) const |
| 168 | { return this->do_is_defined_by_abi(sym); } |
| 169 | |
| 170 | // Adjust the output file header before it is written out. VIEW |
| 171 | // points to the header in external form. LEN is the length. |
| 172 | void |
| 173 | adjust_elf_header(unsigned char* view, int len) const |
| 174 | { return this->do_adjust_elf_header(view, len); } |
| 175 | |
| 176 | protected: |
| 177 | // This struct holds the constant information for a child class. We |
| 178 | // use a struct to avoid the overhead of virtual function calls for |
| 179 | // simple information. |
| 180 | struct Target_info |
| 181 | { |
| 182 | // Address size (32 or 64). |
| 183 | int size; |
| 184 | // Whether the target is big endian. |
| 185 | bool is_big_endian; |
| 186 | // The code to store in the e_machine field of the ELF header. |
| 187 | elfcpp::EM machine_code; |
| 188 | // Whether this target has a specific make_symbol function. |
| 189 | bool has_make_symbol; |
| 190 | // Whether this target has a specific resolve function. |
| 191 | bool has_resolve; |
| 192 | // Whether this target has a specific code fill function. |
| 193 | bool has_code_fill; |
| 194 | // Whether an object file with no .note.GNU-stack sections implies |
| 195 | // that the stack should be executable. |
| 196 | bool is_default_stack_executable; |
| 197 | // Prefix character to strip when checking for wrapping. |
| 198 | char wrap_char; |
| 199 | // The default dynamic linker name. |
| 200 | const char* dynamic_linker; |
| 201 | // The default text segment address. |
| 202 | uint64_t default_text_segment_address; |
| 203 | // The ABI specified page size. |
| 204 | uint64_t abi_pagesize; |
| 205 | // The common page size used by actual implementations. |
| 206 | uint64_t common_pagesize; |
| 207 | }; |
| 208 | |
| 209 | Target(const Target_info* pti) |
| 210 | : pti_(pti) |
| 211 | { } |
| 212 | |
| 213 | // Virtual function which may be implemented by the child class. |
| 214 | virtual void |
| 215 | do_finalize_sections(Layout*) |
| 216 | { } |
| 217 | |
| 218 | // Virtual function which may be implemented by the child class. |
| 219 | virtual uint64_t |
| 220 | do_dynsym_value(const Symbol*) const |
| 221 | { gold_unreachable(); } |
| 222 | |
| 223 | // Virtual function which must be implemented by the child class if |
| 224 | // needed. |
| 225 | virtual std::string |
| 226 | do_code_fill(section_size_type) const |
| 227 | { gold_unreachable(); } |
| 228 | |
| 229 | // Virtual function which may be implemented by the child class. |
| 230 | virtual bool |
| 231 | do_is_defined_by_abi(const Symbol*) const |
| 232 | { return false; } |
| 233 | |
| 234 | // Adjust the output file header before it is written out. VIEW |
| 235 | // points to the header in external form. LEN is the length, and |
| 236 | // will be one of the values of elfcpp::Elf_sizes<size>::ehdr_size. |
| 237 | // By default, we do nothing. |
| 238 | virtual void |
| 239 | do_adjust_elf_header(unsigned char*, int) const |
| 240 | { } |
| 241 | |
| 242 | private: |
| 243 | Target(const Target&); |
| 244 | Target& operator=(const Target&); |
| 245 | |
| 246 | // The target information. |
| 247 | const Target_info* pti_; |
| 248 | }; |
| 249 | |
| 250 | // The abstract class for a specific size and endianness of target. |
| 251 | // Each actual target implementation class should derive from an |
| 252 | // instantiation of Sized_target. |
| 253 | |
| 254 | template<int size, bool big_endian> |
| 255 | class Sized_target : public Target |
| 256 | { |
| 257 | public: |
| 258 | // Make a new symbol table entry for the target. This should be |
| 259 | // overridden by a target which needs additional information in the |
| 260 | // symbol table. This will only be called if has_make_symbol() |
| 261 | // returns true. |
| 262 | virtual Sized_symbol<size>* |
| 263 | make_symbol() const |
| 264 | { gold_unreachable(); } |
| 265 | |
| 266 | // Resolve a symbol for the target. This should be overridden by a |
| 267 | // target which needs to take special action. TO is the |
| 268 | // pre-existing symbol. SYM is the new symbol, seen in OBJECT. |
| 269 | // VERSION is the version of SYM. This will only be called if |
| 270 | // has_resolve() returns true. |
| 271 | virtual void |
| 272 | resolve(Symbol*, const elfcpp::Sym<size, big_endian>&, Object*, |
| 273 | const char*) |
| 274 | { gold_unreachable(); } |
| 275 | |
| 276 | // Process the relocs for a section, and record information of the |
| 277 | // mapping from source to destination sections. This mapping is later |
| 278 | // used to determine unreferenced garbage sections. This procedure is |
| 279 | // only called during garbage collection. |
| 280 | virtual void |
| 281 | gc_process_relocs(const General_options& options, |
| 282 | Symbol_table* symtab, |
| 283 | Layout* layout, |
| 284 | Sized_relobj<size, big_endian>* object, |
| 285 | unsigned int data_shndx, |
| 286 | unsigned int sh_type, |
| 287 | const unsigned char* prelocs, |
| 288 | size_t reloc_count, |
| 289 | Output_section* output_section, |
| 290 | bool needs_special_offset_handling, |
| 291 | size_t local_symbol_count, |
| 292 | const unsigned char* plocal_symbols) = 0; |
| 293 | |
| 294 | // Scan the relocs for a section, and record any information |
| 295 | // required for the symbol. OPTIONS is the command line options. |
| 296 | // SYMTAB is the symbol table. OBJECT is the object in which the |
| 297 | // section appears. DATA_SHNDX is the section index that these |
| 298 | // relocs apply to. SH_TYPE is the type of the relocation section, |
| 299 | // SHT_REL or SHT_RELA. PRELOCS points to the relocation data. |
| 300 | // RELOC_COUNT is the number of relocs. LOCAL_SYMBOL_COUNT is the |
| 301 | // number of local symbols. OUTPUT_SECTION is the output section. |
| 302 | // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets to the output |
| 303 | // sections are not mapped as usual. PLOCAL_SYMBOLS points to the |
| 304 | // local symbol data from OBJECT. GLOBAL_SYMBOLS is the array of |
| 305 | // pointers to the global symbol table from OBJECT. |
| 306 | virtual void |
| 307 | scan_relocs(const General_options& options, |
| 308 | Symbol_table* symtab, |
| 309 | Layout* layout, |
| 310 | Sized_relobj<size, big_endian>* object, |
| 311 | unsigned int data_shndx, |
| 312 | unsigned int sh_type, |
| 313 | const unsigned char* prelocs, |
| 314 | size_t reloc_count, |
| 315 | Output_section* output_section, |
| 316 | bool needs_special_offset_handling, |
| 317 | size_t local_symbol_count, |
| 318 | const unsigned char* plocal_symbols) = 0; |
| 319 | |
| 320 | // Relocate section data. SH_TYPE is the type of the relocation |
| 321 | // section, SHT_REL or SHT_RELA. PRELOCS points to the relocation |
| 322 | // information. RELOC_COUNT is the number of relocs. |
| 323 | // OUTPUT_SECTION is the output section. |
| 324 | // NEEDS_SPECIAL_OFFSET_HANDLING is true if offsets must be mapped |
| 325 | // to correspond to the output section. VIEW is a view into the |
| 326 | // output file holding the section contents, VIEW_ADDRESS is the |
| 327 | // virtual address of the view, and VIEW_SIZE is the size of the |
| 328 | // view. If NEEDS_SPECIAL_OFFSET_HANDLING is true, the VIEW_xx |
| 329 | // parameters refer to the complete output section data, not just |
| 330 | // the input section data. |
| 331 | virtual void |
| 332 | relocate_section(const Relocate_info<size, big_endian>*, |
| 333 | unsigned int sh_type, |
| 334 | const unsigned char* prelocs, |
| 335 | size_t reloc_count, |
| 336 | Output_section* output_section, |
| 337 | bool needs_special_offset_handling, |
| 338 | unsigned char* view, |
| 339 | typename elfcpp::Elf_types<size>::Elf_Addr view_address, |
| 340 | section_size_type view_size) = 0; |
| 341 | |
| 342 | // Scan the relocs during a relocatable link. The parameters are |
| 343 | // like scan_relocs, with an additional Relocatable_relocs |
| 344 | // parameter, used to record the disposition of the relocs. |
| 345 | virtual void |
| 346 | scan_relocatable_relocs(const General_options& options, |
| 347 | Symbol_table* symtab, |
| 348 | Layout* layout, |
| 349 | Sized_relobj<size, big_endian>* object, |
| 350 | unsigned int data_shndx, |
| 351 | unsigned int sh_type, |
| 352 | const unsigned char* prelocs, |
| 353 | size_t reloc_count, |
| 354 | Output_section* output_section, |
| 355 | bool needs_special_offset_handling, |
| 356 | size_t local_symbol_count, |
| 357 | const unsigned char* plocal_symbols, |
| 358 | Relocatable_relocs*) = 0; |
| 359 | |
| 360 | // Relocate a section during a relocatable link. The parameters are |
| 361 | // like relocate_section, with additional parameters for the view of |
| 362 | // the output reloc section. |
| 363 | virtual void |
| 364 | relocate_for_relocatable(const Relocate_info<size, big_endian>*, |
| 365 | unsigned int sh_type, |
| 366 | const unsigned char* prelocs, |
| 367 | size_t reloc_count, |
| 368 | Output_section* output_section, |
| 369 | off_t offset_in_output_section, |
| 370 | const Relocatable_relocs*, |
| 371 | unsigned char* view, |
| 372 | typename elfcpp::Elf_types<size>::Elf_Addr |
| 373 | view_address, |
| 374 | section_size_type view_size, |
| 375 | unsigned char* reloc_view, |
| 376 | section_size_type reloc_view_size) = 0; |
| 377 | |
| 378 | protected: |
| 379 | Sized_target(const Target::Target_info* pti) |
| 380 | : Target(pti) |
| 381 | { |
| 382 | gold_assert(pti->size == size); |
| 383 | gold_assert(pti->is_big_endian ? big_endian : !big_endian); |
| 384 | } |
| 385 | }; |
| 386 | |
| 387 | } // End namespace gold. |
| 388 | |
| 389 | #endif // !defined(GOLD_TARGET_H) |