| 1 | // merge.h -- handle section merging for gold -*- C++ -*- |
| 2 | |
| 3 | // Copyright 2006, 2007, 2008 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 | #ifndef GOLD_MERGE_H |
| 24 | #define GOLD_MERGE_H |
| 25 | |
| 26 | #include <climits> |
| 27 | #include <map> |
| 28 | #include <vector> |
| 29 | |
| 30 | #include "stringpool.h" |
| 31 | #include "output.h" |
| 32 | |
| 33 | namespace gold |
| 34 | { |
| 35 | |
| 36 | class Merge_map; |
| 37 | |
| 38 | // For each object with merge sections, we store an Object_merge_map. |
| 39 | // This is used to map locations in input sections to a merged output |
| 40 | // section. The output section itself is not recorded here--it can be |
| 41 | // found in the output_sections_ field of the Object. |
| 42 | |
| 43 | class Object_merge_map |
| 44 | { |
| 45 | public: |
| 46 | Object_merge_map() |
| 47 | : first_shnum_(-1U), first_map_(), |
| 48 | second_shnum_(-1U), second_map_(), |
| 49 | section_merge_maps_() |
| 50 | { } |
| 51 | |
| 52 | ~Object_merge_map(); |
| 53 | |
| 54 | // Add a mapping for MERGE_MAP, for the bytes from OFFSET to OFFSET |
| 55 | // + LENGTH in the input section SHNDX to OUTPUT_OFFSET in the |
| 56 | // output section. An OUTPUT_OFFSET of -1 means that the bytes are |
| 57 | // discarded. OUTPUT_OFFSET is relative to the start of the merged |
| 58 | // data in the output section. |
| 59 | void |
| 60 | add_mapping(const Merge_map*, unsigned int shndx, section_offset_type offset, |
| 61 | section_size_type length, section_offset_type output_offset); |
| 62 | |
| 63 | // Get the output offset for an input address. MERGE_MAP is the map |
| 64 | // we are looking for, or NULL if we don't care. The input address |
| 65 | // is at offset OFFSET in section SHNDX. This sets *OUTPUT_OFFSET |
| 66 | // to the offset in the output section; this will be -1 if the bytes |
| 67 | // are not being copied to the output. This returns true if the |
| 68 | // mapping is known, false otherwise. *OUTPUT_OFFSET is relative to |
| 69 | // the start of the merged data in the output section. |
| 70 | bool |
| 71 | get_output_offset(const Merge_map*, unsigned int shndx, |
| 72 | section_offset_type offset, |
| 73 | section_offset_type *output_offset); |
| 74 | |
| 75 | // Return whether this is the merge map for section SHNDX. |
| 76 | bool |
| 77 | is_merge_section_for(const Merge_map*, unsigned int shndx); |
| 78 | |
| 79 | // Initialize an mapping from input offsets to output addresses for |
| 80 | // section SHNDX. STARTING_ADDRESS is the output address of the |
| 81 | // merged section. |
| 82 | template<int size> |
| 83 | void |
| 84 | initialize_input_to_output_map( |
| 85 | unsigned int shndx, |
| 86 | typename elfcpp::Elf_types<size>::Elf_Addr starting_address, |
| 87 | Unordered_map<section_offset_type, |
| 88 | typename elfcpp::Elf_types<size>::Elf_Addr>*); |
| 89 | |
| 90 | private: |
| 91 | // Map input section offsets to a length and an output section |
| 92 | // offset. An output section offset of -1 means that this part of |
| 93 | // the input section is being discarded. |
| 94 | struct Input_merge_entry |
| 95 | { |
| 96 | // The offset in the input section. |
| 97 | section_offset_type input_offset; |
| 98 | // The length. |
| 99 | section_size_type length; |
| 100 | // The offset in the output section. |
| 101 | section_offset_type output_offset; |
| 102 | }; |
| 103 | |
| 104 | // A less-than comparison routine for Input_merge_entry. |
| 105 | struct Input_merge_compare |
| 106 | { |
| 107 | bool |
| 108 | operator()(const Input_merge_entry& i1, const Input_merge_entry& i2) const |
| 109 | { return i1.input_offset < i2.input_offset; } |
| 110 | }; |
| 111 | |
| 112 | // A list of entries for a particular input section. |
| 113 | struct Input_merge_map |
| 114 | { |
| 115 | typedef std::vector<Input_merge_entry> Entries; |
| 116 | |
| 117 | // We store these with the Relobj, and we look them up by input |
| 118 | // section. It is possible to have two different merge maps |
| 119 | // associated with a single output section. For example, this |
| 120 | // happens routinely with .rodata, when merged string constants |
| 121 | // and merged fixed size constants are both put into .rodata. The |
| 122 | // output offset that we store is not the offset from the start of |
| 123 | // the output section; it is the offset from the start of the |
| 124 | // merged data in the output section. That means that the caller |
| 125 | // is going to add the offset of the merged data within the output |
| 126 | // section, which means that the caller needs to know which set of |
| 127 | // merged data it found the entry in. So it's not enough to find |
| 128 | // this data based on the input section and the output section; we |
| 129 | // also have to find it based on a set of merged data in the |
| 130 | // output section. In order to verify that we are looking at the |
| 131 | // right data, we store a pointer to the Merge_map here, and we |
| 132 | // pass in a pointer when looking at the data. If we are asked to |
| 133 | // look up information for a different Merge_map, we report that |
| 134 | // we don't have it, rather than trying a lookup and returning an |
| 135 | // answer which will receive the wrong offset. |
| 136 | const Merge_map* merge_map; |
| 137 | // The list of mappings. |
| 138 | Entries entries; |
| 139 | // Whether the ENTRIES field is sorted by input_offset. |
| 140 | bool sorted; |
| 141 | |
| 142 | Input_merge_map() |
| 143 | : merge_map(NULL), entries(), sorted(true) |
| 144 | { } |
| 145 | }; |
| 146 | |
| 147 | // Map input section indices to merge maps. |
| 148 | typedef std::map<unsigned int, Input_merge_map*> Section_merge_maps; |
| 149 | |
| 150 | // Return a pointer to the Input_merge_map to use for the input |
| 151 | // section SHNDX, or NULL. |
| 152 | Input_merge_map* |
| 153 | get_input_merge_map(unsigned int shndx); |
| 154 | |
| 155 | // Get or make the the Input_merge_map to use for the section SHNDX |
| 156 | // with MERGE_MAP. |
| 157 | Input_merge_map* |
| 158 | get_or_make_input_merge_map(const Merge_map* merge_map, unsigned int shndx); |
| 159 | |
| 160 | // Any given object file will normally only have a couple of input |
| 161 | // sections with mergeable contents. So we keep the first two input |
| 162 | // section numbers inline, and push any further ones into a map. A |
| 163 | // value of -1U in first_shnum_ or second_shnum_ means that we don't |
| 164 | // have a corresponding entry. |
| 165 | unsigned int first_shnum_; |
| 166 | Input_merge_map first_map_; |
| 167 | unsigned int second_shnum_; |
| 168 | Input_merge_map second_map_; |
| 169 | Section_merge_maps section_merge_maps_; |
| 170 | }; |
| 171 | |
| 172 | // This class manages mappings from input sections to offsets in an |
| 173 | // output section. This is used where input sections are merged. The |
| 174 | // actual data is stored in fields in Object. |
| 175 | |
| 176 | class Merge_map |
| 177 | { |
| 178 | public: |
| 179 | Merge_map() |
| 180 | { } |
| 181 | |
| 182 | // Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in the |
| 183 | // input section SHNDX in object OBJECT to OUTPUT_OFFSET in the |
| 184 | // output section. An OUTPUT_OFFSET of -1 means that the bytes are |
| 185 | // discarded. OUTPUT_OFFSET is not the offset from the start of the |
| 186 | // output section, it is the offset from the start of the merged |
| 187 | // data within the output section. |
| 188 | void |
| 189 | add_mapping(Relobj* object, unsigned int shndx, |
| 190 | section_offset_type offset, section_size_type length, |
| 191 | section_offset_type output_offset); |
| 192 | |
| 193 | // Return the output offset for an input address. The input address |
| 194 | // is at offset OFFSET in section SHNDX in OBJECT. This sets |
| 195 | // *OUTPUT_OFFSET to the offset in the output section; this will be |
| 196 | // -1 if the bytes are not being copied to the output. This returns |
| 197 | // true if the mapping is known, false otherwise. This returns the |
| 198 | // value stored by add_mapping, namely the offset from the start of |
| 199 | // the merged data within the output section. |
| 200 | bool |
| 201 | get_output_offset(const Relobj* object, unsigned int shndx, |
| 202 | section_offset_type offset, |
| 203 | section_offset_type *output_offset) const; |
| 204 | |
| 205 | // Return whether this is the merge mapping for section SHNDX in |
| 206 | // OBJECT. This should return true when get_output_offset would |
| 207 | // return true for some input offset. |
| 208 | bool |
| 209 | is_merge_section_for(const Relobj* object, unsigned int shndx) const; |
| 210 | }; |
| 211 | |
| 212 | // A general class for SHF_MERGE data, to hold functions shared by |
| 213 | // fixed-size constant data and string data. |
| 214 | |
| 215 | class Output_merge_base : public Output_section_data |
| 216 | { |
| 217 | public: |
| 218 | Output_merge_base(uint64_t entsize, uint64_t addralign) |
| 219 | : Output_section_data(addralign), merge_map_(), entsize_(entsize) |
| 220 | { } |
| 221 | |
| 222 | protected: |
| 223 | // Return the output offset for an input offset. |
| 224 | bool |
| 225 | do_output_offset(const Relobj* object, unsigned int shndx, |
| 226 | section_offset_type offset, |
| 227 | section_offset_type* poutput) const; |
| 228 | |
| 229 | // Return whether this is the merge section for an input section. |
| 230 | bool |
| 231 | do_is_merge_section_for(const Relobj*, unsigned int shndx) const; |
| 232 | |
| 233 | // Return the entry size. |
| 234 | uint64_t |
| 235 | entsize() const |
| 236 | { return this->entsize_; } |
| 237 | |
| 238 | // Add a mapping from an OFFSET in input section SHNDX in object |
| 239 | // OBJECT to an OUTPUT_OFFSET in the output section. OUTPUT_OFFSET |
| 240 | // is the offset from the start of the merged data in the output |
| 241 | // section. |
| 242 | void |
| 243 | add_mapping(Relobj* object, unsigned int shndx, section_offset_type offset, |
| 244 | section_size_type length, section_offset_type output_offset) |
| 245 | { |
| 246 | this->merge_map_.add_mapping(object, shndx, offset, length, output_offset); |
| 247 | } |
| 248 | |
| 249 | private: |
| 250 | // A mapping from input object/section/offset to offset in output |
| 251 | // section. |
| 252 | Merge_map merge_map_; |
| 253 | // The entry size. For fixed-size constants, this is the size of |
| 254 | // the constants. For strings, this is the size of a character. |
| 255 | uint64_t entsize_; |
| 256 | }; |
| 257 | |
| 258 | // Handle SHF_MERGE sections with fixed-size constant data. |
| 259 | |
| 260 | class Output_merge_data : public Output_merge_base |
| 261 | { |
| 262 | public: |
| 263 | Output_merge_data(uint64_t entsize, uint64_t addralign) |
| 264 | : Output_merge_base(entsize, addralign), p_(NULL), len_(0), alc_(0), |
| 265 | input_count_(0), |
| 266 | hashtable_(128, Merge_data_hash(this), Merge_data_eq(this)) |
| 267 | { } |
| 268 | |
| 269 | protected: |
| 270 | // Add an input section. |
| 271 | bool |
| 272 | do_add_input_section(Relobj* object, unsigned int shndx); |
| 273 | |
| 274 | // Set the final data size. |
| 275 | void |
| 276 | set_final_data_size(); |
| 277 | |
| 278 | // Write the data to the file. |
| 279 | void |
| 280 | do_write(Output_file*); |
| 281 | |
| 282 | // Write the data to a buffer. |
| 283 | void |
| 284 | do_write_to_buffer(unsigned char*); |
| 285 | |
| 286 | // Write to a map file. |
| 287 | void |
| 288 | do_print_to_mapfile(Mapfile* mapfile) const |
| 289 | { mapfile->print_output_data(this, _("** merge constants")); } |
| 290 | |
| 291 | // Print merge stats to stderr. |
| 292 | void |
| 293 | do_print_merge_stats(const char* section_name); |
| 294 | |
| 295 | private: |
| 296 | // We build a hash table of the fixed-size constants. Each constant |
| 297 | // is stored as a pointer into the section data we are accumulating. |
| 298 | |
| 299 | // A key in the hash table. This is an offset in the section |
| 300 | // contents we are building. |
| 301 | typedef section_offset_type Merge_data_key; |
| 302 | |
| 303 | // Compute the hash code. To do this we need a pointer back to the |
| 304 | // object holding the data. |
| 305 | class Merge_data_hash |
| 306 | { |
| 307 | public: |
| 308 | Merge_data_hash(const Output_merge_data* pomd) |
| 309 | : pomd_(pomd) |
| 310 | { } |
| 311 | |
| 312 | size_t |
| 313 | operator()(Merge_data_key) const; |
| 314 | |
| 315 | private: |
| 316 | const Output_merge_data* pomd_; |
| 317 | }; |
| 318 | |
| 319 | friend class Merge_data_hash; |
| 320 | |
| 321 | // Compare two entries in the hash table for equality. To do this |
| 322 | // we need a pointer back to the object holding the data. Note that |
| 323 | // we now have a pointer to the object stored in two places in the |
| 324 | // hash table. Fixing this would require specializing the hash |
| 325 | // table, which would be hard to do portably. |
| 326 | class Merge_data_eq |
| 327 | { |
| 328 | public: |
| 329 | Merge_data_eq(const Output_merge_data* pomd) |
| 330 | : pomd_(pomd) |
| 331 | { } |
| 332 | |
| 333 | bool |
| 334 | operator()(Merge_data_key k1, Merge_data_key k2) const; |
| 335 | |
| 336 | private: |
| 337 | const Output_merge_data* pomd_; |
| 338 | }; |
| 339 | |
| 340 | friend class Merge_data_eq; |
| 341 | |
| 342 | // The type of the hash table. |
| 343 | typedef Unordered_set<Merge_data_key, Merge_data_hash, Merge_data_eq> |
| 344 | Merge_data_hashtable; |
| 345 | |
| 346 | // Given a hash table key, which is just an offset into the section |
| 347 | // data, return a pointer to the corresponding constant. |
| 348 | const unsigned char* |
| 349 | constant(Merge_data_key k) const |
| 350 | { |
| 351 | gold_assert(k >= 0 && k < static_cast<section_offset_type>(this->len_)); |
| 352 | return this->p_ + k; |
| 353 | } |
| 354 | |
| 355 | // Add a constant to the output. |
| 356 | void |
| 357 | add_constant(const unsigned char*); |
| 358 | |
| 359 | // The accumulated data. |
| 360 | unsigned char* p_; |
| 361 | // The length of the accumulated data. |
| 362 | section_size_type len_; |
| 363 | // The size of the allocated buffer. |
| 364 | section_size_type alc_; |
| 365 | // The number of entries seen in input files. |
| 366 | size_t input_count_; |
| 367 | // The hash table. |
| 368 | Merge_data_hashtable hashtable_; |
| 369 | }; |
| 370 | |
| 371 | // Handle SHF_MERGE sections with string data. This is a template |
| 372 | // based on the type of the characters in the string. |
| 373 | |
| 374 | template<typename Char_type> |
| 375 | class Output_merge_string : public Output_merge_base |
| 376 | { |
| 377 | public: |
| 378 | Output_merge_string(uint64_t addralign) |
| 379 | : Output_merge_base(sizeof(Char_type), addralign), stringpool_(), |
| 380 | merged_strings_(), input_count_(0) |
| 381 | { |
| 382 | gold_assert(addralign <= sizeof(Char_type)); |
| 383 | this->stringpool_.set_no_zero_null(); |
| 384 | } |
| 385 | |
| 386 | protected: |
| 387 | // Add an input section. |
| 388 | bool |
| 389 | do_add_input_section(Relobj* object, unsigned int shndx); |
| 390 | |
| 391 | // Do all the final processing after the input sections are read in. |
| 392 | // Returns the final data size. |
| 393 | section_size_type |
| 394 | finalize_merged_data(); |
| 395 | |
| 396 | // Set the final data size. |
| 397 | void |
| 398 | set_final_data_size(); |
| 399 | |
| 400 | // Write the data to the file. |
| 401 | void |
| 402 | do_write(Output_file*); |
| 403 | |
| 404 | // Write the data to a buffer. |
| 405 | void |
| 406 | do_write_to_buffer(unsigned char*); |
| 407 | |
| 408 | // Write to a map file. |
| 409 | void |
| 410 | do_print_to_mapfile(Mapfile* mapfile) const |
| 411 | { mapfile->print_output_data(this, _("** merge strings")); } |
| 412 | |
| 413 | // Print merge stats to stderr. |
| 414 | void |
| 415 | do_print_merge_stats(const char* section_name); |
| 416 | |
| 417 | // Writes the stringpool to a buffer. |
| 418 | void |
| 419 | stringpool_to_buffer(unsigned char* buffer, section_size_type buffer_size) |
| 420 | { this->stringpool_.write_to_buffer(buffer, buffer_size); } |
| 421 | |
| 422 | // Clears all the data in the stringpool, to save on memory. |
| 423 | void |
| 424 | clear_stringpool() |
| 425 | { this->stringpool_.clear(); } |
| 426 | |
| 427 | private: |
| 428 | // The name of the string type, for stats. |
| 429 | const char* |
| 430 | string_name(); |
| 431 | |
| 432 | // As we see input sections, we build a mapping from object, section |
| 433 | // index and offset to strings. |
| 434 | struct Merged_string |
| 435 | { |
| 436 | // The input object where the string was found. |
| 437 | Relobj* object; |
| 438 | // The input section in the input object. |
| 439 | unsigned int shndx; |
| 440 | // The offset in the input section. |
| 441 | section_offset_type offset; |
| 442 | // The string itself, a pointer into a Stringpool. |
| 443 | const Char_type* string; |
| 444 | // The length of the string in bytes, including the null terminator. |
| 445 | size_t length; |
| 446 | // The key in the Stringpool. |
| 447 | Stringpool::Key stringpool_key; |
| 448 | |
| 449 | Merged_string(Relobj *objecta, unsigned int shndxa, |
| 450 | section_offset_type offseta, const Char_type* stringa, |
| 451 | size_t lengtha, Stringpool::Key stringpool_keya) |
| 452 | : object(objecta), shndx(shndxa), offset(offseta), string(stringa), |
| 453 | length(lengtha), stringpool_key(stringpool_keya) |
| 454 | { } |
| 455 | }; |
| 456 | |
| 457 | typedef std::vector<Merged_string> Merged_strings; |
| 458 | |
| 459 | // As we see the strings, we add them to a Stringpool. |
| 460 | Stringpool_template<Char_type> stringpool_; |
| 461 | // Map from a location in an input object to an entry in the |
| 462 | // Stringpool. |
| 463 | Merged_strings merged_strings_; |
| 464 | // The number of entries seen in input files. |
| 465 | size_t input_count_; |
| 466 | }; |
| 467 | |
| 468 | } // End namespace gold. |
| 469 | |
| 470 | #endif // !defined(GOLD_MERGE_H) |