1// stringpool.cc -- a string pool for gold 2 3// Copyright (C) 2006-2017 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 <cstring> 26#include <algorithm> 27#include <vector> 28 29#include "output.h" 30#include "parameters.h" 31#include "stringpool.h" 32 33namespace gold 34{ 35 36template<typename Stringpool_char> 37Stringpool_template<Stringpool_char>::Stringpool_template(uint64_t addralign) 38 : string_set_(), key_to_offset_(), strings_(), strtab_size_(0), 39 zero_null_(true), optimize_(false), offset_(sizeof(Stringpool_char)), 40 addralign_(addralign) 41{ 42 if (parameters->options_valid() 43 && parameters->options().optimize() >= 2 44 && addralign <= sizeof(Stringpool_char)) 45 this->optimize_ = true; 46} 47 48template<typename Stringpool_char> 49void 50Stringpool_template<Stringpool_char>::clear() 51{ 52 for (typename std::list<Stringdata*>::iterator p = this->strings_.begin(); 53 p != this->strings_.end(); 54 ++p) 55 delete[] reinterpret_cast<char*>(*p); 56 this->strings_.clear(); 57 this->key_to_offset_.clear(); 58 this->string_set_.clear(); 59} 60 61template<typename Stringpool_char> 62Stringpool_template<Stringpool_char>::~Stringpool_template() 63{ 64 this->clear(); 65} 66 67// Resize the internal hashtable with the expectation we'll get n new 68// elements. Note that the hashtable constructor takes a "number of 69// buckets you'd like," rather than "number of elements you'd like," 70// but that's the best we can do. 71 72template<typename Stringpool_char> 73void 74Stringpool_template<Stringpool_char>::reserve(unsigned int n) 75{ 76 this->key_to_offset_.reserve(n); 77 78#if defined(HAVE_UNORDERED_MAP) 79 this->string_set_.rehash(this->string_set_.size() + n); 80 return; 81#elif defined(HAVE_TR1_UNORDERED_MAP) 82 // rehash() implementation is broken in gcc 4.0.3's stl 83 //this->string_set_.rehash(this->string_set_.size() + n); 84 //return; 85#elif defined(HAVE_EXT_HASH_MAP) 86 this->string_set_.resize(this->string_set_.size() + n); 87 return; 88#endif 89 90 // This is the generic "reserve" code, if no #ifdef above triggers. 91 String_set_type new_string_set(this->string_set_.size() + n); 92 new_string_set.insert(this->string_set_.begin(), this->string_set_.end()); 93 this->string_set_.swap(new_string_set); 94} 95 96// Compare two strings of arbitrary character type for equality. 97 98template<typename Stringpool_char> 99bool 100Stringpool_template<Stringpool_char>::string_equal(const Stringpool_char* s1, 101 const Stringpool_char* s2) 102{ 103 while (*s1 != 0) 104 if (*s1++ != *s2++) 105 return false; 106 return *s2 == 0; 107} 108 109// Specialize string_equal for char. 110 111template<> 112inline bool 113Stringpool_template<char>::string_equal(const char* s1, const char* s2) 114{ 115 return strcmp(s1, s2) == 0; 116} 117 118// Equality comparison function for the hash table. 119 120template<typename Stringpool_char> 121inline bool 122Stringpool_template<Stringpool_char>::Stringpool_eq::operator()( 123 const Hashkey& h1, 124 const Hashkey& h2) const 125{ 126 return (h1.hash_code == h2.hash_code 127 && h1.length == h2.length 128 && (h1.string == h2.string 129 || memcmp(h1.string, h2.string, 130 h1.length * sizeof(Stringpool_char)) == 0)); 131} 132 133// Hash function. The length is in characters, not bytes. 134 135template<typename Stringpool_char> 136size_t 137Stringpool_template<Stringpool_char>::string_hash(const Stringpool_char* s, 138 size_t length) 139{ 140 return gold::string_hash<Stringpool_char>(s, length); 141} 142 143// Add the string S to the list of canonical strings. Return a 144// pointer to the canonical string. If PKEY is not NULL, set *PKEY to 145// the key. LENGTH is the length of S in characters. Note that S may 146// not be NUL terminated. 147 148template<typename Stringpool_char> 149const Stringpool_char* 150Stringpool_template<Stringpool_char>::add_string(const Stringpool_char* s, 151 size_t len) 152{ 153 // We are in trouble if we've already computed the string offsets. 154 gold_assert(this->strtab_size_ == 0); 155 156 // The size we allocate for a new Stringdata. 157 const size_t buffer_size = 1000; 158 // The amount we multiply the Stringdata index when calculating the 159 // key. 160 const size_t key_mult = 1024; 161 gold_assert(key_mult >= buffer_size); 162 163 // Convert len to the number of bytes we need to allocate, including 164 // the null character. 165 len = (len + 1) * sizeof(Stringpool_char); 166 167 size_t alc; 168 bool front = true; 169 if (len > buffer_size) 170 { 171 alc = sizeof(Stringdata) + len; 172 front = false; 173 } 174 else if (this->strings_.empty()) 175 alc = sizeof(Stringdata) + buffer_size; 176 else 177 { 178 Stringdata* psd = this->strings_.front(); 179 if (len > psd->alc - psd->len) 180 alc = sizeof(Stringdata) + buffer_size; 181 else 182 { 183 char* ret = psd->data + psd->len; 184 memcpy(ret, s, len - sizeof(Stringpool_char)); 185 memset(ret + len - sizeof(Stringpool_char), 0, 186 sizeof(Stringpool_char)); 187 188 psd->len += len; 189 190 return reinterpret_cast<const Stringpool_char*>(ret); 191 } 192 } 193 194 Stringdata* psd = reinterpret_cast<Stringdata*>(new char[alc]); 195 psd->alc = alc - sizeof(Stringdata); 196 memcpy(psd->data, s, len - sizeof(Stringpool_char)); 197 memset(psd->data + len - sizeof(Stringpool_char), 0, 198 sizeof(Stringpool_char)); 199 psd->len = len; 200 201 if (front) 202 this->strings_.push_front(psd); 203 else 204 this->strings_.push_back(psd); 205 206 return reinterpret_cast<const Stringpool_char*>(psd->data); 207} 208 209// Add a string to a string pool. 210 211template<typename Stringpool_char> 212const Stringpool_char* 213Stringpool_template<Stringpool_char>::add(const Stringpool_char* s, bool copy, 214 Key* pkey) 215{ 216 return this->add_with_length(s, string_length(s), copy, pkey); 217} 218 219// Add a new key offset entry. 220 221template<typename Stringpool_char> 222void 223Stringpool_template<Stringpool_char>::new_key_offset(size_t length) 224{ 225 section_offset_type offset; 226 if (this->zero_null_ && length == 0) 227 offset = 0; 228 else 229 { 230 offset = this->offset_; 231 // Align strings. 232 offset = align_address(offset, this->addralign_); 233 this->offset_ = offset + (length + 1) * sizeof(Stringpool_char); 234 } 235 this->key_to_offset_.push_back(offset); 236} 237 238template<typename Stringpool_char> 239const Stringpool_char* 240Stringpool_template<Stringpool_char>::add_with_length(const Stringpool_char* s, 241 size_t length, 242 bool copy, 243 Key* pkey) 244{ 245 typedef std::pair<typename String_set_type::iterator, bool> Insert_type; 246 247 // We add 1 so that 0 is always invalid. 248 const Key k = this->key_to_offset_.size() + 1; 249 250 if (!copy) 251 { 252 // When we don't need to copy the string, we can call insert 253 // directly. 254 255 std::pair<Hashkey, Hashval> element(Hashkey(s, length), k); 256 257 Insert_type ins = this->string_set_.insert(element); 258 259 typename String_set_type::const_iterator p = ins.first; 260 261 if (ins.second) 262 { 263 // We just added the string. The key value has now been 264 // used. 265 this->new_key_offset(length); 266 } 267 else 268 { 269 gold_assert(k != p->second); 270 } 271 272 if (pkey != NULL) 273 *pkey = p->second; 274 return p->first.string; 275 } 276 277 // When we have to copy the string, we look it up twice in the hash 278 // table. The problem is that we can't insert S before we 279 // canonicalize it by copying it into the canonical list. The hash 280 // code will only be computed once. 281 282 Hashkey hk(s, length); 283 typename String_set_type::const_iterator p = this->string_set_.find(hk); 284 if (p != this->string_set_.end()) 285 { 286 if (pkey != NULL) 287 *pkey = p->second; 288 return p->first.string; 289 } 290 291 this->new_key_offset(length); 292 293 hk.string = this->add_string(s, length); 294 // The contents of the string stay the same, so we don't need to 295 // adjust hk.hash_code or hk.length. 296 297 std::pair<Hashkey, Hashval> element(hk, k); 298 299 Insert_type ins = this->string_set_.insert(element); 300 gold_assert(ins.second); 301 302 if (pkey != NULL) 303 *pkey = k; 304 return hk.string; 305} 306 307template<typename Stringpool_char> 308const Stringpool_char* 309Stringpool_template<Stringpool_char>::find(const Stringpool_char* s, 310 Key* pkey) const 311{ 312 Hashkey hk(s); 313 typename String_set_type::const_iterator p = this->string_set_.find(hk); 314 if (p == this->string_set_.end()) 315 return NULL; 316 317 if (pkey != NULL) 318 *pkey = p->second; 319 320 return p->first.string; 321} 322 323// Comparison routine used when sorting into an ELF strtab. We want 324// to sort this so that when one string is a suffix of another, we 325// always see the shorter string immediately after the longer string. 326// For example, we want to see these strings in this order: 327// abcd 328// cd 329// d 330// When strings are not suffixes, we don't care what order they are 331// in, but we need to ensure that suffixes wind up next to each other. 332// So we do a reversed lexicographic sort on the reversed string. 333 334template<typename Stringpool_char> 335bool 336Stringpool_template<Stringpool_char>::Stringpool_sort_comparison::operator()( 337 const Stringpool_sort_info& sort_info1, 338 const Stringpool_sort_info& sort_info2) const 339{ 340 const Hashkey& h1(sort_info1->first); 341 const Hashkey& h2(sort_info2->first); 342 const Stringpool_char* s1 = h1.string; 343 const Stringpool_char* s2 = h2.string; 344 const size_t len1 = h1.length; 345 const size_t len2 = h2.length; 346 const size_t minlen = len1 < len2 ? len1 : len2; 347 const Stringpool_char* p1 = s1 + len1 - 1; 348 const Stringpool_char* p2 = s2 + len2 - 1; 349 for (size_t i = minlen; i > 0; --i, --p1, --p2) 350 { 351 if (*p1 != *p2) 352 return *p1 > *p2; 353 } 354 return len1 > len2; 355} 356 357// Return whether s1 is a suffix of s2. 358 359template<typename Stringpool_char> 360bool 361Stringpool_template<Stringpool_char>::is_suffix(const Stringpool_char* s1, 362 size_t len1, 363 const Stringpool_char* s2, 364 size_t len2) 365{ 366 if (len1 > len2) 367 return false; 368 return memcmp(s1, s2 + len2 - len1, len1 * sizeof(Stringpool_char)) == 0; 369} 370 371// Turn the stringpool into an ELF strtab: determine the offsets of 372// each string in the table. 373 374template<typename Stringpool_char> 375void 376Stringpool_template<Stringpool_char>::set_string_offsets() 377{ 378 if (this->strtab_size_ != 0) 379 { 380 // We've already computed the offsets. 381 return; 382 } 383 384 const size_t charsize = sizeof(Stringpool_char); 385 386 // Offset 0 may be reserved for the empty string. 387 section_offset_type offset = this->zero_null_ ? charsize : 0; 388 389 // Sorting to find suffixes can take over 25% of the total CPU time 390 // used by the linker. Since it's merely an optimization to reduce 391 // the strtab size, and gives a relatively small benefit (it's 392 // typically rare for a symbol to be a suffix of another), we only 393 // take the time to sort when the user asks for heavy optimization. 394 if (!this->optimize_) 395 { 396 // If we are not optimizing, the offsets are already assigned. 397 offset = this->offset_; 398 } 399 else 400 { 401 size_t count = this->string_set_.size(); 402 403 std::vector<Stringpool_sort_info> v; 404 v.reserve(count); 405 406 for (typename String_set_type::iterator p = this->string_set_.begin(); 407 p != this->string_set_.end(); 408 ++p) 409 v.push_back(Stringpool_sort_info(p)); 410 411 std::sort(v.begin(), v.end(), Stringpool_sort_comparison()); 412 413 section_offset_type last_offset = -1; 414 for (typename std::vector<Stringpool_sort_info>::iterator last = v.end(), 415 curr = v.begin(); 416 curr != v.end(); 417 last = curr++) 418 { 419 section_offset_type this_offset; 420 if (this->zero_null_ && (*curr)->first.string[0] == 0) 421 this_offset = 0; 422 else if (last != v.end() 423 && ((((*curr)->first.length - (*last)->first.length) 424 % this->addralign_) == 0) 425 && is_suffix((*curr)->first.string, 426 (*curr)->first.length, 427 (*last)->first.string, 428 (*last)->first.length)) 429 this_offset = (last_offset 430 + (((*last)->first.length - (*curr)->first.length) 431 * charsize)); 432 else 433 { 434 this_offset = align_address(offset, this->addralign_); 435 offset = this_offset + ((*curr)->first.length + 1) * charsize; 436 } 437 this->key_to_offset_[(*curr)->second - 1] = this_offset; 438 last_offset = this_offset; 439 } 440 } 441 442 this->strtab_size_ = offset; 443} 444 445// Get the offset of a string in the ELF strtab. The string must 446// exist. 447 448template<typename Stringpool_char> 449section_offset_type 450Stringpool_template<Stringpool_char>::get_offset(const Stringpool_char* s) 451 const 452{ 453 return this->get_offset_with_length(s, string_length(s)); 454} 455 456template<typename Stringpool_char> 457section_offset_type 458Stringpool_template<Stringpool_char>::get_offset_with_length( 459 const Stringpool_char* s, 460 size_t length) const 461{ 462 gold_assert(this->strtab_size_ != 0); 463 Hashkey hk(s, length); 464 typename String_set_type::const_iterator p = this->string_set_.find(hk); 465 if (p != this->string_set_.end()) 466 return this->key_to_offset_[p->second - 1]; 467 gold_unreachable(); 468} 469 470// Write the ELF strtab into the buffer. 471 472template<typename Stringpool_char> 473void 474Stringpool_template<Stringpool_char>::write_to_buffer( 475 unsigned char* buffer, 476 section_size_type bufsize) 477{ 478 gold_assert(this->strtab_size_ != 0); 479 gold_assert(bufsize >= this->strtab_size_); 480 if (this->zero_null_) 481 buffer[0] = '\0'; 482 for (typename String_set_type::const_iterator p = this->string_set_.begin(); 483 p != this->string_set_.end(); 484 ++p) 485 { 486 const int len = (p->first.length + 1) * sizeof(Stringpool_char); 487 const section_offset_type offset = this->key_to_offset_[p->second - 1]; 488 gold_assert(static_cast<section_size_type>(offset) + len 489 <= this->strtab_size_); 490 memcpy(buffer + offset, p->first.string, len); 491 } 492} 493 494// Write the ELF strtab into the output file at the specified offset. 495 496template<typename Stringpool_char> 497void 498Stringpool_template<Stringpool_char>::write(Output_file* of, off_t offset) 499{ 500 gold_assert(this->strtab_size_ != 0); 501 unsigned char* view = of->get_output_view(offset, this->strtab_size_); 502 this->write_to_buffer(view, this->strtab_size_); 503 of->write_output_view(offset, this->strtab_size_, view); 504} 505 506// Print statistical information to stderr. This is used for --stats. 507 508template<typename Stringpool_char> 509void 510Stringpool_template<Stringpool_char>::print_stats(const char* name) const 511{ 512#if defined(HAVE_UNORDERED_MAP) || defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP) 513 fprintf(stderr, _("%s: %s entries: %zu; buckets: %zu\n"), 514 program_name, name, this->string_set_.size(), 515 this->string_set_.bucket_count()); 516#else 517 fprintf(stderr, _("%s: %s entries: %zu\n"), 518 program_name, name, this->table_.size()); 519#endif 520 fprintf(stderr, _("%s: %s Stringdata structures: %zu\n"), 521 program_name, name, this->strings_.size()); 522} 523 524// Instantiate the templates we need. 525 526template 527class Stringpool_template<char>; 528 529template 530class Stringpool_template<uint16_t>; 531 532template 533class Stringpool_template<uint32_t>; 534 535} // End namespace gold. 536