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1 | // stringpool.cc -- a string pool for gold | |
2 | ||
3 | // Copyright (C) 2006-2020 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 | ||
33 | namespace gold | |
34 | { | |
35 | ||
36 | template<typename Stringpool_char> | |
37 | Stringpool_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 | ||
48 | template<typename Stringpool_char> | |
49 | void | |
50 | Stringpool_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 | ||
61 | template<typename Stringpool_char> | |
62 | Stringpool_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 | ||
72 | template<typename Stringpool_char> | |
73 | void | |
74 | Stringpool_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 | ||
98 | template<typename Stringpool_char> | |
99 | bool | |
100 | Stringpool_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 | ||
111 | template<> | |
112 | inline bool | |
113 | Stringpool_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 | ||
120 | template<typename Stringpool_char> | |
121 | inline bool | |
122 | Stringpool_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 | ||
135 | template<typename Stringpool_char> | |
136 | size_t | |
137 | Stringpool_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 | ||
148 | template<typename Stringpool_char> | |
149 | const Stringpool_char* | |
150 | Stringpool_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 | ||
211 | template<typename Stringpool_char> | |
212 | const Stringpool_char* | |
213 | Stringpool_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 | ||
221 | template<typename Stringpool_char> | |
222 | void | |
223 | Stringpool_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 | ||
238 | template<typename Stringpool_char> | |
239 | const Stringpool_char* | |
240 | Stringpool_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 | ||
307 | template<typename Stringpool_char> | |
308 | const Stringpool_char* | |
309 | Stringpool_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 | ||
334 | template<typename Stringpool_char> | |
335 | bool | |
336 | Stringpool_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 | ||
359 | template<typename Stringpool_char> | |
360 | bool | |
361 | Stringpool_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 | ||
374 | template<typename Stringpool_char> | |
375 | void | |
376 | Stringpool_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 | ||
448 | template<typename Stringpool_char> | |
449 | section_offset_type | |
450 | Stringpool_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 | ||
456 | template<typename Stringpool_char> | |
457 | section_offset_type | |
458 | Stringpool_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 | ||
472 | template<typename Stringpool_char> | |
473 | void | |
474 | Stringpool_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 | ||
496 | template<typename Stringpool_char> | |
497 | void | |
498 | Stringpool_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 | ||
508 | template<typename Stringpool_char> | |
509 | void | |
510 | Stringpool_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 | ||
526 | template | |
527 | class Stringpool_template<char>; | |
528 | ||
529 | template | |
530 | class Stringpool_template<uint16_t>; | |
531 | ||
532 | template | |
533 | class Stringpool_template<uint32_t>; | |
534 | ||
535 | } // End namespace gold. |