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1 | /* ELF strtab with GC and suffix merging support. | |
2 | Copyright (C) 2001-2020 Free Software Foundation, Inc. | |
3 | Written by Jakub Jelinek <jakub@redhat.com>. | |
4 | ||
5 | This file is part of BFD, the Binary File Descriptor library. | |
6 | ||
7 | This program is free software; you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation; either version 3 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | This program is distributed in the hope that it will be useful, | |
13 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
15 | GNU General Public License for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with this program; if not, write to the Free Software | |
19 | Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, | |
20 | MA 02110-1301, USA. */ | |
21 | ||
22 | #include "sysdep.h" | |
23 | #include "bfd.h" | |
24 | #include "libbfd.h" | |
25 | #include "elf-bfd.h" | |
26 | #include "hashtab.h" | |
27 | #include "libiberty.h" | |
28 | ||
29 | /* An entry in the strtab hash table. */ | |
30 | ||
31 | struct elf_strtab_hash_entry | |
32 | { | |
33 | struct bfd_hash_entry root; | |
34 | /* Length of this entry. This includes the zero terminator. */ | |
35 | int len; | |
36 | unsigned int refcount; | |
37 | union { | |
38 | /* Index within the merged section. */ | |
39 | bfd_size_type index; | |
40 | /* Entry this is a suffix of (if len < 0). */ | |
41 | struct elf_strtab_hash_entry *suffix; | |
42 | } u; | |
43 | }; | |
44 | ||
45 | /* The strtab hash table. */ | |
46 | ||
47 | struct elf_strtab_hash | |
48 | { | |
49 | struct bfd_hash_table table; | |
50 | /* Next available index. */ | |
51 | size_t size; | |
52 | /* Number of array entries alloced. */ | |
53 | size_t alloced; | |
54 | /* Final strtab size. */ | |
55 | bfd_size_type sec_size; | |
56 | /* Array of pointers to strtab entries. */ | |
57 | struct elf_strtab_hash_entry **array; | |
58 | }; | |
59 | ||
60 | /* Routine to create an entry in a section merge hashtab. */ | |
61 | ||
62 | static struct bfd_hash_entry * | |
63 | elf_strtab_hash_newfunc (struct bfd_hash_entry *entry, | |
64 | struct bfd_hash_table *table, | |
65 | const char *string) | |
66 | { | |
67 | /* Allocate the structure if it has not already been allocated by a | |
68 | subclass. */ | |
69 | if (entry == NULL) | |
70 | entry = (struct bfd_hash_entry *) | |
71 | bfd_hash_allocate (table, sizeof (struct elf_strtab_hash_entry)); | |
72 | if (entry == NULL) | |
73 | return NULL; | |
74 | ||
75 | /* Call the allocation method of the superclass. */ | |
76 | entry = bfd_hash_newfunc (entry, table, string); | |
77 | ||
78 | if (entry) | |
79 | { | |
80 | /* Initialize the local fields. */ | |
81 | struct elf_strtab_hash_entry *ret; | |
82 | ||
83 | ret = (struct elf_strtab_hash_entry *) entry; | |
84 | ret->u.index = -1; | |
85 | ret->refcount = 0; | |
86 | ret->len = 0; | |
87 | } | |
88 | ||
89 | return entry; | |
90 | } | |
91 | ||
92 | /* Create a new hash table. */ | |
93 | ||
94 | struct elf_strtab_hash * | |
95 | _bfd_elf_strtab_init (void) | |
96 | { | |
97 | struct elf_strtab_hash *table; | |
98 | size_t amt = sizeof (struct elf_strtab_hash); | |
99 | ||
100 | table = (struct elf_strtab_hash *) bfd_malloc (amt); | |
101 | if (table == NULL) | |
102 | return NULL; | |
103 | ||
104 | if (!bfd_hash_table_init (&table->table, elf_strtab_hash_newfunc, | |
105 | sizeof (struct elf_strtab_hash_entry))) | |
106 | { | |
107 | free (table); | |
108 | return NULL; | |
109 | } | |
110 | ||
111 | table->sec_size = 0; | |
112 | table->size = 1; | |
113 | table->alloced = 64; | |
114 | amt = sizeof (struct elf_strtab_hasn_entry *); | |
115 | table->array = ((struct elf_strtab_hash_entry **) | |
116 | bfd_malloc (table->alloced * amt)); | |
117 | if (table->array == NULL) | |
118 | { | |
119 | free (table); | |
120 | return NULL; | |
121 | } | |
122 | ||
123 | table->array[0] = NULL; | |
124 | ||
125 | return table; | |
126 | } | |
127 | ||
128 | /* Free a strtab. */ | |
129 | ||
130 | void | |
131 | _bfd_elf_strtab_free (struct elf_strtab_hash *tab) | |
132 | { | |
133 | bfd_hash_table_free (&tab->table); | |
134 | free (tab->array); | |
135 | free (tab); | |
136 | } | |
137 | ||
138 | /* Get the index of an entity in a hash table, adding it if it is not | |
139 | already present. */ | |
140 | ||
141 | size_t | |
142 | _bfd_elf_strtab_add (struct elf_strtab_hash *tab, | |
143 | const char *str, | |
144 | bfd_boolean copy) | |
145 | { | |
146 | register struct elf_strtab_hash_entry *entry; | |
147 | ||
148 | /* We handle this specially, since we don't want to do refcounting | |
149 | on it. */ | |
150 | if (*str == '\0') | |
151 | return 0; | |
152 | ||
153 | BFD_ASSERT (tab->sec_size == 0); | |
154 | entry = (struct elf_strtab_hash_entry *) | |
155 | bfd_hash_lookup (&tab->table, str, TRUE, copy); | |
156 | ||
157 | if (entry == NULL) | |
158 | return (size_t) -1; | |
159 | ||
160 | entry->refcount++; | |
161 | if (entry->len == 0) | |
162 | { | |
163 | entry->len = strlen (str) + 1; | |
164 | /* 2G strings lose. */ | |
165 | BFD_ASSERT (entry->len > 0); | |
166 | if (tab->size == tab->alloced) | |
167 | { | |
168 | bfd_size_type amt = sizeof (struct elf_strtab_hash_entry *); | |
169 | tab->alloced *= 2; | |
170 | tab->array = (struct elf_strtab_hash_entry **) | |
171 | bfd_realloc_or_free (tab->array, tab->alloced * amt); | |
172 | if (tab->array == NULL) | |
173 | return (size_t) -1; | |
174 | } | |
175 | ||
176 | entry->u.index = tab->size++; | |
177 | tab->array[entry->u.index] = entry; | |
178 | } | |
179 | return entry->u.index; | |
180 | } | |
181 | ||
182 | void | |
183 | _bfd_elf_strtab_addref (struct elf_strtab_hash *tab, size_t idx) | |
184 | { | |
185 | if (idx == 0 || idx == (size_t) -1) | |
186 | return; | |
187 | BFD_ASSERT (tab->sec_size == 0); | |
188 | BFD_ASSERT (idx < tab->size); | |
189 | ++tab->array[idx]->refcount; | |
190 | } | |
191 | ||
192 | void | |
193 | _bfd_elf_strtab_delref (struct elf_strtab_hash *tab, size_t idx) | |
194 | { | |
195 | if (idx == 0 || idx == (size_t) -1) | |
196 | return; | |
197 | BFD_ASSERT (tab->sec_size == 0); | |
198 | BFD_ASSERT (idx < tab->size); | |
199 | BFD_ASSERT (tab->array[idx]->refcount > 0); | |
200 | --tab->array[idx]->refcount; | |
201 | } | |
202 | ||
203 | unsigned int | |
204 | _bfd_elf_strtab_refcount (struct elf_strtab_hash *tab, size_t idx) | |
205 | { | |
206 | return tab->array[idx]->refcount; | |
207 | } | |
208 | ||
209 | void | |
210 | _bfd_elf_strtab_clear_all_refs (struct elf_strtab_hash *tab) | |
211 | { | |
212 | size_t idx; | |
213 | ||
214 | for (idx = 1; idx < tab->size; idx++) | |
215 | tab->array[idx]->refcount = 0; | |
216 | } | |
217 | ||
218 | /* Save strtab refcounts prior to adding --as-needed library. */ | |
219 | ||
220 | struct strtab_save | |
221 | { | |
222 | size_t size; | |
223 | unsigned int refcount[1]; | |
224 | }; | |
225 | ||
226 | void * | |
227 | _bfd_elf_strtab_save (struct elf_strtab_hash *tab) | |
228 | { | |
229 | struct strtab_save *save; | |
230 | size_t idx, size; | |
231 | ||
232 | size = sizeof (*save) + (tab->size - 1) * sizeof (save->refcount[0]); | |
233 | save = bfd_malloc (size); | |
234 | if (save == NULL) | |
235 | return save; | |
236 | ||
237 | save->size = tab->size; | |
238 | for (idx = 1; idx < tab->size; idx++) | |
239 | save->refcount[idx] = tab->array[idx]->refcount; | |
240 | return save; | |
241 | } | |
242 | ||
243 | /* Restore strtab refcounts on finding --as-needed library not needed. */ | |
244 | ||
245 | void | |
246 | _bfd_elf_strtab_restore (struct elf_strtab_hash *tab, void *buf) | |
247 | { | |
248 | size_t idx, curr_size = tab->size, save_size; | |
249 | struct strtab_save *save = (struct strtab_save *) buf; | |
250 | ||
251 | BFD_ASSERT (tab->sec_size == 0); | |
252 | save_size = 1; | |
253 | if (save != NULL) | |
254 | save_size = save->size; | |
255 | BFD_ASSERT (save_size <= curr_size); | |
256 | tab->size = save_size; | |
257 | for (idx = 1; idx < save_size; ++idx) | |
258 | tab->array[idx]->refcount = save->refcount[idx]; | |
259 | ||
260 | for (; idx < curr_size; ++idx) | |
261 | { | |
262 | /* We don't remove entries from the hash table, just set their | |
263 | REFCOUNT to zero. Setting LEN zero will result in the size | |
264 | growing if the entry is added again. See _bfd_elf_strtab_add. */ | |
265 | tab->array[idx]->refcount = 0; | |
266 | tab->array[idx]->len = 0; | |
267 | } | |
268 | } | |
269 | ||
270 | bfd_size_type | |
271 | _bfd_elf_strtab_size (struct elf_strtab_hash *tab) | |
272 | { | |
273 | return tab->sec_size ? tab->sec_size : tab->size; | |
274 | } | |
275 | ||
276 | bfd_size_type | |
277 | _bfd_elf_strtab_len (struct elf_strtab_hash *tab) | |
278 | { | |
279 | return tab->size; | |
280 | } | |
281 | ||
282 | bfd_size_type | |
283 | _bfd_elf_strtab_offset (struct elf_strtab_hash *tab, size_t idx) | |
284 | { | |
285 | struct elf_strtab_hash_entry *entry; | |
286 | ||
287 | if (idx == 0) | |
288 | return 0; | |
289 | BFD_ASSERT (idx < tab->size); | |
290 | BFD_ASSERT (tab->sec_size); | |
291 | entry = tab->array[idx]; | |
292 | BFD_ASSERT (entry->refcount > 0); | |
293 | entry->refcount--; | |
294 | return tab->array[idx]->u.index; | |
295 | } | |
296 | ||
297 | const char * | |
298 | _bfd_elf_strtab_str (struct elf_strtab_hash *tab, size_t idx, | |
299 | bfd_size_type *offset) | |
300 | { | |
301 | if (idx == 0) | |
302 | return 0; | |
303 | BFD_ASSERT (idx < tab->size); | |
304 | BFD_ASSERT (tab->sec_size); | |
305 | if (offset) | |
306 | *offset = tab->array[idx]->u.index; | |
307 | return tab->array[idx]->root.string; | |
308 | } | |
309 | ||
310 | bfd_boolean | |
311 | _bfd_elf_strtab_emit (register bfd *abfd, struct elf_strtab_hash *tab) | |
312 | { | |
313 | bfd_size_type off = 1; | |
314 | size_t i; | |
315 | ||
316 | if (bfd_bwrite ("", 1, abfd) != 1) | |
317 | return FALSE; | |
318 | ||
319 | for (i = 1; i < tab->size; ++i) | |
320 | { | |
321 | register const char *str; | |
322 | register unsigned int len; | |
323 | ||
324 | BFD_ASSERT (tab->array[i]->refcount == 0); | |
325 | len = tab->array[i]->len; | |
326 | if ((int) len < 0) | |
327 | continue; | |
328 | ||
329 | str = tab->array[i]->root.string; | |
330 | if (bfd_bwrite (str, len, abfd) != len) | |
331 | return FALSE; | |
332 | ||
333 | off += len; | |
334 | } | |
335 | ||
336 | BFD_ASSERT (off == tab->sec_size); | |
337 | return TRUE; | |
338 | } | |
339 | ||
340 | /* Compare two elf_strtab_hash_entry structures. Called via qsort. | |
341 | Won't ever return zero as all entries differ, so there is no issue | |
342 | with qsort stability here. */ | |
343 | ||
344 | static int | |
345 | strrevcmp (const void *a, const void *b) | |
346 | { | |
347 | struct elf_strtab_hash_entry *A = *(struct elf_strtab_hash_entry **) a; | |
348 | struct elf_strtab_hash_entry *B = *(struct elf_strtab_hash_entry **) b; | |
349 | unsigned int lenA = A->len; | |
350 | unsigned int lenB = B->len; | |
351 | const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1; | |
352 | const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1; | |
353 | int l = lenA < lenB ? lenA : lenB; | |
354 | ||
355 | while (l) | |
356 | { | |
357 | if (*s != *t) | |
358 | return (int) *s - (int) *t; | |
359 | s--; | |
360 | t--; | |
361 | l--; | |
362 | } | |
363 | return lenA - lenB; | |
364 | } | |
365 | ||
366 | static inline int | |
367 | is_suffix (const struct elf_strtab_hash_entry *A, | |
368 | const struct elf_strtab_hash_entry *B) | |
369 | { | |
370 | if (A->len <= B->len) | |
371 | /* B cannot be a suffix of A unless A is equal to B, which is guaranteed | |
372 | not to be equal by the hash table. */ | |
373 | return 0; | |
374 | ||
375 | return memcmp (A->root.string + (A->len - B->len), | |
376 | B->root.string, B->len - 1) == 0; | |
377 | } | |
378 | ||
379 | /* This function assigns final string table offsets for used strings, | |
380 | merging strings matching suffixes of longer strings if possible. */ | |
381 | ||
382 | void | |
383 | _bfd_elf_strtab_finalize (struct elf_strtab_hash *tab) | |
384 | { | |
385 | struct elf_strtab_hash_entry **array, **a, *e; | |
386 | bfd_size_type amt, sec_size; | |
387 | size_t size, i; | |
388 | ||
389 | /* Sort the strings by suffix and length. */ | |
390 | amt = tab->size; | |
391 | amt *= sizeof (struct elf_strtab_hash_entry *); | |
392 | array = (struct elf_strtab_hash_entry **) bfd_malloc (amt); | |
393 | if (array == NULL) | |
394 | goto alloc_failure; | |
395 | ||
396 | for (i = 1, a = array; i < tab->size; ++i) | |
397 | { | |
398 | e = tab->array[i]; | |
399 | if (e->refcount) | |
400 | { | |
401 | *a++ = e; | |
402 | /* Adjust the length to not include the zero terminator. */ | |
403 | e->len -= 1; | |
404 | } | |
405 | else | |
406 | e->len = 0; | |
407 | } | |
408 | ||
409 | size = a - array; | |
410 | if (size != 0) | |
411 | { | |
412 | qsort (array, size, sizeof (struct elf_strtab_hash_entry *), strrevcmp); | |
413 | ||
414 | /* Loop over the sorted array and merge suffixes. Start from the | |
415 | end because we want eg. | |
416 | ||
417 | s1 -> "d" | |
418 | s2 -> "bcd" | |
419 | s3 -> "abcd" | |
420 | ||
421 | to end up as | |
422 | ||
423 | s3 -> "abcd" | |
424 | s2 _____^ | |
425 | s1 _______^ | |
426 | ||
427 | ie. we don't want s1 pointing into the old s2. */ | |
428 | e = *--a; | |
429 | e->len += 1; | |
430 | while (--a >= array) | |
431 | { | |
432 | struct elf_strtab_hash_entry *cmp = *a; | |
433 | ||
434 | cmp->len += 1; | |
435 | if (is_suffix (e, cmp)) | |
436 | { | |
437 | cmp->u.suffix = e; | |
438 | cmp->len = -cmp->len; | |
439 | } | |
440 | else | |
441 | e = cmp; | |
442 | } | |
443 | } | |
444 | ||
445 | alloc_failure: | |
446 | free (array); | |
447 | ||
448 | /* Assign positions to the strings we want to keep. */ | |
449 | sec_size = 1; | |
450 | for (i = 1; i < tab->size; ++i) | |
451 | { | |
452 | e = tab->array[i]; | |
453 | if (e->refcount && e->len > 0) | |
454 | { | |
455 | e->u.index = sec_size; | |
456 | sec_size += e->len; | |
457 | } | |
458 | } | |
459 | ||
460 | tab->sec_size = sec_size; | |
461 | ||
462 | /* Adjust the rest. */ | |
463 | for (i = 1; i < tab->size; ++i) | |
464 | { | |
465 | e = tab->array[i]; | |
466 | if (e->refcount && e->len < 0) | |
467 | e->u.index = e->u.suffix->u.index + (e->u.suffix->len + e->len); | |
468 | } | |
469 | } |