1 /* ELF strtab with GC and suffix merging support. 2 Copyright 2001, 2002, 2003, 2005, 2006, 2007, 2008 3 Free Software Foundation, Inc. 4 Written by Jakub Jelinek <jakub@redhat.com>. 5 6 This file is part of BFD, the Binary File Descriptor library. 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 "sysdep.h" 24 #include "bfd.h" 25 #include "libbfd.h" 26 #include "elf-bfd.h" 27 #include "hashtab.h" 28 #include "libiberty.h" 29 30 /* An entry in the strtab hash table. */ 31 32 struct elf_strtab_hash_entry 33 { 34 struct bfd_hash_entry root; 35 /* Length of this entry. This includes the zero terminator. */ 36 int len; 37 unsigned int refcount; 38 union { 39 /* Index within the merged section. */ 40 bfd_size_type index; 41 /* Entry this is a suffix of (if len < 0). */ 42 struct elf_strtab_hash_entry *suffix; 43 } u; 44 }; 45 46 /* The strtab hash table. */ 47 48 struct elf_strtab_hash 49 { 50 struct bfd_hash_table table; 51 /* Next available index. */ 52 bfd_size_type size; 53 /* Number of array entries alloced. */ 54 bfd_size_type alloced; 55 /* Final strtab size. */ 56 bfd_size_type sec_size; 57 /* Array of pointers to strtab entries. */ 58 struct elf_strtab_hash_entry **array; 59 }; 60 61 /* Routine to create an entry in a section merge hashtab. */ 62 63 static struct bfd_hash_entry * 64 elf_strtab_hash_newfunc (struct bfd_hash_entry *entry, 65 struct bfd_hash_table *table, 66 const char *string) 67 { 68 /* Allocate the structure if it has not already been allocated by a 69 subclass. */ 70 if (entry == NULL) 71 entry = (struct bfd_hash_entry *) 72 bfd_hash_allocate (table, sizeof (struct elf_strtab_hash_entry)); 73 if (entry == NULL) 74 return NULL; 75 76 /* Call the allocation method of the superclass. */ 77 entry = bfd_hash_newfunc (entry, table, string); 78 79 if (entry) 80 { 81 /* Initialize the local fields. */ 82 struct elf_strtab_hash_entry *ret; 83 84 ret = (struct elf_strtab_hash_entry *) entry; 85 ret->u.index = -1; 86 ret->refcount = 0; 87 ret->len = 0; 88 } 89 90 return entry; 91 } 92 93 /* Create a new hash table. */ 94 95 struct elf_strtab_hash * 96 _bfd_elf_strtab_init (void) 97 { 98 struct elf_strtab_hash *table; 99 bfd_size_type amt = sizeof (struct elf_strtab_hash); 100 101 table = (struct elf_strtab_hash *) bfd_malloc (amt); 102 if (table == NULL) 103 return NULL; 104 105 if (!bfd_hash_table_init (&table->table, elf_strtab_hash_newfunc, 106 sizeof (struct elf_strtab_hash_entry))) 107 { 108 free (table); 109 return NULL; 110 } 111 112 table->sec_size = 0; 113 table->size = 1; 114 table->alloced = 64; 115 amt = sizeof (struct elf_strtab_hasn_entry *); 116 table->array = (struct elf_strtab_hash_entry **) 117 bfd_malloc (table->alloced * amt); 118 if (table->array == NULL) 119 { 120 free (table); 121 return NULL; 122 } 123 124 table->array[0] = NULL; 125 126 return table; 127 } 128 129 /* Free a strtab. */ 130 131 void 132 _bfd_elf_strtab_free (struct elf_strtab_hash *tab) 133 { 134 bfd_hash_table_free (&tab->table); 135 free (tab->array); 136 free (tab); 137 } 138 139 /* Get the index of an entity in a hash table, adding it if it is not 140 already present. */ 141 142 bfd_size_type 143 _bfd_elf_strtab_add (struct elf_strtab_hash *tab, 144 const char *str, 145 bfd_boolean copy) 146 { 147 register struct elf_strtab_hash_entry *entry; 148 149 /* We handle this specially, since we don't want to do refcounting 150 on it. */ 151 if (*str == '\0') 152 return 0; 153 154 BFD_ASSERT (tab->sec_size == 0); 155 entry = (struct elf_strtab_hash_entry *) 156 bfd_hash_lookup (&tab->table, str, TRUE, copy); 157 158 if (entry == NULL) 159 return (bfd_size_type) -1; 160 161 entry->refcount++; 162 if (entry->len == 0) 163 { 164 entry->len = strlen (str) + 1; 165 /* 2G strings lose. */ 166 BFD_ASSERT (entry->len > 0); 167 if (tab->size == tab->alloced) 168 { 169 bfd_size_type amt = sizeof (struct elf_strtab_hash_entry *); 170 tab->alloced *= 2; 171 tab->array = (struct elf_strtab_hash_entry **) 172 bfd_realloc_or_free (tab->array, tab->alloced * amt); 173 if (tab->array == NULL) 174 return (bfd_size_type) -1; 175 } 176 177 entry->u.index = tab->size++; 178 tab->array[entry->u.index] = entry; 179 } 180 return entry->u.index; 181 } 182 183 void 184 _bfd_elf_strtab_addref (struct elf_strtab_hash *tab, bfd_size_type idx) 185 { 186 if (idx == 0 || idx == (bfd_size_type) -1) 187 return; 188 BFD_ASSERT (tab->sec_size == 0); 189 BFD_ASSERT (idx < tab->size); 190 ++tab->array[idx]->refcount; 191 } 192 193 void 194 _bfd_elf_strtab_delref (struct elf_strtab_hash *tab, bfd_size_type idx) 195 { 196 if (idx == 0 || idx == (bfd_size_type) -1) 197 return; 198 BFD_ASSERT (tab->sec_size == 0); 199 BFD_ASSERT (idx < tab->size); 200 BFD_ASSERT (tab->array[idx]->refcount > 0); 201 --tab->array[idx]->refcount; 202 } 203 204 void 205 _bfd_elf_strtab_clear_all_refs (struct elf_strtab_hash *tab) 206 { 207 bfd_size_type idx; 208 209 for (idx = 1; idx < tab->size; ++idx) 210 tab->array[idx]->refcount = 0; 211 } 212 213 bfd_size_type 214 _bfd_elf_strtab_size (struct elf_strtab_hash *tab) 215 { 216 return tab->sec_size ? tab->sec_size : tab->size; 217 } 218 219 bfd_size_type 220 _bfd_elf_strtab_offset (struct elf_strtab_hash *tab, bfd_size_type idx) 221 { 222 struct elf_strtab_hash_entry *entry; 223 224 if (idx == 0) 225 return 0; 226 BFD_ASSERT (idx < tab->size); 227 BFD_ASSERT (tab->sec_size); 228 entry = tab->array[idx]; 229 BFD_ASSERT (entry->refcount > 0); 230 entry->refcount--; 231 return tab->array[idx]->u.index; 232 } 233 234 bfd_boolean 235 _bfd_elf_strtab_emit (register bfd *abfd, struct elf_strtab_hash *tab) 236 { 237 bfd_size_type off = 1, i; 238 239 if (bfd_bwrite ("", 1, abfd) != 1) 240 return FALSE; 241 242 for (i = 1; i < tab->size; ++i) 243 { 244 register const char *str; 245 register unsigned int len; 246 247 BFD_ASSERT (tab->array[i]->refcount == 0); 248 len = tab->array[i]->len; 249 if ((int) len < 0) 250 continue; 251 252 str = tab->array[i]->root.string; 253 if (bfd_bwrite (str, len, abfd) != len) 254 return FALSE; 255 256 off += len; 257 } 258 259 BFD_ASSERT (off == tab->sec_size); 260 return TRUE; 261 } 262 263 /* Compare two elf_strtab_hash_entry structures. Called via qsort. */ 264 265 static int 266 strrevcmp (const void *a, const void *b) 267 { 268 struct elf_strtab_hash_entry *A = *(struct elf_strtab_hash_entry **) a; 269 struct elf_strtab_hash_entry *B = *(struct elf_strtab_hash_entry **) b; 270 unsigned int lenA = A->len; 271 unsigned int lenB = B->len; 272 const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1; 273 const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1; 274 int l = lenA < lenB ? lenA : lenB; 275 276 while (l) 277 { 278 if (*s != *t) 279 return (int) *s - (int) *t; 280 s--; 281 t--; 282 l--; 283 } 284 return lenA - lenB; 285 } 286 287 static inline int 288 is_suffix (const struct elf_strtab_hash_entry *A, 289 const struct elf_strtab_hash_entry *B) 290 { 291 if (A->len <= B->len) 292 /* B cannot be a suffix of A unless A is equal to B, which is guaranteed 293 not to be equal by the hash table. */ 294 return 0; 295 296 return memcmp (A->root.string + (A->len - B->len), 297 B->root.string, B->len - 1) == 0; 298 } 299 300 /* This function assigns final string table offsets for used strings, 301 merging strings matching suffixes of longer strings if possible. */ 302 303 void 304 _bfd_elf_strtab_finalize (struct elf_strtab_hash *tab) 305 { 306 struct elf_strtab_hash_entry **array, **a, *e; 307 bfd_size_type size, amt; 308 309 /* GCC 2.91.66 (egcs-1.1.2) on i386 miscompiles this function when i is 310 a 64-bit bfd_size_type: a 64-bit target or --enable-64-bit-bfd. 311 Besides, indexing with a long long wouldn't give anything but extra 312 cycles. */ 313 size_t i; 314 315 /* Sort the strings by suffix and length. */ 316 amt = tab->size * sizeof (struct elf_strtab_hash_entry *); 317 array = (struct elf_strtab_hash_entry **) bfd_malloc (amt); 318 if (array == NULL) 319 goto alloc_failure; 320 321 for (i = 1, a = array; i < tab->size; ++i) 322 { 323 e = tab->array[i]; 324 if (e->refcount) 325 { 326 *a++ = e; 327 /* Adjust the length to not include the zero terminator. */ 328 e->len -= 1; 329 } 330 else 331 e->len = 0; 332 } 333 334 size = a - array; 335 if (size != 0) 336 { 337 qsort (array, size, sizeof (struct elf_strtab_hash_entry *), strrevcmp); 338 339 /* Loop over the sorted array and merge suffixes. Start from the 340 end because we want eg. 341 342 s1 -> "d" 343 s2 -> "bcd" 344 s3 -> "abcd" 345 346 to end up as 347 348 s3 -> "abcd" 349 s2 _____^ 350 s1 _______^ 351 352 ie. we don't want s1 pointing into the old s2. */ 353 e = *--a; 354 e->len += 1; 355 while (--a >= array) 356 { 357 struct elf_strtab_hash_entry *cmp = *a; 358 359 cmp->len += 1; 360 if (is_suffix (e, cmp)) 361 { 362 cmp->u.suffix = e; 363 cmp->len = -cmp->len; 364 } 365 else 366 e = cmp; 367 } 368 } 369 370 alloc_failure: 371 if (array) 372 free (array); 373 374 /* Assign positions to the strings we want to keep. */ 375 size = 1; 376 for (i = 1; i < tab->size; ++i) 377 { 378 e = tab->array[i]; 379 if (e->refcount && e->len > 0) 380 { 381 e->u.index = size; 382 size += e->len; 383 } 384 } 385 386 tab->sec_size = size; 387 388 /* Adjust the rest. */ 389 for (i = 1; i < tab->size; ++i) 390 { 391 e = tab->array[i]; 392 if (e->refcount && e->len < 0) 393 e->u.index = e->u.suffix->u.index + (e->u.suffix->len + e->len); 394 } 395 } 396