bfd/elf-strtab.c

   1 /* ELF strtab with GC and suffix merging support.
   2    Copyright 2001 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 2 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 #include "bfd.h"
  22 #include "sysdep.h"
  23 #include "libbfd.h"
  24 #include "elf-bfd.h"
  25 #include "hashtab.h"
  26
  27 /* An entry in the strtab hash table.  */
  28
  29 struct elf_strtab_hash_entry
  30 {
  31   struct bfd_hash_entry root;
  32   /* Length of this entry.  */
  33   unsigned int len;
  34   unsigned int refcount;
  35   union {
  36     /* Index within the merged section.  */
  37     bfd_size_type index;
  38     /* Entry this is a suffix of (if len is 0).  */
  39     struct elf_strtab_hash_entry *suffix;
  40     struct elf_strtab_hash_entry *next;
  41   } u;
  42 };
  43
  44 /* The strtab hash table.  */
  45
  46 struct elf_strtab_hash
  47 {
  48   struct bfd_hash_table table;
  49   /* Next available index.  */
  50   bfd_size_type size;
  51   /* Number of array entries alloced.  */
  52   bfd_size_type alloced;
  53   /* Final strtab size.  */
  54   bfd_size_type sec_size;
  55   /* Array of pointers to strtab entries.  */
  56   struct elf_strtab_hash_entry **array;
  57 };
  58
  59 static struct bfd_hash_entry *elf_strtab_hash_newfunc
  60   PARAMS ((struct bfd_hash_entry *, struct bfd_hash_table *, const char *));
  61 static int cmplengthentry PARAMS ((const PTR, const PTR));
  62 static int last4_eq PARAMS ((const PTR, const PTR));
  63
  64 /* Routine to create an entry in a section merge hashtab.  */
  65
  66 static struct bfd_hash_entry *
  67 elf_strtab_hash_newfunc (entry, table, string)
  68      struct bfd_hash_entry *entry;
  69      struct bfd_hash_table *table;
  70      const char *string;
  71 {
  72   struct elf_strtab_hash_entry *ret = (struct elf_strtab_hash_entry *) entry;
  73
  74   /* Allocate the structure if it has not already been allocated by a
  75      subclass.  */
  76   if (ret == (struct elf_strtab_hash_entry *) NULL)
  77     ret = ((struct elf_strtab_hash_entry *)
  78            bfd_hash_allocate (table, sizeof (struct elf_strtab_hash_entry)));
  79   if (ret == (struct elf_strtab_hash_entry *) NULL)
  80     return NULL;
  81
  82   /* Call the allocation method of the superclass.  */
  83   ret = ((struct elf_strtab_hash_entry *)
  84          bfd_hash_newfunc ((struct bfd_hash_entry *) ret, table, string));
  85
  86   if (ret)
  87     {
  88       /* Initialize the local fields.  */
  89       ret->u.index = -1;
  90       ret->refcount = 0;
  91       ret->len = 0;
  92     }
  93
  94   return (struct bfd_hash_entry *)ret;
  95 }
  96
  97 /* Create a new hash table.  */
  98
  99 struct elf_strtab_hash *
 100 _bfd_elf_strtab_init ()
 101 {
 102   struct elf_strtab_hash *table;
 103   bfd_size_type amt = sizeof (struct elf_strtab_hash);
 104
 105   table = (struct elf_strtab_hash *) bfd_malloc (amt);
 106   if (table == NULL)
 107     return NULL;
 108
 109   if (! bfd_hash_table_init (&table->table, elf_strtab_hash_newfunc))
 110     {
 111       free (table);
 112       return NULL;
 113     }
 114
 115   table->sec_size = 0;
 116   table->size = 1;
 117   table->alloced = 64;
 118   amt = sizeof (struct elf_strtab_hasn_entry *);
 119   table->array = (struct elf_strtab_hash_entry **)
 120                  bfd_malloc (table->alloced * amt);
 121   if (table->array == NULL)
 122     {
 123       free (table);
 124       return NULL;
 125     }
 126
 127   table->array[0] = NULL;
 128
 129   return table;
 130 }
 131
 132 /* Free a strtab.  */
 133
 134 void
 135 _bfd_elf_strtab_free (tab)
 136      struct elf_strtab_hash *tab;
 137 {
 138   bfd_hash_table_free (&tab->table);
 139   free (tab->array);
 140   free (tab);
 141 }
 142
 143 /* Get the index of an entity in a hash table, adding it if it is not
 144    already present.  */
 145
 146 bfd_size_type
 147 _bfd_elf_strtab_add (tab, str, copy)
 148      struct elf_strtab_hash *tab;
 149      const char *str;
 150      boolean copy;
 151 {
 152   register struct elf_strtab_hash_entry *entry;
 153
 154   /* We handle this specially, since we don't want to do refcounting
 155      on it.  */
 156   if (*str == '\0')
 157     return 0;
 158
 159   BFD_ASSERT (tab->sec_size == 0);
 160   entry = (struct elf_strtab_hash_entry *)
 161           bfd_hash_lookup (&tab->table, str, true, copy);
 162
 163   if (entry == NULL)
 164     return (bfd_size_type) -1;
 165
 166   entry->refcount++;
 167   if (entry->len == 0)
 168     {
 169       entry->len = strlen (str) + 1;
 170       if (tab->size == tab->alloced)
 171         {
 172           bfd_size_type amt = sizeof (struct elf_strtab_hash_entry *);
 173           tab->alloced *= 2;
 174           tab->array = (struct elf_strtab_hash_entry **)
 175                        bfd_realloc (tab->array, tab->alloced * amt);
 176           if (tab->array == NULL)
 177             return (bfd_size_type) -1;
 178         }
 179
 180       entry->u.index = tab->size++;
 181       tab->array[entry->u.index] = entry;
 182     }
 183   return entry->u.index;
 184 }
 185
 186 void
 187 _bfd_elf_strtab_addref (tab, idx)
 188      struct elf_strtab_hash *tab;
 189      bfd_size_type idx;
 190 {
 191   if (idx == 0 || idx == (bfd_size_type) -1)
 192     return;
 193   BFD_ASSERT (tab->sec_size == 0);
 194   BFD_ASSERT (idx < tab->size);
 195   ++tab->array[idx]->refcount;
 196 }
 197
 198 void
 199 _bfd_elf_strtab_delref (tab, idx)
 200      struct elf_strtab_hash *tab;
 201      bfd_size_type idx;
 202 {
 203   if (idx == 0 || idx == (bfd_size_type) -1)
 204     return;
 205   BFD_ASSERT (tab->sec_size == 0);
 206   BFD_ASSERT (idx < tab->size);
 207   BFD_ASSERT (tab->array[idx]->refcount > 0);
 208   --tab->array[idx]->refcount;
 209 }
 210
 211 void
 212 _bfd_elf_strtab_clear_all_refs (tab)
 213      struct elf_strtab_hash *tab;
 214 {
 215   bfd_size_type idx;
 216
 217   for (idx = 1; idx < tab->size; ++idx)
 218     tab->array[idx]->refcount = 0;
 219 }
 220
 221 bfd_size_type
 222 _bfd_elf_strtab_size (tab)
 223      struct elf_strtab_hash *tab;
 224 {
 225   return tab->sec_size ? tab->sec_size : tab->size;
 226 }
 227
 228 bfd_size_type
 229 _bfd_elf_strtab_offset (tab, idx)
 230      struct elf_strtab_hash *tab;
 231      bfd_size_type idx;
 232 {
 233   struct elf_strtab_hash_entry *entry;
 234
 235   if (idx == 0)
 236     return 0;
 237   BFD_ASSERT (idx < tab->size);
 238   BFD_ASSERT (tab->sec_size);
 239   entry = tab->array[idx];
 240   BFD_ASSERT (entry->refcount > 0);
 241   entry->refcount--;
 242   return tab->array[idx]->u.index;
 243 }
 244
 245 boolean
 246 _bfd_elf_strtab_emit (abfd, tab)
 247      register bfd *abfd;
 248      struct elf_strtab_hash *tab;
 249 {
 250   bfd_size_type off = 1, i;
 251
 252   if (bfd_bwrite ("", 1, abfd) != 1)
 253     return false;
 254
 255   for (i = 1; i < tab->size; ++i)
 256     {
 257       register const char *str;
 258       register size_t len;
 259
 260       str = tab->array[i]->root.string;
 261       len = tab->array[i]->len;
 262       BFD_ASSERT (tab->array[i]->refcount == 0);
 263       if (len == 0)
 264         continue;
 265
 266       if (bfd_bwrite ((PTR) str, (bfd_size_type) len, abfd) != len)
 267         return false;
 268
 269       off += len;
 270     }
 271
 272   BFD_ASSERT (off == tab->sec_size);
 273   return true;
 274 }
 275
 276 /* Compare two elf_strtab_hash_entry structures.  This is called via qsort.  */
 277
 278 static int
 279 cmplengthentry (a, b)
 280      const PTR a;
 281      const PTR b;
 282 {
 283   struct elf_strtab_hash_entry * A = *(struct elf_strtab_hash_entry **) a;
 284   struct elf_strtab_hash_entry * B = *(struct elf_strtab_hash_entry **) b;
 285
 286   if (A->len < B->len)
 287     return 1;
 288   else if (A->len > B->len)
 289     return -1;
 290
 291   return memcmp (A->root.string, B->root.string, A->len);
 292 }
 293
 294 static int
 295 last4_eq (a, b)
 296      const PTR a;
 297      const PTR b;
 298 {
 299   struct elf_strtab_hash_entry * A = (struct elf_strtab_hash_entry *) a;
 300   struct elf_strtab_hash_entry * B = (struct elf_strtab_hash_entry *) b;
 301
 302   if (memcmp (A->root.string + A->len - 5, B->root.string + B->len - 5, 4)
 303       != 0)
 304     /* This was a hashtable collision.  */
 305     return 0;
 306
 307   if (A->len <= B->len)
 308     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 309        not to be equal by the hash table.  */
 310     return 0;
 311
 312   return memcmp (A->root.string + (A->len - B->len),
 313                  B->root.string, B->len - 5) == 0;
 314 }
 315
 316 /* This function assigns final string table offsets for used strings,
 317    merging strings matching suffixes of longer strings if possible.  */
 318
 319 void
 320 _bfd_elf_strtab_finalize (tab)
 321      struct elf_strtab_hash *tab;
 322 {
 323   struct elf_strtab_hash_entry **array, **a, **end, *e;
 324   htab_t last4tab = NULL;
 325   bfd_size_type size, amt;
 326   struct elf_strtab_hash_entry *last[256], **last_ptr[256];
 327
 328   /* GCC 2.91.66 (egcs-1.1.2) on i386 miscompiles this function when i is
 329      a 64-bit bfd_size_type: a 64-bit target or --enable-64-bit-bfd.
 330      Besides, indexing with a long long wouldn't give anything but extra
 331      cycles.  */
 332   size_t i;
 333
 334   /* Now sort the strings by length, longest first.  */
 335   array = NULL;
 336   amt = tab->size * sizeof (struct elf_strtab_hash_entry *);
 337   array = (struct elf_strtab_hash_entry **) bfd_malloc (amt);
 338   if (array == NULL)
 339     goto alloc_failure;
 340
 341   memset (last, 0, sizeof (last));
 342   for (i = 0; i < 256; ++i)
 343     last_ptr[i] = &last[i];
 344   for (i = 1, a = array; i < tab->size; ++i)
 345     if (tab->array[i]->refcount)
 346       *a++ = tab->array[i];
 347     else
 348       tab->array[i]->len = 0;
 349
 350   size = a - array;
 351
 352   qsort (array, size, sizeof (struct elf_strtab_hash_entry *), cmplengthentry);
 353
 354   last4tab = htab_create (size * 4, NULL, last4_eq, NULL);
 355   if (last4tab == NULL)
 356     goto alloc_failure;
 357
 358   /* Now insert the strings into hash tables (strings with last 4 characters
 359      and strings with last character equal), look for longer strings which
 360      we're suffix of.  */
 361   for (a = array, end = array + size; a < end; a++)
 362     {
 363       register hashval_t hash;
 364       unsigned int c;
 365       unsigned int j;
 366       const unsigned char *s;
 367       PTR *p;
 368
 369       e = *a;
 370       if (e->len > 4)
 371         {
 372           s = e->root.string + e->len - 1;
 373           hash = 0;
 374           for (j = 0; j < 4; j++)
 375             {
 376               c = *--s;
 377               hash += c + (c << 17);
 378               hash ^= hash >> 2;
 379             }
 380           p = htab_find_slot_with_hash (last4tab, e, hash, INSERT);
 381           if (p == NULL)
 382             goto alloc_failure;
 383           if (*p)
 384             {
 385               struct elf_strtab_hash_entry *ent;
 386
 387               ent = (struct elf_strtab_hash_entry *) *p;
 388               e->u.suffix = ent;
 389               e->len = 0;
 390               continue;
 391             }
 392           else
 393             *p = (PTR) e;
 394         }
 395       else
 396         {
 397           struct elf_strtab_hash_entry *tem;
 398
 399           c = e->root.string[e->len - 2] & 0xff;
 400
 401           for (tem = last[c]; tem; tem = tem->u.next)
 402             if (tem->len > e->len
 403                 && memcmp (tem->root.string + (tem->len - e->len),
 404                            e->root.string, e->len - 1) == 0)
 405               break;
 406           if (tem)
 407             {
 408               e->u.suffix = tem;
 409               e->len = 0;
 410               continue;
 411             }
 412         }
 413
 414       c = e->root.string[e->len - 2] & 0xff;
 415       /* Put longest strings first.  */
 416       *last_ptr[c] = e;
 417       last_ptr[c] = &e->u.next;
 418       e->u.next = NULL;
 419     }
 420
 421 alloc_failure:
 422   if (array)
 423     free (array);
 424   if (last4tab)
 425     htab_delete (last4tab);
 426
 427   /* Now assign positions to the strings we want to keep.  */
 428   size = 1;
 429   for (i = 1; i < tab->size; ++i)
 430     {
 431       e = tab->array[i];
 432       if (e->refcount && e->len)
 433         {
 434           e->u.index = size;
 435           size += e->len;
 436         }
 437     }
 438
 439   tab->sec_size = size;
 440
 441   /* And now adjust the rest.  */
 442   for (i = 1; i < tab->size; ++i)
 443     {
 444       e = tab->array[i];
 445       if (e->refcount && ! e->len)
 446         e->u.index = e->u.suffix->u.index
 447                      + (e->u.suffix->len - strlen (e->root.string) - 1);
 448     }
 449 }