bfd/elf-strtab.c

   1 /* ELF strtab with GC and suffix merging support.
   2    Copyright 2001, 2002, 2003, 2005 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., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */
  20
  21 #include "bfd.h"
  22 #include "sysdep.h"
  23 #include "libbfd.h"
  24 #include "elf-bfd.h"
  25 #include "hashtab.h"
  26 #include "libiberty.h"
  27
  28 /* An entry in the strtab hash table.  */
  29
  30 struct elf_strtab_hash_entry
  31 {
  32   struct bfd_hash_entry root;
  33   /* Length of this entry.  This includes the zero terminator.  */
  34   int len;
  35   unsigned int refcount;
  36   union {
  37     /* Index within the merged section.  */
  38     bfd_size_type index;
  39     /* Entry this is a suffix of (if len < 0).  */
  40     struct elf_strtab_hash_entry *suffix;
  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 /* Routine to create an entry in a section merge hashtab.  */
  60
  61 static struct bfd_hash_entry *
  62 elf_strtab_hash_newfunc (struct bfd_hash_entry *entry,
  63                          struct bfd_hash_table *table,
  64                          const char *string)
  65 {
  66   /* Allocate the structure if it has not already been allocated by a
  67      subclass.  */
  68   if (entry == NULL)
  69     entry = bfd_hash_allocate (table, sizeof (struct elf_strtab_hash_entry));
  70   if (entry == NULL)
  71     return NULL;
  72
  73   /* Call the allocation method of the superclass.  */
  74   entry = bfd_hash_newfunc (entry, table, string);
  75
  76   if (entry)
  77     {
  78       /* Initialize the local fields.  */
  79       struct elf_strtab_hash_entry *ret;
  80
  81       ret = (struct elf_strtab_hash_entry *) entry;
  82       ret->u.index = -1;
  83       ret->refcount = 0;
  84       ret->len = 0;
  85     }
  86
  87   return entry;
  88 }
  89
  90 /* Create a new hash table.  */
  91
  92 struct elf_strtab_hash *
  93 _bfd_elf_strtab_init (void)
  94 {
  95   struct elf_strtab_hash *table;
  96   bfd_size_type amt = sizeof (struct elf_strtab_hash);
  97
  98   table = bfd_malloc (amt);
  99   if (table == NULL)
 100     return NULL;
 101
 102   if (! bfd_hash_table_init (&table->table, elf_strtab_hash_newfunc))
 103     {
 104       free (table);
 105       return NULL;
 106     }
 107
 108   table->sec_size = 0;
 109   table->size = 1;
 110   table->alloced = 64;
 111   amt = sizeof (struct elf_strtab_hasn_entry *);
 112   table->array = bfd_malloc (table->alloced * amt);
 113   if (table->array == NULL)
 114     {
 115       free (table);
 116       return NULL;
 117     }
 118
 119   table->array[0] = NULL;
 120
 121   return table;
 122 }
 123
 124 /* Free a strtab.  */
 125
 126 void
 127 _bfd_elf_strtab_free (struct elf_strtab_hash *tab)
 128 {
 129   bfd_hash_table_free (&tab->table);
 130   free (tab->array);
 131   free (tab);
 132 }
 133
 134 /* Get the index of an entity in a hash table, adding it if it is not
 135    already present.  */
 136
 137 bfd_size_type
 138 _bfd_elf_strtab_add (struct elf_strtab_hash *tab,
 139                      const char *str,
 140                      bfd_boolean copy)
 141 {
 142   register struct elf_strtab_hash_entry *entry;
 143
 144   /* We handle this specially, since we don't want to do refcounting
 145      on it.  */
 146   if (*str == '\0')
 147     return 0;
 148
 149   BFD_ASSERT (tab->sec_size == 0);
 150   entry = (struct elf_strtab_hash_entry *)
 151           bfd_hash_lookup (&tab->table, str, TRUE, copy);
 152
 153   if (entry == NULL)
 154     return (bfd_size_type) -1;
 155
 156   entry->refcount++;
 157   if (entry->len == 0)
 158     {
 159       entry->len = strlen (str) + 1;
 160       /* 2G strings lose.  */
 161       BFD_ASSERT (entry->len > 0);
 162       if (tab->size == tab->alloced)
 163         {
 164           bfd_size_type amt = sizeof (struct elf_strtab_hash_entry *);
 165           tab->alloced *= 2;
 166           tab->array = bfd_realloc (tab->array, tab->alloced * amt);
 167           if (tab->array == NULL)
 168             return (bfd_size_type) -1;
 169         }
 170
 171       entry->u.index = tab->size++;
 172       tab->array[entry->u.index] = entry;
 173     }
 174   return entry->u.index;
 175 }
 176
 177 void
 178 _bfd_elf_strtab_addref (struct elf_strtab_hash *tab, bfd_size_type idx)
 179 {
 180   if (idx == 0 || idx == (bfd_size_type) -1)
 181     return;
 182   BFD_ASSERT (tab->sec_size == 0);
 183   BFD_ASSERT (idx < tab->size);
 184   ++tab->array[idx]->refcount;
 185 }
 186
 187 void
 188 _bfd_elf_strtab_delref (struct elf_strtab_hash *tab, bfd_size_type idx)
 189 {
 190   if (idx == 0 || idx == (bfd_size_type) -1)
 191     return;
 192   BFD_ASSERT (tab->sec_size == 0);
 193   BFD_ASSERT (idx < tab->size);
 194   BFD_ASSERT (tab->array[idx]->refcount > 0);
 195   --tab->array[idx]->refcount;
 196 }
 197
 198 void
 199 _bfd_elf_strtab_clear_all_refs (struct elf_strtab_hash *tab)
 200 {
 201   bfd_size_type idx;
 202
 203   for (idx = 1; idx < tab->size; ++idx)
 204     tab->array[idx]->refcount = 0;
 205 }
 206
 207 bfd_size_type
 208 _bfd_elf_strtab_size (struct elf_strtab_hash *tab)
 209 {
 210   return tab->sec_size ? tab->sec_size : tab->size;
 211 }
 212
 213 bfd_size_type
 214 _bfd_elf_strtab_offset (struct elf_strtab_hash *tab, bfd_size_type idx)
 215 {
 216   struct elf_strtab_hash_entry *entry;
 217
 218   if (idx == 0)
 219     return 0;
 220   BFD_ASSERT (idx < tab->size);
 221   BFD_ASSERT (tab->sec_size);
 222   entry = tab->array[idx];
 223   BFD_ASSERT (entry->refcount > 0);
 224   entry->refcount--;
 225   return tab->array[idx]->u.index;
 226 }
 227
 228 bfd_boolean
 229 _bfd_elf_strtab_emit (register bfd *abfd, struct elf_strtab_hash *tab)
 230 {
 231   bfd_size_type off = 1, i;
 232
 233   if (bfd_bwrite ("", 1, abfd) != 1)
 234     return FALSE;
 235
 236   for (i = 1; i < tab->size; ++i)
 237     {
 238       register const char *str;
 239       register unsigned int len;
 240
 241       BFD_ASSERT (tab->array[i]->refcount == 0);
 242       len = tab->array[i]->len;
 243       if ((int) len < 0)
 244         continue;
 245
 246       str = tab->array[i]->root.string;
 247       if (bfd_bwrite (str, len, abfd) != len)
 248         return FALSE;
 249
 250       off += len;
 251     }
 252
 253   BFD_ASSERT (off == tab->sec_size);
 254   return TRUE;
 255 }
 256
 257 /* Compare two elf_strtab_hash_entry structures.  Called via qsort.  */
 258
 259 static int
 260 strrevcmp (const void *a, const void *b)
 261 {
 262   struct elf_strtab_hash_entry *A = *(struct elf_strtab_hash_entry **) a;
 263   struct elf_strtab_hash_entry *B = *(struct elf_strtab_hash_entry **) b;
 264   unsigned int lenA = A->len;
 265   unsigned int lenB = B->len;
 266   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 267   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 268   int l = lenA < lenB ? lenA : lenB;
 269
 270   while (l)
 271     {
 272       if (*s != *t)
 273         return (int) *s - (int) *t;
 274       s--;
 275       t--;
 276       l--;
 277     }
 278   return lenA - lenB;
 279 }
 280
 281 static inline int
 282 is_suffix (const struct elf_strtab_hash_entry *A,
 283            const struct elf_strtab_hash_entry *B)
 284 {
 285   if (A->len <= B->len)
 286     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 287        not to be equal by the hash table.  */
 288     return 0;
 289
 290   return memcmp (A->root.string + (A->len - B->len),
 291                  B->root.string, B->len - 1) == 0;
 292 }
 293
 294 /* This function assigns final string table offsets for used strings,
 295    merging strings matching suffixes of longer strings if possible.  */
 296
 297 void
 298 _bfd_elf_strtab_finalize (struct elf_strtab_hash *tab)
 299 {
 300   struct elf_strtab_hash_entry **array, **a, *e;
 301   bfd_size_type size, amt;
 302
 303   /* GCC 2.91.66 (egcs-1.1.2) on i386 miscompiles this function when i is
 304      a 64-bit bfd_size_type: a 64-bit target or --enable-64-bit-bfd.
 305      Besides, indexing with a long long wouldn't give anything but extra
 306      cycles.  */
 307   size_t i;
 308
 309   /* Sort the strings by suffix and length.  */
 310   amt = tab->size * sizeof (struct elf_strtab_hash_entry *);
 311   array = bfd_malloc (amt);
 312   if (array == NULL)
 313     goto alloc_failure;
 314
 315   for (i = 1, a = array; i < tab->size; ++i)
 316     {
 317       e = tab->array[i];
 318       if (e->refcount)
 319         {
 320           *a++ = e;
 321           /* Adjust the length to not include the zero terminator.  */
 322           e->len -= 1;
 323         }
 324       else
 325         e->len = 0;
 326     }
 327
 328   size = a - array;
 329   if (size != 0)
 330     {
 331       qsort (array, size, sizeof (struct elf_strtab_hash_entry *), strrevcmp);
 332
 333       /* Loop over the sorted array and merge suffixes.  Start from the
 334          end because we want eg.
 335
 336          s1 -> "d"
 337          s2 -> "bcd"
 338          s3 -> "abcd"
 339
 340          to end up as
 341
 342          s3 -> "abcd"
 343          s2 _____^
 344          s1 _______^
 345
 346          ie. we don't want s1 pointing into the old s2.  */
 347       e = *--a;
 348       e->len += 1;
 349       while (--a >= array)
 350         {
 351           struct elf_strtab_hash_entry *cmp = *a;
 352
 353           cmp->len += 1;
 354           if (is_suffix (e, cmp))
 355             {
 356               cmp->u.suffix = e;
 357               cmp->len = -cmp->len;
 358             }
 359           else
 360             e = cmp;
 361         }
 362     }
 363
 364 alloc_failure:
 365   if (array)
 366     free (array);
 367
 368   /* Assign positions to the strings we want to keep.  */
 369   size = 1;
 370   for (i = 1; i < tab->size; ++i)
 371     {
 372       e = tab->array[i];
 373       if (e->refcount && e->len > 0)
 374         {
 375           e->u.index = size;
 376           size += e->len;
 377         }
 378     }
 379
 380   tab->sec_size = size;
 381
 382   /* Adjust the rest.  */
 383   for (i = 1; i < tab->size; ++i)
 384     {
 385       e = tab->array[i];
 386       if (e->refcount && e->len < 0)
 387         e->u.index = e->u.suffix->u.index + (e->u.suffix->len + e->len);
 388     }
 389 }