bfd/elf-strtab.c

   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_refs (struct elf_strtab_hash *tab, bfd_size_type idx)
 206 {
 207   while (idx < tab->size)
 208     tab->array[idx++]->refcount = 0;
 209 }
 210
 211 bfd_size_type
 212 _bfd_elf_strtab_size (struct elf_strtab_hash *tab)
 213 {
 214   return tab->sec_size ? tab->sec_size : tab->size;
 215 }
 216
 217 bfd_size_type
 218 _bfd_elf_strtab_offset (struct elf_strtab_hash *tab, bfd_size_type idx)
 219 {
 220   struct elf_strtab_hash_entry *entry;
 221
 222   if (idx == 0)
 223     return 0;
 224   BFD_ASSERT (idx < tab->size);
 225   BFD_ASSERT (tab->sec_size);
 226   entry = tab->array[idx];
 227   BFD_ASSERT (entry->refcount > 0);
 228   entry->refcount--;
 229   return tab->array[idx]->u.index;
 230 }
 231
 232 bfd_boolean
 233 _bfd_elf_strtab_emit (register bfd *abfd, struct elf_strtab_hash *tab)
 234 {
 235   bfd_size_type off = 1, i;
 236
 237   if (bfd_bwrite ("", 1, abfd) != 1)
 238     return FALSE;
 239
 240   for (i = 1; i < tab->size; ++i)
 241     {
 242       register const char *str;
 243       register unsigned int len;
 244
 245       BFD_ASSERT (tab->array[i]->refcount == 0);
 246       len = tab->array[i]->len;
 247       if ((int) len < 0)
 248         continue;
 249
 250       str = tab->array[i]->root.string;
 251       if (bfd_bwrite (str, len, abfd) != len)
 252         return FALSE;
 253
 254       off += len;
 255     }
 256
 257   BFD_ASSERT (off == tab->sec_size);
 258   return TRUE;
 259 }
 260
 261 /* Compare two elf_strtab_hash_entry structures.  Called via qsort.  */
 262
 263 static int
 264 strrevcmp (const void *a, const void *b)
 265 {
 266   struct elf_strtab_hash_entry *A = *(struct elf_strtab_hash_entry **) a;
 267   struct elf_strtab_hash_entry *B = *(struct elf_strtab_hash_entry **) b;
 268   unsigned int lenA = A->len;
 269   unsigned int lenB = B->len;
 270   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 271   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 272   int l = lenA < lenB ? lenA : lenB;
 273
 274   while (l)
 275     {
 276       if (*s != *t)
 277         return (int) *s - (int) *t;
 278       s--;
 279       t--;
 280       l--;
 281     }
 282   return lenA - lenB;
 283 }
 284
 285 static inline int
 286 is_suffix (const struct elf_strtab_hash_entry *A,
 287            const struct elf_strtab_hash_entry *B)
 288 {
 289   if (A->len <= B->len)
 290     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 291        not to be equal by the hash table.  */
 292     return 0;
 293
 294   return memcmp (A->root.string + (A->len - B->len),
 295                  B->root.string, B->len - 1) == 0;
 296 }
 297
 298 /* This function assigns final string table offsets for used strings,
 299    merging strings matching suffixes of longer strings if possible.  */
 300
 301 void
 302 _bfd_elf_strtab_finalize (struct elf_strtab_hash *tab)
 303 {
 304   struct elf_strtab_hash_entry **array, **a, *e;
 305   bfd_size_type size, amt;
 306
 307   /* GCC 2.91.66 (egcs-1.1.2) on i386 miscompiles this function when i is
 308      a 64-bit bfd_size_type: a 64-bit target or --enable-64-bit-bfd.
 309      Besides, indexing with a long long wouldn't give anything but extra
 310      cycles.  */
 311   size_t i;
 312
 313   /* Sort the strings by suffix and length.  */
 314   amt = tab->size * sizeof (struct elf_strtab_hash_entry *);
 315   array = (struct elf_strtab_hash_entry **) bfd_malloc (amt);
 316   if (array == NULL)
 317     goto alloc_failure;
 318
 319   for (i = 1, a = array; i < tab->size; ++i)
 320     {
 321       e = tab->array[i];
 322       if (e->refcount)
 323         {
 324           *a++ = e;
 325           /* Adjust the length to not include the zero terminator.  */
 326           e->len -= 1;
 327         }
 328       else
 329         e->len = 0;
 330     }
 331
 332   size = a - array;
 333   if (size != 0)
 334     {
 335       qsort (array, size, sizeof (struct elf_strtab_hash_entry *), strrevcmp);
 336
 337       /* Loop over the sorted array and merge suffixes.  Start from the
 338          end because we want eg.
 339
 340          s1 -> "d"
 341          s2 -> "bcd"
 342          s3 -> "abcd"
 343
 344          to end up as
 345
 346          s3 -> "abcd"
 347          s2 _____^
 348          s1 _______^
 349
 350          ie. we don't want s1 pointing into the old s2.  */
 351       e = *--a;
 352       e->len += 1;
 353       while (--a >= array)
 354         {
 355           struct elf_strtab_hash_entry *cmp = *a;
 356
 357           cmp->len += 1;
 358           if (is_suffix (e, cmp))
 359             {
 360               cmp->u.suffix = e;
 361               cmp->len = -cmp->len;
 362             }
 363           else
 364             e = cmp;
 365         }
 366     }
 367
 368 alloc_failure:
 369   if (array)
 370     free (array);
 371
 372   /* Assign positions to the strings we want to keep.  */
 373   size = 1;
 374   for (i = 1; i < tab->size; ++i)
 375     {
 376       e = tab->array[i];
 377       if (e->refcount && e->len > 0)
 378         {
 379           e->u.index = size;
 380           size += e->len;
 381         }
 382     }
 383
 384   tab->sec_size = size;
 385
 386   /* Adjust the rest.  */
 387   for (i = 1; i < tab->size; ++i)
 388     {
 389       e = tab->array[i];
 390       if (e->refcount && e->len < 0)
 391         e->u.index = e->u.suffix->u.index + (e->u.suffix->len + e->len);
 392     }
 393 }