bfd/merge.c

   1 /* SEC_MERGE support.
   2    Copyright (C) 2001-2018 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
  23 /* This file contains support for merging duplicate entities within sections,
  24    as used in ELF SHF_MERGE.  */
  25
  26 #include "sysdep.h"
  27 #include "bfd.h"
  28 #include "elf-bfd.h"
  29 #include "libbfd.h"
  30 #include "hashtab.h"
  31 #include "libiberty.h"
  32
  33 struct sec_merge_sec_info;
  34
  35 /* An entry in the section merge hash table.  */
  36
  37 struct sec_merge_hash_entry
  38 {
  39   struct bfd_hash_entry root;
  40   /* Length of this entry.  This includes the zero terminator.  */
  41   unsigned int len;
  42   /* Start of this string needs to be aligned to
  43      alignment octets (not 1 << align).  */
  44   unsigned int alignment;
  45   union
  46   {
  47     /* Index within the merged section.  */
  48     bfd_size_type index;
  49     /* Entry this is a suffix of (if alignment is 0).  */
  50     struct sec_merge_hash_entry *suffix;
  51   } u;
  52   /* Which section is it in.  */
  53   struct sec_merge_sec_info *secinfo;
  54   /* Next entity in the hash table.  */
  55   struct sec_merge_hash_entry *next;
  56 };
  57
  58 /* The section merge hash table.  */
  59
  60 struct sec_merge_hash
  61 {
  62   struct bfd_hash_table table;
  63   /* Next available index.  */
  64   bfd_size_type size;
  65   /* First entity in the SEC_MERGE sections of this type.  */
  66   struct sec_merge_hash_entry *first;
  67   /* Last entity in the SEC_MERGE sections of this type.  */
  68   struct sec_merge_hash_entry *last;
  69   /* Entity size.  */
  70   unsigned int entsize;
  71   /* Are entries fixed size or zero terminated strings?  */
  72   bfd_boolean strings;
  73 };
  74
  75 struct sec_merge_info
  76 {
  77   /* Chain of sec_merge_infos.  */
  78   struct sec_merge_info *next;
  79   /* Chain of sec_merge_sec_infos.  */
  80   struct sec_merge_sec_info *chain;
  81   /* A hash table used to hold section content.  */
  82   struct sec_merge_hash *htab;
  83 };
  84
  85 struct sec_merge_sec_info
  86 {
  87   /* Chain of sec_merge_sec_infos.  */
  88   struct sec_merge_sec_info *next;
  89   /* The corresponding section.  */
  90   asection *sec;
  91   /* Pointer to merge_info pointing to us.  */
  92   void **psecinfo;
  93   /* A hash table used to hold section content.  */
  94   struct sec_merge_hash *htab;
  95   /* First string in this section.  */
  96   struct sec_merge_hash_entry *first_str;
  97   /* Original section content.  */
  98   unsigned char contents[1];
  99 };
 100
 101
 102 /* Routine to create an entry in a section merge hashtab.  */
 103
 104 static struct bfd_hash_entry *
 105 sec_merge_hash_newfunc (struct bfd_hash_entry *entry,
 106                         struct bfd_hash_table *table, const char *string)
 107 {
 108   /* Allocate the structure if it has not already been allocated by a
 109      subclass.  */
 110   if (entry == NULL)
 111     entry = (struct bfd_hash_entry *)
 112         bfd_hash_allocate (table, sizeof (struct sec_merge_hash_entry));
 113   if (entry == NULL)
 114     return NULL;
 115
 116   /* Call the allocation method of the superclass.  */
 117   entry = bfd_hash_newfunc (entry, table, string);
 118
 119   if (entry != NULL)
 120     {
 121       /* Initialize the local fields.  */
 122       struct sec_merge_hash_entry *ret = (struct sec_merge_hash_entry *) entry;
 123
 124       ret->u.suffix = NULL;
 125       ret->alignment = 0;
 126       ret->secinfo = NULL;
 127       ret->next = NULL;
 128     }
 129
 130   return entry;
 131 }
 132
 133 /* Look up an entry in a section merge hash table.  */
 134
 135 static struct sec_merge_hash_entry *
 136 sec_merge_hash_lookup (struct sec_merge_hash *table, const char *string,
 137                        unsigned int alignment, bfd_boolean create)
 138 {
 139   const unsigned char *s;
 140   unsigned long hash;
 141   unsigned int c;
 142   struct sec_merge_hash_entry *hashp;
 143   unsigned int len, i;
 144   unsigned int _index;
 145
 146   hash = 0;
 147   len = 0;
 148   s = (const unsigned char *) string;
 149   if (table->strings)
 150     {
 151       if (table->entsize == 1)
 152         {
 153           while ((c = *s++) != '\0')
 154             {
 155               hash += c + (c << 17);
 156               hash ^= hash >> 2;
 157               ++len;
 158             }
 159           hash += len + (len << 17);
 160         }
 161       else
 162         {
 163           for (;;)
 164             {
 165               for (i = 0; i < table->entsize; ++i)
 166                 if (s[i] != '\0')
 167                   break;
 168               if (i == table->entsize)
 169                 break;
 170               for (i = 0; i < table->entsize; ++i)
 171                 {
 172                   c = *s++;
 173                   hash += c + (c << 17);
 174                   hash ^= hash >> 2;
 175                 }
 176               ++len;
 177             }
 178           hash += len + (len << 17);
 179           len *= table->entsize;
 180         }
 181       hash ^= hash >> 2;
 182       len += table->entsize;
 183     }
 184   else
 185     {
 186       for (i = 0; i < table->entsize; ++i)
 187         {
 188           c = *s++;
 189           hash += c + (c << 17);
 190           hash ^= hash >> 2;
 191         }
 192       len = table->entsize;
 193     }
 194
 195   _index = hash % table->table.size;
 196   for (hashp = (struct sec_merge_hash_entry *) table->table.table[_index];
 197        hashp != NULL;
 198        hashp = (struct sec_merge_hash_entry *) hashp->root.next)
 199     {
 200       if (hashp->root.hash == hash
 201           && len == hashp->len
 202           && memcmp (hashp->root.string, string, len) == 0)
 203         {
 204           /* If the string we found does not have at least the required
 205              alignment, we need to insert another copy.  */
 206           if (hashp->alignment < alignment)
 207             {
 208               if (create)
 209                 {
 210                   /*  Mark the less aligned copy as deleted.  */
 211                   hashp->len = 0;
 212                   hashp->alignment = 0;
 213                 }
 214               break;
 215             }
 216           return hashp;
 217         }
 218     }
 219
 220   if (! create)
 221     return NULL;
 222
 223   hashp = ((struct sec_merge_hash_entry *)
 224            bfd_hash_insert (&table->table, string, hash));
 225   if (hashp == NULL)
 226     return NULL;
 227   hashp->len = len;
 228   hashp->alignment = alignment;
 229   return hashp;
 230 }
 231
 232 /* Create a new hash table.  */
 233
 234 static struct sec_merge_hash *
 235 sec_merge_init (unsigned int entsize, bfd_boolean strings)
 236 {
 237   struct sec_merge_hash *table;
 238
 239   table = (struct sec_merge_hash *) bfd_malloc (sizeof (struct sec_merge_hash));
 240   if (table == NULL)
 241     return NULL;
 242
 243   if (! bfd_hash_table_init_n (&table->table, sec_merge_hash_newfunc,
 244                                sizeof (struct sec_merge_hash_entry), 16699))
 245     {
 246       free (table);
 247       return NULL;
 248     }
 249
 250   table->size = 0;
 251   table->first = NULL;
 252   table->last = NULL;
 253   table->entsize = entsize;
 254   table->strings = strings;
 255
 256   return table;
 257 }
 258
 259 /* Get the index of an entity in a hash table, adding it if it is not
 260    already present.  */
 261
 262 static struct sec_merge_hash_entry *
 263 sec_merge_add (struct sec_merge_hash *tab, const char *str,
 264                unsigned int alignment, struct sec_merge_sec_info *secinfo)
 265 {
 266   struct sec_merge_hash_entry *entry;
 267
 268   entry = sec_merge_hash_lookup (tab, str, alignment, TRUE);
 269   if (entry == NULL)
 270     return NULL;
 271
 272   if (entry->secinfo == NULL)
 273     {
 274       tab->size++;
 275       entry->secinfo = secinfo;
 276       if (tab->first == NULL)
 277         tab->first = entry;
 278       else
 279         tab->last->next = entry;
 280       tab->last = entry;
 281     }
 282
 283   return entry;
 284 }
 285
 286 static bfd_boolean
 287 sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry,
 288                 unsigned char *contents, file_ptr offset)
 289 {
 290   struct sec_merge_sec_info *secinfo = entry->secinfo;
 291   asection *sec = secinfo->sec;
 292   char *pad = NULL;
 293   bfd_size_type off = 0;
 294   int alignment_power = sec->output_section->alignment_power;
 295   bfd_size_type pad_len;
 296
 297   /* FIXME: If alignment_power is 0 then really we should scan the
 298      entry list for the largest required alignment and use that.  */
 299   pad_len = alignment_power ? ((bfd_size_type) 1 << alignment_power) : 16;
 300
 301   pad = (char *) bfd_zmalloc (pad_len);
 302   if (pad == NULL)
 303     return FALSE;
 304
 305   for (; entry != NULL && entry->secinfo == secinfo; entry = entry->next)
 306     {
 307       const char *str;
 308       bfd_size_type len;
 309
 310       len = -off & (entry->alignment - 1);
 311       if (len != 0)
 312         {
 313           BFD_ASSERT (len <= pad_len);
 314           if (contents)
 315             {
 316               memcpy (contents + offset, pad, len);
 317               offset += len;
 318             }
 319           else if (bfd_bwrite (pad, len, abfd) != len)
 320             goto err;
 321           off += len;
 322         }
 323
 324       str = entry->root.string;
 325       len = entry->len;
 326
 327       if (contents)
 328         {
 329           memcpy (contents + offset, str, len);
 330           offset += len;
 331         }
 332       else if (bfd_bwrite (str, len, abfd) != len)
 333         goto err;
 334
 335       off += len;
 336     }
 337
 338   /* Trailing alignment needed?  */
 339   off = sec->size - off;
 340   if (off != 0)
 341     {
 342       BFD_ASSERT (off <= pad_len);
 343       if (contents)
 344         memcpy (contents + offset, pad, off);
 345       else if (bfd_bwrite (pad, off, abfd) != off)
 346         goto err;
 347     }
 348
 349   free (pad);
 350   return TRUE;
 351
 352  err:
 353   free (pad);
 354   return FALSE;
 355 }
 356
 357 /* Register a SEC_MERGE section as a candidate for merging.
 358    This function is called for all non-dynamic SEC_MERGE input sections.  */
 359
 360 bfd_boolean
 361 _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
 362                         void **psecinfo)
 363 {
 364   struct sec_merge_info *sinfo;
 365   struct sec_merge_sec_info *secinfo;
 366   unsigned int align;
 367   bfd_size_type amt;
 368   bfd_byte *contents;
 369
 370   if ((abfd->flags & DYNAMIC) != 0
 371       || (sec->flags & SEC_MERGE) == 0)
 372     abort ();
 373
 374   if (sec->size == 0
 375       || (sec->flags & SEC_EXCLUDE) != 0
 376       || sec->entsize == 0)
 377     return TRUE;
 378
 379   if ((sec->flags & SEC_RELOC) != 0)
 380     {
 381       /* We aren't prepared to handle relocations in merged sections.  */
 382       return TRUE;
 383     }
 384
 385   align = sec->alignment_power;
 386   if ((sec->entsize < (unsigned) 1 << align
 387        && ((sec->entsize & (sec->entsize - 1))
 388            || !(sec->flags & SEC_STRINGS)))
 389       || (sec->entsize > (unsigned) 1 << align
 390           && (sec->entsize & (((unsigned) 1 << align) - 1))))
 391     {
 392       /* Sanity check.  If string character size is smaller than
 393          alignment, then we require character size to be a power
 394          of 2, otherwise character size must be integer multiple
 395          of alignment.  For non-string constants, alignment must
 396          be smaller than or equal to entity size and entity size
 397          must be integer multiple of alignment.  */
 398       return TRUE;
 399     }
 400
 401   for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
 402     if ((secinfo = sinfo->chain)
 403         && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
 404         && secinfo->sec->entsize == sec->entsize
 405         && secinfo->sec->alignment_power == sec->alignment_power
 406         && secinfo->sec->output_section == sec->output_section)
 407       break;
 408
 409   if (sinfo == NULL)
 410     {
 411       /* Initialize the information we need to keep track of.  */
 412       sinfo = (struct sec_merge_info *)
 413           bfd_alloc (abfd, sizeof (struct sec_merge_info));
 414       if (sinfo == NULL)
 415         goto error_return;
 416       sinfo->next = (struct sec_merge_info *) *psinfo;
 417       sinfo->chain = NULL;
 418       *psinfo = sinfo;
 419       sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
 420       if (sinfo->htab == NULL)
 421         goto error_return;
 422     }
 423
 424   /* Read the section from abfd.  */
 425
 426   amt = sizeof (struct sec_merge_sec_info) - 1 + sec->size;
 427   if (sec->flags & SEC_STRINGS)
 428     /* Some versions of gcc may emit a string without a zero terminator.
 429        See http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01004.html
 430        Allocate space for an extra zero.  */
 431     amt += sec->entsize;
 432   *psecinfo = bfd_alloc (abfd, amt);
 433   if (*psecinfo == NULL)
 434     goto error_return;
 435
 436   secinfo = (struct sec_merge_sec_info *) *psecinfo;
 437   if (sinfo->chain)
 438     {
 439       secinfo->next = sinfo->chain->next;
 440       sinfo->chain->next = secinfo;
 441     }
 442   else
 443     secinfo->next = secinfo;
 444   sinfo->chain = secinfo;
 445   secinfo->sec = sec;
 446   secinfo->psecinfo = psecinfo;
 447   secinfo->htab = sinfo->htab;
 448   secinfo->first_str = NULL;
 449
 450   sec->rawsize = sec->size;
 451   if (sec->flags & SEC_STRINGS)
 452     memset (secinfo->contents + sec->size, 0, sec->entsize);
 453   contents = secinfo->contents;
 454   if (! bfd_get_full_section_contents (sec->owner, sec, &contents))
 455     goto error_return;
 456
 457   return TRUE;
 458
 459  error_return:
 460   *psecinfo = NULL;
 461   return FALSE;
 462 }
 463
 464 /* Record one section into the hash table.  */
 465 static bfd_boolean
 466 record_section (struct sec_merge_info *sinfo,
 467                 struct sec_merge_sec_info *secinfo)
 468 {
 469   asection *sec = secinfo->sec;
 470   struct sec_merge_hash_entry *entry;
 471   bfd_boolean nul;
 472   unsigned char *p, *end;
 473   bfd_vma mask, eltalign;
 474   unsigned int align, i;
 475
 476   align = sec->alignment_power;
 477   end = secinfo->contents + sec->size;
 478   nul = FALSE;
 479   mask = ((bfd_vma) 1 << align) - 1;
 480   if (sec->flags & SEC_STRINGS)
 481     {
 482       for (p = secinfo->contents; p < end; )
 483         {
 484           eltalign = p - secinfo->contents;
 485           eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
 486           if (!eltalign || eltalign > mask)
 487             eltalign = mask + 1;
 488           entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
 489                                  secinfo);
 490           if (! entry)
 491             goto error_return;
 492           p += entry->len;
 493           if (sec->entsize == 1)
 494             {
 495               while (p < end && *p == 0)
 496                 {
 497                   if (!nul && !((p - secinfo->contents) & mask))
 498                     {
 499                       nul = TRUE;
 500                       entry = sec_merge_add (sinfo->htab, "",
 501                                              (unsigned) mask + 1, secinfo);
 502                       if (! entry)
 503                         goto error_return;
 504                     }
 505                   p++;
 506                 }
 507             }
 508           else
 509             {
 510               while (p < end)
 511                 {
 512                   for (i = 0; i < sec->entsize; i++)
 513                     if (p[i] != '\0')
 514                       break;
 515                   if (i != sec->entsize)
 516                     break;
 517                   if (!nul && !((p - secinfo->contents) & mask))
 518                     {
 519                       nul = TRUE;
 520                       entry = sec_merge_add (sinfo->htab, (char *) p,
 521                                              (unsigned) mask + 1, secinfo);
 522                       if (! entry)
 523                         goto error_return;
 524                     }
 525                   p += sec->entsize;
 526                 }
 527             }
 528         }
 529     }
 530   else
 531     {
 532       for (p = secinfo->contents; p < end; p += sec->entsize)
 533         {
 534           entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
 535           if (! entry)
 536             goto error_return;
 537         }
 538     }
 539
 540   return TRUE;
 541
 542 error_return:
 543   for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 544     *secinfo->psecinfo = NULL;
 545   return FALSE;
 546 }
 547
 548 static int
 549 strrevcmp (const void *a, const void *b)
 550 {
 551   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 552   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 553   unsigned int lenA = A->len;
 554   unsigned int lenB = B->len;
 555   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 556   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 557   int l = lenA < lenB ? lenA : lenB;
 558
 559   while (l)
 560     {
 561       if (*s != *t)
 562         return (int) *s - (int) *t;
 563       s--;
 564       t--;
 565       l--;
 566     }
 567   return lenA - lenB;
 568 }
 569
 570 /* Like strrevcmp, but for the case where all strings have the same
 571    alignment > entsize.  */
 572
 573 static int
 574 strrevcmp_align (const void *a, const void *b)
 575 {
 576   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 577   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 578   unsigned int lenA = A->len;
 579   unsigned int lenB = B->len;
 580   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 581   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 582   int l = lenA < lenB ? lenA : lenB;
 583   int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
 584
 585   if (tail_align != 0)
 586     return tail_align;
 587
 588   while (l)
 589     {
 590       if (*s != *t)
 591         return (int) *s - (int) *t;
 592       s--;
 593       t--;
 594       l--;
 595     }
 596   return lenA - lenB;
 597 }
 598
 599 static inline int
 600 is_suffix (const struct sec_merge_hash_entry *A,
 601            const struct sec_merge_hash_entry *B)
 602 {
 603   if (A->len <= B->len)
 604     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 605        not to be equal by the hash table.  */
 606     return 0;
 607
 608   return memcmp (A->root.string + (A->len - B->len),
 609                  B->root.string, B->len) == 0;
 610 }
 611
 612 /* This is a helper function for _bfd_merge_sections.  It attempts to
 613    merge strings matching suffixes of longer strings.  */
 614 static bfd_boolean
 615 merge_strings (struct sec_merge_info *sinfo)
 616 {
 617   struct sec_merge_hash_entry **array, **a, *e;
 618   struct sec_merge_sec_info *secinfo;
 619   bfd_size_type size, amt;
 620   unsigned int alignment = 0;
 621
 622   /* Now sort the strings */
 623   amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
 624   array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
 625   if (array == NULL)
 626     return FALSE;
 627
 628   for (e = sinfo->htab->first, a = array; e; e = e->next)
 629     if (e->alignment)
 630       {
 631         *a++ = e;
 632         /* Adjust the length to not include the zero terminator.  */
 633         e->len -= sinfo->htab->entsize;
 634         if (alignment != e->alignment)
 635           {
 636             if (alignment == 0)
 637               alignment = e->alignment;
 638             else
 639               alignment = (unsigned) -1;
 640           }
 641       }
 642
 643   sinfo->htab->size = a - array;
 644   if (sinfo->htab->size != 0)
 645     {
 646       qsort (array, (size_t) sinfo->htab->size,
 647              sizeof (struct sec_merge_hash_entry *),
 648              (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
 649               ? strrevcmp_align : strrevcmp));
 650
 651       /* Loop over the sorted array and merge suffixes */
 652       e = *--a;
 653       e->len += sinfo->htab->entsize;
 654       while (--a >= array)
 655         {
 656           struct sec_merge_hash_entry *cmp = *a;
 657
 658           cmp->len += sinfo->htab->entsize;
 659           if (e->alignment >= cmp->alignment
 660               && !((e->len - cmp->len) & (cmp->alignment - 1))
 661               && is_suffix (e, cmp))
 662             {
 663               cmp->u.suffix = e;
 664               cmp->alignment = 0;
 665             }
 666           else
 667             e = cmp;
 668         }
 669     }
 670
 671   free (array);
 672
 673   /* Now assign positions to the strings we want to keep.  */
 674   size = 0;
 675   secinfo = sinfo->htab->first->secinfo;
 676   for (e = sinfo->htab->first; e; e = e->next)
 677     {
 678       if (e->secinfo != secinfo)
 679         {
 680           secinfo->sec->size = size;
 681           secinfo = e->secinfo;
 682         }
 683       if (e->alignment)
 684         {
 685           if (e->secinfo->first_str == NULL)
 686             {
 687               e->secinfo->first_str = e;
 688               size = 0;
 689             }
 690           size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 691           e->u.index = size;
 692           size += e->len;
 693         }
 694     }
 695   secinfo->sec->size = size;
 696   if (secinfo->sec->alignment_power != 0)
 697     {
 698       bfd_size_type align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
 699       secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
 700     }
 701
 702   /* And now adjust the rest, removing them from the chain (but not hashtable)
 703      at the same time.  */
 704   for (a = &sinfo->htab->first, e = *a; e; e = e->next)
 705     if (e->alignment)
 706       a = &e->next;
 707     else
 708       {
 709         *a = e->next;
 710         if (e->len)
 711           {
 712             e->secinfo = e->u.suffix->secinfo;
 713             e->alignment = e->u.suffix->alignment;
 714             e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
 715           }
 716       }
 717   return TRUE;
 718 }
 719
 720 /* This function is called once after all SEC_MERGE sections are registered
 721    with _bfd_merge_section.  */
 722
 723 bfd_boolean
 724 _bfd_merge_sections (bfd *abfd,
 725                      struct bfd_link_info *info ATTRIBUTE_UNUSED,
 726                      void *xsinfo,
 727                      void (*remove_hook) (bfd *, asection *))
 728 {
 729   struct sec_merge_info *sinfo;
 730
 731   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 732     {
 733       struct sec_merge_sec_info * secinfo;
 734
 735       if (! sinfo->chain)
 736         continue;
 737
 738       /* Move sinfo->chain to head of the chain, terminate it.  */
 739       secinfo = sinfo->chain;
 740       sinfo->chain = secinfo->next;
 741       secinfo->next = NULL;
 742
 743       /* Record the sections into the hash table.  */
 744       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 745         if (secinfo->sec->flags & SEC_EXCLUDE)
 746           {
 747             *secinfo->psecinfo = NULL;
 748             if (remove_hook)
 749               (*remove_hook) (abfd, secinfo->sec);
 750           }
 751         else if (! record_section (sinfo, secinfo))
 752           return FALSE;
 753
 754       if (secinfo)
 755         continue;
 756
 757       if (sinfo->htab->first == NULL)
 758         continue;
 759
 760       if (sinfo->htab->strings)
 761         {
 762           if (!merge_strings (sinfo))
 763             return FALSE;
 764         }
 765       else
 766         {
 767           struct sec_merge_hash_entry *e;
 768           bfd_size_type size = 0;
 769
 770           /* Things are much simpler for non-strings.
 771              Just assign them slots in the section.  */
 772           secinfo = NULL;
 773           for (e = sinfo->htab->first; e; e = e->next)
 774             {
 775               if (e->secinfo->first_str == NULL)
 776                 {
 777                   if (secinfo)
 778                     secinfo->sec->size = size;
 779                   e->secinfo->first_str = e;
 780                   size = 0;
 781                 }
 782               size = (size + e->alignment - 1)
 783                      & ~((bfd_vma) e->alignment - 1);
 784               e->u.index = size;
 785               size += e->len;
 786               secinfo = e->secinfo;
 787             }
 788           secinfo->sec->size = size;
 789         }
 790
 791         /* Finally remove all input sections which have not made it into
 792            the hash table at all.  */
 793         for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 794           if (secinfo->first_str == NULL)
 795             secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
 796     }
 797
 798   return TRUE;
 799 }
 800
 801 /* Write out the merged section.  */
 802
 803 bfd_boolean
 804 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
 805 {
 806   struct sec_merge_sec_info *secinfo;
 807   file_ptr pos;
 808   unsigned char *contents;
 809   Elf_Internal_Shdr *hdr;
 810
 811   secinfo = (struct sec_merge_sec_info *) psecinfo;
 812
 813   if (!secinfo)
 814     return FALSE;
 815
 816   if (secinfo->first_str == NULL)
 817     return TRUE;
 818
 819   /* FIXME: octets_per_byte.  */
 820   hdr = &elf_section_data (sec->output_section)->this_hdr;
 821   if (hdr->sh_offset == (file_ptr) -1)
 822     {
 823       /* We must compress this section.  Write output to the
 824          buffer.  */
 825       contents = hdr->contents;
 826       if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
 827           || contents == NULL)
 828         abort ();
 829     }
 830   else
 831     {
 832       contents = NULL;
 833       pos = sec->output_section->filepos + sec->output_offset;
 834       if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
 835         return FALSE;
 836     }
 837
 838   if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
 839                         sec->output_offset))
 840     return FALSE;
 841
 842   return TRUE;
 843 }
 844
 845 /* Adjust an address in the SEC_MERGE section.  Given OFFSET within
 846    *PSEC, this returns the new offset in the adjusted SEC_MERGE
 847    section and writes the new section back into *PSEC.  */
 848
 849 bfd_vma
 850 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
 851                             void *psecinfo, bfd_vma offset)
 852 {
 853   struct sec_merge_sec_info *secinfo;
 854   struct sec_merge_hash_entry *entry;
 855   unsigned char *p;
 856   asection *sec = *psec;
 857
 858   secinfo = (struct sec_merge_sec_info *) psecinfo;
 859
 860   if (!secinfo)
 861     return offset;
 862
 863   if (offset >= sec->rawsize)
 864     {
 865       if (offset > sec->rawsize)
 866         _bfd_error_handler
 867           /* xgettext:c-format */
 868           (_("%B: access beyond end of merged section (%Ld)"),
 869            sec->owner, offset);
 870       return secinfo->first_str ? sec->size : 0;
 871     }
 872
 873   if (secinfo->htab->strings)
 874     {
 875       if (sec->entsize == 1)
 876         {
 877           p = secinfo->contents + offset - 1;
 878           while (p >= secinfo->contents && *p)
 879             --p;
 880           ++p;
 881         }
 882       else
 883         {
 884           p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 885           p -= sec->entsize;
 886           while (p >= secinfo->contents)
 887             {
 888               unsigned int i;
 889
 890               for (i = 0; i < sec->entsize; ++i)
 891                 if (p[i] != '\0')
 892                   break;
 893               if (i == sec->entsize)
 894                 break;
 895               p -= sec->entsize;
 896             }
 897           p += sec->entsize;
 898         }
 899     }
 900   else
 901     {
 902       p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 903     }
 904   entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
 905   if (!entry)
 906     {
 907       if (! secinfo->htab->strings)
 908         abort ();
 909       /* This should only happen if somebody points into the padding
 910          after a NUL character but before next entity.  */
 911       if (*p)
 912         abort ();
 913       if (! secinfo->htab->first)
 914         abort ();
 915       entry = secinfo->htab->first;
 916       p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
 917            - entry->len);
 918     }
 919
 920   *psec = entry->secinfo->sec;
 921   return entry->u.index + (secinfo->contents + offset - p);
 922 }
 923
 924 /* Tidy up when done.  */
 925
 926 void
 927 _bfd_merge_sections_free (void *xsinfo)
 928 {
 929   struct sec_merge_info *sinfo;
 930
 931   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 932     {
 933       bfd_hash_table_free (&sinfo->htab->table);
 934       free (sinfo->htab);
 935     }
 936 }