bfd/merge.c

   1 /* SEC_MERGE support.
   2    Copyright (C) 2001-2017 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
 296   if (alignment_power)
 297     {
 298       pad = (char *) bfd_zmalloc ((bfd_size_type) 1 << alignment_power);
 299       if (pad == NULL)
 300         return FALSE;
 301     }
 302
 303   for (; entry != NULL && entry->secinfo == secinfo; entry = entry->next)
 304     {
 305       const char *str;
 306       bfd_size_type len;
 307
 308       len = -off & (entry->alignment - 1);
 309       if (len != 0)
 310         {
 311           if (contents)
 312             {
 313               memcpy (contents + offset, pad, len);
 314               offset += len;
 315             }
 316           else if (bfd_bwrite (pad, len, abfd) != len)
 317             goto err;
 318           off += len;
 319         }
 320
 321       str = entry->root.string;
 322       len = entry->len;
 323
 324       if (contents)
 325         {
 326           memcpy (contents + offset, str, len);
 327           offset += len;
 328         }
 329       else if (bfd_bwrite (str, len, abfd) != len)
 330         goto err;
 331
 332       off += len;
 333     }
 334
 335   /* Trailing alignment needed?  */
 336   off = sec->size - off;
 337   if (off != 0)
 338     {
 339       if (contents)
 340         memcpy (contents + offset, pad, off);
 341       else if (bfd_bwrite (pad, off, abfd) != off)
 342         goto err;
 343     }
 344
 345   if (pad != NULL)
 346     free (pad);
 347   return TRUE;
 348
 349  err:
 350   if (pad != NULL)
 351     free (pad);
 352   return FALSE;
 353 }
 354
 355 /* Register a SEC_MERGE section as a candidate for merging.
 356    This function is called for all non-dynamic SEC_MERGE input sections.  */
 357
 358 bfd_boolean
 359 _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
 360                         void **psecinfo)
 361 {
 362   struct sec_merge_info *sinfo;
 363   struct sec_merge_sec_info *secinfo;
 364   unsigned int align;
 365   bfd_size_type amt;
 366   bfd_byte *contents;
 367
 368   if ((abfd->flags & DYNAMIC) != 0
 369       || (sec->flags & SEC_MERGE) == 0)
 370     abort ();
 371
 372   if (sec->size == 0
 373       || (sec->flags & SEC_EXCLUDE) != 0
 374       || sec->entsize == 0)
 375     return TRUE;
 376
 377   if ((sec->flags & SEC_RELOC) != 0)
 378     {
 379       /* We aren't prepared to handle relocations in merged sections.  */
 380       return TRUE;
 381     }
 382
 383   align = sec->alignment_power;
 384   if ((sec->entsize < (unsigned) 1 << align
 385        && ((sec->entsize & (sec->entsize - 1))
 386            || !(sec->flags & SEC_STRINGS)))
 387       || (sec->entsize > (unsigned) 1 << align
 388           && (sec->entsize & (((unsigned) 1 << align) - 1))))
 389     {
 390       /* Sanity check.  If string character size is smaller than
 391          alignment, then we require character size to be a power
 392          of 2, otherwise character size must be integer multiple
 393          of alignment.  For non-string constants, alignment must
 394          be smaller than or equal to entity size and entity size
 395          must be integer multiple of alignment.  */
 396       return TRUE;
 397     }
 398
 399   for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
 400     if ((secinfo = sinfo->chain)
 401         && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
 402         && secinfo->sec->entsize == sec->entsize
 403         && secinfo->sec->alignment_power == sec->alignment_power
 404         && secinfo->sec->output_section == sec->output_section)
 405       break;
 406
 407   if (sinfo == NULL)
 408     {
 409       /* Initialize the information we need to keep track of.  */
 410       sinfo = (struct sec_merge_info *)
 411           bfd_alloc (abfd, sizeof (struct sec_merge_info));
 412       if (sinfo == NULL)
 413         goto error_return;
 414       sinfo->next = (struct sec_merge_info *) *psinfo;
 415       sinfo->chain = NULL;
 416       *psinfo = sinfo;
 417       sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
 418       if (sinfo->htab == NULL)
 419         goto error_return;
 420     }
 421
 422   /* Read the section from abfd.  */
 423
 424   amt = sizeof (struct sec_merge_sec_info) - 1 + sec->size;
 425   if (sec->flags & SEC_STRINGS)
 426     /* Some versions of gcc may emit a string without a zero terminator.
 427        See http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01004.html
 428        Allocate space for an extra zero.  */
 429     amt += sec->entsize;
 430   *psecinfo = bfd_alloc (abfd, amt);
 431   if (*psecinfo == NULL)
 432     goto error_return;
 433
 434   secinfo = (struct sec_merge_sec_info *) *psecinfo;
 435   if (sinfo->chain)
 436     {
 437       secinfo->next = sinfo->chain->next;
 438       sinfo->chain->next = secinfo;
 439     }
 440   else
 441     secinfo->next = secinfo;
 442   sinfo->chain = secinfo;
 443   secinfo->sec = sec;
 444   secinfo->psecinfo = psecinfo;
 445   secinfo->htab = sinfo->htab;
 446   secinfo->first_str = NULL;
 447
 448   sec->rawsize = sec->size;
 449   if (sec->flags & SEC_STRINGS)
 450     memset (secinfo->contents + sec->size, 0, sec->entsize);
 451   contents = secinfo->contents;
 452   if (! bfd_get_full_section_contents (sec->owner, sec, &contents))
 453     goto error_return;
 454
 455   return TRUE;
 456
 457  error_return:
 458   *psecinfo = NULL;
 459   return FALSE;
 460 }
 461
 462 /* Record one section into the hash table.  */
 463 static bfd_boolean
 464 record_section (struct sec_merge_info *sinfo,
 465                 struct sec_merge_sec_info *secinfo)
 466 {
 467   asection *sec = secinfo->sec;
 468   struct sec_merge_hash_entry *entry;
 469   bfd_boolean nul;
 470   unsigned char *p, *end;
 471   bfd_vma mask, eltalign;
 472   unsigned int align, i;
 473
 474   align = sec->alignment_power;
 475   end = secinfo->contents + sec->size;
 476   nul = FALSE;
 477   mask = ((bfd_vma) 1 << align) - 1;
 478   if (sec->flags & SEC_STRINGS)
 479     {
 480       for (p = secinfo->contents; p < end; )
 481         {
 482           eltalign = p - secinfo->contents;
 483           eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
 484           if (!eltalign || eltalign > mask)
 485             eltalign = mask + 1;
 486           entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
 487                                  secinfo);
 488           if (! entry)
 489             goto error_return;
 490           p += entry->len;
 491           if (sec->entsize == 1)
 492             {
 493               while (p < end && *p == 0)
 494                 {
 495                   if (!nul && !((p - secinfo->contents) & mask))
 496                     {
 497                       nul = TRUE;
 498                       entry = sec_merge_add (sinfo->htab, "",
 499                                              (unsigned) mask + 1, secinfo);
 500                       if (! entry)
 501                         goto error_return;
 502                     }
 503                   p++;
 504                 }
 505             }
 506           else
 507             {
 508               while (p < end)
 509                 {
 510                   for (i = 0; i < sec->entsize; i++)
 511                     if (p[i] != '\0')
 512                       break;
 513                   if (i != sec->entsize)
 514                     break;
 515                   if (!nul && !((p - secinfo->contents) & mask))
 516                     {
 517                       nul = TRUE;
 518                       entry = sec_merge_add (sinfo->htab, (char *) p,
 519                                              (unsigned) mask + 1, secinfo);
 520                       if (! entry)
 521                         goto error_return;
 522                     }
 523                   p += sec->entsize;
 524                 }
 525             }
 526         }
 527     }
 528   else
 529     {
 530       for (p = secinfo->contents; p < end; p += sec->entsize)
 531         {
 532           entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
 533           if (! entry)
 534             goto error_return;
 535         }
 536     }
 537
 538   return TRUE;
 539
 540 error_return:
 541   for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 542     *secinfo->psecinfo = NULL;
 543   return FALSE;
 544 }
 545
 546 static int
 547 strrevcmp (const void *a, const void *b)
 548 {
 549   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 550   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 551   unsigned int lenA = A->len;
 552   unsigned int lenB = B->len;
 553   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 554   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 555   int l = lenA < lenB ? lenA : lenB;
 556
 557   while (l)
 558     {
 559       if (*s != *t)
 560         return (int) *s - (int) *t;
 561       s--;
 562       t--;
 563       l--;
 564     }
 565   return lenA - lenB;
 566 }
 567
 568 /* Like strrevcmp, but for the case where all strings have the same
 569    alignment > entsize.  */
 570
 571 static int
 572 strrevcmp_align (const void *a, const void *b)
 573 {
 574   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 575   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 576   unsigned int lenA = A->len;
 577   unsigned int lenB = B->len;
 578   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 579   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 580   int l = lenA < lenB ? lenA : lenB;
 581   int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
 582
 583   if (tail_align != 0)
 584     return tail_align;
 585
 586   while (l)
 587     {
 588       if (*s != *t)
 589         return (int) *s - (int) *t;
 590       s--;
 591       t--;
 592       l--;
 593     }
 594   return lenA - lenB;
 595 }
 596
 597 static inline int
 598 is_suffix (const struct sec_merge_hash_entry *A,
 599            const struct sec_merge_hash_entry *B)
 600 {
 601   if (A->len <= B->len)
 602     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 603        not to be equal by the hash table.  */
 604     return 0;
 605
 606   return memcmp (A->root.string + (A->len - B->len),
 607                  B->root.string, B->len) == 0;
 608 }
 609
 610 /* This is a helper function for _bfd_merge_sections.  It attempts to
 611    merge strings matching suffixes of longer strings.  */
 612 static void
 613 merge_strings (struct sec_merge_info *sinfo)
 614 {
 615   struct sec_merge_hash_entry **array, **a, *e;
 616   struct sec_merge_sec_info *secinfo;
 617   bfd_size_type size, amt;
 618   unsigned int alignment = 0;
 619
 620   /* Now sort the strings */
 621   amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
 622   array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
 623   if (array == NULL)
 624     goto alloc_failure;
 625
 626   for (e = sinfo->htab->first, a = array; e; e = e->next)
 627     if (e->alignment)
 628       {
 629         *a++ = e;
 630         /* Adjust the length to not include the zero terminator.  */
 631         e->len -= sinfo->htab->entsize;
 632         if (alignment != e->alignment)
 633           {
 634             if (alignment == 0)
 635               alignment = e->alignment;
 636             else
 637               alignment = (unsigned) -1;
 638           }
 639       }
 640
 641   sinfo->htab->size = a - array;
 642   if (sinfo->htab->size != 0)
 643     {
 644       qsort (array, (size_t) sinfo->htab->size,
 645              sizeof (struct sec_merge_hash_entry *),
 646              (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
 647               ? strrevcmp_align : strrevcmp));
 648
 649       /* Loop over the sorted array and merge suffixes */
 650       e = *--a;
 651       e->len += sinfo->htab->entsize;
 652       while (--a >= array)
 653         {
 654           struct sec_merge_hash_entry *cmp = *a;
 655
 656           cmp->len += sinfo->htab->entsize;
 657           if (e->alignment >= cmp->alignment
 658               && !((e->len - cmp->len) & (cmp->alignment - 1))
 659               && is_suffix (e, cmp))
 660             {
 661               cmp->u.suffix = e;
 662               cmp->alignment = 0;
 663             }
 664           else
 665             e = cmp;
 666         }
 667     }
 668
 669 alloc_failure:
 670   if (array)
 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 }
 718
 719 /* This function is called once after all SEC_MERGE sections are registered
 720    with _bfd_merge_section.  */
 721
 722 bfd_boolean
 723 _bfd_merge_sections (bfd *abfd,
 724                      struct bfd_link_info *info ATTRIBUTE_UNUSED,
 725                      void *xsinfo,
 726                      void (*remove_hook) (bfd *, asection *))
 727 {
 728   struct sec_merge_info *sinfo;
 729
 730   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 731     {
 732       struct sec_merge_sec_info * secinfo;
 733
 734       if (! sinfo->chain)
 735         continue;
 736
 737       /* Move sinfo->chain to head of the chain, terminate it.  */
 738       secinfo = sinfo->chain;
 739       sinfo->chain = secinfo->next;
 740       secinfo->next = NULL;
 741
 742       /* Record the sections into the hash table.  */
 743       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 744         if (secinfo->sec->flags & SEC_EXCLUDE)
 745           {
 746             *secinfo->psecinfo = NULL;
 747             if (remove_hook)
 748               (*remove_hook) (abfd, secinfo->sec);
 749           }
 750         else if (! record_section (sinfo, secinfo))
 751           break;
 752
 753       if (secinfo)
 754         continue;
 755
 756       if (sinfo->htab->first == NULL)
 757         continue;
 758
 759       if (sinfo->htab->strings)
 760         merge_strings (sinfo);
 761       else
 762         {
 763           struct sec_merge_hash_entry *e;
 764           bfd_size_type size = 0;
 765
 766           /* Things are much simpler for non-strings.
 767              Just assign them slots in the section.  */
 768           secinfo = NULL;
 769           for (e = sinfo->htab->first; e; e = e->next)
 770             {
 771               if (e->secinfo->first_str == NULL)
 772                 {
 773                   if (secinfo)
 774                     secinfo->sec->size = size;
 775                   e->secinfo->first_str = e;
 776                   size = 0;
 777                 }
 778               size = (size + e->alignment - 1)
 779                      & ~((bfd_vma) e->alignment - 1);
 780               e->u.index = size;
 781               size += e->len;
 782               secinfo = e->secinfo;
 783             }
 784           secinfo->sec->size = size;
 785         }
 786
 787         /* Finally remove all input sections which have not made it into
 788            the hash table at all.  */
 789         for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 790           if (secinfo->first_str == NULL)
 791             secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
 792     }
 793
 794   return TRUE;
 795 }
 796
 797 /* Write out the merged section.  */
 798
 799 bfd_boolean
 800 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
 801 {
 802   struct sec_merge_sec_info *secinfo;
 803   file_ptr pos;
 804   unsigned char *contents;
 805   Elf_Internal_Shdr *hdr;
 806
 807   secinfo = (struct sec_merge_sec_info *) psecinfo;
 808
 809   if (!secinfo)
 810     return FALSE;
 811
 812   if (secinfo->first_str == NULL)
 813     return TRUE;
 814
 815   /* FIXME: octets_per_byte.  */
 816   hdr = &elf_section_data (sec->output_section)->this_hdr;
 817   if (hdr->sh_offset == (file_ptr) -1)
 818     {
 819       /* We must compress this section.  Write output to the
 820          buffer.  */
 821       contents = hdr->contents;
 822       if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
 823           || contents == NULL)
 824         abort ();
 825     }
 826   else
 827     {
 828       contents = NULL;
 829       pos = sec->output_section->filepos + sec->output_offset;
 830       if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
 831         return FALSE;
 832     }
 833
 834   if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
 835                         sec->output_offset))
 836     return FALSE;
 837
 838   return TRUE;
 839 }
 840
 841 /* Adjust an address in the SEC_MERGE section.  Given OFFSET within
 842    *PSEC, this returns the new offset in the adjusted SEC_MERGE
 843    section and writes the new section back into *PSEC.  */
 844
 845 bfd_vma
 846 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
 847                             void *psecinfo, bfd_vma offset)
 848 {
 849   struct sec_merge_sec_info *secinfo;
 850   struct sec_merge_hash_entry *entry;
 851   unsigned char *p;
 852   asection *sec = *psec;
 853
 854   secinfo = (struct sec_merge_sec_info *) psecinfo;
 855
 856   if (!secinfo)
 857     return offset;
 858
 859   if (offset >= sec->rawsize)
 860     {
 861       if (offset > sec->rawsize)
 862         _bfd_error_handler
 863           /* xgettext:c-format */
 864           (_("%B: access beyond end of merged section (%Ld)"),
 865            sec->owner, offset);
 866       return secinfo->first_str ? sec->size : 0;
 867     }
 868
 869   if (secinfo->htab->strings)
 870     {
 871       if (sec->entsize == 1)
 872         {
 873           p = secinfo->contents + offset - 1;
 874           while (p >= secinfo->contents && *p)
 875             --p;
 876           ++p;
 877         }
 878       else
 879         {
 880           p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 881           p -= sec->entsize;
 882           while (p >= secinfo->contents)
 883             {
 884               unsigned int i;
 885
 886               for (i = 0; i < sec->entsize; ++i)
 887                 if (p[i] != '\0')
 888                   break;
 889               if (i == sec->entsize)
 890                 break;
 891               p -= sec->entsize;
 892             }
 893           p += sec->entsize;
 894         }
 895     }
 896   else
 897     {
 898       p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 899     }
 900   entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
 901   if (!entry)
 902     {
 903       if (! secinfo->htab->strings)
 904         abort ();
 905       /* This should only happen if somebody points into the padding
 906          after a NUL character but before next entity.  */
 907       if (*p)
 908         abort ();
 909       if (! secinfo->htab->first)
 910         abort ();
 911       entry = secinfo->htab->first;
 912       p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
 913            - entry->len);
 914     }
 915
 916   *psec = entry->secinfo->sec;
 917   return entry->u.index + (secinfo->contents + offset - p);
 918 }
 919
 920 /* Tidy up when done.  */
 921
 922 void
 923 _bfd_merge_sections_free (void *xsinfo)
 924 {
 925   struct sec_merge_info *sinfo;
 926
 927   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 928     {
 929       bfd_hash_table_free (&sinfo->htab->table);
 930       free (sinfo->htab);
 931     }
 932 }