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 <limits.h>
  28 #include "bfd.h"
  29 #include "elf-bfd.h"
  30 #include "libbfd.h"
  31 #include "hashtab.h"
  32 #include "libiberty.h"
  33
  34 struct sec_merge_sec_info;
  35
  36 /* An entry in the section merge hash table.  */
  37
  38 struct sec_merge_hash_entry
  39 {
  40   struct bfd_hash_entry root;
  41   /* Length of this entry.  This includes the zero terminator.  */
  42   unsigned int len;
  43   /* Start of this string needs to be aligned to
  44      alignment octets (not 1 << align).  */
  45   unsigned int alignment;
  46   union
  47   {
  48     /* Index within the merged section.  */
  49     bfd_size_type index;
  50     /* Entry this is a suffix of (if alignment is 0).  */
  51     struct sec_merge_hash_entry *suffix;
  52   } u;
  53   /* Which section is it in.  */
  54   struct sec_merge_sec_info *secinfo;
  55   /* Next entity in the hash table.  */
  56   struct sec_merge_hash_entry *next;
  57 };
  58
  59 /* The section merge hash table.  */
  60
  61 struct sec_merge_hash
  62 {
  63   struct bfd_hash_table table;
  64   /* Next available index.  */
  65   bfd_size_type size;
  66   /* First entity in the SEC_MERGE sections of this type.  */
  67   struct sec_merge_hash_entry *first;
  68   /* Last entity in the SEC_MERGE sections of this type.  */
  69   struct sec_merge_hash_entry *last;
  70   /* Entity size.  */
  71   unsigned int entsize;
  72   /* Are entries fixed size or zero terminated strings?  */
  73   bfd_boolean strings;
  74 };
  75
  76 struct sec_merge_info
  77 {
  78   /* Chain of sec_merge_infos.  */
  79   struct sec_merge_info *next;
  80   /* Chain of sec_merge_sec_infos.  */
  81   struct sec_merge_sec_info *chain;
  82   /* A hash table used to hold section content.  */
  83   struct sec_merge_hash *htab;
  84 };
  85
  86 struct sec_merge_sec_info
  87 {
  88   /* Chain of sec_merge_sec_infos.  */
  89   struct sec_merge_sec_info *next;
  90   /* The corresponding section.  */
  91   asection *sec;
  92   /* Pointer to merge_info pointing to us.  */
  93   void **psecinfo;
  94   /* A hash table used to hold section content.  */
  95   struct sec_merge_hash *htab;
  96   /* First string in this section.  */
  97   struct sec_merge_hash_entry *first_str;
  98   /* Original section content.  */
  99   unsigned char contents[1];
 100 };
 101
 102
 103 /* Routine to create an entry in a section merge hashtab.  */
 104
 105 static struct bfd_hash_entry *
 106 sec_merge_hash_newfunc (struct bfd_hash_entry *entry,
 107                         struct bfd_hash_table *table, const char *string)
 108 {
 109   /* Allocate the structure if it has not already been allocated by a
 110      subclass.  */
 111   if (entry == NULL)
 112     entry = (struct bfd_hash_entry *)
 113         bfd_hash_allocate (table, sizeof (struct sec_merge_hash_entry));
 114   if (entry == NULL)
 115     return NULL;
 116
 117   /* Call the allocation method of the superclass.  */
 118   entry = bfd_hash_newfunc (entry, table, string);
 119
 120   if (entry != NULL)
 121     {
 122       /* Initialize the local fields.  */
 123       struct sec_merge_hash_entry *ret = (struct sec_merge_hash_entry *) entry;
 124
 125       ret->u.suffix = NULL;
 126       ret->alignment = 0;
 127       ret->secinfo = NULL;
 128       ret->next = NULL;
 129     }
 130
 131   return entry;
 132 }
 133
 134 /* Look up an entry in a section merge hash table.  */
 135
 136 static struct sec_merge_hash_entry *
 137 sec_merge_hash_lookup (struct sec_merge_hash *table, const char *string,
 138                        unsigned int alignment, bfd_boolean create)
 139 {
 140   const unsigned char *s;
 141   unsigned long hash;
 142   unsigned int c;
 143   struct sec_merge_hash_entry *hashp;
 144   unsigned int len, i;
 145   unsigned int _index;
 146
 147   hash = 0;
 148   len = 0;
 149   s = (const unsigned char *) string;
 150   if (table->strings)
 151     {
 152       if (table->entsize == 1)
 153         {
 154           while ((c = *s++) != '\0')
 155             {
 156               hash += c + (c << 17);
 157               hash ^= hash >> 2;
 158               ++len;
 159             }
 160           hash += len + (len << 17);
 161         }
 162       else
 163         {
 164           for (;;)
 165             {
 166               for (i = 0; i < table->entsize; ++i)
 167                 if (s[i] != '\0')
 168                   break;
 169               if (i == table->entsize)
 170                 break;
 171               for (i = 0; i < table->entsize; ++i)
 172                 {
 173                   c = *s++;
 174                   hash += c + (c << 17);
 175                   hash ^= hash >> 2;
 176                 }
 177               ++len;
 178             }
 179           hash += len + (len << 17);
 180           len *= table->entsize;
 181         }
 182       hash ^= hash >> 2;
 183       len += table->entsize;
 184     }
 185   else
 186     {
 187       for (i = 0; i < table->entsize; ++i)
 188         {
 189           c = *s++;
 190           hash += c + (c << 17);
 191           hash ^= hash >> 2;
 192         }
 193       len = table->entsize;
 194     }
 195
 196   _index = hash % table->table.size;
 197   for (hashp = (struct sec_merge_hash_entry *) table->table.table[_index];
 198        hashp != NULL;
 199        hashp = (struct sec_merge_hash_entry *) hashp->root.next)
 200     {
 201       if (hashp->root.hash == hash
 202           && len == hashp->len
 203           && memcmp (hashp->root.string, string, len) == 0)
 204         {
 205           /* If the string we found does not have at least the required
 206              alignment, we need to insert another copy.  */
 207           if (hashp->alignment < alignment)
 208             {
 209               if (create)
 210                 {
 211                   /*  Mark the less aligned copy as deleted.  */
 212                   hashp->len = 0;
 213                   hashp->alignment = 0;
 214                 }
 215               break;
 216             }
 217           return hashp;
 218         }
 219     }
 220
 221   if (! create)
 222     return NULL;
 223
 224   hashp = ((struct sec_merge_hash_entry *)
 225            bfd_hash_insert (&table->table, string, hash));
 226   if (hashp == NULL)
 227     return NULL;
 228   hashp->len = len;
 229   hashp->alignment = alignment;
 230   return hashp;
 231 }
 232
 233 /* Create a new hash table.  */
 234
 235 static struct sec_merge_hash *
 236 sec_merge_init (unsigned int entsize, bfd_boolean strings)
 237 {
 238   struct sec_merge_hash *table;
 239
 240   table = (struct sec_merge_hash *) bfd_malloc (sizeof (struct sec_merge_hash));
 241   if (table == NULL)
 242     return NULL;
 243
 244   if (! bfd_hash_table_init_n (&table->table, sec_merge_hash_newfunc,
 245                                sizeof (struct sec_merge_hash_entry), 16699))
 246     {
 247       free (table);
 248       return NULL;
 249     }
 250
 251   table->size = 0;
 252   table->first = NULL;
 253   table->last = NULL;
 254   table->entsize = entsize;
 255   table->strings = strings;
 256
 257   return table;
 258 }
 259
 260 /* Get the index of an entity in a hash table, adding it if it is not
 261    already present.  */
 262
 263 static struct sec_merge_hash_entry *
 264 sec_merge_add (struct sec_merge_hash *tab, const char *str,
 265                unsigned int alignment, struct sec_merge_sec_info *secinfo)
 266 {
 267   struct sec_merge_hash_entry *entry;
 268
 269   entry = sec_merge_hash_lookup (tab, str, alignment, TRUE);
 270   if (entry == NULL)
 271     return NULL;
 272
 273   if (entry->secinfo == NULL)
 274     {
 275       tab->size++;
 276       entry->secinfo = secinfo;
 277       if (tab->first == NULL)
 278         tab->first = entry;
 279       else
 280         tab->last->next = entry;
 281       tab->last = entry;
 282     }
 283
 284   return entry;
 285 }
 286
 287 static bfd_boolean
 288 sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry,
 289                 unsigned char *contents, file_ptr offset)
 290 {
 291   struct sec_merge_sec_info *secinfo = entry->secinfo;
 292   asection *sec = secinfo->sec;
 293   char *pad = NULL;
 294   bfd_size_type off = 0;
 295   int alignment_power = sec->output_section->alignment_power;
 296   bfd_size_type pad_len;
 297
 298   /* FIXME: If alignment_power is 0 then really we should scan the
 299      entry list for the largest required alignment and use that.  */
 300   pad_len = alignment_power ? ((bfd_size_type) 1 << alignment_power) : 16;
 301
 302   pad = (char *) bfd_zmalloc (pad_len);
 303   if (pad == NULL)
 304     return FALSE;
 305
 306   for (; entry != NULL && entry->secinfo == secinfo; entry = entry->next)
 307     {
 308       const char *str;
 309       bfd_size_type len;
 310
 311       len = -off & (entry->alignment - 1);
 312       if (len != 0)
 313         {
 314           BFD_ASSERT (len <= pad_len);
 315           if (contents)
 316             {
 317               memcpy (contents + offset, pad, len);
 318               offset += len;
 319             }
 320           else if (bfd_bwrite (pad, len, abfd) != len)
 321             goto err;
 322           off += len;
 323         }
 324
 325       str = entry->root.string;
 326       len = entry->len;
 327
 328       if (contents)
 329         {
 330           memcpy (contents + offset, str, len);
 331           offset += len;
 332         }
 333       else if (bfd_bwrite (str, len, abfd) != len)
 334         goto err;
 335
 336       off += len;
 337     }
 338
 339   /* Trailing alignment needed?  */
 340   off = sec->size - off;
 341   if (off != 0)
 342     {
 343       BFD_ASSERT (off <= pad_len);
 344       if (contents)
 345         memcpy (contents + offset, pad, off);
 346       else if (bfd_bwrite (pad, off, abfd) != off)
 347         goto err;
 348     }
 349
 350   free (pad);
 351   return TRUE;
 352
 353  err:
 354   free (pad);
 355   return FALSE;
 356 }
 357
 358 /* Register a SEC_MERGE section as a candidate for merging.
 359    This function is called for all non-dynamic SEC_MERGE input sections.  */
 360
 361 bfd_boolean
 362 _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
 363                         void **psecinfo)
 364 {
 365   struct sec_merge_info *sinfo;
 366   struct sec_merge_sec_info *secinfo;
 367   unsigned int align;
 368   bfd_size_type amt;
 369   bfd_byte *contents;
 370
 371   if ((abfd->flags & DYNAMIC) != 0
 372       || (sec->flags & SEC_MERGE) == 0)
 373     abort ();
 374
 375   if (sec->size == 0
 376       || (sec->flags & SEC_EXCLUDE) != 0
 377       || sec->entsize == 0)
 378     return TRUE;
 379
 380   if (sec->size % sec->entsize != 0)
 381     return TRUE;
 382
 383   if ((sec->flags & SEC_RELOC) != 0)
 384     {
 385       /* We aren't prepared to handle relocations in merged sections.  */
 386       return TRUE;
 387     }
 388
 389 #ifndef CHAR_BIT
 390 #define CHAR_BIT 8
 391 #endif
 392   if (sec->alignment_power >= sizeof (align) * CHAR_BIT)
 393     return TRUE;
 394
 395   align = 1u << sec->alignment_power;
 396   if ((sec->entsize < align
 397        && ((sec->entsize & (sec->entsize - 1))
 398            || !(sec->flags & SEC_STRINGS)))
 399       || (sec->entsize > align
 400           && (sec->entsize & (align - 1))))
 401     {
 402       /* Sanity check.  If string character size is smaller than
 403          alignment, then we require character size to be a power
 404          of 2, otherwise character size must be integer multiple
 405          of alignment.  For non-string constants, alignment must
 406          be smaller than or equal to entity size and entity size
 407          must be integer multiple of alignment.  */
 408       return TRUE;
 409     }
 410
 411   for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
 412     if ((secinfo = sinfo->chain)
 413         && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
 414         && secinfo->sec->entsize == sec->entsize
 415         && secinfo->sec->alignment_power == sec->alignment_power
 416         && secinfo->sec->output_section == sec->output_section)
 417       break;
 418
 419   if (sinfo == NULL)
 420     {
 421       /* Initialize the information we need to keep track of.  */
 422       sinfo = (struct sec_merge_info *)
 423           bfd_alloc (abfd, sizeof (struct sec_merge_info));
 424       if (sinfo == NULL)
 425         goto error_return;
 426       sinfo->next = (struct sec_merge_info *) *psinfo;
 427       sinfo->chain = NULL;
 428       *psinfo = sinfo;
 429       sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
 430       if (sinfo->htab == NULL)
 431         goto error_return;
 432     }
 433
 434   /* Read the section from abfd.  */
 435
 436   amt = sizeof (struct sec_merge_sec_info) - 1 + sec->size;
 437   if (sec->flags & SEC_STRINGS)
 438     /* Some versions of gcc may emit a string without a zero terminator.
 439        See http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01004.html
 440        Allocate space for an extra zero.  */
 441     amt += sec->entsize;
 442   *psecinfo = bfd_alloc (abfd, amt);
 443   if (*psecinfo == NULL)
 444     goto error_return;
 445
 446   secinfo = (struct sec_merge_sec_info *) *psecinfo;
 447   if (sinfo->chain)
 448     {
 449       secinfo->next = sinfo->chain->next;
 450       sinfo->chain->next = secinfo;
 451     }
 452   else
 453     secinfo->next = secinfo;
 454   sinfo->chain = secinfo;
 455   secinfo->sec = sec;
 456   secinfo->psecinfo = psecinfo;
 457   secinfo->htab = sinfo->htab;
 458   secinfo->first_str = NULL;
 459
 460   sec->rawsize = sec->size;
 461   if (sec->flags & SEC_STRINGS)
 462     memset (secinfo->contents + sec->size, 0, sec->entsize);
 463   contents = secinfo->contents;
 464   if (! bfd_get_full_section_contents (sec->owner, sec, &contents))
 465     goto error_return;
 466
 467   return TRUE;
 468
 469  error_return:
 470   *psecinfo = NULL;
 471   return FALSE;
 472 }
 473
 474 /* Record one section into the hash table.  */
 475 static bfd_boolean
 476 record_section (struct sec_merge_info *sinfo,
 477                 struct sec_merge_sec_info *secinfo)
 478 {
 479   asection *sec = secinfo->sec;
 480   struct sec_merge_hash_entry *entry;
 481   bfd_boolean nul;
 482   unsigned char *p, *end;
 483   bfd_vma mask, eltalign;
 484   unsigned int align, i;
 485
 486   align = sec->alignment_power;
 487   end = secinfo->contents + sec->size;
 488   nul = FALSE;
 489   mask = ((bfd_vma) 1 << align) - 1;
 490   if (sec->flags & SEC_STRINGS)
 491     {
 492       for (p = secinfo->contents; p < end; )
 493         {
 494           eltalign = p - secinfo->contents;
 495           eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
 496           if (!eltalign || eltalign > mask)
 497             eltalign = mask + 1;
 498           entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
 499                                  secinfo);
 500           if (! entry)
 501             goto error_return;
 502           p += entry->len;
 503           if (sec->entsize == 1)
 504             {
 505               while (p < end && *p == 0)
 506                 {
 507                   if (!nul && !((p - secinfo->contents) & mask))
 508                     {
 509                       nul = TRUE;
 510                       entry = sec_merge_add (sinfo->htab, "",
 511                                              (unsigned) mask + 1, secinfo);
 512                       if (! entry)
 513                         goto error_return;
 514                     }
 515                   p++;
 516                 }
 517             }
 518           else
 519             {
 520               while (p < end)
 521                 {
 522                   for (i = 0; i < sec->entsize; i++)
 523                     if (p[i] != '\0')
 524                       break;
 525                   if (i != sec->entsize)
 526                     break;
 527                   if (!nul && !((p - secinfo->contents) & mask))
 528                     {
 529                       nul = TRUE;
 530                       entry = sec_merge_add (sinfo->htab, (char *) p,
 531                                              (unsigned) mask + 1, secinfo);
 532                       if (! entry)
 533                         goto error_return;
 534                     }
 535                   p += sec->entsize;
 536                 }
 537             }
 538         }
 539     }
 540   else
 541     {
 542       for (p = secinfo->contents; p < end; p += sec->entsize)
 543         {
 544           entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
 545           if (! entry)
 546             goto error_return;
 547         }
 548     }
 549
 550   return TRUE;
 551
 552 error_return:
 553   for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 554     *secinfo->psecinfo = NULL;
 555   return FALSE;
 556 }
 557
 558 static int
 559 strrevcmp (const void *a, const void *b)
 560 {
 561   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 562   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 563   unsigned int lenA = A->len;
 564   unsigned int lenB = B->len;
 565   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 566   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 567   int l = lenA < lenB ? lenA : lenB;
 568
 569   while (l)
 570     {
 571       if (*s != *t)
 572         return (int) *s - (int) *t;
 573       s--;
 574       t--;
 575       l--;
 576     }
 577   return lenA - lenB;
 578 }
 579
 580 /* Like strrevcmp, but for the case where all strings have the same
 581    alignment > entsize.  */
 582
 583 static int
 584 strrevcmp_align (const void *a, const void *b)
 585 {
 586   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 587   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 588   unsigned int lenA = A->len;
 589   unsigned int lenB = B->len;
 590   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 591   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 592   int l = lenA < lenB ? lenA : lenB;
 593   int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
 594
 595   if (tail_align != 0)
 596     return tail_align;
 597
 598   while (l)
 599     {
 600       if (*s != *t)
 601         return (int) *s - (int) *t;
 602       s--;
 603       t--;
 604       l--;
 605     }
 606   return lenA - lenB;
 607 }
 608
 609 static inline int
 610 is_suffix (const struct sec_merge_hash_entry *A,
 611            const struct sec_merge_hash_entry *B)
 612 {
 613   if (A->len <= B->len)
 614     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 615        not to be equal by the hash table.  */
 616     return 0;
 617
 618   return memcmp (A->root.string + (A->len - B->len),
 619                  B->root.string, B->len) == 0;
 620 }
 621
 622 /* This is a helper function for _bfd_merge_sections.  It attempts to
 623    merge strings matching suffixes of longer strings.  */
 624 static bfd_boolean
 625 merge_strings (struct sec_merge_info *sinfo)
 626 {
 627   struct sec_merge_hash_entry **array, **a, *e;
 628   struct sec_merge_sec_info *secinfo;
 629   bfd_size_type size, amt;
 630   unsigned int alignment = 0;
 631
 632   /* Now sort the strings */
 633   amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
 634   array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
 635   if (array == NULL)
 636     return FALSE;
 637
 638   for (e = sinfo->htab->first, a = array; e; e = e->next)
 639     if (e->alignment)
 640       {
 641         *a++ = e;
 642         /* Adjust the length to not include the zero terminator.  */
 643         e->len -= sinfo->htab->entsize;
 644         if (alignment != e->alignment)
 645           {
 646             if (alignment == 0)
 647               alignment = e->alignment;
 648             else
 649               alignment = (unsigned) -1;
 650           }
 651       }
 652
 653   sinfo->htab->size = a - array;
 654   if (sinfo->htab->size != 0)
 655     {
 656       qsort (array, (size_t) sinfo->htab->size,
 657              sizeof (struct sec_merge_hash_entry *),
 658              (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
 659               ? strrevcmp_align : strrevcmp));
 660
 661       /* Loop over the sorted array and merge suffixes */
 662       e = *--a;
 663       e->len += sinfo->htab->entsize;
 664       while (--a >= array)
 665         {
 666           struct sec_merge_hash_entry *cmp = *a;
 667
 668           cmp->len += sinfo->htab->entsize;
 669           if (e->alignment >= cmp->alignment
 670               && !((e->len - cmp->len) & (cmp->alignment - 1))
 671               && is_suffix (e, cmp))
 672             {
 673               cmp->u.suffix = e;
 674               cmp->alignment = 0;
 675             }
 676           else
 677             e = cmp;
 678         }
 679     }
 680
 681   free (array);
 682
 683   /* Now assign positions to the strings we want to keep.  */
 684   size = 0;
 685   secinfo = sinfo->htab->first->secinfo;
 686   for (e = sinfo->htab->first; e; e = e->next)
 687     {
 688       if (e->secinfo != secinfo)
 689         {
 690           secinfo->sec->size = size;
 691           secinfo = e->secinfo;
 692         }
 693       if (e->alignment)
 694         {
 695           if (e->secinfo->first_str == NULL)
 696             {
 697               e->secinfo->first_str = e;
 698               size = 0;
 699             }
 700           size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 701           e->u.index = size;
 702           size += e->len;
 703         }
 704     }
 705   secinfo->sec->size = size;
 706   if (secinfo->sec->alignment_power != 0)
 707     {
 708       bfd_size_type align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
 709       secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
 710     }
 711
 712   /* And now adjust the rest, removing them from the chain (but not hashtable)
 713      at the same time.  */
 714   for (a = &sinfo->htab->first, e = *a; e; e = e->next)
 715     if (e->alignment)
 716       a = &e->next;
 717     else
 718       {
 719         *a = e->next;
 720         if (e->len)
 721           {
 722             e->secinfo = e->u.suffix->secinfo;
 723             e->alignment = e->u.suffix->alignment;
 724             e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
 725           }
 726       }
 727   return TRUE;
 728 }
 729
 730 /* This function is called once after all SEC_MERGE sections are registered
 731    with _bfd_merge_section.  */
 732
 733 bfd_boolean
 734 _bfd_merge_sections (bfd *abfd,
 735                      struct bfd_link_info *info ATTRIBUTE_UNUSED,
 736                      void *xsinfo,
 737                      void (*remove_hook) (bfd *, asection *))
 738 {
 739   struct sec_merge_info *sinfo;
 740
 741   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 742     {
 743       struct sec_merge_sec_info * secinfo;
 744
 745       if (! sinfo->chain)
 746         continue;
 747
 748       /* Move sinfo->chain to head of the chain, terminate it.  */
 749       secinfo = sinfo->chain;
 750       sinfo->chain = secinfo->next;
 751       secinfo->next = NULL;
 752
 753       /* Record the sections into the hash table.  */
 754       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 755         if (secinfo->sec->flags & SEC_EXCLUDE)
 756           {
 757             *secinfo->psecinfo = NULL;
 758             if (remove_hook)
 759               (*remove_hook) (abfd, secinfo->sec);
 760           }
 761         else if (! record_section (sinfo, secinfo))
 762           return FALSE;
 763
 764       if (secinfo)
 765         continue;
 766
 767       if (sinfo->htab->first == NULL)
 768         continue;
 769
 770       if (sinfo->htab->strings)
 771         {
 772           if (!merge_strings (sinfo))
 773             return FALSE;
 774         }
 775       else
 776         {
 777           struct sec_merge_hash_entry *e;
 778           bfd_size_type size = 0;
 779
 780           /* Things are much simpler for non-strings.
 781              Just assign them slots in the section.  */
 782           secinfo = NULL;
 783           for (e = sinfo->htab->first; e; e = e->next)
 784             {
 785               if (e->secinfo->first_str == NULL)
 786                 {
 787                   if (secinfo)
 788                     secinfo->sec->size = size;
 789                   e->secinfo->first_str = e;
 790                   size = 0;
 791                 }
 792               size = (size + e->alignment - 1)
 793                      & ~((bfd_vma) e->alignment - 1);
 794               e->u.index = size;
 795               size += e->len;
 796               secinfo = e->secinfo;
 797             }
 798           secinfo->sec->size = size;
 799         }
 800
 801         /* Finally remove all input sections which have not made it into
 802            the hash table at all.  */
 803         for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 804           if (secinfo->first_str == NULL)
 805             secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
 806     }
 807
 808   return TRUE;
 809 }
 810
 811 /* Write out the merged section.  */
 812
 813 bfd_boolean
 814 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
 815 {
 816   struct sec_merge_sec_info *secinfo;
 817   file_ptr pos;
 818   unsigned char *contents;
 819   Elf_Internal_Shdr *hdr;
 820
 821   secinfo = (struct sec_merge_sec_info *) psecinfo;
 822
 823   if (!secinfo)
 824     return FALSE;
 825
 826   if (secinfo->first_str == NULL)
 827     return TRUE;
 828
 829   /* FIXME: octets_per_byte.  */
 830   hdr = &elf_section_data (sec->output_section)->this_hdr;
 831   if (hdr->sh_offset == (file_ptr) -1)
 832     {
 833       /* We must compress this section.  Write output to the
 834          buffer.  */
 835       contents = hdr->contents;
 836       if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
 837           || contents == NULL)
 838         abort ();
 839     }
 840   else
 841     {
 842       contents = NULL;
 843       pos = sec->output_section->filepos + sec->output_offset;
 844       if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
 845         return FALSE;
 846     }
 847
 848   if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
 849                         sec->output_offset))
 850     return FALSE;
 851
 852   return TRUE;
 853 }
 854
 855 /* Adjust an address in the SEC_MERGE section.  Given OFFSET within
 856    *PSEC, this returns the new offset in the adjusted SEC_MERGE
 857    section and writes the new section back into *PSEC.  */
 858
 859 bfd_vma
 860 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
 861                             void *psecinfo, bfd_vma offset)
 862 {
 863   struct sec_merge_sec_info *secinfo;
 864   struct sec_merge_hash_entry *entry;
 865   unsigned char *p;
 866   asection *sec = *psec;
 867
 868   secinfo = (struct sec_merge_sec_info *) psecinfo;
 869
 870   if (!secinfo)
 871     return offset;
 872
 873   if (offset >= sec->rawsize)
 874     {
 875       if (offset > sec->rawsize)
 876         _bfd_error_handler
 877           /* xgettext:c-format */
 878           (_("%pB: access beyond end of merged section (%" PRId64 ")"),
 879            sec->owner, (int64_t) offset);
 880       return secinfo->first_str ? sec->size : 0;
 881     }
 882
 883   if (secinfo->htab->strings)
 884     {
 885       if (sec->entsize == 1)
 886         {
 887           p = secinfo->contents + offset - 1;
 888           while (p >= secinfo->contents && *p)
 889             --p;
 890           ++p;
 891         }
 892       else
 893         {
 894           p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 895           p -= sec->entsize;
 896           while (p >= secinfo->contents)
 897             {
 898               unsigned int i;
 899
 900               for (i = 0; i < sec->entsize; ++i)
 901                 if (p[i] != '\0')
 902                   break;
 903               if (i == sec->entsize)
 904                 break;
 905               p -= sec->entsize;
 906             }
 907           p += sec->entsize;
 908         }
 909     }
 910   else
 911     {
 912       p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 913     }
 914   entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
 915   if (!entry)
 916     {
 917       if (! secinfo->htab->strings)
 918         abort ();
 919       /* This should only happen if somebody points into the padding
 920          after a NUL character but before next entity.  */
 921       if (*p)
 922         abort ();
 923       if (! secinfo->htab->first)
 924         abort ();
 925       entry = secinfo->htab->first;
 926       p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
 927            - entry->len);
 928     }
 929
 930   *psec = entry->secinfo->sec;
 931   return entry->u.index + (secinfo->contents + offset - p);
 932 }
 933
 934 /* Tidy up when done.  */
 935
 936 void
 937 _bfd_merge_sections_free (void *xsinfo)
 938 {
 939   struct sec_merge_info *sinfo;
 940
 941   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 942     {
 943       bfd_hash_table_free (&sinfo->htab->table);
 944       free (sinfo->htab);
 945     }
 946 }