bfd/merge.c

   1 /* SEC_MERGE support.
   2    Copyright (C) 2001-2020 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 /* qsort comparison function.  Won't ever return zero as all entries
 559    differ, so there is no issue with qsort stability here.  */
 560
 561 static int
 562 strrevcmp (const void *a, const void *b)
 563 {
 564   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 565   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 566   unsigned int lenA = A->len;
 567   unsigned int lenB = B->len;
 568   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 569   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 570   int l = lenA < lenB ? lenA : lenB;
 571
 572   while (l)
 573     {
 574       if (*s != *t)
 575         return (int) *s - (int) *t;
 576       s--;
 577       t--;
 578       l--;
 579     }
 580   return lenA - lenB;
 581 }
 582
 583 /* Like strrevcmp, but for the case where all strings have the same
 584    alignment > entsize.  */
 585
 586 static int
 587 strrevcmp_align (const void *a, const void *b)
 588 {
 589   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 590   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 591   unsigned int lenA = A->len;
 592   unsigned int lenB = B->len;
 593   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 594   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 595   int l = lenA < lenB ? lenA : lenB;
 596   int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
 597
 598   if (tail_align != 0)
 599     return tail_align;
 600
 601   while (l)
 602     {
 603       if (*s != *t)
 604         return (int) *s - (int) *t;
 605       s--;
 606       t--;
 607       l--;
 608     }
 609   return lenA - lenB;
 610 }
 611
 612 static inline int
 613 is_suffix (const struct sec_merge_hash_entry *A,
 614            const struct sec_merge_hash_entry *B)
 615 {
 616   if (A->len <= B->len)
 617     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 618        not to be equal by the hash table.  */
 619     return 0;
 620
 621   return memcmp (A->root.string + (A->len - B->len),
 622                  B->root.string, B->len) == 0;
 623 }
 624
 625 /* This is a helper function for _bfd_merge_sections.  It attempts to
 626    merge strings matching suffixes of longer strings.  */
 627 static struct sec_merge_sec_info *
 628 merge_strings (struct sec_merge_info *sinfo)
 629 {
 630   struct sec_merge_hash_entry **array, **a, *e;
 631   struct sec_merge_sec_info *secinfo;
 632   bfd_size_type size, amt;
 633   unsigned int alignment = 0;
 634
 635   /* Now sort the strings */
 636   amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
 637   array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
 638   if (array == NULL)
 639     return NULL;
 640
 641   for (e = sinfo->htab->first, a = array; e; e = e->next)
 642     if (e->alignment)
 643       {
 644         *a++ = e;
 645         /* Adjust the length to not include the zero terminator.  */
 646         e->len -= sinfo->htab->entsize;
 647         if (alignment != e->alignment)
 648           {
 649             if (alignment == 0)
 650               alignment = e->alignment;
 651             else
 652               alignment = (unsigned) -1;
 653           }
 654       }
 655
 656   sinfo->htab->size = a - array;
 657   if (sinfo->htab->size != 0)
 658     {
 659       qsort (array, (size_t) sinfo->htab->size,
 660              sizeof (struct sec_merge_hash_entry *),
 661              (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
 662               ? strrevcmp_align : strrevcmp));
 663
 664       /* Loop over the sorted array and merge suffixes */
 665       e = *--a;
 666       e->len += sinfo->htab->entsize;
 667       while (--a >= array)
 668         {
 669           struct sec_merge_hash_entry *cmp = *a;
 670
 671           cmp->len += sinfo->htab->entsize;
 672           if (e->alignment >= cmp->alignment
 673               && !((e->len - cmp->len) & (cmp->alignment - 1))
 674               && is_suffix (e, cmp))
 675             {
 676               cmp->u.suffix = e;
 677               cmp->alignment = 0;
 678             }
 679           else
 680             e = cmp;
 681         }
 682     }
 683
 684   free (array);
 685
 686   /* Now assign positions to the strings we want to keep.  */
 687   size = 0;
 688   secinfo = sinfo->htab->first->secinfo;
 689   for (e = sinfo->htab->first; e; e = e->next)
 690     {
 691       if (e->secinfo != secinfo)
 692         {
 693           secinfo->sec->size = size;
 694           secinfo = e->secinfo;
 695         }
 696       if (e->alignment)
 697         {
 698           if (e->secinfo->first_str == NULL)
 699             {
 700               e->secinfo->first_str = e;
 701               size = 0;
 702             }
 703           size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 704           e->u.index = size;
 705           size += e->len;
 706         }
 707     }
 708   secinfo->sec->size = size;
 709
 710   /* And now adjust the rest, removing them from the chain (but not hashtable)
 711      at the same time.  */
 712   for (a = &sinfo->htab->first, e = *a; e; e = e->next)
 713     if (e->alignment)
 714       a = &e->next;
 715     else
 716       {
 717         *a = e->next;
 718         if (e->len)
 719           {
 720             e->secinfo = e->u.suffix->secinfo;
 721             e->alignment = e->u.suffix->alignment;
 722             e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
 723           }
 724       }
 725   return secinfo;
 726 }
 727
 728 /* This function is called once after all SEC_MERGE sections are registered
 729    with _bfd_merge_section.  */
 730
 731 bfd_boolean
 732 _bfd_merge_sections (bfd *abfd,
 733                      struct bfd_link_info *info ATTRIBUTE_UNUSED,
 734                      void *xsinfo,
 735                      void (*remove_hook) (bfd *, asection *))
 736 {
 737   struct sec_merge_info *sinfo;
 738
 739   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 740     {
 741       struct sec_merge_sec_info *secinfo;
 742       bfd_size_type align;
 743
 744       if (! sinfo->chain)
 745         continue;
 746
 747       /* Move sinfo->chain to head of the chain, terminate it.  */
 748       secinfo = sinfo->chain;
 749       sinfo->chain = secinfo->next;
 750       secinfo->next = NULL;
 751
 752       /* Record the sections into the hash table.  */
 753       align = 1;
 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
 762           {
 763             if (!record_section (sinfo, secinfo))
 764               return FALSE;
 765             if (align)
 766               {
 767                 align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
 768                 if ((secinfo->sec->size & (align - 1)) != 0)
 769                   align = 0;
 770               }
 771           }
 772
 773       if (sinfo->htab->first == NULL)
 774         continue;
 775
 776       if (sinfo->htab->strings)
 777         {
 778           secinfo = merge_strings (sinfo);
 779           if (!secinfo)
 780             return FALSE;
 781         }
 782       else
 783         {
 784           struct sec_merge_hash_entry *e;
 785           bfd_size_type size = 0;
 786
 787           /* Things are much simpler for non-strings.
 788              Just assign them slots in the section.  */
 789           secinfo = NULL;
 790           for (e = sinfo->htab->first; e; e = e->next)
 791             {
 792               if (e->secinfo->first_str == NULL)
 793                 {
 794                   if (secinfo)
 795                     secinfo->sec->size = size;
 796                   e->secinfo->first_str = e;
 797                   size = 0;
 798                 }
 799               size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 800               e->u.index = size;
 801               size += e->len;
 802               secinfo = e->secinfo;
 803             }
 804           secinfo->sec->size = size;
 805         }
 806
 807       /* If the input sections were padded according to their alignments,
 808          then pad the output too.  */
 809       if (align)
 810         secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
 811
 812       /* Finally remove all input sections which have not made it into
 813          the hash table at all.  */
 814       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 815         if (secinfo->first_str == NULL)
 816           secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
 817     }
 818
 819   return TRUE;
 820 }
 821
 822 /* Write out the merged section.  */
 823
 824 bfd_boolean
 825 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
 826 {
 827   struct sec_merge_sec_info *secinfo;
 828   file_ptr pos;
 829   unsigned char *contents;
 830   Elf_Internal_Shdr *hdr;
 831
 832   secinfo = (struct sec_merge_sec_info *) psecinfo;
 833
 834   if (!secinfo)
 835     return FALSE;
 836
 837   if (secinfo->first_str == NULL)
 838     return TRUE;
 839
 840   /* FIXME: octets_per_byte.  */
 841   hdr = &elf_section_data (sec->output_section)->this_hdr;
 842   if (hdr->sh_offset == (file_ptr) -1)
 843     {
 844       /* We must compress this section.  Write output to the
 845          buffer.  */
 846       contents = hdr->contents;
 847       if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
 848           || contents == NULL)
 849         abort ();
 850     }
 851   else
 852     {
 853       contents = NULL;
 854       pos = sec->output_section->filepos + sec->output_offset;
 855       if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
 856         return FALSE;
 857     }
 858
 859   if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
 860                         sec->output_offset))
 861     return FALSE;
 862
 863   return TRUE;
 864 }
 865
 866 /* Adjust an address in the SEC_MERGE section.  Given OFFSET within
 867    *PSEC, this returns the new offset in the adjusted SEC_MERGE
 868    section and writes the new section back into *PSEC.  */
 869
 870 bfd_vma
 871 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
 872                             void *psecinfo, bfd_vma offset)
 873 {
 874   struct sec_merge_sec_info *secinfo;
 875   struct sec_merge_hash_entry *entry;
 876   unsigned char *p;
 877   asection *sec = *psec;
 878
 879   secinfo = (struct sec_merge_sec_info *) psecinfo;
 880
 881   if (!secinfo)
 882     return offset;
 883
 884   if (offset >= sec->rawsize)
 885     {
 886       if (offset > sec->rawsize)
 887         _bfd_error_handler
 888           /* xgettext:c-format */
 889           (_("%pB: access beyond end of merged section (%" PRId64 ")"),
 890            sec->owner, (int64_t) offset);
 891       return secinfo->first_str ? sec->size : 0;
 892     }
 893
 894   if (secinfo->htab->strings)
 895     {
 896       if (sec->entsize == 1)
 897         {
 898           p = secinfo->contents + offset - 1;
 899           while (p >= secinfo->contents && *p)
 900             --p;
 901           ++p;
 902         }
 903       else
 904         {
 905           p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 906           p -= sec->entsize;
 907           while (p >= secinfo->contents)
 908             {
 909               unsigned int i;
 910
 911               for (i = 0; i < sec->entsize; ++i)
 912                 if (p[i] != '\0')
 913                   break;
 914               if (i == sec->entsize)
 915                 break;
 916               p -= sec->entsize;
 917             }
 918           p += sec->entsize;
 919         }
 920     }
 921   else
 922     {
 923       p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 924     }
 925   entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, FALSE);
 926   if (!entry)
 927     {
 928       if (! secinfo->htab->strings)
 929         abort ();
 930       /* This should only happen if somebody points into the padding
 931          after a NUL character but before next entity.  */
 932       if (*p)
 933         abort ();
 934       if (! secinfo->htab->first)
 935         abort ();
 936       entry = secinfo->htab->first;
 937       p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
 938            - entry->len);
 939     }
 940
 941   *psec = entry->secinfo->sec;
 942   return entry->u.index + (secinfo->contents + offset - p);
 943 }
 944
 945 /* Tidy up when done.  */
 946
 947 void
 948 _bfd_merge_sections_free (void *xsinfo)
 949 {
 950   struct sec_merge_info *sinfo;
 951
 952   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 953     {
 954       bfd_hash_table_free (&sinfo->htab->table);
 955       free (sinfo->htab);
 956     }
 957 }