bfd/merge.c

   1 /* SEC_MERGE support.
   2    Copyright (C) 2001-2022 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   bool 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, bool 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, bool 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 bool
 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   unsigned int opb = bfd_octets_per_byte (abfd, sec);
 296   int alignment_power = sec->output_section->alignment_power * opb;
 297   bfd_size_type pad_len;  /* Octets.  */
 298
 299   /* FIXME: If alignment_power is 0 then really we should scan the
 300      entry list for the largest required alignment and use that.  */
 301   pad_len = alignment_power ? ((bfd_size_type) 1 << alignment_power) : 16;
 302
 303   pad = (char *) bfd_zmalloc (pad_len);
 304   if (pad == NULL)
 305     return false;
 306
 307   for (; entry != NULL && entry->secinfo == secinfo; entry = entry->next)
 308     {
 309       const char *str;
 310       bfd_size_type len;
 311
 312       len = -off & (entry->alignment - 1);
 313       if (len != 0)
 314         {
 315           BFD_ASSERT (len <= pad_len);
 316           if (contents)
 317             {
 318               memcpy (contents + offset, pad, len);
 319               offset += len;
 320             }
 321           else if (bfd_bwrite (pad, len, abfd) != len)
 322             goto err;
 323           off += len;
 324         }
 325
 326       str = entry->root.string;
 327       len = entry->len;
 328
 329       if (contents)
 330         {
 331           memcpy (contents + offset, str, len);
 332           offset += len;
 333         }
 334       else if (bfd_bwrite (str, len, abfd) != len)
 335         goto err;
 336
 337       off += len;
 338     }
 339
 340   /* Trailing alignment needed?  */
 341   off = sec->size - off;
 342   if (off != 0)
 343     {
 344       BFD_ASSERT (off <= pad_len);
 345       if (contents)
 346         memcpy (contents + offset, pad, off);
 347       else if (bfd_bwrite (pad, off, abfd) != off)
 348         goto err;
 349     }
 350
 351   free (pad);
 352   return true;
 353
 354  err:
 355   free (pad);
 356   return false;
 357 }
 358
 359 /* Register a SEC_MERGE section as a candidate for merging.
 360    This function is called for all non-dynamic SEC_MERGE input sections.  */
 361
 362 bool
 363 _bfd_add_merge_section (bfd *abfd, void **psinfo, asection *sec,
 364                         void **psecinfo)
 365 {
 366   struct sec_merge_info *sinfo;
 367   struct sec_merge_sec_info *secinfo;
 368   unsigned int alignment_power;  /* Octets.  */
 369   unsigned int align;            /* Octets.  */
 370   bfd_size_type amt;
 371   bfd_byte *contents;
 372   unsigned int opb = bfd_octets_per_byte (abfd, sec);
 373
 374   if ((abfd->flags & DYNAMIC) != 0
 375       || (sec->flags & SEC_MERGE) == 0)
 376     abort ();
 377
 378   if (sec->size == 0
 379       || (sec->flags & SEC_EXCLUDE) != 0
 380       || sec->entsize == 0)
 381     return true;
 382
 383   if (sec->size % sec->entsize != 0)
 384     return true;
 385
 386   if ((sec->flags & SEC_RELOC) != 0)
 387     {
 388       /* We aren't prepared to handle relocations in merged sections.  */
 389       return true;
 390     }
 391
 392 #ifndef CHAR_BIT
 393 #define CHAR_BIT 8
 394 #endif
 395   alignment_power = sec->alignment_power * opb;
 396   if (alignment_power >= sizeof (align) * CHAR_BIT)
 397     return true;
 398
 399   align = 1u << alignment_power;
 400   if ((sec->entsize < align
 401        && ((sec->entsize & (sec->entsize - 1))
 402            || !(sec->flags & SEC_STRINGS)))
 403       || (sec->entsize > align
 404           && (sec->entsize & (align - 1))))
 405     {
 406       /* Sanity check.  If string character size is smaller than
 407          alignment, then we require character size to be a power
 408          of 2, otherwise character size must be integer multiple
 409          of alignment.  For non-string constants, alignment must
 410          be smaller than or equal to entity size and entity size
 411          must be integer multiple of alignment.  */
 412       return true;
 413     }
 414
 415   for (sinfo = (struct sec_merge_info *) *psinfo; sinfo; sinfo = sinfo->next)
 416     if ((secinfo = sinfo->chain)
 417         && ! ((secinfo->sec->flags ^ sec->flags) & (SEC_MERGE | SEC_STRINGS))
 418         && secinfo->sec->entsize == sec->entsize
 419         && secinfo->sec->alignment_power == sec->alignment_power
 420         && secinfo->sec->output_section == sec->output_section)
 421       break;
 422
 423   if (sinfo == NULL)
 424     {
 425       /* Initialize the information we need to keep track of.  */
 426       sinfo = (struct sec_merge_info *)
 427           bfd_alloc (abfd, sizeof (struct sec_merge_info));
 428       if (sinfo == NULL)
 429         goto error_return;
 430       sinfo->next = (struct sec_merge_info *) *psinfo;
 431       sinfo->chain = NULL;
 432       *psinfo = sinfo;
 433       sinfo->htab = sec_merge_init (sec->entsize, (sec->flags & SEC_STRINGS));
 434       if (sinfo->htab == NULL)
 435         goto error_return;
 436     }
 437
 438   /* Read the section from abfd.  */
 439
 440   amt = sizeof (struct sec_merge_sec_info) - 1 + sec->size;
 441   if (sec->flags & SEC_STRINGS)
 442     /* Some versions of gcc may emit a string without a zero terminator.
 443        See http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01004.html
 444        Allocate space for an extra zero.  */
 445     amt += sec->entsize;
 446   *psecinfo = bfd_alloc (abfd, amt);
 447   if (*psecinfo == NULL)
 448     goto error_return;
 449
 450   secinfo = (struct sec_merge_sec_info *) *psecinfo;
 451   if (sinfo->chain)
 452     {
 453       secinfo->next = sinfo->chain->next;
 454       sinfo->chain->next = secinfo;
 455     }
 456   else
 457     secinfo->next = secinfo;
 458   sinfo->chain = secinfo;
 459   secinfo->sec = sec;
 460   secinfo->psecinfo = psecinfo;
 461   secinfo->htab = sinfo->htab;
 462   secinfo->first_str = NULL;
 463
 464   sec->rawsize = sec->size;
 465   if (sec->flags & SEC_STRINGS)
 466     memset (secinfo->contents + sec->size, 0, sec->entsize);
 467   contents = secinfo->contents;
 468   if (! bfd_get_full_section_contents (sec->owner, sec, &contents))
 469     goto error_return;
 470
 471   return true;
 472
 473  error_return:
 474   *psecinfo = NULL;
 475   return false;
 476 }
 477
 478 /* Record one section into the hash table.  */
 479 static bool
 480 record_section (struct sec_merge_info *sinfo,
 481                 struct sec_merge_sec_info *secinfo)
 482 {
 483   asection *sec = secinfo->sec;
 484   struct sec_merge_hash_entry *entry;
 485   bool nul;
 486   unsigned char *p, *end;
 487   bfd_vma mask, eltalign;
 488   unsigned int align, i;
 489
 490   align = sec->alignment_power;
 491   end = secinfo->contents + sec->size;
 492   nul = false;
 493   mask = ((bfd_vma) 1 << align) - 1;
 494   if (sec->flags & SEC_STRINGS)
 495     {
 496       for (p = secinfo->contents; p < end; )
 497         {
 498           eltalign = p - secinfo->contents;
 499           eltalign = ((eltalign ^ (eltalign - 1)) + 1) >> 1;
 500           if (!eltalign || eltalign > mask)
 501             eltalign = mask + 1;
 502           entry = sec_merge_add (sinfo->htab, (char *) p, (unsigned) eltalign,
 503                                  secinfo);
 504           if (! entry)
 505             goto error_return;
 506           p += entry->len;
 507           if (sec->entsize == 1)
 508             {
 509               while (p < end && *p == 0)
 510                 {
 511                   if (!nul && !((p - secinfo->contents) & mask))
 512                     {
 513                       nul = true;
 514                       entry = sec_merge_add (sinfo->htab, "",
 515                                              (unsigned) mask + 1, secinfo);
 516                       if (! entry)
 517                         goto error_return;
 518                     }
 519                   p++;
 520                 }
 521             }
 522           else
 523             {
 524               while (p < end)
 525                 {
 526                   for (i = 0; i < sec->entsize; i++)
 527                     if (p[i] != '\0')
 528                       break;
 529                   if (i != sec->entsize)
 530                     break;
 531                   if (!nul && !((p - secinfo->contents) & mask))
 532                     {
 533                       nul = true;
 534                       entry = sec_merge_add (sinfo->htab, (char *) p,
 535                                              (unsigned) mask + 1, secinfo);
 536                       if (! entry)
 537                         goto error_return;
 538                     }
 539                   p += sec->entsize;
 540                 }
 541             }
 542         }
 543     }
 544   else
 545     {
 546       for (p = secinfo->contents; p < end; p += sec->entsize)
 547         {
 548           entry = sec_merge_add (sinfo->htab, (char *) p, 1, secinfo);
 549           if (! entry)
 550             goto error_return;
 551         }
 552     }
 553
 554   return true;
 555
 556  error_return:
 557   for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 558     *secinfo->psecinfo = NULL;
 559   return false;
 560 }
 561
 562 /* qsort comparison function.  Won't ever return zero as all entries
 563    differ, so there is no issue with qsort stability here.  */
 564
 565 static int
 566 strrevcmp (const void *a, const void *b)
 567 {
 568   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 569   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 570   unsigned int lenA = A->len;
 571   unsigned int lenB = B->len;
 572   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 573   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 574   int l = lenA < lenB ? lenA : lenB;
 575
 576   while (l)
 577     {
 578       if (*s != *t)
 579         return (int) *s - (int) *t;
 580       s--;
 581       t--;
 582       l--;
 583     }
 584   return lenA - lenB;
 585 }
 586
 587 /* Like strrevcmp, but for the case where all strings have the same
 588    alignment > entsize.  */
 589
 590 static int
 591 strrevcmp_align (const void *a, const void *b)
 592 {
 593   struct sec_merge_hash_entry *A = *(struct sec_merge_hash_entry **) a;
 594   struct sec_merge_hash_entry *B = *(struct sec_merge_hash_entry **) b;
 595   unsigned int lenA = A->len;
 596   unsigned int lenB = B->len;
 597   const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;
 598   const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;
 599   int l = lenA < lenB ? lenA : lenB;
 600   int tail_align = (lenA & (A->alignment - 1)) - (lenB & (A->alignment - 1));
 601
 602   if (tail_align != 0)
 603     return tail_align;
 604
 605   while (l)
 606     {
 607       if (*s != *t)
 608         return (int) *s - (int) *t;
 609       s--;
 610       t--;
 611       l--;
 612     }
 613   return lenA - lenB;
 614 }
 615
 616 static inline int
 617 is_suffix (const struct sec_merge_hash_entry *A,
 618            const struct sec_merge_hash_entry *B)
 619 {
 620   if (A->len <= B->len)
 621     /* B cannot be a suffix of A unless A is equal to B, which is guaranteed
 622        not to be equal by the hash table.  */
 623     return 0;
 624
 625   return memcmp (A->root.string + (A->len - B->len),
 626                  B->root.string, B->len) == 0;
 627 }
 628
 629 /* This is a helper function for _bfd_merge_sections.  It attempts to
 630    merge strings matching suffixes of longer strings.  */
 631 static struct sec_merge_sec_info *
 632 merge_strings (struct sec_merge_info *sinfo)
 633 {
 634   struct sec_merge_hash_entry **array, **a, *e;
 635   struct sec_merge_sec_info *secinfo;
 636   bfd_size_type size, amt;
 637   unsigned int alignment = 0;
 638
 639   /* Now sort the strings */
 640   amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
 641   array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
 642   if (array == NULL)
 643     return NULL;
 644
 645   for (e = sinfo->htab->first, a = array; e; e = e->next)
 646     if (e->alignment)
 647       {
 648         *a++ = e;
 649         /* Adjust the length to not include the zero terminator.  */
 650         e->len -= sinfo->htab->entsize;
 651         if (alignment != e->alignment)
 652           {
 653             if (alignment == 0)
 654               alignment = e->alignment;
 655             else
 656               alignment = (unsigned) -1;
 657           }
 658       }
 659
 660   sinfo->htab->size = a - array;
 661   if (sinfo->htab->size != 0)
 662     {
 663       qsort (array, (size_t) sinfo->htab->size,
 664              sizeof (struct sec_merge_hash_entry *),
 665              (alignment != (unsigned) -1 && alignment > sinfo->htab->entsize
 666               ? strrevcmp_align : strrevcmp));
 667
 668       /* Loop over the sorted array and merge suffixes */
 669       e = *--a;
 670       e->len += sinfo->htab->entsize;
 671       while (--a >= array)
 672         {
 673           struct sec_merge_hash_entry *cmp = *a;
 674
 675           cmp->len += sinfo->htab->entsize;
 676           if (e->alignment >= cmp->alignment
 677               && !((e->len - cmp->len) & (cmp->alignment - 1))
 678               && is_suffix (e, cmp))
 679             {
 680               cmp->u.suffix = e;
 681               cmp->alignment = 0;
 682             }
 683           else
 684             e = cmp;
 685         }
 686     }
 687
 688   free (array);
 689
 690   /* Now assign positions to the strings we want to keep.  */
 691   size = 0;
 692   secinfo = sinfo->htab->first->secinfo;
 693   for (e = sinfo->htab->first; e; e = e->next)
 694     {
 695       if (e->secinfo != secinfo)
 696         {
 697           secinfo->sec->size = size;
 698           secinfo = e->secinfo;
 699         }
 700       if (e->alignment)
 701         {
 702           if (e->secinfo->first_str == NULL)
 703             {
 704               e->secinfo->first_str = e;
 705               size = 0;
 706             }
 707           size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 708           e->u.index = size;
 709           size += e->len;
 710         }
 711     }
 712   secinfo->sec->size = size;
 713
 714   /* And now adjust the rest, removing them from the chain (but not hashtable)
 715      at the same time.  */
 716   for (a = &sinfo->htab->first, e = *a; e; e = e->next)
 717     if (e->alignment)
 718       a = &e->next;
 719     else
 720       {
 721         *a = e->next;
 722         if (e->len)
 723           {
 724             e->secinfo = e->u.suffix->secinfo;
 725             e->alignment = e->u.suffix->alignment;
 726             e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
 727           }
 728       }
 729   return secinfo;
 730 }
 731
 732 /* This function is called once after all SEC_MERGE sections are registered
 733    with _bfd_merge_section.  */
 734
 735 bool
 736 _bfd_merge_sections (bfd *abfd,
 737                      struct bfd_link_info *info ATTRIBUTE_UNUSED,
 738                      void *xsinfo,
 739                      void (*remove_hook) (bfd *, asection *))
 740 {
 741   struct sec_merge_info *sinfo;
 742
 743   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 744     {
 745       struct sec_merge_sec_info *secinfo;
 746       bfd_size_type align;  /* Bytes.  */
 747
 748       if (! sinfo->chain)
 749         continue;
 750
 751       /* Move sinfo->chain to head of the chain, terminate it.  */
 752       secinfo = sinfo->chain;
 753       sinfo->chain = secinfo->next;
 754       secinfo->next = NULL;
 755
 756       /* Record the sections into the hash table.  */
 757       align = 1;
 758       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 759         if (secinfo->sec->flags & SEC_EXCLUDE)
 760           {
 761             *secinfo->psecinfo = NULL;
 762             if (remove_hook)
 763               (*remove_hook) (abfd, secinfo->sec);
 764           }
 765         else
 766           {
 767             if (!record_section (sinfo, secinfo))
 768               return false;
 769             if (align)
 770               {
 771                 unsigned int opb = bfd_octets_per_byte (abfd, secinfo->sec);
 772
 773                 align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
 774                 if (((secinfo->sec->size / opb) & (align - 1)) != 0)
 775                   align = 0;
 776               }
 777           }
 778
 779       if (sinfo->htab->first == NULL)
 780         continue;
 781
 782       if (sinfo->htab->strings)
 783         {
 784           secinfo = merge_strings (sinfo);
 785           if (!secinfo)
 786             return false;
 787         }
 788       else
 789         {
 790           struct sec_merge_hash_entry *e;
 791           bfd_size_type size = 0;  /* Octets.  */
 792
 793           /* Things are much simpler for non-strings.
 794              Just assign them slots in the section.  */
 795           secinfo = NULL;
 796           for (e = sinfo->htab->first; e; e = e->next)
 797             {
 798               if (e->secinfo->first_str == NULL)
 799                 {
 800                   if (secinfo)
 801                     secinfo->sec->size = size;
 802                   e->secinfo->first_str = e;
 803                   size = 0;
 804                 }
 805               size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 806               e->u.index = size;
 807               size += e->len;
 808               secinfo = e->secinfo;
 809             }
 810           secinfo->sec->size = size;
 811         }
 812
 813       /* If the input sections were padded according to their alignments,
 814          then pad the output too.  */
 815       if (align)
 816         secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
 817
 818       /* Finally remove all input sections which have not made it into
 819          the hash table at all.  */
 820       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 821         if (secinfo->first_str == NULL)
 822           secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
 823     }
 824
 825   return true;
 826 }
 827
 828 /* Write out the merged section.  */
 829
 830 bool
 831 _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
 832 {
 833   struct sec_merge_sec_info *secinfo;
 834   file_ptr pos;
 835   unsigned char *contents;
 836   Elf_Internal_Shdr *hdr;
 837
 838   secinfo = (struct sec_merge_sec_info *) psecinfo;
 839
 840   if (!secinfo)
 841     return false;
 842
 843   if (secinfo->first_str == NULL)
 844     return true;
 845
 846   /* FIXME: octets_per_byte.  */
 847   hdr = &elf_section_data (sec->output_section)->this_hdr;
 848   if (hdr->sh_offset == (file_ptr) -1)
 849     {
 850       /* We must compress this section.  Write output to the
 851          buffer.  */
 852       contents = hdr->contents;
 853       if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
 854           || contents == NULL)
 855         abort ();
 856     }
 857   else
 858     {
 859       contents = NULL;
 860       pos = sec->output_section->filepos + sec->output_offset;
 861       if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
 862         return false;
 863     }
 864
 865   if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
 866                         sec->output_offset))
 867     return false;
 868
 869   return true;
 870 }
 871
 872 /* Adjust an address in the SEC_MERGE section.  Given OFFSET within
 873    *PSEC, this returns the new offset in the adjusted SEC_MERGE
 874    section and writes the new section back into *PSEC.  */
 875
 876 bfd_vma
 877 _bfd_merged_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, asection **psec,
 878                             void *psecinfo, bfd_vma offset)
 879 {
 880   struct sec_merge_sec_info *secinfo;
 881   struct sec_merge_hash_entry *entry;
 882   unsigned char *p;
 883   asection *sec = *psec;
 884
 885   secinfo = (struct sec_merge_sec_info *) psecinfo;
 886
 887   if (!secinfo)
 888     return offset;
 889
 890   if (offset >= sec->rawsize)
 891     {
 892       if (offset > sec->rawsize)
 893         _bfd_error_handler
 894           /* xgettext:c-format */
 895           (_("%pB: access beyond end of merged section (%" PRId64 ")"),
 896            sec->owner, (int64_t) offset);
 897       return secinfo->first_str ? sec->size : 0;
 898     }
 899
 900   if (secinfo->htab->strings)
 901     {
 902       if (sec->entsize == 1)
 903         {
 904           p = secinfo->contents + offset - 1;
 905           while (p >= secinfo->contents && *p)
 906             --p;
 907           ++p;
 908         }
 909       else
 910         {
 911           p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 912           p -= sec->entsize;
 913           while (p >= secinfo->contents)
 914             {
 915               unsigned int i;
 916
 917               for (i = 0; i < sec->entsize; ++i)
 918                 if (p[i] != '\0')
 919                   break;
 920               if (i == sec->entsize)
 921                 break;
 922               p -= sec->entsize;
 923             }
 924           p += sec->entsize;
 925         }
 926     }
 927   else
 928     {
 929       p = secinfo->contents + (offset / sec->entsize) * sec->entsize;
 930     }
 931   entry = sec_merge_hash_lookup (secinfo->htab, (char *) p, 0, false);
 932   if (!entry)
 933     {
 934       if (! secinfo->htab->strings)
 935         abort ();
 936       /* This should only happen if somebody points into the padding
 937          after a NUL character but before next entity.  */
 938       if (*p)
 939         abort ();
 940       if (! secinfo->htab->first)
 941         abort ();
 942       entry = secinfo->htab->first;
 943       p = (secinfo->contents + (offset / sec->entsize + 1) * sec->entsize
 944            - entry->len);
 945     }
 946
 947   *psec = entry->secinfo->sec;
 948   return entry->u.index + (secinfo->contents + offset - p);
 949 }
 950
 951 /* Tidy up when done.  */
 952
 953 void
 954 _bfd_merge_sections_free (void *xsinfo)
 955 {
 956   struct sec_merge_info *sinfo;
 957
 958   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
 959     {
 960       bfd_hash_table_free (&sinfo->htab->table);
 961       free (sinfo->htab);
 962     }
 963 }