bfd/elf-attrs.c

   1 /* ELF attributes support (based on ARM EABI attributes).
   2    Copyright (C) 2005-2018 Free Software Foundation, Inc.
   3
   4    This file is part of BFD, the Binary File Descriptor library.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  19    MA 02110-1301, USA.  */
  20
  21 #include "sysdep.h"
  22 #include "bfd.h"
  23 #include "libiberty.h"
  24 #include "libbfd.h"
  25 #include "elf-bfd.h"
  26
  27 /* Return the number of bytes needed by I in uleb128 format.  */
  28 static int
  29 uleb128_size (unsigned int i)
  30 {
  31   int size;
  32   size = 1;
  33   while (i >= 0x80)
  34     {
  35       i >>= 7;
  36       size++;
  37     }
  38   return size;
  39 }
  40
  41 /* Return TRUE if the attribute has the default value (0/"").  */
  42 static bfd_boolean
  43 is_default_attr (obj_attribute *attr)
  44 {
  45   if (ATTR_TYPE_HAS_ERROR (attr->type))
  46     return TRUE;
  47   if (ATTR_TYPE_HAS_INT_VAL (attr->type) && attr->i != 0)
  48     return FALSE;
  49   if (ATTR_TYPE_HAS_STR_VAL (attr->type) && attr->s && *attr->s)
  50     return FALSE;
  51   if (ATTR_TYPE_HAS_NO_DEFAULT (attr->type))
  52     return FALSE;
  53
  54   return TRUE;
  55 }
  56
  57 /* Return the size of a single attribute.  */
  58 static bfd_vma
  59 obj_attr_size (unsigned int tag, obj_attribute *attr)
  60 {
  61   bfd_vma size;
  62
  63   if (is_default_attr (attr))
  64     return 0;
  65
  66   size = uleb128_size (tag);
  67   if (ATTR_TYPE_HAS_INT_VAL (attr->type))
  68     size += uleb128_size (attr->i);
  69   if (ATTR_TYPE_HAS_STR_VAL (attr->type))
  70     size += strlen ((char *)attr->s) + 1;
  71   return size;
  72 }
  73
  74 /* Return the vendor name for a given object attributes section.  */
  75 static const char *
  76 vendor_obj_attr_name (bfd *abfd, int vendor)
  77 {
  78   return (vendor == OBJ_ATTR_PROC
  79           ? get_elf_backend_data (abfd)->obj_attrs_vendor
  80           : "gnu");
  81 }
  82
  83 /* Return the size of the object attributes section for VENDOR
  84    (OBJ_ATTR_PROC or OBJ_ATTR_GNU), or 0 if there are no attributes
  85    for that vendor to record and the vendor is OBJ_ATTR_GNU.  */
  86 static bfd_vma
  87 vendor_obj_attr_size (bfd *abfd, int vendor)
  88 {
  89   bfd_vma size;
  90   obj_attribute *attr;
  91   obj_attribute_list *list;
  92   int i;
  93   const char *vendor_name = vendor_obj_attr_name (abfd, vendor);
  94
  95   if (!vendor_name)
  96     return 0;
  97
  98   attr = elf_known_obj_attributes (abfd)[vendor];
  99   size = 0;
 100   for (i = LEAST_KNOWN_OBJ_ATTRIBUTE; i < NUM_KNOWN_OBJ_ATTRIBUTES; i++)
 101     size += obj_attr_size (i, &attr[i]);
 102
 103   for (list = elf_other_obj_attributes (abfd)[vendor];
 104        list;
 105        list = list->next)
 106     size += obj_attr_size (list->tag, &list->attr);
 107
 108   /* <size> <vendor_name> NUL 0x1 <size> */
 109   return ((size || vendor == OBJ_ATTR_PROC)
 110           ? size + 10 + strlen (vendor_name)
 111           : 0);
 112 }
 113
 114 /* Return the size of the object attributes section.  */
 115 bfd_vma
 116 bfd_elf_obj_attr_size (bfd *abfd)
 117 {
 118   bfd_vma size;
 119
 120   size = vendor_obj_attr_size (abfd, OBJ_ATTR_PROC);
 121   size += vendor_obj_attr_size (abfd, OBJ_ATTR_GNU);
 122
 123   /* 'A' <sections for each vendor> */
 124   return (size ? size + 1 : 0);
 125 }
 126
 127 /* Write VAL in uleb128 format to P, returning a pointer to the
 128    following byte.  */
 129 static bfd_byte *
 130 write_uleb128 (bfd_byte *p, unsigned int val)
 131 {
 132   bfd_byte c;
 133   do
 134     {
 135       c = val & 0x7f;
 136       val >>= 7;
 137       if (val)
 138         c |= 0x80;
 139       *(p++) = c;
 140     }
 141   while (val);
 142   return p;
 143 }
 144
 145 /* Write attribute ATTR to butter P, and return a pointer to the following
 146    byte.  */
 147 static bfd_byte *
 148 write_obj_attribute (bfd_byte *p, unsigned int tag, obj_attribute *attr)
 149 {
 150   /* Suppress default entries.  */
 151   if (is_default_attr (attr))
 152     return p;
 153
 154   p = write_uleb128 (p, tag);
 155   if (ATTR_TYPE_HAS_INT_VAL (attr->type))
 156     p = write_uleb128 (p, attr->i);
 157   if (ATTR_TYPE_HAS_STR_VAL (attr->type))
 158     {
 159       int len;
 160
 161       len = strlen (attr->s) + 1;
 162       memcpy (p, attr->s, len);
 163       p += len;
 164     }
 165
 166   return p;
 167 }
 168
 169 /* Write the contents of the object attributes section (length SIZE)
 170    for VENDOR to CONTENTS.  */
 171 static void
 172 vendor_set_obj_attr_contents (bfd *abfd, bfd_byte *contents, bfd_vma size,
 173                               int vendor)
 174 {
 175   bfd_byte *p;
 176   obj_attribute *attr;
 177   obj_attribute_list *list;
 178   int i;
 179   const char *vendor_name = vendor_obj_attr_name (abfd, vendor);
 180   size_t vendor_length = strlen (vendor_name) + 1;
 181
 182   p = contents;
 183   bfd_put_32 (abfd, size, p);
 184   p += 4;
 185   memcpy (p, vendor_name, vendor_length);
 186   p += vendor_length;
 187   *(p++) = Tag_File;
 188   bfd_put_32 (abfd, size - 4 - vendor_length, p);
 189   p += 4;
 190
 191   attr = elf_known_obj_attributes (abfd)[vendor];
 192   for (i = LEAST_KNOWN_OBJ_ATTRIBUTE; i < NUM_KNOWN_OBJ_ATTRIBUTES; i++)
 193     {
 194       unsigned int tag = i;
 195       if (get_elf_backend_data (abfd)->obj_attrs_order)
 196         tag = get_elf_backend_data (abfd)->obj_attrs_order (i);
 197       p = write_obj_attribute (p, tag, &attr[tag]);
 198     }
 199
 200   for (list = elf_other_obj_attributes (abfd)[vendor];
 201        list;
 202        list = list->next)
 203     p = write_obj_attribute (p, list->tag, &list->attr);
 204 }
 205
 206 /* Write the contents of the object attributes section to CONTENTS.  */
 207 void
 208 bfd_elf_set_obj_attr_contents (bfd *abfd, bfd_byte *contents, bfd_vma size)
 209 {
 210   bfd_byte *p;
 211   int vendor;
 212   bfd_vma my_size;
 213
 214   p = contents;
 215   *(p++) = 'A';
 216   my_size = 1;
 217   for (vendor = OBJ_ATTR_FIRST; vendor <= OBJ_ATTR_LAST; vendor++)
 218     {
 219       bfd_vma vendor_size = vendor_obj_attr_size (abfd, vendor);
 220       if (vendor_size)
 221         vendor_set_obj_attr_contents (abfd, p, vendor_size, vendor);
 222       p += vendor_size;
 223       my_size += vendor_size;
 224     }
 225
 226   if (size != my_size)
 227     abort ();
 228 }
 229
 230 /* Allocate/find an object attribute.  */
 231 static obj_attribute *
 232 elf_new_obj_attr (bfd *abfd, int vendor, unsigned int tag)
 233 {
 234   obj_attribute *attr;
 235   obj_attribute_list *list;
 236   obj_attribute_list *p;
 237   obj_attribute_list **lastp;
 238
 239
 240   if (tag < NUM_KNOWN_OBJ_ATTRIBUTES)
 241     {
 242       /* Known tags are preallocated.  */
 243       attr = &elf_known_obj_attributes (abfd)[vendor][tag];
 244     }
 245   else
 246     {
 247       /* Create a new tag.  */
 248       list = (obj_attribute_list *)
 249         bfd_alloc (abfd, sizeof (obj_attribute_list));
 250       memset (list, 0, sizeof (obj_attribute_list));
 251       list->tag = tag;
 252       /* Keep the tag list in order.  */
 253       lastp = &elf_other_obj_attributes (abfd)[vendor];
 254       for (p = *lastp; p; p = p->next)
 255         {
 256           if (tag < p->tag)
 257             break;
 258           lastp = &p->next;
 259         }
 260       list->next = *lastp;
 261       *lastp = list;
 262       attr = &list->attr;
 263     }
 264
 265   return attr;
 266 }
 267
 268 /* Return the value of an integer object attribute.  */
 269 int
 270 bfd_elf_get_obj_attr_int (bfd *abfd, int vendor, unsigned int tag)
 271 {
 272   obj_attribute_list *p;
 273
 274   if (tag < NUM_KNOWN_OBJ_ATTRIBUTES)
 275     {
 276       /* Known tags are preallocated.  */
 277       return elf_known_obj_attributes (abfd)[vendor][tag].i;
 278     }
 279   else
 280     {
 281       for (p = elf_other_obj_attributes (abfd)[vendor];
 282            p;
 283            p = p->next)
 284         {
 285           if (tag == p->tag)
 286             return p->attr.i;
 287           if (tag < p->tag)
 288             break;
 289         }
 290       return 0;
 291     }
 292 }
 293
 294 /* Add an integer object attribute.  */
 295 void
 296 bfd_elf_add_obj_attr_int (bfd *abfd, int vendor, unsigned int tag, unsigned int i)
 297 {
 298   obj_attribute *attr;
 299
 300   attr = elf_new_obj_attr (abfd, vendor, tag);
 301   attr->type = _bfd_elf_obj_attrs_arg_type (abfd, vendor, tag);
 302   attr->i = i;
 303 }
 304
 305 /* Duplicate an object attribute string value.  */
 306 char *
 307 _bfd_elf_attr_strdup (bfd *abfd, const char * s)
 308 {
 309   char * p;
 310   int len;
 311
 312   len = strlen (s) + 1;
 313   p = (char *) bfd_alloc (abfd, len);
 314   return (char *) memcpy (p, s, len);
 315 }
 316
 317 /* Add a string object attribute.  */
 318 void
 319 bfd_elf_add_obj_attr_string (bfd *abfd, int vendor, unsigned int tag, const char *s)
 320 {
 321   obj_attribute *attr;
 322
 323   attr = elf_new_obj_attr (abfd, vendor, tag);
 324   attr->type = _bfd_elf_obj_attrs_arg_type (abfd, vendor, tag);
 325   attr->s = _bfd_elf_attr_strdup (abfd, s);
 326 }
 327
 328 /* Add a int+string object attribute.  */
 329 void
 330 bfd_elf_add_obj_attr_int_string (bfd *abfd, int vendor,
 331                                  unsigned int tag,
 332                                  unsigned int i, const char *s)
 333 {
 334   obj_attribute *attr;
 335
 336   attr = elf_new_obj_attr (abfd, vendor, tag);
 337   attr->type = _bfd_elf_obj_attrs_arg_type (abfd, vendor, tag);
 338   attr->i = i;
 339   attr->s = _bfd_elf_attr_strdup (abfd, s);
 340 }
 341
 342 /* Copy the object attributes from IBFD to OBFD.  */
 343 void
 344 _bfd_elf_copy_obj_attributes (bfd *ibfd, bfd *obfd)
 345 {
 346   obj_attribute *in_attr;
 347   obj_attribute *out_attr;
 348   obj_attribute_list *list;
 349   int i;
 350   int vendor;
 351
 352   if (bfd_get_flavour (ibfd) != bfd_target_elf_flavour
 353       || bfd_get_flavour (obfd) != bfd_target_elf_flavour)
 354     return;
 355
 356   for (vendor = OBJ_ATTR_FIRST; vendor <= OBJ_ATTR_LAST; vendor++)
 357     {
 358       in_attr
 359         = &elf_known_obj_attributes (ibfd)[vendor][LEAST_KNOWN_OBJ_ATTRIBUTE];
 360       out_attr
 361         = &elf_known_obj_attributes (obfd)[vendor][LEAST_KNOWN_OBJ_ATTRIBUTE];
 362       for (i = LEAST_KNOWN_OBJ_ATTRIBUTE; i < NUM_KNOWN_OBJ_ATTRIBUTES; i++)
 363         {
 364           out_attr->type = in_attr->type;
 365           out_attr->i = in_attr->i;
 366           if (in_attr->s && *in_attr->s)
 367             out_attr->s = _bfd_elf_attr_strdup (obfd, in_attr->s);
 368           in_attr++;
 369           out_attr++;
 370         }
 371
 372       for (list = elf_other_obj_attributes (ibfd)[vendor];
 373            list;
 374            list = list->next)
 375         {
 376           in_attr = &list->attr;
 377           switch (in_attr->type & (ATTR_TYPE_FLAG_INT_VAL | ATTR_TYPE_FLAG_STR_VAL))
 378             {
 379             case ATTR_TYPE_FLAG_INT_VAL:
 380               bfd_elf_add_obj_attr_int (obfd, vendor, list->tag, in_attr->i);
 381               break;
 382             case ATTR_TYPE_FLAG_STR_VAL:
 383               bfd_elf_add_obj_attr_string (obfd, vendor, list->tag,
 384                                            in_attr->s);
 385               break;
 386             case ATTR_TYPE_FLAG_INT_VAL | ATTR_TYPE_FLAG_STR_VAL:
 387               bfd_elf_add_obj_attr_int_string (obfd, vendor, list->tag,
 388                                                in_attr->i, in_attr->s);
 389               break;
 390             default:
 391               abort ();
 392             }
 393         }
 394     }
 395 }
 396
 397 /* Determine whether a GNU object attribute tag takes an integer, a
 398    string or both.  */
 399 static int
 400 gnu_obj_attrs_arg_type (unsigned int tag)
 401 {
 402   /* Except for Tag_compatibility, for GNU attributes we follow the
 403      same rule ARM ones > 32 follow: odd-numbered tags take strings
 404      and even-numbered tags take integers.  In addition, tag & 2 is
 405      nonzero for architecture-independent tags and zero for
 406      architecture-dependent ones.  */
 407   if (tag == Tag_compatibility)
 408     return 3;
 409   else
 410     return (tag & 1) != 0 ? 2 : 1;
 411 }
 412
 413 /* Determine what arguments an attribute tag takes.  */
 414 int
 415 _bfd_elf_obj_attrs_arg_type (bfd *abfd, int vendor, unsigned int tag)
 416 {
 417   switch (vendor)
 418     {
 419     case OBJ_ATTR_PROC:
 420       return get_elf_backend_data (abfd)->obj_attrs_arg_type (tag);
 421       break;
 422     case OBJ_ATTR_GNU:
 423       return gnu_obj_attrs_arg_type (tag);
 424       break;
 425     default:
 426       abort ();
 427     }
 428 }
 429
 430 /* Parse an object attributes section.  */
 431 void
 432 _bfd_elf_parse_attributes (bfd *abfd, Elf_Internal_Shdr * hdr)
 433 {
 434   bfd_byte *contents;
 435   bfd_byte *p;
 436   bfd_byte *p_end;
 437   bfd_vma len;
 438   const char *std_sec;
 439
 440   /* PR 17512: file: 2844a11d.  */
 441   if (hdr->sh_size == 0)
 442     return;
 443   if (hdr->sh_size > bfd_get_file_size (abfd))
 444     {
 445       /* xgettext:c-format */
 446       _bfd_error_handler (_("%pB: error: attribute section '%pA' too big: %#llx"),
 447                           abfd, hdr->bfd_section, (long long) hdr->sh_size);
 448       bfd_set_error (bfd_error_invalid_operation);
 449       return;
 450     }
 451
 452   contents = (bfd_byte *) bfd_malloc (hdr->sh_size + 1);
 453   if (!contents)
 454     return;
 455   if (!bfd_get_section_contents (abfd, hdr->bfd_section, contents, 0,
 456                                  hdr->sh_size))
 457     {
 458       free (contents);
 459       return;
 460     }
 461   /* Ensure that the buffer is NUL terminated.  */
 462   contents[hdr->sh_size] = 0;
 463   p = contents;
 464   p_end = p + hdr->sh_size;
 465   std_sec = get_elf_backend_data (abfd)->obj_attrs_vendor;
 466
 467   if (*(p++) == 'A')
 468     {
 469       len = hdr->sh_size - 1;
 470
 471       while (len > 0 && p < p_end - 4)
 472         {
 473           unsigned namelen;
 474           bfd_vma section_len;
 475           int vendor;
 476
 477           section_len = bfd_get_32 (abfd, p);
 478           p += 4;
 479           if (section_len == 0)
 480             break;
 481           if (section_len > len)
 482             section_len = len;
 483           len -= section_len;
 484           if (section_len <= 4)
 485             {
 486               _bfd_error_handler
 487                 (_("%pB: error: attribute section length too small: %" PRId64),
 488                  abfd, (int64_t) section_len);
 489               break;
 490             }
 491           section_len -= 4;
 492           namelen = strnlen ((char *) p, section_len) + 1;
 493           if (namelen == 0 || namelen >= section_len)
 494             break;
 495           section_len -= namelen;
 496           if (std_sec && strcmp ((char *) p, std_sec) == 0)
 497             vendor = OBJ_ATTR_PROC;
 498           else if (strcmp ((char *) p, "gnu") == 0)
 499             vendor = OBJ_ATTR_GNU;
 500           else
 501             {
 502               /* Other vendor section.  Ignore it.  */
 503               p += namelen + section_len;
 504               continue;
 505             }
 506
 507           p += namelen;
 508           while (section_len > 0 && p < p_end)
 509             {
 510               unsigned int tag;
 511               unsigned int n;
 512               unsigned int val;
 513               bfd_vma subsection_len;
 514               bfd_byte *end;
 515
 516               tag = _bfd_safe_read_leb128 (abfd, p, &n, FALSE, p_end);
 517               p += n;
 518               if (p < p_end - 4)
 519                 subsection_len = bfd_get_32 (abfd, p);
 520               else
 521                 subsection_len = 0;
 522               p += 4;
 523               if (subsection_len == 0)
 524                 break;
 525               if (subsection_len > section_len)
 526                 subsection_len = section_len;
 527               section_len -= subsection_len;
 528               subsection_len -= n + 4;
 529               end = p + subsection_len;
 530               /* PR 17512: file: 0e8c0c90.  */
 531               if (end > p_end)
 532                 end = p_end;
 533               switch (tag)
 534                 {
 535                 case Tag_File:
 536                   while (p < end)
 537                     {
 538                       int type;
 539
 540                       tag = _bfd_safe_read_leb128 (abfd, p, &n, FALSE, end);
 541                       p += n;
 542                       type = _bfd_elf_obj_attrs_arg_type (abfd, vendor, tag);
 543                       switch (type & (ATTR_TYPE_FLAG_INT_VAL | ATTR_TYPE_FLAG_STR_VAL))
 544                         {
 545                         case ATTR_TYPE_FLAG_INT_VAL | ATTR_TYPE_FLAG_STR_VAL:
 546                           val = _bfd_safe_read_leb128 (abfd, p, &n, FALSE, end);
 547                           p += n;
 548                           bfd_elf_add_obj_attr_int_string (abfd, vendor, tag,
 549                                                            val, (char *) p);
 550                           p += strlen ((char *)p) + 1;
 551                           break;
 552                         case ATTR_TYPE_FLAG_STR_VAL:
 553                           bfd_elf_add_obj_attr_string (abfd, vendor, tag,
 554                                                        (char *) p);
 555                           p += strlen ((char *)p) + 1;
 556                           break;
 557                         case ATTR_TYPE_FLAG_INT_VAL:
 558                           val = _bfd_safe_read_leb128 (abfd, p, &n, FALSE, end);
 559                           p += n;
 560                           bfd_elf_add_obj_attr_int (abfd, vendor, tag, val);
 561                           break;
 562                         default:
 563                           abort ();
 564                         }
 565                     }
 566                   break;
 567                 case Tag_Section:
 568                 case Tag_Symbol:
 569                   /* Don't have anywhere convenient to attach these.
 570                      Fall through for now.  */
 571                 default:
 572                   /* Ignore things we don't kow about.  */
 573                   p += subsection_len;
 574                   subsection_len = 0;
 575                   break;
 576                 }
 577             }
 578         }
 579     }
 580   free (contents);
 581 }
 582
 583 /* Merge common object attributes from IBFD into OBFD.  Raise an error
 584    if there are conflicting attributes.  Any processor-specific
 585    attributes have already been merged.  This must be called from the
 586    bfd_elfNN_bfd_merge_private_bfd_data hook for each individual
 587    target, along with any target-specific merging.  Because there are
 588    no common attributes other than Tag_compatibility at present, and
 589    non-"gnu" Tag_compatibility is not expected in "gnu" sections, this
 590    is not presently called for targets without their own
 591    attributes.  */
 592
 593 bfd_boolean
 594 _bfd_elf_merge_object_attributes (bfd *ibfd, struct bfd_link_info *info)
 595 {
 596   bfd *obfd = info->output_bfd;
 597   obj_attribute *in_attr;
 598   obj_attribute *out_attr;
 599   int vendor;
 600
 601   /* The only common attribute is currently Tag_compatibility,
 602      accepted in both processor and "gnu" sections.  */
 603   for (vendor = OBJ_ATTR_FIRST; vendor <= OBJ_ATTR_LAST; vendor++)
 604     {
 605       /* Handle Tag_compatibility.  The tags are only compatible if the flags
 606          are identical and, if the flags are '1', the strings are identical.
 607          If the flags are non-zero, then we can only use the string "gnu".  */
 608       in_attr = &elf_known_obj_attributes (ibfd)[vendor][Tag_compatibility];
 609       out_attr = &elf_known_obj_attributes (obfd)[vendor][Tag_compatibility];
 610
 611       if (in_attr->i > 0 && strcmp (in_attr->s, "gnu") != 0)
 612         {
 613           _bfd_error_handler
 614             /* xgettext:c-format */
 615                 (_("error: %pB: object has vendor-specific contents that "
 616                    "must be processed by the '%s' toolchain"),
 617                  ibfd, in_attr->s);
 618           return FALSE;
 619         }
 620
 621       if (in_attr->i != out_attr->i
 622           || (in_attr->i != 0 && strcmp (in_attr->s, out_attr->s) != 0))
 623         {
 624           /* xgettext:c-format */
 625           _bfd_error_handler (_("error: %pB: object tag '%d, %s' is "
 626                                 "incompatible with tag '%d, %s'"),
 627                               ibfd,
 628                               in_attr->i, in_attr->s ? in_attr->s : "",
 629                               out_attr->i, out_attr->s ? out_attr->s : "");
 630           return FALSE;
 631         }
 632     }
 633
 634   return TRUE;
 635 }
 636
 637 /* Merge an unknown processor-specific attribute TAG, within the range
 638    of known attributes, from IBFD into OBFD; return TRUE if the link
 639    is OK, FALSE if it must fail.  */
 640
 641 bfd_boolean
 642 _bfd_elf_merge_unknown_attribute_low (bfd *ibfd, bfd *obfd, int tag)
 643 {
 644   obj_attribute *in_attr;
 645   obj_attribute *out_attr;
 646   bfd *err_bfd = NULL;
 647   bfd_boolean result = TRUE;
 648
 649   in_attr = elf_known_obj_attributes_proc (ibfd);
 650   out_attr = elf_known_obj_attributes_proc (obfd);
 651
 652   if (out_attr[tag].i != 0 || out_attr[tag].s != NULL)
 653     err_bfd = obfd;
 654   else if (in_attr[tag].i != 0 || in_attr[tag].s != NULL)
 655     err_bfd = ibfd;
 656
 657   if (err_bfd != NULL)
 658     result
 659       = get_elf_backend_data (err_bfd)->obj_attrs_handle_unknown (err_bfd, tag);
 660
 661   /* Only pass on attributes that match in both inputs.  */
 662   if (in_attr[tag].i != out_attr[tag].i
 663       || (in_attr[tag].s == NULL) != (out_attr[tag].s == NULL)
 664       || (in_attr[tag].s != NULL && out_attr[tag].s != NULL
 665           && strcmp (in_attr[tag].s, out_attr[tag].s) != 0))
 666     {
 667       out_attr[tag].i = 0;
 668       out_attr[tag].s = NULL;
 669     }
 670
 671   return result;
 672 }
 673
 674 /* Merge the lists of unknown processor-specific attributes, outside
 675    the known range, from IBFD into OBFD; return TRUE if the link is
 676    OK, FALSE if it must fail.  */
 677
 678 bfd_boolean
 679 _bfd_elf_merge_unknown_attribute_list (bfd *ibfd, bfd *obfd)
 680 {
 681   obj_attribute_list *in_list;
 682   obj_attribute_list *out_list;
 683   obj_attribute_list **out_listp;
 684   bfd_boolean result = TRUE;
 685
 686   in_list = elf_other_obj_attributes_proc (ibfd);
 687   out_listp = &elf_other_obj_attributes_proc (obfd);
 688   out_list = *out_listp;
 689
 690   for (; in_list || out_list; )
 691     {
 692       bfd *err_bfd = NULL;
 693       unsigned int err_tag = 0;
 694
 695       /* The tags for each list are in numerical order.  */
 696       /* If the tags are equal, then merge.  */
 697       if (out_list && (!in_list || in_list->tag > out_list->tag))
 698         {
 699           /* This attribute only exists in obfd.  We can't merge, and we don't
 700              know what the tag means, so delete it.  */
 701           err_bfd = obfd;
 702           err_tag = out_list->tag;
 703           *out_listp = out_list->next;
 704           out_list = *out_listp;
 705         }
 706       else if (in_list && (!out_list || in_list->tag < out_list->tag))
 707         {
 708           /* This attribute only exists in ibfd. We can't merge, and we don't
 709              know what the tag means, so ignore it.  */
 710           err_bfd = ibfd;
 711           err_tag = in_list->tag;
 712           in_list = in_list->next;
 713         }
 714       else /* The tags are equal.  */
 715         {
 716           /* As present, all attributes in the list are unknown, and
 717              therefore can't be merged meaningfully.  */
 718           err_bfd = obfd;
 719           err_tag = out_list->tag;
 720
 721           /*  Only pass on attributes that match in both inputs.  */
 722           if (in_list->attr.i != out_list->attr.i
 723               || (in_list->attr.s == NULL) != (out_list->attr.s == NULL)
 724               || (in_list->attr.s && out_list->attr.s
 725                   && strcmp (in_list->attr.s, out_list->attr.s) != 0))
 726             {
 727               /* No match.  Delete the attribute.  */
 728               *out_listp = out_list->next;
 729               out_list = *out_listp;
 730             }
 731           else
 732             {
 733               /* Matched.  Keep the attribute and move to the next.  */
 734               out_list = out_list->next;
 735               in_list = in_list->next;
 736             }
 737         }
 738
 739       if (err_bfd)
 740         result = result
 741           && get_elf_backend_data (err_bfd)->obj_attrs_handle_unknown (err_bfd,
 742                                                                        err_tag);
 743     }
 744
 745   return result;
 746 }