bfd/elf-properties.c

   1 /* ELF program property support.
   2    Copyright (C) 2017-2018 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 /* GNU program property draft is at:
  22
  23    https://github.com/hjl-tools/linux-abi/wiki/property-draft.pdf
  24  */
  25
  26 #include "sysdep.h"
  27 #include "bfd.h"
  28 #include "libbfd.h"
  29 #include "elf-bfd.h"
  30
  31 /* Get a property, allocate a new one if needed.  */
  32
  33 elf_property *
  34 _bfd_elf_get_property (bfd *abfd, unsigned int type, unsigned int datasz)
  35 {
  36   elf_property_list *p, **lastp;
  37
  38   if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
  39     {
  40       /* Never should happen.  */
  41       abort ();
  42     }
  43
  44   /* Keep the property list in order of type.  */
  45   lastp = &elf_properties (abfd);
  46   for (p = *lastp; p; p = p->next)
  47     {
  48       /* Reuse the existing entry.  */
  49       if (type == p->property.pr_type)
  50         {
  51           if (datasz > p->property.pr_datasz)
  52             {
  53               /* This can happen when mixing 32-bit and 64-bit objects.  */
  54               p->property.pr_datasz = datasz;
  55             }
  56           return &p->property;
  57         }
  58       else if (type < p->property.pr_type)
  59         break;
  60       lastp = &p->next;
  61     }
  62   p = (elf_property_list *) bfd_alloc (abfd, sizeof (*p));
  63   if (p == NULL)
  64     {
  65       _bfd_error_handler (_("%pB: out of memory in _bfd_elf_get_property"),
  66                           abfd);
  67       _exit (EXIT_FAILURE);
  68     }
  69   memset (p, 0, sizeof (*p));
  70   p->property.pr_type = type;
  71   p->property.pr_datasz = datasz;
  72   p->next = *lastp;
  73   *lastp = p;
  74   return &p->property;
  75 }
  76
  77 /* Parse GNU properties.  */
  78
  79 bfd_boolean
  80 _bfd_elf_parse_gnu_properties (bfd *abfd, Elf_Internal_Note *note)
  81 {
  82   const struct elf_backend_data *bed = get_elf_backend_data (abfd);
  83   unsigned int align_size = bed->s->elfclass == ELFCLASS64 ? 8 : 4;
  84   bfd_byte *ptr = (bfd_byte *) note->descdata;
  85   bfd_byte *ptr_end = ptr + note->descsz;
  86
  87   if (note->descsz < 8 || (note->descsz % align_size) != 0)
  88     {
  89 bad_size:
  90       _bfd_error_handler
  91         (_("warning: %pB: corrupt GNU_PROPERTY_TYPE (%ld) size: %#lx"),
  92          abfd, note->type, note->descsz);
  93       return FALSE;
  94     }
  95
  96   while (ptr != ptr_end)
  97     {
  98       unsigned int type;
  99       unsigned int datasz;
 100       elf_property *prop;
 101
 102       if ((size_t) (ptr_end - ptr) < 8)
 103         goto bad_size;
 104
 105       type = bfd_h_get_32 (abfd, ptr);
 106       datasz = bfd_h_get_32 (abfd, ptr + 4);
 107       ptr += 8;
 108
 109       if (datasz > (size_t) (ptr_end - ptr))
 110         {
 111           _bfd_error_handler
 112             (_("warning: %pB: corrupt GNU_PROPERTY_TYPE (%ld) type (0x%x) datasz: 0x%x"),
 113              abfd, note->type, type, datasz);
 114           /* Clear all properties.  */
 115           elf_properties (abfd) = NULL;
 116           return FALSE;
 117         }
 118
 119       if (type >= GNU_PROPERTY_LOPROC)
 120         {
 121           if (bed->elf_machine_code == EM_NONE)
 122             {
 123               /* Ignore processor-specific properties with generic ELF
 124                  target vector.  They should be handled by the matching
 125                  ELF target vector.  */
 126               goto next;
 127             }
 128           else if (type < GNU_PROPERTY_LOUSER
 129                    && bed->parse_gnu_properties)
 130             {
 131               enum elf_property_kind kind
 132                 = bed->parse_gnu_properties (abfd, type, ptr, datasz);
 133               if (kind == property_corrupt)
 134                 {
 135                   /* Clear all properties.  */
 136                   elf_properties (abfd) = NULL;
 137                   return FALSE;
 138                 }
 139               else if (kind != property_ignored)
 140                 goto next;
 141             }
 142         }
 143       else
 144         {
 145           switch (type)
 146             {
 147             case GNU_PROPERTY_STACK_SIZE:
 148               if (datasz != align_size)
 149                 {
 150                   _bfd_error_handler
 151                     (_("warning: %pB: corrupt stack size: 0x%x"),
 152                      abfd, datasz);
 153                   /* Clear all properties.  */
 154                   elf_properties (abfd) = NULL;
 155                   return FALSE;
 156                 }
 157               prop = _bfd_elf_get_property (abfd, type, datasz);
 158               if (datasz == 8)
 159                 prop->u.number = bfd_h_get_64 (abfd, ptr);
 160               else
 161                 prop->u.number = bfd_h_get_32 (abfd, ptr);
 162               prop->pr_kind = property_number;
 163               goto next;
 164
 165             case GNU_PROPERTY_NO_COPY_ON_PROTECTED:
 166               if (datasz != 0)
 167                 {
 168                   _bfd_error_handler
 169                     (_("warning: %pB: corrupt no copy on protected size: 0x%x"),
 170                      abfd, datasz);
 171                   /* Clear all properties.  */
 172                   elf_properties (abfd) = NULL;
 173                   return FALSE;
 174                 }
 175               prop = _bfd_elf_get_property (abfd, type, datasz);
 176               elf_has_no_copy_on_protected (abfd) = TRUE;
 177               prop->pr_kind = property_number;
 178               goto next;
 179
 180             default:
 181               break;
 182             }
 183         }
 184
 185       _bfd_error_handler
 186         (_("warning: %pB: unsupported GNU_PROPERTY_TYPE (%ld) type: 0x%x"),
 187          abfd, note->type, type);
 188
 189 next:
 190       ptr += (datasz + (align_size - 1)) & ~ (align_size - 1);
 191     }
 192
 193   return TRUE;
 194 }
 195
 196 /* Merge GNU property BPROP with APROP.  If APROP isn't NULL, return TRUE
 197    if APROP is updated.  Otherwise, return TRUE if BPROP should be merged
 198    with ABFD.  */
 199
 200 static bfd_boolean
 201 elf_merge_gnu_properties (struct bfd_link_info *info, bfd *abfd,
 202                           elf_property *aprop, elf_property *bprop)
 203 {
 204   const struct elf_backend_data *bed = get_elf_backend_data (abfd);
 205   unsigned int pr_type = aprop != NULL ? aprop->pr_type : bprop->pr_type;
 206
 207   if (bed->merge_gnu_properties != NULL
 208       && pr_type >= GNU_PROPERTY_LOPROC
 209       && pr_type < GNU_PROPERTY_LOUSER)
 210     return bed->merge_gnu_properties (info, abfd, aprop, bprop);
 211
 212   switch (pr_type)
 213     {
 214     case GNU_PROPERTY_STACK_SIZE:
 215       if (aprop != NULL && bprop != NULL)
 216         {
 217           if (bprop->u.number > aprop->u.number)
 218             {
 219               aprop->u.number = bprop->u.number;
 220               return TRUE;
 221             }
 222           break;
 223         }
 224       /* FALLTHROUGH */
 225
 226     case GNU_PROPERTY_NO_COPY_ON_PROTECTED:
 227       /* Return TRUE if APROP is NULL to indicate that BPROP should
 228          be added to ABFD.  */
 229       return aprop == NULL;
 230
 231     default:
 232       /* Never should happen.  */
 233       abort ();
 234     }
 235
 236   return FALSE;
 237 }
 238
 239 /* Return the property of TYPE on *LISTP and remove it from *LISTP.
 240    Return NULL if not found.  */
 241
 242 static elf_property *
 243 elf_find_and_remove_property (elf_property_list **listp,
 244                               unsigned int type)
 245 {
 246   elf_property_list *list;
 247
 248   for (list = *listp; list; list = list->next)
 249     {
 250       if (type == list->property.pr_type)
 251         {
 252           /* Remove this property.  */
 253           *listp = list->next;
 254           return &list->property;
 255         }
 256       else if (type < list->property.pr_type)
 257         break;
 258       listp = &list->next;
 259     }
 260
 261   return NULL;
 262 }
 263
 264 /* Merge GNU property list *LISTP with ABFD.  */
 265
 266 static void
 267 elf_merge_gnu_property_list (struct bfd_link_info *info, bfd *abfd,
 268                              elf_property_list **listp)
 269 {
 270   elf_property_list *p, **lastp;
 271   elf_property *pr;
 272
 273   /* Merge each GNU property in ABFD with the one on *LISTP.  */
 274   lastp = &elf_properties (abfd);
 275   for (p = *lastp; p; p = p->next)
 276     {
 277       pr = elf_find_and_remove_property (listp, p->property.pr_type);
 278       /* Pass NULL to elf_merge_gnu_properties for the property which
 279          isn't on *LISTP.  */
 280       elf_merge_gnu_properties (info, abfd, &p->property, pr);
 281       if (p->property.pr_kind == property_remove)
 282         {
 283           /* Remove this property.  */
 284           *lastp = p->next;
 285           continue;
 286         }
 287       lastp = &p->next;
 288     }
 289
 290   /* Merge the remaining properties on *LISTP with ABFD.  */
 291   for (p = *listp; p != NULL; p = p->next)
 292     if (elf_merge_gnu_properties (info, abfd, NULL, &p->property))
 293       {
 294         if (p->property.pr_type == GNU_PROPERTY_NO_COPY_ON_PROTECTED)
 295           elf_has_no_copy_on_protected (abfd) = TRUE;
 296
 297         pr = _bfd_elf_get_property (abfd, p->property.pr_type,
 298                                     p->property.pr_datasz);
 299         /* It must be a new property.  */
 300         if (pr->pr_kind != property_unknown)
 301           abort ();
 302         /* Add a new property.  */
 303         *pr = p->property;
 304       }
 305 }
 306
 307 /* Set up GNU properties.  Return the first relocatable ELF input with
 308    GNU properties if found.  Otherwise, return NULL.  */
 309
 310 bfd *
 311 _bfd_elf_link_setup_gnu_properties (struct bfd_link_info *info)
 312 {
 313   bfd *abfd, *first_pbfd = NULL;
 314   elf_property_list *list;
 315   asection *sec;
 316   bfd_boolean has_properties = FALSE;
 317   const struct elf_backend_data *bed
 318     = get_elf_backend_data (info->output_bfd);
 319   unsigned int elfclass = bed->s->elfclass;
 320   int elf_machine_code = bed->elf_machine_code;
 321
 322   /* Find the first relocatable ELF input with GNU properties.  */
 323   for (abfd = info->input_bfds; abfd != NULL; abfd = abfd->link.next)
 324     if (bfd_get_flavour (abfd) == bfd_target_elf_flavour
 325         && (abfd->flags & DYNAMIC) == 0
 326         && elf_properties (abfd) != NULL)
 327       {
 328         has_properties = TRUE;
 329
 330         /* Ignore GNU properties from ELF objects with different machine
 331            code or class.  Also skip objects without a GNU_PROPERTY note
 332            section.  */
 333         if ((elf_machine_code
 334              == get_elf_backend_data (abfd)->elf_machine_code)
 335             && (elfclass
 336                 == get_elf_backend_data (abfd)->s->elfclass)
 337             && bfd_get_section_by_name (abfd,
 338                                         NOTE_GNU_PROPERTY_SECTION_NAME) != NULL
 339             )
 340           {
 341             /* Keep .note.gnu.property section in FIRST_PBFD.  */
 342             first_pbfd = abfd;
 343             break;
 344           }
 345       }
 346
 347   /* Do nothing if there is no .note.gnu.property section.  */
 348   if (!has_properties)
 349     return NULL;
 350
 351   /* Merge .note.gnu.property sections.  */
 352   for (abfd = info->input_bfds; abfd != NULL; abfd = abfd->link.next)
 353     if (abfd != first_pbfd && (abfd->flags & DYNAMIC) == 0)
 354       {
 355         elf_property_list *null_ptr = NULL;
 356         elf_property_list **listp = &null_ptr;
 357
 358         /* Merge .note.gnu.property section in relocatable ELF input.  */
 359         if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
 360           {
 361             list = elf_properties (abfd);
 362
 363             /* Ignore GNU properties from ELF objects with different
 364                machine code.  */
 365             if (list != NULL
 366                 && (elf_machine_code
 367                     == get_elf_backend_data (abfd)->elf_machine_code))
 368               listp = &elf_properties (abfd);
 369           }
 370         else
 371           list = NULL;
 372
 373         /* Merge properties with FIRST_PBFD.  FIRST_PBFD can be NULL
 374            when all properties are from ELF objects with different
 375            machine code or class.  */
 376         if (first_pbfd != NULL)
 377           elf_merge_gnu_property_list (info, first_pbfd, listp);
 378
 379         if (list != NULL)
 380           {
 381             /* Discard the .note.gnu.property section in this bfd.  */
 382             sec = bfd_get_section_by_name (abfd,
 383                                            NOTE_GNU_PROPERTY_SECTION_NAME);
 384             if (sec != NULL)
 385               sec->output_section = bfd_abs_section_ptr;
 386           }
 387       }
 388
 389   /* Rewrite .note.gnu.property section so that GNU properties are
 390      always sorted by type even if input GNU properties aren't sorted.  */
 391   if (first_pbfd != NULL)
 392     {
 393       unsigned int size;
 394       unsigned int descsz;
 395       bfd_byte *contents;
 396       Elf_External_Note *e_note;
 397       unsigned int align_size = bed->s->elfclass == ELFCLASS64 ? 8 : 4;
 398
 399       sec = bfd_get_section_by_name (first_pbfd,
 400                                      NOTE_GNU_PROPERTY_SECTION_NAME);
 401       BFD_ASSERT (sec != NULL);
 402
 403       /* Update stack size in .note.gnu.property with -z stack-size=N
 404          if N > 0.  */
 405       if (info->stacksize > 0)
 406         {
 407           elf_property *p;
 408           bfd_vma stacksize = info->stacksize;
 409
 410           p = _bfd_elf_get_property (first_pbfd, GNU_PROPERTY_STACK_SIZE,
 411                                      align_size);
 412           if (p->pr_kind == property_unknown)
 413             {
 414               /* Create GNU_PROPERTY_STACK_SIZE.  */
 415               p->u.number = stacksize;
 416               p->pr_kind = property_number;
 417             }
 418           else if (stacksize > p->u.number)
 419             p->u.number = stacksize;
 420         }
 421       else if (elf_properties (first_pbfd) == NULL)
 422         {
 423           /* Discard .note.gnu.property section if all properties have
 424              been removed.  */
 425           sec->output_section = bfd_abs_section_ptr;
 426           return NULL;
 427         }
 428
 429       /* Compute the section size.  */
 430       descsz = offsetof (Elf_External_Note, name[sizeof "GNU"]);
 431       descsz = (descsz + 3) & -(unsigned int) 4;
 432       size = descsz;
 433       for (list = elf_properties (first_pbfd);
 434            list != NULL;
 435            list = list->next)
 436         {
 437           /* There are 4 byte type + 4 byte datasz for each property.  */
 438           size += 4 + 4 + list->property.pr_datasz;
 439           /* Align each property.  */
 440           size = (size + (align_size - 1)) & ~(align_size - 1);
 441         }
 442
 443       /* Update .note.gnu.property section now.  */
 444       sec->size = size;
 445       contents = (bfd_byte *) bfd_zalloc (first_pbfd, size);
 446
 447       e_note = (Elf_External_Note *) contents;
 448       bfd_h_put_32 (first_pbfd, sizeof "GNU", &e_note->namesz);
 449       bfd_h_put_32 (first_pbfd, size - descsz, &e_note->descsz);
 450       bfd_h_put_32 (first_pbfd, NT_GNU_PROPERTY_TYPE_0, &e_note->type);
 451       memcpy (e_note->name, "GNU", sizeof "GNU");
 452
 453       size = descsz;
 454       for (list = elf_properties (first_pbfd);
 455            list != NULL;
 456            list = list->next)
 457         {
 458           /* There are 4 byte type + 4 byte datasz for each property.  */
 459           bfd_h_put_32 (first_pbfd, list->property.pr_type,
 460                         contents + size);
 461           bfd_h_put_32 (first_pbfd, list->property.pr_datasz,
 462                         contents + size + 4);
 463           size += 4 + 4;
 464
 465           /* Write out property value.  */
 466           switch (list->property.pr_kind)
 467             {
 468             case property_number:
 469               switch (list->property.pr_datasz)
 470                 {
 471                 default:
 472                   /* Never should happen.  */
 473                   abort ();
 474
 475                 case 0:
 476                   break;
 477
 478                 case 4:
 479                   bfd_h_put_32 (first_pbfd, list->property.u.number,
 480                                 contents + size);
 481                   break;
 482
 483                 case 8:
 484                   bfd_h_put_64 (first_pbfd, list->property.u.number,
 485                                 contents + size);
 486                   break;
 487                 }
 488               break;
 489
 490             default:
 491               /* Never should happen.  */
 492               abort ();
 493             }
 494           size += list->property.pr_datasz;
 495
 496           /* Align each property.  */
 497           size = (size + (align_size - 1)) & ~ (align_size - 1);
 498         }
 499
 500       /* Cache the section contents for elf_link_input_bfd.  */
 501       elf_section_data (sec)->this_hdr.contents = contents;
 502
 503       /* If GNU_PROPERTY_NO_COPY_ON_PROTECTED is set, protected data
 504          symbol is defined in the shared object.  */
 505       if (elf_has_no_copy_on_protected (first_pbfd))
 506         info->extern_protected_data = FALSE;
 507     }
 508
 509   return first_pbfd;
 510 }