bfd/elf-properties.c

   1 /* ELF program property support.
   2    Copyright (C) 2017 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 (_("%B: 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: %B: corrupt GNU_PROPERTY_TYPE (%ld) size: %#lx"),
  92          abfd, note->type, note->descsz);
  93       return FALSE;
  94     }
  95
  96   while (1)
  97     {
  98       unsigned int type = bfd_h_get_32 (abfd, ptr);
  99       unsigned int datasz = bfd_h_get_32 (abfd, ptr + 4);
 100       elf_property *prop;
 101
 102       ptr += 8;
 103
 104       if ((ptr + datasz) > ptr_end)
 105         {
 106           _bfd_error_handler
 107             (_("warning: %B: corrupt GNU_PROPERTY_TYPE (%ld) type (0x%x) datasz: 0x%x"),
 108              abfd, note->type, type, datasz);
 109           /* Clear all properties.  */
 110           elf_properties (abfd) = NULL;
 111           return FALSE;
 112         }
 113
 114       if (type >= GNU_PROPERTY_LOPROC)
 115         {
 116           if (bed->elf_machine_code == EM_NONE)
 117             {
 118               /* Ignore processor-specific properties with generic ELF
 119                  target vector.  They should be handled by the matching
 120                  ELF target vector.  */
 121               goto next;
 122             }
 123           else if (type < GNU_PROPERTY_LOUSER
 124                    && bed->parse_gnu_properties)
 125             {
 126               enum elf_property_kind kind
 127                 = bed->parse_gnu_properties (abfd, type, ptr, datasz);
 128               if (kind == property_corrupt)
 129                 {
 130                   /* Clear all properties.  */
 131                   elf_properties (abfd) = NULL;
 132                   return FALSE;
 133                 }
 134               else if (kind != property_ignored)
 135                 goto next;
 136             }
 137         }
 138       else
 139         {
 140           switch (type)
 141             {
 142             case GNU_PROPERTY_STACK_SIZE:
 143               if (datasz != align_size)
 144                 {
 145                   _bfd_error_handler
 146                     (_("warning: %B: corrupt stack size: 0x%x"),
 147                      abfd, datasz);
 148                   /* Clear all properties.  */
 149                   elf_properties (abfd) = NULL;
 150                   return FALSE;
 151                 }
 152               prop = _bfd_elf_get_property (abfd, type, datasz);
 153               if (datasz == 8)
 154                 prop->u.number = bfd_h_get_64 (abfd, ptr);
 155               else
 156                 prop->u.number = bfd_h_get_32 (abfd, ptr);
 157               prop->pr_kind = property_number;
 158               goto next;
 159
 160             case GNU_PROPERTY_NO_COPY_ON_PROTECTED:
 161               if (datasz != 0)
 162                 {
 163                   _bfd_error_handler
 164                     (_("warning: %B: corrupt no copy on protected size: 0x%x"),
 165                      abfd, datasz);
 166                   /* Clear all properties.  */
 167                   elf_properties (abfd) = NULL;
 168                   return FALSE;
 169                 }
 170               prop = _bfd_elf_get_property (abfd, type, datasz);
 171               elf_has_no_copy_on_protected (abfd) = TRUE;
 172               prop->pr_kind = property_number;
 173               goto next;
 174
 175             default:
 176               break;
 177             }
 178         }
 179
 180       _bfd_error_handler
 181         (_("warning: %B: unsupported GNU_PROPERTY_TYPE (%ld) type: 0x%x"),
 182          abfd, note->type, type);
 183
 184 next:
 185       ptr += (datasz + (align_size - 1)) & ~ (align_size - 1);
 186       if (ptr == ptr_end)
 187         break;
 188
 189       if (ptr > (ptr_end - 8))
 190         goto bad_size;
 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.  */
 332         if ((elf_machine_code
 333              == get_elf_backend_data (abfd)->elf_machine_code)
 334             && (elfclass
 335                 == get_elf_backend_data (abfd)->s->elfclass))
 336           {
 337             /* Keep .note.gnu.property section in FIRST_PBFD.  */
 338             first_pbfd = abfd;
 339             break;
 340           }
 341       }
 342
 343   /* Do nothing if there is no .note.gnu.property section.  */
 344   if (!has_properties)
 345     return NULL;
 346
 347   /* Merge .note.gnu.property sections.  */
 348   for (abfd = info->input_bfds; abfd != NULL; abfd = abfd->link.next)
 349     if (abfd != first_pbfd && (abfd->flags & DYNAMIC) == 0)
 350       {
 351         elf_property_list *null_ptr = NULL;
 352         elf_property_list **listp = &null_ptr;
 353
 354         /* Merge .note.gnu.property section in relocatable ELF input.  */
 355         if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
 356           {
 357             list = elf_properties (abfd);
 358
 359             /* Ignore GNU properties from ELF objects with different
 360                machine code.  */
 361             if (list != NULL
 362                 && (elf_machine_code
 363                     == get_elf_backend_data (abfd)->elf_machine_code))
 364               listp = &elf_properties (abfd);
 365           }
 366         else
 367           list = NULL;
 368
 369         /* Merge properties with FIRST_PBFD.  FIRST_PBFD can be NULL
 370            when all properties are from ELF objects with different
 371            machine code or class.  */
 372         if (first_pbfd != NULL)
 373           elf_merge_gnu_property_list (info, first_pbfd, listp);
 374
 375         if (list != NULL)
 376           {
 377             /* Discard .note.gnu.property section in the rest inputs.  */
 378             sec = bfd_get_section_by_name (abfd,
 379                                            NOTE_GNU_PROPERTY_SECTION_NAME);
 380             sec->output_section = bfd_abs_section_ptr;
 381           }
 382       }
 383
 384   /* Rewrite .note.gnu.property section so that GNU properties are
 385      always sorted by type even if input GNU properties aren't sorted.  */
 386   if (first_pbfd != NULL)
 387     {
 388       unsigned int size;
 389       unsigned int descsz;
 390       bfd_byte *contents;
 391       Elf_External_Note *e_note;
 392       unsigned int align_size = bed->s->elfclass == ELFCLASS64 ? 8 : 4;
 393
 394       sec = bfd_get_section_by_name (first_pbfd,
 395                                      NOTE_GNU_PROPERTY_SECTION_NAME);
 396
 397       /* Update stack size in .note.gnu.property with -z stack-size=N
 398          if N > 0.  */
 399       if (info->stacksize > 0)
 400         {
 401           elf_property *p;
 402           bfd_vma stacksize = info->stacksize;
 403
 404           p = _bfd_elf_get_property (first_pbfd, GNU_PROPERTY_STACK_SIZE,
 405                                      align_size);
 406           if (p->pr_kind == property_unknown)
 407             {
 408               /* Create GNU_PROPERTY_STACK_SIZE.  */
 409               p->u.number = stacksize;
 410               p->pr_kind = property_number;
 411             }
 412           else if (stacksize > p->u.number)
 413             p->u.number = stacksize;
 414         }
 415       else if (elf_properties (first_pbfd) == NULL)
 416         {
 417           /* Discard .note.gnu.property section if all properties have
 418              been removed.  */
 419           sec->output_section = bfd_abs_section_ptr;
 420           return NULL;
 421         }
 422
 423       /* Compute the section size.  */
 424       descsz = offsetof (Elf_External_Note, name[sizeof "GNU"]);
 425       descsz = (descsz + 3) & -(unsigned int) 4;
 426       size = descsz;
 427       for (list = elf_properties (first_pbfd);
 428            list != NULL;
 429            list = list->next)
 430         {
 431           /* There are 4 byte type + 4 byte datasz for each property.  */
 432           size += 4 + 4 + list->property.pr_datasz;
 433           /* Align each property.  */
 434           size = (size + (align_size - 1)) & ~(align_size - 1);
 435         }
 436
 437       /* Update .note.gnu.property section now.  */
 438       sec->size = size;
 439       contents = (bfd_byte *) bfd_zalloc (first_pbfd, size);
 440
 441       e_note = (Elf_External_Note *) contents;
 442       bfd_h_put_32 (first_pbfd, sizeof "GNU", &e_note->namesz);
 443       bfd_h_put_32 (first_pbfd, size - descsz, &e_note->descsz);
 444       bfd_h_put_32 (first_pbfd, NT_GNU_PROPERTY_TYPE_0, &e_note->type);
 445       memcpy (e_note->name, "GNU", sizeof "GNU");
 446
 447       size = descsz;
 448       for (list = elf_properties (first_pbfd);
 449            list != NULL;
 450            list = list->next)
 451         {
 452           /* There are 4 byte type + 4 byte datasz for each property.  */
 453           bfd_h_put_32 (first_pbfd, list->property.pr_type,
 454                         contents + size);
 455           bfd_h_put_32 (first_pbfd, list->property.pr_datasz,
 456                         contents + size + 4);
 457           size += 4 + 4;
 458
 459           /* Write out property value.  */
 460           switch (list->property.pr_kind)
 461             {
 462             case property_number:
 463               switch (list->property.pr_datasz)
 464                 {
 465                 default:
 466                   /* Never should happen.  */
 467                   abort ();
 468
 469                 case 0:
 470                   break;
 471
 472                 case 4:
 473                   bfd_h_put_32 (first_pbfd, list->property.u.number,
 474                                 contents + size);
 475                   break;
 476
 477                 case 8:
 478                   bfd_h_put_64 (first_pbfd, list->property.u.number,
 479                                 contents + size);
 480                   break;
 481                 }
 482               break;
 483
 484             default:
 485               /* Never should happen.  */
 486               abort ();
 487             }
 488           size += list->property.pr_datasz;
 489
 490           /* Align each property.  */
 491           size = (size + (align_size - 1)) & ~ (align_size - 1);
 492         }
 493
 494       /* Cache the section contents for elf_link_input_bfd.  */
 495       elf_section_data (sec)->this_hdr.contents = contents;
 496
 497       /* If GNU_PROPERTY_NO_COPY_ON_PROTECTED is set, protected data
 498          symbol is defined in the shared object.  */
 499       if (elf_has_no_copy_on_protected (first_pbfd))
 500         info->extern_protected_data = FALSE;
 501     }
 502
 503   return first_pbfd;
 504 }