bfd/format.c

   1 /* Generic BFD support for file formats.
   2    Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1999, 2000, 2001, 2002,
   3    2003, 2005, 2007 Free Software Foundation, Inc.
   4    Written by Cygnus Support.
   5
   6    This file is part of BFD, the Binary File Descriptor library.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21    MA 02110-1301, USA.  */
  22
  23
  24 /*
  25 SECTION
  26         File formats
  27
  28         A format is a BFD concept of high level file contents type. The
  29         formats supported by BFD are:
  30
  31         o <<bfd_object>>
  32
  33         The BFD may contain data, symbols, relocations and debug info.
  34
  35         o <<bfd_archive>>
  36
  37         The BFD contains other BFDs and an optional index.
  38
  39         o <<bfd_core>>
  40
  41         The BFD contains the result of an executable core dump.
  42
  43 SUBSECTION
  44         File format functions
  45 */
  46
  47 #include "sysdep.h"
  48 #include "bfd.h"
  49 #include "libbfd.h"
  50
  51 /* IMPORT from targets.c.  */
  52 extern const size_t _bfd_target_vector_entries;
  53
  54 /*
  55 FUNCTION
  56         bfd_check_format
  57
  58 SYNOPSIS
  59         bfd_boolean bfd_check_format (bfd *abfd, bfd_format format);
  60
  61 DESCRIPTION
  62         Verify if the file attached to the BFD @var{abfd} is compatible
  63         with the format @var{format} (i.e., one of <<bfd_object>>,
  64         <<bfd_archive>> or <<bfd_core>>).
  65
  66         If the BFD has been set to a specific target before the
  67         call, only the named target and format combination is
  68         checked. If the target has not been set, or has been set to
  69         <<default>>, then all the known target backends is
  70         interrogated to determine a match.  If the default target
  71         matches, it is used.  If not, exactly one target must recognize
  72         the file, or an error results.
  73
  74         The function returns <<TRUE>> on success, otherwise <<FALSE>>
  75         with one of the following error codes:
  76
  77         o <<bfd_error_invalid_operation>> -
  78         if <<format>> is not one of <<bfd_object>>, <<bfd_archive>> or
  79         <<bfd_core>>.
  80
  81         o <<bfd_error_system_call>> -
  82         if an error occured during a read - even some file mismatches
  83         can cause bfd_error_system_calls.
  84
  85         o <<file_not_recognised>> -
  86         none of the backends recognised the file format.
  87
  88         o <<bfd_error_file_ambiguously_recognized>> -
  89         more than one backend recognised the file format.
  90 */
  91
  92 bfd_boolean
  93 bfd_check_format (bfd *abfd, bfd_format format)
  94 {
  95   return bfd_check_format_matches (abfd, format, NULL);
  96 }
  97
  98 /*
  99 FUNCTION
 100         bfd_check_format_matches
 101
 102 SYNOPSIS
 103         bfd_boolean bfd_check_format_matches
 104           (bfd *abfd, bfd_format format, char ***matching);
 105
 106 DESCRIPTION
 107         Like <<bfd_check_format>>, except when it returns FALSE with
 108         <<bfd_errno>> set to <<bfd_error_file_ambiguously_recognized>>.  In that
 109         case, if @var{matching} is not NULL, it will be filled in with
 110         a NULL-terminated list of the names of the formats that matched,
 111         allocated with <<malloc>>.
 112         Then the user may choose a format and try again.
 113
 114         When done with the list that @var{matching} points to, the caller
 115         should free it.
 116 */
 117
 118 bfd_boolean
 119 bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
 120 {
 121   extern const bfd_target binary_vec;
 122   const bfd_target * const *target;
 123   const bfd_target **matching_vector = NULL;
 124   const bfd_target *save_targ, *right_targ, *ar_right_targ;
 125   int match_count;
 126   int ar_match_index;
 127
 128   if (!bfd_read_p (abfd)
 129       || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
 130     {
 131       bfd_set_error (bfd_error_invalid_operation);
 132       return FALSE;
 133     }
 134
 135   if (abfd->format != bfd_unknown)
 136     return abfd->format == format;
 137
 138   /* Since the target type was defaulted, check them
 139      all in the hope that one will be uniquely recognized.  */
 140   save_targ = abfd->xvec;
 141   match_count = 0;
 142   ar_match_index = _bfd_target_vector_entries;
 143
 144   if (matching)
 145     {
 146       bfd_size_type amt;
 147
 148       *matching = NULL;
 149       amt = sizeof (*matching_vector) * 2 * _bfd_target_vector_entries;
 150       matching_vector = bfd_malloc (amt);
 151       if (!matching_vector)
 152         return FALSE;
 153     }
 154
 155   right_targ = 0;
 156   ar_right_targ = 0;
 157
 158   /* Presume the answer is yes.  */
 159   abfd->format = format;
 160
 161   /* If the target type was explicitly specified, just check that target.  */
 162   if (!abfd->target_defaulted)
 163     {
 164       if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0) /* rewind! */
 165         {
 166           if (matching)
 167             free (matching_vector);
 168           return FALSE;
 169         }
 170
 171       right_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 172
 173       if (right_targ)
 174         {
 175           abfd->xvec = right_targ;      /* Set the target as returned.  */
 176
 177           if (matching)
 178             free (matching_vector);
 179
 180           /* If the file was opened for update, then `output_has_begun'
 181              some time ago when the file was created.  Do not recompute
 182              sections sizes or alignments in _bfd_set_section_contents.
 183              We can not set this flag until after checking the format,
 184              because it will interfere with creation of BFD sections.  */
 185           if (abfd->direction == both_direction)
 186             abfd->output_has_begun = TRUE;
 187
 188           return TRUE;                  /* File position has moved, BTW.  */
 189         }
 190
 191       /* For a long time the code has dropped through to check all
 192          targets if the specified target was wrong.  I don't know why,
 193          and I'm reluctant to change it.  However, in the case of an
 194          archive, it can cause problems.  If the specified target does
 195          not permit archives (e.g., the binary target), then we should
 196          not allow some other target to recognize it as an archive, but
 197          should instead allow the specified target to recognize it as an
 198          object.  When I first made this change, it broke the PE target,
 199          because the specified pei-i386 target did not recognize the
 200          actual pe-i386 archive.  Since there may be other problems of
 201          this sort, I changed this test to check only for the binary
 202          target.  */
 203       if (format == bfd_archive && save_targ == &binary_vec)
 204         {
 205           abfd->xvec = save_targ;
 206           abfd->format = bfd_unknown;
 207
 208           if (matching)
 209             free (matching_vector);
 210
 211           bfd_set_error (bfd_error_file_not_recognized);
 212
 213           return FALSE;
 214         }
 215     }
 216
 217   for (target = bfd_target_vector; *target != NULL; target++)
 218     {
 219       const bfd_target *temp;
 220       bfd_error_type err;
 221
 222       /* Don't check the default target twice.  */
 223       if (*target == &binary_vec
 224           || (!abfd->target_defaulted && *target == save_targ))
 225         continue;
 226
 227       abfd->xvec = *target;     /* Change BFD's target temporarily.  */
 228
 229       if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
 230         {
 231           if (matching)
 232             free (matching_vector);
 233           return FALSE;
 234         }
 235
 236       /* If _bfd_check_format neglects to set bfd_error, assume
 237          bfd_error_wrong_format.  We didn't used to even pay any
 238          attention to bfd_error, so I suspect that some
 239          _bfd_check_format might have this problem.  */
 240       bfd_set_error (bfd_error_wrong_format);
 241
 242       temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 243
 244       if (temp)
 245         {
 246           /* This format checks out as ok!  */
 247           right_targ = temp;
 248
 249           /* If this is the default target, accept it, even if other
 250              targets might match.  People who want those other targets
 251              have to set the GNUTARGET variable.  */
 252           if (temp == bfd_default_vector[0])
 253             {
 254               match_count = 1;
 255               break;
 256             }
 257
 258           if (matching)
 259             matching_vector[match_count] = temp;
 260
 261           match_count++;
 262         }
 263       else if ((err = bfd_get_error ()) == bfd_error_wrong_object_format
 264                || err == bfd_error_file_ambiguously_recognized)
 265         {
 266           /* An archive with objects of the wrong type, or an
 267              ambiguous match.  We want this target to match if we get
 268              no better matches.  */
 269           if (ar_right_targ != bfd_default_vector[0])
 270             ar_right_targ = *target;
 271           if (matching)
 272             matching_vector[ar_match_index] = *target;
 273           ar_match_index++;
 274         }
 275       else if (err != bfd_error_wrong_format)
 276         {
 277           abfd->xvec = save_targ;
 278           abfd->format = bfd_unknown;
 279
 280           if (matching)
 281             free (matching_vector);
 282
 283           return FALSE;
 284         }
 285     }
 286
 287   if (match_count == 0)
 288     {
 289       /* Try partial matches.  */
 290       right_targ = ar_right_targ;
 291
 292       if (right_targ == bfd_default_vector[0])
 293         {
 294           match_count = 1;
 295         }
 296       else
 297         {
 298           match_count = ar_match_index - _bfd_target_vector_entries;
 299
 300           if (matching && match_count > 1)
 301             memcpy (matching_vector,
 302                     matching_vector + _bfd_target_vector_entries,
 303                     sizeof (*matching_vector) * match_count);
 304         }
 305     }
 306
 307   if (match_count > 1
 308       && bfd_associated_vector != NULL
 309       && matching)
 310     {
 311       const bfd_target * const *assoc = bfd_associated_vector;
 312
 313       while ((right_targ = *assoc++) != NULL)
 314         {
 315           int i = match_count;
 316
 317           while (--i >= 0)
 318             if (matching_vector[i] == right_targ)
 319               break;
 320
 321           if (i >= 0)
 322             {
 323               match_count = 1;
 324               break;
 325             }
 326         }
 327     }
 328
 329   if (match_count == 1)
 330     {
 331       abfd->xvec = right_targ;          /* Change BFD's target permanently.  */
 332
 333       if (matching)
 334         free (matching_vector);
 335
 336       /* If the file was opened for update, then `output_has_begun'
 337          some time ago when the file was created.  Do not recompute
 338          sections sizes or alignments in _bfd_set_section_contents.
 339          We can not set this flag until after checking the format,
 340          because it will interfere with creation of BFD sections.  */
 341       if (abfd->direction == both_direction)
 342         abfd->output_has_begun = TRUE;
 343
 344       return TRUE;                      /* File position has moved, BTW.  */
 345     }
 346
 347   abfd->xvec = save_targ;               /* Restore original target type.  */
 348   abfd->format = bfd_unknown;           /* Restore original format.  */
 349
 350   if (match_count == 0)
 351     {
 352       bfd_set_error (bfd_error_file_not_recognized);
 353
 354       if (matching)
 355         free (matching_vector);
 356     }
 357   else
 358     {
 359       bfd_set_error (bfd_error_file_ambiguously_recognized);
 360
 361       if (matching)
 362         {
 363           *matching = (char **) matching_vector;
 364           matching_vector[match_count] = NULL;
 365           /* Return target names.  This is a little nasty.  Maybe we
 366              should do another bfd_malloc?  */
 367           while (--match_count >= 0)
 368             {
 369               const char *name = matching_vector[match_count]->name;
 370               *(const char **) &matching_vector[match_count] = name;
 371             }
 372         }
 373     }
 374
 375   return FALSE;
 376 }
 377
 378 /*
 379 FUNCTION
 380         bfd_set_format
 381
 382 SYNOPSIS
 383         bfd_boolean bfd_set_format (bfd *abfd, bfd_format format);
 384
 385 DESCRIPTION
 386         This function sets the file format of the BFD @var{abfd} to the
 387         format @var{format}. If the target set in the BFD does not
 388         support the format requested, the format is invalid, or the BFD
 389         is not open for writing, then an error occurs.
 390 */
 391
 392 bfd_boolean
 393 bfd_set_format (bfd *abfd, bfd_format format)
 394 {
 395   if (bfd_read_p (abfd)
 396       || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
 397     {
 398       bfd_set_error (bfd_error_invalid_operation);
 399       return FALSE;
 400     }
 401
 402   if (abfd->format != bfd_unknown)
 403     return abfd->format == format;
 404
 405   /* Presume the answer is yes.  */
 406   abfd->format = format;
 407
 408   if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd)))
 409     {
 410       abfd->format = bfd_unknown;
 411       return FALSE;
 412     }
 413
 414   return TRUE;
 415 }
 416
 417 /*
 418 FUNCTION
 419         bfd_format_string
 420
 421 SYNOPSIS
 422         const char *bfd_format_string (bfd_format format);
 423
 424 DESCRIPTION
 425         Return a pointer to a const string
 426         <<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
 427         depending upon the value of @var{format}.
 428 */
 429
 430 const char *
 431 bfd_format_string (bfd_format format)
 432 {
 433   if (((int) format < (int) bfd_unknown)
 434       || ((int) format >= (int) bfd_type_end))
 435     return "invalid";
 436
 437   switch (format)
 438     {
 439     case bfd_object:
 440       return "object";          /* Linker/assembler/compiler output.  */
 441     case bfd_archive:
 442       return "archive";         /* Object archive file.  */
 443     case bfd_core:
 444       return "core";            /* Core dump.  */
 445     default:
 446       return "unknown";
 447     }
 448 }