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, 2008, 2009 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, *match_targ;
 125   int match_count, best_count, best_match;
 126   int ar_match_index;
 127
 128   if (matching != NULL)
 129     *matching = NULL;
 130
 131   if (!bfd_read_p (abfd)
 132       || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
 133     {
 134       bfd_set_error (bfd_error_invalid_operation);
 135       return FALSE;
 136     }
 137
 138   if (abfd->format != bfd_unknown)
 139     return abfd->format == format;
 140
 141   /* Since the target type was defaulted, check them
 142      all in the hope that one will be uniquely recognized.  */
 143   save_targ = abfd->xvec;
 144   match_count = 0;
 145   ar_match_index = _bfd_target_vector_entries;
 146
 147   if (matching != NULL || *bfd_associated_vector != NULL)
 148     {
 149       bfd_size_type amt;
 150
 151       amt = sizeof (*matching_vector) * 2 * _bfd_target_vector_entries;
 152       matching_vector = (const bfd_target **) bfd_malloc (amt);
 153       if (!matching_vector)
 154         return FALSE;
 155     }
 156
 157   right_targ = 0;
 158   ar_right_targ = 0;
 159   match_targ = 0;
 160   best_match = 256;
 161   best_count = 0;
 162
 163   /* Presume the answer is yes.  */
 164   abfd->format = format;
 165
 166   /* If the target type was explicitly specified, just check that target.  */
 167   if (!abfd->target_defaulted)
 168     {
 169       if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0) /* rewind! */
 170         goto err_ret;
 171
 172       right_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 173
 174       if (right_targ)
 175         goto ok_ret;
 176
 177       /* For a long time the code has dropped through to check all
 178          targets if the specified target was wrong.  I don't know why,
 179          and I'm reluctant to change it.  However, in the case of an
 180          archive, it can cause problems.  If the specified target does
 181          not permit archives (e.g., the binary target), then we should
 182          not allow some other target to recognize it as an archive, but
 183          should instead allow the specified target to recognize it as an
 184          object.  When I first made this change, it broke the PE target,
 185          because the specified pei-i386 target did not recognize the
 186          actual pe-i386 archive.  Since there may be other problems of
 187          this sort, I changed this test to check only for the binary
 188          target.  */
 189       if (format == bfd_archive && save_targ == &binary_vec)
 190         goto err_unrecog;
 191     }
 192
 193   for (target = bfd_target_vector; *target != NULL; target++)
 194     {
 195       const bfd_target *temp;
 196       bfd_error_type err;
 197
 198       /* Don't check the default target twice.  */
 199       if (*target == &binary_vec
 200           || (!abfd->target_defaulted && *target == save_targ)
 201           || (*target)->match_priority > best_match)
 202         continue;
 203
 204       abfd->xvec = *target;     /* Change BFD's target temporarily.  */
 205
 206       if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
 207         goto err_ret;
 208
 209       /* If _bfd_check_format neglects to set bfd_error, assume
 210          bfd_error_wrong_format.  We didn't used to even pay any
 211          attention to bfd_error, so I suspect that some
 212          _bfd_check_format might have this problem.  */
 213       bfd_set_error (bfd_error_wrong_format);
 214
 215       temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 216       if (temp)
 217         match_targ = temp;
 218
 219       if (temp && (abfd->format != bfd_archive || bfd_has_map (abfd)))
 220         {
 221           /* This format checks out as ok!  */
 222           right_targ = temp;
 223
 224           /* If this is the default target, accept it, even if other
 225              targets might match.  People who want those other targets
 226              have to set the GNUTARGET variable.  */
 227           if (temp == bfd_default_vector[0])
 228             goto ok_ret;
 229
 230           if (matching_vector)
 231             matching_vector[match_count] = temp;
 232           match_count++;
 233
 234           if (temp->match_priority < best_match)
 235             {
 236               best_match = temp->match_priority;
 237               best_count = 0;
 238             }
 239           best_count++;
 240         }
 241       else if (temp
 242                || (err = bfd_get_error ()) == bfd_error_wrong_object_format
 243                || err == bfd_error_file_ambiguously_recognized)
 244         {
 245           /* An archive with no armap or objects of the wrong type,
 246              or an ambiguous match.  We want this target to match
 247              if we get no better matches.  */
 248           if (ar_right_targ != bfd_default_vector[0])
 249             ar_right_targ = *target;
 250           if (matching_vector)
 251             matching_vector[ar_match_index] = *target;
 252           ar_match_index++;
 253         }
 254       else if (err != bfd_error_wrong_format)
 255         goto err_ret;
 256     }
 257
 258   if (best_count == 1)
 259     match_count = 1;
 260
 261   if (match_count == 0)
 262     {
 263       /* Try partial matches.  */
 264       right_targ = ar_right_targ;
 265
 266       if (right_targ == bfd_default_vector[0])
 267         {
 268           match_count = 1;
 269         }
 270       else
 271         {
 272           match_count = ar_match_index - _bfd_target_vector_entries;
 273
 274           if (matching_vector && match_count > 1)
 275             memcpy (matching_vector,
 276                     matching_vector + _bfd_target_vector_entries,
 277                     sizeof (*matching_vector) * match_count);
 278         }
 279     }
 280
 281   if (match_count > 1)
 282     {
 283       const bfd_target * const *assoc = bfd_associated_vector;
 284
 285       while ((right_targ = *assoc++) != NULL)
 286         {
 287           int i = match_count;
 288
 289           while (--i >= 0)
 290             if (matching_vector[i] == right_targ)
 291               break;
 292
 293           if (i >= 0)
 294             {
 295               match_count = 1;
 296               break;
 297             }
 298         }
 299     }
 300
 301   if (match_count == 1)
 302     {
 303       abfd->xvec = right_targ;
 304       /* If we come out of the loop knowing that the last target that
 305          matched is the one we want, then ABFD should still be in a usable
 306          state (except possibly for XVEC).  */
 307       if (match_targ != right_targ)
 308         {
 309           if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
 310             goto err_ret;
 311           match_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
 312         }
 313
 314     ok_ret:
 315       /* If the file was opened for update, then `output_has_begun'
 316          some time ago when the file was created.  Do not recompute
 317          sections sizes or alignments in _bfd_set_section_contents.
 318          We can not set this flag until after checking the format,
 319          because it will interfere with creation of BFD sections.  */
 320       if (abfd->direction == both_direction)
 321         abfd->output_has_begun = TRUE;
 322
 323       if (matching_vector)
 324         free (matching_vector);
 325       return TRUE;                      /* File position has moved, BTW.  */
 326     }
 327
 328   if (match_count == 0)
 329     {
 330     err_unrecog:
 331       bfd_set_error (bfd_error_file_not_recognized);
 332     err_ret:
 333       abfd->xvec = save_targ;
 334       abfd->format = bfd_unknown;
 335       if (matching_vector)
 336         free (matching_vector);
 337       return FALSE;
 338     }
 339
 340   abfd->xvec = save_targ;               /* Restore original target type.  */
 341   abfd->format = bfd_unknown;           /* Restore original format.  */
 342   bfd_set_error (bfd_error_file_ambiguously_recognized);
 343
 344   if (matching)
 345     {
 346       *matching = (char **) matching_vector;
 347       matching_vector[match_count] = NULL;
 348       /* Return target names.  This is a little nasty.  Maybe we
 349          should do another bfd_malloc?  */
 350       while (--match_count >= 0)
 351         {
 352           const char *name = matching_vector[match_count]->name;
 353           *(const char **) &matching_vector[match_count] = name;
 354         }
 355     }
 356   return FALSE;
 357 }
 358
 359 /*
 360 FUNCTION
 361         bfd_set_format
 362
 363 SYNOPSIS
 364         bfd_boolean bfd_set_format (bfd *abfd, bfd_format format);
 365
 366 DESCRIPTION
 367         This function sets the file format of the BFD @var{abfd} to the
 368         format @var{format}. If the target set in the BFD does not
 369         support the format requested, the format is invalid, or the BFD
 370         is not open for writing, then an error occurs.
 371 */
 372
 373 bfd_boolean
 374 bfd_set_format (bfd *abfd, bfd_format format)
 375 {
 376   if (bfd_read_p (abfd)
 377       || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
 378     {
 379       bfd_set_error (bfd_error_invalid_operation);
 380       return FALSE;
 381     }
 382
 383   if (abfd->format != bfd_unknown)
 384     return abfd->format == format;
 385
 386   /* Presume the answer is yes.  */
 387   abfd->format = format;
 388
 389   if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd)))
 390     {
 391       abfd->format = bfd_unknown;
 392       return FALSE;
 393     }
 394
 395   return TRUE;
 396 }
 397
 398 /*
 399 FUNCTION
 400         bfd_format_string
 401
 402 SYNOPSIS
 403         const char *bfd_format_string (bfd_format format);
 404
 405 DESCRIPTION
 406         Return a pointer to a const string
 407         <<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
 408         depending upon the value of @var{format}.
 409 */
 410
 411 const char *
 412 bfd_format_string (bfd_format format)
 413 {
 414   if (((int) format < (int) bfd_unknown)
 415       || ((int) format >= (int) bfd_type_end))
 416     return "invalid";
 417
 418   switch (format)
 419     {
 420     case bfd_object:
 421       return "object";          /* Linker/assembler/compiler output.  */
 422     case bfd_archive:
 423       return "archive";         /* Object archive file.  */
 424     case bfd_core:
 425       return "core";            /* Core dump.  */
 426     default:
 427       return "unknown";
 428     }
 429 }