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