aboutsummaryrefslogtreecommitdiff
path: root/bfd/format.c
blob: 15237a3b1761108dbe284188622a4c05bad0f864 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
/* Generic BFD support for file formats.
   Copyright (C) 1990-2016 Free Software Foundation, Inc.
   Written by Cygnus Support.

   This file is part of BFD, the Binary File Descriptor library.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
   MA 02110-1301, USA.  */


/*
SECTION
	File formats

	A format is a BFD concept of high level file contents type. The
	formats supported by BFD are:

	o <<bfd_object>>

	The BFD may contain data, symbols, relocations and debug info.

	o <<bfd_archive>>

	The BFD contains other BFDs and an optional index.

	o <<bfd_core>>

	The BFD contains the result of an executable core dump.

SUBSECTION
	File format functions
*/

#include "sysdep.h"
#include "bfd.h"
#include "libbfd.h"

/* IMPORT from targets.c.  */
extern const size_t _bfd_target_vector_entries;

/*
FUNCTION
	bfd_check_format

SYNOPSIS
	bfd_boolean bfd_check_format (bfd *abfd, bfd_format format);

DESCRIPTION
	Verify if the file attached to the BFD @var{abfd} is compatible
	with the format @var{format} (i.e., one of <<bfd_object>>,
	<<bfd_archive>> or <<bfd_core>>).

	If the BFD has been set to a specific target before the
	call, only the named target and format combination is
	checked. If the target has not been set, or has been set to
	<<default>>, then all the known target backends is
	interrogated to determine a match.  If the default target
	matches, it is used.  If not, exactly one target must recognize
	the file, or an error results.

	The function returns <<TRUE>> on success, otherwise <<FALSE>>
	with one of the following error codes:

	o <<bfd_error_invalid_operation>> -
	if <<format>> is not one of <<bfd_object>>, <<bfd_archive>> or
	<<bfd_core>>.

	o <<bfd_error_system_call>> -
	if an error occured during a read - even some file mismatches
	can cause bfd_error_system_calls.

	o <<file_not_recognised>> -
	none of the backends recognised the file format.

	o <<bfd_error_file_ambiguously_recognized>> -
	more than one backend recognised the file format.
*/

bfd_boolean
bfd_check_format (bfd *abfd, bfd_format format)
{
  return bfd_check_format_matches (abfd, format, NULL);
}

struct bfd_preserve
{
  void *marker;
  void *tdata;
  flagword flags;
  const struct bfd_arch_info *arch_info;
  struct bfd_section *sections;
  struct bfd_section *section_last;
  unsigned int section_count;
  struct bfd_hash_table section_htab;
  const struct bfd_build_id *build_id;
};

/* When testing an object for compatibility with a particular target
   back-end, the back-end object_p function needs to set up certain
   fields in the bfd on successfully recognizing the object.  This
   typically happens in a piecemeal fashion, with failures possible at
   many points.  On failure, the bfd is supposed to be restored to its
   initial state, which is virtually impossible.  However, restoring a
   subset of the bfd state works in practice.  This function stores
   the subset.  */

static bfd_boolean
bfd_preserve_save (bfd *abfd, struct bfd_preserve *preserve)
{
  preserve->tdata = abfd->tdata.any;
  preserve->arch_info = abfd->arch_info;
  preserve->flags = abfd->flags;
  preserve->sections = abfd->sections;
  preserve->section_last = abfd->section_last;
  preserve->section_count = abfd->section_count;
  preserve->section_htab = abfd->section_htab;
  preserve->marker = bfd_alloc (abfd, 1);
  preserve->build_id = abfd->build_id;
  if (preserve->marker == NULL)
    return FALSE;

  return bfd_hash_table_init (&abfd->section_htab, bfd_section_hash_newfunc,
			      sizeof (struct section_hash_entry));
}

/* Clear out a subset of BFD state.  */

static void
bfd_reinit (bfd *abfd)
{
  abfd->tdata.any = NULL;
  abfd->arch_info = &bfd_default_arch_struct;
  abfd->flags &= BFD_FLAGS_SAVED;
  bfd_section_list_clear (abfd);
}

/* Restores bfd state saved by bfd_preserve_save.  */

static void
bfd_preserve_restore (bfd *abfd, struct bfd_preserve *preserve)
{
  bfd_hash_table_free (&abfd->section_htab);

  abfd->tdata.any = preserve->tdata;
  abfd->arch_info = preserve->arch_info;
  abfd->flags = preserve->flags;
  abfd->section_htab = preserve->section_htab;
  abfd->sections = preserve->sections;
  abfd->section_last = preserve->section_last;
  abfd->section_count = preserve->section_count;
  abfd->build_id = preserve->build_id;

  /* bfd_release frees all memory more recently bfd_alloc'd than
     its arg, as well as its arg.  */
  bfd_release (abfd, preserve->marker);
  preserve->marker = NULL;
}

/* Called when the bfd state saved by bfd_preserve_save is no longer
   needed.  */

static void
bfd_preserve_finish (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_preserve *preserve)
{
  /* It would be nice to be able to free more memory here, eg. old
     tdata, but that's not possible since these blocks are sitting
     inside bfd_alloc'd memory.  The section hash is on a separate
     objalloc.  */
  bfd_hash_table_free (&preserve->section_htab);
  preserve->marker = NULL;
}

/*
FUNCTION
	bfd_check_format_matches

SYNOPSIS
	bfd_boolean bfd_check_format_matches
	  (bfd *abfd, bfd_format format, char ***matching);

DESCRIPTION
	Like <<bfd_check_format>>, except when it returns FALSE with
	<<bfd_errno>> set to <<bfd_error_file_ambiguously_recognized>>.  In that
	case, if @var{matching} is not NULL, it will be filled in with
	a NULL-terminated list of the names of the formats that matched,
	allocated with <<malloc>>.
	Then the user may choose a format and try again.

	When done with the list that @var{matching} points to, the caller
	should free it.
*/

bfd_boolean
bfd_check_format_matches (bfd *abfd, bfd_format format, char ***matching)
{
  extern const bfd_target binary_vec;
#if BFD_SUPPORTS_PLUGINS
  extern const bfd_target plugin_vec;
#endif
  const bfd_target * const *target;
  const bfd_target **matching_vector = NULL;
  const bfd_target *save_targ, *right_targ, *ar_right_targ, *match_targ;
  int match_count, best_count, best_match;
  int ar_match_index;
  struct bfd_preserve preserve;

  if (matching != NULL)
    *matching = NULL;

  if (!bfd_read_p (abfd)
      || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
    {
      bfd_set_error (bfd_error_invalid_operation);
      return FALSE;
    }

  if (abfd->format != bfd_unknown)
    return abfd->format == format;

  if (matching != NULL || *bfd_associated_vector != NULL)
    {
      bfd_size_type amt;

      amt = sizeof (*matching_vector) * 2 * _bfd_target_vector_entries;
      matching_vector = (const bfd_target **) bfd_malloc (amt);
      if (!matching_vector)
	return FALSE;
    }

  /* Presume the answer is yes.  */
  abfd->format = format;
  save_targ = abfd->xvec;
  preserve.marker = NULL;

  /* If the target type was explicitly specified, just check that target.  */
  if (!abfd->target_defaulted)
    {
      if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)	/* rewind! */
	goto err_ret;

      right_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));

      if (right_targ)
	goto ok_ret;

      /* For a long time the code has dropped through to check all
	 targets if the specified target was wrong.  I don't know why,
	 and I'm reluctant to change it.  However, in the case of an
	 archive, it can cause problems.  If the specified target does
	 not permit archives (e.g., the binary target), then we should
	 not allow some other target to recognize it as an archive, but
	 should instead allow the specified target to recognize it as an
	 object.  When I first made this change, it broke the PE target,
	 because the specified pei-i386 target did not recognize the
	 actual pe-i386 archive.  Since there may be other problems of
	 this sort, I changed this test to check only for the binary
	 target.  */
      if (format == bfd_archive && save_targ == &binary_vec)
	goto err_unrecog;
    }

  /* Since the target type was defaulted, check them all in the hope
     that one will be uniquely recognized.  */
  right_targ = NULL;
  ar_right_targ = NULL;
  match_targ = NULL;
  best_match = 256;
  best_count = 0;
  match_count = 0;
  ar_match_index = _bfd_target_vector_entries;

  for (target = bfd_target_vector; *target != NULL; target++)
    {
      const bfd_target *temp;

      /* Don't check the default target twice.  */
      if (*target == &binary_vec
	  || (!abfd->target_defaulted && *target == save_targ)
	  || (*target)->match_priority > best_match)
	continue;

      /* If we already tried a match, the bfd is modified and may
	 have sections attached, which will confuse the next
	 _bfd_check_format call.  */
      bfd_reinit (abfd);

      /* Change BFD's target temporarily.  */
      abfd->xvec = *target;

      if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
	goto err_ret;

      /* If _bfd_check_format neglects to set bfd_error, assume
	 bfd_error_wrong_format.  We didn't used to even pay any
	 attention to bfd_error, so I suspect that some
	 _bfd_check_format might have this problem.  */
      bfd_set_error (bfd_error_wrong_format);

      temp = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
      if (temp)
	{
	  int match_priority = temp->match_priority;
#if BFD_SUPPORTS_PLUGINS
	  /* If this object can be handled by a plugin, give that the
	     lowest priority; objects both handled by a plugin and
	     with an underlying object format will be claimed
	     separately by the plugin.  */
	  if (*target == &plugin_vec)
	    match_priority = (*target)->match_priority;
#endif

	  match_targ = temp;
	  if (preserve.marker != NULL)
	    bfd_preserve_finish (abfd, &preserve);

	  if (abfd->format != bfd_archive
	      || (bfd_has_map (abfd)
		  && bfd_get_error () != bfd_error_wrong_object_format))
	    {
	      /* This format checks out as ok!  */
	      right_targ = temp;

	      /* If this is the default target, accept it, even if
		 other targets might match.  People who want those
		 other targets have to set the GNUTARGET variable.  */
	      if (temp == bfd_default_vector[0])
		goto ok_ret;

	      if (matching_vector)
		matching_vector[match_count] = temp;
	      match_count++;

	      if (match_priority < best_match)
		{
		  best_match = match_priority;
		  best_count = 0;
		}
	      best_count++;
	    }
	  else
	    {
	      /* An archive with no armap or objects of the wrong
		 type.  We want this target to match if we get no
		 better matches.  */
	      if (ar_right_targ != bfd_default_vector[0])
		ar_right_targ = *target;
	      if (matching_vector)
		matching_vector[ar_match_index] = *target;
	      ar_match_index++;
	    }

	  if (!bfd_preserve_save (abfd, &preserve))
	    goto err_ret;
	}
      else if (bfd_get_error () != bfd_error_wrong_format)
	goto err_ret;
    }

  if (best_count == 1)
    match_count = 1;

  if (match_count == 0)
    {
      /* Try partial matches.  */
      right_targ = ar_right_targ;

      if (right_targ == bfd_default_vector[0])
	{
	  match_count = 1;
	}
      else
	{
	  match_count = ar_match_index - _bfd_target_vector_entries;

	  if (matching_vector && match_count > 1)
	    memcpy (matching_vector,
		    matching_vector + _bfd_target_vector_entries,
		    sizeof (*matching_vector) * match_count);
	}
    }

  /* We have more than one equally good match.  If any of the best
     matches is a target in config.bfd targ_defvec or targ_selvecs,
     choose it.  */
  if (match_count > 1)
    {
      const bfd_target * const *assoc = bfd_associated_vector;

      while ((right_targ = *assoc++) != NULL)
	{
	  int i = match_count;

	  while (--i >= 0)
	    if (matching_vector[i] == right_targ
		&& right_targ->match_priority <= best_match)
	      break;

	  if (i >= 0)
	    {
	      match_count = 1;
	      break;
	    }
	}
    }

  /* We still have more than one equally good match, and at least some
     of the targets support match priority.  Choose the first of the
     best matches.  */
  if (matching_vector && match_count > 1 && best_count != match_count)
    {
      int i;

      for (i = 0; i < match_count; i++)
	{
	  right_targ = matching_vector[i];
	  if (right_targ->match_priority <= best_match)
	    break;
	}
      match_count = 1;
    }

  /* There is way too much undoing of half-known state here.  We
     really shouldn't iterate on live bfd's.  Note that saving the
     whole bfd and restoring it would be even worse; the first thing
     you notice is that the cached bfd file position gets out of sync.  */
  if (preserve.marker != NULL)
    bfd_preserve_restore (abfd, &preserve);

  if (match_count == 1)
    {
      abfd->xvec = right_targ;
      /* If we come out of the loop knowing that the last target that
	 matched is the one we want, then ABFD should still be in a usable
	 state (except possibly for XVEC).  */
      if (match_targ != right_targ)
	{
	  bfd_reinit (abfd);
	  if (bfd_seek (abfd, (file_ptr) 0, SEEK_SET) != 0)
	    goto err_ret;
	  match_targ = BFD_SEND_FMT (abfd, _bfd_check_format, (abfd));
	  BFD_ASSERT (match_targ != NULL);
	}

    ok_ret:
      /* If the file was opened for update, then `output_has_begun'
	 some time ago when the file was created.  Do not recompute
	 sections sizes or alignments in _bfd_set_section_contents.
	 We can not set this flag until after checking the format,
	 because it will interfere with creation of BFD sections.  */
      if (abfd->direction == both_direction)
	abfd->output_has_begun = TRUE;

      if (matching_vector)
	free (matching_vector);

      /* File position has moved, BTW.  */
      return TRUE;
    }

  if (match_count == 0)
    {
    err_unrecog:
      bfd_set_error (bfd_error_file_not_recognized);
    err_ret:
      abfd->xvec = save_targ;
      abfd->format = bfd_unknown;
      if (matching_vector)
	free (matching_vector);
      if (preserve.marker != NULL)
	bfd_preserve_restore (abfd, &preserve);
      return FALSE;
    }

  /* Restore original target type and format.  */
  abfd->xvec = save_targ;
  abfd->format = bfd_unknown;
  bfd_set_error (bfd_error_file_ambiguously_recognized);

  if (matching)
    {
      *matching = (char **) matching_vector;
      matching_vector[match_count] = NULL;
      /* Return target names.  This is a little nasty.  Maybe we
	 should do another bfd_malloc?  */
      while (--match_count >= 0)
	{
	  const char *name = matching_vector[match_count]->name;
	  *(const char **) &matching_vector[match_count] = name;
	}
    }
  return FALSE;
}

/*
FUNCTION
	bfd_set_format

SYNOPSIS
	bfd_boolean bfd_set_format (bfd *abfd, bfd_format format);

DESCRIPTION
	This function sets the file format of the BFD @var{abfd} to the
	format @var{format}. If the target set in the BFD does not
	support the format requested, the format is invalid, or the BFD
	is not open for writing, then an error occurs.
*/

bfd_boolean
bfd_set_format (bfd *abfd, bfd_format format)
{
  if (bfd_read_p (abfd)
      || (unsigned int) abfd->format >= (unsigned int) bfd_type_end)
    {
      bfd_set_error (bfd_error_invalid_operation);
      return FALSE;
    }

  if (abfd->format != bfd_unknown)
    return abfd->format == format;

  /* Presume the answer is yes.  */
  abfd->format = format;

  if (!BFD_SEND_FMT (abfd, _bfd_set_format, (abfd)))
    {
      abfd->format = bfd_unknown;
      return FALSE;
    }

  return TRUE;
}

/*
FUNCTION
	bfd_format_string

SYNOPSIS
	const char *bfd_format_string (bfd_format format);

DESCRIPTION
	Return a pointer to a const string
	<<invalid>>, <<object>>, <<archive>>, <<core>>, or <<unknown>>,
	depending upon the value of @var{format}.
*/

const char *
bfd_format_string (bfd_format format)
{
  if (((int) format < (int) bfd_unknown)
      || ((int) format >= (int) bfd_type_end))
    return "invalid";

  switch (format)
    {
    case bfd_object:
      return "object";		/* Linker/assembler/compiler output.  */
    case bfd_archive:
      return "archive";		/* Object archive file.  */
    case bfd_core:
      return "core";		/* Core dump.  */
    default:
      return "unknown";
    }
}