about summary refs log tree commit diff
path: root/elf/dl-deps.c
blob: e79e8f1b7b255d2bf667233441374239c82a5566 (plain) (blame)
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
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
/* Load the dependencies of a mapped object.
   Copyright (C) 1996-2001, 2002 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <assert.h>
#include <dlfcn.h>
#include <errno.h>
#include <libintl.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <ldsodefs.h>

#include <dl-dst.h>

/* Whether an shared object references one or more auxiliary objects
   is signaled by the AUXTAG entry in l_info.  */
#define AUXTAG	(DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM \
		 + DT_EXTRATAGIDX (DT_AUXILIARY))
/* Whether an shared object references one or more auxiliary objects
   is signaled by the AUXTAG entry in l_info.  */
#define FILTERTAG (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGNUM \
		   + DT_EXTRATAGIDX (DT_FILTER))


/* When loading auxiliary objects we must ignore errors.  It's ok if
   an object is missing.  */
struct openaux_args
  {
    /* The arguments to openaux.  */
    struct link_map *map;
    int trace_mode;
    int open_mode;
    const char *strtab;
    const char *name;

    /* The return value of openaux.  */
    struct link_map *aux;
  };

static void
openaux (void *a)
{
  struct openaux_args *args = (struct openaux_args *) a;

  args->aux = INTUSE(_dl_map_object) (args->map, args->name, 0,
				      (args->map->l_type == lt_executable
				       ? lt_library : args->map->l_type),
				      args->trace_mode, args->open_mode);
}

static ptrdiff_t
internal_function
_dl_build_local_scope (struct link_map **list, struct link_map *map)
{
  struct link_map **p = list;
  struct link_map **q;

  *p++ = map;
  map->l_reserved = 1;
  if (map->l_initfini)
    for (q = map->l_initfini + 1; *q; ++q)
      if (! (*q)->l_reserved)
	p += _dl_build_local_scope (p, *q);
  return p - list;
}


/* We use a very special kind of list to track the path
   through the list of loaded shared objects.  We have to
   produce a flat list with unique members of all involved objects.
*/
struct list
  {
    int done;			/* Nonzero if this map was processed.  */
    struct link_map *map;	/* The data.  */
    struct list *next;	/* Elements for normal list.  */
  };


/* Macro to expand DST.  It is an macro since we use `alloca'.  */
#define expand_dst(l, str, fatal) \
  ({									      \
    const char *__str = (str);						      \
    const char *__result = __str;					      \
    size_t __cnt = DL_DST_COUNT(__str, 0);				      \
									      \
    if (__cnt != 0)							      \
      {									      \
	char *__newp;							      \
									      \
	/* DST must not appear in SUID/SGID programs.  */		      \
	if (__libc_enable_secure)					      \
	  INTUSE(_dl_signal_error) (0, __str, NULL, N_("\
DST not allowed in SUID/SGID programs"));				      \
									      \
	__newp = (char *) alloca (DL_DST_REQUIRED (l, __str, strlen (__str),  \
						   __cnt));		      \
									      \
	__result = INTUSE(_dl_dst_substitute) (l, __str, __newp, 0);	      \
									      \
	if (*__result == '\0')						      \
	  {								      \
	    /* The replacement for the DST is not known.  We can't	      \
	       processed.  */						      \
	    if (fatal)							      \
	      INTUSE(_dl_signal_error) (0, __str, NULL, N_("\
empty dynamics string token substitution"));				      \
	    else							      \
	      {								      \
		/* This is for DT_AUXILIARY.  */			      \
		if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_LIBS, 0))  \
		  INTUSE(_dl_debug_printf) (N_("\
cannot load auxiliary `%s' because of empty dynamic string token "	      \
					    "substitution\n"), __str);	      \
		continue;						      \
	      }								      \
	  }								      \
      }									      \
									      \
    __result; })


void
internal_function
_dl_map_object_deps (struct link_map *map,
		     struct link_map **preloads, unsigned int npreloads,
		     int trace_mode, int open_mode)
{
  struct list known[1 + npreloads + 1];
  struct list *runp, *tail;
  unsigned int nlist, i;
  /* Object name.  */
  const char *name;
  int errno_saved;
  int errno_reason;
  const char *errstring;
  const char *objname;

  auto inline void preload (struct link_map *map);

  inline void preload (struct link_map *map)
    {
      known[nlist].done = 0;
      known[nlist].map = map;
      known[nlist].next = &known[nlist + 1];

      ++nlist;
      /* We use `l_reserved' as a mark bit to detect objects we have
	 already put in the search list and avoid adding duplicate
	 elements later in the list.  */
      map->l_reserved = 1;
    }

  /* No loaded object so far.  */
  nlist = 0;

  /* First load MAP itself.  */
  preload (map);

  /* Add the preloaded items after MAP but before any of its dependencies.  */
  for (i = 0; i < npreloads; ++i)
    preload (preloads[i]);

  /* Terminate the lists.  */
  known[nlist - 1].next = NULL;

  /* Pointer to last unique object.  */
  tail = &known[nlist - 1];

  /* Process each element of the search list, loading each of its
     auxiliary objects and immediate dependencies.  Auxiliary objects
     will be added in the list before the object itself and
     dependencies will be appended to the list as we step through it.
     This produces a flat, ordered list that represents a
     breadth-first search of the dependency tree.

     The whole process is complicated by the fact that we better
     should use alloca for the temporary list elements.  But using
     alloca means we cannot use recursive function calls.  */
  errno_saved = errno;
  errno_reason = 0;
  errstring = NULL;
  errno = 0;
  name = NULL;
  for (runp = known; runp; )
    {
      struct link_map *l = runp->map;
      struct link_map **needed = NULL;
      unsigned int nneeded = 0;

      /* Unless otherwise stated, this object is handled.  */
      runp->done = 1;

      /* Allocate a temporary record to contain the references to the
	 dependencies of this object.  */
      if (l->l_searchlist.r_list == NULL && l->l_initfini == NULL
	  && l != map && l->l_ldnum > 0)
	needed = (struct link_map **) alloca (l->l_ldnum
					      * sizeof (struct link_map *));

      if (l->l_info[DT_NEEDED] || l->l_info[AUXTAG] || l->l_info[FILTERTAG])
	{
	  const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
	  struct openaux_args args;
	  struct list *orig;
	  const ElfW(Dyn) *d;

	  args.strtab = strtab;
	  args.map = l;
	  args.trace_mode = trace_mode;
	  args.open_mode = open_mode;
	  orig = runp;

	  for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
	    if (__builtin_expect (d->d_tag, DT_NEEDED) == DT_NEEDED)
	      {
		/* Map in the needed object.  */
		struct link_map *dep;
		int err;

		/* Recognize DSTs.  */
		name = expand_dst (l, strtab + d->d_un.d_val, 0);
		/* Store the tag in the argument structure.  */
		args.name = name;

		err = INTUSE(_dl_catch_error) (&objname, &errstring, openaux,
					       &args);
		if (__builtin_expect (errstring != NULL, 0))
		  {
		    if (err)
		      errno_reason = err;
		    else
		      errno_reason = -1;
		    goto out;
		  }
		else
		  dep = args.aux;

		if (! dep->l_reserved)
		  {
		    /* Allocate new entry.  */
		    struct list *newp;

		    newp = alloca (sizeof (struct list));

		    /* Append DEP to the list.  */
		    newp->map = dep;
		    newp->done = 0;
		    newp->next = NULL;
		    tail->next = newp;
		    tail = newp;
		    ++nlist;
		    /* Set the mark bit that says it's already in the list.  */
		    dep->l_reserved = 1;
		  }

		/* Remember this dependency.  */
		if (needed != NULL)
		  needed[nneeded++] = dep;
	      }
	    else if (d->d_tag == DT_AUXILIARY || d->d_tag == DT_FILTER)
	      {
		struct list *newp;

		/* Recognize DSTs.  */
		name = expand_dst (l, strtab + d->d_un.d_val,
				   d->d_tag == DT_AUXILIARY);
		/* Store the tag in the argument structure.  */
		args.name = name;

		if (d->d_tag == DT_AUXILIARY)
		  {
		    int err;

		    /* Say that we are about to load an auxiliary library.  */
		    if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_LIBS,
					  0))
		      INTUSE(_dl_debug_printf) ("load auxiliary object=%s"
						" requested by file=%s\n",
						name,
						l->l_name[0]
						? l->l_name : _dl_argv[0]);

		    /* We must be prepared that the addressed shared
		       object is not available.  */
		    err = INTUSE(_dl_catch_error) (&objname, &errstring,
						   openaux, &args);
		    if (__builtin_expect (errstring != NULL, 0))
		      {
			/* We are not interested in the error message.  */
			assert (errstring != NULL);
			if (errstring != _dl_out_of_memory)
			  free ((char *) errstring);

			/* Simply ignore this error and continue the work.  */
			continue;
		      }
		  }
		else
		  {
		    int err;

		    /* Say that we are about to load an auxiliary library.  */
		    if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_LIBS,
					  0))
		      INTUSE(_dl_debug_printf) ("load filtered object=%s"
						" requested by file=%s\n",
						name,
						l->l_name[0]
						? l->l_name : _dl_argv[0]);

		    /* For filter objects the dependency must be available.  */
		    err = INTUSE(_dl_catch_error) (&objname, &errstring,
						   openaux, &args);
		    if (__builtin_expect (errstring != NULL, 0))
		      {
			if (err)
			  errno_reason = err;
			else
			  errno_reason = -1;
			goto out;
		      }
		  }

		/* The auxiliary object is actually available.
		   Incorporate the map in all the lists.  */

		/* Allocate new entry.  This always has to be done.  */
		newp = alloca (sizeof (struct list));

		/* We want to insert the new map before the current one,
		   but we have no back links.  So we copy the contents of
		   the current entry over.  Note that ORIG and NEWP now
		   have switched their meanings.  */
		memcpy (newp, orig, sizeof (*newp));

		/* Initialize new entry.  */
		orig->done = 0;
		orig->map = args.aux;

		/* Remember this dependency.  */
		if (needed != NULL)
		  needed[nneeded++] = args.aux;

		/* We must handle two situations here: the map is new,
		   so we must add it in all three lists.  If the map
		   is already known, we have two further possibilities:
		   - if the object is before the current map in the
		   search list, we do nothing.  It is already found
		   early
		   - if the object is after the current one, we must
		   move it just before the current map to make sure
		   the symbols are found early enough
		*/
		if (args.aux->l_reserved)
		  {
		    /* The object is already somewhere in the list.
		       Locate it first.  */
		    struct list *late;

		    /* This object is already in the search list we
		       are building.  Don't add a duplicate pointer.
		       Just added by _dl_map_object.  */
		    for (late = newp; late->next != NULL; late = late->next)
		      if (late->next->map == args.aux)
			break;

		    if (late->next != NULL)
		      {
			/* The object is somewhere behind the current
			   position in the search path.  We have to
			   move it to this earlier position.  */
			orig->next = newp;

			/* Now remove the later entry from the list
			   and adjust the tail pointer.  */
			if (tail == late->next)
			  tail = late;
			late->next = late->next->next;

			/* We must move the object earlier in the chain.  */
			if (args.aux->l_prev != NULL)
			  args.aux->l_prev->l_next = args.aux->l_next;
			if (args.aux->l_next != NULL)
			  args.aux->l_next->l_prev = args.aux->l_prev;

			args.aux->l_prev = newp->map->l_prev;
			newp->map->l_prev = args.aux;
			if (args.aux->l_prev != NULL)
			  args.aux->l_prev->l_next = args.aux;
			args.aux->l_next = newp->map;
		      }
		    else
		      {
			/* The object must be somewhere earlier in the
			   list.  Undo to the current list element what
			   we did above.  */
			memcpy (orig, newp, sizeof (*newp));
			continue;
		      }
		  }
		else
		  {
		    /* This is easy.  We just add the symbol right here.  */
		    orig->next = newp;
		    ++nlist;
		    /* Set the mark bit that says it's already in the list.  */
		    args.aux->l_reserved = 1;

		    /* The only problem is that in the double linked
		       list of all objects we don't have this new
		       object at the correct place.  Correct this here.  */
		    if (args.aux->l_prev)
		      args.aux->l_prev->l_next = args.aux->l_next;
		    if (args.aux->l_next)
		      args.aux->l_next->l_prev = args.aux->l_prev;

		    args.aux->l_prev = newp->map->l_prev;
		    newp->map->l_prev = args.aux;
		    if (args.aux->l_prev != NULL)
		      args.aux->l_prev->l_next = args.aux;
		    args.aux->l_next = newp->map;
		  }

		/* Move the tail pointer if necessary.  */
		if (orig == tail)
		  tail = newp;

		/* Move on the insert point.  */
		orig = newp;
	      }
	}

      /* Terminate the list of dependencies and store the array address.  */
      if (needed != NULL)
	{
	  needed[nneeded++] = NULL;

	  l->l_initfini = (struct link_map **)
	    malloc ((nneeded + 1) * sizeof needed[0]);
	  if (l->l_initfini == NULL)
	    INTUSE(_dl_signal_error) (ENOMEM, map->l_name, NULL,
				      N_("cannot allocate dependency list"));
	  l->l_initfini[0] = l;
	  memcpy (&l->l_initfini[1], needed, nneeded * sizeof needed[0]);
	}

      /* If we have no auxiliary objects just go on to the next map.  */
      if (runp->done)
	do
	  runp = runp->next;
	while (runp != NULL && runp->done);
    }

 out:
  if (errno == 0 && errno_saved != 0)
    __set_errno (errno_saved);

  if (map->l_initfini != NULL && map->l_type == lt_loaded)
    {
      /* This object was previously loaded as a dependency and we have
	 a separate l_initfini list.  We don't need it anymore.  */
      assert (map->l_searchlist.r_list == NULL);
      free (map->l_initfini);
    }

  /* Store the search list we built in the object.  It will be used for
     searches in the scope of this object.  */
  map->l_initfini =
    (struct link_map **) malloc ((2 * nlist + 1)
				 * sizeof (struct link_map *));
  if (map->l_initfini == NULL)
    INTUSE(_dl_signal_error) (ENOMEM, map->l_name, NULL,
			      N_("cannot allocate symbol search list"));


  map->l_searchlist.r_list = &map->l_initfini[nlist + 1];
  map->l_searchlist.r_nlist = nlist;

  for (nlist = 0, runp = known; runp; runp = runp->next)
    {
      if (__builtin_expect (trace_mode, 0) && runp->map->l_faked)
	/* This can happen when we trace the loading.  */
	--map->l_searchlist.r_nlist;
      else
	map->l_searchlist.r_list[nlist++] = runp->map;

      /* Now clear all the mark bits we set in the objects on the search list
	 to avoid duplicates, so the next call starts fresh.  */
      runp->map->l_reserved = 0;
    }

  if (__builtin_expect(GL(dl_debug_mask) & DL_DEBUG_PRELINK, 0) != 0
      && map == GL(dl_loaded))
    {
      /* If we are to compute conflicts, we have to build local scope
	 for each library, not just the ultimate loader.  */
      for (i = 0; i < nlist; ++i)
	{
	  struct link_map *l = map->l_searchlist.r_list[i];
	  unsigned int j, cnt;

	  /* The local scope has been already computed.  */
	  if (l == map
	      || (l->l_local_scope[0]
		  && l->l_local_scope[0]->r_nlist) != 0)
	    continue;

	  if (l->l_info[AUXTAG] || l->l_info[FILTERTAG])
	    {
	      /* As current DT_AUXILIARY/DT_FILTER implementation needs to be
		 rewritten, no need to bother with prelinking the old
		 implementation.  */
	      INTUSE(_dl_signal_error) (EINVAL, l->l_name, NULL, N_("\
Filters not supported with LD_TRACE_PRELINKING"));
	    }

	  cnt = _dl_build_local_scope (map->l_initfini, l);
	  assert (cnt <= nlist);
	  for (j = 0; j < cnt; j++)
	    map->l_initfini[j]->l_reserved = 0;

	  l->l_local_scope[0] =
	    (struct r_scope_elem *) malloc (sizeof (struct r_scope_elem)
					    + (cnt
					       * sizeof (struct link_map *)));
	  if (l->l_local_scope[0] == NULL)
	    INTUSE(_dl_signal_error) (ENOMEM, map->l_name, NULL,
				      N_("cannot allocate symbol search list"));
	  l->l_local_scope[0]->r_nlist = cnt;
	  l->l_local_scope[0]->r_list =
	    (struct link_map **) (l->l_local_scope[0] + 1);
	  memcpy (l->l_local_scope[0]->r_list, map->l_initfini,
		  cnt * sizeof (struct link_map *));
	}
    }

  /* Maybe we can remove some relocation dependencies now.  */
  assert (map->l_searchlist.r_list[0] == map);
  for (i = 0; i < map->l_reldepsact; ++i)
    {
      unsigned int j;

      for (j = 1; j < nlist; ++j)
	if (map->l_searchlist.r_list[j] == map->l_reldeps[i])
	  {
	    /* A direct or transitive dependency is also on the list
	       of relocation dependencies.  Remove the latter.  */
	    --map->l_reldeps[i]->l_opencount;

	    for (j = i + 1; j < map->l_reldepsact; ++j)
	      map->l_reldeps[j - 1] = map->l_reldeps[j];

	    --map->l_reldepsact;

	    /* Account for the '++i' performed by the 'for'.  */
	    --i;
	    break;
	  }
    }

  /* Now determine the order in which the initialization has to happen.  */
  memcpy (map->l_initfini, map->l_searchlist.r_list,
	  nlist * sizeof (struct link_map *));
  /* We can skip looking for the binary itself which is at the front
     of the search list.  Look through the list backward so that circular
     dependencies are not changing the order.  */
  for (i = 1; i < nlist; ++i)
    {
      struct link_map *l = map->l_searchlist.r_list[i];
      unsigned int j;
      unsigned int k;

      /* Find the place in the initfini list where the map is currently
	 located.  */
      for (j = 1; map->l_initfini[j] != l; ++j)
	;

      /* Find all object for which the current one is a dependency and
	 move the found object (if necessary) in front.  */
      for (k = j + 1; k < nlist; ++k)
	{
	  struct link_map **runp;

	  runp = map->l_initfini[k]->l_initfini;
	  if (runp != NULL)
	    {
	      while (*runp != NULL)
		if (__builtin_expect (*runp++ == l, 0))
		  {
		    struct link_map *here = map->l_initfini[k];

		    /* Move it now.  */
		    memmove (&map->l_initfini[j] + 1,
			     &map->l_initfini[j],
			     (k - j) * sizeof (struct link_map *));
		    map->l_initfini[j] = here;

		    break;
		  }
	    }
	}
    }
  /* Terminate the list of dependencies.  */
  map->l_initfini[nlist] = NULL;

  if (errno_reason)
    INTUSE(_dl_signal_error) (errno_reason == -1 ? 0 : errno_reason, objname,
			   NULL, errstring);
}
INTDEF (_dl_map_object_deps)