summary refs log tree commit diff
path: root/sysdeps/generic/unwind-dw2-fde.c
blob: 80bcf613707fc52263c2739b96febb4f4e3d5fd8 (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
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
/* Subroutines needed for unwinding stack frames for exception handling.  */
/* Copyright (C) 1997-2018 Free Software Foundation, Inc.
   Contributed by Jason Merrill <jason@cygnus.com>.

   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, see
   <http://www.gnu.org/licenses/>.  */

#ifdef _LIBC
# include <shlib-compat.h>
#endif

#if !defined _LIBC || SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_2_5)

#ifdef _LIBC
#include <stdlib.h>
#include <string.h>
#include <libc-lock.h>
#include <dwarf2.h>
#include <unwind.h>
#define NO_BASE_OF_ENCODED_VALUE
#include <unwind-pe.h>
#include <unwind-dw2-fde.h>
#else
#ifndef _Unwind_Find_FDE
#include "tconfig.h"
#include "tsystem.h"
#include "dwarf2.h"
#include "unwind.h"
#define NO_BASE_OF_ENCODED_VALUE
#include "unwind-pe.h"
#include "unwind-dw2-fde.h"
#include "gthr.h"
#endif
#endif

/* The unseen_objects list contains objects that have been registered
   but not yet categorized in any way.  The seen_objects list has had
   it's pc_begin and count fields initialized at minimum, and is sorted
   by decreasing value of pc_begin.  */
static struct object *unseen_objects;
static struct object *seen_objects;

#ifdef _LIBC

__libc_lock_define_initialized (static, object_mutex)
#define init_object_mutex_once()
#define __gthread_mutex_lock(m) __libc_lock_lock (*(m))
#define __gthread_mutex_unlock(m) __libc_lock_unlock (*(m))

void __register_frame_info_bases (void *begin, struct object *ob,
				  void *tbase, void *dbase);
hidden_proto (__register_frame_info_bases)
void __register_frame_info_table_bases (void *begin,
					struct object *ob,
					void *tbase, void *dbase);
hidden_proto (__register_frame_info_table_bases)
void *__deregister_frame_info_bases (void *begin);
hidden_proto (__deregister_frame_info_bases)

#else

#ifdef __GTHREAD_MUTEX_INIT
static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT;
#else
static __gthread_mutex_t object_mutex;
#endif

#ifdef __GTHREAD_MUTEX_INIT_FUNCTION
static void
init_object_mutex (void)
{
  __GTHREAD_MUTEX_INIT_FUNCTION (&object_mutex);
}

static void
init_object_mutex_once (void)
{
  static __gthread_once_t once = __GTHREAD_ONCE_INIT;
  __gthread_once (&once, init_object_mutex);
}
#else
#define init_object_mutex_once()
#endif

#endif /* _LIBC */

/* Called from crtbegin.o to register the unwind info for an object.  */

void
__register_frame_info_bases (void *begin, struct object *ob,
			     void *tbase, void *dbase)
{
  /* If .eh_frame is empty, don't register at all.  */
  if (*(uword *) begin == 0)
    return;

  ob->pc_begin = (void *)-1;
  ob->tbase = tbase;
  ob->dbase = dbase;
  ob->u.single = begin;
  ob->s.i = 0;
  ob->s.b.encoding = DW_EH_PE_omit;
#ifdef DWARF2_OBJECT_END_PTR_EXTENSION
  ob->fde_end = NULL;
#endif

  init_object_mutex_once ();
  __gthread_mutex_lock (&object_mutex);

  ob->next = unseen_objects;
  unseen_objects = ob;

  __gthread_mutex_unlock (&object_mutex);
}
hidden_def (__register_frame_info_bases)

void
__register_frame_info (void *begin, struct object *ob)
{
  __register_frame_info_bases (begin, ob, 0, 0);
}

void
__register_frame (void *begin)
{
  struct object *ob;

  /* If .eh_frame is empty, don't register at all.  */
  if (*(uword *) begin == 0)
    return;

  ob = (struct object *) malloc (sizeof (struct object));
  __register_frame_info_bases (begin, ob, 0, 0);
}

/* Similar, but BEGIN is actually a pointer to a table of unwind entries
   for different translation units.  Called from the file generated by
   collect2.  */

void
__register_frame_info_table_bases (void *begin, struct object *ob,
				   void *tbase, void *dbase)
{
  ob->pc_begin = (void *)-1;
  ob->tbase = tbase;
  ob->dbase = dbase;
  ob->u.array = begin;
  ob->s.i = 0;
  ob->s.b.from_array = 1;
  ob->s.b.encoding = DW_EH_PE_omit;

  init_object_mutex_once ();
  __gthread_mutex_lock (&object_mutex);

  ob->next = unseen_objects;
  unseen_objects = ob;

  __gthread_mutex_unlock (&object_mutex);
}
hidden_def (__register_frame_info_table_bases)

void
__register_frame_info_table (void *begin, struct object *ob)
{
  __register_frame_info_table_bases (begin, ob, 0, 0);
}

void
__register_frame_table (void *begin)
{
  struct object *ob = (struct object *) malloc (sizeof (struct object));
  __register_frame_info_table_bases (begin, ob, 0, 0);
}

/* Called from crtbegin.o to deregister the unwind info for an object.  */
/* ??? Glibc has for a while now exported __register_frame_info and
   __deregister_frame_info.  If we call __register_frame_info_bases
   from crtbegin (wherein it is declared weak), and this object does
   not get pulled from libgcc.a for other reasons, then the
   invocation of __deregister_frame_info will be resolved from glibc.
   Since the registration did not happen there, we'll abort.

   Therefore, declare a new deregistration entry point that does the
   exact same thing, but will resolve to the same library as
   implements __register_frame_info_bases.  */

void *
__deregister_frame_info_bases (void *begin)
{
  struct object **p;
  struct object *ob = 0;
  struct fde_vector *tofree = NULL;

  /* If .eh_frame is empty, we haven't registered.  */
  if (*(uword *) begin == 0)
    return ob;

  init_object_mutex_once ();
  __gthread_mutex_lock (&object_mutex);

  for (p = &unseen_objects; *p ; p = &(*p)->next)
    if ((*p)->u.single == begin)
      {
	ob = *p;
	*p = ob->next;
	goto out;
      }

  for (p = &seen_objects; *p ; p = &(*p)->next)
    if ((*p)->s.b.sorted)
      {
	if ((*p)->u.sort->orig_data == begin)
	  {
	    ob = *p;
	    *p = ob->next;
	    tofree = ob->u.sort;
	    goto out;
	  }
      }
    else
      {
	if ((*p)->u.single == begin)
	  {
	    ob = *p;
	    *p = ob->next;
	    goto out;
	  }
      }

  __gthread_mutex_unlock (&object_mutex);
  abort ();

 out:
  __gthread_mutex_unlock (&object_mutex);
  free (tofree);
  return (void *) ob;
}
hidden_def (__deregister_frame_info_bases)

void *
__deregister_frame_info (void *begin)
{
  return __deregister_frame_info_bases (begin);
}

void
__deregister_frame (void *begin)
{
  /* If .eh_frame is empty, we haven't registered.  */
  if (*(uword *) begin != 0)
    free (__deregister_frame_info_bases (begin));
}


/* Like base_of_encoded_value, but take the base from a struct object
   instead of an _Unwind_Context.  */

static _Unwind_Ptr
base_from_object (unsigned char encoding, struct object *ob)
{
  if (encoding == DW_EH_PE_omit)
    return 0;

  switch (encoding & 0x70)
    {
    case DW_EH_PE_absptr:
    case DW_EH_PE_pcrel:
    case DW_EH_PE_aligned:
      return 0;

    case DW_EH_PE_textrel:
      return (_Unwind_Ptr) ob->tbase;
    case DW_EH_PE_datarel:
      return (_Unwind_Ptr) ob->dbase;
    }
  abort ();
}

/* Return the FDE pointer encoding from the CIE.  */
/* ??? This is a subset of extract_cie_info from unwind-dw2.c.  */

static int
get_cie_encoding (struct dwarf_cie *cie)
{
  const unsigned char *aug, *p;
  _Unwind_Ptr dummy;
  _Unwind_Word utmp;
  _Unwind_Sword stmp;

  aug = cie->augmentation;
  if (aug[0] != 'z')
    return DW_EH_PE_absptr;

  /* Skip the augmentation string.  */
  p = aug + strlen ((const char *) aug) + 1;
  p = read_uleb128 (p, &utmp);		/* Skip code alignment.  */
  p = read_sleb128 (p, &stmp);		/* Skip data alignment.  */
  p++;					/* Skip return address column.  */

  aug++;				/* Skip 'z' */
  p = read_uleb128 (p, &utmp);		/* Skip augmentation length.  */
  while (1)
    {
      /* This is what we're looking for.  */
      if (*aug == 'R')
	return *p;
      /* Personality encoding and pointer.  */
      else if (*aug == 'P')
	{
	  /* ??? Avoid dereferencing indirect pointers, since we're
	     faking the base address.  Gotta keep DW_EH_PE_aligned
	     intact, however.  */
	  p = read_encoded_value_with_base (*p & 0x7F, 0, p + 1, &dummy);
	}
      /* LSDA encoding.  */
      else if (*aug == 'L')
	p++;
      /* Otherwise end of string, or unknown augmentation.  */
      else
	return DW_EH_PE_absptr;
      aug++;
    }
}

static inline int
get_fde_encoding (struct dwarf_fde *f)
{
  return get_cie_encoding (get_cie (f));
}


/* Sorting an array of FDEs by address.
   (Ideally we would have the linker sort the FDEs so we don't have to do
   it at run time. But the linkers are not yet prepared for this.)  */

/* Return the Nth pc_begin value from FDE x.  */

static inline _Unwind_Ptr
get_pc_begin (fde *x, size_t n)
{
  _Unwind_Ptr p;
  memcpy (&p, x->pc_begin + n * sizeof (_Unwind_Ptr), sizeof (_Unwind_Ptr));
  return p;
}

/* Comparison routines.  Three variants of increasing complexity.  */

static int
fde_unencoded_compare (struct object *ob __attribute__((unused)),
		       fde *x, fde *y)
{
  _Unwind_Ptr x_ptr = get_pc_begin (x, 0);
  _Unwind_Ptr y_ptr = get_pc_begin (y, 0);

  if (x_ptr > y_ptr)
    return 1;
  if (x_ptr < y_ptr)
    return -1;
  return 0;
}

static int
fde_single_encoding_compare (struct object *ob, fde *x, fde *y)
{
  _Unwind_Ptr base, x_ptr, y_ptr;

  base = base_from_object (ob->s.b.encoding, ob);
  read_encoded_value_with_base (ob->s.b.encoding, base, x->pc_begin, &x_ptr);
  read_encoded_value_with_base (ob->s.b.encoding, base, y->pc_begin, &y_ptr);

  if (x_ptr > y_ptr)
    return 1;
  if (x_ptr < y_ptr)
    return -1;
  return 0;
}

static int
fde_mixed_encoding_compare (struct object *ob, fde *x, fde *y)
{
  int x_encoding, y_encoding;
  _Unwind_Ptr x_ptr, y_ptr;

  x_encoding = get_fde_encoding (x);
  read_encoded_value_with_base (x_encoding, base_from_object (x_encoding, ob),
				x->pc_begin, &x_ptr);

  y_encoding = get_fde_encoding (y);
  read_encoded_value_with_base (y_encoding, base_from_object (y_encoding, ob),
				y->pc_begin, &y_ptr);

  if (x_ptr > y_ptr)
    return 1;
  if (x_ptr < y_ptr)
    return -1;
  return 0;
}

typedef int (*fde_compare_t) (struct object *, fde *, fde *);


/* This is a special mix of insertion sort and heap sort, optimized for
   the data sets that actually occur. They look like
   101 102 103 127 128 105 108 110 190 111 115 119 125 160 126 129 130.
   I.e. a linearly increasing sequence (coming from functions in the text
   section), with additionally a few unordered elements (coming from functions
   in gnu_linkonce sections) whose values are higher than the values in the
   surrounding linear sequence (but not necessarily higher than the values
   at the end of the linear sequence!).
   The worst-case total run time is O(N) + O(n log (n)), where N is the
   total number of FDEs and n is the number of erratic ones.  */

struct fde_accumulator
{
  struct fde_vector *linear;
  struct fde_vector *erratic;
};

static int
start_fde_sort (struct fde_accumulator *accu, size_t count)
{
  size_t size;
  if (! count)
    return 0;

  size = sizeof (struct fde_vector) + sizeof (fde *) * count;
  if ((accu->linear = (struct fde_vector *) malloc (size)))
    {
      accu->linear->count = 0;
      if ((accu->erratic = (struct fde_vector *) malloc (size)))
	accu->erratic->count = 0;
      return 1;
    }
  else
    return 0;
}

static inline void
fde_insert (struct fde_accumulator *accu, fde *this_fde)
{
  if (accu->linear)
    accu->linear->array[accu->linear->count++] = this_fde;
}

/* Split LINEAR into a linear sequence with low values and an erratic
   sequence with high values, put the linear one (of longest possible
   length) into LINEAR and the erratic one into ERRATIC. This is O(N).

   Because the longest linear sequence we are trying to locate within the
   incoming LINEAR array can be interspersed with (high valued) erratic
   entries.  We construct a chain indicating the sequenced entries.
   To avoid having to allocate this chain, we overlay it onto the space of
   the ERRATIC array during construction.  A final pass iterates over the
   chain to determine what should be placed in the ERRATIC array, and
   what is the linear sequence.  This overlay is safe from aliasing.  */

static void
fde_split (struct object *ob, fde_compare_t fde_compare,
	   struct fde_vector *linear, struct fde_vector *erratic)
{
  static fde *marker;
  size_t count = linear->count;
  fde **chain_end = &marker;
  size_t i, j, k;

  /* This should optimize out, but it is wise to make sure this assumption
     is correct. Should these have different sizes, we cannot cast between
     them and the overlaying onto ERRATIC will not work.  */
  if (sizeof (fde *) != sizeof (fde **))
    abort ();

  for (i = 0; i < count; i++)
    {
      fde **probe;

      for (probe = chain_end;
	   probe != &marker && fde_compare (ob, linear->array[i], *probe) < 0;
	   probe = chain_end)
	{
	  chain_end = (fde **) erratic->array[probe - linear->array];
	  erratic->array[probe - linear->array] = NULL;
	}
      erratic->array[i] = (fde *) chain_end;
      chain_end = &linear->array[i];
    }

  /* Each entry in LINEAR which is part of the linear sequence we have
     discovered will correspond to a non-NULL entry in the chain we built in
     the ERRATIC array.  */
  for (i = j = k = 0; i < count; i++)
    if (erratic->array[i])
      linear->array[j++] = linear->array[i];
    else
      erratic->array[k++] = linear->array[i];
  linear->count = j;
  erratic->count = k;
}

/* This is O(n log(n)).  BSD/OS defines heapsort in stdlib.h, so we must
   use a name that does not conflict.  */

static void
frame_heapsort (struct object *ob, fde_compare_t fde_compare,
		struct fde_vector *erratic)
{
  /* For a description of this algorithm, see:
     Samuel P. Harbison, Guy L. Steele Jr.: C, a reference manual, 2nd ed.,
     p. 60-61.  */
  fde ** a = erratic->array;
  /* A portion of the array is called a "heap" if for all i>=0:
     If i and 2i+1 are valid indices, then a[i] >= a[2i+1].
     If i and 2i+2 are valid indices, then a[i] >= a[2i+2].  */
#define SWAP(x,y) do { fde * tmp = x; x = y; y = tmp; } while (0)
  size_t n = erratic->count;
  size_t m = n;
  size_t i;

  while (m > 0)
    {
      /* Invariant: a[m..n-1] is a heap.  */
      m--;
      for (i = m; 2*i+1 < n; )
	{
	  if (2*i+2 < n
	      && fde_compare (ob, a[2*i+2], a[2*i+1]) > 0
	      && fde_compare (ob, a[2*i+2], a[i]) > 0)
	    {
	      SWAP (a[i], a[2*i+2]);
	      i = 2*i+2;
	    }
	  else if (fde_compare (ob, a[2*i+1], a[i]) > 0)
	    {
	      SWAP (a[i], a[2*i+1]);
	      i = 2*i+1;
	    }
	  else
	    break;
	}
    }
  while (n > 1)
    {
      /* Invariant: a[0..n-1] is a heap.  */
      n--;
      SWAP (a[0], a[n]);
      for (i = 0; 2*i+1 < n; )
	{
	  if (2*i+2 < n
	      && fde_compare (ob, a[2*i+2], a[2*i+1]) > 0
	      && fde_compare (ob, a[2*i+2], a[i]) > 0)
	    {
	      SWAP (a[i], a[2*i+2]);
	      i = 2*i+2;
	    }
	  else if (fde_compare (ob, a[2*i+1], a[i]) > 0)
	    {
	      SWAP (a[i], a[2*i+1]);
	      i = 2*i+1;
	    }
	  else
	    break;
	}
    }
#undef SWAP
}

/* Merge V1 and V2, both sorted, and put the result into V1.  */
static void
fde_merge (struct object *ob, fde_compare_t fde_compare,
	   struct fde_vector *v1, struct fde_vector *v2)
{
  size_t i1, i2;
  fde * fde2;

  i2 = v2->count;
  if (i2 > 0)
    {
      i1 = v1->count;
      do
	{
	  i2--;
	  fde2 = v2->array[i2];
	  while (i1 > 0 && fde_compare (ob, v1->array[i1-1], fde2) > 0)
	    {
	      v1->array[i1+i2] = v1->array[i1-1];
	      i1--;
	    }
	  v1->array[i1+i2] = fde2;
	}
      while (i2 > 0);
      v1->count += v2->count;
    }
}

static void
end_fde_sort (struct object *ob, struct fde_accumulator *accu, size_t count)
{
  fde_compare_t fde_compare;

  if (accu->linear->count != count)
    abort ();

  if (ob->s.b.mixed_encoding)
    fde_compare = fde_mixed_encoding_compare;
  else if (ob->s.b.encoding == DW_EH_PE_absptr)
    fde_compare = fde_unencoded_compare;
  else
    fde_compare = fde_single_encoding_compare;

  if (accu->erratic)
    {
      fde_split (ob, fde_compare, accu->linear, accu->erratic);
      if (accu->linear->count + accu->erratic->count != count)
	abort ();
      frame_heapsort (ob, fde_compare, accu->erratic);
      fde_merge (ob, fde_compare, accu->linear, accu->erratic);
      free (accu->erratic);
    }
  else
    {
      /* We've not managed to malloc an erratic array,
	 so heap sort in the linear one.  */
      frame_heapsort (ob, fde_compare, accu->linear);
    }
}


/* Update encoding, mixed_encoding, and pc_begin for OB for the
   fde array beginning at THIS_FDE.  Return the number of fdes
   encountered along the way.  */

static size_t
classify_object_over_fdes (struct object *ob, fde *this_fde)
{
  struct dwarf_cie *last_cie = 0;
  size_t count = 0;
  int encoding = DW_EH_PE_absptr;
  _Unwind_Ptr base = 0;

  for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde))
    {
      struct dwarf_cie *this_cie;
      _Unwind_Ptr mask, pc_begin;

      /* Skip CIEs.  */
      if (this_fde->CIE_delta == 0)
	continue;

      /* Determine the encoding for this FDE.  Note mixed encoded
	 objects for later.  */
      this_cie = get_cie (this_fde);
      if (this_cie != last_cie)
	{
	  last_cie = this_cie;
	  encoding = get_cie_encoding (this_cie);
	  base = base_from_object (encoding, ob);
	  if (ob->s.b.encoding == DW_EH_PE_omit)
	    ob->s.b.encoding = encoding;
	  else if (ob->s.b.encoding != encoding)
	    ob->s.b.mixed_encoding = 1;
	}

      read_encoded_value_with_base (encoding, base, this_fde->pc_begin,
				    &pc_begin);

      /* Take care to ignore link-once functions that were removed.
	 In these cases, the function address will be NULL, but if
	 the encoding is smaller than a pointer a true NULL may not
	 be representable.  Assume 0 in the representable bits is NULL.  */
      mask = size_of_encoded_value (encoding);
      if (mask < sizeof (void *))
	mask = (1L << (mask << 3)) - 1;
      else
	mask = -1;

      if ((pc_begin & mask) == 0)
	continue;

      count += 1;
      if ((void *) pc_begin < ob->pc_begin)
	ob->pc_begin = (void *) pc_begin;
    }

  return count;
}

static void
add_fdes (struct object *ob, struct fde_accumulator *accu, fde *this_fde)
{
  struct dwarf_cie *last_cie = 0;
  int encoding = ob->s.b.encoding;
  _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob);

  for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde))
    {
      struct dwarf_cie *this_cie;

      /* Skip CIEs.  */
      if (this_fde->CIE_delta == 0)
	continue;

      if (ob->s.b.mixed_encoding)
	{
	  /* Determine the encoding for this FDE.  Note mixed encoded
	     objects for later.  */
	  this_cie = get_cie (this_fde);
	  if (this_cie != last_cie)
	    {
	      last_cie = this_cie;
	      encoding = get_cie_encoding (this_cie);
	      base = base_from_object (encoding, ob);
	    }
	}

      if (encoding == DW_EH_PE_absptr)
	{
	  if (get_pc_begin (this_fde, 0) == 0)
	    continue;
	}
      else
	{
	  _Unwind_Ptr pc_begin, mask;

	  read_encoded_value_with_base (encoding, base, this_fde->pc_begin,
					&pc_begin);

	  /* Take care to ignore link-once functions that were removed.
	     In these cases, the function address will be NULL, but if
	     the encoding is smaller than a pointer a true NULL may not
	     be representable.  Assume 0 in the representable bits is NULL.  */
	  mask = size_of_encoded_value (encoding);
	  if (mask < sizeof (void *))
	    mask = (1L << (mask << 3)) - 1;
	  else
	    mask = -1;

	  if ((pc_begin & mask) == 0)
	    continue;
	}

      fde_insert (accu, this_fde);
    }
}

/* Set up a sorted array of pointers to FDEs for a loaded object.  We
   count up the entries before allocating the array because it's likely to
   be faster.  We can be called multiple times, should we have failed to
   allocate a sorted fde array on a previous occasion.  */

static void
init_object (struct object* ob)
{
  struct fde_accumulator accu;
  size_t count;

  count = ob->s.b.count;
  if (count == 0)
    {
      if (ob->s.b.from_array)
	{
	  fde **p = ob->u.array;
	  for (count = 0; *p; ++p)
	    count += classify_object_over_fdes (ob, *p);
	}
      else
	count = classify_object_over_fdes (ob, ob->u.single);

      /* The count field we have in the main struct object is somewhat
	 limited, but should suffice for virtually all cases.  If the
	 counted value doesn't fit, re-write a zero.  The worst that
	 happens is that we re-count next time -- admittedly non-trivial
	 in that this implies some 2M fdes, but at least we function.  */
      ob->s.b.count = count;
      if (ob->s.b.count != count)
	ob->s.b.count = 0;
    }

  if (!start_fde_sort (&accu, count))
    return;

  if (ob->s.b.from_array)
    {
      fde **p;
      for (p = ob->u.array; *p; ++p)
	add_fdes (ob, &accu, *p);
    }
  else
    add_fdes (ob, &accu, ob->u.single);

  end_fde_sort (ob, &accu, count);

  /* Save the original fde pointer, since this is the key by which the
     DSO will deregister the object.  */
  accu.linear->orig_data = ob->u.single;
  ob->u.sort = accu.linear;

  ob->s.b.sorted = 1;
}

/* A linear search through a set of FDEs for the given PC.  This is
   used when there was insufficient memory to allocate and sort an
   array.  */

static fde *
linear_search_fdes (struct object *ob, fde *this_fde, void *pc)
{
  struct dwarf_cie *last_cie = 0;
  int encoding = ob->s.b.encoding;
  _Unwind_Ptr base = base_from_object (ob->s.b.encoding, ob);

  for (; ! last_fde (ob, this_fde); this_fde = next_fde (this_fde))
    {
      struct dwarf_cie *this_cie;
      _Unwind_Ptr pc_begin, pc_range;

      /* Skip CIEs.  */
      if (this_fde->CIE_delta == 0)
	continue;

      if (ob->s.b.mixed_encoding)
	{
	  /* Determine the encoding for this FDE.  Note mixed encoded
	     objects for later.  */
	  this_cie = get_cie (this_fde);
	  if (this_cie != last_cie)
	    {
	      last_cie = this_cie;
	      encoding = get_cie_encoding (this_cie);
	      base = base_from_object (encoding, ob);
	    }
	}

      if (encoding == DW_EH_PE_absptr)
	{
	  pc_begin = get_pc_begin (this_fde, 0);
	  pc_range = get_pc_begin (this_fde, 1);
	  if (pc_begin == 0)
	    continue;
	}
      else
	{
	  _Unwind_Ptr mask;
	  const unsigned char *p;

	  p = read_encoded_value_with_base (encoding, base,
					    this_fde->pc_begin, &pc_begin);
	  read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);

	  /* Take care to ignore link-once functions that were removed.
	     In these cases, the function address will be NULL, but if
	     the encoding is smaller than a pointer a true NULL may not
	     be representable.  Assume 0 in the representable bits is NULL.  */
	  mask = size_of_encoded_value (encoding);
	  if (mask < sizeof (void *))
	    mask = (1L << (mask << 3)) - 1;
	  else
	    mask = -1;

	  if ((pc_begin & mask) == 0)
	    continue;
	}

      if ((_Unwind_Ptr) pc - pc_begin < pc_range)
	return this_fde;
    }

  return NULL;
}

/* Binary search for an FDE containing the given PC.  Here are three
   implementations of increasing complexity.  */

static fde *
binary_search_unencoded_fdes (struct object *ob, void *pc)
{
  struct fde_vector *vec = ob->u.sort;
  size_t lo, hi;

  for (lo = 0, hi = vec->count; lo < hi; )
    {
      size_t i = (lo + hi) / 2;
      fde *f = vec->array[i];
      void *pc_begin;
      uaddr pc_range;

      pc_begin = (void *) get_pc_begin (f, 0);
      pc_range = (uaddr) get_pc_begin (f, 1);

      if (pc < pc_begin)
	hi = i;
      else if (pc >= pc_begin + pc_range)
	lo = i + 1;
      else
	return f;
    }

  return NULL;
}

static fde *
binary_search_single_encoding_fdes (struct object *ob, void *pc)
{
  struct fde_vector *vec = ob->u.sort;
  int encoding = ob->s.b.encoding;
  _Unwind_Ptr base = base_from_object (encoding, ob);
  size_t lo, hi;

  for (lo = 0, hi = vec->count; lo < hi; )
    {
      size_t i = (lo + hi) / 2;
      fde *f = vec->array[i];
      _Unwind_Ptr pc_begin, pc_range;
      const unsigned char *p;

      p = read_encoded_value_with_base (encoding, base, f->pc_begin,
					&pc_begin);
      read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);

      if ((_Unwind_Ptr) pc < pc_begin)
	hi = i;
      else if ((_Unwind_Ptr) pc >= pc_begin + pc_range)
	lo = i + 1;
      else
	return f;
    }

  return NULL;
}

static fde *
binary_search_mixed_encoding_fdes (struct object *ob, void *pc)
{
  struct fde_vector *vec = ob->u.sort;
  size_t lo, hi;

  for (lo = 0, hi = vec->count; lo < hi; )
    {
      size_t i = (lo + hi) / 2;
      fde *f = vec->array[i];
      _Unwind_Ptr pc_begin, pc_range;
      const unsigned char *p;
      int encoding;

      encoding = get_fde_encoding (f);
      p = read_encoded_value_with_base (encoding,
					base_from_object (encoding, ob),
					f->pc_begin, &pc_begin);
      read_encoded_value_with_base (encoding & 0x0F, 0, p, &pc_range);

      if ((_Unwind_Ptr) pc < pc_begin)
	hi = i;
      else if ((_Unwind_Ptr) pc >= pc_begin + pc_range)
	lo = i + 1;
      else
	return f;
    }

  return NULL;
}

static fde *
search_object (struct object* ob, void *pc)
{
  /* If the data hasn't been sorted, try to do this now.  We may have
     more memory available than last time we tried.  */
  if (! ob->s.b.sorted)
    {
      init_object (ob);

      /* Despite the above comment, the normal reason to get here is
	 that we've not processed this object before.  A quick range
	 check is in order.  */
      if (pc < ob->pc_begin)
	return NULL;
    }

  if (ob->s.b.sorted)
    {
      if (ob->s.b.mixed_encoding)
	return binary_search_mixed_encoding_fdes (ob, pc);
      else if (ob->s.b.encoding == DW_EH_PE_absptr)
	return binary_search_unencoded_fdes (ob, pc);
      else
	return binary_search_single_encoding_fdes (ob, pc);
    }
  else
    {
      /* Long slow labourious linear search, cos we've no memory.  */
      if (ob->s.b.from_array)
	{
	  fde **p;
	  for (p = ob->u.array; *p ; p++)
	    {
	      fde *f = linear_search_fdes (ob, *p, pc);
	      if (f)
		return f;
	    }
	  return NULL;
	}
      else
	return linear_search_fdes (ob, ob->u.single, pc);
    }
}

fde *
_Unwind_Find_FDE (void *pc, struct dwarf_eh_bases *bases)
{
  struct object *ob;
  fde *f = NULL;

  init_object_mutex_once ();
  __gthread_mutex_lock (&object_mutex);

  /* Linear search through the classified objects, to find the one
     containing the pc.  Note that pc_begin is sorted descending, and
     we expect objects to be non-overlapping.  */
  for (ob = seen_objects; ob; ob = ob->next)
    if (pc >= ob->pc_begin)
      {
	f = search_object (ob, pc);
	if (f)
	  goto fini;
	break;
      }

  /* Classify and search the objects we've not yet processed.  */
  while ((ob = unseen_objects))
    {
      struct object **p;

      unseen_objects = ob->next;
      f = search_object (ob, pc);

      /* Insert the object into the classified list.  */
      for (p = &seen_objects; *p ; p = &(*p)->next)
	if ((*p)->pc_begin < ob->pc_begin)
	  break;
      ob->next = *p;
      *p = ob;

      if (f)
	goto fini;
    }

 fini:
  __gthread_mutex_unlock (&object_mutex);

  if (f)
    {
      int encoding;
      _Unwind_Ptr func;

      bases->tbase = ob->tbase;
      bases->dbase = ob->dbase;

      encoding = ob->s.b.encoding;
      if (ob->s.b.mixed_encoding)
	encoding = get_fde_encoding (f);
      read_encoded_value_with_base (encoding, base_from_object (encoding, ob),
				    f->pc_begin, &func);
      bases->func = (void *) func;
    }

  return f;
}

#endif