summaryrefslogtreecommitdiff
path: root/gdb/solib-dsbt.c
blob: 59b195f491eb06f9d514bd7b53f83ec2f36c9f1a (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
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
/* Handle TIC6X (DSBT) shared libraries for GDB, the GNU Debugger.
   Copyright (C) 2010-2019 Free Software Foundation, Inc.

   This file is part of GDB.

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


#include "defs.h"
#include "inferior.h"
#include "gdbcore.h"
#include "solib.h"
#include "solist.h"
#include "objfiles.h"
#include "symtab.h"
#include "language.h"
#include "command.h"
#include "gdbcmd.h"
#include "elf-bfd.h"
#include "gdb_bfd.h"

#define GOT_MODULE_OFFSET 4

/* Flag which indicates whether internal debug messages should be printed.  */
static unsigned int solib_dsbt_debug = 0;

/* TIC6X pointers are four bytes wide.  */
enum { TIC6X_PTR_SIZE = 4 };

/* Representation of loadmap and related structs for the TIC6X DSBT.  */

/* External versions; the size and alignment of the fields should be
   the same as those on the target.  When loaded, the placement of
   the bits in each field will be the same as on the target.  */
typedef gdb_byte ext_Elf32_Half[2];
typedef gdb_byte ext_Elf32_Addr[4];
typedef gdb_byte ext_Elf32_Word[4];

struct ext_elf32_dsbt_loadseg
{
  /* Core address to which the segment is mapped.  */
  ext_Elf32_Addr addr;
  /* VMA recorded in the program header.  */
  ext_Elf32_Addr p_vaddr;
  /* Size of this segment in memory.  */
  ext_Elf32_Word p_memsz;
};

struct ext_elf32_dsbt_loadmap {
  /* Protocol version number, must be zero.  */
  ext_Elf32_Word version;
  /* A pointer to the DSBT table; the DSBT size and the index of this
     module.  */
  ext_Elf32_Word dsbt_table_ptr;
  ext_Elf32_Word dsbt_size;
  ext_Elf32_Word dsbt_index;
  /* Number of segments in this map.  */
  ext_Elf32_Word nsegs;
  /* The actual memory map.  */
  struct ext_elf32_dsbt_loadseg segs[1 /* nsegs, actually */];
};

/* Internal versions; the types are GDB types and the data in each
   of the fields is (or will be) decoded from the external struct
   for ease of consumption.  */
struct int_elf32_dsbt_loadseg
{
  /* Core address to which the segment is mapped.  */
  CORE_ADDR addr;
  /* VMA recorded in the program header.  */
  CORE_ADDR p_vaddr;
  /* Size of this segment in memory.  */
  long p_memsz;
};

struct int_elf32_dsbt_loadmap
{
  /* Protocol version number, must be zero.  */
  int version;
  CORE_ADDR dsbt_table_ptr;
  /* A pointer to the DSBT table; the DSBT size and the index of this
     module.  */
  int dsbt_size, dsbt_index;
  /* Number of segments in this map.  */
  int nsegs;
  /* The actual memory map.  */
  struct int_elf32_dsbt_loadseg segs[1 /* nsegs, actually */];
};

/* External link_map and elf32_dsbt_loadaddr struct definitions.  */

typedef gdb_byte ext_ptr[4];

struct ext_elf32_dsbt_loadaddr
{
  ext_ptr map;			/* struct elf32_dsbt_loadmap *map; */
};

struct ext_link_map
{
  struct ext_elf32_dsbt_loadaddr l_addr;

  /* Absolute file name object was found in.  */
  ext_ptr l_name;		/* char *l_name; */

  /* Dynamic section of the shared object.  */
  ext_ptr l_ld;			/* ElfW(Dyn) *l_ld; */

  /* Chain of loaded objects.  */
  ext_ptr l_next, l_prev;	/* struct link_map *l_next, *l_prev; */
};

/* Link map info to include in an allocated so_list entry */

struct lm_info_dsbt : public lm_info_base
{
  ~lm_info_dsbt ()
  {
    xfree (this->map);
  }

  /* The loadmap, digested into an easier to use form.  */
  int_elf32_dsbt_loadmap *map = NULL;
};

/* Per pspace dsbt specific data.  */

struct dsbt_info
{
  /* The load map, got value, etc. are not available from the chain
     of loaded shared objects.  ``main_executable_lm_info'' provides
     a way to get at this information so that it doesn't need to be
     frequently recomputed.  Initialized by dsbt_relocate_main_executable.  */
  struct lm_info_dsbt *main_executable_lm_info = nullptr;

  /* Load maps for the main executable and the interpreter.  These are obtained
     from ptrace.  They are the starting point for getting into the program,
     and are required to find the solib list with the individual load maps for
     each module.  */
  struct int_elf32_dsbt_loadmap *exec_loadmap = nullptr;
  struct int_elf32_dsbt_loadmap *interp_loadmap = nullptr;

  /* Cached value for lm_base, below.  */
  CORE_ADDR lm_base_cache = 0;

  /* Link map address for main module.  */
  CORE_ADDR main_lm_addr = 0;

  CORE_ADDR interp_text_sect_low = 0;
  CORE_ADDR interp_text_sect_high = 0;
  CORE_ADDR interp_plt_sect_low = 0;
  CORE_ADDR interp_plt_sect_high = 0;
};

/* Per-program-space data key.  */
static program_space_key<dsbt_info> solib_dsbt_pspace_data;

/* Get the current dsbt data.  If none is found yet, add it now.  This
   function always returns a valid object.  */

static struct dsbt_info *
get_dsbt_info (void)
{
  struct dsbt_info *info;

  info = solib_dsbt_pspace_data.get (current_program_space);
  if (info != NULL)
    return info;

  return solib_dsbt_pspace_data.emplace (current_program_space);
}


static void
dsbt_print_loadmap (struct int_elf32_dsbt_loadmap *map)
{
  int i;

  if (map == NULL)
    printf_filtered ("(null)\n");
  else if (map->version != 0)
    printf_filtered (_("Unsupported map version: %d\n"), map->version);
  else
    {
      printf_filtered ("version %d\n", map->version);

      for (i = 0; i < map->nsegs; i++)
	printf_filtered ("%s:%s -> %s:%s\n",
			 print_core_address (target_gdbarch (),
					     map->segs[i].p_vaddr),
			 print_core_address (target_gdbarch (),
					     map->segs[i].p_vaddr
					     + map->segs[i].p_memsz),
			 print_core_address (target_gdbarch (), map->segs[i].addr),
			 print_core_address (target_gdbarch (), map->segs[i].addr
					     + map->segs[i].p_memsz));
    }
}

/* Decode int_elf32_dsbt_loadmap from BUF.  */

static struct int_elf32_dsbt_loadmap *
decode_loadmap (const gdb_byte *buf)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
  const struct ext_elf32_dsbt_loadmap *ext_ldmbuf;
  struct int_elf32_dsbt_loadmap *int_ldmbuf;

  int version, seg, nsegs;
  int int_ldmbuf_size;

  ext_ldmbuf = (struct ext_elf32_dsbt_loadmap *) buf;

  /* Extract the version.  */
  version = extract_unsigned_integer (ext_ldmbuf->version,
				      sizeof ext_ldmbuf->version,
				      byte_order);
  if (version != 0)
    {
      /* We only handle version 0.  */
      return NULL;
    }

  /* Extract the number of segments.  */
  nsegs = extract_unsigned_integer (ext_ldmbuf->nsegs,
				    sizeof ext_ldmbuf->nsegs,
				    byte_order);

  if (nsegs <= 0)
    return NULL;

  /* Allocate space into which to put information extract from the
     external loadsegs.  I.e, allocate the internal loadsegs.  */
  int_ldmbuf_size = (sizeof (struct int_elf32_dsbt_loadmap)
		     + (nsegs - 1) * sizeof (struct int_elf32_dsbt_loadseg));
  int_ldmbuf = (struct int_elf32_dsbt_loadmap *) xmalloc (int_ldmbuf_size);

  /* Place extracted information in internal structs.  */
  int_ldmbuf->version = version;
  int_ldmbuf->nsegs = nsegs;
  for (seg = 0; seg < nsegs; seg++)
    {
      int_ldmbuf->segs[seg].addr
	= extract_unsigned_integer (ext_ldmbuf->segs[seg].addr,
				    sizeof (ext_ldmbuf->segs[seg].addr),
				    byte_order);
      int_ldmbuf->segs[seg].p_vaddr
	= extract_unsigned_integer (ext_ldmbuf->segs[seg].p_vaddr,
				    sizeof (ext_ldmbuf->segs[seg].p_vaddr),
				    byte_order);
      int_ldmbuf->segs[seg].p_memsz
	= extract_unsigned_integer (ext_ldmbuf->segs[seg].p_memsz,
				    sizeof (ext_ldmbuf->segs[seg].p_memsz),
				    byte_order);
    }

  return int_ldmbuf;
}


static struct dsbt_info *get_dsbt_info (void);

/* Interrogate the Linux kernel to find out where the program was loaded.
   There are two load maps; one for the executable and one for the
   interpreter (only in the case of a dynamically linked executable).  */

static void
dsbt_get_initial_loadmaps (void)
{
  struct dsbt_info *info = get_dsbt_info ();
  gdb::optional<gdb::byte_vector> buf
    = target_read_alloc (current_top_target (), TARGET_OBJECT_FDPIC, "exec");

  if (!buf || buf->empty ())
    {
      info->exec_loadmap = NULL;
      error (_("Error reading DSBT exec loadmap"));
    }
  info->exec_loadmap = decode_loadmap (buf->data ());
  if (solib_dsbt_debug)
    dsbt_print_loadmap (info->exec_loadmap);

  buf = target_read_alloc (current_top_target (), TARGET_OBJECT_FDPIC, "exec");
  if (!buf || buf->empty ())
    {
      info->interp_loadmap = NULL;
      error (_("Error reading DSBT interp loadmap"));
    }
  info->interp_loadmap = decode_loadmap (buf->data ());
  if (solib_dsbt_debug)
    dsbt_print_loadmap (info->interp_loadmap);
}

/* Given address LDMADDR, fetch and decode the loadmap at that address.
   Return NULL if there is a problem reading the target memory or if
   there doesn't appear to be a loadmap at the given address.  The
   allocated space (representing the loadmap) returned by this
   function may be freed via a single call to xfree.  */

static struct int_elf32_dsbt_loadmap *
fetch_loadmap (CORE_ADDR ldmaddr)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
  struct ext_elf32_dsbt_loadmap ext_ldmbuf_partial;
  struct ext_elf32_dsbt_loadmap *ext_ldmbuf;
  struct int_elf32_dsbt_loadmap *int_ldmbuf;
  int ext_ldmbuf_size, int_ldmbuf_size;
  int version, seg, nsegs;

  /* Fetch initial portion of the loadmap.  */
  if (target_read_memory (ldmaddr, (gdb_byte *) &ext_ldmbuf_partial,
			  sizeof ext_ldmbuf_partial))
    {
      /* Problem reading the target's memory.  */
      return NULL;
    }

  /* Extract the version.  */
  version = extract_unsigned_integer (ext_ldmbuf_partial.version,
				      sizeof ext_ldmbuf_partial.version,
				      byte_order);
  if (version != 0)
    {
      /* We only handle version 0.  */
      return NULL;
    }

  /* Extract the number of segments.  */
  nsegs = extract_unsigned_integer (ext_ldmbuf_partial.nsegs,
				    sizeof ext_ldmbuf_partial.nsegs,
				    byte_order);

  if (nsegs <= 0)
    return NULL;

  /* Allocate space for the complete (external) loadmap.  */
  ext_ldmbuf_size = sizeof (struct ext_elf32_dsbt_loadmap)
    + (nsegs - 1) * sizeof (struct ext_elf32_dsbt_loadseg);
  ext_ldmbuf = (struct ext_elf32_dsbt_loadmap *) xmalloc (ext_ldmbuf_size);

  /* Copy over the portion of the loadmap that's already been read.  */
  memcpy (ext_ldmbuf, &ext_ldmbuf_partial, sizeof ext_ldmbuf_partial);

  /* Read the rest of the loadmap from the target.  */
  if (target_read_memory (ldmaddr + sizeof ext_ldmbuf_partial,
			  (gdb_byte *) ext_ldmbuf + sizeof ext_ldmbuf_partial,
			  ext_ldmbuf_size - sizeof ext_ldmbuf_partial))
    {
      /* Couldn't read rest of the loadmap.  */
      xfree (ext_ldmbuf);
      return NULL;
    }

  /* Allocate space into which to put information extract from the
     external loadsegs.  I.e, allocate the internal loadsegs.  */
  int_ldmbuf_size = sizeof (struct int_elf32_dsbt_loadmap)
    + (nsegs - 1) * sizeof (struct int_elf32_dsbt_loadseg);
  int_ldmbuf = (struct int_elf32_dsbt_loadmap *) xmalloc (int_ldmbuf_size);

  /* Place extracted information in internal structs.  */
  int_ldmbuf->version = version;
  int_ldmbuf->nsegs = nsegs;
  for (seg = 0; seg < nsegs; seg++)
    {
      int_ldmbuf->segs[seg].addr
	= extract_unsigned_integer (ext_ldmbuf->segs[seg].addr,
				    sizeof (ext_ldmbuf->segs[seg].addr),
				    byte_order);
      int_ldmbuf->segs[seg].p_vaddr
	= extract_unsigned_integer (ext_ldmbuf->segs[seg].p_vaddr,
				    sizeof (ext_ldmbuf->segs[seg].p_vaddr),
				    byte_order);
      int_ldmbuf->segs[seg].p_memsz
	= extract_unsigned_integer (ext_ldmbuf->segs[seg].p_memsz,
				    sizeof (ext_ldmbuf->segs[seg].p_memsz),
				    byte_order);
    }

  xfree (ext_ldmbuf);
  return int_ldmbuf;
}

static void dsbt_relocate_main_executable (void);
static int enable_break (void);

/* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
   returned and the corresponding PTR is set.  */

static int
scan_dyntag (int dyntag, bfd *abfd, CORE_ADDR *ptr)
{
  int arch_size, step, sect_size;
  long dyn_tag;
  CORE_ADDR dyn_ptr, dyn_addr;
  gdb_byte *bufend, *bufstart, *buf;
  Elf32_External_Dyn *x_dynp_32;
  Elf64_External_Dyn *x_dynp_64;
  struct bfd_section *sect;
  struct target_section *target_section;

  if (abfd == NULL)
    return 0;

  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
    return 0;

  arch_size = bfd_get_arch_size (abfd);
  if (arch_size == -1)
    return 0;

  /* Find the start address of the .dynamic section.  */
  sect = bfd_get_section_by_name (abfd, ".dynamic");
  if (sect == NULL)
    return 0;

  for (target_section = current_target_sections->sections;
       target_section < current_target_sections->sections_end;
       target_section++)
    if (sect == target_section->the_bfd_section)
      break;
  if (target_section < current_target_sections->sections_end)
    dyn_addr = target_section->addr;
  else
    {
      /* ABFD may come from OBJFILE acting only as a symbol file without being
	 loaded into the target (see add_symbol_file_command).  This case is
	 such fallback to the file VMA address without the possibility of
	 having the section relocated to its actual in-memory address.  */

      dyn_addr = bfd_section_vma (abfd, sect);
    }

  /* Read in .dynamic from the BFD.  We will get the actual value
     from memory later.  */
  sect_size = bfd_section_size (abfd, sect);
  buf = bufstart = (gdb_byte *) alloca (sect_size);
  if (!bfd_get_section_contents (abfd, sect,
				 buf, 0, sect_size))
    return 0;

  /* Iterate over BUF and scan for DYNTAG.  If found, set PTR and return.  */
  step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
			   : sizeof (Elf64_External_Dyn);
  for (bufend = buf + sect_size;
       buf < bufend;
       buf += step)
  {
    if (arch_size == 32)
      {
	x_dynp_32 = (Elf32_External_Dyn *) buf;
	dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_tag);
	dyn_ptr = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_un.d_ptr);
      }
    else
      {
	x_dynp_64 = (Elf64_External_Dyn *) buf;
	dyn_tag = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_tag);
	dyn_ptr = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_un.d_ptr);
      }
     if (dyn_tag == DT_NULL)
       return 0;
     if (dyn_tag == dyntag)
       {
	 /* If requested, try to read the runtime value of this .dynamic
	    entry.  */
	 if (ptr)
	   {
	     struct type *ptr_type;
	     gdb_byte ptr_buf[8];
	     CORE_ADDR ptr_addr;

	     ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
	     ptr_addr = dyn_addr + (buf - bufstart) + arch_size / 8;
	     if (target_read_memory (ptr_addr, ptr_buf, arch_size / 8) == 0)
	       dyn_ptr = extract_typed_address (ptr_buf, ptr_type);
	     *ptr = dyn_ptr;
	   }
	 return 1;
       }
  }

  return 0;
}

/* See solist.h. */

static int
open_symbol_file_object (int from_tty)
{
  /* Unimplemented.  */
  return 0;
}

/* Given a loadmap and an address, return the displacement needed
   to relocate the address.  */

static CORE_ADDR
displacement_from_map (struct int_elf32_dsbt_loadmap *map,
		       CORE_ADDR addr)
{
  int seg;

  for (seg = 0; seg < map->nsegs; seg++)
    if (map->segs[seg].p_vaddr <= addr
	&& addr < map->segs[seg].p_vaddr + map->segs[seg].p_memsz)
      return map->segs[seg].addr - map->segs[seg].p_vaddr;

  return 0;
}

/* Return the address from which the link map chain may be found.  On
   DSBT, a pointer to the start of the link map will be located at the
   word found at base of GOT + GOT_MODULE_OFFSET.

   The base of GOT may be found in a number of ways.  Assuming that the
   main executable has already been relocated,
   1 The easiest way to find this value is to look up the address of
   _GLOBAL_OFFSET_TABLE_.
   2 The other way is to look for tag DT_PLTGOT, which contains the virtual
   address of Global Offset Table.  .*/

static CORE_ADDR
lm_base (void)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
  struct bound_minimal_symbol got_sym;
  CORE_ADDR addr;
  gdb_byte buf[TIC6X_PTR_SIZE];
  struct dsbt_info *info = get_dsbt_info ();

  /* One of our assumptions is that the main executable has been relocated.
     Bail out if this has not happened.  (Note that post_create_inferior
     in infcmd.c will call solib_add prior to solib_create_inferior_hook.
     If we allow this to happen, lm_base_cache will be initialized with
     a bogus value.  */
  if (info->main_executable_lm_info == 0)
    return 0;

  /* If we already have a cached value, return it.  */
  if (info->lm_base_cache)
    return info->lm_base_cache;

  got_sym = lookup_minimal_symbol ("_GLOBAL_OFFSET_TABLE_", NULL,
				   symfile_objfile);

  if (got_sym.minsym != 0)
    {
      addr = BMSYMBOL_VALUE_ADDRESS (got_sym);
      if (solib_dsbt_debug)
	fprintf_unfiltered (gdb_stdlog,
			    "lm_base: get addr %x by _GLOBAL_OFFSET_TABLE_.\n",
			    (unsigned int) addr);
    }
  else if (scan_dyntag (DT_PLTGOT, exec_bfd, &addr))
    {
      struct int_elf32_dsbt_loadmap *ldm;

      dsbt_get_initial_loadmaps ();
      ldm = info->exec_loadmap;
      addr += displacement_from_map (ldm, addr);
      if (solib_dsbt_debug)
	fprintf_unfiltered (gdb_stdlog,
			    "lm_base: get addr %x by DT_PLTGOT.\n",
			    (unsigned int) addr);
    }
  else
    {
      if (solib_dsbt_debug)
	fprintf_unfiltered (gdb_stdlog,
			    "lm_base: _GLOBAL_OFFSET_TABLE_ not found.\n");
      return 0;
    }
  addr += GOT_MODULE_OFFSET;

  if (solib_dsbt_debug)
    fprintf_unfiltered (gdb_stdlog,
			"lm_base: _GLOBAL_OFFSET_TABLE_ + %d = %s\n",
			GOT_MODULE_OFFSET, hex_string_custom (addr, 8));

  if (target_read_memory (addr, buf, sizeof buf) != 0)
    return 0;
  info->lm_base_cache = extract_unsigned_integer (buf, sizeof buf, byte_order);

  if (solib_dsbt_debug)
    fprintf_unfiltered (gdb_stdlog,
			"lm_base: lm_base_cache = %s\n",
			hex_string_custom (info->lm_base_cache, 8));

  return info->lm_base_cache;
}


/* Build a list of `struct so_list' objects describing the shared
   objects currently loaded in the inferior.  This list does not
   include an entry for the main executable file.

   Note that we only gather information directly available from the
   inferior --- we don't examine any of the shared library files
   themselves.  The declaration of `struct so_list' says which fields
   we provide values for.  */

static struct so_list *
dsbt_current_sos (void)
{
  enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
  CORE_ADDR lm_addr;
  struct so_list *sos_head = NULL;
  struct so_list **sos_next_ptr = &sos_head;
  struct dsbt_info *info = get_dsbt_info ();

  /* Make sure that the main executable has been relocated.  This is
     required in order to find the address of the global offset table,
     which in turn is used to find the link map info.  (See lm_base
     for details.)

     Note that the relocation of the main executable is also performed
     by solib_create_inferior_hook, however, in the case of core
     files, this hook is called too late in order to be of benefit to
     solib_add.  solib_add eventually calls this function,
     dsbt_current_sos, and also precedes the call to
     solib_create_inferior_hook.   (See post_create_inferior in
     infcmd.c.)  */
  if (info->main_executable_lm_info == 0 && core_bfd != NULL)
    dsbt_relocate_main_executable ();

  /* Locate the address of the first link map struct.  */
  lm_addr = lm_base ();

  /* We have at least one link map entry.  Fetch the lot of them,
     building the solist chain.  */
  while (lm_addr)
    {
      struct ext_link_map lm_buf;
      ext_Elf32_Word indexword;
      CORE_ADDR map_addr;
      int dsbt_index;
      int ret;

      if (solib_dsbt_debug)
	fprintf_unfiltered (gdb_stdlog,
			    "current_sos: reading link_map entry at %s\n",
			    hex_string_custom (lm_addr, 8));

      ret = target_read_memory (lm_addr, (gdb_byte *) &lm_buf, sizeof (lm_buf));
      if (ret)
	{
	  warning (_("dsbt_current_sos: Unable to read link map entry."
		     "  Shared object chain may be incomplete."));
	  break;
	}

      /* Fetch the load map address.  */
      map_addr = extract_unsigned_integer (lm_buf.l_addr.map,
					   sizeof lm_buf.l_addr.map,
					   byte_order);

      ret = target_read_memory (map_addr + 12, (gdb_byte *) &indexword,
				sizeof indexword);
      if (ret)
	{
	  warning (_("dsbt_current_sos: Unable to read dsbt index."
		     "  Shared object chain may be incomplete."));
	  break;
	}
      dsbt_index = extract_unsigned_integer (indexword, sizeof indexword,
					     byte_order);

      /* If the DSBT index is zero, then we're looking at the entry
	 for the main executable.  By convention, we don't include
	 this in the list of shared objects.  */
      if (dsbt_index != 0)
	{
	  int errcode;
	  gdb::unique_xmalloc_ptr<char> name_buf;
	  struct int_elf32_dsbt_loadmap *loadmap;
	  struct so_list *sop;
	  CORE_ADDR addr;

	  loadmap = fetch_loadmap (map_addr);
	  if (loadmap == NULL)
	    {
	      warning (_("dsbt_current_sos: Unable to fetch load map."
			 "  Shared object chain may be incomplete."));
	      break;
	    }

	  sop = XCNEW (struct so_list);
	  lm_info_dsbt *li = new lm_info_dsbt;
	  sop->lm_info = li;
	  li->map = loadmap;
	  /* Fetch the name.  */
	  addr = extract_unsigned_integer (lm_buf.l_name,
					   sizeof (lm_buf.l_name),
					   byte_order);
	  target_read_string (addr, &name_buf, SO_NAME_MAX_PATH_SIZE - 1,
			      &errcode);

	  if (errcode != 0)
	    warning (_("Can't read pathname for link map entry: %s."),
		     safe_strerror (errcode));
	  else
	    {
	      if (solib_dsbt_debug)
		fprintf_unfiltered (gdb_stdlog, "current_sos: name = %s\n",
				    name_buf.get ());

	      strncpy (sop->so_name, name_buf.get (), SO_NAME_MAX_PATH_SIZE - 1);
	      sop->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
	      strcpy (sop->so_original_name, sop->so_name);
	    }

	  *sos_next_ptr = sop;
	  sos_next_ptr = &sop->next;
	}
      else
	{
	  info->main_lm_addr = lm_addr;
	}

      lm_addr = extract_unsigned_integer (lm_buf.l_next,
					  sizeof (lm_buf.l_next), byte_order);
    }

  return sos_head;
}

/* Return 1 if PC lies in the dynamic symbol resolution code of the
   run time loader.  */

static int
dsbt_in_dynsym_resolve_code (CORE_ADDR pc)
{
  struct dsbt_info *info = get_dsbt_info ();

  return ((pc >= info->interp_text_sect_low && pc < info->interp_text_sect_high)
	  || (pc >= info->interp_plt_sect_low && pc < info->interp_plt_sect_high)
	  || in_plt_section (pc));
}

/* Print a warning about being unable to set the dynamic linker
   breakpoint.  */

static void
enable_break_failure_warning (void)
{
  warning (_("Unable to find dynamic linker breakpoint function.\n"
	     "GDB will be unable to debug shared library initializers\n"
	     "and track explicitly loaded dynamic code."));
}

/* Helper function for gdb_bfd_lookup_symbol.  */

static int
cmp_name (const asymbol *sym, const void *data)
{
  return (strcmp (sym->name, (const char *) data) == 0);
}

/* The dynamic linkers has, as part of its debugger interface, support
   for arranging for the inferior to hit a breakpoint after mapping in
   the shared libraries.  This function enables that breakpoint.

   On the TIC6X, using the shared library (DSBT), GDB can try to place
   a breakpoint on '_dl_debug_state' to monitor the shared library
   event.  */

static int
enable_break (void)
{
  asection *interp_sect;
  struct dsbt_info *info;

  if (exec_bfd == NULL)
    return 0;

  if (!target_has_execution)
    return 0;

  info = get_dsbt_info ();

  info->interp_text_sect_low = 0;
  info->interp_text_sect_high = 0;
  info->interp_plt_sect_low = 0;
  info->interp_plt_sect_high = 0;

  /* Find the .interp section; if not found, warn the user and drop
     into the old breakpoint at symbol code.  */
  interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
  if (interp_sect)
    {
      unsigned int interp_sect_size;
      char *buf;
      CORE_ADDR addr;
      struct int_elf32_dsbt_loadmap *ldm;
      int ret;

      /* Read the contents of the .interp section into a local buffer;
	 the contents specify the dynamic linker this program uses.  */
      interp_sect_size = bfd_section_size (exec_bfd, interp_sect);
      buf = (char *) alloca (interp_sect_size);
      bfd_get_section_contents (exec_bfd, interp_sect,
				buf, 0, interp_sect_size);

      /* Now we need to figure out where the dynamic linker was
	 loaded so that we can load its symbols and place a breakpoint
	 in the dynamic linker itself.  */

      gdb_bfd_ref_ptr tmp_bfd;
      try
	{
	  tmp_bfd = solib_bfd_open (buf);
	}
      catch (const gdb_exception &ex)
	{
	}

      if (tmp_bfd == NULL)
	{
	  enable_break_failure_warning ();
	  return 0;
	}

      dsbt_get_initial_loadmaps ();
      ldm = info->interp_loadmap;

      /* Record the relocated start and end address of the dynamic linker
	 text and plt section for dsbt_in_dynsym_resolve_code.  */
      interp_sect = bfd_get_section_by_name (tmp_bfd.get (), ".text");
      if (interp_sect)
	{
	  info->interp_text_sect_low
	    = bfd_section_vma (tmp_bfd.get (), interp_sect);
	  info->interp_text_sect_low
	    += displacement_from_map (ldm, info->interp_text_sect_low);
	  info->interp_text_sect_high
	    = info->interp_text_sect_low
	    + bfd_section_size (tmp_bfd.get (), interp_sect);
	}
      interp_sect = bfd_get_section_by_name (tmp_bfd.get (), ".plt");
      if (interp_sect)
	{
	  info->interp_plt_sect_low =
	    bfd_section_vma (tmp_bfd.get (), interp_sect);
	  info->interp_plt_sect_low
	    += displacement_from_map (ldm, info->interp_plt_sect_low);
	  info->interp_plt_sect_high =
	    info->interp_plt_sect_low + bfd_section_size (tmp_bfd.get (),
							  interp_sect);
	}

      addr = gdb_bfd_lookup_symbol (tmp_bfd.get (), cmp_name,
				    "_dl_debug_state");
      if (addr != 0)
	{
	  if (solib_dsbt_debug)
	    fprintf_unfiltered (gdb_stdlog,
				"enable_break: _dl_debug_state (prior to relocation) = %s\n",
				hex_string_custom (addr, 8));
	  addr += displacement_from_map (ldm, addr);

	  if (solib_dsbt_debug)
	    fprintf_unfiltered (gdb_stdlog,
				"enable_break: _dl_debug_state (after relocation) = %s\n",
				hex_string_custom (addr, 8));

	  /* Now (finally!) create the solib breakpoint.  */
	  create_solib_event_breakpoint (target_gdbarch (), addr);

	  ret = 1;
	}
      else
	{
	  if (solib_dsbt_debug)
	    fprintf_unfiltered (gdb_stdlog,
				"enable_break: _dl_debug_state is not found\n");
	  ret = 0;
	}

      /* We're done with the loadmap.  */
      xfree (ldm);

      return ret;
    }

  /* Tell the user we couldn't set a dynamic linker breakpoint.  */
  enable_break_failure_warning ();

  /* Failure return.  */
  return 0;
}

static void
dsbt_relocate_main_executable (void)
{
  struct int_elf32_dsbt_loadmap *ldm;
  int changed;
  struct obj_section *osect;
  struct dsbt_info *info = get_dsbt_info ();

  dsbt_get_initial_loadmaps ();
  ldm = info->exec_loadmap;

  delete info->main_executable_lm_info;
  info->main_executable_lm_info = new lm_info_dsbt;
  info->main_executable_lm_info->map = ldm;

  gdb::unique_xmalloc_ptr<struct section_offsets> new_offsets
    (XCNEWVEC (struct section_offsets, symfile_objfile->num_sections));
  changed = 0;

  ALL_OBJFILE_OSECTIONS (symfile_objfile, osect)
    {
      CORE_ADDR orig_addr, addr, offset;
      int osect_idx;
      int seg;

      osect_idx = osect - symfile_objfile->sections;

      /* Current address of section.  */
      addr = obj_section_addr (osect);
      /* Offset from where this section started.  */
      offset = ANOFFSET (symfile_objfile->section_offsets, osect_idx);
      /* Original address prior to any past relocations.  */
      orig_addr = addr - offset;

      for (seg = 0; seg < ldm->nsegs; seg++)
	{
	  if (ldm->segs[seg].p_vaddr <= orig_addr
	      && orig_addr < ldm->segs[seg].p_vaddr + ldm->segs[seg].p_memsz)
	    {
	      new_offsets->offsets[osect_idx]
		= ldm->segs[seg].addr - ldm->segs[seg].p_vaddr;

	      if (new_offsets->offsets[osect_idx] != offset)
		changed = 1;
	      break;
	    }
	}
    }

  if (changed)
    objfile_relocate (symfile_objfile, new_offsets.get ());

  /* Now that symfile_objfile has been relocated, we can compute the
     GOT value and stash it away.  */
}

/* When gdb starts up the inferior, it nurses it along (through the
   shell) until it is ready to execute it's first instruction.  At this
   point, this function gets called via solib_create_inferior_hook.

   For the DSBT shared library, the main executable needs to be relocated.
   The shared library breakpoints also need to be enabled.  */

static void
dsbt_solib_create_inferior_hook (int from_tty)
{
  /* Relocate main executable.  */
  dsbt_relocate_main_executable ();

  /* Enable shared library breakpoints.  */
  if (!enable_break ())
    {
      warning (_("shared library handler failed to enable breakpoint"));
      return;
    }
}

static void
dsbt_clear_solib (void)
{
  struct dsbt_info *info = get_dsbt_info ();

  info->lm_base_cache = 0;
  info->main_lm_addr = 0;

  delete info->main_executable_lm_info;
  info->main_executable_lm_info = NULL;
}

static void
dsbt_free_so (struct so_list *so)
{
  lm_info_dsbt *li = (lm_info_dsbt *) so->lm_info;

  delete li;
}

static void
dsbt_relocate_section_addresses (struct so_list *so,
				 struct target_section *sec)
{
  int seg;
  lm_info_dsbt *li = (lm_info_dsbt *) so->lm_info;
  int_elf32_dsbt_loadmap *map = li->map;

  for (seg = 0; seg < map->nsegs; seg++)
    {
      if (map->segs[seg].p_vaddr <= sec->addr
	  && sec->addr < map->segs[seg].p_vaddr + map->segs[seg].p_memsz)
	{
	  CORE_ADDR displ = map->segs[seg].addr - map->segs[seg].p_vaddr;

	  sec->addr += displ;
	  sec->endaddr += displ;
	  break;
	}
    }
}
static void
show_dsbt_debug (struct ui_file *file, int from_tty,
		 struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("solib-dsbt debugging is %s.\n"), value);
}

struct target_so_ops dsbt_so_ops;

void
_initialize_dsbt_solib (void)
{
  dsbt_so_ops.relocate_section_addresses = dsbt_relocate_section_addresses;
  dsbt_so_ops.free_so = dsbt_free_so;
  dsbt_so_ops.clear_solib = dsbt_clear_solib;
  dsbt_so_ops.solib_create_inferior_hook = dsbt_solib_create_inferior_hook;
  dsbt_so_ops.current_sos = dsbt_current_sos;
  dsbt_so_ops.open_symbol_file_object = open_symbol_file_object;
  dsbt_so_ops.in_dynsym_resolve_code = dsbt_in_dynsym_resolve_code;
  dsbt_so_ops.bfd_open = solib_bfd_open;

  /* Debug this file's internals.  */
  add_setshow_zuinteger_cmd ("solib-dsbt", class_maintenance,
			     &solib_dsbt_debug, _("\
Set internal debugging of shared library code for DSBT ELF."), _("\
Show internal debugging of shared library code for DSBT ELF."), _("\
When non-zero, DSBT solib specific internal debugging is enabled."),
			     NULL,
			     show_dsbt_debug,
			     &setdebuglist, &showdebuglist);
}