summaryrefslogtreecommitdiff
path: root/gdb/i386-linux-nat.c
blob: ed555ef4e2b2ef3a8229ed92a06c84a83419b3e5 (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
/* Native-dependent code for GNU/Linux i386.

   Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
   2009, 2010, 2011 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 "i386-nat.h"
#include "inferior.h"
#include "gdbcore.h"
#include "regcache.h"
#include "regset.h"
#include "target.h"
#include "linux-nat.h"

#include "gdb_assert.h"
#include "gdb_string.h"
#include "elf/common.h"
#include <sys/uio.h>
#include <sys/ptrace.h>
#include <sys/user.h>
#include <sys/procfs.h>

#ifdef HAVE_SYS_REG_H
#include <sys/reg.h>
#endif

#ifndef ORIG_EAX
#define ORIG_EAX -1
#endif

#ifdef HAVE_SYS_DEBUGREG_H
#include <sys/debugreg.h>
#endif

#ifndef DR_FIRSTADDR
#define DR_FIRSTADDR 0
#endif

#ifndef DR_LASTADDR
#define DR_LASTADDR 3
#endif

#ifndef DR_STATUS
#define DR_STATUS 6
#endif

#ifndef DR_CONTROL
#define DR_CONTROL 7
#endif

/* Prototypes for supply_gregset etc.  */
#include "gregset.h"

#include "i387-tdep.h"
#include "i386-tdep.h"
#include "i386-linux-tdep.h"

/* Defines ps_err_e, struct ps_prochandle.  */
#include "gdb_proc_service.h"

#include "i386-xstate.h"

#ifndef PTRACE_GETREGSET
#define PTRACE_GETREGSET	0x4204
#endif

#ifndef PTRACE_SETREGSET
#define PTRACE_SETREGSET	0x4205
#endif

/* Does the current host support PTRACE_GETREGSET?  */
static int have_ptrace_getregset = -1;


/* The register sets used in GNU/Linux ELF core-dumps are identical to
   the register sets in `struct user' that is used for a.out
   core-dumps, and is also used by `ptrace'.  The corresponding types
   are `elf_gregset_t' for the general-purpose registers (with
   `elf_greg_t' the type of a single GP register) and `elf_fpregset_t'
   for the floating-point registers.

   Those types used to be available under the names `gregset_t' and
   `fpregset_t' too, and this file used those names in the past.  But
   those names are now used for the register sets used in the
   `mcontext_t' type, and have a different size and layout.  */

/* Which ptrace request retrieves which registers?
   These apply to the corresponding SET requests as well.  */

#define GETREGS_SUPPLIES(regno) \
  ((0 <= (regno) && (regno) <= 15) || (regno) == I386_LINUX_ORIG_EAX_REGNUM)

#define GETFPXREGS_SUPPLIES(regno) \
  (I386_ST0_REGNUM <= (regno) && (regno) < I386_SSE_NUM_REGS)

#define GETXSTATEREGS_SUPPLIES(regno) \
  (I386_ST0_REGNUM <= (regno) && (regno) < I386_AVX_NUM_REGS)

/* Does the current host support the GETREGS request?  */
int have_ptrace_getregs =
#ifdef HAVE_PTRACE_GETREGS
  1
#else
  0
#endif
;

/* Does the current host support the GETFPXREGS request?  The header
   file may or may not define it, and even if it is defined, the
   kernel will return EIO if it's running on a pre-SSE processor.

   My instinct is to attach this to some architecture- or
   target-specific data structure, but really, a particular GDB
   process can only run on top of one kernel at a time.  So it's okay
   for this to be a simple variable.  */
int have_ptrace_getfpxregs =
#ifdef HAVE_PTRACE_GETFPXREGS
  -1
#else
  0
#endif
;


/* Accessing registers through the U area, one at a time.  */

/* Fetch one register.  */

static void
fetch_register (struct regcache *regcache, int regno)
{
  int tid;
  int val;

  gdb_assert (!have_ptrace_getregs);
  if (i386_linux_gregset_reg_offset[regno] == -1)
    {
      regcache_raw_supply (regcache, regno, NULL);
      return;
    }

  /* GNU/Linux LWP ID's are process ID's.  */
  tid = TIDGET (inferior_ptid);
  if (tid == 0)
    tid = PIDGET (inferior_ptid); /* Not a threaded program.  */

  errno = 0;
  val = ptrace (PTRACE_PEEKUSER, tid,
		i386_linux_gregset_reg_offset[regno], 0);
  if (errno != 0)
    error (_("Couldn't read register %s (#%d): %s."), 
	   gdbarch_register_name (get_regcache_arch (regcache), regno),
	   regno, safe_strerror (errno));

  regcache_raw_supply (regcache, regno, &val);
}

/* Store one register. */

static void
store_register (const struct regcache *regcache, int regno)
{
  int tid;
  int val;

  gdb_assert (!have_ptrace_getregs);
  if (i386_linux_gregset_reg_offset[regno] == -1)
    return;

  /* GNU/Linux LWP ID's are process ID's.  */
  tid = TIDGET (inferior_ptid);
  if (tid == 0)
    tid = PIDGET (inferior_ptid); /* Not a threaded program.  */

  errno = 0;
  regcache_raw_collect (regcache, regno, &val);
  ptrace (PTRACE_POKEUSER, tid,
	  i386_linux_gregset_reg_offset[regno], val);
  if (errno != 0)
    error (_("Couldn't write register %s (#%d): %s."),
	   gdbarch_register_name (get_regcache_arch (regcache), regno),
	   regno, safe_strerror (errno));
}


/* Transfering the general-purpose registers between GDB, inferiors
   and core files.  */

/* Fill GDB's register array with the general-purpose register values
   in *GREGSETP.  */

void
supply_gregset (struct regcache *regcache, const elf_gregset_t *gregsetp)
{
  const gdb_byte *regp = (const gdb_byte *) gregsetp;
  int i;

  for (i = 0; i < I386_NUM_GREGS; i++)
    regcache_raw_supply (regcache, i,
			 regp + i386_linux_gregset_reg_offset[i]);

  if (I386_LINUX_ORIG_EAX_REGNUM
	< gdbarch_num_regs (get_regcache_arch (regcache)))
    regcache_raw_supply (regcache, I386_LINUX_ORIG_EAX_REGNUM,
			  regp + i386_linux_gregset_reg_offset[I386_LINUX_ORIG_EAX_REGNUM]);
}

/* Fill register REGNO (if it is a general-purpose register) in
   *GREGSETPS with the value in GDB's register array.  If REGNO is -1,
   do this for all registers.  */

void
fill_gregset (const struct regcache *regcache,
	      elf_gregset_t *gregsetp, int regno)
{
  gdb_byte *regp = (gdb_byte *) gregsetp;
  int i;

  for (i = 0; i < I386_NUM_GREGS; i++)
    if (regno == -1 || regno == i)
      regcache_raw_collect (regcache, i,
			    regp + i386_linux_gregset_reg_offset[i]);

  if ((regno == -1 || regno == I386_LINUX_ORIG_EAX_REGNUM)
      && I386_LINUX_ORIG_EAX_REGNUM
	   < gdbarch_num_regs (get_regcache_arch (regcache)))
    regcache_raw_collect (regcache, I386_LINUX_ORIG_EAX_REGNUM,
			  regp + i386_linux_gregset_reg_offset[I386_LINUX_ORIG_EAX_REGNUM]);
}

#ifdef HAVE_PTRACE_GETREGS

/* Fetch all general-purpose registers from process/thread TID and
   store their values in GDB's register array.  */

static void
fetch_regs (struct regcache *regcache, int tid)
{
  elf_gregset_t regs;
  elf_gregset_t *regs_p = &regs;

  if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
    {
      if (errno == EIO)
	{
	  /* The kernel we're running on doesn't support the GETREGS
             request.  Reset `have_ptrace_getregs'.  */
	  have_ptrace_getregs = 0;
	  return;
	}

      perror_with_name (_("Couldn't get registers"));
    }

  supply_gregset (regcache, (const elf_gregset_t *) regs_p);
}

/* Store all valid general-purpose registers in GDB's register array
   into the process/thread specified by TID.  */

static void
store_regs (const struct regcache *regcache, int tid, int regno)
{
  elf_gregset_t regs;

  if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
    perror_with_name (_("Couldn't get registers"));

  fill_gregset (regcache, &regs, regno);
  
  if (ptrace (PTRACE_SETREGS, tid, 0, (int) &regs) < 0)
    perror_with_name (_("Couldn't write registers"));
}

#else

static void fetch_regs (struct regcache *regcache, int tid) {}
static void store_regs (const struct regcache *regcache, int tid, int regno) {}

#endif


/* Transfering floating-point registers between GDB, inferiors and cores.  */

/* Fill GDB's register array with the floating-point register values in
   *FPREGSETP.  */

void 
supply_fpregset (struct regcache *regcache, const elf_fpregset_t *fpregsetp)
{
  i387_supply_fsave (regcache, -1, fpregsetp);
}

/* Fill register REGNO (if it is a floating-point register) in
   *FPREGSETP with the value in GDB's register array.  If REGNO is -1,
   do this for all registers.  */

void
fill_fpregset (const struct regcache *regcache,
	       elf_fpregset_t *fpregsetp, int regno)
{
  i387_collect_fsave (regcache, regno, fpregsetp);
}

#ifdef HAVE_PTRACE_GETREGS

/* Fetch all floating-point registers from process/thread TID and store
   thier values in GDB's register array.  */

static void
fetch_fpregs (struct regcache *regcache, int tid)
{
  elf_fpregset_t fpregs;

  if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
    perror_with_name (_("Couldn't get floating point status"));

  supply_fpregset (regcache, (const elf_fpregset_t *) &fpregs);
}

/* Store all valid floating-point registers in GDB's register array
   into the process/thread specified by TID.  */

static void
store_fpregs (const struct regcache *regcache, int tid, int regno)
{
  elf_fpregset_t fpregs;

  if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
    perror_with_name (_("Couldn't get floating point status"));

  fill_fpregset (regcache, &fpregs, regno);

  if (ptrace (PTRACE_SETFPREGS, tid, 0, (int) &fpregs) < 0)
    perror_with_name (_("Couldn't write floating point status"));
}

#else

static void fetch_fpregs (struct regcache *regcache, int tid) {}
static void store_fpregs (const struct regcache *regcache, int tid, int regno) {}

#endif


/* Transfering floating-point and SSE registers to and from GDB.  */

/* Fetch all registers covered by the PTRACE_GETREGSET request from
   process/thread TID and store their values in GDB's register array.
   Return non-zero if successful, zero otherwise.  */

static int
fetch_xstateregs (struct regcache *regcache, int tid)
{
  char xstateregs[I386_XSTATE_MAX_SIZE];
  struct iovec iov;

  if (!have_ptrace_getregset)
    return 0;

  iov.iov_base = xstateregs;
  iov.iov_len = sizeof(xstateregs);
  if (ptrace (PTRACE_GETREGSET, tid, (unsigned int) NT_X86_XSTATE,
	      &iov) < 0)
    perror_with_name (_("Couldn't read extended state status"));

  i387_supply_xsave (regcache, -1, xstateregs);
  return 1;
}

/* Store all valid registers in GDB's register array covered by the
   PTRACE_SETREGSET request into the process/thread specified by TID.
   Return non-zero if successful, zero otherwise.  */

static int
store_xstateregs (const struct regcache *regcache, int tid, int regno)
{
  char xstateregs[I386_XSTATE_MAX_SIZE];
  struct iovec iov;

  if (!have_ptrace_getregset)
    return 0;
  
  iov.iov_base = xstateregs;
  iov.iov_len = sizeof(xstateregs);
  if (ptrace (PTRACE_GETREGSET, tid, (unsigned int) NT_X86_XSTATE,
	      &iov) < 0)
    perror_with_name (_("Couldn't read extended state status"));

  i387_collect_xsave (regcache, regno, xstateregs, 0);

  if (ptrace (PTRACE_SETREGSET, tid, (unsigned int) NT_X86_XSTATE,
	      (int) &iov) < 0)
    perror_with_name (_("Couldn't write extended state status"));

  return 1;
}

#ifdef HAVE_PTRACE_GETFPXREGS

/* Fetch all registers covered by the PTRACE_GETFPXREGS request from
   process/thread TID and store their values in GDB's register array.
   Return non-zero if successful, zero otherwise.  */

static int
fetch_fpxregs (struct regcache *regcache, int tid)
{
  elf_fpxregset_t fpxregs;

  if (! have_ptrace_getfpxregs)
    return 0;

  if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
    {
      if (errno == EIO)
	{
	  have_ptrace_getfpxregs = 0;
	  return 0;
	}

      perror_with_name (_("Couldn't read floating-point and SSE registers"));
    }

  i387_supply_fxsave (regcache, -1, (const elf_fpxregset_t *) &fpxregs);
  return 1;
}

/* Store all valid registers in GDB's register array covered by the
   PTRACE_SETFPXREGS request into the process/thread specified by TID.
   Return non-zero if successful, zero otherwise.  */

static int
store_fpxregs (const struct regcache *regcache, int tid, int regno)
{
  elf_fpxregset_t fpxregs;

  if (! have_ptrace_getfpxregs)
    return 0;
  
  if (ptrace (PTRACE_GETFPXREGS, tid, 0, &fpxregs) == -1)
    {
      if (errno == EIO)
	{
	  have_ptrace_getfpxregs = 0;
	  return 0;
	}

      perror_with_name (_("Couldn't read floating-point and SSE registers"));
    }

  i387_collect_fxsave (regcache, regno, &fpxregs);

  if (ptrace (PTRACE_SETFPXREGS, tid, 0, &fpxregs) == -1)
    perror_with_name (_("Couldn't write floating-point and SSE registers"));

  return 1;
}

#else

static int fetch_fpxregs (struct regcache *regcache, int tid) { return 0; }
static int store_fpxregs (const struct regcache *regcache, int tid, int regno) { return 0; }

#endif /* HAVE_PTRACE_GETFPXREGS */


/* Transferring arbitrary registers between GDB and inferior.  */

/* Fetch register REGNO from the child process.  If REGNO is -1, do
   this for all registers (including the floating point and SSE
   registers).  */

static void
i386_linux_fetch_inferior_registers (struct target_ops *ops,
				     struct regcache *regcache, int regno)
{
  int tid;

  /* Use the old method of peeking around in `struct user' if the
     GETREGS request isn't available.  */
  if (!have_ptrace_getregs)
    {
      int i;

      for (i = 0; i < gdbarch_num_regs (get_regcache_arch (regcache)); i++)
	if (regno == -1 || regno == i)
	  fetch_register (regcache, i);

      return;
    }

  /* GNU/Linux LWP ID's are process ID's.  */
  tid = TIDGET (inferior_ptid);
  if (tid == 0)
    tid = PIDGET (inferior_ptid); /* Not a threaded program.  */

  /* Use the PTRACE_GETFPXREGS request whenever possible, since it
     transfers more registers in one system call, and we'll cache the
     results.  But remember that fetch_fpxregs can fail, and return
     zero.  */
  if (regno == -1)
    {
      fetch_regs (regcache, tid);

      /* The call above might reset `have_ptrace_getregs'.  */
      if (!have_ptrace_getregs)
	{
	  i386_linux_fetch_inferior_registers (ops, regcache, regno);
	  return;
	}

      if (fetch_xstateregs (regcache, tid))
	return;
      if (fetch_fpxregs (regcache, tid))
	return;
      fetch_fpregs (regcache, tid);
      return;
    }

  if (GETREGS_SUPPLIES (regno))
    {
      fetch_regs (regcache, tid);
      return;
    }

  if (GETXSTATEREGS_SUPPLIES (regno))
    {
      if (fetch_xstateregs (regcache, tid))
	return;
    }

  if (GETFPXREGS_SUPPLIES (regno))
    {
      if (fetch_fpxregs (regcache, tid))
	return;

      /* Either our processor or our kernel doesn't support the SSE
	 registers, so read the FP registers in the traditional way,
	 and fill the SSE registers with dummy values.  It would be
	 more graceful to handle differences in the register set using
	 gdbarch.  Until then, this will at least make things work
	 plausibly.  */
      fetch_fpregs (regcache, tid);
      return;
    }

  internal_error (__FILE__, __LINE__,
		  _("Got request for bad register number %d."), regno);
}

/* Store register REGNO back into the child process.  If REGNO is -1,
   do this for all registers (including the floating point and SSE
   registers).  */
static void
i386_linux_store_inferior_registers (struct target_ops *ops,
				     struct regcache *regcache, int regno)
{
  int tid;

  /* Use the old method of poking around in `struct user' if the
     SETREGS request isn't available.  */
  if (!have_ptrace_getregs)
    {
      int i;

      for (i = 0; i < gdbarch_num_regs (get_regcache_arch (regcache)); i++)
	if (regno == -1 || regno == i)
	  store_register (regcache, i);

      return;
    }

  /* GNU/Linux LWP ID's are process ID's.  */
  tid = TIDGET (inferior_ptid);
  if (tid == 0)
    tid = PIDGET (inferior_ptid); /* Not a threaded program.  */

  /* Use the PTRACE_SETFPXREGS requests whenever possible, since it
     transfers more registers in one system call.  But remember that
     store_fpxregs can fail, and return zero.  */
  if (regno == -1)
    {
      store_regs (regcache, tid, regno);
      if (store_xstateregs (regcache, tid, regno))
	return;
      if (store_fpxregs (regcache, tid, regno))
	return;
      store_fpregs (regcache, tid, regno);
      return;
    }

  if (GETREGS_SUPPLIES (regno))
    {
      store_regs (regcache, tid, regno);
      return;
    }

  if (GETXSTATEREGS_SUPPLIES (regno))
    {
      if (store_xstateregs (regcache, tid, regno))
	return;
    }

  if (GETFPXREGS_SUPPLIES (regno))
    {
      if (store_fpxregs (regcache, tid, regno))
	return;

      /* Either our processor or our kernel doesn't support the SSE
	 registers, so just write the FP registers in the traditional
	 way.  */
      store_fpregs (regcache, tid, regno);
      return;
    }

  internal_error (__FILE__, __LINE__,
		  _("Got request to store bad register number %d."), regno);
}


/* Support for debug registers.  */

static unsigned long i386_linux_dr[DR_CONTROL + 1];

/* Get debug register REGNUM value from only the one LWP of PTID.  */

static unsigned long
i386_linux_dr_get (ptid_t ptid, int regnum)
{
  int tid;
  unsigned long value;

  tid = TIDGET (ptid);
  if (tid == 0)
    tid = PIDGET (ptid);

  /* FIXME: kettenis/2001-03-27: Calling perror_with_name if the
     ptrace call fails breaks debugging remote targets.  The correct
     way to fix this is to add the hardware breakpoint and watchpoint
     stuff to the target vector.  For now, just return zero if the
     ptrace call fails.  */
  errno = 0;
  value = ptrace (PTRACE_PEEKUSER, tid,
		  offsetof (struct user, u_debugreg[regnum]), 0);
  if (errno != 0)
#if 0
    perror_with_name (_("Couldn't read debug register"));
#else
    return 0;
#endif

  return value;
}

/* Set debug register REGNUM to VALUE in only the one LWP of PTID.  */

static void
i386_linux_dr_set (ptid_t ptid, int regnum, unsigned long value)
{
  int tid;

  tid = TIDGET (ptid);
  if (tid == 0)
    tid = PIDGET (ptid);

  errno = 0;
  ptrace (PTRACE_POKEUSER, tid,
	  offsetof (struct user, u_debugreg[regnum]), value);
  if (errno != 0)
    perror_with_name (_("Couldn't write debug register"));
}

/* Set DR_CONTROL to ADDR in all LWPs of LWP_LIST.  */

static void
i386_linux_dr_set_control (unsigned long control)
{
  struct lwp_info *lp;
  ptid_t ptid;

  i386_linux_dr[DR_CONTROL] = control;
  ALL_LWPS (lp, ptid)
    i386_linux_dr_set (ptid, DR_CONTROL, control);
}

/* Set address REGNUM (zero based) to ADDR in all LWPs of LWP_LIST.  */

static void
i386_linux_dr_set_addr (int regnum, CORE_ADDR addr)
{
  struct lwp_info *lp;
  ptid_t ptid;

  gdb_assert (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR);

  i386_linux_dr[DR_FIRSTADDR + regnum] = addr;
  ALL_LWPS (lp, ptid)
    i386_linux_dr_set (ptid, DR_FIRSTADDR + regnum, addr);
}

/* Set address REGNUM (zero based) to zero in all LWPs of LWP_LIST.  */

static void
i386_linux_dr_reset_addr (int regnum)
{
  i386_linux_dr_set_addr (regnum, 0);
}

/* Get DR_STATUS from only the one LWP of INFERIOR_PTID.  */

static unsigned long
i386_linux_dr_get_status (void)
{
  return i386_linux_dr_get (inferior_ptid, DR_STATUS);
}

/* Unset MASK bits in DR_STATUS in all LWPs of LWP_LIST.  */

static void
i386_linux_dr_unset_status (unsigned long mask)
{
  struct lwp_info *lp;
  ptid_t ptid;

  ALL_LWPS (lp, ptid)
    {
      unsigned long value;
      
      value = i386_linux_dr_get (ptid, DR_STATUS);
      value &= ~mask;
      i386_linux_dr_set (ptid, DR_STATUS, value);
    }
}

static void
i386_linux_new_thread (ptid_t ptid)
{
  int i;

  for (i = DR_FIRSTADDR; i <= DR_LASTADDR; i++)
    i386_linux_dr_set (ptid, i, i386_linux_dr[i]);

  i386_linux_dr_set (ptid, DR_CONTROL, i386_linux_dr[DR_CONTROL]);
}


/* Called by libthread_db.  Returns a pointer to the thread local
   storage (or its descriptor).  */

ps_err_e
ps_get_thread_area (const struct ps_prochandle *ph, 
		    lwpid_t lwpid, int idx, void **base)
{
  /* NOTE: cagney/2003-08-26: The definition of this buffer is found
     in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
     4 byte integers in size: `entry_number', `base_addr', `limit',
     and a bunch of status bits.

     The values returned by this ptrace call should be part of the
     regcache buffer, and ps_get_thread_area should channel its
     request through the regcache.  That way remote targets could
     provide the value using the remote protocol and not this direct
     call.

     Is this function needed?  I'm guessing that the `base' is the
     address of a a descriptor that libthread_db uses to find the
     thread local address base that GDB needs.  Perhaps that
     descriptor is defined by the ABI.  Anyway, given that
     libthread_db calls this function without prompting (gdb
     requesting tls base) I guess it needs info in there anyway.  */
  unsigned int desc[4];
  gdb_assert (sizeof (int) == 4);

#ifndef PTRACE_GET_THREAD_AREA
#define PTRACE_GET_THREAD_AREA 25
#endif

  if (ptrace (PTRACE_GET_THREAD_AREA, lwpid,
	      (void *) idx, (unsigned long) &desc) < 0)
    return PS_ERR;

  *(int *)base = desc[1];
  return PS_OK;
}


/* The instruction for a GNU/Linux system call is:
       int $0x80
   or 0xcd 0x80.  */

static const unsigned char linux_syscall[] = { 0xcd, 0x80 };

#define LINUX_SYSCALL_LEN (sizeof linux_syscall)

/* The system call number is stored in the %eax register.  */
#define LINUX_SYSCALL_REGNUM I386_EAX_REGNUM

/* We are specifically interested in the sigreturn and rt_sigreturn
   system calls.  */

#ifndef SYS_sigreturn
#define SYS_sigreturn		0x77
#endif
#ifndef SYS_rt_sigreturn
#define SYS_rt_sigreturn	0xad
#endif

/* Offset to saved processor flags, from <asm/sigcontext.h>.  */
#define LINUX_SIGCONTEXT_EFLAGS_OFFSET (64)

/* Resume execution of the inferior process.
   If STEP is nonzero, single-step it.
   If SIGNAL is nonzero, give it that signal.  */

static void
i386_linux_resume (struct target_ops *ops,
		   ptid_t ptid, int step, enum target_signal signal)
{
  int pid = PIDGET (ptid);

  int request;

  if (catch_syscall_enabled () > 0)
   request = PTRACE_SYSCALL;
  else
    request = PTRACE_CONT;

  if (step)
    {
      struct regcache *regcache = get_thread_regcache (pid_to_ptid (pid));
      struct gdbarch *gdbarch = get_regcache_arch (regcache);
      enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
      ULONGEST pc;
      gdb_byte buf[LINUX_SYSCALL_LEN];

      request = PTRACE_SINGLESTEP;

      regcache_cooked_read_unsigned (regcache,
				     gdbarch_pc_regnum (gdbarch), &pc);

      /* Returning from a signal trampoline is done by calling a
         special system call (sigreturn or rt_sigreturn, see
         i386-linux-tdep.c for more information).  This system call
         restores the registers that were saved when the signal was
         raised, including %eflags.  That means that single-stepping
         won't work.  Instead, we'll have to modify the signal context
         that's about to be restored, and set the trace flag there.  */

      /* First check if PC is at a system call.  */
      if (target_read_memory (pc, buf, LINUX_SYSCALL_LEN) == 0
	  && memcmp (buf, linux_syscall, LINUX_SYSCALL_LEN) == 0)
	{
	  ULONGEST syscall;
	  regcache_cooked_read_unsigned (regcache,
					 LINUX_SYSCALL_REGNUM, &syscall);

	  /* Then check the system call number.  */
	  if (syscall == SYS_sigreturn || syscall == SYS_rt_sigreturn)
	    {
	      ULONGEST sp, addr;
	      unsigned long int eflags;

	      regcache_cooked_read_unsigned (regcache, I386_ESP_REGNUM, &sp);
	      if (syscall == SYS_rt_sigreturn)
		addr = read_memory_integer (sp + 8, 4, byte_order) + 20;
	      else
		addr = sp;

	      /* Set the trace flag in the context that's about to be
                 restored.  */
	      addr += LINUX_SIGCONTEXT_EFLAGS_OFFSET;
	      read_memory (addr, (gdb_byte *) &eflags, 4);
	      eflags |= 0x0100;
	      write_memory (addr, (gdb_byte *) &eflags, 4);
	    }
	}
    }

  if (ptrace (request, pid, 0, target_signal_to_host (signal)) == -1)
    perror_with_name (("ptrace"));
}

static void (*super_post_startup_inferior) (ptid_t ptid);

static void
i386_linux_child_post_startup_inferior (ptid_t ptid)
{
  i386_cleanup_dregs ();
  super_post_startup_inferior (ptid);
}

/* Get Linux/x86 target description from running target.  */

static const struct target_desc *
i386_linux_read_description (struct target_ops *ops)
{
  int tid;
  static uint64_t xcr0;

  /* GNU/Linux LWP ID's are process ID's.  */
  tid = TIDGET (inferior_ptid);
  if (tid == 0)
    tid = PIDGET (inferior_ptid); /* Not a threaded program.  */

#ifdef HAVE_PTRACE_GETFPXREGS
  if (have_ptrace_getfpxregs == -1)
    {
      elf_fpxregset_t fpxregs;

      if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
	{
	  have_ptrace_getfpxregs = 0;
	  have_ptrace_getregset = 0;
	  return tdesc_i386_mmx_linux;
	}
    }
#endif

  if (have_ptrace_getregset == -1)
    {
      uint64_t xstateregs[(I386_XSTATE_SSE_SIZE / sizeof (uint64_t))];
      struct iovec iov;

      iov.iov_base = xstateregs;
      iov.iov_len = sizeof (xstateregs);

      /* Check if PTRACE_GETREGSET works.  */
      if (ptrace (PTRACE_GETREGSET, tid, (unsigned int) NT_X86_XSTATE,
		  &iov) < 0)
	have_ptrace_getregset = 0;
      else
	{
	  have_ptrace_getregset = 1;

	  /* Get XCR0 from XSAVE extended state.  */
	  xcr0 = xstateregs[(I386_LINUX_XSAVE_XCR0_OFFSET
			     / sizeof (long long))];
	}
    }

  /* Check the native XCR0 only if PTRACE_GETREGSET is available.  */
  if (have_ptrace_getregset
      && (xcr0 & I386_XSTATE_AVX_MASK) == I386_XSTATE_AVX_MASK)
    return tdesc_i386_avx_linux;
  else
    return tdesc_i386_linux;
}

void
_initialize_i386_linux_nat (void)
{
  struct target_ops *t;

  /* Fill in the generic GNU/Linux methods.  */
  t = linux_target ();

  i386_use_watchpoints (t);

  i386_dr_low.set_control = i386_linux_dr_set_control;
  i386_dr_low.set_addr = i386_linux_dr_set_addr;
  i386_dr_low.reset_addr = i386_linux_dr_reset_addr;
  i386_dr_low.get_status = i386_linux_dr_get_status;
  i386_dr_low.unset_status = i386_linux_dr_unset_status;
  i386_set_debug_register_length (4);

  /* Override the default ptrace resume method.  */
  t->to_resume = i386_linux_resume;

  /* Override the GNU/Linux inferior startup hook.  */
  super_post_startup_inferior = t->to_post_startup_inferior;
  t->to_post_startup_inferior = i386_linux_child_post_startup_inferior;

  /* Add our register access methods.  */
  t->to_fetch_registers = i386_linux_fetch_inferior_registers;
  t->to_store_registers = i386_linux_store_inferior_registers;

  t->to_read_description = i386_linux_read_description;

  /* Register the target.  */
  linux_nat_add_target (t);
  linux_nat_set_new_thread (t, i386_linux_new_thread);
}