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[/] [openrisc/] [trunk/] [gnu-src/] [gdb-7.1/] [gdb/] [linux-fork.c] - Blame information for rev 227

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1 227 jeremybenn
/* GNU/Linux native-dependent code for debugging multiple forks.
2
 
3
   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010
4
   Free Software Foundation, Inc.
5
 
6
   This file is part of GDB.
7
 
8
   This program is free software; you can redistribute it and/or modify
9
   it under the terms of the GNU General Public License as published by
10
   the Free Software Foundation; either version 3 of the License, or
11
   (at your option) any later version.
12
 
13
   This program is distributed in the hope that it will be useful,
14
   but WITHOUT ANY WARRANTY; without even the implied warranty of
15
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16
   GNU General Public License for more details.
17
 
18
   You should have received a copy of the GNU General Public License
19
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
20
 
21
#include "defs.h"
22
#include "arch-utils.h"
23
#include "inferior.h"
24
#include "regcache.h"
25
#include "gdbcmd.h"
26
#include "infcall.h"
27
#include "objfiles.h"
28
#include "gdb_assert.h"
29
#include "gdb_string.h"
30
#include "linux-fork.h"
31
#include "linux-nat.h"
32
 
33
#include <sys/ptrace.h>
34
#include "gdb_wait.h"
35
#include <sys/param.h>
36
#include "gdb_dirent.h"
37
#include <ctype.h>
38
 
39
struct fork_info *fork_list;
40
static int highest_fork_num;
41
 
42
/* Prevent warning from -Wmissing-prototypes.  */
43
extern void _initialize_linux_fork (void);
44
 
45
/* Fork list data structure:  */
46
struct fork_info
47
{
48
  struct fork_info *next;
49
  ptid_t ptid;
50
  int num;                      /* Convenient handle (GDB fork id) */
51
  struct regcache *savedregs;   /* Convenient for info fork, saves
52
                                   having to actually switch contexts.  */
53
  int clobber_regs;             /* True if we should restore saved regs.  */
54
  off_t *filepos;               /* Set of open file descriptors' offsets.  */
55
  int maxfd;
56
};
57
 
58
/* Fork list methods:  */
59
 
60
int
61
forks_exist_p (void)
62
{
63
  return (fork_list != NULL);
64
}
65
 
66
/* Add a fork to the internal fork list.  */
67
 
68
struct fork_info *
69
add_fork (pid_t pid)
70
{
71
  struct fork_info *fp;
72
 
73
  if (fork_list == NULL && pid != PIDGET (inferior_ptid))
74
    {
75
      /* Special case -- if this is the first fork in the list
76
         (the list is hitherto empty), and if this new fork is
77
         NOT the current inferior_ptid, then add inferior_ptid
78
         first, as a special zeroeth fork id.  */
79
      highest_fork_num = -1;
80
      add_fork (PIDGET (inferior_ptid));        /* safe recursion */
81
    }
82
 
83
  fp = XZALLOC (struct fork_info);
84
  fp->ptid = ptid_build (pid, pid, 0);
85
  fp->num = ++highest_fork_num;
86
  fp->next = fork_list;
87
  fork_list = fp;
88
  return fp;
89
}
90
 
91
static void
92
free_fork (struct fork_info *fp)
93
{
94
  /* Notes on step-resume breakpoints: since this is a concern for
95
     threads, let's convince ourselves that it's not a concern for
96
     forks.  There are two ways for a fork_info to be created.  First,
97
     by the checkpoint command, in which case we're at a gdb prompt
98
     and there can't be any step-resume breakpoint.  Second, by a fork
99
     in the user program, in which case we *may* have stepped into the
100
     fork call, but regardless of whether we follow the parent or the
101
     child, we will return to the same place and the step-resume
102
     breakpoint, if any, will take care of itself as usual.  And
103
     unlike threads, we do not save a private copy of the step-resume
104
     breakpoint -- so we're OK.  */
105
 
106
  if (fp)
107
    {
108
      if (fp->savedregs)
109
        regcache_xfree (fp->savedregs);
110
      if (fp->filepos)
111
        xfree (fp->filepos);
112
      xfree (fp);
113
    }
114
}
115
 
116
static void
117
delete_fork (ptid_t ptid)
118
{
119
  struct fork_info *fp, *fpprev;
120
 
121
  fpprev = NULL;
122
 
123
  for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
124
    if (ptid_equal (fp->ptid, ptid))
125
      break;
126
 
127
  if (!fp)
128
    return;
129
 
130
  if (fpprev)
131
    fpprev->next = fp->next;
132
  else
133
    fork_list = fp->next;
134
 
135
  free_fork (fp);
136
 
137
  /* Special case: if there is now only one process in the list,
138
     and if it is (hopefully!) the current inferior_ptid, then
139
     remove it, leaving the list empty -- we're now down to the
140
     default case of debugging a single process.  */
141
  if (fork_list != NULL && fork_list->next == NULL &&
142
      ptid_equal (fork_list->ptid, inferior_ptid))
143
    {
144
      /* Last fork -- delete from list and handle as solo process
145
         (should be a safe recursion).  */
146
      delete_fork (inferior_ptid);
147
    }
148
}
149
 
150
/* Find a fork_info by matching PTID.  */
151
static struct fork_info *
152
find_fork_ptid (ptid_t ptid)
153
{
154
  struct fork_info *fp;
155
 
156
  for (fp = fork_list; fp; fp = fp->next)
157
    if (ptid_equal (fp->ptid, ptid))
158
      return fp;
159
 
160
  return NULL;
161
}
162
 
163
/* Find a fork_info by matching ID.  */
164
static struct fork_info *
165
find_fork_id (int num)
166
{
167
  struct fork_info *fp;
168
 
169
  for (fp = fork_list; fp; fp = fp->next)
170
    if (fp->num == num)
171
      return fp;
172
 
173
  return NULL;
174
}
175
 
176
/* Find a fork_info by matching pid.  */
177
extern struct fork_info *
178
find_fork_pid (pid_t pid)
179
{
180
  struct fork_info *fp;
181
 
182
  for (fp = fork_list; fp; fp = fp->next)
183
    if (pid == ptid_get_pid (fp->ptid))
184
      return fp;
185
 
186
  return NULL;
187
}
188
 
189
static ptid_t
190
fork_id_to_ptid (int num)
191
{
192
  struct fork_info *fork = find_fork_id (num);
193
  if (fork)
194
    return fork->ptid;
195
  else
196
    return pid_to_ptid (-1);
197
}
198
 
199
static void
200
init_fork_list (void)
201
{
202
  struct fork_info *fp, *fpnext;
203
 
204
  if (!fork_list)
205
    return;
206
 
207
  for (fp = fork_list; fp; fp = fpnext)
208
    {
209
      fpnext = fp->next;
210
      free_fork (fp);
211
    }
212
 
213
  fork_list = NULL;
214
}
215
 
216
/* Fork list <-> gdb interface.  */
217
 
218
/* Utility function for fork_load/fork_save.
219
   Calls lseek in the (current) inferior process.  */
220
 
221
static off_t
222
call_lseek (int fd, off_t offset, int whence)
223
{
224
  char exp[80];
225
 
226
  snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",
227
            fd, (long) offset, whence);
228
  return (off_t) parse_and_eval_long (&exp[0]);
229
}
230
 
231
/* Load infrun state for the fork PTID.  */
232
 
233
static void
234
fork_load_infrun_state (struct fork_info *fp)
235
{
236
  extern void nullify_last_target_wait_ptid ();
237
  int i;
238
 
239
  linux_nat_switch_fork (fp->ptid);
240
 
241
  if (fp->savedregs && fp->clobber_regs)
242
    regcache_cpy (get_current_regcache (), fp->savedregs);
243
 
244
  registers_changed ();
245
  reinit_frame_cache ();
246
 
247
  stop_pc = regcache_read_pc (get_current_regcache ());
248
  nullify_last_target_wait_ptid ();
249
 
250
  /* Now restore the file positions of open file descriptors.  */
251
  if (fp->filepos)
252
    {
253
      for (i = 0; i <= fp->maxfd; i++)
254
        if (fp->filepos[i] != (off_t) -1)
255
          call_lseek (i, fp->filepos[i], SEEK_SET);
256
      /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
257
         this is native-only.  If it ever has to be cross, we'll have
258
         to rethink this.  */
259
    }
260
}
261
 
262
/* Save infrun state for the fork PTID.
263
   Exported for use by linux child_follow_fork.  */
264
 
265
static void
266
fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
267
{
268
  char path[MAXPATHLEN];
269
  struct dirent *de;
270
  DIR *d;
271
 
272
  if (fp->savedregs)
273
    regcache_xfree (fp->savedregs);
274
 
275
  fp->savedregs = regcache_dup (get_current_regcache ());
276
  fp->clobber_regs = clobber_regs;
277
 
278
  if (clobber_regs)
279
    {
280
      /* Now save the 'state' (file position) of all open file descriptors.
281
         Unfortunately fork does not take care of that for us...  */
282
      snprintf (path, MAXPATHLEN, "/proc/%ld/fd", (long) PIDGET (fp->ptid));
283
      if ((d = opendir (path)) != NULL)
284
        {
285
          long tmp;
286
 
287
          fp->maxfd = 0;
288
          while ((de = readdir (d)) != NULL)
289
            {
290
              /* Count open file descriptors (actually find highest
291
                 numbered).  */
292
              tmp = strtol (&de->d_name[0], NULL, 10);
293
              if (fp->maxfd < tmp)
294
                fp->maxfd = tmp;
295
            }
296
          /* Allocate array of file positions.  */
297
          fp->filepos = xrealloc (fp->filepos,
298
                                  (fp->maxfd + 1) * sizeof (*fp->filepos));
299
 
300
          /* Initialize to -1 (invalid).  */
301
          for (tmp = 0; tmp <= fp->maxfd; tmp++)
302
            fp->filepos[tmp] = -1;
303
 
304
          /* Now find actual file positions.  */
305
          rewinddir (d);
306
          while ((de = readdir (d)) != NULL)
307
            if (isdigit (de->d_name[0]))
308
              {
309
                tmp = strtol (&de->d_name[0], NULL, 10);
310
                fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
311
              }
312
          closedir (d);
313
        }
314
    }
315
}
316
 
317
/* Kill 'em all, let God sort 'em out...  */
318
 
319
void
320
linux_fork_killall (void)
321
{
322
  /* Walk list and kill every pid.  No need to treat the
323
     current inferior_ptid as special (we do not return a
324
     status for it) -- however any process may be a child
325
     or a parent, so may get a SIGCHLD from a previously
326
     killed child.  Wait them all out.  */
327
  struct fork_info *fp;
328
  pid_t pid, ret;
329
  int status;
330
 
331
  for (fp = fork_list; fp; fp = fp->next)
332
    {
333
      pid = PIDGET (fp->ptid);
334
      do {
335
        /* Use SIGKILL instead of PTRACE_KILL because the former works even
336
           if the thread is running, while the later doesn't.  */
337
        kill (pid, SIGKILL);
338
        ret = waitpid (pid, &status, 0);
339
        /* We might get a SIGCHLD instead of an exit status.  This is
340
         aggravated by the first kill above - a child has just
341
         died.  MVS comment cut-and-pasted from linux-nat.  */
342
      } while (ret == pid && WIFSTOPPED (status));
343
    }
344
  init_fork_list ();    /* Clear list, prepare to start fresh.  */
345
}
346
 
347
/* The current inferior_ptid has exited, but there are other viable
348
   forks to debug.  Delete the exiting one and context-switch to the
349
   first available.  */
350
 
351
void
352
linux_fork_mourn_inferior (void)
353
{
354
  /* Wait just one more time to collect the inferior's exit status.
355
     Do not check whether this succeeds though, since we may be
356
     dealing with a process that we attached to.  Such a process will
357
     only report its exit status to its original parent.  */
358
  int status;
359
 
360
  waitpid (ptid_get_pid (inferior_ptid), &status, 0);
361
 
362
  /* OK, presumably inferior_ptid is the one who has exited.
363
     We need to delete that one from the fork_list, and switch
364
     to the next available fork.  */
365
  delete_fork (inferior_ptid);
366
 
367
  /* There should still be a fork - if there's only one left,
368
     delete_fork won't remove it, because we haven't updated
369
     inferior_ptid yet.  */
370
  gdb_assert (fork_list);
371
 
372
  fork_load_infrun_state (fork_list);
373
  printf_filtered (_("[Switching to %s]\n"),
374
                   target_pid_to_str (inferior_ptid));
375
 
376
  /* If there's only one fork, switch back to non-fork mode.  */
377
  if (fork_list->next == NULL)
378
    delete_fork (inferior_ptid);
379
}
380
 
381
/* The current inferior_ptid is being detached, but there are other
382
   viable forks to debug.  Detach and delete it and context-switch to
383
   the first available.  */
384
 
385
void
386
linux_fork_detach (char *args, int from_tty)
387
{
388
  /* OK, inferior_ptid is the one we are detaching from.  We need to
389
     delete it from the fork_list, and switch to the next available
390
     fork.  */
391
 
392
  if (ptrace (PTRACE_DETACH, PIDGET (inferior_ptid), 0, 0))
393
    error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
394
 
395
  delete_fork (inferior_ptid);
396
 
397
  /* There should still be a fork - if there's only one left,
398
     delete_fork won't remove it, because we haven't updated
399
     inferior_ptid yet.  */
400
  gdb_assert (fork_list);
401
 
402
  fork_load_infrun_state (fork_list);
403
 
404
  if (from_tty)
405
    printf_filtered (_("[Switching to %s]\n"),
406
                     target_pid_to_str (inferior_ptid));
407
 
408
  /* If there's only one fork, switch back to non-fork mode.  */
409
  if (fork_list->next == NULL)
410
    delete_fork (inferior_ptid);
411
}
412
 
413
/* Fork list <-> user interface.  */
414
 
415
static void
416
delete_checkpoint_command (char *args, int from_tty)
417
{
418
  ptid_t ptid;
419
 
420
  if (!args || !*args)
421
    error (_("Requires argument (checkpoint id to delete)"));
422
 
423
  ptid = fork_id_to_ptid (parse_and_eval_long (args));
424
  if (ptid_equal (ptid, minus_one_ptid))
425
    error (_("No such checkpoint id, %s"), args);
426
 
427
  if (ptid_equal (ptid, inferior_ptid))
428
    error (_("\
429
Please switch to another checkpoint before deleting the current one"));
430
 
431
  if (ptrace (PTRACE_KILL, PIDGET (ptid), 0, 0))
432
    error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
433
 
434
  if (from_tty)
435
    printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
436
 
437
  delete_fork (ptid);
438
}
439
 
440
static void
441
detach_checkpoint_command (char *args, int from_tty)
442
{
443
  ptid_t ptid;
444
 
445
  if (!args || !*args)
446
    error (_("Requires argument (checkpoint id to detach)"));
447
 
448
  ptid = fork_id_to_ptid (parse_and_eval_long (args));
449
  if (ptid_equal (ptid, minus_one_ptid))
450
    error (_("No such checkpoint id, %s"), args);
451
 
452
  if (ptid_equal (ptid, inferior_ptid))
453
    error (_("\
454
Please switch to another checkpoint before detaching the current one"));
455
 
456
  if (ptrace (PTRACE_DETACH, PIDGET (ptid), 0, 0))
457
    error (_("Unable to detach %s"), target_pid_to_str (ptid));
458
 
459
  if (from_tty)
460
    printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
461
 
462
  delete_fork (ptid);
463
}
464
 
465
/* Print information about currently known checkpoints.  */
466
 
467
static void
468
info_checkpoints_command (char *arg, int from_tty)
469
{
470
  struct gdbarch *gdbarch = get_current_arch ();
471
  struct frame_info *cur_frame;
472
  struct symtab_and_line sal;
473
  struct symtab *cur_symtab;
474
  struct fork_info *fp;
475
  int cur_line;
476
  ULONGEST pc;
477
  int requested = -1;
478
  struct fork_info *printed = NULL;
479
 
480
  if (arg && *arg)
481
    requested = (int) parse_and_eval_long (arg);
482
 
483
  for (fp = fork_list; fp; fp = fp->next)
484
    {
485
      if (requested > 0 && fp->num != requested)
486
        continue;
487
 
488
      printed = fp;
489
      if (ptid_equal (fp->ptid, inferior_ptid))
490
        {
491
          printf_filtered ("* ");
492
          pc = regcache_read_pc (get_current_regcache ());
493
        }
494
      else
495
        {
496
          printf_filtered ("  ");
497
          pc = regcache_read_pc (fp->savedregs);
498
        }
499
      printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
500
      if (fp->num == 0)
501
        printf_filtered (_(" (main process)"));
502
      printf_filtered (_(" at "));
503
      fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
504
 
505
      sal = find_pc_line (pc, 0);
506
      if (sal.symtab)
507
        {
508
          char *tmp = strrchr (sal.symtab->filename, '/');
509
 
510
          if (tmp)
511
            printf_filtered (_(", file %s"), tmp + 1);
512
          else
513
            printf_filtered (_(", file %s"), sal.symtab->filename);
514
        }
515
      if (sal.line)
516
        printf_filtered (_(", line %d"), sal.line);
517
      if (!sal.symtab && !sal.line)
518
        {
519
          struct minimal_symbol *msym;
520
 
521
          msym = lookup_minimal_symbol_by_pc (pc);
522
          if (msym)
523
            printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym));
524
        }
525
 
526
      putchar_filtered ('\n');
527
    }
528
  if (printed == NULL)
529
    {
530
      if (requested > 0)
531
        printf_filtered (_("No checkpoint number %d.\n"), requested);
532
      else
533
        printf_filtered (_("No checkpoints.\n"));
534
    }
535
}
536
 
537
/* The PID of the process we're checkpointing.  */
538
static int checkpointing_pid = 0;
539
 
540
int
541
linux_fork_checkpointing_p (int pid)
542
{
543
  return (checkpointing_pid == pid);
544
}
545
 
546
static void
547
checkpoint_command (char *args, int from_tty)
548
{
549
  struct objfile *fork_objf;
550
  struct gdbarch *gdbarch;
551
  struct target_waitstatus last_target_waitstatus;
552
  ptid_t last_target_ptid;
553
  struct value *fork_fn = NULL, *ret;
554
  struct fork_info *fp;
555
  pid_t retpid;
556
  struct cleanup *old_chain;
557
  long i;
558
 
559
  /* Make the inferior fork, record its (and gdb's) state.  */
560
 
561
  if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)
562
    fork_fn = find_function_in_inferior ("fork", &fork_objf);
563
  if (!fork_fn)
564
    if (lookup_minimal_symbol ("_fork", NULL, NULL) != NULL)
565
      fork_fn = find_function_in_inferior ("fork", &fork_objf);
566
  if (!fork_fn)
567
    error (_("checkpoint: can't find fork function in inferior."));
568
 
569
  gdbarch = get_objfile_arch (fork_objf);
570
  ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
571
 
572
  /* Tell linux-nat.c that we're checkpointing this inferior.  */
573
  old_chain = make_cleanup_restore_integer (&checkpointing_pid);
574
  checkpointing_pid = PIDGET (inferior_ptid);
575
 
576
  ret = call_function_by_hand (fork_fn, 0, &ret);
577
  do_cleanups (old_chain);
578
  if (!ret)     /* Probably can't happen.  */
579
    error (_("checkpoint: call_function_by_hand returned null."));
580
 
581
  retpid = value_as_long (ret);
582
  get_last_target_status (&last_target_ptid, &last_target_waitstatus);
583
  if (from_tty)
584
    {
585
      int parent_pid;
586
 
587
      printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
588
                       (long) retpid);
589
      if (info_verbose)
590
        {
591
          parent_pid = ptid_get_lwp (last_target_ptid);
592
          if (parent_pid == 0)
593
            parent_pid = ptid_get_pid (last_target_ptid);
594
          printf_filtered (_("   gdb says parent = %ld.\n"),
595
                           (long) parent_pid);
596
        }
597
    }
598
 
599
  fp = find_fork_pid (retpid);
600
  if (!fp)
601
    error (_("Failed to find new fork"));
602
  fork_save_infrun_state (fp, 1);
603
}
604
 
605
static void
606
linux_fork_context (struct fork_info *newfp, int from_tty)
607
{
608
  /* Now we attempt to switch processes.  */
609
  struct fork_info *oldfp;
610
  ptid_t ptid;
611
  int id, i;
612
 
613
  gdb_assert (newfp != NULL);
614
 
615
  oldfp = find_fork_ptid (inferior_ptid);
616
  gdb_assert (oldfp != NULL);
617
 
618
  fork_save_infrun_state (oldfp, 1);
619
  remove_breakpoints ();
620
  fork_load_infrun_state (newfp);
621
  insert_breakpoints ();
622
 
623
  printf_filtered (_("Switching to %s\n"),
624
                   target_pid_to_str (inferior_ptid));
625
 
626
  print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC);
627
}
628
 
629
/* Switch inferior process (checkpoint) context, by checkpoint id.  */
630
static void
631
restart_command (char *args, int from_tty)
632
{
633
  struct fork_info *fp;
634
 
635
  if (!args || !*args)
636
    error (_("Requires argument (checkpoint id to restart)"));
637
 
638
  if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
639
    error (_("Not found: checkpoint id %s"), args);
640
 
641
  linux_fork_context (fp, from_tty);
642
}
643
 
644
void
645
_initialize_linux_fork (void)
646
{
647
  init_fork_list ();
648
 
649
  /* Checkpoint command: create a fork of the inferior process
650
     and set it aside for later debugging.  */
651
 
652
  add_com ("checkpoint", class_obscure, checkpoint_command, _("\
653
Fork a duplicate process (experimental)."));
654
 
655
  /* Restart command: restore the context of a specified checkpoint
656
     process.  */
657
 
658
  add_com ("restart", class_obscure, restart_command, _("\
659
restart <n>: restore program context from a checkpoint.\n\
660
Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
661
 
662
  /* Delete checkpoint command: kill the process and remove it from
663
     the fork list.  */
664
 
665
  add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\
666
Delete a checkpoint (experimental)."),
667
           &deletelist);
668
 
669
  /* Detach checkpoint command: release the process to run independently,
670
     and remove it from the fork list.  */
671
 
672
  add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\
673
Detach from a checkpoint (experimental)."),
674
           &detachlist);
675
 
676
  /* Info checkpoints command: list all forks/checkpoints
677
     currently under gdb's control.  */
678
 
679
  add_info ("checkpoints", info_checkpoints_command,
680
            _("IDs of currently known checkpoints."));
681
}

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