1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 51 Franklin Street, Fifth Floor,
20 Boston, MA 02110-1301, USA. */
27 #include "gdb_assert.h"
28 #include "gdb_string.h"
29 #include "linux-fork.h"
30 #include "linux-nat.h"
32 #include <sys/ptrace.h>
34 #include <sys/param.h>
38 struct fork_info
*fork_list
;
39 static int highest_fork_num
;
41 /* Prevent warning from -Wmissing-prototypes. */
42 extern void _initialize_linux_fork (void);
44 int detach_fork
= 1; /* Default behavior is to detach
45 newly forked processes (legacy). */
47 /* Fork list data structure: */
50 struct fork_info
*next
;
52 int num
; /* Convenient handle (GDB fork id) */
53 struct regcache
*savedregs
; /* Convenient for info fork, saves
54 having to actually switch contexts. */
55 int clobber_regs
; /* True if we should restore saved regs. */
56 ULONGEST pc
; /* PC for info fork. */
57 off_t
*filepos
; /* Set of open file descriptors' offsets. */
61 /* Fork list methods: */
66 return (fork_list
!= NULL
);
69 /* Add a fork to internal fork list.
70 Called from linux child_follow_fork. */
72 extern struct fork_info
*
77 if (fork_list
== NULL
&& pid
!= PIDGET (inferior_ptid
))
79 /* Special case -- if this is the first fork in the list
80 (the list is hitherto empty), and if this new fork is
81 NOT the current inferior_ptid, then add inferior_ptid
82 first, as a special zeroeth fork id. */
83 highest_fork_num
= -1;
84 add_fork (PIDGET (inferior_ptid
)); /* safe recursion */
87 fp
= XZALLOC (struct fork_info
);
88 fp
->ptid
= ptid_build (pid
, pid
, 0);
89 fp
->num
= ++highest_fork_num
;
96 free_fork (struct fork_info
*fp
)
98 /* Notes on step-resume breakpoints: since this is a concern for
99 threads, let's convince ourselves that it's not a concern for
100 forks. There are two ways for a fork_info to be created. First,
101 by the checkpoint command, in which case we're at a gdb prompt
102 and there can't be any step-resume breakpoint. Second, by a fork
103 in the user program, in which case we *may* have stepped into the
104 fork call, but regardless of whether we follow the parent or the
105 child, we will return to the same place and the step-resume
106 breakpoint, if any, will take care of itself as usual. And
107 unlike threads, we do not save a private copy of the step-resume
108 breakpoint -- so we're OK. */
113 regcache_xfree (fp
->savedregs
);
121 delete_fork (ptid_t ptid
)
123 struct fork_info
*fp
, *fpprev
;
127 for (fp
= fork_list
; fp
; fpprev
= fp
, fp
= fp
->next
)
128 if (ptid_equal (fp
->ptid
, ptid
))
135 fpprev
->next
= fp
->next
;
137 fork_list
= fp
->next
;
141 /* Special case: if there is now only one process in the list,
142 and if it is (hopefully!) the current inferior_ptid, then
143 remove it, leaving the list empty -- we're now down to the
144 default case of debugging a single process. */
145 if (fork_list
!= NULL
&& fork_list
->next
== NULL
&&
146 ptid_equal (fork_list
->ptid
, inferior_ptid
))
148 /* Last fork -- delete from list and handle as solo process
149 (should be a safe recursion). */
150 delete_fork (inferior_ptid
);
154 /* Find a fork_info by matching PTID. */
155 static struct fork_info
*
156 find_fork_ptid (ptid_t ptid
)
158 struct fork_info
*fp
;
160 for (fp
= fork_list
; fp
; fp
= fp
->next
)
161 if (ptid_equal (fp
->ptid
, ptid
))
167 /* Find a fork_info by matching ID. */
168 static struct fork_info
*
169 find_fork_id (int num
)
171 struct fork_info
*fp
;
173 for (fp
= fork_list
; fp
; fp
= fp
->next
)
180 /* Find a fork_info by matching pid. */
181 extern struct fork_info
*
182 find_fork_pid (pid_t pid
)
184 struct fork_info
*fp
;
186 for (fp
= fork_list
; fp
; fp
= fp
->next
)
187 if (pid
== ptid_get_pid (fp
->ptid
))
194 fork_id_to_ptid (int num
)
196 struct fork_info
*fork
= find_fork_id (num
);
200 return pid_to_ptid (-1);
204 init_fork_list (void)
206 struct fork_info
*fp
, *fpnext
;
211 for (fp
= fork_list
; fp
; fp
= fpnext
)
220 /* Fork list <-> gdb interface. */
222 /* Utility function for fork_load/fork_save.
223 Calls lseek in the (current) inferior process. */
226 call_lseek (int fd
, off_t offset
, int whence
)
230 snprintf (&exp
[0], sizeof (exp
), "lseek (%d, %ld, %d)",
231 fd
, (long) offset
, whence
);
232 return (off_t
) parse_and_eval_long (&exp
[0]);
235 /* Load infrun state for the fork PTID. */
238 fork_load_infrun_state (struct fork_info
*fp
)
240 extern void nullify_last_target_wait_ptid ();
243 inferior_ptid
= fp
->ptid
;
245 linux_nat_switch_fork (inferior_ptid
);
247 if (fp
->savedregs
&& fp
->clobber_regs
)
248 regcache_cpy (current_regcache
, fp
->savedregs
);
250 registers_changed ();
251 reinit_frame_cache ();
253 stop_pc
= read_pc ();
254 nullify_last_target_wait_ptid ();
256 /* Now restore the file positions of open file descriptors. */
259 for (i
= 0; i
<= fp
->maxfd
; i
++)
260 if (fp
->filepos
[i
] != (off_t
) -1)
261 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
262 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
263 this is native-only. If it ever has to be cross, we'll have
268 /* Save infrun state for the fork PTID.
269 Exported for use by linux child_follow_fork. */
272 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
274 char path
[MAXPATHLEN
];
279 regcache_xfree (fp
->savedregs
);
281 fp
->savedregs
= regcache_dup (current_regcache
);
282 fp
->clobber_regs
= clobber_regs
;
287 /* Now save the 'state' (file position) of all open file descriptors.
288 Unfortunately fork does not take care of that for us... */
289 snprintf (path
, MAXPATHLEN
, "/proc/%ld/fd", (long) PIDGET (fp
->ptid
));
290 if ((d
= opendir (path
)) != NULL
)
295 while ((de
= readdir (d
)) != NULL
)
297 /* Count open file descriptors (actually find highest
299 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
303 /* Allocate array of file positions. */
304 fp
->filepos
= xrealloc (fp
->filepos
,
305 (fp
->maxfd
+ 1) * sizeof (*fp
->filepos
));
307 /* Initialize to -1 (invalid). */
308 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
309 fp
->filepos
[tmp
] = -1;
311 /* Now find actual file positions. */
313 while ((de
= readdir (d
)) != NULL
)
314 if (isdigit (de
->d_name
[0]))
316 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
317 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
324 /* Kill 'em all, let God sort 'em out... */
327 linux_fork_killall (void)
329 /* Walk list and kill every pid. No need to treat the
330 current inferior_ptid as special (we do not return a
331 status for it) -- however any process may be a child
332 or a parent, so may get a SIGCHLD from a previously
333 killed child. Wait them all out. */
334 struct fork_info
*fp
;
338 for (fp
= fork_list
; fp
; fp
= fp
->next
)
340 pid
= PIDGET (fp
->ptid
);
342 ptrace (PT_KILL
, pid
, 0, 0);
343 ret
= waitpid (pid
, &status
, 0);
344 /* We might get a SIGCHLD instead of an exit status. This is
345 aggravated by the first kill above - a child has just
346 died. MVS comment cut-and-pasted from linux-nat. */
347 } while (ret
== pid
&& WIFSTOPPED (status
));
349 init_fork_list (); /* Clear list, prepare to start fresh. */
352 /* The current inferior_ptid has exited, but there are other viable
353 forks to debug. Delete the exiting one and context-switch to the
357 linux_fork_mourn_inferior (void)
359 /* Wait just one more time to collect the inferior's exit status.
360 Do not check whether this succeeds though, since we may be
361 dealing with a process that we attached to. Such a process will
362 only report its exit status to its original parent. */
365 waitpid (ptid_get_pid (inferior_ptid
), &status
, 0);
367 /* OK, presumably inferior_ptid is the one who has exited.
368 We need to delete that one from the fork_list, and switch
369 to the next available fork. */
370 delete_fork (inferior_ptid
);
372 /* There should still be a fork - if there's only one left,
373 delete_fork won't remove it, because we haven't updated
374 inferior_ptid yet. */
375 gdb_assert (fork_list
);
377 fork_load_infrun_state (fork_list
);
378 printf_filtered (_("[Switching to %s]\n"),
379 target_pid_to_str (inferior_ptid
));
381 /* If there's only one fork, switch back to non-fork mode. */
382 if (fork_list
->next
== NULL
)
383 delete_fork (inferior_ptid
);
386 /* Fork list <-> user interface. */
389 delete_fork_command (char *args
, int from_tty
)
394 error (_("Requires argument (fork/checkpoint id to delete)"));
396 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
397 if (ptid_equal (ptid
, minus_one_ptid
))
398 error (_("No such fork/checkpoint id, %s"), args
);
400 if (ptid_equal (ptid
, inferior_ptid
))
401 error (_("Please switch to another fork/checkpoint before deleting the current one"));
403 if (ptrace (PTRACE_KILL
, PIDGET (ptid
), 0, 0))
404 error (_("Unable to kill pid %s"), target_tid_to_str (ptid
));
407 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
413 detach_fork_command (char *args
, int from_tty
)
418 error (_("Requires argument (fork id to detach)"));
420 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
421 if (ptid_equal (ptid
, minus_one_ptid
))
422 error (_("No such fork id, %s"), args
);
424 if (ptid_equal (ptid
, inferior_ptid
))
425 error (_("Please switch to another fork before detaching the current one"));
427 if (ptrace (PTRACE_DETACH
, PIDGET (ptid
), 0, 0))
428 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
431 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
436 /* Print information about currently known forks. */
439 info_forks_command (char *arg
, int from_tty
)
441 struct frame_info
*cur_frame
;
442 struct symtab_and_line sal
;
443 struct symtab
*cur_symtab
;
444 struct fork_info
*fp
;
448 struct fork_info
*printed
= NULL
;
451 requested
= (int) parse_and_eval_long (arg
);
453 for (fp
= fork_list
; fp
; fp
= fp
->next
)
455 if (requested
> 0 && fp
->num
!= requested
)
459 if (ptid_equal (fp
->ptid
, inferior_ptid
))
461 printf_filtered ("* ");
466 printf_filtered (" ");
469 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
471 printf_filtered (_(" (main process)"));
472 printf_filtered (_(" at "));
473 deprecated_print_address_numeric (pc
, 1, gdb_stdout
);
475 sal
= find_pc_line (pc
, 0);
478 char *tmp
= strrchr (sal
.symtab
->filename
, '/');
481 printf_filtered (_(", file %s"), tmp
+ 1);
483 printf_filtered (_(", file %s"), sal
.symtab
->filename
);
486 printf_filtered (_(", line %d"), sal
.line
);
487 if (!sal
.symtab
&& !sal
.line
)
489 struct minimal_symbol
*msym
;
491 msym
= lookup_minimal_symbol_by_pc (pc
);
493 printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym
));
496 putchar_filtered ('\n');
501 printf_filtered (_("No fork number %d.\n"), requested
);
503 printf_filtered (_("No forks.\n"));
507 /* Save/restore mode variable 'detach_fork':
508 We need to temporarily take over this mode variable, while
509 preserving the user-specified state, and make sure that it
510 gets restored in case of error.
512 The int pointer that we use comes from the caller, so we can
513 be called more than once (even though currently we don't need to). */
516 restore_detach_fork (void *arg
)
518 detach_fork
= *(int *) arg
;
521 static struct cleanup
*
522 save_detach_fork (int *saved_val
)
524 *saved_val
= detach_fork
;
525 return make_cleanup (restore_detach_fork
, (void *) saved_val
);
529 checkpoint_command (char *args
, int from_tty
)
531 struct target_waitstatus last_target_waitstatus
;
532 ptid_t last_target_ptid
;
533 struct value
*fork_fn
= NULL
, *ret
;
534 struct fork_info
*fp
;
536 struct cleanup
*old_chain
;
538 /* Make this temp var static, 'cause it's used in the error context. */
539 static int temp_detach_fork
;
541 /* Make the inferior fork, record its (and gdb's) state. */
543 if (lookup_minimal_symbol ("fork", NULL
, NULL
) != NULL
)
544 fork_fn
= find_function_in_inferior ("fork");
546 if (lookup_minimal_symbol ("_fork", NULL
, NULL
) != NULL
)
547 fork_fn
= find_function_in_inferior ("fork");
549 error (_("checkpoint: can't find fork function in inferior."));
551 ret
= value_from_longest (builtin_type_int
, 0);
552 old_chain
= save_detach_fork (&temp_detach_fork
);
554 ret
= call_function_by_hand (fork_fn
, 0, &ret
);
555 do_cleanups (old_chain
);
556 if (!ret
) /* Probably can't happen. */
557 error (_("checkpoint: call_function_by_hand returned null."));
559 retpid
= value_as_long (ret
);
560 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
565 printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
569 parent_pid
= ptid_get_lwp (last_target_ptid
);
571 parent_pid
= ptid_get_pid (last_target_ptid
);
572 printf_filtered (_(" gdb says parent = %ld.\n"),
577 fp
= find_fork_pid (retpid
);
579 error (_("Failed to find new fork"));
580 fork_save_infrun_state (fp
, 1);
584 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
586 /* Now we attempt to switch processes. */
587 struct fork_info
*oldfp
= find_fork_ptid (inferior_ptid
);
592 error (_("No such fork/process"));
595 oldfp
= add_fork (ptid_get_pid (inferior_ptid
));
597 fork_save_infrun_state (oldfp
, 1);
598 fork_load_infrun_state (newfp
);
600 printf_filtered (_("Switching to %s\n"),
601 target_pid_to_str (inferior_ptid
));
603 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
);
606 /* Switch inferior process (fork) context, by process id. */
608 process_command (char *args
, int from_tty
)
610 struct fork_info
*fp
;
613 error (_("Requires argument (process id to switch to)"));
615 if ((fp
= find_fork_pid (parse_and_eval_long (args
))) == NULL
)
616 error (_("Not found: process id %s"), args
);
618 linux_fork_context (fp
, from_tty
);
621 /* Switch inferior process (fork) context, by fork id. */
623 fork_command (char *args
, int from_tty
)
625 struct fork_info
*fp
;
628 error (_("Requires argument (fork id to switch to)"));
630 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
631 error (_("Not found: fork id %s"), args
);
633 linux_fork_context (fp
, from_tty
);
636 /* Switch inferior process (fork) context, by checkpoint id. */
638 restart_command (char *args
, int from_tty
)
640 struct fork_info
*fp
;
643 error (_("Requires argument (checkpoint id to restart)"));
645 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
646 error (_("Not found: checkpoint id %s"), args
);
648 linux_fork_context (fp
, from_tty
);
652 _initialize_linux_fork (void)
656 /* Set/show detach-on-fork: user-settable mode. */
658 add_setshow_boolean_cmd ("detach-on-fork", class_obscure
, &detach_fork
, _("\
659 Set whether gdb will detach the child of a fork."), _("\
660 Show whether gdb will detach the child of a fork."), _("\
661 Tells gdb whether to detach the child of a fork."),
662 NULL
, NULL
, &setlist
, &showlist
);
664 /* Set/show restart-auto-finish: user-settable count. Causes the
665 first "restart" of a fork to do some number of "finish" commands
666 before returning to user.
668 Useful because otherwise the virgin fork process will be stopped
669 somewhere in the un-interesting fork system call. */
671 /* Checkpoint command: create a fork of the inferior process
672 and set it aside for later debugging. */
674 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
675 Fork a duplicate process (experimental)."));
677 /* Restart command: restore the context of a specified fork
678 process. May be used for "program forks" as well as for
679 "debugger forks" (checkpoints). */
681 add_com ("restart", class_obscure
, restart_command
, _("\
682 restart <n>: restore program context from a checkpoint.\n\
683 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
685 /* Delete checkpoint command: kill the process and remove it from
688 add_cmd ("checkpoint", class_obscure
, delete_fork_command
, _("\
689 Delete a fork/checkpoint (experimental)."),
692 /* Detach checkpoint command: release the process to run independently,
693 and remove it from the fork list. */
695 add_cmd ("checkpoint", class_obscure
, detach_fork_command
, _("\
696 Detach from a fork/checkpoint (experimental)."),
699 /* Info checkpoints command: list all forks/checkpoints
700 currently under gdb's control. */
702 add_info ("checkpoints", info_forks_command
,
703 _("IDs of currently known forks/checkpoints."));
705 /* Command aliases (let "fork" and "checkpoint" be used
708 add_alias_cmd ("fork", "checkpoint", class_obscure
, 1, &deletelist
);
709 add_alias_cmd ("fork", "checkpoint", class_obscure
, 1, &detachlist
);
710 add_info_alias ("forks", "checkpoints", 0);
712 /* "fork <n>" (by analogy to "thread <n>"). */
713 add_com ("fork", class_obscure
, fork_command
, _("\
714 fork <n>: Switch between forked processes.\n\
715 Argument 'n' is fork ID, as displayed by 'info forks'."));
717 /* "process <proc id>" as opposed to "fork <fork id>". */
718 add_com ("process", class_obscure
, process_command
, _("\
719 process <pid>: Switch between forked processes.\n\
720 Argument 'pid' is process ID, as displayed by 'info forks' or 'shell ps'."));