1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005-2013 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 3 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, see <http://www.gnu.org/licenses/>. */
21 #include "arch-utils.h"
27 #include "gdb_assert.h"
29 #include "linux-fork.h"
30 #include "linux-nat.h"
31 #include "gdbthread.h"
34 #include <sys/ptrace.h>
39 struct fork_info
*fork_list
;
40 static int highest_fork_num
;
42 /* Prevent warning from -Wmissing-prototypes. */
43 extern void _initialize_linux_fork (void);
45 /* Fork list data structure: */
48 struct fork_info
*next
;
51 int num
; /* Convenient handle (GDB fork id). */
52 struct regcache
*savedregs
; /* Convenient for info fork, saves
53 having to actually switch contexts. */
54 int clobber_regs
; /* True if we should restore saved regs. */
55 off_t
*filepos
; /* Set of open file descriptors' offsets. */
59 /* Fork list methods: */
64 return (fork_list
!= NULL
);
67 /* Add a fork to the internal fork list. */
74 if (fork_list
== NULL
&& pid
!= ptid_get_pid (inferior_ptid
))
76 /* Special case -- if this is the first fork in the list
77 (the list is hitherto empty), and if this new fork is
78 NOT the current inferior_ptid, then add inferior_ptid
79 first, as a special zeroeth fork id. */
80 highest_fork_num
= -1;
81 add_fork (ptid_get_pid (inferior_ptid
)); /* safe recursion */
84 fp
= XZALLOC (struct fork_info
);
85 fp
->ptid
= ptid_build (pid
, pid
, 0);
86 fp
->num
= ++highest_fork_num
;
93 free_fork (struct fork_info
*fp
)
95 /* Notes on step-resume breakpoints: since this is a concern for
96 threads, let's convince ourselves that it's not a concern for
97 forks. There are two ways for a fork_info to be created. First,
98 by the checkpoint command, in which case we're at a gdb prompt
99 and there can't be any step-resume breakpoint. Second, by a fork
100 in the user program, in which case we *may* have stepped into the
101 fork call, but regardless of whether we follow the parent or the
102 child, we will return to the same place and the step-resume
103 breakpoint, if any, will take care of itself as usual. And
104 unlike threads, we do not save a private copy of the step-resume
105 breakpoint -- so we're OK. */
110 regcache_xfree (fp
->savedregs
);
118 delete_fork (ptid_t ptid
)
120 struct fork_info
*fp
, *fpprev
;
124 linux_nat_forget_process (ptid_get_pid (ptid
));
126 for (fp
= fork_list
; fp
; fpprev
= fp
, fp
= fp
->next
)
127 if (ptid_equal (fp
->ptid
, ptid
))
134 fpprev
->next
= fp
->next
;
136 fork_list
= fp
->next
;
140 /* Special case: if there is now only one process in the list,
141 and if it is (hopefully!) the current inferior_ptid, then
142 remove it, leaving the list empty -- we're now down to the
143 default case of debugging a single process. */
144 if (fork_list
!= NULL
&& fork_list
->next
== NULL
&&
145 ptid_equal (fork_list
->ptid
, inferior_ptid
))
147 /* Last fork -- delete from list and handle as solo process
148 (should be a safe recursion). */
149 delete_fork (inferior_ptid
);
153 /* Find a fork_info by matching PTID. */
154 static struct fork_info
*
155 find_fork_ptid (ptid_t ptid
)
157 struct fork_info
*fp
;
159 for (fp
= fork_list
; fp
; fp
= fp
->next
)
160 if (ptid_equal (fp
->ptid
, ptid
))
166 /* Find a fork_info by matching ID. */
167 static struct fork_info
*
168 find_fork_id (int num
)
170 struct fork_info
*fp
;
172 for (fp
= fork_list
; fp
; fp
= fp
->next
)
179 /* Find a fork_info by matching pid. */
180 extern struct fork_info
*
181 find_fork_pid (pid_t pid
)
183 struct fork_info
*fp
;
185 for (fp
= fork_list
; fp
; fp
= fp
->next
)
186 if (pid
== ptid_get_pid (fp
->ptid
))
193 fork_id_to_ptid (int num
)
195 struct fork_info
*fork
= find_fork_id (num
);
199 return pid_to_ptid (-1);
203 init_fork_list (void)
205 struct fork_info
*fp
, *fpnext
;
210 for (fp
= fork_list
; fp
; fp
= fpnext
)
219 /* Fork list <-> gdb interface. */
221 /* Utility function for fork_load/fork_save.
222 Calls lseek in the (current) inferior process. */
225 call_lseek (int fd
, off_t offset
, int whence
)
229 snprintf (&exp
[0], sizeof (exp
), "lseek (%d, %ld, %d)",
230 fd
, (long) offset
, whence
);
231 return (off_t
) parse_and_eval_long (&exp
[0]);
234 /* Load infrun state for the fork PTID. */
237 fork_load_infrun_state (struct fork_info
*fp
)
239 extern void nullify_last_target_wait_ptid ();
242 linux_nat_switch_fork (fp
->ptid
);
244 if (fp
->savedregs
&& fp
->clobber_regs
)
245 regcache_cpy (get_current_regcache (), fp
->savedregs
);
247 registers_changed ();
248 reinit_frame_cache ();
250 stop_pc
= regcache_read_pc (get_current_regcache ());
251 nullify_last_target_wait_ptid ();
253 /* Now restore the file positions of open file descriptors. */
256 for (i
= 0; i
<= fp
->maxfd
; i
++)
257 if (fp
->filepos
[i
] != (off_t
) -1)
258 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
259 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
260 this is native-only. If it ever has to be cross, we'll have
265 /* Save infrun state for the fork PTID.
266 Exported for use by linux child_follow_fork. */
269 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
276 regcache_xfree (fp
->savedregs
);
278 fp
->savedregs
= regcache_dup (get_current_regcache ());
279 fp
->clobber_regs
= clobber_regs
;
283 /* Now save the 'state' (file position) of all open file descriptors.
284 Unfortunately fork does not take care of that for us... */
285 snprintf (path
, PATH_MAX
, "/proc/%ld/fd",
286 (long) ptid_get_pid (fp
->ptid
));
287 if ((d
= opendir (path
)) != NULL
)
292 while ((de
= readdir (d
)) != NULL
)
294 /* Count open file descriptors (actually find highest
296 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
300 /* Allocate array of file positions. */
301 fp
->filepos
= xrealloc (fp
->filepos
,
302 (fp
->maxfd
+ 1) * sizeof (*fp
->filepos
));
304 /* Initialize to -1 (invalid). */
305 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
306 fp
->filepos
[tmp
] = -1;
308 /* Now find actual file positions. */
310 while ((de
= readdir (d
)) != NULL
)
311 if (isdigit (de
->d_name
[0]))
313 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
314 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
321 /* Kill 'em all, let God sort 'em out... */
324 linux_fork_killall (void)
326 /* Walk list and kill every pid. No need to treat the
327 current inferior_ptid as special (we do not return a
328 status for it) -- however any process may be a child
329 or a parent, so may get a SIGCHLD from a previously
330 killed child. Wait them all out. */
331 struct fork_info
*fp
;
335 for (fp
= fork_list
; fp
; fp
= fp
->next
)
337 pid
= ptid_get_pid (fp
->ptid
);
339 /* Use SIGKILL instead of PTRACE_KILL because the former works even
340 if the thread is running, while the later doesn't. */
342 ret
= waitpid (pid
, &status
, 0);
343 /* We might get a SIGCHLD instead of an exit status. This is
344 aggravated by the first kill above - a child has just
345 died. MVS comment cut-and-pasted from linux-nat. */
346 } while (ret
== pid
&& WIFSTOPPED (status
));
348 init_fork_list (); /* Clear list, prepare to start fresh. */
351 /* The current inferior_ptid has exited, but there are other viable
352 forks to debug. Delete the exiting one and context-switch to the
356 linux_fork_mourn_inferior (void)
358 /* Wait just one more time to collect the inferior's exit status.
359 Do not check whether this succeeds though, since we may be
360 dealing with a process that we attached to. Such a process will
361 only report its exit status to its original parent. */
364 waitpid (ptid_get_pid (inferior_ptid
), &status
, 0);
366 /* OK, presumably inferior_ptid is the one who has exited.
367 We need to delete that one from the fork_list, and switch
368 to the next available fork. */
369 delete_fork (inferior_ptid
);
371 /* There should still be a fork - if there's only one left,
372 delete_fork won't remove it, because we haven't updated
373 inferior_ptid yet. */
374 gdb_assert (fork_list
);
376 fork_load_infrun_state (fork_list
);
377 printf_filtered (_("[Switching to %s]\n"),
378 target_pid_to_str (inferior_ptid
));
380 /* If there's only one fork, switch back to non-fork mode. */
381 if (fork_list
->next
== NULL
)
382 delete_fork (inferior_ptid
);
385 /* The current inferior_ptid is being detached, but there are other
386 viable forks to debug. Detach and delete it and context-switch to
387 the first available. */
390 linux_fork_detach (const char *args
, int from_tty
)
392 /* OK, inferior_ptid is the one we are detaching from. We need to
393 delete it from the fork_list, and switch to the next available
396 if (ptrace (PTRACE_DETACH
, ptid_get_pid (inferior_ptid
), 0, 0))
397 error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid
));
399 delete_fork (inferior_ptid
);
401 /* There should still be a fork - if there's only one left,
402 delete_fork won't remove it, because we haven't updated
403 inferior_ptid yet. */
404 gdb_assert (fork_list
);
406 fork_load_infrun_state (fork_list
);
409 printf_filtered (_("[Switching to %s]\n"),
410 target_pid_to_str (inferior_ptid
));
412 /* If there's only one fork, switch back to non-fork mode. */
413 if (fork_list
->next
== NULL
)
414 delete_fork (inferior_ptid
);
418 inferior_call_waitpid_cleanup (void *fp
)
420 struct fork_info
*oldfp
= fp
;
424 /* Switch back to inferior_ptid. */
425 remove_breakpoints ();
426 fork_load_infrun_state (oldfp
);
427 insert_breakpoints ();
432 inferior_call_waitpid (ptid_t pptid
, int pid
)
434 struct objfile
*waitpid_objf
;
435 struct value
*waitpid_fn
= NULL
;
436 struct value
*argv
[4], *retv
;
437 struct gdbarch
*gdbarch
= get_current_arch ();
438 struct fork_info
*oldfp
= NULL
, *newfp
= NULL
;
439 struct cleanup
*old_cleanup
;
442 if (!ptid_equal (pptid
, inferior_ptid
))
444 /* Switch to pptid. */
445 oldfp
= find_fork_ptid (inferior_ptid
);
446 gdb_assert (oldfp
!= NULL
);
447 newfp
= find_fork_ptid (pptid
);
448 gdb_assert (newfp
!= NULL
);
449 fork_save_infrun_state (oldfp
, 1);
450 remove_breakpoints ();
451 fork_load_infrun_state (newfp
);
452 insert_breakpoints ();
455 old_cleanup
= make_cleanup (inferior_call_waitpid_cleanup
, oldfp
);
457 /* Get the waitpid_fn. */
458 if (lookup_minimal_symbol ("waitpid", NULL
, NULL
) != NULL
)
459 waitpid_fn
= find_function_in_inferior ("waitpid", &waitpid_objf
);
460 if (!waitpid_fn
&& lookup_minimal_symbol ("_waitpid", NULL
, NULL
) != NULL
)
461 waitpid_fn
= find_function_in_inferior ("_waitpid", &waitpid_objf
);
466 argv
[0] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, pid
);
467 argv
[1] = value_from_pointer (builtin_type (gdbarch
)->builtin_data_ptr
, 0);
468 argv
[2] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
471 retv
= call_function_by_hand (waitpid_fn
, 3, argv
);
472 if (value_as_long (retv
) < 0)
478 do_cleanups (old_cleanup
);
482 /* Fork list <-> user interface. */
485 delete_checkpoint_command (char *args
, int from_tty
)
488 struct fork_info
*fi
;
491 error (_("Requires argument (checkpoint id to delete)"));
493 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
494 if (ptid_equal (ptid
, minus_one_ptid
))
495 error (_("No such checkpoint id, %s"), args
);
497 if (ptid_equal (ptid
, inferior_ptid
))
499 Please switch to another checkpoint before deleting the current one"));
501 if (ptrace (PTRACE_KILL
, ptid_get_pid (ptid
), 0, 0))
502 error (_("Unable to kill pid %s"), target_pid_to_str (ptid
));
504 fi
= find_fork_ptid (ptid
);
506 pptid
= fi
->parent_ptid
;
509 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
513 /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
514 list, waitpid the ptid.
515 If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
517 if ((!find_thread_ptid (pptid
) && find_fork_ptid (pptid
))
518 || (find_thread_ptid (pptid
) && is_stopped (pptid
)))
520 if (inferior_call_waitpid (pptid
, ptid_get_pid (ptid
)))
521 warning (_("Unable to wait pid %s"), target_pid_to_str (ptid
));
526 detach_checkpoint_command (char *args
, int from_tty
)
531 error (_("Requires argument (checkpoint id to detach)"));
533 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
534 if (ptid_equal (ptid
, minus_one_ptid
))
535 error (_("No such checkpoint id, %s"), args
);
537 if (ptid_equal (ptid
, inferior_ptid
))
539 Please switch to another checkpoint before detaching the current one"));
541 if (ptrace (PTRACE_DETACH
, ptid_get_pid (ptid
), 0, 0))
542 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
545 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
550 /* Print information about currently known checkpoints. */
553 info_checkpoints_command (char *arg
, int from_tty
)
555 struct gdbarch
*gdbarch
= get_current_arch ();
556 struct symtab_and_line sal
;
557 struct fork_info
*fp
;
560 struct fork_info
*printed
= NULL
;
563 requested
= (int) parse_and_eval_long (arg
);
565 for (fp
= fork_list
; fp
; fp
= fp
->next
)
567 if (requested
> 0 && fp
->num
!= requested
)
571 if (ptid_equal (fp
->ptid
, inferior_ptid
))
573 printf_filtered ("* ");
574 pc
= regcache_read_pc (get_current_regcache ());
578 printf_filtered (" ");
579 pc
= regcache_read_pc (fp
->savedregs
);
581 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
583 printf_filtered (_(" (main process)"));
584 printf_filtered (_(" at "));
585 fputs_filtered (paddress (gdbarch
, pc
), gdb_stdout
);
587 sal
= find_pc_line (pc
, 0);
589 printf_filtered (_(", file %s"),
590 symtab_to_filename_for_display (sal
.symtab
));
592 printf_filtered (_(", line %d"), sal
.line
);
593 if (!sal
.symtab
&& !sal
.line
)
595 struct bound_minimal_symbol msym
;
597 msym
= lookup_minimal_symbol_by_pc (pc
);
599 printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym
.minsym
));
602 putchar_filtered ('\n');
607 printf_filtered (_("No checkpoint number %d.\n"), requested
);
609 printf_filtered (_("No checkpoints.\n"));
613 /* The PID of the process we're checkpointing. */
614 static int checkpointing_pid
= 0;
617 linux_fork_checkpointing_p (int pid
)
619 return (checkpointing_pid
== pid
);
622 /* Callback for iterate over threads. Used to check whether
623 the current inferior is multi-threaded. Returns true as soon
624 as it sees the second thread of the current inferior. */
627 inf_has_multiple_thread_cb (struct thread_info
*tp
, void *data
)
629 int *count_p
= (int *) data
;
631 if (current_inferior ()->pid
== ptid_get_pid (tp
->ptid
))
634 /* Stop the iteration if multiple threads have been detected. */
638 /* Return true if the current inferior is multi-threaded. */
641 inf_has_multiple_threads (void)
645 iterate_over_threads (inf_has_multiple_thread_cb
, &count
);
650 checkpoint_command (char *args
, int from_tty
)
652 struct objfile
*fork_objf
;
653 struct gdbarch
*gdbarch
;
654 struct target_waitstatus last_target_waitstatus
;
655 ptid_t last_target_ptid
;
656 struct value
*fork_fn
= NULL
, *ret
;
657 struct fork_info
*fp
;
659 struct cleanup
*old_chain
;
661 if (!target_has_execution
)
662 error (_("The program is not being run."));
664 /* Ensure that the inferior is not multithreaded. */
665 update_thread_list ();
666 if (inf_has_multiple_threads ())
667 error (_("checkpoint: can't checkpoint multiple threads."));
669 /* Make the inferior fork, record its (and gdb's) state. */
671 if (lookup_minimal_symbol ("fork", NULL
, NULL
) != NULL
)
672 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
674 if (lookup_minimal_symbol ("_fork", NULL
, NULL
) != NULL
)
675 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
677 error (_("checkpoint: can't find fork function in inferior."));
679 gdbarch
= get_objfile_arch (fork_objf
);
680 ret
= value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
682 /* Tell linux-nat.c that we're checkpointing this inferior. */
683 old_chain
= make_cleanup_restore_integer (&checkpointing_pid
);
684 checkpointing_pid
= ptid_get_pid (inferior_ptid
);
686 ret
= call_function_by_hand (fork_fn
, 0, &ret
);
687 do_cleanups (old_chain
);
688 if (!ret
) /* Probably can't happen. */
689 error (_("checkpoint: call_function_by_hand returned null."));
691 retpid
= value_as_long (ret
);
692 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
697 printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
701 parent_pid
= ptid_get_lwp (last_target_ptid
);
703 parent_pid
= ptid_get_pid (last_target_ptid
);
704 printf_filtered (_(" gdb says parent = %ld.\n"),
709 fp
= find_fork_pid (retpid
);
711 error (_("Failed to find new fork"));
712 fork_save_infrun_state (fp
, 1);
713 fp
->parent_ptid
= last_target_ptid
;
717 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
719 /* Now we attempt to switch processes. */
720 struct fork_info
*oldfp
;
722 gdb_assert (newfp
!= NULL
);
724 oldfp
= find_fork_ptid (inferior_ptid
);
725 gdb_assert (oldfp
!= NULL
);
727 fork_save_infrun_state (oldfp
, 1);
728 remove_breakpoints ();
729 fork_load_infrun_state (newfp
);
730 insert_breakpoints ();
732 printf_filtered (_("Switching to %s\n"),
733 target_pid_to_str (inferior_ptid
));
735 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
, 1);
738 /* Switch inferior process (checkpoint) context, by checkpoint id. */
740 restart_command (char *args
, int from_tty
)
742 struct fork_info
*fp
;
745 error (_("Requires argument (checkpoint id to restart)"));
747 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
748 error (_("Not found: checkpoint id %s"), args
);
750 linux_fork_context (fp
, from_tty
);
754 _initialize_linux_fork (void)
758 /* Checkpoint command: create a fork of the inferior process
759 and set it aside for later debugging. */
761 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
762 Fork a duplicate process (experimental)."));
764 /* Restart command: restore the context of a specified checkpoint
767 add_com ("restart", class_obscure
, restart_command
, _("\
768 restart <n>: restore program context from a checkpoint.\n\
769 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
771 /* Delete checkpoint command: kill the process and remove it from
774 add_cmd ("checkpoint", class_obscure
, delete_checkpoint_command
, _("\
775 Delete a checkpoint (experimental)."),
778 /* Detach checkpoint command: release the process to run independently,
779 and remove it from the fork list. */
781 add_cmd ("checkpoint", class_obscure
, detach_checkpoint_command
, _("\
782 Detach from a checkpoint (experimental)."),
785 /* Info checkpoints command: list all forks/checkpoints
786 currently under gdb's control. */
788 add_info ("checkpoints", info_checkpoints_command
,
789 _("IDs of currently known checkpoints."));