1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005-2014 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"
28 #include "gdb_assert.h"
30 #include "linux-fork.h"
31 #include "linux-nat.h"
32 #include "gdbthread.h"
35 #include <sys/ptrace.h>
40 struct fork_info
*fork_list
;
41 static int highest_fork_num
;
43 /* Prevent warning from -Wmissing-prototypes. */
44 extern void _initialize_linux_fork (void);
46 /* Fork list data structure: */
49 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 off_t
*filepos
; /* Set of open file descriptors' offsets. */
60 /* Fork list methods: */
65 return (fork_list
!= NULL
);
68 /* Add a fork to the internal fork list. */
75 if (fork_list
== NULL
&& pid
!= ptid_get_pid (inferior_ptid
))
77 /* Special case -- if this is the first fork in the list
78 (the list is hitherto empty), and if this new fork is
79 NOT the current inferior_ptid, then add inferior_ptid
80 first, as a special zeroeth fork id. */
81 highest_fork_num
= -1;
82 add_fork (ptid_get_pid (inferior_ptid
)); /* safe recursion */
85 fp
= XCNEW (struct fork_info
);
86 fp
->ptid
= ptid_build (pid
, pid
, 0);
87 fp
->num
= ++highest_fork_num
;
94 free_fork (struct fork_info
*fp
)
96 /* Notes on step-resume breakpoints: since this is a concern for
97 threads, let's convince ourselves that it's not a concern for
98 forks. There are two ways for a fork_info to be created. First,
99 by the checkpoint command, in which case we're at a gdb prompt
100 and there can't be any step-resume breakpoint. Second, by a fork
101 in the user program, in which case we *may* have stepped into the
102 fork call, but regardless of whether we follow the parent or the
103 child, we will return to the same place and the step-resume
104 breakpoint, if any, will take care of itself as usual. And
105 unlike threads, we do not save a private copy of the step-resume
106 breakpoint -- so we're OK. */
111 regcache_xfree (fp
->savedregs
);
119 delete_fork (ptid_t ptid
)
121 struct fork_info
*fp
, *fpprev
;
125 linux_nat_forget_process (ptid_get_pid (ptid
));
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 linux_nat_switch_fork (fp
->ptid
);
245 if (fp
->savedregs
&& fp
->clobber_regs
)
246 regcache_cpy (get_current_regcache (), fp
->savedregs
);
248 registers_changed ();
249 reinit_frame_cache ();
251 stop_pc
= regcache_read_pc (get_current_regcache ());
252 nullify_last_target_wait_ptid ();
254 /* Now restore the file positions of open file descriptors. */
257 for (i
= 0; i
<= fp
->maxfd
; i
++)
258 if (fp
->filepos
[i
] != (off_t
) -1)
259 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
260 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
261 this is native-only. If it ever has to be cross, we'll have
266 /* Save infrun state for the fork PTID.
267 Exported for use by linux child_follow_fork. */
270 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
277 regcache_xfree (fp
->savedregs
);
279 fp
->savedregs
= regcache_dup (get_current_regcache ());
280 fp
->clobber_regs
= clobber_regs
;
284 /* Now save the 'state' (file position) of all open file descriptors.
285 Unfortunately fork does not take care of that for us... */
286 snprintf (path
, PATH_MAX
, "/proc/%ld/fd",
287 (long) ptid_get_pid (fp
->ptid
));
288 if ((d
= opendir (path
)) != NULL
)
293 while ((de
= readdir (d
)) != NULL
)
295 /* Count open file descriptors (actually find highest
297 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
301 /* Allocate array of file positions. */
302 fp
->filepos
= xrealloc (fp
->filepos
,
303 (fp
->maxfd
+ 1) * sizeof (*fp
->filepos
));
305 /* Initialize to -1 (invalid). */
306 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
307 fp
->filepos
[tmp
] = -1;
309 /* Now find actual file positions. */
311 while ((de
= readdir (d
)) != NULL
)
312 if (isdigit (de
->d_name
[0]))
314 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
315 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
322 /* Kill 'em all, let God sort 'em out... */
325 linux_fork_killall (void)
327 /* Walk list and kill every pid. No need to treat the
328 current inferior_ptid as special (we do not return a
329 status for it) -- however any process may be a child
330 or a parent, so may get a SIGCHLD from a previously
331 killed child. Wait them all out. */
332 struct fork_info
*fp
;
336 for (fp
= fork_list
; fp
; fp
= fp
->next
)
338 pid
= ptid_get_pid (fp
->ptid
);
340 /* Use SIGKILL instead of PTRACE_KILL because the former works even
341 if the thread is running, while the later doesn't. */
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 /* The current inferior_ptid is being detached, but there are other
387 viable forks to debug. Detach and delete it and context-switch to
388 the first available. */
391 linux_fork_detach (const char *args
, int from_tty
)
393 /* OK, inferior_ptid is the one we are detaching from. We need to
394 delete it from the fork_list, and switch to the next available
397 if (ptrace (PTRACE_DETACH
, ptid_get_pid (inferior_ptid
), 0, 0))
398 error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid
));
400 delete_fork (inferior_ptid
);
402 /* There should still be a fork - if there's only one left,
403 delete_fork won't remove it, because we haven't updated
404 inferior_ptid yet. */
405 gdb_assert (fork_list
);
407 fork_load_infrun_state (fork_list
);
410 printf_filtered (_("[Switching to %s]\n"),
411 target_pid_to_str (inferior_ptid
));
413 /* If there's only one fork, switch back to non-fork mode. */
414 if (fork_list
->next
== NULL
)
415 delete_fork (inferior_ptid
);
419 inferior_call_waitpid_cleanup (void *fp
)
421 struct fork_info
*oldfp
= fp
;
425 /* Switch back to inferior_ptid. */
426 remove_breakpoints ();
427 fork_load_infrun_state (oldfp
);
428 insert_breakpoints ();
433 inferior_call_waitpid (ptid_t pptid
, int pid
)
435 struct objfile
*waitpid_objf
;
436 struct value
*waitpid_fn
= NULL
;
437 struct value
*argv
[4], *retv
;
438 struct gdbarch
*gdbarch
= get_current_arch ();
439 struct fork_info
*oldfp
= NULL
, *newfp
= NULL
;
440 struct cleanup
*old_cleanup
;
443 if (!ptid_equal (pptid
, inferior_ptid
))
445 /* Switch to pptid. */
446 oldfp
= find_fork_ptid (inferior_ptid
);
447 gdb_assert (oldfp
!= NULL
);
448 newfp
= find_fork_ptid (pptid
);
449 gdb_assert (newfp
!= NULL
);
450 fork_save_infrun_state (oldfp
, 1);
451 remove_breakpoints ();
452 fork_load_infrun_state (newfp
);
453 insert_breakpoints ();
456 old_cleanup
= make_cleanup (inferior_call_waitpid_cleanup
, oldfp
);
458 /* Get the waitpid_fn. */
459 if (lookup_minimal_symbol ("waitpid", NULL
, NULL
).minsym
!= NULL
)
460 waitpid_fn
= find_function_in_inferior ("waitpid", &waitpid_objf
);
462 && lookup_minimal_symbol ("_waitpid", NULL
, NULL
).minsym
!= NULL
)
463 waitpid_fn
= find_function_in_inferior ("_waitpid", &waitpid_objf
);
468 argv
[0] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, pid
);
469 argv
[1] = value_from_pointer (builtin_type (gdbarch
)->builtin_data_ptr
, 0);
470 argv
[2] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
473 retv
= call_function_by_hand (waitpid_fn
, 3, argv
);
474 if (value_as_long (retv
) < 0)
480 do_cleanups (old_cleanup
);
484 /* Fork list <-> user interface. */
487 delete_checkpoint_command (char *args
, int from_tty
)
490 struct fork_info
*fi
;
493 error (_("Requires argument (checkpoint id to delete)"));
495 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
496 if (ptid_equal (ptid
, minus_one_ptid
))
497 error (_("No such checkpoint id, %s"), args
);
499 if (ptid_equal (ptid
, inferior_ptid
))
501 Please switch to another checkpoint before deleting the current one"));
503 if (ptrace (PTRACE_KILL
, ptid_get_pid (ptid
), 0, 0))
504 error (_("Unable to kill pid %s"), target_pid_to_str (ptid
));
506 fi
= find_fork_ptid (ptid
);
508 pptid
= fi
->parent_ptid
;
511 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
515 /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
516 list, waitpid the ptid.
517 If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
519 if ((!find_thread_ptid (pptid
) && find_fork_ptid (pptid
))
520 || (find_thread_ptid (pptid
) && is_stopped (pptid
)))
522 if (inferior_call_waitpid (pptid
, ptid_get_pid (ptid
)))
523 warning (_("Unable to wait pid %s"), target_pid_to_str (ptid
));
528 detach_checkpoint_command (char *args
, int from_tty
)
533 error (_("Requires argument (checkpoint id to detach)"));
535 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
536 if (ptid_equal (ptid
, minus_one_ptid
))
537 error (_("No such checkpoint id, %s"), args
);
539 if (ptid_equal (ptid
, inferior_ptid
))
541 Please switch to another checkpoint before detaching the current one"));
543 if (ptrace (PTRACE_DETACH
, ptid_get_pid (ptid
), 0, 0))
544 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
547 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
552 /* Print information about currently known checkpoints. */
555 info_checkpoints_command (char *arg
, int from_tty
)
557 struct gdbarch
*gdbarch
= get_current_arch ();
558 struct symtab_and_line sal
;
559 struct fork_info
*fp
;
562 struct fork_info
*printed
= NULL
;
565 requested
= (int) parse_and_eval_long (arg
);
567 for (fp
= fork_list
; fp
; fp
= fp
->next
)
569 if (requested
> 0 && fp
->num
!= requested
)
573 if (ptid_equal (fp
->ptid
, inferior_ptid
))
575 printf_filtered ("* ");
576 pc
= regcache_read_pc (get_current_regcache ());
580 printf_filtered (" ");
581 pc
= regcache_read_pc (fp
->savedregs
);
583 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
585 printf_filtered (_(" (main process)"));
586 printf_filtered (_(" at "));
587 fputs_filtered (paddress (gdbarch
, pc
), gdb_stdout
);
589 sal
= find_pc_line (pc
, 0);
591 printf_filtered (_(", file %s"),
592 symtab_to_filename_for_display (sal
.symtab
));
594 printf_filtered (_(", line %d"), sal
.line
);
595 if (!sal
.symtab
&& !sal
.line
)
597 struct bound_minimal_symbol msym
;
599 msym
= lookup_minimal_symbol_by_pc (pc
);
601 printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym
.minsym
));
604 putchar_filtered ('\n');
609 printf_filtered (_("No checkpoint number %d.\n"), requested
);
611 printf_filtered (_("No checkpoints.\n"));
615 /* The PID of the process we're checkpointing. */
616 static int checkpointing_pid
= 0;
619 linux_fork_checkpointing_p (int pid
)
621 return (checkpointing_pid
== pid
);
624 /* Callback for iterate over threads. Used to check whether
625 the current inferior is multi-threaded. Returns true as soon
626 as it sees the second thread of the current inferior. */
629 inf_has_multiple_thread_cb (struct thread_info
*tp
, void *data
)
631 int *count_p
= (int *) data
;
633 if (current_inferior ()->pid
== ptid_get_pid (tp
->ptid
))
636 /* Stop the iteration if multiple threads have been detected. */
640 /* Return true if the current inferior is multi-threaded. */
643 inf_has_multiple_threads (void)
647 iterate_over_threads (inf_has_multiple_thread_cb
, &count
);
652 checkpoint_command (char *args
, int from_tty
)
654 struct objfile
*fork_objf
;
655 struct gdbarch
*gdbarch
;
656 struct target_waitstatus last_target_waitstatus
;
657 ptid_t last_target_ptid
;
658 struct value
*fork_fn
= NULL
, *ret
;
659 struct fork_info
*fp
;
661 struct cleanup
*old_chain
;
663 if (!target_has_execution
)
664 error (_("The program is not being run."));
666 /* Ensure that the inferior is not multithreaded. */
667 update_thread_list ();
668 if (inf_has_multiple_threads ())
669 error (_("checkpoint: can't checkpoint multiple threads."));
671 /* Make the inferior fork, record its (and gdb's) state. */
673 if (lookup_minimal_symbol ("fork", NULL
, NULL
).minsym
!= NULL
)
674 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
676 if (lookup_minimal_symbol ("_fork", NULL
, NULL
).minsym
!= NULL
)
677 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
679 error (_("checkpoint: can't find fork function in inferior."));
681 gdbarch
= get_objfile_arch (fork_objf
);
682 ret
= value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
684 /* Tell linux-nat.c that we're checkpointing this inferior. */
685 old_chain
= make_cleanup_restore_integer (&checkpointing_pid
);
686 checkpointing_pid
= ptid_get_pid (inferior_ptid
);
688 ret
= call_function_by_hand (fork_fn
, 0, &ret
);
689 do_cleanups (old_chain
);
690 if (!ret
) /* Probably can't happen. */
691 error (_("checkpoint: call_function_by_hand returned null."));
693 retpid
= value_as_long (ret
);
694 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
699 printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
703 parent_pid
= ptid_get_lwp (last_target_ptid
);
705 parent_pid
= ptid_get_pid (last_target_ptid
);
706 printf_filtered (_(" gdb says parent = %ld.\n"),
711 fp
= find_fork_pid (retpid
);
713 error (_("Failed to find new fork"));
714 fork_save_infrun_state (fp
, 1);
715 fp
->parent_ptid
= last_target_ptid
;
719 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
721 /* Now we attempt to switch processes. */
722 struct fork_info
*oldfp
;
724 gdb_assert (newfp
!= NULL
);
726 oldfp
= find_fork_ptid (inferior_ptid
);
727 gdb_assert (oldfp
!= NULL
);
729 fork_save_infrun_state (oldfp
, 1);
730 remove_breakpoints ();
731 fork_load_infrun_state (newfp
);
732 insert_breakpoints ();
734 printf_filtered (_("Switching to %s\n"),
735 target_pid_to_str (inferior_ptid
));
737 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
, 1);
740 /* Switch inferior process (checkpoint) context, by checkpoint id. */
742 restart_command (char *args
, int from_tty
)
744 struct fork_info
*fp
;
747 error (_("Requires argument (checkpoint id to restart)"));
749 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
750 error (_("Not found: checkpoint id %s"), args
);
752 linux_fork_context (fp
, from_tty
);
756 _initialize_linux_fork (void)
760 /* Checkpoint command: create a fork of the inferior process
761 and set it aside for later debugging. */
763 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
764 Fork a duplicate process (experimental)."));
766 /* Restart command: restore the context of a specified checkpoint
769 add_com ("restart", class_obscure
, restart_command
, _("\
770 restart <n>: restore program context from a checkpoint.\n\
771 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
773 /* Delete checkpoint command: kill the process and remove it from
776 add_cmd ("checkpoint", class_obscure
, delete_checkpoint_command
, _("\
777 Delete a checkpoint (experimental)."),
780 /* Detach checkpoint command: release the process to run independently,
781 and remove it from the fork list. */
783 add_cmd ("checkpoint", class_obscure
, detach_checkpoint_command
, _("\
784 Detach from a checkpoint (experimental)."),
787 /* Info checkpoints command: list all forks/checkpoints
788 currently under gdb's control. */
790 add_info ("checkpoints", info_checkpoints_command
,
791 _("IDs of currently known checkpoints."));