1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005-2017 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 "linux-fork.h"
29 #include "linux-nat.h"
30 #include "gdbthread.h"
33 #include "nat/gdb_ptrace.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 /* Fork list data structure: */
47 struct fork_info
*next
;
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. */
58 /* Fork list methods: */
63 return (fork_list
!= NULL
);
66 /* Return the last fork in the list. */
68 static struct fork_info
*
71 struct fork_info
*last
;
73 if (fork_list
== NULL
)
76 for (last
= fork_list
; last
->next
!= NULL
; last
= last
->next
)
81 /* Add a fork to the internal fork list. */
88 if (fork_list
== NULL
&& pid
!= ptid_get_pid (inferior_ptid
))
90 /* Special case -- if this is the first fork in the list
91 (the list is hitherto empty), and if this new fork is
92 NOT the current inferior_ptid, then add inferior_ptid
93 first, as a special zeroeth fork id. */
94 highest_fork_num
= -1;
95 add_fork (ptid_get_pid (inferior_ptid
)); /* safe recursion */
98 fp
= XCNEW (struct fork_info
);
99 fp
->ptid
= ptid_build (pid
, pid
, 0);
100 fp
->num
= ++highest_fork_num
;
102 if (fork_list
== NULL
)
106 struct fork_info
*last
= find_last_fork ();
115 free_fork (struct fork_info
*fp
)
117 /* Notes on step-resume breakpoints: since this is a concern for
118 threads, let's convince ourselves that it's not a concern for
119 forks. There are two ways for a fork_info to be created. First,
120 by the checkpoint command, in which case we're at a gdb prompt
121 and there can't be any step-resume breakpoint. Second, by a fork
122 in the user program, in which case we *may* have stepped into the
123 fork call, but regardless of whether we follow the parent or the
124 child, we will return to the same place and the step-resume
125 breakpoint, if any, will take care of itself as usual. And
126 unlike threads, we do not save a private copy of the step-resume
127 breakpoint -- so we're OK. */
132 regcache_xfree (fp
->savedregs
);
140 delete_fork (ptid_t ptid
)
142 struct fork_info
*fp
, *fpprev
;
146 linux_nat_forget_process (ptid_get_pid (ptid
));
148 for (fp
= fork_list
; fp
; fpprev
= fp
, fp
= fp
->next
)
149 if (ptid_equal (fp
->ptid
, ptid
))
156 fpprev
->next
= fp
->next
;
158 fork_list
= fp
->next
;
162 /* Special case: if there is now only one process in the list,
163 and if it is (hopefully!) the current inferior_ptid, then
164 remove it, leaving the list empty -- we're now down to the
165 default case of debugging a single process. */
166 if (fork_list
!= NULL
&& fork_list
->next
== NULL
&&
167 ptid_equal (fork_list
->ptid
, inferior_ptid
))
169 /* Last fork -- delete from list and handle as solo process
170 (should be a safe recursion). */
171 delete_fork (inferior_ptid
);
175 /* Find a fork_info by matching PTID. */
176 static struct fork_info
*
177 find_fork_ptid (ptid_t ptid
)
179 struct fork_info
*fp
;
181 for (fp
= fork_list
; fp
; fp
= fp
->next
)
182 if (ptid_equal (fp
->ptid
, ptid
))
188 /* Find a fork_info by matching ID. */
189 static struct fork_info
*
190 find_fork_id (int num
)
192 struct fork_info
*fp
;
194 for (fp
= fork_list
; fp
; fp
= fp
->next
)
201 /* Find a fork_info by matching pid. */
202 extern struct fork_info
*
203 find_fork_pid (pid_t pid
)
205 struct fork_info
*fp
;
207 for (fp
= fork_list
; fp
; fp
= fp
->next
)
208 if (pid
== ptid_get_pid (fp
->ptid
))
215 fork_id_to_ptid (int num
)
217 struct fork_info
*fork
= find_fork_id (num
);
221 return pid_to_ptid (-1);
225 init_fork_list (void)
227 struct fork_info
*fp
, *fpnext
;
232 for (fp
= fork_list
; fp
; fp
= fpnext
)
241 /* Fork list <-> gdb interface. */
243 /* Utility function for fork_load/fork_save.
244 Calls lseek in the (current) inferior process. */
247 call_lseek (int fd
, off_t offset
, int whence
)
251 snprintf (&exp
[0], sizeof (exp
), "lseek (%d, %ld, %d)",
252 fd
, (long) offset
, whence
);
253 return (off_t
) parse_and_eval_long (&exp
[0]);
256 /* Load infrun state for the fork PTID. */
259 fork_load_infrun_state (struct fork_info
*fp
)
261 extern void nullify_last_target_wait_ptid ();
264 linux_nat_switch_fork (fp
->ptid
);
266 if (fp
->savedregs
&& fp
->clobber_regs
)
267 regcache_cpy (get_current_regcache (), fp
->savedregs
);
269 registers_changed ();
270 reinit_frame_cache ();
272 stop_pc
= regcache_read_pc (get_current_regcache ());
273 nullify_last_target_wait_ptid ();
275 /* Now restore the file positions of open file descriptors. */
278 for (i
= 0; i
<= fp
->maxfd
; i
++)
279 if (fp
->filepos
[i
] != (off_t
) -1)
280 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
281 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
282 this is native-only. If it ever has to be cross, we'll have
287 /* Save infrun state for the fork PTID.
288 Exported for use by linux child_follow_fork. */
291 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
298 regcache_xfree (fp
->savedregs
);
300 fp
->savedregs
= regcache_dup (get_current_regcache ());
301 fp
->clobber_regs
= clobber_regs
;
305 /* Now save the 'state' (file position) of all open file descriptors.
306 Unfortunately fork does not take care of that for us... */
307 snprintf (path
, PATH_MAX
, "/proc/%ld/fd",
308 (long) ptid_get_pid (fp
->ptid
));
309 if ((d
= opendir (path
)) != NULL
)
314 while ((de
= readdir (d
)) != NULL
)
316 /* Count open file descriptors (actually find highest
318 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
322 /* Allocate array of file positions. */
323 fp
->filepos
= XRESIZEVEC (off_t
, fp
->filepos
, fp
->maxfd
+ 1);
325 /* Initialize to -1 (invalid). */
326 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
327 fp
->filepos
[tmp
] = -1;
329 /* Now find actual file positions. */
331 while ((de
= readdir (d
)) != NULL
)
332 if (isdigit (de
->d_name
[0]))
334 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
335 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
342 /* Kill 'em all, let God sort 'em out... */
345 linux_fork_killall (void)
347 /* Walk list and kill every pid. No need to treat the
348 current inferior_ptid as special (we do not return a
349 status for it) -- however any process may be a child
350 or a parent, so may get a SIGCHLD from a previously
351 killed child. Wait them all out. */
352 struct fork_info
*fp
;
356 for (fp
= fork_list
; fp
; fp
= fp
->next
)
358 pid
= ptid_get_pid (fp
->ptid
);
360 /* Use SIGKILL instead of PTRACE_KILL because the former works even
361 if the thread is running, while the later doesn't. */
363 ret
= waitpid (pid
, &status
, 0);
364 /* We might get a SIGCHLD instead of an exit status. This is
365 aggravated by the first kill above - a child has just
366 died. MVS comment cut-and-pasted from linux-nat. */
367 } while (ret
== pid
&& WIFSTOPPED (status
));
369 init_fork_list (); /* Clear list, prepare to start fresh. */
372 /* The current inferior_ptid has exited, but there are other viable
373 forks to debug. Delete the exiting one and context-switch to the
377 linux_fork_mourn_inferior (void)
379 struct fork_info
*last
;
382 /* Wait just one more time to collect the inferior's exit status.
383 Do not check whether this succeeds though, since we may be
384 dealing with a process that we attached to. Such a process will
385 only report its exit status to its original parent. */
386 waitpid (ptid_get_pid (inferior_ptid
), &status
, 0);
388 /* OK, presumably inferior_ptid is the one who has exited.
389 We need to delete that one from the fork_list, and switch
390 to the next available fork. */
391 delete_fork (inferior_ptid
);
393 /* There should still be a fork - if there's only one left,
394 delete_fork won't remove it, because we haven't updated
395 inferior_ptid yet. */
396 gdb_assert (fork_list
);
398 last
= find_last_fork ();
399 fork_load_infrun_state (last
);
400 printf_filtered (_("[Switching to %s]\n"),
401 target_pid_to_str (inferior_ptid
));
403 /* If there's only one fork, switch back to non-fork mode. */
404 if (fork_list
->next
== NULL
)
405 delete_fork (inferior_ptid
);
408 /* The current inferior_ptid is being detached, but there are other
409 viable forks to debug. Detach and delete it and context-switch to
410 the first available. */
413 linux_fork_detach (const char *args
, int from_tty
)
415 /* OK, inferior_ptid is the one we are detaching from. We need to
416 delete it from the fork_list, and switch to the next available
419 if (ptrace (PTRACE_DETACH
, ptid_get_pid (inferior_ptid
), 0, 0))
420 error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid
));
422 delete_fork (inferior_ptid
);
424 /* There should still be a fork - if there's only one left,
425 delete_fork won't remove it, because we haven't updated
426 inferior_ptid yet. */
427 gdb_assert (fork_list
);
429 fork_load_infrun_state (fork_list
);
432 printf_filtered (_("[Switching to %s]\n"),
433 target_pid_to_str (inferior_ptid
));
435 /* If there's only one fork, switch back to non-fork mode. */
436 if (fork_list
->next
== NULL
)
437 delete_fork (inferior_ptid
);
441 inferior_call_waitpid_cleanup (void *fp
)
443 struct fork_info
*oldfp
= (struct fork_info
*) fp
;
447 /* Switch back to inferior_ptid. */
448 remove_breakpoints ();
449 fork_load_infrun_state (oldfp
);
450 insert_breakpoints ();
455 inferior_call_waitpid (ptid_t pptid
, int pid
)
457 struct objfile
*waitpid_objf
;
458 struct value
*waitpid_fn
= NULL
;
459 struct value
*argv
[4], *retv
;
460 struct gdbarch
*gdbarch
= get_current_arch ();
461 struct fork_info
*oldfp
= NULL
, *newfp
= NULL
;
462 struct cleanup
*old_cleanup
;
465 if (!ptid_equal (pptid
, inferior_ptid
))
467 /* Switch to pptid. */
468 oldfp
= find_fork_ptid (inferior_ptid
);
469 gdb_assert (oldfp
!= NULL
);
470 newfp
= find_fork_ptid (pptid
);
471 gdb_assert (newfp
!= NULL
);
472 fork_save_infrun_state (oldfp
, 1);
473 remove_breakpoints ();
474 fork_load_infrun_state (newfp
);
475 insert_breakpoints ();
478 old_cleanup
= make_cleanup (inferior_call_waitpid_cleanup
, oldfp
);
480 /* Get the waitpid_fn. */
481 if (lookup_minimal_symbol ("waitpid", NULL
, NULL
).minsym
!= NULL
)
482 waitpid_fn
= find_function_in_inferior ("waitpid", &waitpid_objf
);
484 && lookup_minimal_symbol ("_waitpid", NULL
, NULL
).minsym
!= NULL
)
485 waitpid_fn
= find_function_in_inferior ("_waitpid", &waitpid_objf
);
490 argv
[0] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, pid
);
491 argv
[1] = value_from_pointer (builtin_type (gdbarch
)->builtin_data_ptr
, 0);
492 argv
[2] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
495 retv
= call_function_by_hand (waitpid_fn
, 3, argv
);
496 if (value_as_long (retv
) < 0)
502 do_cleanups (old_cleanup
);
506 /* Fork list <-> user interface. */
509 delete_checkpoint_command (char *args
, int from_tty
)
512 struct fork_info
*fi
;
515 error (_("Requires argument (checkpoint id to delete)"));
517 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
518 if (ptid_equal (ptid
, minus_one_ptid
))
519 error (_("No such checkpoint id, %s"), args
);
521 if (ptid_equal (ptid
, inferior_ptid
))
523 Please switch to another checkpoint before deleting the current one"));
525 if (ptrace (PTRACE_KILL
, ptid_get_pid (ptid
), 0, 0))
526 error (_("Unable to kill pid %s"), target_pid_to_str (ptid
));
528 fi
= find_fork_ptid (ptid
);
530 pptid
= fi
->parent_ptid
;
533 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
537 /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
538 list, waitpid the ptid.
539 If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
541 if ((!find_thread_ptid (pptid
) && find_fork_ptid (pptid
))
542 || (find_thread_ptid (pptid
) && is_stopped (pptid
)))
544 if (inferior_call_waitpid (pptid
, ptid_get_pid (ptid
)))
545 warning (_("Unable to wait pid %s"), target_pid_to_str (ptid
));
550 detach_checkpoint_command (char *args
, int from_tty
)
555 error (_("Requires argument (checkpoint id to detach)"));
557 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
558 if (ptid_equal (ptid
, minus_one_ptid
))
559 error (_("No such checkpoint id, %s"), args
);
561 if (ptid_equal (ptid
, inferior_ptid
))
563 Please switch to another checkpoint before detaching the current one"));
565 if (ptrace (PTRACE_DETACH
, ptid_get_pid (ptid
), 0, 0))
566 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
569 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
574 /* Print information about currently known checkpoints. */
577 info_checkpoints_command (char *arg
, int from_tty
)
579 struct gdbarch
*gdbarch
= get_current_arch ();
580 struct symtab_and_line sal
;
581 struct fork_info
*fp
;
584 struct fork_info
*printed
= NULL
;
587 requested
= (int) parse_and_eval_long (arg
);
589 for (fp
= fork_list
; fp
; fp
= fp
->next
)
591 if (requested
> 0 && fp
->num
!= requested
)
595 if (ptid_equal (fp
->ptid
, inferior_ptid
))
597 printf_filtered ("* ");
598 pc
= regcache_read_pc (get_current_regcache ());
602 printf_filtered (" ");
603 pc
= regcache_read_pc (fp
->savedregs
);
605 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
607 printf_filtered (_(" (main process)"));
608 printf_filtered (_(" at "));
609 fputs_filtered (paddress (gdbarch
, pc
), gdb_stdout
);
611 sal
= find_pc_line (pc
, 0);
613 printf_filtered (_(", file %s"),
614 symtab_to_filename_for_display (sal
.symtab
));
616 printf_filtered (_(", line %d"), sal
.line
);
617 if (!sal
.symtab
&& !sal
.line
)
619 struct bound_minimal_symbol msym
;
621 msym
= lookup_minimal_symbol_by_pc (pc
);
623 printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym
.minsym
));
626 putchar_filtered ('\n');
631 printf_filtered (_("No checkpoint number %d.\n"), requested
);
633 printf_filtered (_("No checkpoints.\n"));
637 /* The PID of the process we're checkpointing. */
638 static int checkpointing_pid
= 0;
641 linux_fork_checkpointing_p (int pid
)
643 return (checkpointing_pid
== pid
);
646 /* Callback for iterate over threads. Used to check whether
647 the current inferior is multi-threaded. Returns true as soon
648 as it sees the second thread of the current inferior. */
651 inf_has_multiple_thread_cb (struct thread_info
*tp
, void *data
)
653 int *count_p
= (int *) data
;
655 if (current_inferior ()->pid
== ptid_get_pid (tp
->ptid
))
658 /* Stop the iteration if multiple threads have been detected. */
662 /* Return true if the current inferior is multi-threaded. */
665 inf_has_multiple_threads (void)
669 iterate_over_threads (inf_has_multiple_thread_cb
, &count
);
674 checkpoint_command (char *args
, int from_tty
)
676 struct objfile
*fork_objf
;
677 struct gdbarch
*gdbarch
;
678 struct target_waitstatus last_target_waitstatus
;
679 ptid_t last_target_ptid
;
680 struct value
*fork_fn
= NULL
, *ret
;
681 struct fork_info
*fp
;
684 if (!target_has_execution
)
685 error (_("The program is not being run."));
687 /* Ensure that the inferior is not multithreaded. */
688 update_thread_list ();
689 if (inf_has_multiple_threads ())
690 error (_("checkpoint: can't checkpoint multiple threads."));
692 /* Make the inferior fork, record its (and gdb's) state. */
694 if (lookup_minimal_symbol ("fork", NULL
, NULL
).minsym
!= NULL
)
695 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
697 if (lookup_minimal_symbol ("_fork", NULL
, NULL
).minsym
!= NULL
)
698 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
700 error (_("checkpoint: can't find fork function in inferior."));
702 gdbarch
= get_objfile_arch (fork_objf
);
703 ret
= value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
705 /* Tell linux-nat.c that we're checkpointing this inferior. */
707 scoped_restore save_pid
708 = make_scoped_restore (&checkpointing_pid
, ptid_get_pid (inferior_ptid
));
710 ret
= call_function_by_hand (fork_fn
, 0, &ret
);
713 if (!ret
) /* Probably can't happen. */
714 error (_("checkpoint: call_function_by_hand returned null."));
716 retpid
= value_as_long (ret
);
717 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
719 fp
= find_fork_pid (retpid
);
725 printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
726 fp
!= NULL
? fp
->num
: -1, (long) retpid
);
729 parent_pid
= ptid_get_lwp (last_target_ptid
);
731 parent_pid
= ptid_get_pid (last_target_ptid
);
732 printf_filtered (_(" gdb says parent = %ld.\n"),
738 error (_("Failed to find new fork"));
739 fork_save_infrun_state (fp
, 1);
740 fp
->parent_ptid
= last_target_ptid
;
744 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
746 /* Now we attempt to switch processes. */
747 struct fork_info
*oldfp
;
749 gdb_assert (newfp
!= NULL
);
751 oldfp
= find_fork_ptid (inferior_ptid
);
752 gdb_assert (oldfp
!= NULL
);
754 fork_save_infrun_state (oldfp
, 1);
755 remove_breakpoints ();
756 fork_load_infrun_state (newfp
);
757 insert_breakpoints ();
759 printf_filtered (_("Switching to %s\n"),
760 target_pid_to_str (inferior_ptid
));
762 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
, 1);
765 /* Switch inferior process (checkpoint) context, by checkpoint id. */
767 restart_command (char *args
, int from_tty
)
769 struct fork_info
*fp
;
772 error (_("Requires argument (checkpoint id to restart)"));
774 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
775 error (_("Not found: checkpoint id %s"), args
);
777 linux_fork_context (fp
, from_tty
);
781 _initialize_linux_fork (void)
785 /* Checkpoint command: create a fork of the inferior process
786 and set it aside for later debugging. */
788 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
789 Fork a duplicate process (experimental)."));
791 /* Restart command: restore the context of a specified checkpoint
794 add_com ("restart", class_obscure
, restart_command
, _("\
795 restart <n>: restore program context from a checkpoint.\n\
796 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
798 /* Delete checkpoint command: kill the process and remove it from
801 add_cmd ("checkpoint", class_obscure
, delete_checkpoint_command
, _("\
802 Delete a checkpoint (experimental)."),
805 /* Detach checkpoint command: release the process to run independently,
806 and remove it from the fork list. */
808 add_cmd ("checkpoint", class_obscure
, detach_checkpoint_command
, _("\
809 Detach from a checkpoint (experimental)."),
812 /* Info checkpoints command: list all forks/checkpoints
813 currently under gdb's control. */
815 add_info ("checkpoints", info_checkpoints_command
,
816 _("IDs of currently known checkpoints."));