1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005-2018 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 /* Fork list data structure: */
44 struct fork_info
*next
;
47 int num
; /* Convenient handle (GDB fork id). */
48 readonly_detached_regcache
*savedregs
; /* Convenient for info fork, saves
49 having to actually switch contexts. */
51 int clobber_regs
; /* True if we should restore saved regs. */
52 off_t
*filepos
; /* Set of open file descriptors' offsets. */
56 /* Fork list methods: */
61 return (fork_list
!= NULL
);
64 /* Return the last fork in the list. */
66 static struct fork_info
*
69 struct fork_info
*last
;
71 if (fork_list
== NULL
)
74 for (last
= fork_list
; last
->next
!= NULL
; last
= last
->next
)
79 /* Add a fork to the internal fork list. */
86 if (fork_list
== NULL
&& pid
!= ptid_get_pid (inferior_ptid
))
88 /* Special case -- if this is the first fork in the list
89 (the list is hitherto empty), and if this new fork is
90 NOT the current inferior_ptid, then add inferior_ptid
91 first, as a special zeroeth fork id. */
92 highest_fork_num
= -1;
93 add_fork (ptid_get_pid (inferior_ptid
)); /* safe recursion */
96 fp
= XCNEW (struct fork_info
);
97 fp
->ptid
= ptid_build (pid
, pid
, 0);
98 fp
->num
= ++highest_fork_num
;
100 if (fork_list
== NULL
)
104 struct fork_info
*last
= find_last_fork ();
113 free_fork (struct fork_info
*fp
)
115 /* Notes on step-resume breakpoints: since this is a concern for
116 threads, let's convince ourselves that it's not a concern for
117 forks. There are two ways for a fork_info to be created. First,
118 by the checkpoint command, in which case we're at a gdb prompt
119 and there can't be any step-resume breakpoint. Second, by a fork
120 in the user program, in which case we *may* have stepped into the
121 fork call, but regardless of whether we follow the parent or the
122 child, we will return to the same place and the step-resume
123 breakpoint, if any, will take care of itself as usual. And
124 unlike threads, we do not save a private copy of the step-resume
125 breakpoint -- so we're OK. */
130 delete fp
->savedregs
;
138 delete_fork (ptid_t ptid
)
140 struct fork_info
*fp
, *fpprev
;
144 linux_nat_forget_process (ptid_get_pid (ptid
));
146 for (fp
= fork_list
; fp
; fpprev
= fp
, fp
= fp
->next
)
147 if (ptid_equal (fp
->ptid
, ptid
))
154 fpprev
->next
= fp
->next
;
156 fork_list
= fp
->next
;
160 /* Special case: if there is now only one process in the list,
161 and if it is (hopefully!) the current inferior_ptid, then
162 remove it, leaving the list empty -- we're now down to the
163 default case of debugging a single process. */
164 if (fork_list
!= NULL
&& fork_list
->next
== NULL
&&
165 ptid_equal (fork_list
->ptid
, inferior_ptid
))
167 /* Last fork -- delete from list and handle as solo process
168 (should be a safe recursion). */
169 delete_fork (inferior_ptid
);
173 /* Find a fork_info by matching PTID. */
174 static struct fork_info
*
175 find_fork_ptid (ptid_t ptid
)
177 struct fork_info
*fp
;
179 for (fp
= fork_list
; fp
; fp
= fp
->next
)
180 if (ptid_equal (fp
->ptid
, ptid
))
186 /* Find a fork_info by matching ID. */
187 static struct fork_info
*
188 find_fork_id (int num
)
190 struct fork_info
*fp
;
192 for (fp
= fork_list
; fp
; fp
= fp
->next
)
199 /* Find a fork_info by matching pid. */
200 extern struct fork_info
*
201 find_fork_pid (pid_t pid
)
203 struct fork_info
*fp
;
205 for (fp
= fork_list
; fp
; fp
= fp
->next
)
206 if (pid
== ptid_get_pid (fp
->ptid
))
213 fork_id_to_ptid (int num
)
215 struct fork_info
*fork
= find_fork_id (num
);
219 return pid_to_ptid (-1);
223 init_fork_list (void)
225 struct fork_info
*fp
, *fpnext
;
230 for (fp
= fork_list
; fp
; fp
= fpnext
)
239 /* Fork list <-> gdb interface. */
241 /* Utility function for fork_load/fork_save.
242 Calls lseek in the (current) inferior process. */
245 call_lseek (int fd
, off_t offset
, int whence
)
249 snprintf (&exp
[0], sizeof (exp
), "(long) lseek (%d, %ld, %d)",
250 fd
, (long) offset
, whence
);
251 return (off_t
) parse_and_eval_long (&exp
[0]);
254 /* Load infrun state for the fork PTID. */
257 fork_load_infrun_state (struct fork_info
*fp
)
259 extern void nullify_last_target_wait_ptid ();
262 linux_nat_switch_fork (fp
->ptid
);
264 if (fp
->savedregs
&& fp
->clobber_regs
)
265 get_current_regcache ()->restore (fp
->savedregs
);
267 registers_changed ();
268 reinit_frame_cache ();
270 stop_pc
= regcache_read_pc (get_current_regcache ());
271 nullify_last_target_wait_ptid ();
273 /* Now restore the file positions of open file descriptors. */
276 for (i
= 0; i
<= fp
->maxfd
; i
++)
277 if (fp
->filepos
[i
] != (off_t
) -1)
278 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
279 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
280 this is native-only. If it ever has to be cross, we'll have
285 /* Save infrun state for the fork PTID.
286 Exported for use by linux child_follow_fork. */
289 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
296 delete fp
->savedregs
;
298 fp
->savedregs
= new readonly_detached_regcache (*get_current_regcache ());
299 fp
->pc
= regcache_read_pc (get_current_regcache ());
300 fp
->clobber_regs
= clobber_regs
;
304 /* Now save the 'state' (file position) of all open file descriptors.
305 Unfortunately fork does not take care of that for us... */
306 snprintf (path
, PATH_MAX
, "/proc/%ld/fd",
307 (long) ptid_get_pid (fp
->ptid
));
308 if ((d
= opendir (path
)) != NULL
)
313 while ((de
= readdir (d
)) != NULL
)
315 /* Count open file descriptors (actually find highest
317 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
321 /* Allocate array of file positions. */
322 fp
->filepos
= XRESIZEVEC (off_t
, fp
->filepos
, fp
->maxfd
+ 1);
324 /* Initialize to -1 (invalid). */
325 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
326 fp
->filepos
[tmp
] = -1;
328 /* Now find actual file positions. */
330 while ((de
= readdir (d
)) != NULL
)
331 if (isdigit (de
->d_name
[0]))
333 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
334 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
341 /* Kill 'em all, let God sort 'em out... */
344 linux_fork_killall (void)
346 /* Walk list and kill every pid. No need to treat the
347 current inferior_ptid as special (we do not return a
348 status for it) -- however any process may be a child
349 or a parent, so may get a SIGCHLD from a previously
350 killed child. Wait them all out. */
351 struct fork_info
*fp
;
355 for (fp
= fork_list
; fp
; fp
= fp
->next
)
357 pid
= ptid_get_pid (fp
->ptid
);
359 /* Use SIGKILL instead of PTRACE_KILL because the former works even
360 if the thread is running, while the later doesn't. */
362 ret
= waitpid (pid
, &status
, 0);
363 /* We might get a SIGCHLD instead of an exit status. This is
364 aggravated by the first kill above - a child has just
365 died. MVS comment cut-and-pasted from linux-nat. */
366 } while (ret
== pid
&& WIFSTOPPED (status
));
368 init_fork_list (); /* Clear list, prepare to start fresh. */
371 /* The current inferior_ptid has exited, but there are other viable
372 forks to debug. Delete the exiting one and context-switch to the
376 linux_fork_mourn_inferior (void)
378 struct fork_info
*last
;
381 /* Wait just one more time to collect the inferior's exit status.
382 Do not check whether this succeeds though, since we may be
383 dealing with a process that we attached to. Such a process will
384 only report its exit status to its original parent. */
385 waitpid (ptid_get_pid (inferior_ptid
), &status
, 0);
387 /* OK, presumably inferior_ptid is the one who has exited.
388 We need to delete that one from the fork_list, and switch
389 to the next available fork. */
390 delete_fork (inferior_ptid
);
392 /* There should still be a fork - if there's only one left,
393 delete_fork won't remove it, because we haven't updated
394 inferior_ptid yet. */
395 gdb_assert (fork_list
);
397 last
= find_last_fork ();
398 fork_load_infrun_state (last
);
399 printf_filtered (_("[Switching to %s]\n"),
400 target_pid_to_str (inferior_ptid
));
402 /* If there's only one fork, switch back to non-fork mode. */
403 if (fork_list
->next
== NULL
)
404 delete_fork (inferior_ptid
);
407 /* The current inferior_ptid is being detached, but there are other
408 viable forks to debug. Detach and delete it and context-switch to
409 the first available. */
412 linux_fork_detach (int from_tty
)
414 /* OK, inferior_ptid is the one we are detaching from. We need to
415 delete it from the fork_list, and switch to the next available
418 if (ptrace (PTRACE_DETACH
, ptid_get_pid (inferior_ptid
), 0, 0))
419 error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid
));
421 delete_fork (inferior_ptid
);
423 /* There should still be a fork - if there's only one left,
424 delete_fork won't remove it, because we haven't updated
425 inferior_ptid yet. */
426 gdb_assert (fork_list
);
428 fork_load_infrun_state (fork_list
);
431 printf_filtered (_("[Switching to %s]\n"),
432 target_pid_to_str (inferior_ptid
));
434 /* If there's only one fork, switch back to non-fork mode. */
435 if (fork_list
->next
== NULL
)
436 delete_fork (inferior_ptid
);
440 inferior_call_waitpid_cleanup (void *fp
)
442 struct fork_info
*oldfp
= (struct fork_info
*) fp
;
446 /* Switch back to inferior_ptid. */
447 remove_breakpoints ();
448 fork_load_infrun_state (oldfp
);
449 insert_breakpoints ();
454 inferior_call_waitpid (ptid_t pptid
, int pid
)
456 struct objfile
*waitpid_objf
;
457 struct value
*waitpid_fn
= NULL
;
458 struct value
*argv
[4], *retv
;
459 struct gdbarch
*gdbarch
= get_current_arch ();
460 struct fork_info
*oldfp
= NULL
, *newfp
= NULL
;
461 struct cleanup
*old_cleanup
;
464 if (!ptid_equal (pptid
, inferior_ptid
))
466 /* Switch to pptid. */
467 oldfp
= find_fork_ptid (inferior_ptid
);
468 gdb_assert (oldfp
!= NULL
);
469 newfp
= find_fork_ptid (pptid
);
470 gdb_assert (newfp
!= NULL
);
471 fork_save_infrun_state (oldfp
, 1);
472 remove_breakpoints ();
473 fork_load_infrun_state (newfp
);
474 insert_breakpoints ();
477 old_cleanup
= make_cleanup (inferior_call_waitpid_cleanup
, oldfp
);
479 /* Get the waitpid_fn. */
480 if (lookup_minimal_symbol ("waitpid", NULL
, NULL
).minsym
!= NULL
)
481 waitpid_fn
= find_function_in_inferior ("waitpid", &waitpid_objf
);
483 && lookup_minimal_symbol ("_waitpid", NULL
, NULL
).minsym
!= NULL
)
484 waitpid_fn
= find_function_in_inferior ("_waitpid", &waitpid_objf
);
489 argv
[0] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, pid
);
490 argv
[1] = value_from_pointer (builtin_type (gdbarch
)->builtin_data_ptr
, 0);
491 argv
[2] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
494 retv
= call_function_by_hand (waitpid_fn
, NULL
, 3, argv
);
495 if (value_as_long (retv
) < 0)
501 do_cleanups (old_cleanup
);
505 /* Fork list <-> user interface. */
508 delete_checkpoint_command (const char *args
, int from_tty
)
511 struct fork_info
*fi
;
514 error (_("Requires argument (checkpoint id to delete)"));
516 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
517 if (ptid_equal (ptid
, minus_one_ptid
))
518 error (_("No such checkpoint id, %s"), args
);
520 if (ptid_equal (ptid
, inferior_ptid
))
522 Please switch to another checkpoint before deleting the current one"));
524 if (ptrace (PTRACE_KILL
, ptid_get_pid (ptid
), 0, 0))
525 error (_("Unable to kill pid %s"), target_pid_to_str (ptid
));
527 fi
= find_fork_ptid (ptid
);
529 pptid
= fi
->parent_ptid
;
532 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
536 /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
537 list, waitpid the ptid.
538 If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
540 if ((!find_thread_ptid (pptid
) && find_fork_ptid (pptid
))
541 || (find_thread_ptid (pptid
) && is_stopped (pptid
)))
543 if (inferior_call_waitpid (pptid
, ptid_get_pid (ptid
)))
544 warning (_("Unable to wait pid %s"), target_pid_to_str (ptid
));
549 detach_checkpoint_command (const char *args
, int from_tty
)
554 error (_("Requires argument (checkpoint id to detach)"));
556 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
557 if (ptid_equal (ptid
, minus_one_ptid
))
558 error (_("No such checkpoint id, %s"), args
);
560 if (ptid_equal (ptid
, inferior_ptid
))
562 Please switch to another checkpoint before detaching the current one"));
564 if (ptrace (PTRACE_DETACH
, ptid_get_pid (ptid
), 0, 0))
565 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
568 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
573 /* Print information about currently known checkpoints. */
576 info_checkpoints_command (const char *arg
, int from_tty
)
578 struct gdbarch
*gdbarch
= get_current_arch ();
579 struct symtab_and_line sal
;
580 struct fork_info
*fp
;
583 struct fork_info
*printed
= NULL
;
586 requested
= (int) parse_and_eval_long (arg
);
588 for (fp
= fork_list
; fp
; fp
= fp
->next
)
590 if (requested
> 0 && fp
->num
!= requested
)
594 if (ptid_equal (fp
->ptid
, inferior_ptid
))
595 printf_filtered ("* ");
597 printf_filtered (" ");
600 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
602 printf_filtered (_(" (main process)"));
603 printf_filtered (_(" at "));
604 fputs_filtered (paddress (gdbarch
, pc
), gdb_stdout
);
606 sal
= find_pc_line (pc
, 0);
608 printf_filtered (_(", file %s"),
609 symtab_to_filename_for_display (sal
.symtab
));
611 printf_filtered (_(", line %d"), sal
.line
);
612 if (!sal
.symtab
&& !sal
.line
)
614 struct bound_minimal_symbol msym
;
616 msym
= lookup_minimal_symbol_by_pc (pc
);
618 printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym
.minsym
));
621 putchar_filtered ('\n');
626 printf_filtered (_("No checkpoint number %d.\n"), requested
);
628 printf_filtered (_("No checkpoints.\n"));
632 /* The PID of the process we're checkpointing. */
633 static int checkpointing_pid
= 0;
636 linux_fork_checkpointing_p (int pid
)
638 return (checkpointing_pid
== pid
);
641 /* Callback for iterate over threads. Used to check whether
642 the current inferior is multi-threaded. Returns true as soon
643 as it sees the second thread of the current inferior. */
646 inf_has_multiple_thread_cb (struct thread_info
*tp
, void *data
)
648 int *count_p
= (int *) data
;
650 if (current_inferior ()->pid
== ptid_get_pid (tp
->ptid
))
653 /* Stop the iteration if multiple threads have been detected. */
657 /* Return true if the current inferior is multi-threaded. */
660 inf_has_multiple_threads (void)
664 iterate_over_threads (inf_has_multiple_thread_cb
, &count
);
669 checkpoint_command (const char *args
, int from_tty
)
671 struct objfile
*fork_objf
;
672 struct gdbarch
*gdbarch
;
673 struct target_waitstatus last_target_waitstatus
;
674 ptid_t last_target_ptid
;
675 struct value
*fork_fn
= NULL
, *ret
;
676 struct fork_info
*fp
;
679 if (!target_has_execution
)
680 error (_("The program is not being run."));
682 /* Ensure that the inferior is not multithreaded. */
683 update_thread_list ();
684 if (inf_has_multiple_threads ())
685 error (_("checkpoint: can't checkpoint multiple threads."));
687 /* Make the inferior fork, record its (and gdb's) state. */
689 if (lookup_minimal_symbol ("fork", NULL
, NULL
).minsym
!= NULL
)
690 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
692 if (lookup_minimal_symbol ("_fork", NULL
, NULL
).minsym
!= NULL
)
693 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
695 error (_("checkpoint: can't find fork function in inferior."));
697 gdbarch
= get_objfile_arch (fork_objf
);
698 ret
= value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
700 /* Tell linux-nat.c that we're checkpointing this inferior. */
702 scoped_restore save_pid
703 = make_scoped_restore (&checkpointing_pid
, ptid_get_pid (inferior_ptid
));
705 ret
= call_function_by_hand (fork_fn
, NULL
, 0, &ret
);
708 if (!ret
) /* Probably can't happen. */
709 error (_("checkpoint: call_function_by_hand returned null."));
711 retpid
= value_as_long (ret
);
712 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
714 fp
= find_fork_pid (retpid
);
720 printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
721 fp
!= NULL
? fp
->num
: -1, (long) retpid
);
724 parent_pid
= ptid_get_lwp (last_target_ptid
);
726 parent_pid
= ptid_get_pid (last_target_ptid
);
727 printf_filtered (_(" gdb says parent = %ld.\n"),
733 error (_("Failed to find new fork"));
734 fork_save_infrun_state (fp
, 1);
735 fp
->parent_ptid
= last_target_ptid
;
739 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
741 /* Now we attempt to switch processes. */
742 struct fork_info
*oldfp
;
744 gdb_assert (newfp
!= NULL
);
746 oldfp
= find_fork_ptid (inferior_ptid
);
747 gdb_assert (oldfp
!= NULL
);
749 fork_save_infrun_state (oldfp
, 1);
750 remove_breakpoints ();
751 fork_load_infrun_state (newfp
);
752 insert_breakpoints ();
754 printf_filtered (_("Switching to %s\n"),
755 target_pid_to_str (inferior_ptid
));
757 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
, 1);
760 /* Switch inferior process (checkpoint) context, by checkpoint id. */
762 restart_command (const char *args
, int from_tty
)
764 struct fork_info
*fp
;
767 error (_("Requires argument (checkpoint id to restart)"));
769 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
770 error (_("Not found: checkpoint id %s"), args
);
772 linux_fork_context (fp
, from_tty
);
776 _initialize_linux_fork (void)
780 /* Checkpoint command: create a fork of the inferior process
781 and set it aside for later debugging. */
783 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
784 Fork a duplicate process (experimental)."));
786 /* Restart command: restore the context of a specified checkpoint
789 add_com ("restart", class_obscure
, restart_command
, _("\
790 restart <n>: restore program context from a checkpoint.\n\
791 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
793 /* Delete checkpoint command: kill the process and remove it from
796 add_cmd ("checkpoint", class_obscure
, delete_checkpoint_command
, _("\
797 Delete a checkpoint (experimental)."),
800 /* Detach checkpoint command: release the process to run independently,
801 and remove it from the fork list. */
803 add_cmd ("checkpoint", class_obscure
, detach_checkpoint_command
, _("\
804 Detach from a checkpoint (experimental)."),
807 /* Info checkpoints command: list all forks/checkpoints
808 currently under gdb's control. */
810 add_info ("checkpoints", info_checkpoints_command
,
811 _("IDs of currently known checkpoints."));