1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005-2019 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"
34 #include "common/gdb_wait.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
!= inferior_ptid
.pid ())
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 (inferior_ptid
.pid ()); /* safe recursion */
96 fp
= XCNEW (struct fork_info
);
97 fp
->ptid
= ptid_t (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_target
->low_forget_process (ptid
.pid ());
146 for (fp
= fork_list
; fp
; fpprev
= fp
, fp
= fp
->next
)
147 if (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 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 (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
== fp
->ptid
.pid ())
213 fork_id_to_ptid (int num
)
215 struct fork_info
*fork
= find_fork_id (num
);
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 inferior_thread ()->suspend
.stop_pc
271 = regcache_read_pc (get_current_regcache ());
272 nullify_last_target_wait_ptid ();
274 /* Now restore the file positions of open file descriptors. */
277 for (i
= 0; i
<= fp
->maxfd
; i
++)
278 if (fp
->filepos
[i
] != (off_t
) -1)
279 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
280 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
281 this is native-only. If it ever has to be cross, we'll have
286 /* Save infrun state for the fork PTID.
287 Exported for use by linux child_follow_fork. */
290 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
297 delete fp
->savedregs
;
299 fp
->savedregs
= new readonly_detached_regcache (*get_current_regcache ());
300 fp
->pc
= regcache_read_pc (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) fp
->ptid
.pid ());
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
= fp
->ptid
.pid ();
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 (inferior_ptid
.pid (), &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 (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
, inferior_ptid
.pid (), 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
);
440 /* Temporarily switch to the infrun state stored on the fork_info
441 identified by a given ptid_t. When this object goes out of scope,
442 restore the currently selected infrun state. */
444 class scoped_switch_fork_info
447 /* Switch to the infrun state held on the fork_info identified by
448 PPTID. If PPTID is the current inferior then no switch is done. */
449 explicit scoped_switch_fork_info (ptid_t pptid
)
452 if (pptid
!= inferior_ptid
)
454 struct fork_info
*newfp
= nullptr;
456 /* Switch to pptid. */
457 m_oldfp
= find_fork_ptid (inferior_ptid
);
458 gdb_assert (m_oldfp
!= nullptr);
459 newfp
= find_fork_ptid (pptid
);
460 gdb_assert (newfp
!= nullptr);
461 fork_save_infrun_state (m_oldfp
, 1);
462 remove_breakpoints ();
463 fork_load_infrun_state (newfp
);
464 insert_breakpoints ();
468 /* Restore the previously selected infrun state. If the constructor
469 didn't need to switch states, then nothing is done here either. */
470 ~scoped_switch_fork_info ()
472 if (m_oldfp
!= nullptr)
474 /* Switch back to inferior_ptid. */
477 remove_breakpoints ();
478 fork_load_infrun_state (m_oldfp
);
479 insert_breakpoints ();
481 CATCH (ex
, RETURN_MASK_ALL
)
483 warning (_("Couldn't restore checkpoint state in %s: %s"),
484 target_pid_to_str (m_oldfp
->ptid
), ex
.message
);
490 DISABLE_COPY_AND_ASSIGN (scoped_switch_fork_info
);
493 /* The fork_info for the previously selected infrun state, or nullptr if
494 we were already in the desired state, and nothing needs to be
496 struct fork_info
*m_oldfp
;
500 inferior_call_waitpid (ptid_t pptid
, int pid
)
502 struct objfile
*waitpid_objf
;
503 struct value
*waitpid_fn
= NULL
;
506 scoped_switch_fork_info
switch_fork_info (pptid
);
508 /* Get the waitpid_fn. */
509 if (lookup_minimal_symbol ("waitpid", NULL
, NULL
).minsym
!= NULL
)
510 waitpid_fn
= find_function_in_inferior ("waitpid", &waitpid_objf
);
512 && lookup_minimal_symbol ("_waitpid", NULL
, NULL
).minsym
!= NULL
)
513 waitpid_fn
= find_function_in_inferior ("_waitpid", &waitpid_objf
);
514 if (waitpid_fn
!= nullptr)
516 struct gdbarch
*gdbarch
= get_current_arch ();
517 struct value
*argv
[3], *retv
;
520 argv
[0] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, pid
);
521 argv
[1] = value_from_pointer (builtin_type (gdbarch
)->builtin_data_ptr
, 0);
522 argv
[2] = value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
524 retv
= call_function_by_hand (waitpid_fn
, NULL
, argv
);
526 if (value_as_long (retv
) >= 0)
533 /* Fork list <-> user interface. */
536 delete_checkpoint_command (const char *args
, int from_tty
)
539 struct fork_info
*fi
;
542 error (_("Requires argument (checkpoint id to delete)"));
544 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
545 if (ptid
== minus_one_ptid
)
546 error (_("No such checkpoint id, %s"), args
);
548 if (ptid
== inferior_ptid
)
550 Please switch to another checkpoint before deleting the current one"));
552 if (ptrace (PTRACE_KILL
, ptid
.pid (), 0, 0))
553 error (_("Unable to kill pid %s"), target_pid_to_str (ptid
));
555 fi
= find_fork_ptid (ptid
);
557 pptid
= fi
->parent_ptid
;
560 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
564 /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
565 list, waitpid the ptid.
566 If fi->parent_ptid is a part of lwp and it is stopped, waitpid the
568 thread_info
*parent
= find_thread_ptid (pptid
);
569 if ((parent
== NULL
&& find_fork_ptid (pptid
))
570 || (parent
!= NULL
&& parent
->state
== THREAD_STOPPED
))
572 if (inferior_call_waitpid (pptid
, ptid
.pid ()))
573 warning (_("Unable to wait pid %s"), target_pid_to_str (ptid
));
578 detach_checkpoint_command (const char *args
, int from_tty
)
583 error (_("Requires argument (checkpoint id to detach)"));
585 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
586 if (ptid
== minus_one_ptid
)
587 error (_("No such checkpoint id, %s"), args
);
589 if (ptid
== inferior_ptid
)
591 Please switch to another checkpoint before detaching the current one"));
593 if (ptrace (PTRACE_DETACH
, ptid
.pid (), 0, 0))
594 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
597 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
602 /* Print information about currently known checkpoints. */
605 info_checkpoints_command (const char *arg
, int from_tty
)
607 struct gdbarch
*gdbarch
= get_current_arch ();
608 struct symtab_and_line sal
;
609 struct fork_info
*fp
;
612 struct fork_info
*printed
= NULL
;
615 requested
= (int) parse_and_eval_long (arg
);
617 for (fp
= fork_list
; fp
; fp
= fp
->next
)
619 if (requested
> 0 && fp
->num
!= requested
)
623 if (fp
->ptid
== inferior_ptid
)
624 printf_filtered ("* ");
626 printf_filtered (" ");
629 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
631 printf_filtered (_(" (main process)"));
632 printf_filtered (_(" at "));
633 fputs_filtered (paddress (gdbarch
, pc
), gdb_stdout
);
635 sal
= find_pc_line (pc
, 0);
637 printf_filtered (_(", file %s"),
638 symtab_to_filename_for_display (sal
.symtab
));
640 printf_filtered (_(", line %d"), sal
.line
);
641 if (!sal
.symtab
&& !sal
.line
)
643 struct bound_minimal_symbol msym
;
645 msym
= lookup_minimal_symbol_by_pc (pc
);
647 printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym
.minsym
));
650 putchar_filtered ('\n');
655 printf_filtered (_("No checkpoint number %d.\n"), requested
);
657 printf_filtered (_("No checkpoints.\n"));
661 /* The PID of the process we're checkpointing. */
662 static int checkpointing_pid
= 0;
665 linux_fork_checkpointing_p (int pid
)
667 return (checkpointing_pid
== pid
);
670 /* Callback for iterate over threads. Used to check whether
671 the current inferior is multi-threaded. Returns true as soon
672 as it sees the second thread of the current inferior. */
675 inf_has_multiple_thread_cb (struct thread_info
*tp
, void *data
)
677 int *count_p
= (int *) data
;
679 if (current_inferior ()->pid
== tp
->ptid
.pid ())
682 /* Stop the iteration if multiple threads have been detected. */
686 /* Return true if the current inferior is multi-threaded. */
689 inf_has_multiple_threads (void)
693 iterate_over_threads (inf_has_multiple_thread_cb
, &count
);
698 checkpoint_command (const char *args
, int from_tty
)
700 struct objfile
*fork_objf
;
701 struct gdbarch
*gdbarch
;
702 struct target_waitstatus last_target_waitstatus
;
703 ptid_t last_target_ptid
;
704 struct value
*fork_fn
= NULL
, *ret
;
705 struct fork_info
*fp
;
708 if (!target_has_execution
)
709 error (_("The program is not being run."));
711 /* Ensure that the inferior is not multithreaded. */
712 update_thread_list ();
713 if (inf_has_multiple_threads ())
714 error (_("checkpoint: can't checkpoint multiple threads."));
716 /* Make the inferior fork, record its (and gdb's) state. */
718 if (lookup_minimal_symbol ("fork", NULL
, NULL
).minsym
!= NULL
)
719 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
721 if (lookup_minimal_symbol ("_fork", NULL
, NULL
).minsym
!= NULL
)
722 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
724 error (_("checkpoint: can't find fork function in inferior."));
726 gdbarch
= get_objfile_arch (fork_objf
);
727 ret
= value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
729 /* Tell linux-nat.c that we're checkpointing this inferior. */
731 scoped_restore save_pid
732 = make_scoped_restore (&checkpointing_pid
, inferior_ptid
.pid ());
734 ret
= call_function_by_hand (fork_fn
, NULL
, {});
737 if (!ret
) /* Probably can't happen. */
738 error (_("checkpoint: call_function_by_hand returned null."));
740 retpid
= value_as_long (ret
);
741 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
743 fp
= find_fork_pid (retpid
);
749 printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
750 fp
!= NULL
? fp
->num
: -1, (long) retpid
);
753 parent_pid
= last_target_ptid
.lwp ();
755 parent_pid
= last_target_ptid
.pid ();
756 printf_filtered (_(" gdb says parent = %ld.\n"),
762 error (_("Failed to find new fork"));
763 fork_save_infrun_state (fp
, 1);
764 fp
->parent_ptid
= last_target_ptid
;
768 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
770 /* Now we attempt to switch processes. */
771 struct fork_info
*oldfp
;
773 gdb_assert (newfp
!= NULL
);
775 oldfp
= find_fork_ptid (inferior_ptid
);
776 gdb_assert (oldfp
!= NULL
);
778 fork_save_infrun_state (oldfp
, 1);
779 remove_breakpoints ();
780 fork_load_infrun_state (newfp
);
781 insert_breakpoints ();
783 printf_filtered (_("Switching to %s\n"),
784 target_pid_to_str (inferior_ptid
));
786 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
, 1);
789 /* Switch inferior process (checkpoint) context, by checkpoint id. */
791 restart_command (const char *args
, int from_tty
)
793 struct fork_info
*fp
;
796 error (_("Requires argument (checkpoint id to restart)"));
798 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
799 error (_("Not found: checkpoint id %s"), args
);
801 linux_fork_context (fp
, from_tty
);
805 _initialize_linux_fork (void)
809 /* Checkpoint command: create a fork of the inferior process
810 and set it aside for later debugging. */
812 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
813 Fork a duplicate process (experimental)."));
815 /* Restart command: restore the context of a specified checkpoint
818 add_com ("restart", class_obscure
, restart_command
, _("\
819 restart N: restore program context from a checkpoint.\n\
820 Argument N is checkpoint ID, as displayed by 'info checkpoints'."));
822 /* Delete checkpoint command: kill the process and remove it from
825 add_cmd ("checkpoint", class_obscure
, delete_checkpoint_command
, _("\
826 Delete a checkpoint (experimental)."),
829 /* Detach checkpoint command: release the process to run independently,
830 and remove it from the fork list. */
832 add_cmd ("checkpoint", class_obscure
, detach_checkpoint_command
, _("\
833 Detach from a checkpoint (experimental)."),
836 /* Info checkpoints command: list all forks/checkpoints
837 currently under gdb's control. */
839 add_info ("checkpoints", info_checkpoints_command
,
840 _("IDs of currently known checkpoints."));