1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005, 2006, 2007, 2008, 2009 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"
28 #include "gdb_string.h"
29 #include "linux-fork.h"
30 #include "linux-nat.h"
32 #include <sys/ptrace.h>
34 #include <sys/param.h>
35 #include "gdb_dirent.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 int detach_fork
= 1; /* Default behavior is to detach
45 newly forked processes (legacy). */
47 /* Fork list data structure: */
50 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 internal fork list.
69 Called from linux child_follow_fork. */
71 extern struct fork_info
*
76 if (fork_list
== NULL
&& pid
!= PIDGET (inferior_ptid
))
78 /* Special case -- if this is the first fork in the list
79 (the list is hitherto empty), and if this new fork is
80 NOT the current inferior_ptid, then add inferior_ptid
81 first, as a special zeroeth fork id. */
82 highest_fork_num
= -1;
83 add_fork (PIDGET (inferior_ptid
)); /* safe recursion */
86 fp
= XZALLOC (struct fork_info
);
87 fp
->ptid
= ptid_build (pid
, pid
, 0);
88 fp
->num
= ++highest_fork_num
;
95 free_fork (struct fork_info
*fp
)
97 /* Notes on step-resume breakpoints: since this is a concern for
98 threads, let's convince ourselves that it's not a concern for
99 forks. There are two ways for a fork_info to be created. First,
100 by the checkpoint command, in which case we're at a gdb prompt
101 and there can't be any step-resume breakpoint. Second, by a fork
102 in the user program, in which case we *may* have stepped into the
103 fork call, but regardless of whether we follow the parent or the
104 child, we will return to the same place and the step-resume
105 breakpoint, if any, will take care of itself as usual. And
106 unlike threads, we do not save a private copy of the step-resume
107 breakpoint -- so we're OK. */
112 regcache_xfree (fp
->savedregs
);
120 delete_fork (ptid_t ptid
)
122 struct fork_info
*fp
, *fpprev
;
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
)
271 char path
[MAXPATHLEN
];
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
, MAXPATHLEN
, "/proc/%ld/fd", (long) PIDGET (fp
->ptid
));
286 if ((d
= opendir (path
)) != NULL
)
291 while ((de
= readdir (d
)) != NULL
)
293 /* Count open file descriptors (actually find highest
295 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
299 /* Allocate array of file positions. */
300 fp
->filepos
= xrealloc (fp
->filepos
,
301 (fp
->maxfd
+ 1) * sizeof (*fp
->filepos
));
303 /* Initialize to -1 (invalid). */
304 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
305 fp
->filepos
[tmp
] = -1;
307 /* Now find actual file positions. */
309 while ((de
= readdir (d
)) != NULL
)
310 if (isdigit (de
->d_name
[0]))
312 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
313 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
320 /* Kill 'em all, let God sort 'em out... */
323 linux_fork_killall (void)
325 /* Walk list and kill every pid. No need to treat the
326 current inferior_ptid as special (we do not return a
327 status for it) -- however any process may be a child
328 or a parent, so may get a SIGCHLD from a previously
329 killed child. Wait them all out. */
330 struct fork_info
*fp
;
334 for (fp
= fork_list
; fp
; fp
= fp
->next
)
336 pid
= PIDGET (fp
->ptid
);
338 /* Use SIGKILL instead of PTRACE_KILL because the former works even
339 if the thread is running, while the later doesn't. */
341 ret
= waitpid (pid
, &status
, 0);
342 /* We might get a SIGCHLD instead of an exit status. This is
343 aggravated by the first kill above - a child has just
344 died. MVS comment cut-and-pasted from linux-nat. */
345 } while (ret
== pid
&& WIFSTOPPED (status
));
347 init_fork_list (); /* Clear list, prepare to start fresh. */
350 /* The current inferior_ptid has exited, but there are other viable
351 forks to debug. Delete the exiting one and context-switch to the
355 linux_fork_mourn_inferior (void)
357 /* Wait just one more time to collect the inferior's exit status.
358 Do not check whether this succeeds though, since we may be
359 dealing with a process that we attached to. Such a process will
360 only report its exit status to its original parent. */
363 waitpid (ptid_get_pid (inferior_ptid
), &status
, 0);
365 /* OK, presumably inferior_ptid is the one who has exited.
366 We need to delete that one from the fork_list, and switch
367 to the next available fork. */
368 delete_fork (inferior_ptid
);
370 /* There should still be a fork - if there's only one left,
371 delete_fork won't remove it, because we haven't updated
372 inferior_ptid yet. */
373 gdb_assert (fork_list
);
375 fork_load_infrun_state (fork_list
);
376 printf_filtered (_("[Switching to %s]\n"),
377 target_pid_to_str (inferior_ptid
));
379 /* If there's only one fork, switch back to non-fork mode. */
380 if (fork_list
->next
== NULL
)
381 delete_fork (inferior_ptid
);
384 /* The current inferior_ptid is being detached, but there are other
385 viable forks to debug. Detach and delete it and context-switch to
386 the first available. */
389 linux_fork_detach (char *args
, int from_tty
)
391 /* OK, inferior_ptid is the one we are detaching from. We need to
392 delete it from the fork_list, and switch to the next available
395 if (ptrace (PTRACE_DETACH
, PIDGET (inferior_ptid
), 0, 0))
396 error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid
));
398 delete_fork (inferior_ptid
);
400 /* There should still be a fork - if there's only one left,
401 delete_fork won't remove it, because we haven't updated
402 inferior_ptid yet. */
403 gdb_assert (fork_list
);
405 fork_load_infrun_state (fork_list
);
408 printf_filtered (_("[Switching to %s]\n"),
409 target_pid_to_str (inferior_ptid
));
411 /* If there's only one fork, switch back to non-fork mode. */
412 if (fork_list
->next
== NULL
)
413 delete_fork (inferior_ptid
);
416 /* Fork list <-> user interface. */
419 delete_fork_command (char *args
, int from_tty
)
424 error (_("Requires argument (checkpoint id to delete)"));
426 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
427 if (ptid_equal (ptid
, minus_one_ptid
))
428 error (_("No such checkpoint id, %s"), args
);
430 if (ptid_equal (ptid
, inferior_ptid
))
431 error (_("Please switch to another checkpoint before deleting the current one"));
433 if (ptrace (PTRACE_KILL
, PIDGET (ptid
), 0, 0))
434 error (_("Unable to kill pid %s"), target_pid_to_str (ptid
));
437 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid
));
443 detach_fork_command (char *args
, int from_tty
)
448 error (_("Requires argument (checkpoint id to detach)"));
450 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
451 if (ptid_equal (ptid
, minus_one_ptid
))
452 error (_("No such checkpoint id, %s"), args
);
454 if (ptid_equal (ptid
, inferior_ptid
))
456 Please switch to another checkpoint before detaching the current one"));
458 if (ptrace (PTRACE_DETACH
, PIDGET (ptid
), 0, 0))
459 error (_("Unable to detach %s"), target_pid_to_str (ptid
));
462 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid
));
467 /* Print information about currently known forks. */
470 info_forks_command (char *arg
, int from_tty
)
472 struct gdbarch
*gdbarch
= get_current_arch ();
473 struct frame_info
*cur_frame
;
474 struct symtab_and_line sal
;
475 struct symtab
*cur_symtab
;
476 struct fork_info
*fp
;
480 struct fork_info
*printed
= NULL
;
483 requested
= (int) parse_and_eval_long (arg
);
485 for (fp
= fork_list
; fp
; fp
= fp
->next
)
487 if (requested
> 0 && fp
->num
!= requested
)
491 if (ptid_equal (fp
->ptid
, inferior_ptid
))
493 printf_filtered ("* ");
494 pc
= regcache_read_pc (get_current_regcache ());
498 printf_filtered (" ");
499 pc
= regcache_read_pc (fp
->savedregs
);
501 printf_filtered ("%d %s", fp
->num
, target_pid_to_str (fp
->ptid
));
503 printf_filtered (_(" (main process)"));
504 printf_filtered (_(" at "));
505 fputs_filtered (paddress (gdbarch
, pc
), gdb_stdout
);
507 sal
= find_pc_line (pc
, 0);
510 char *tmp
= strrchr (sal
.symtab
->filename
, '/');
513 printf_filtered (_(", file %s"), tmp
+ 1);
515 printf_filtered (_(", file %s"), sal
.symtab
->filename
);
518 printf_filtered (_(", line %d"), sal
.line
);
519 if (!sal
.symtab
&& !sal
.line
)
521 struct minimal_symbol
*msym
;
523 msym
= lookup_minimal_symbol_by_pc (pc
);
525 printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym
));
528 putchar_filtered ('\n');
533 printf_filtered (_("No checkpoint number %d.\n"), requested
);
535 printf_filtered (_("No checkpoints.\n"));
539 /* The PID of the process we're checkpointing. */
540 static int checkpointing_pid
= 0;
543 linux_fork_checkpointing_p (int pid
)
545 return (checkpointing_pid
== pid
);
549 checkpoint_command (char *args
, int from_tty
)
551 struct objfile
*fork_objf
;
552 struct gdbarch
*gdbarch
;
553 struct target_waitstatus last_target_waitstatus
;
554 ptid_t last_target_ptid
;
555 struct value
*fork_fn
= NULL
, *ret
;
556 struct fork_info
*fp
;
558 struct cleanup
*old_chain
;
561 /* Make the inferior fork, record its (and gdb's) state. */
563 if (lookup_minimal_symbol ("fork", NULL
, NULL
) != NULL
)
564 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
566 if (lookup_minimal_symbol ("_fork", NULL
, NULL
) != NULL
)
567 fork_fn
= find_function_in_inferior ("fork", &fork_objf
);
569 error (_("checkpoint: can't find fork function in inferior."));
571 gdbarch
= get_objfile_arch (fork_objf
);
572 ret
= value_from_longest (builtin_type (gdbarch
)->builtin_int
, 0);
574 /* Tell linux-nat.c that we're checkpointing this inferior. */
575 old_chain
= make_cleanup_restore_integer (&checkpointing_pid
);
576 checkpointing_pid
= PIDGET (inferior_ptid
);
578 ret
= call_function_by_hand (fork_fn
, 0, &ret
);
579 do_cleanups (old_chain
);
580 if (!ret
) /* Probably can't happen. */
581 error (_("checkpoint: call_function_by_hand returned null."));
583 retpid
= value_as_long (ret
);
584 get_last_target_status (&last_target_ptid
, &last_target_waitstatus
);
589 printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
593 parent_pid
= ptid_get_lwp (last_target_ptid
);
595 parent_pid
= ptid_get_pid (last_target_ptid
);
596 printf_filtered (_(" gdb says parent = %ld.\n"),
601 fp
= find_fork_pid (retpid
);
603 error (_("Failed to find new fork"));
604 fork_save_infrun_state (fp
, 1);
608 linux_fork_context (struct fork_info
*newfp
, int from_tty
)
610 /* Now we attempt to switch processes. */
611 struct fork_info
*oldfp
;
615 gdb_assert (newfp
!= NULL
);
617 oldfp
= find_fork_ptid (inferior_ptid
);
618 gdb_assert (oldfp
!= NULL
);
620 fork_save_infrun_state (oldfp
, 1);
621 remove_breakpoints ();
622 fork_load_infrun_state (newfp
);
623 insert_breakpoints ();
625 printf_filtered (_("Switching to %s\n"),
626 target_pid_to_str (inferior_ptid
));
628 print_stack_frame (get_selected_frame (NULL
), 1, SRC_AND_LOC
);
631 /* Switch inferior process (checkpoint) context, by checkpoint id. */
633 restart_command (char *args
, int from_tty
)
635 struct fork_info
*fp
;
638 error (_("Requires argument (checkpoint id to restart)"));
640 if ((fp
= find_fork_id (parse_and_eval_long (args
))) == NULL
)
641 error (_("Not found: checkpoint id %s"), args
);
643 linux_fork_context (fp
, from_tty
);
647 _initialize_linux_fork (void)
651 /* Set/show detach-on-fork: user-settable mode. */
653 add_setshow_boolean_cmd ("detach-on-fork", class_obscure
, &detach_fork
, _("\
654 Set whether gdb will detach the child of a fork."), _("\
655 Show whether gdb will detach the child of a fork."), _("\
656 Tells gdb whether to detach the child of a fork."),
657 NULL
, NULL
, &setlist
, &showlist
);
659 /* Set/show restart-auto-finish: user-settable count. Causes the
660 first "restart" of a fork to do some number of "finish" commands
661 before returning to user.
663 Useful because otherwise the virgin fork process will be stopped
664 somewhere in the un-interesting fork system call. */
666 /* Checkpoint command: create a fork of the inferior process
667 and set it aside for later debugging. */
669 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
670 Fork a duplicate process (experimental)."));
672 /* Restart command: restore the context of a specified checkpoint
675 add_com ("restart", class_obscure
, restart_command
, _("\
676 restart <n>: restore program context from a checkpoint.\n\
677 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
679 /* Delete checkpoint command: kill the process and remove it from
682 add_cmd ("checkpoint", class_obscure
, delete_fork_command
, _("\
683 Delete a checkpoint (experimental)."),
686 /* Detach checkpoint command: release the process to run independently,
687 and remove it from the fork list. */
689 add_cmd ("checkpoint", class_obscure
, detach_fork_command
, _("\
690 Detach from a checkpoint (experimental)."),
693 /* Info checkpoints command: list all forks/checkpoints
694 currently under gdb's control. */
696 add_info ("checkpoints", info_forks_command
,
697 _("IDs of currently known checkpoints."));