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 the internal fork list. */
75 if (fork_list
== NULL
&& pid
!= PIDGET (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 (PIDGET (inferior_ptid
)); /* safe recursion */
85 fp
= XZALLOC (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 for (fp
= fork_list
; fp
; fpprev
= fp
, fp
= fp
->next
)
126 if (ptid_equal (fp
->ptid
, ptid
))
133 fpprev
->next
= fp
->next
;
135 fork_list
= fp
->next
;
139 /* Special case: if there is now only one process in the list,
140 and if it is (hopefully!) the current inferior_ptid, then
141 remove it, leaving the list empty -- we're now down to the
142 default case of debugging a single process. */
143 if (fork_list
!= NULL
&& fork_list
->next
== NULL
&&
144 ptid_equal (fork_list
->ptid
, inferior_ptid
))
146 /* Last fork -- delete from list and handle as solo process
147 (should be a safe recursion). */
148 delete_fork (inferior_ptid
);
152 /* Find a fork_info by matching PTID. */
153 static struct fork_info
*
154 find_fork_ptid (ptid_t ptid
)
156 struct fork_info
*fp
;
158 for (fp
= fork_list
; fp
; fp
= fp
->next
)
159 if (ptid_equal (fp
->ptid
, ptid
))
165 /* Find a fork_info by matching ID. */
166 static struct fork_info
*
167 find_fork_id (int num
)
169 struct fork_info
*fp
;
171 for (fp
= fork_list
; fp
; fp
= fp
->next
)
178 /* Find a fork_info by matching pid. */
179 extern struct fork_info
*
180 find_fork_pid (pid_t pid
)
182 struct fork_info
*fp
;
184 for (fp
= fork_list
; fp
; fp
= fp
->next
)
185 if (pid
== ptid_get_pid (fp
->ptid
))
192 fork_id_to_ptid (int num
)
194 struct fork_info
*fork
= find_fork_id (num
);
198 return pid_to_ptid (-1);
202 init_fork_list (void)
204 struct fork_info
*fp
, *fpnext
;
209 for (fp
= fork_list
; fp
; fp
= fpnext
)
218 /* Fork list <-> gdb interface. */
220 /* Utility function for fork_load/fork_save.
221 Calls lseek in the (current) inferior process. */
224 call_lseek (int fd
, off_t offset
, int whence
)
228 snprintf (&exp
[0], sizeof (exp
), "lseek (%d, %ld, %d)",
229 fd
, (long) offset
, whence
);
230 return (off_t
) parse_and_eval_long (&exp
[0]);
233 /* Load infrun state for the fork PTID. */
236 fork_load_infrun_state (struct fork_info
*fp
)
238 extern void nullify_last_target_wait_ptid ();
241 linux_nat_switch_fork (fp
->ptid
);
243 if (fp
->savedregs
&& fp
->clobber_regs
)
244 regcache_cpy (get_current_regcache (), fp
->savedregs
);
246 registers_changed ();
247 reinit_frame_cache ();
249 stop_pc
= regcache_read_pc (get_current_regcache ());
250 nullify_last_target_wait_ptid ();
252 /* Now restore the file positions of open file descriptors. */
255 for (i
= 0; i
<= fp
->maxfd
; i
++)
256 if (fp
->filepos
[i
] != (off_t
) -1)
257 call_lseek (i
, fp
->filepos
[i
], SEEK_SET
);
258 /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
259 this is native-only. If it ever has to be cross, we'll have
264 /* Save infrun state for the fork PTID.
265 Exported for use by linux child_follow_fork. */
268 fork_save_infrun_state (struct fork_info
*fp
, int clobber_regs
)
270 char path
[MAXPATHLEN
];
275 regcache_xfree (fp
->savedregs
);
277 fp
->savedregs
= regcache_dup (get_current_regcache ());
278 fp
->clobber_regs
= clobber_regs
;
282 /* Now save the 'state' (file position) of all open file descriptors.
283 Unfortunately fork does not take care of that for us... */
284 snprintf (path
, MAXPATHLEN
, "/proc/%ld/fd", (long) PIDGET (fp
->ptid
));
285 if ((d
= opendir (path
)) != NULL
)
290 while ((de
= readdir (d
)) != NULL
)
292 /* Count open file descriptors (actually find highest
294 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
298 /* Allocate array of file positions. */
299 fp
->filepos
= xrealloc (fp
->filepos
,
300 (fp
->maxfd
+ 1) * sizeof (*fp
->filepos
));
302 /* Initialize to -1 (invalid). */
303 for (tmp
= 0; tmp
<= fp
->maxfd
; tmp
++)
304 fp
->filepos
[tmp
] = -1;
306 /* Now find actual file positions. */
308 while ((de
= readdir (d
)) != NULL
)
309 if (isdigit (de
->d_name
[0]))
311 tmp
= strtol (&de
->d_name
[0], NULL
, 10);
312 fp
->filepos
[tmp
] = call_lseek (tmp
, 0, SEEK_CUR
);
319 /* Kill 'em all, let God sort 'em out... */
322 linux_fork_killall (void)
324 /* Walk list and kill every pid. No need to treat the
325 current inferior_ptid as special (we do not return a
326 status for it) -- however any process may be a child
327 or a parent, so may get a SIGCHLD from a previously
328 killed child. Wait them all out. */
329 struct fork_info
*fp
;
333 for (fp
= fork_list
; fp
; fp
= fp
->next
)
335 pid
= PIDGET (fp
->ptid
);
337 /* Use SIGKILL instead of PTRACE_KILL because the former works even
338 if the thread is running, while the later doesn't. */
340 ret
= waitpid (pid
, &status
, 0);
341 /* We might get a SIGCHLD instead of an exit status. This is
342 aggravated by the first kill above - a child has just
343 died. MVS comment cut-and-pasted from linux-nat. */
344 } while (ret
== pid
&& WIFSTOPPED (status
));
346 init_fork_list (); /* Clear list, prepare to start fresh. */
349 /* The current inferior_ptid has exited, but there are other viable
350 forks to debug. Delete the exiting one and context-switch to the
354 linux_fork_mourn_inferior (void)
356 /* Wait just one more time to collect the inferior's exit status.
357 Do not check whether this succeeds though, since we may be
358 dealing with a process that we attached to. Such a process will
359 only report its exit status to its original parent. */
362 waitpid (ptid_get_pid (inferior_ptid
), &status
, 0);
364 /* OK, presumably inferior_ptid is the one who has exited.
365 We need to delete that one from the fork_list, and switch
366 to the next available fork. */
367 delete_fork (inferior_ptid
);
369 /* There should still be a fork - if there's only one left,
370 delete_fork won't remove it, because we haven't updated
371 inferior_ptid yet. */
372 gdb_assert (fork_list
);
374 fork_load_infrun_state (fork_list
);
375 printf_filtered (_("[Switching to %s]\n"),
376 target_pid_to_str (inferior_ptid
));
378 /* If there's only one fork, switch back to non-fork mode. */
379 if (fork_list
->next
== NULL
)
380 delete_fork (inferior_ptid
);
383 /* The current inferior_ptid is being detached, but there are other
384 viable forks to debug. Detach and delete it and context-switch to
385 the first available. */
388 linux_fork_detach (char *args
, int from_tty
)
390 /* OK, inferior_ptid is the one we are detaching from. We need to
391 delete it from the fork_list, and switch to the next available
394 if (ptrace (PTRACE_DETACH
, PIDGET (inferior_ptid
), 0, 0))
395 error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid
));
397 delete_fork (inferior_ptid
);
399 /* There should still be a fork - if there's only one left,
400 delete_fork won't remove it, because we haven't updated
401 inferior_ptid yet. */
402 gdb_assert (fork_list
);
404 fork_load_infrun_state (fork_list
);
407 printf_filtered (_("[Switching to %s]\n"),
408 target_pid_to_str (inferior_ptid
));
410 /* If there's only one fork, switch back to non-fork mode. */
411 if (fork_list
->next
== NULL
)
412 delete_fork (inferior_ptid
);
415 /* Fork list <-> user interface. */
418 delete_checkpoint_command (char *args
, int from_tty
)
423 error (_("Requires argument (checkpoint id to delete)"));
425 ptid
= fork_id_to_ptid (parse_and_eval_long (args
));
426 if (ptid_equal (ptid
, minus_one_ptid
))
427 error (_("No such checkpoint id, %s"), args
);
429 if (ptid_equal (ptid
, inferior_ptid
))
431 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_checkpoint_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 checkpoints. */
470 info_checkpoints_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 /* Checkpoint command: create a fork of the inferior process
660 and set it aside for later debugging. */
662 add_com ("checkpoint", class_obscure
, checkpoint_command
, _("\
663 Fork a duplicate process (experimental)."));
665 /* Restart command: restore the context of a specified checkpoint
668 add_com ("restart", class_obscure
, restart_command
, _("\
669 restart <n>: restore program context from a checkpoint.\n\
670 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
672 /* Delete checkpoint command: kill the process and remove it from
675 add_cmd ("checkpoint", class_obscure
, delete_checkpoint_command
, _("\
676 Delete a checkpoint (experimental)."),
679 /* Detach checkpoint command: release the process to run independently,
680 and remove it from the fork list. */
682 add_cmd ("checkpoint", class_obscure
, detach_checkpoint_command
, _("\
683 Detach from a checkpoint (experimental)."),
686 /* Info checkpoints command: list all forks/checkpoints
687 currently under gdb's control. */
689 add_info ("checkpoints", info_checkpoints_command
,
690 _("IDs of currently known checkpoints."));