1 /* GNU/Linux native-dependent code for debugging multiple forks.
3 Copyright (C) 2005-2015 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 /* Add a fork to the internal fork list. */
73 if (fork_list == NULL && pid != ptid_get_pid (inferior_ptid))
75 /* Special case -- if this is the first fork in the list
76 (the list is hitherto empty), and if this new fork is
77 NOT the current inferior_ptid, then add inferior_ptid
78 first, as a special zeroeth fork id. */
79 highest_fork_num = -1;
80 add_fork (ptid_get_pid (inferior_ptid)); /* safe recursion */
83 fp = XCNEW (struct fork_info);
84 fp->ptid = ptid_build (pid, pid, 0);
85 fp->num = ++highest_fork_num;
92 free_fork (struct fork_info *fp)
94 /* Notes on step-resume breakpoints: since this is a concern for
95 threads, let's convince ourselves that it's not a concern for
96 forks. There are two ways for a fork_info to be created. First,
97 by the checkpoint command, in which case we're at a gdb prompt
98 and there can't be any step-resume breakpoint. Second, by a fork
99 in the user program, in which case we *may* have stepped into the
100 fork call, but regardless of whether we follow the parent or the
101 child, we will return to the same place and the step-resume
102 breakpoint, if any, will take care of itself as usual. And
103 unlike threads, we do not save a private copy of the step-resume
104 breakpoint -- so we're OK. */
109 regcache_xfree (fp->savedregs);
117 delete_fork (ptid_t ptid)
119 struct fork_info *fp, *fpprev;
123 linux_nat_forget_process (ptid_get_pid (ptid));
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)
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, PATH_MAX, "/proc/%ld/fd",
285 (long) ptid_get_pid (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 = XRESIZEVEC (off_t, fp->filepos, fp->maxfd + 1);
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 = ptid_get_pid (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 (const 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, ptid_get_pid (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);
416 inferior_call_waitpid_cleanup (void *fp)
418 struct fork_info *oldfp = fp;
422 /* Switch back to inferior_ptid. */
423 remove_breakpoints ();
424 fork_load_infrun_state (oldfp);
425 insert_breakpoints ();
430 inferior_call_waitpid (ptid_t pptid, int pid)
432 struct objfile *waitpid_objf;
433 struct value *waitpid_fn = NULL;
434 struct value *argv[4], *retv;
435 struct gdbarch *gdbarch = get_current_arch ();
436 struct fork_info *oldfp = NULL, *newfp = NULL;
437 struct cleanup *old_cleanup;
440 if (!ptid_equal (pptid, inferior_ptid))
442 /* Switch to pptid. */
443 oldfp = find_fork_ptid (inferior_ptid);
444 gdb_assert (oldfp != NULL);
445 newfp = find_fork_ptid (pptid);
446 gdb_assert (newfp != NULL);
447 fork_save_infrun_state (oldfp, 1);
448 remove_breakpoints ();
449 fork_load_infrun_state (newfp);
450 insert_breakpoints ();
453 old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
455 /* Get the waitpid_fn. */
456 if (lookup_minimal_symbol ("waitpid", NULL, NULL).minsym != NULL)
457 waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
459 && lookup_minimal_symbol ("_waitpid", NULL, NULL).minsym != NULL)
460 waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
465 argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
466 argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
467 argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
470 retv = call_function_by_hand (waitpid_fn, 3, argv);
471 if (value_as_long (retv) < 0)
477 do_cleanups (old_cleanup);
481 /* Fork list <-> user interface. */
484 delete_checkpoint_command (char *args, int from_tty)
487 struct fork_info *fi;
490 error (_("Requires argument (checkpoint id to delete)"));
492 ptid = fork_id_to_ptid (parse_and_eval_long (args));
493 if (ptid_equal (ptid, minus_one_ptid))
494 error (_("No such checkpoint id, %s"), args);
496 if (ptid_equal (ptid, inferior_ptid))
498 Please switch to another checkpoint before deleting the current one"));
500 if (ptrace (PTRACE_KILL, ptid_get_pid (ptid), 0, 0))
501 error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
503 fi = find_fork_ptid (ptid);
505 pptid = fi->parent_ptid;
508 printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
512 /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
513 list, waitpid the ptid.
514 If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
516 if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
517 || (find_thread_ptid (pptid) && is_stopped (pptid)))
519 if (inferior_call_waitpid (pptid, ptid_get_pid (ptid)))
520 warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
525 detach_checkpoint_command (char *args, int from_tty)
530 error (_("Requires argument (checkpoint id to detach)"));
532 ptid = fork_id_to_ptid (parse_and_eval_long (args));
533 if (ptid_equal (ptid, minus_one_ptid))
534 error (_("No such checkpoint id, %s"), args);
536 if (ptid_equal (ptid, inferior_ptid))
538 Please switch to another checkpoint before detaching the current one"));
540 if (ptrace (PTRACE_DETACH, ptid_get_pid (ptid), 0, 0))
541 error (_("Unable to detach %s"), target_pid_to_str (ptid));
544 printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
549 /* Print information about currently known checkpoints. */
552 info_checkpoints_command (char *arg, int from_tty)
554 struct gdbarch *gdbarch = get_current_arch ();
555 struct symtab_and_line sal;
556 struct fork_info *fp;
559 struct fork_info *printed = NULL;
562 requested = (int) parse_and_eval_long (arg);
564 for (fp = fork_list; fp; fp = fp->next)
566 if (requested > 0 && fp->num != requested)
570 if (ptid_equal (fp->ptid, inferior_ptid))
572 printf_filtered ("* ");
573 pc = regcache_read_pc (get_current_regcache ());
577 printf_filtered (" ");
578 pc = regcache_read_pc (fp->savedregs);
580 printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
582 printf_filtered (_(" (main process)"));
583 printf_filtered (_(" at "));
584 fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
586 sal = find_pc_line (pc, 0);
588 printf_filtered (_(", file %s"),
589 symtab_to_filename_for_display (sal.symtab));
591 printf_filtered (_(", line %d"), sal.line);
592 if (!sal.symtab && !sal.line)
594 struct bound_minimal_symbol msym;
596 msym = lookup_minimal_symbol_by_pc (pc);
598 printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym.minsym));
601 putchar_filtered ('\n');
606 printf_filtered (_("No checkpoint number %d.\n"), requested);
608 printf_filtered (_("No checkpoints.\n"));
612 /* The PID of the process we're checkpointing. */
613 static int checkpointing_pid = 0;
616 linux_fork_checkpointing_p (int pid)
618 return (checkpointing_pid == pid);
621 /* Callback for iterate over threads. Used to check whether
622 the current inferior is multi-threaded. Returns true as soon
623 as it sees the second thread of the current inferior. */
626 inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
628 int *count_p = (int *) data;
630 if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
633 /* Stop the iteration if multiple threads have been detected. */
637 /* Return true if the current inferior is multi-threaded. */
640 inf_has_multiple_threads (void)
644 iterate_over_threads (inf_has_multiple_thread_cb, &count);
649 checkpoint_command (char *args, int from_tty)
651 struct objfile *fork_objf;
652 struct gdbarch *gdbarch;
653 struct target_waitstatus last_target_waitstatus;
654 ptid_t last_target_ptid;
655 struct value *fork_fn = NULL, *ret;
656 struct fork_info *fp;
658 struct cleanup *old_chain;
660 if (!target_has_execution)
661 error (_("The program is not being run."));
663 /* Ensure that the inferior is not multithreaded. */
664 update_thread_list ();
665 if (inf_has_multiple_threads ())
666 error (_("checkpoint: can't checkpoint multiple threads."));
668 /* Make the inferior fork, record its (and gdb's) state. */
670 if (lookup_minimal_symbol ("fork", NULL, NULL).minsym != NULL)
671 fork_fn = find_function_in_inferior ("fork", &fork_objf);
673 if (lookup_minimal_symbol ("_fork", NULL, NULL).minsym != NULL)
674 fork_fn = find_function_in_inferior ("fork", &fork_objf);
676 error (_("checkpoint: can't find fork function in inferior."));
678 gdbarch = get_objfile_arch (fork_objf);
679 ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
681 /* Tell linux-nat.c that we're checkpointing this inferior. */
682 old_chain = make_cleanup_restore_integer (&checkpointing_pid);
683 checkpointing_pid = ptid_get_pid (inferior_ptid);
685 ret = call_function_by_hand (fork_fn, 0, &ret);
686 do_cleanups (old_chain);
687 if (!ret) /* Probably can't happen. */
688 error (_("checkpoint: call_function_by_hand returned null."));
690 retpid = value_as_long (ret);
691 get_last_target_status (&last_target_ptid, &last_target_waitstatus);
693 fp = find_fork_pid (retpid);
699 printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
700 fp != NULL ? fp->num : -1, (long) retpid);
703 parent_pid = ptid_get_lwp (last_target_ptid);
705 parent_pid = ptid_get_pid (last_target_ptid);
706 printf_filtered (_(" gdb says parent = %ld.\n"),
712 error (_("Failed to find new fork"));
713 fork_save_infrun_state (fp, 1);
714 fp->parent_ptid = last_target_ptid;
718 linux_fork_context (struct fork_info *newfp, int from_tty)
720 /* Now we attempt to switch processes. */
721 struct fork_info *oldfp;
723 gdb_assert (newfp != NULL);
725 oldfp = find_fork_ptid (inferior_ptid);
726 gdb_assert (oldfp != NULL);
728 fork_save_infrun_state (oldfp, 1);
729 remove_breakpoints ();
730 fork_load_infrun_state (newfp);
731 insert_breakpoints ();
733 printf_filtered (_("Switching to %s\n"),
734 target_pid_to_str (inferior_ptid));
736 print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
739 /* Switch inferior process (checkpoint) context, by checkpoint id. */
741 restart_command (char *args, int from_tty)
743 struct fork_info *fp;
746 error (_("Requires argument (checkpoint id to restart)"));
748 if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
749 error (_("Not found: checkpoint id %s"), args);
751 linux_fork_context (fp, from_tty);
755 _initialize_linux_fork (void)
759 /* Checkpoint command: create a fork of the inferior process
760 and set it aside for later debugging. */
762 add_com ("checkpoint", class_obscure, checkpoint_command, _("\
763 Fork a duplicate process (experimental)."));
765 /* Restart command: restore the context of a specified checkpoint
768 add_com ("restart", class_obscure, restart_command, _("\
769 restart <n>: restore program context from a checkpoint.\n\
770 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
772 /* Delete checkpoint command: kill the process and remove it from
775 add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\
776 Delete a checkpoint (experimental)."),
779 /* Detach checkpoint command: release the process to run independently,
780 and remove it from the fork list. */
782 add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\
783 Detach from a checkpoint (experimental)."),
786 /* Info checkpoints command: list all forks/checkpoints
787 currently under gdb's control. */
789 add_info ("checkpoints", info_checkpoints_command,
790 _("IDs of currently known checkpoints."));