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."));