Fake VFORK_DONE events when following only the parent after a vfork.
FreeBSD does not currently report a ptrace event for a parent process after it resumes due to the child exiting the shared memory region after a vfork. Take the same approach used in linux-nat.c in this case of sleeping for a while and then reporting a fake VFORK_DONE event. gdb/ChangeLog: * fbsd-nat.c (struct fbsd_fork_child_info): Rename to ... (struct fbsd_fork_info): ... this. (struct fbsd_fork_info) <child>: Rename to ... (struct fbsd_fork_info) <ptid>: ... this. (fbsd_pending_children): Update type. (fbsd_remember_child): Update type and field name. (fbsd_is_child_pending): Likewise. (fbsd_pending_vfork_done): New variable. (fbsd_is_vfork_done_pending): New function. (fbsd_next_vfork_done): New function. (fbsd_resume): Don't resume processes with a pending vfork done event. (fbsd_wait): Report pending vfork done events. (fbsd_follow_fork): Delay and record a pending vfork done event for a vfork parent when detaching the child.
This commit is contained in:
John Baldwin
parent
8607ea632c
commit
2c5c2a3321
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@ -1,3 +1,21 @@
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2016-07-01 John Baldwin <jhb@FreeBSD.org>
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* fbsd-nat.c (struct fbsd_fork_child_info): Rename to ...
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(struct fbsd_fork_info): ... this.
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(struct fbsd_fork_info) <child>: Rename to ...
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(struct fbsd_fork_info) <ptid>: ... this.
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(fbsd_pending_children): Update type.
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(fbsd_remember_child): Update type and field name.
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(fbsd_is_child_pending): Likewise.
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(fbsd_pending_vfork_done): New variable.
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(fbsd_is_vfork_done_pending): New function.
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(fbsd_next_vfork_done): New function.
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(fbsd_resume): Don't resume processes with a pending vfork done
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event.
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(fbsd_wait): Report pending vfork done events.
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(fbsd_follow_fork): Delay and record a pending vfork done event
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for a vfork parent when detaching the child.
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2016-07-01 John Baldwin <jhb@FreeBSD.org>
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* fbsd-nat.c (super_resume): Move earlier next to "super_wait".
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112
gdb/fbsd-nat.c
112
gdb/fbsd-nat.c
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@ -530,13 +530,13 @@ fbsd_update_thread_list (struct target_ops *ops)
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sake. FreeBSD versions newer than 9.1 contain both fixes.
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*/
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struct fbsd_fork_child_info
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struct fbsd_fork_info
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{
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struct fbsd_fork_child_info *next;
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ptid_t child; /* Pid of new child. */
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struct fbsd_fork_info *next;
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ptid_t ptid;
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};
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static struct fbsd_fork_child_info *fbsd_pending_children;
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static struct fbsd_fork_info *fbsd_pending_children;
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/* Record a new child process event that is reported before the
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corresponding fork event in the parent. */
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@ -544,9 +544,9 @@ static struct fbsd_fork_child_info *fbsd_pending_children;
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static void
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fbsd_remember_child (ptid_t pid)
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{
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struct fbsd_fork_child_info *info = XCNEW (struct fbsd_fork_child_info);
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struct fbsd_fork_info *info = XCNEW (struct fbsd_fork_info);
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info->child = pid;
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info->ptid = pid;
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info->next = fbsd_pending_children;
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fbsd_pending_children = info;
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}
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@ -557,25 +557,74 @@ fbsd_remember_child (ptid_t pid)
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static ptid_t
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fbsd_is_child_pending (pid_t pid)
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{
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struct fbsd_fork_child_info *info, *prev;
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struct fbsd_fork_info *info, *prev;
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ptid_t ptid;
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prev = NULL;
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for (info = fbsd_pending_children; info; prev = info, info = info->next)
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{
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if (ptid_get_pid (info->child) == pid)
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if (ptid_get_pid (info->ptid) == pid)
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{
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if (prev == NULL)
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fbsd_pending_children = info->next;
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else
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prev->next = info->next;
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ptid = info->child;
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ptid = info->ptid;
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xfree (info);
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return ptid;
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}
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}
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return null_ptid;
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}
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static struct fbsd_fork_info *fbsd_pending_vfork_done;
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/* Record a pending vfork done event. */
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static void
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fbsd_add_vfork_done (ptid_t pid)
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{
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struct fbsd_fork_info *info = XCNEW (struct fbsd_fork_info);
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info->ptid = pid;
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info->next = fbsd_pending_vfork_done;
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fbsd_pending_vfork_done = info;
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}
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/* Check for a pending vfork done event for a specific PID. */
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static int
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fbsd_is_vfork_done_pending (pid_t pid)
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{
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struct fbsd_fork_info *info;
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for (info = fbsd_pending_vfork_done; info != NULL; info = info->next)
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{
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if (ptid_get_pid (info->ptid) == pid)
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return 1;
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}
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return 0;
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}
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/* Check for a pending vfork done event. If one is found, remove it
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from the list and return the PTID. */
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static ptid
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fbsd_next_vfork_done (void)
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{
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struct fbsd_fork_info *info;
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ptid_t ptid;
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if (fbsd_pending_vfork_done != NULL)
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{
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info = fbsd_pending_vfork_done;
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fbsd_pending_vfork_done = info->next;
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ptid = info->ptid;
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xfree (info);
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return ptid;
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}
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return null_ptid;
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}
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#endif
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static int
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@ -616,6 +665,17 @@ static void
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fbsd_resume (struct target_ops *ops,
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ptid_t ptid, int step, enum gdb_signal signo)
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{
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#ifdef TDP_RFPPWAIT
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pid_t pid;
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/* Don't PT_CONTINUE a process which has a pending vfork done event. */
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if (ptid_equal (minus_one_ptid, ptid))
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pid = ptid_get_pid (inferior_ptid);
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else
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pid = ptid_get_pid (ptid);
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if (fbsd_is_vfork_done_pending (pid))
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return;
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#endif
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if (debug_fbsd_lwp)
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fprintf_unfiltered (gdb_stdlog,
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@ -650,6 +710,12 @@ fbsd_wait (struct target_ops *ops,
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while (1)
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{
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wptid = fbsd_next_vfork_done ();
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if (!ptid_equal (wptid, null_ptid))
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{
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ourstatus->kind = TARGET_WAITKIND_VFORK_DONE;
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return wptid;
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}
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wptid = super_wait (ops, ptid, ourstatus, target_options);
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if (ourstatus->kind == TARGET_WAITKIND_STOPPED)
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{
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@ -828,6 +894,7 @@ fbsd_follow_fork (struct target_ops *ops, int follow_child,
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if (!follow_child && detach_fork)
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{
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struct thread_info *tp = inferior_thread ();
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int has_vforked = tp->pending_follow.kind == TARGET_WAITKIND_VFORKED;
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pid_t child_pid = ptid_get_pid (tp->pending_follow.value.related_pid);
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/* Breakpoints have already been detached from the child by
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@ -835,6 +902,33 @@ fbsd_follow_fork (struct target_ops *ops, int follow_child,
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if (ptrace (PT_DETACH, child_pid, (PTRACE_TYPE_ARG3)1, 0) == -1)
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perror_with_name (("ptrace"));
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if (has_vforked)
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{
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/* We can't insert breakpoints until the child process has
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finished with the shared memory region. The parent
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process doesn't wait for the child process to exit or
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exec until after it has been resumed from the ptrace stop
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to report the fork. Once it has been resumed it doesn't
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stop again before returning to userland, so there is no
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reliable way to wait on the parent.
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We can't stay attached to the child to wait for an exec
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or exit because it may invoke ptrace(PT_TRACE_ME)
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(e.g. if the parent process is a debugger forking a new
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child process).
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In the end, the best we can do is to make sure it runs
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for a little while. Hopefully it will be out of range of
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any breakpoints we reinsert. Usually this is only the
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single-step breakpoint at vfork's return point. */
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usleep (10000);
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/* Schedule a fake VFORK_DONE event to report on the next
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wait. */
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fbsd_add_vfork_done (inferior_ptid);
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}
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}
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return 0;
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