[PATCH 3/3] Use a real vfork done event on FreeBSD when available.

[PATCH 3/3] Use a real vfork done event on FreeBSD when available.

[John Baldwin]

FreeBSD 12 recently added a new ptrace event to indicate when the vfork
parent resumes after the child process stops sharing the address space.
Use this event to report a proper TARGET_WAITKIND_VFORK_DONE rather than
faking a vfork done event after a delay.

gdb/ChangeLog:

	* fbsd-nat.c (fbsd_enable_proc_events): Enable "PTRACE_VFORK"
	events.
	(fbsd_pending_vfork_done): Only define if "PTRACE_VFORK" is not
	defined.
	(fbsd_add_vfork_done): Likewise.
	(fbsd_is_vfork_done_pending): Likewise.
	(fbsd_next_vfork_done): Likewise.
	(fbsd_resume): Only ignore pending vfork done events if
	"PTRACE_VFORK" is not defined.
	(fbsd_wait): Only look for pending vfork done events if
	"PTRACE_VFORK" is not defined.
	[PTRACE_VFORK]: Handle "PL_FLAG_VFORKED" and "PL_FLAG_VFORK_DONE"
	events.
	(fbsd_follow_fork): Only fake a vfork done event if "PTRACE_VFORK"
	is not defined.
---
 gdb/ChangeLog  | 18 ++++++++++++++++++
 gdb/fbsd-nat.c | 30 +++++++++++++++++++++++++++---
 2 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 33cd6a7..f11871c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,23 @@
 2016-07-15  John Baldwin  <jhb@FreeBSD.org>
 
+	* fbsd-nat.c (fbsd_enable_proc_events): Enable "PTRACE_VFORK"
+	events.
+	(fbsd_pending_vfork_done): Only define if "PTRACE_VFORK" is not
+	defined.
+	(fbsd_add_vfork_done): Likewise.
+	(fbsd_is_vfork_done_pending): Likewise.
+	(fbsd_next_vfork_done): Likewise.
+	(fbsd_resume): Only ignore pending vfork done events if
+	"PTRACE_VFORK" is not defined.
+	(fbsd_wait): Only look for pending vfork done events if
+	"PTRACE_VFORK" is not defined.
+	[PTRACE_VFORK]: Handle "PL_FLAG_VFORKED" and "PL_FLAG_VFORK_DONE"
+	events.
+	(fbsd_follow_fork): Only fake a vfork done event if "PTRACE_VFORK"
+	is not defined.
+
+2016-07-15  John Baldwin  <jhb@FreeBSD.org>
+
 	* fbsd-nat.c (fbsd_wait): Use "fbsd_enable_proc_events" on
 	new child processes.
 
diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index 5e4304e..ade62f1 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -435,6 +435,9 @@ fbsd_enable_proc_events (pid_t pid)
 	      sizeof (events)) == -1)
     perror_with_name (("ptrace"));
   events |= PTRACE_FORK | PTRACE_LWP;
+#ifdef PTRACE_VFORK
+  events |= PTRACE_VFORK;
+#endif
   if (ptrace (PT_SET_EVENT_MASK, pid, (PTRACE_TYPE_ARG3)&events,
 	      sizeof (events)) == -1)
     perror_with_name (("ptrace"));
@@ -598,6 +601,7 @@ fbsd_is_child_pending (pid_t pid)
   return null_ptid;
 }
 
+#ifndef PTRACE_VFORK
 static struct fbsd_fork_info *fbsd_pending_vfork_done;
 
 /* Record a pending vfork done event.  */
@@ -647,6 +651,7 @@ fbsd_next_vfork_done (void)
   return null_ptid;
 }
 #endif
+#endif
 
 static int
 resume_one_thread_cb (struct thread_info *tp, void *data)
@@ -686,7 +691,7 @@ static void
 fbsd_resume (struct target_ops *ops,
 	     ptid_t ptid, int step, enum gdb_signal signo)
 {
-#ifdef TDP_RFPPWAIT
+#if defined(TDP_RFPPWAIT) && !defined(PTRACE_VFORK)
   pid_t pid;
 
   /* Don't PT_CONTINUE a process which has a pending vfork done event.  */
@@ -731,12 +736,14 @@ fbsd_wait (struct target_ops *ops,
 
   while (1)
     {
+#ifndef PTRACE_VFORK
       wptid = fbsd_next_vfork_done ();
       if (!ptid_equal (wptid, null_ptid))
 	{
 	  ourstatus->kind = TARGET_WAITKIND_VFORK_DONE;
 	  return wptid;
 	}
+#endif
       wptid = super_wait (ops, ptid, ourstatus, target_options);
       if (ourstatus->kind == TARGET_WAITKIND_STOPPED)
 	{
@@ -812,12 +819,18 @@ fbsd_wait (struct target_ops *ops,
 #ifdef TDP_RFPPWAIT
 	  if (pl.pl_flags & PL_FLAG_FORKED)
 	    {
+#ifndef PTRACE_VFORK
 	      struct kinfo_proc kp;
+#endif
 	      ptid_t child_ptid;
 	      pid_t child;
 
 	      child = pl.pl_child_pid;
 	      ourstatus->kind = TARGET_WAITKIND_FORKED;
+#ifdef PTRACE_VFORK
+	      if (pl.pl_flags & PL_FLAG_VFORKED)
+		ourstatus->kind = TARGET_WAITKIND_VFORKED;
+#endif
 
 	      /* Make sure the other end of the fork is stopped too.  */
 	      child_ptid = fbsd_is_child_pending (child);
@@ -839,11 +852,13 @@ fbsd_wait (struct target_ops *ops,
 	      /* Enable additional events on the child process.  */
 	      fbsd_enable_proc_events (ptid_get_pid (child_ptid));
 
+#ifndef PTRACE_VFORK
 	      /* For vfork, the child process will have the P_PPWAIT
 		 flag set.  */
 	      fbsd_fetch_kinfo_proc (child, &kp);
 	      if (kp.ki_flag & P_PPWAIT)
 		ourstatus->kind = TARGET_WAITKIND_VFORKED;
+#endif
 	      ourstatus->value.related_pid = child_ptid;
 
 	      return wptid;
@@ -857,6 +872,14 @@ fbsd_wait (struct target_ops *ops,
 	      fbsd_remember_child (wptid);
 	      continue;
 	    }
+
+#ifdef PTRACE_VFORK
+	  if (pl.pl_flags & PL_FLAG_VFORK_DONE)
+	    {
+	      ourstatus->kind = TARGET_WAITKIND_VFORK_DONE;
+	      return wptid;
+	    }
+#endif
 #endif
 
 #ifdef PL_FLAG_EXEC
@@ -918,7 +941,6 @@ fbsd_follow_fork (struct target_ops *ops, int follow_child,
   if (!follow_child && detach_fork)
     {
       struct thread_info *tp = inferior_thread ();
-      int has_vforked = tp->pending_follow.kind == TARGET_WAITKIND_VFORKED;
       pid_t child_pid = ptid_get_pid (tp->pending_follow.value.related_pid);
 
       /* Breakpoints have already been detached from the child by
@@ -927,7 +949,8 @@ fbsd_follow_fork (struct target_ops *ops, int follow_child,
       if (ptrace (PT_DETACH, child_pid, (PTRACE_TYPE_ARG3)1, 0) == -1)
 	perror_with_name (("ptrace"));
 
-      if (has_vforked)
+#ifndef PTRACE_VFORK
+      if (tp->pending_follow.kind == TARGET_WAITKIND_VFORKED)
 	{
 	  /* We can't insert breakpoints until the child process has
 	     finished with the shared memory region.  The parent
@@ -953,6 +976,7 @@ fbsd_follow_fork (struct target_ops *ops, int follow_child,
 	     wait.  */
 	  fbsd_add_vfork_done (inferior_ptid);
 	}
+#endif
     }
 
   return 0;
-- 
2.8.4

[PATCH 0/3] Add "real" vfork done handling on FreeBSD

[John Baldwin]

FreeBSD 12 recently gained a real vfork done event via ptrace(2).
This changes the FreeBSD native targets to use this when it exists
instead of faking a done event after a sleep.

John Baldwin (3):
  Consolidate code to enable optional FreeBSD native target event
    reporting.
  Enable ptrace events on new child processes.
  Use a real vfork done event on FreeBSD when available.

 gdb/ChangeLog  | 31 ++++++++++++++++++++
 gdb/fbsd-nat.c | 92 ++++++++++++++++++++++++++++++++++++----------------------
 2 files changed, 89 insertions(+), 34 deletions(-)

-- 
2.8.4

[PATCH 2/3] Enable ptrace events on new child processes.

[John Baldwin]

New child processes on FreeBSD do not inherit optional ptrace events
such as fork and LWP events from the parent process.  Instead,
explicitly enable events on new children when reporting a fork
event.

gdb/ChangeLog:

	* fbsd-nat.c (fbsd_wait): Use "fbsd_enable_proc_events" on
	new child processes.
---
 gdb/ChangeLog  | 5 +++++
 gdb/fbsd-nat.c | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dcedc14..33cd6a7 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,10 @@
 2016-07-15  John Baldwin  <jhb@FreeBSD.org>
 
+	* fbsd-nat.c (fbsd_wait): Use "fbsd_enable_proc_events" on
+	new child processes.
+
+2016-07-15  John Baldwin  <jhb@FreeBSD.org>
+
 	* fbsd-nat.c (fbsd_enable_lwp_events): Remove function.
 	(fbsd_enable_proc_events): New function.
 	(fbsd_enable_follow_fork): Remove function.
diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index 508ab19..5e4304e 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -836,6 +836,9 @@ fbsd_wait (struct target_ops *ops,
 		  child_ptid = ptid_build (child, pl.pl_lwpid, 0);
 		}
 
+	      /* Enable additional events on the child process.  */
+	      fbsd_enable_proc_events (ptid_get_pid (child_ptid));
+
 	      /* For vfork, the child process will have the P_PPWAIT
 		 flag set.  */
 	      fbsd_fetch_kinfo_proc (child, &kp);
-- 
2.8.4

[PATCH 1/3] Consolidate code to enable optional FreeBSD native target event reporting.

[John Baldwin]

Add a new function to enable optional event reporting for FreeBSD native
targets.  Specifically, use this to enable fork and LWP events.
The bodies of fbsd_enable_follow_fork and fbsd_enable_lwp_events have been
subsumed into the new function.  In addition, use the PT_GET_EVENT_MASK
and PT_EVENT_SET_MASK requests added in FreeBSD 12 when present to enable
these events.

gdb/ChangeLog:

	* fbsd-nat.c (fbsd_enable_lwp_events): Remove function.
	(fbsd_enable_proc_events): New function.
	(fbsd_enable_follow_fork): Remove function.
	(fbsd_post_startup_inferior): Use "fbsd_enable_proc_events".
	(fbsd_post_attach): Likewise.
---
 gdb/ChangeLog  |  8 ++++++++
 gdb/fbsd-nat.c | 59 ++++++++++++++++++++++++++++------------------------------
 2 files changed, 36 insertions(+), 31 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6c187dc..dcedc14 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,13 @@
 2016-07-15  John Baldwin  <jhb@FreeBSD.org>
 
+	* fbsd-nat.c (fbsd_enable_lwp_events): Remove function.
+	(fbsd_enable_proc_events): New function.
+	(fbsd_enable_follow_fork): Remove function.
+	(fbsd_post_startup_inferior): Use "fbsd_enable_proc_events".
+	(fbsd_post_attach): Likewise.
+
+2016-07-15  John Baldwin  <jhb@FreeBSD.org>
+
 	* common/signals.c (gdb_signal_from_host): Handle SIGLIBRT.
 	(do_gdb_signal_to_host): Likewise.
 	* infrun.c (_initialize_infrun): Pass GDB_SIGNAL_LIBRT through to
diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
index fa9516e..508ab19 100644
--- a/gdb/fbsd-nat.c
+++ b/gdb/fbsd-nat.c
@@ -412,22 +412,43 @@ fbsd_thread_name (struct target_ops *self, struct thread_info *thr)
 }
 #endif
 
-#ifdef PT_LWP_EVENTS
-/* Enable LWP events for a specific process.
+/* Enable additional event reporting on new processes.
 
-   To catch LWP events, PT_LWP_EVENTS is set on every traced process.
+   To catch fork events, PTRACE_FORK is set on every traced process
+   to enable stops on returns from fork or vfork.  Note that both the
+   parent and child will always stop, even if system call stops are
+   not enabled.
+
+   To catch LWP events, PTRACE_EVENTS is set on every traced process.
    This enables stops on the birth for new LWPs (excluding the "main" LWP)
    and the death of LWPs (excluding the last LWP in a process).  Note
    that unlike fork events, the LWP that creates a new LWP does not
    report an event.  */
 
 static void
-fbsd_enable_lwp_events (pid_t pid)
+fbsd_enable_proc_events (pid_t pid)
 {
+#ifdef PT_GET_EVENT_MASK
+  int events;
+
+  if (ptrace (PT_GET_EVENT_MASK, pid, (PTRACE_TYPE_ARG3)&events,
+	      sizeof (events)) == -1)
+    perror_with_name (("ptrace"));
+  events |= PTRACE_FORK | PTRACE_LWP;
+  if (ptrace (PT_SET_EVENT_MASK, pid, (PTRACE_TYPE_ARG3)&events,
+	      sizeof (events)) == -1)
+    perror_with_name (("ptrace"));
+#else
+#ifdef TDP_RFPPWAIT
+  if (ptrace (PT_FOLLOW_FORK, pid, (PTRACE_TYPE_ARG3)0, 1) == -1)
+    perror_with_name (("ptrace"));
+#endif
+#ifdef PT_LWP_EVENTS
   if (ptrace (PT_LWP_EVENTS, pid, (PTRACE_TYPE_ARG3)0, 1) == -1)
     perror_with_name (("ptrace"));
-}
 #endif
+#endif
+}
 
 /* Add threads for any new LWPs in a process.
 
@@ -957,20 +978,6 @@ fbsd_remove_vfork_catchpoint (struct target_ops *self, int pid)
 {
   return 0;
 }
-
-/* Enable fork tracing for a specific process.
-   
-   To catch fork events, PT_FOLLOW_FORK is set on every traced process
-   to enable stops on returns from fork or vfork.  Note that both the
-   parent and child will always stop, even if system call stops are
-   not enabled.  */
-
-static void
-fbsd_enable_follow_fork (pid_t pid)
-{
-  if (ptrace (PT_FOLLOW_FORK, pid, (PTRACE_TYPE_ARG3)0, 1) == -1)
-    perror_with_name (("ptrace"));
-}
 #endif
 
 /* Implement the "to_post_startup_inferior" target_ops method.  */
@@ -978,12 +985,7 @@ fbsd_enable_follow_fork (pid_t pid)
 static void
 fbsd_post_startup_inferior (struct target_ops *self, ptid_t pid)
 {
-#ifdef TDP_RFPPWAIT
-  fbsd_enable_follow_fork (ptid_get_pid (pid));
-#endif
-#ifdef PT_LWP_EVENTS
-  fbsd_enable_lwp_events (ptid_get_pid (pid));
-#endif
+  fbsd_enable_proc_events (ptid_get_pid (pid));
 }
 
 /* Implement the "to_post_attach" target_ops method.  */
@@ -991,12 +993,7 @@ fbsd_post_startup_inferior (struct target_ops *self, ptid_t pid)
 static void
 fbsd_post_attach (struct target_ops *self, int pid)
 {
-#ifdef TDP_RFPPWAIT
-  fbsd_enable_follow_fork (pid);
-#endif
-#ifdef PT_LWP_EVENTS
-  fbsd_enable_lwp_events (pid);
-#endif
+  fbsd_enable_proc_events (pid);
   fbsd_add_threads (pid);
 }
 
-- 
2.8.4

Re: [PATCH 0/3] Add "real" vfork done handling on FreeBSD

[Pedro Alves]

On 07/18/2016 03:57 PM, John Baldwin wrote:
> FreeBSD 12 recently gained a real vfork done event via ptrace(2).
> This changes the FreeBSD native targets to use this when it exists
> instead of faking a done event after a sleep.

That was fast...

LGTM.

Thanks,
Pedro Alves