Refactor ptrace extended event status.

This commit implements functions for identifying and extracting extended
ptrace event information from a Linux wait status.  These are just
convenience functions intended to hide the ">> 16" used to extract the
event from the wait status word, replacing the hard-coded shift with a more
descriptive function call.  This is preparatory work for implementation of
follow-fork and detach-on-fork for extended-remote linux targets.

gdb/ChangeLog:

	* linux-nat.c (linux_handle_extended_wait): Call
	linux_ptrace_get_extended_event.
	(wait_lwp): Call linux_is_extended_waitstatus.
	(linux_nat_filter_event): Call linux_ptrace_get_extended_event
	and linux_is_extended_waitstatus.
	* nat/linux-ptrace.c (linux_test_for_tracefork): Call
	linux_ptrace_get_extended_event.
	(linux_ptrace_get_extended_event): New function.
	(linux_is_extended_waitstatus): New function.
	* nat/linux-ptrace.h (linux_ptrace_get_extended_event)
	(linux_is_extended_waitstatus): New declarations.

gdb/gdbserver/ChangeLog:

	* linux-low.c (handle_extended_wait): Call
	linux_ptrace_get_extended_event.
	(get_stop_pc, get_detach_signal, linux_low_filter_event): Call
	linux_is_extended_waitstatus.

---

1 files changed, 17 insertions, 1 deletions

diff --git a/gdb/nat/linux-ptrace.c b/gdb/nat/linux-ptrace.c
index 6275516..8bc3f16 100644
--- a/gdb/nat/linux-ptrace.c
+++ b/gdb/nat/linux-ptrace.c
@@ -416,7 +416,7 @@ linux_test_for_tracefork (int child_pid)
 
   /* Check if we received a fork event notification.  */
   if (ret == child_pid && WIFSTOPPED (status)
-      && status >> 16 == PTRACE_EVENT_FORK)
+      && linux_ptrace_get_extended_event (status) == PTRACE_EVENT_FORK)
     {
       /* We did receive a fork event notification.  Make sure its PID
 	 is reported.  */
@@ -550,3 +550,19 @@ linux_ptrace_set_additional_flags (int flags)
 {
   additional_flags = flags;
 }
+
+/* Extract extended ptrace event from wait status.  */
+
+int
+linux_ptrace_get_extended_event (int wstat)
+{
+  return (wstat >> 16);
+}
+
+/* Determine whether wait status denotes an extended event.  */
+
+int
+linux_is_extended_waitstatus (int wstat)
+{
+  return (linux_ptrace_get_extended_event (wstat) != 0);
+}