[PATCH xserver] xwayland: Restore default signal handlers

[Olivier Fourdan]

Xwayland is a pretty standard Wayland client, we want to be able to
capture core dumps on crashes.

Yet using "-core" in the command line is not what we want, because that
causes any FatalError() to generate a core dump, meaning that we would
get a core file for all Wayland server crashes, which would generate a
lot of false positives.

Besides, for most case, the xorg_backtrace() generated is not sufficient
and rather ineffective compared to a regular debugger session.

Restore the default signal handlers for Xwayland so that the usual
signals (SIGSEGV, SIGABRT, SIGILL, etc.) will possibly generate a core
file (depending on the OS configuration of course).

See also: https://bugzilla.gnome.org/show_bug.cgi?id=790502
     and: https://bugzilla.gnome.org/show_bug.cgi?id=789086

Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
---
 hw/xwayland/xwayland.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/hw/xwayland/xwayland.c b/hw/xwayland/xwayland.c
index 81e669cae..f327db748 100644
--- a/hw/xwayland/xwayland.c
+++ b/hw/xwayland/xwayland.c
@@ -845,6 +845,22 @@ wm_selection_callback(CallbackListPtr *p, void *data, void *arg)
     DeleteCallback(&SelectionCallback, wm_selection_callback, xwl_screen);
 }
 
+static void
+reset_default_signals (void)
+{
+    OsSignal(SIGSEGV, SIG_DFL);
+    OsSignal(SIGABRT, SIG_DFL);
+    OsSignal(SIGILL, SIG_DFL);
+#ifdef SIGEMT
+    OsSignal(SIGEMT, SIG_DFL);
+#endif
+    OsSignal(SIGFPE, SIG_DFL);
+    OsSignal(SIGBUS, SIG_DFL);
+    OsSignal(SIGSYS, SIG_DFL);
+    OsSignal(SIGXCPU, SIG_DFL);
+    OsSignal(SIGXFSZ, SIG_DFL);
+}
+
 static Bool
 xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
 {
@@ -853,6 +869,9 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
     Pixel red_mask, blue_mask, green_mask;
     int ret, bpc, green_bpc, i;
 
+    /* For Xwayland, we want to be able to capture core files on crashes */
+    reset_default_signals();
+
     xwl_screen = calloc(1, sizeof *xwl_screen);
     if (xwl_screen == NULL)
         return FALSE;
-- 
2.14.3