[PATCH:xserver] OsSigHandler should not show rtld errors for unrelated signals

[Alan Coopersmith]

If RTLD_DI_SETSIGNAL is set to let us turn runtime linker/loader errors
into catchable signals, then we should only show the errors when catching
that signal, instead of tossing out red herrings to distract people with
unrelated crashes long after their last failed symbol lookup (especially
when using drivers built to support multiple API's by checking which
symbols are available before calling them).

Signed-off-by: Alan Coopersmith <alan.coopersmith at oracle.com>
---
 os/osinit.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/os/osinit.c b/os/osinit.c
index 47061bb..5b2f6b5 100644
--- a/os/osinit.c
+++ b/os/osinit.c
@@ -114,10 +114,14 @@ OsSigHandler(int signo)
 #endif
 {
 #ifdef RTLD_DI_SETSIGNAL
-    const char *dlerr = dlerror();
+# define SIGNAL_FOR_RTLD_ERROR SIGQUIT
+    if (signo == SIGNAL_FOR_RTLD_ERROR) {
+        const char *dlerr = dlerror();
 
-    if (dlerr) {
-        LogMessageVerbSigSafe(X_ERROR, 1, "Dynamic loader error: %s\n", dlerr);
+        if (dlerr) {
+            LogMessageVerbSigSafe(X_ERROR, 1,
+                                  "Dynamic loader error: %s\n", dlerr);
+        }
     }
 #endif                          /* RTLD_DI_SETSIGNAL */
 
@@ -217,7 +221,7 @@ OsInit(void)
          * after ourselves.
          */
         {
-            int failure_signal = SIGQUIT;
+            int failure_signal = SIGNAL_FOR_RTLD_ERROR;
 
             dlinfo(RTLD_SELF, RTLD_DI_SETSIGNAL, &failure_signal);
         }
-- 
2.7.4