8255741: Zero: print signal name in unhandled signal handler

Reviewed-by: stuefe

Author: shipilev

src/hotspot/os_cpu/linux_zero/os_linux_zero.cpp

@@ -240,9 +240,16 @@ JVM_handle_linux_signal(int sig,
   }
 #endif // !PRODUCT
 
-  char buf[64];
-
-  sprintf(buf, "caught unhandled signal %d", sig);
+  char buf[128];
+  char exc_buf[32];
+
+  if (os::exception_name(sig, exc_buf, sizeof(exc_buf))) {
+    bool sent_by_kill = (info != NULL && os::signal_sent_by_kill(info));
+    snprintf(buf, sizeof(buf), "caught unhandled signal: %s %s",
+             exc_buf, sent_by_kill ? "(sent by kill)" : "");
+  } else {
+    snprintf(buf, sizeof(buf), "caught unhandled signal: %d", sig);
+  }
 
 // Silence -Wformat-security warning for fatal()
 PRAGMA_DIAG_PUSH