Do traditional Ocall if g_uswitchless_handle is uninitialized

Global object initialization (init_global_object) happens before
g_uswitchless_handle is initialized (via sl_init_switchless).
Some ctors invoke syscalls via switchless ocalls. This causes
init_tswitchless_ocall_mngr to be invoked with sl_call_once
prematurely, returning -1. Subsequent invokations will always return -1, such
that switchless ocalls never happen. A simple solution is to fallback
to traditional ocalls until g_uswitchless_handle has been
initialized.

Author: henrywang8atfbdotcom

sdk/switchless/sgx_tswitchless/sgx_ocall_switchless.c

@@ -89,6 +89,17 @@ sgx_status_t sgx_ocall_switchless(const unsigned int index, void* ms)
     if (sgx_is_enclave_crashed())
         return SGX_ERROR_ENCLAVE_CRASHED;
 
+    /* Global object initialization (init_global_object) happens before
+     * g_uswitchless_handle is initialized (via sl_init_switchless).
+     * Some ctors invoke syscalls via switchless ocalls. This causes
+     * init_tswitchless_ocall_mngr to be invoked with sl_call_once prematurely,
+     * returning -1. Subsequent invokations will always return -1, such that
+     * switchless ocalls never happen. A simple solution is to fallback to
+     * traditional ocalls until g_uswitchless_handle has been initialized. */
+    if (g_uswitchless_handle == NULL) {
+      return sgx_ocall(index, ms);
+    }
+
     /* If Switchless SGX is not enabled at enclave creation, then switchless OCalls
      * fallback to the traditional OCalls */
     if (sl_call_once(&g_init_ocall_mngr_done, init_tswitchless_ocall_mngr, NULL))