Moves finalise logic out of signal handler (#268)

Signal handler now only sets a flag that is checked in main

firmware/src/sgx/src/untrusted/main.c

@@ -54,6 +54,9 @@ struct arguments {
     char *enclave_path;
 };
 
+// Global flag to indicate that the application should stop
+static sig_atomic_t G_stop_requested = 0;
+
 // Argp individual option parsing function
 static error_t parse_opt(int key, char *arg, struct argp_state *state) {
     struct arguments *arguments = state->input;
@@ -106,7 +109,9 @@ static void finalise_with(int exit_code) {
 static void finalise(int signum) {
     (void)signum; // Suppress unused parameter warning
 
-    finalise_with(0);
+    // Note: Do not add any finalise logic directly here, just set the flag
+    // and let the main loop handle it
+    G_stop_requested = 1;
 }
 
 static void set_signal_handlers() {
@@ -157,16 +162,22 @@ int main(int argc, char **argv) {
     unsigned int tx = 0;
 
     while (true) {
+        if (G_stop_requested) {
+            break;
+        }
+
         rx = io_exchange(tx);
 
         if (rx) {
             tx = eprx_system_process_apdu(rx);
         }
     }
 
-    LOG("Exited main loop unexpectedly\n");
+    finalise_with(0);
+    return 0;
 
 main_error:
+    LOG("Exited main loop unexpectedly\n");
     finalise_with(1);
     return 1;
 }