Change the parameters of start

On the switch, `start` takes two parameters : an exception pointer,
and a handle to the main thread. For libtransistor, we'll also add
a third one: a context handle. This should allow ace_loader to start
apps expecting the usual switch treatment, while still providing the
context to libtransistor binaries.

nro.c

@@ -26,7 +26,7 @@ static char *nro_argoffs;
 
 uint64_t nro_start()
 {
-	uint64_t (*entry)(libtransistor_context_t*) = nro_base + 0x80;
+	uint64_t (*entry)(void*, thread_h, libtransistor_context_t*) = nro_base + 0x80;
 	uint64_t ret;
 
 	// generate memory block
@@ -68,8 +68,14 @@ uint64_t nro_start()
 	void *tls_backup = *tls_userspace_pointer;
 	*(void**)(get_tls() + 0x1f8) = NULL;
 
+	thread_h main_handle = 0;
+	if (svcGetThreadId(&main_handle, CURRENT_THREAD) != RESULT_OK) {
+		printf("- failed to acquire handle to main thread\n");
+		return -1;
+	}
+
 	// run NRO
-	ret = entry(&loader_context);
+	ret = entry(NULL, main_handle, &loader_context);
 
 	// Restore TLS
 	*tls_userspace_pointer = tls_backup;