typedef unsigned short __kernel_ipc_pid_t;
typedef unsigned short __kernel_uid_t;
typedef unsigned short __kernel_gid_t;
-#if CONFIG_IS_ENABLED(X86_64)
+/* checking against __x86_64__ covers both 64-bit EFI stub and 64-bit U-Boot */
+#if defined(__x86_64__)
typedef unsigned long __kernel_size_t;
typedef long __kernel_ssize_t;
#else