efi_loader: Clean up system table on exit

We put the system table into our runtime services data section so that
payloads may still access it after exit_boot_services. However, most fields
in it are quite useless once we're in that state, so let's just patch them
out.

With this patch we don't get spurious warnings when running EFI binaries
anymore.
Signed-off-by: NAlexander Graf <agraf@suse.de>

lib/efi_loader/efi_runtime.c

@@ -125,6 +125,22 @@ static const struct efi_runtime_detach_list_struct efi_runtime_detach_list[] = {
 		/* RTC accessors are gone */
 		.ptr = &efi_runtime_services.get_time,
 		.patchto = &efi_device_error,
+	}, {
+		/* Clean up system table */
+		.ptr = &systab.con_in,
+		.patchto = NULL,
+	}, {
+		/* Clean up system table */
+		.ptr = &systab.con_out,
+		.patchto = NULL,
+	}, {
+		/* Clean up system table */
+		.ptr = &systab.std_err,
+		.patchto = NULL,
+	}, {
+		/* Clean up system table */
+		.ptr = &systab.boottime,
+		.patchto = NULL,
 	},
 };