Index: kernel/generic/include/syscall/copy.h
===================================================================
--- kernel/generic/include/syscall/copy.h	(revision b7fd2a02e4161f4edd38548e7f8456b8021549be)
+++ kernel/generic/include/syscall/copy.h	(revision 86b70c6fa1a6e0fc138e6294cb6cfe8bda4535d3)
@@ -49,7 +49,8 @@
 /*
  * This interface must be implemented by each architecture.
+ * The functions return zero on failure and nonzero on success.
  */
-extern errno_t memcpy_from_uspace(void *dst, const void *uspace_src, size_t size);
-extern errno_t memcpy_to_uspace(void *uspace_dst, const void *src, size_t size);
+extern uintptr_t memcpy_from_uspace(void *dst, const void *uspace_src, size_t size);
+extern uintptr_t memcpy_to_uspace(void *uspace_dst, const void *src, size_t size);
 
 #endif