Several macros/functions from asm/uaccess.h (powerpc) are not seen by Elixir

[chleroy]

For instance, there's two definitions for __get_user_asm_goto() in a #if/#else
The second definition is not seen by Elixir.

Also problem with allow_read_from_user() and similar helpers, Elixir sees its definition in asm/kup.h as a reference and see no definition for that function.

Same for allow_user_access(), definitions are seen as references