From: Marc-Christian Petersen <m.c.p@wolk-project.de>

2.4 patch from Adrian Bunk.

ERRORS

    The mprotect() function shall fail if:

    ...

    [ENOMEM]
        Addresses in the range [addr,addr+len) are invalid for the
        address space of a process, or specify one or more pages which are
        not mapped.