The strong requirement would be that the cookie is not a bit longer than
sizeof(unsigned long).
For the "equality" check, this better be "==", although it could be
abstracted in a function/macro that SeLinux implements in a different way.
But this "equality" check is done a page-fault time, so it better be
pretty quick (otherwise if they bloat that path, they probably be better
of not using MAP_NOZERO at all).
- Davide
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