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Clarify that vm_map_protect cannot upgrade max_protection
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Authored by emaste on Jun 20 2019, 1:01 PM.

Details

Summary

It's implied by the RETURN VALUES section but be explicit in the description that vm_map_protect can not set new protection bits that are already in each entry's max_protection.

(Prompted by a comment/review in D18880.)

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Event Timeline

emaste created this revision.Jun 20 2019, 1:01 PM
brooks accepted this revision.Jun 20 2019, 6:04 PM
brooks added inline comments.
share/man/man9/vm_map_protect.9
66

It is probably noting that this case also (IIRC) demotes any existing permissions (vs bailing if they would not be permitted).

This revision is now accepted and ready to land.Jun 20 2019, 6:04 PM
brooks added inline comments.Jun 20 2019, 6:04 PM
share/man/man9/vm_map_protect.9
66

*worth noting

This revision was automatically updated to reflect the committed changes.
emaste added inline comments.Jun 20 2019, 6:20 PM
share/man/man9/vm_map_protect.9
66

Yeah - I'll confirm and commit another change.

emaste added inline comments.Jun 20 2019, 6:23 PM
share/man/man9/vm_map_protect.9
66

yes,

old_prot = current->protection;

if (set_max)
        current->protection =
            (current->max_protection = new_prot) &
            old_prot;
else
        current->protection = new_prot;