Make /home /tmp noexec nodev without a separate patition

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http://serverfault.com – I need to change some mount options for parts of the root filesystem, such as /tmp /var and /home (add nodev,nosuid and quota), but I haven't ability to make a separate partition and I have not enough RAM to mount /tmp as tmpfs. I've tried mount -o bind,noexec,nodev,nosuid /tmp /tmp, but it seems not working because after that I still can exec files from /tmp and make device nods on it. Is there other way to do that? (HowTos)