/proc/<pid>/maps

[cpg aladdin de]

I've got a question:

If I look at /proc/<pid>/maps I've got 3 entries for every shared lib
the process uses. On i386 there are only 2 entries for each shlib
(I assume code + data).
The additional entry on alpha has flags "---p" (no read, no write  no
execute,
I don't know what p means).

What is the purpose of this mapping and where does it come from?

regards,
chris