A question that has been presented to us is that of direct mmap() access to
AGP bridge-viewed RAM. For our AGP/GART device, the client non-root
processes that are coordinated by the X server are handed a "magic cookie"
that can be used to "bless" a device file descriptor (allowed inside the
kernel) ... and thus allow any mmap as needed directly from the AGP/GART
device. In general, then, only smart and X-server coordinated processes are
then able to do this, enhancing stability, but decreasing unneeded
centralization.
Are there any plans to allow "handing over" priviledges to clients, from one
process to another? Should a technique of "trusted-cookies" be used to
allow non-root clients access to important devices? This technique is easy,
sensibly secure (at least, the first priviledges is granted properly) and
takes little code.
-- CH
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