Fiasco.OC x86 IO port permission bitmap

Daniel Waddington d.waddington at
Tue Jan 24 00:54:29 CET 2012


I want to use the TSS I/O permission bit map to support fine grained 
control of I/O access for user-level apps (x86 32 bit target).  From 
looking at the kernel code, I believe the bit map is switched out 
per-process as part of the Context class (Space::_io_space) - correct me 
if I am wrong.  My query is how to set/clear the bits for a given target 
task from a "root" task with sufficient privileges (e.g., base caps and 
sigma0 caps).  I could extend the kernel scheduler protocol, but I don't 
want to do this if there is already a clean way in place.

Daniel Waddington

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