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Confused with TSS structure

Posted: Fri Mar 26, 2010 9:03 pm
by shindow
hello everyone!
I am confused with the the I/O map base address field in TSS
from the intel paper:
I/O map base address field
Contains a 16-bit offset from the base of the TSS to the I/O permission bit map
and interrupt redirection bitmap.
I cann't get more detailed information about it.

my Question is that
1. how to set the interrupt redirection bitmap.I was using vm86 that have to set it.
2.could anyone explain it more detailed about this filed .

Thank you in advance! :D

Re: Confused with TSS structure

Posted: Sat Mar 27, 2010 4:13 am
by thepowersgang
To include a TSS port bitmap you need to allocate space for it in your TSS segment (by increasing the limit field in the GDT/LDT and adding space to the TSS buffer) and then set the I/O permission map field to the offset from the beginning of the TSS to the bitmap.
Usually this bitmap will be immediately after the TSS, but the field exists to allow you to have multiple bitmaps in the same TSS and quickly switch between them.

Re: Confused with TSS structure

Posted: Sat Mar 27, 2010 12:35 pm
by Gigasoft
The interrupt redirection bitmap is located at the offset of the I/O permission bitmap minus 32.