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SubjectRe: I/O permissions for V86 tasks?
Date
On 	Wed, 15 Jul 1998 11:03:32 -0800, Kendall Bennett said:
> Actually I have tried compiled the 2.0.35 kernel sources with an 8Kb
> I/O bitmap (I just grabbed the latest 2.1 sources so we will start
> hacking on this), and it did not work.

Forgive me if you've already done this but you also need to modify the
macro which sets TSS descriptors. In 2.0.33 this is the set_tss_desc
macro in asm/system.h. In my experimental VBE driver I have the following:

/* The following hack allows the IO_BITMAP to be a nonstandard size */
#undef set_tss_desc /* asm/system.h */
#define _set_tss_desc(n,addr,sz) _set_tssldt_desc(((char *) (n)),((int)(addr)),107+sz*4,"0x89")
#define set_tss_desc(n,addr) _set_tss_desc(n,addr,IO_BITMAP_SIZE)

I have attempted to allow the bitmap to be extended just for the V86 task
but I don't know whether it works as I haven't tested it since my video
card just uses the normal VGA I/O ports.

And by the way, the answer to your previous question about IOPL is no,
the Intel processor does not allow the V86 task to take notice of any IOPL
so you are forced to do it via the bitmap.

imc


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