On Mon, 30 Dec 2002 21:03:30 +0100 (MEZ), Ruediger Ihle wrote:
>> Memory objects in this so called linear address
>>space are addressable from any context by means of
>>the DOS32FLATDS selector;
>
>Are you sure ? AFAIK, DOS32FLATDS requires the code to
>run at ring 0. I seem to remember, that I had to move some
>INIT code to INITCOMPLETE in order to use this approach.
I've checked this in detail now: DOS32FLATDS may be used at INIT time
of DEVICEs as well. As a proof, there is a largely modified (i.e.
mostly rewritten) VFDisk.sys (virtual floppy driver) now which no
longer allocates its memory in (contiguous) physical address space
(using AllocPhys) but in linear address space (physically
discontiguous, using VMAlloc). There is no mapping to any GDT selector
anywhere just plain flat addressing. This change not only makes the
driver much easier and more concise, but rather stops it from its
annoying tendency of failing to allocate large chunks of physically
contiguous memory :-)
Ciao,
Dani
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