Subject: RE: pgd_offset

From: "Chagas, Jason" <[email-masked]>
Date: Fri, 20 Aug 1999 10:11:25 -0700

That makes sense...

Thanks,

Jason

		-----Original Message-----
		From:	Dr. David Gilbert [mailto:[email-masked]]
		Sent:	Friday, August 20, 1999 11:40 AM
		To:	Chagas, Jason
		Subject:	RE: pgd_offset

		On Fri, 20 Aug 1999, Chagas, Jason wrote:

		> Kong,
		> 
		> That's right, 'pgd' is a pointer to the translation table
(TB) and 'address'
		> contains the virtual address being mapped. Shifting the
virtual address
		> [right] by 18 (the most significant 11 bits - 31-20) yield
the address of
		> first-level descriptor in the translation table with the
first two least
		> significant bits (1-0) set to zero. Oddly enough, the
function below is
		> shifts by 20. I just wondering if anyone could explain it
to me...

		I wonder if it is something like the fact that this is
shifting bits 1-0
		off the bottom and then I wonder if the pointer its
modifying is actually
		a word pointer and thus each value causes a 4 byte offset in
the language
		- the effect being to do the clear of bits 1-0 for you.

		Dave
	
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