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From: Martin Stromberg <Martin DOT Stromberg AT epl DOT ericsson DOT se>
Message-Id: <200303130749.IAA25231@lws256.lu.erisoft.se>
Subject: Re: Getting CRx registers
To: djgpp-workers AT delorie DOT com
Date: Thu, 13 Mar 2003 08:49:46 +0100 (MET)
In-Reply-To: <09e801c2e8ac$6685f830$0600000a@broadpark.no> from "Gisle Vanem" at Mar 12, 2003 04:31:06 PM
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> Is there a safe way to get the value of the Control Registers
> (CR0-4) under CPL > 0?. Under Win-XP "movl %cr4,%eax" seems 
> to be safe (i.e. doesn't crash), but return value is always 0. Under
> plain DOS and CWSDMI it crashes.

Not for CR1-CR4. For CR0 you can SMSW to get the lower 16 bits. And,
IIRC, DB 66; SMSW to get all! (Undocumented so perhaps it won't work
on all CPUs. Unsure if it should be 66 or 67.) I have a little test
program for this somewhere if anybody is interested.


Right,

						MartinS