Message-ID: <3294F710.32E6@skygames.com>
Date: Thu, 21 Nov 1996 16:42:56 -0800
From: Kevin Baca <kbaca AT skygames DOT com>
Organization: BlueSky Software
MIME-Version: 1.0
To: djgpp AT delorie DOT com
Subject: Re: pentium RDMSR instruction
References: <571ku3$gf1 AT news2 DOT noc DOT netcom DOT net>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

mcarter@@delorie.com wrote:
> 
> I've got the new DJGPP binaries 2.7 for v2.1 and the assembler now recognizes
> Pentium instructions - great!  RDTSC works fine but RDMSR does not.  It gets
> encoded as 0x0F,0x32 which is right but I get the following error when it is run:
> 
> >Exiting due to signal SIGILL
> >Invalid Opcode at eip=00001581
> >eax=d2504e7b ebx=0004e080 ecx=00000011 edx=00000dcf esi=00000054 edi=0000c4d0
> >ebp=0004c4a4 esp=0004c488 program=C:\UTILS\GNU\A.EXE
> >cs: sel=00d7  base=00400000  limit=0005ffff
> >ds: sel=00df  base=00400000  limit=0005ffff
> >es: sel=00df  base=00400000  limit=0005ffff
> >fs: sel=00b7  base=0001dfe0  limit=0000ffff
> >gs: sel=00ef  base=00000000  limit=ffffffff
> >ss: sel=00df  base=00400000  limit=0005ffff
> >
> >Call frame traceback EIPs:
> >  0x00001581
> >  0x00001b2e
> 
> Anyone else get this problem?  Should I have posted this to an assembly
> news group?

I gave the wrong answer on this same question today.  I suggested using
__asm__ __volatile__ instead of just plain __asm__.

The real problem (I think) is that these instructions are priveleged
instructions and therefore can only be executed from a ring 0 process
(e.g. kernel code).

You need a DPMI host that allows your program to run in ring 0.  I'm not
sure if Windows does this.  I know CWSDPMI does not.  But CWSDPR0 does. 
You should be able to get CWSDPRO.EXE from the same place you got
CWSDPMI.EXE (I think).

-Kevin