From: clc5q AT cobra DOT cs DOT Virginia DOT EDU (Clark L. Coleman)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Inline Assembler/CWSDPR0 (Privileged instructions)
Date: 18 Mar 1999 19:29:40 GMT
Organization: University of Virginia
Lines: 45
Message-ID: <7crk74$5jl$1@murdoch.acc.Virginia.EDU>
References: <7copjd$mp6$1 AT murdoch DOT acc DOT Virginia DOT EDU> <36f02ea0 DOT sandmann AT clio DOT rice DOT edu>
NNTP-Posting-Host: cobra.cs.virginia.edu
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

In article <36f02ea0 DOT sandmann AT clio DOT rice DOT edu>,
Charles Sandmann <sandmann AT clio DOT rice DOT edu> wrote:
>> I followed those instructions (turned off DPMI in my AUTOEXEC.BAT,
>> rebooted, compiled/linked, did the stubedit). However, as I step
>> through the code in the debugger (gdb), I see that as soon as I step
>> over the WRMSR instruction, I get a SIGSEGV exception and cannot
>> continue. I will show the code below.
>
>You aren't executing the ring 0 if you have the debugger loaded!  It
>loads the regular version, which must be used for the child.  Run
>the image standalone - and if it dies write down the registers.  If the 
>low bits on the selectors are "3" you aren't running a ring 0 DPMI.
>If they are 0 check the line number/EIP for the real error.  You can't
>really debug in ring 0.

OK, I recompiled without -g and ran the EXE without gdb. Same
story. Here is the register dump info:

Exiting due to signal SIGSEGV
Page fault at eip=00002585, error = 0002
eax=00000011 ebx=00000000 ecx=00000011 edx=00000000
esi=00000054 edi=0c040843 ebp=0108fc68 esp=0108fc68

cs: sel=00a4  base=10000000  limit=0109ffff
ds: sel=00ac  base=10000000  limit=0109ffff
es: sel=00ac  base=10000000  limit=0109ffff
fs: sel=008c  base=00030280  limit=0000ffff
gs: sel=00bc  base=00000000  limit=0010ffff
ss: sel=00ac  base=10000000  limit=0109ffff

App stack: [0108fd18..0100fd18]
Excepn stack: [0100fc00..0100dcc0]

Call frame traceback EIPs:
0x00002585
0x00001833
0x000016a9
0x00003532

That's it. Someone asked for a "symify of the traceback" and I have no
idea what that means.

Any help is very much appreciated.

Clark Coleman