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Date: Mon, 20 Nov 2006 00:10:16 -0500
From: "Andrew Wilcox" <andrew.r.wilcox@gmail.com>
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Subject: [Qemu-devel] Qemu 0.8.0 and latest CVS - invalid opcode doing ljmp
	to set CS
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To: qemu-devel@nongnu.org

Hello,

My kernel crashes in Qemu with this error:

An exception 06 (Invalid Opcode) with error code 0 has occurred in the
AWOS kernel (0008:0000004C).

the disassembly of the relevant section:
00100039 <gdt_flush>:
  100039:       0f 01 15 60 d0 10 00    lgdtl  0x10d060
  100040:       66 b8 10 00             mov    $0x10,%ax
  100044:       8e d8                   movl   %eax,%ds
  100046:       8e c0                   movl   %eax,%es
  100048:       8e e0                   movl   %eax,%fs
  10004a:       8e e8                   movl   %eax,%gs
  10004c:       ea 53 00 10 00 08 00    ljmp   $0x8,$0x100053
  100053:       c3                      ret

Qemu's disassembly (via log in_asm):
0x00000039:  out    %eax,(%dx)
0x0000003a:  add    %dh,%al
0x0000003c:  push   %ebx
0x0000003d:  incl   (%eax)
0x0000003f:  lock adc %al,0xf84dc000(%ebx)
0x00000046:  add    %dh,%al
0x00000048:  inc    %ecx
0x00000049:  clc
0x0000004a:  add    %dh,%al
0x0000004c:  (bad)
0x0000004d:  jecxz  0x4f

I can boot the kernel on a normal computer, an IBM Aptiva with a
Pentium 166MHz MMX processor, without this error.

Is there a special way to compile the kernel, or maybe something I
missed?  You may look at the source at:
http://awos.sourceforge.net/nightly

The computer I am attempting to run Qemu on:
Mobile Intel(R) Celeron(R) Processor (NetBurst) 1.60GHz
487MB RAM (16MB shared Video RAM)
Ubuntu Dapper Drake 6.06.1 LTS
Linux Lappy 2.6.15-27-386 #1 PREEMPT Sat Sep 16 01:51:59 UTC 2006 i686 GNU/Linux
Tested with 0.8.0, 0.8.2-release and snapshot-2006-11-18.  All exhibit
the same problem.

I did try and Google "Qemu invalid opcode ljmp" and "Qemu invalid
instruction ljmp" and "Qemu #UD ljmp" to no avail.

I also saw this message which seems fairly similar to my problem with
no replies:  http://lists.gnu.org/archive/html/qemu-devel/2006-03/msg00022.html

Thank you for your attention.

Andrew