dosemu crashes if $_dosmem setting in dosemu.conf is changed

[James Paige]

Binary package hint: dosemu

Description: Ubuntu 8.04.1
Release: 8.04
Package version: dosemu 1.4.0+svn.1828-1

Dosemu has an option that controls available real-mode memory. Edit /etc/dosemu/dosemu.conf and you will find:

# $_dosmem = (640)

Uncomment this line, and slightly increase the number. 768 is the highest valid value, but 641 is sufficient to trigger this crash.

Run dosemu (in console mode from a terminal, NOT the graphical X mode), and it will crash immediately with no error message.

This error does not occur when I downgrade to the older 1.2.2-9 packages. In my own configuration I use $_dosmem = (704) and it works perfectly in the older version.

I have already worked around the LOWRAM mmap segmentation fault reported in bug 216398

[Pablo Castellano (pablocastellano)]

Hello!
I have followed your steps but I can't reproduce it under Intrepid and dosemu version 1.4.0+svn.1828-2ubuntu1.
Since Intrepid is now stable, could you try it using the latest version?

This is what I get:
:~$ dosemu
ERROR: $_dosmem = (641) not allowed for X and VGA console graphics, restricting to 640K

And it doesn't crash.
Good bye!

[James Paige (jamesp-westcoastaerospace)]

Oh! I should have clarified. I am not using the X windows mode of dosemu, I am running it in a text mode terminal. When you run in a terminal, it is not supposed to allocate the VGA graphics areas (leaving them available for $_dosmem)

That is consistent with the behavior of real DOS. If you boot with a monochrome card (no VGA) you have access to more memory, or if you used the correct emm386 options you could disable your VGA card's graphics modes and get access to that memory.

[Pablo Castellano (pablocastellano)]

:) Okay now I can confirm it.

My output is:
DOSEMU 1.4.0.0 [...]
[...]
GNU General Public License [...]
ERROR: general protection at 0x31c9f: 0