Re: sysutils/vbetools not working anymore

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Mon, Dec 20, 2010 at 11:58:34PM +0100, Dennis den Brok wrote:
> Hello,
> 
> on 5.99.41/i386, every vbetool command fails with
> 
> mmap /dev/mem: Permission denied
> 
> The exact place seems to be where it tries to mmap 0x0-0x502. I'd
> be thankful for suggestions how to fix this.

Mapping of NULL was explicitly disable by default on platforms with
shared kernel / userland address space.  This makes it harder to exploit
NULL function pointer dereferences in the kernel as shown a few years
ago during the CCC congress for OpenBSD.  There is a sysctl or kernel
option to reenable it, but I forgot the name.

Joerg