NAME    [Toc]    [Back]

     xf86 - XFree86 aperture driver

SYNOPSIS    [Toc]    [Back]

     option APERTURE

DESCRIPTION    [Toc]    [Back]

     On  alpha,  amd64,  cats,  i386,  macppc,  and  sparc64  the
/dev/xf86 driver
     provides  access  to the memory and I/O ports of a VGA board
and to the PCI
     configuration registers for use by  the  XFree86  X  servers
when running
     with a kernel security level > 0.

     The X servers require the use of this driver.

ACCESS CONTROL    [Toc]    [Back]

     Access  to  the  /dev/xf86 device is allowed when the sysctl
variable
     machdep.allowaperture >= 1.  This variable (which has a  default value of
     0)  can only be manipulated when the security level is <= 0,
so it should
     be set in /etc/sysctl.conf.  The possible values for
     machdep.allowaperture are:

     0       the aperture driver is disabled.  Opening it returns
EPERM.

     1        the  aperture  driver allows access to standard VGA
framebuffer and
             BIOS.  Access to pci(4) configuration  registers  is
also allowed.

     2        in addition to allowing access to pci(4) configuration registers,
             the aperture driver allows access to the  whole  1st
megabyte of
             physical  memory, permitting use of the int10 emulation in XFree86
             4.0.x.  Note that this can cause some security problems, since
             the  process  that has access to the aperture driver
can also access
 part of the kernel memory.  This  mode  is  not
supported on
             alpha or sparc64.

SEE ALSO    [Toc]    [Back]

     XF86_Accel(1),     XF86_SVGA(1),     options(4),     pci(4),
sysctl.conf(5),
     config(8), sysctl(8)

HISTORY    [Toc]    [Back]

     /dev/xf86 was introduced as a  loadable  kernel  module  for
NetBSD 0.9c with
     XFree86  3.1.   It  was integrated as an in-kernel device on
OpenBSD 2.3.
     It is required in order to allow access to I/O ports for all
X servers
     since OpenBSD 2.4.

AUTHORS    [Toc]    [Back]

     The aperture driver was written by Matthieu Herrb.

BUGS    [Toc]    [Back]

     This  driver  allows  access to all addresses above physmem.
It should be
     restricted to the actual address range of the video  memory.

OpenBSD      3.6                        February     20,     1998