X Window System aperture driver
On the alpha, amd64, i386, macppc, and sparc64 architectures, the
driver provides access to the
memory and I/O ports of a VGA board and to the PCI configuration registers for
use by the X servers when running with a kernel security level greater than 0.
The X servers require the use of this driver for
video cards on
Access to the /dev/xf86
device is allowed
when the sysctl(8)
than or equal to 1. This variable (which has a default value of 0) can only be
raised when the security level is less than or equal to 0, so it should be set
. The possible values
- the aperture driver is disabled. Opening it returns
- the aperture driver allows access to standard VGA framebuffer and BIOS.
Access to pci(4)
configuration registers is also allowed.
- in addition to allowing access to
configuration registers, the aperture driver allows access to the whole
first megabyte of physical memory, permitting use of the int10 emulation
in X.Org 6.8 and later. 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
- the aperture driver allows multiple processes to concurrently access
configuration registers and the whole first megabyte of physical
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
The aperture driver was written by Matthieu
This driver allows access to all addresses above
. It should be restricted to the
actual address range of the video memory.