MirOS Manual: xf86(4)

XF86(4)                    BSD Programmer's Manual                     XF86(4)

NAME

     xf86 - XFree86 aperture driver

SYNOPSIS

     option APERTURE

DESCRIPTION

     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

     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

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

HISTORY

     /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

     The aperture driver was written by Matthieu Herrb.

BUGS

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

MirOS BSD #10-current         February 20, 1998                              1

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