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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: ioperm call on FreeBSD?
Date: 1 Jan 1996 12:02:00 GMT
Organization: Private BSD site, Dresden
Lines: 42
Message-ID: <4c8ifo$30e@uriah.heep.sax.de>
References: <DKEMoG.C19@midway.uchicago.edu> <4c49he$f8v@uriah.heep.sax.de> <4c4hcm$ur@prds-grn.demon.co.uk>
Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch)
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t.d.g.sandford@prds-grn.demon.co.uk (Thomas D.G. Sandford) writes:
> Is there any documentation on how to use /dev/io ? - I can't find a man
> page anywhere.
IO(4) UNIX Programmer's Manual IO(4)
NAME
io - I/O privilege file
DESCRIPTION
The special file /dev/io is a controlled security hole that allows a pro-
cess to gain I/O privileges (which are normally reserved for kernel-
internal code). Any process that holds a file descriptor on /dev/io open
will get its IOPL bits in the flag register set, thus allowing it to per-
form direct I/O operations. This can be useful in order to write user-
land programs that handle some hardware directly.
The entire access control is handled by the file access permissions of
/dev/io, so care should be taken in granting rights for this device.
Note that even read/only access will grant the full I/O privileges.
FILES
/dev/io
SEE ALSO
mem(4)
HISTORY
The io file appeared in FreeBSD 1.0.
BSD Experimental Jan 1, 1996 1
(Just commited. :-)
--
cheers, J"org
joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)