Date: Wed, 5 May 1999 10:01:55 +0100 (BST) From: Doug Rabson <dfr@nlsystems.com> To: CyberPsychotic <fygrave@tigerteam.net> Cc: freebsd-hackers@freebsd.org, tech@openbsd.org Subject: Re: io ports reading/writing Message-ID: <Pine.BSF.4.05.9905051001000.411-100000@herring.nlsystems.com> In-Reply-To: <Pine.GSO.4.05.9905051339310.632-100000@kyrnet.kg>
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On Wed, 5 May 1999, CyberPsychotic wrote:
> ~
> ~ I think you just open /dev/io and use inb/outb. Be warned that this will
> ~ only work on i386 - the alpha uses a library, libio, to emulate inb/outb
> ~ in user programs.
>
> you say that on i386,
> open("/dev/io",O_RDWR); foo=inb(PORT_X); bar=outb(foo,PORT_Y); would work?
> if so, in this scheme I don't quite understand how kernel would handle the
> access to io ports. F.e. assuming that opening /dev/io, would give
> permittions to all io ports would be quite dangerous (since not all programs
> which could be permitted to modify cmos, should be permitted to ports
> controlling disk access etc).
>
> would you mind eleborating this abit?
>
The access control for io ports is controlled by the file-system
permissions on /dev/io. In a standard setup, only root can access this
device.
--
Doug Rabson Mail: dfr@nlsystems.com
Nonlinear Systems Ltd. Phone: +44 181 442 9037
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