From: "H. Peter Anvin" <hpa@zytor.com>
To: linux-kernel@vger.kernel.org
Subject: Re: ioperm() / iopl() irritation
Date: 28 Feb 2002 15:53:27 -0800 [thread overview]
Message-ID: <a5mftn$jim$1@cesium.transmeta.com> (raw)
In-Reply-To: <Pine.LNX.4.33.0202282128170.25655-100000@biker.pdb.fsc.net>
Followup to: <Pine.LNX.4.33.0202282128170.25655-100000@biker.pdb.fsc.net>
By author: Martin Wilck <Martin.Wilck@fujitsu-siemens.com>
In newsgroup: linux.dev.kernel
>
> A short question that may be dumb:
>
> In the docs on i386 IO protection that I know, it is said that
> the processor ANDs the two protection mechanisms offered by the
> IOPL flag and the io permission bitmap. That is, if IO permissions
> are granted through iopl(), but ports are masked in the IO permission
> bitmap, a segmentation fault should arise.
>
Wrong.
> Such a situation should be generated by code like this:
>
> iopl(3);
> ioperm (0,0x1f,1); /* 0x20-0x3ff remain masked */
> c = inb (0x20);
>
> However on my machine this codse is successful! How is that possible?
Because you have misunderstood how IOPL works.
-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
next prev parent reply other threads:[~2002-02-28 23:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-28 20:34 ioperm() / iopl() irritation Martin Wilck
2002-02-28 23:53 ` H. Peter Anvin [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-03-01 10:45 Martin Wilck
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