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> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Feb 28 2002 - 21:00:46 EST