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Re: a small C program to test xdm's /dev/mem reading on your architecture

HP rx4610 (4x Itanium), Debian unstable, 2.4.18-itanium-smp
Works without problems

HP i2000 (Itanium), Debian unstable, 2.4.18-itanium
Machine hangs after read #40; works with "fragile"

DEC UDB (Alpha 21066), Debian unstable, 2.4.6
Works without problems

I do think that blindly reading /dev/mem is a bad idea though ;)


On Mon, Aug 26, 2002 at 01:20:33AM -0500, Branden Robinson wrote:
> The long story, for those interested:
> http://lists.debian.org/debian-x/2002/debian-x-200208/msg00091.html
> (and read the whole thread)
> The short story:
> I need people with root on machines of your given architecture to
> compile and run the attached C program.  It consists of code borrowed
> from xdm's genauth.c program.
> The X Strike Force is trying to determine for which architectures it's a
> bad idea to read several megabytes of data sequentially from /dev/mem,
> because this is exactly what XDM currently does when generating an
> Be warned: on at least some architectures (notably IA-64), this sort of
> read has been known to cause untrapped machine checks (a.k.a., lockups
> or spontaneous reboots).  Arguably the kernel should trap this sort of
> nonsense, so you may be in the mood to file a bug against "kernel" after
> running this program.
> I and the other folks at the X Strike Force need to know the following
> things:
> 1) whether or not this program works when you run it without arguments
> 2) if scenario 1) causes problems, what the last line of output was
> 3) if scenario 1) causes problems, whether invoking this program with
> the argument "fragile" helps it
> 4) if scenario 3) causes problems, what the last line of output was
> Remember, this program must be run as root.  If normal users can read
> from /dev/mem on your machine, you're in trouble.  :)
> -- 
> G. Branden Robinson                |     No math genius, eh?  Then perhaps
> Debian GNU/Linux                   |     you could explain to me where you
> branden@debian.org                 |     got these...       PENROSE TILES!
> http://people.debian.org/~branden/ |     -- Stephen R. Notley

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