Re: RFC: banning device driver reserved resources from /dev/mem

[Alan Cox]

> This patch adds, to the existing config option to restrict /dev/mem, the
> reserved regions to the "banned from /dev/mem use" list, so now
> both kernel memory and device-exclusive MMIO regions are banned.

This breaks a whole class of diagnostic and debug tools which quite
intentionally dump the MMIO register space of devices that are live.

Plus it doesn't actually work - if I have /dev/mem open and mmapped you
don't pull the pages from under me....

The problem with the way this is going is the more you take from /dev/mem
the sooner someone is forced to add /dev/mem-proper which undoes it all
again so they can get work done.

It's certainly a useful debug aid to know about such things but I don't
believe it's something you should ban.

Alan
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