Messages in this thread | | | Date | Sun, 17 Jan 2010 09:40:43 -0800 | From | Arjan van de Ven <> | Subject | Re: /dev/mem implementation |
| |
On Sun, 17 Jan 2010 18:47:10 +0200 Felix Rubinstein <felixru@gmail.com> wrote:
> I see the motivation to limit the access to DRAM from root account > CONFIG_STRICT_DEVMEM by mmap'ing /dev/[k]mem but it's easily overruled > by simple char driver and implementing mmap of it's own totally > bypassing all limitations. > > What do you think about it guy? > Appreciate it.
the reason PAT bans parts of /dev/mem is simple: it is illegal to have mapping aliases (different cachability) for the same physical page. Normal kernel APIs take care of this for the normal case, but /dev/mem would be a back door into that. This is a hardware imposed requirement, and violating the rule can have really nasty consequences... hence the PAT code just not allowing it.
If you feel that you have a valid use case where you really want do muck with such memory, it might be a good idea to explain that usecase....
-- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org
| |