/dev/mem implementation

From: Felix Rubinstein
Date: Sun Jan 17 2010 - 11:47:18 EST

The recent kernels use CONFIG_STRICT_DEVMEM and CONFIG_X86_PAT
concerning the /dev/mem (/dev/kmem) so interchangeably one cannot
figure out what exactly does it mean to access the /dev/mem if both

It would be more logically to remove pat_enabled variable in
arch/x86/mm/pat.c and to make everything under CONFIG_X86_PAT define.
The same goes for phys_mem_access_prot_allowed function (from
arch/x86/mm/pat.c) even though CONFIG_X86_PAT is disabled.
To make the story worse there are four implementations of
range_is_allowed depending on how CONFIG_STRICT_DEVMEM and
CONFIG_X86_PAT are defined.

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.

Felix R.
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