How can I test if a physical address is already mapped or not.

[Rajat Sharma]

On Tue, Oct 18, 2011 at 1:34 AM, StephanT <stman937-linewbie at yahoo.com> wrote:
> Hi all,
> In a kernel module is there a way to test if an address range has
> been already mapped by the kernel or not.
> Ex:  (on a PC with the latest kernel)
> - an access to physical 0xC0000000 will return the value at this address
> - an access to physical 0x00100000 will have the kernel kill the
> module/application
>            using the module. Dmesg: BUG: unable to handle kernel paging
> request at 00100000.
>
> How can I test this condition before dereferencing the address.
> Thanks,
> Stephan.
>
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>

When you say an access to physical address, how are you managing to
access the physical address directly?