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

[StephanT]

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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