privilege mode access to coprocessor register


I want the privilege and user mode access to the coprocessor register
C0, C1

I tried to write following for the c1 and c0 coprocessor

mrc p15, 0, r0, c1, c0, 2 @ read the coprocessor access control reg
    @@ write '1111' to bits 3,2,1,0 - which should enable user- and
    @@ privilege- mode access to the c1, c0 coprocessor
    orr r0, r0, #0x000f @
    mcr p15, 0, r0, c1, c0, 2 @ write back

With this much change, I can build the kernel without any error but
when I use the instruction "MRC p15. 0, r0, c1, c0, 1" in my code it
gives "illegal instruction error with this new uImage. so do you any
reason? Can any one suggest me?