Use of copy_to_user() and copy_from_user() functions

[पारस]

Hi All,

To read/write data to user-space from kernel-space we use copy_from_user()
and copy_to_user() functions.

What is the use of these function?
Why kernel can't directly access user address and read/write on to it?
Can any one explain why kernel can't directly access the user-space
address.

Thanks
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