copy_from_user user space address mapping in the kernel page table.

[mind entropy]

Hi,
  In the copy_from_user when the user passes the virtual address is
the address mapped in the kernel page tables? In the function there is
a source is a user virtual address(<3GB) and the destination is the
kernel virtual address(3GB - 4GB) and for the MMU to access the
physical page frame when in kernel space operating in behalf of the
process context there should be a mapping of the virtual address to
the page frame, correct?

  I am assuming the implementation would be to take the virtual
address and walk the page table to get to the physical page frame and
map the physical page frame in the kernel page table (i.e.
swapper_pgd). Is this correct? If not what would be the mechanism?

Thanks,
Gautam.