why kernel heap and code copied in fork()

[psnix]

in j.m tutorial say we must copy kernel heap and code to the child process:

http://www.jamesmolloy.co.uk/tutorial_h ... sking.html

why we need to copy kernel heap and code to the every child process in fork?

[NickJohnson]

You don't want to copy it, but you do want to link it in the same place. I don't see anything in the tutorial about copying the kernel code/data.