Because kernel does not want userspace to modify the passed data while it process the same data.
Copy from/to user
Validates buffer
Copy buffer to/from user so it does not have worry about data being updated in user space.
Question
As we all know that kernel has access to user space also. Thus, it doesn't need the special function - copy_to_user()
. Why is it required then? The kernel can access the user space address directly. Isn't it?
Solution
Because kernel does not want userspace to modify the passed data while it process the same data.
Copy from/to user
Validates buffer
Copy buffer to/from user so it does not have worry about data being updated in user space.
OTHER TIPS
Note that on some architectures, it's not implemented with a simple memcpy()
: