copy_from_user/copy_to_user question

From: Vinay Venkataraghavan
Date: Fri Dec 02 2005 - 17:40:37 EST

I have a question regarding copy_to_user and
copy_from_user, specifically the conditons and
situations when they can be used.

Firstly, I guess it is always safe to use these
funtions when making an ioctl call.

But my question is: Are there any specific
circumstances or conditions when these functions don't
have to be used, but at the same time ensure that no
page fault occurs and crashes the system.

The reason I ask is, there is some software that I am
dealing with that just don't use these functions.

Secondly, they seem to use memcpy as opposed to using
copy_to_user/copy_from_user which is also very

Any thoughts?


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