Hi Vishal, On Sun, Jul 3, 2011 at 5:09 AM, Vishal Thanki <vishalthanki@xxxxxxxxx> wrote: > Hi, > > We use copy_from_user/copy_to_user functions to copy data transfer > user data between user space and kernel space. As per my > understanding, these functions are required because we cannot access > userspace data directly within kernel space. But, the implementation > of these functions actually access the user-space data right? Can > someone explain me how this actually happens? How it actually happens is architecture dependent. Whether kernel space can access user space while in the context of the user-process is also architecture dependent. I know with ARM, for example, it's possible to do memcpy instead of copy_to_user, but using memcpy isn't guaranteed to work on all architectures. The other difference between memcpy and copy_to/from_user is that memcpy will typically cause a segmentation fault if passed a bad pointer, where copy_to/from_user won't. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
