Aboo Valappil wrote:
You must be tired of answering questions :)
It's relaxing. More to the point, when I started working with Linux there were no useful fora such as this to help me so I learn by as always by pottering along and making various mistakes on the way.
[ discussion about copy_[from|to]_user context ]
*). Check page is available.
Point number 2 here ( check page is available ) ... What if page is not available and there is no page table/page directory set up for this ?
Then the process just issued a dud request (in which case the memory will not exist within the current process' vmas) or the page is part of a valid mapping but not in memory so it needs to be brought in.
Does it cause a page fault ?
If there's no valid page table entry then the fault handler will run and it knows if we're in the kernel already when it gets called.
Why is copy_to_user() required ?
Mostly to check that any access is allowed and valid for a given process. The standard fault handler will run if necessary.
Jon.
-- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
