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SubjectRe: Copy_to_user and copy_from_user
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Then, how do I make sure that all the data I wanted to be copied is infact
copied?? What are the scenarios where copy_to/from_user could fail and how
can I avoid it.

Thanks
-Ramesh


>
>No you cannot call it until all data has been copied. copy_{to,from}_user
>fails when a fault happens during the copy process. So you simply cannot
>try again... It will fault again.
>Well, not 100% true. An other running thread (same mm with the process
>which copies data) can "fix" the faulty adress space. Bad thread....
>
>Ramesh Sudini wrote:
>>Hi,
>>
>>If copy_from_user returns non zero value, then I do not see any driver(for
>>example PPP) try to copy the remaining data. It treats it as an error
>>scenario.
>>
>>Why is this? Shouldnt it have a while loop and attempt to copy_from_user
>>till all the data is copied??
>>
>>I am writing a driver and trying to understand what needs to be done in
>>case it returns a non-zero value? I have huge amount of data to be copied
>>from user space Ex: 3000byte messages.
>>
>>Can somebody suggest me what is the best I could do...(Please cc me
>>personally with your response)
>>
>>Thanks
>>Ramesh
>>

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