Re: Why system call need to copy the date from the userspace beforeusing it

[Tomko]

Catalin Marinas wrote:

> Tomko <tomko@xxxxxxxx> wrote:
>  
>
> > Inside the system call , the kernel often copy the data by calling
> > copy_from_user() rather than just using strcpy(), is it because the
> > memory mapping in kenel space is different from user space?
> >    
>
> No, it is because this function checks whether the access to the user
> space address is OK. There are situations when it can also sleep (page
> not present).
>
>  
what u means "OK"?  kernel space should have right to access any memory 
address , can u expained in details what u means "OK"?
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