On Wed, 2005-04-13 12:21:41 +0800, Tomko <[EMAIL PROTECTED]> wrote in message <[EMAIL PROTECTED]>: > While i am reading the source code of the linux system call , i find > that the system call need to call copy_from_user() to copy the data from > user space to kernel space before using it . Why not use it directly as > the system call has got the address ? Furthermore , how to distinguish > between user space and kernel space ?
Think about the memory access. The page that contains the data could be swapped out, so the kernel isn't allowed to just access it, because it's not there. MfG, JBG -- Jan-Benedict Glaw [EMAIL PROTECTED] . +49-172-7608481 _ O _ "Eine Freie Meinung in einem Freien Kopf | Gegen Zensur | Gegen Krieg _ _ O fuer einen Freien Staat voll Freier BÃrger" | im Internet! | im Irak! O O O ret = do_actions((curr | FREE_SPEECH) & ~(NEW_COPYRIGHT_LAW | DRM | TCPA));
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