Timur Tabi <[EMAIL PROTECTED]> writes:
> I'm confused about something in usercopy_64.c:
>
> unsigned long copy_from_user(void *to, const void __user *from, unsigned long
> n)
> {
> if (likely(access_ok(VERIFY_READ, from, n)))
> n = __copy_from_user(to, from, n);
> else
> memset(to, 0, n);
> return n;
> }
>
> If access_ok() returns false, then that means that we cannot copy the data
> from
> user-space. So why are we returning 'n'?
To tell the caller that the function failed. The result is the number
of bytes _left_ to be copying, ie. zero means success.
Andreas.
--
Andreas Schwab, SuSE Labs, [EMAIL PROTECTED]
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
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