On Wed, 11 Aug 2010 21:22:51 -0700 "H. Peter Anvin" <hpa@xxxxxxxxx> wrote: > [Adding Linux and linux-arch. The context is that get_user/put_user > don't work on 64 bit values on i386.] > > On 08/11/2010 05:33 PM, Andrew Morton wrote: > > > > Anyway, this should be fixed in x86 core, I suspect. > > After looking at it -- and suffering a bad case of d__j__ vu -- I'm > reluctant to change it, as get/put_user are specified to work only on > locally atomic data: > > * This macro copies a single simple variable from user space to kernel > * space. It supports simple types like char and int, but not larger > * data types like structures or arrays. > > Given that u64 is not a simple type on 32 bits, it would appear that the > behavior is intentional. > > A user might very well find that supporting u64 and/or structure types > would be beneficial, but it would a) be a semantic change, and b) would > introduce the possibility of a partially completed transfer. That is a > semantic change to the interface. However, it may very well be nicer to > have a generally available get_user()/put_user() for the cases which > would just kick an EFAULT up the stack when they fail anyway. > > If there is consensus for making get_user/put_user a general interface, > I'm more than willing to do the x86 changes, but I don't want to do them > a) unilaterally and b) for 2.6.36. This seems like .37 material at this > point. It occurs so rarely that it's probably not worth bothering about, IMO. However we should arrange for it to fail at compile time rather than at link time, please. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
