On Sat, Feb 05, 2005 at 03:44:48PM -0800, David S. Miller wrote: > On Sat, 5 Feb 2005 09:06:19 +0000 > Russell King <[EMAIL PROTECTED]> wrote: > > > Except that "addr_limit" may be defined by an architecture to be zero > > (which can be interpreted as 4GB by the arch specific code) for the > > case where we allow kernel mode access. > > I believe this to be a problematic scheme, let me explain why. > > First, "set_fs(KERNEL_DS)" allows kernel mode access, but it absolutely > must not allow user mode accesses. It seems to suggest we might need > some "addr_min" value for access_ok() checking purposes...
That's an unreasonable requirement which no architecture other than those with truly separate address spaces follow. I think on the others it would lead to quite bad code bloat for the additional tests (access_ok is called very often) -Andi
