Messages in this thread | | | Date | Fri, 29 Nov 2002 22:51:52 +0000 | From | Russell King <> | Subject | Re: v2.4.19-rmk4 slab.c: /proc/slabinfo uses broken instead of slab labels |
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On Fri, Nov 29, 2002 at 07:24:02PM +0100, Manfred Spraul wrote: > Russell King wrote: > >On Thu, Nov 28, 2002 at 11:34:20PM +0100, Manfred Spraul wrote: > > > > > >>On i386, it's possible to skip set_fs() and use __get_user() - but > >>that's i386 specific. For example the i386 oops code uses that. > >> > >> > > > >That isn't actually an x86 specific feature - it is a requirement across > >all architectures that get_user() and friends can access kernel areas > >after set_fs(get_ds()) > > > > > It's i386 specific that > __get_user(). > is equivalent to > set_fs(KERNEL_DS) > get_user() > arch/i386/kernel/traps.c uses that in the fault code. > > Portable code must use set_fs()/get_user(), i386 specific code can > continue to use __get_user().
That seems broken to me. IIRC, when all this uaccess stuff went in back in 2.1 times, the original intention was that __get_user() would fault even when used from kernel mode, unless set_fs(KERNEL_DS) was in effect.
__get_user() at that time was always meant to be used as a faster version of get_user(), even by generic code, and relied solely on the TLB protection mechanisms, whereas get_user() verified the address.
Gah, I _really_ wish that we had a method to notify architecture maintainers when this type of stuff changes. Are we supposed to re-read the x86 implementation of everything for each kernel release to try to discover what subtle semantics have changed?
-- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html
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