Messages in this thread | | | Date | Sat, 16 Feb 2008 14:48:17 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: + futex-runtime-enable-pi-and-robust-functionality.patch added to -mm tree |
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On Sat, 16 Feb 2008, Heiko Carstens wrote:
> > Well, NULL pointer dereferencing is supposed to fail, isn't it ? > > I wasn't sure that this is true for all architectures, but...
It's an requirement for futex support.
> > > Indeed it does fail with an Oops on s390 since we enable low address > > > protection in the kernel so we get an exception if something within the > > > kernel writes to the first 512 bytes of the kernel address space. > > > Otherwise it would have silently passed the test... > > > > NULL pointer dereferencing faults on all architectures, at least it > > should, but we explicitely disable pagefaults and recover via the > > extable fixup, which is in S390 as well. That returns -EFAULT and > > signals that there is a working implementation, while those which have > > no support return -ENOSYS, which keeps the robust/pi stuff disabled. > > ...one of our exception table entries has an off-by-one bug. > Never mind, I'll go and fix our own stuff instead ;)
Maybe we should do such tests on all exception table protected assembler constructs :)
Thanks,
tglx
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