Messages in this thread | | | Date | Sat, 16 Feb 2008 15:29:07 +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:
> On Sat, Feb 16, 2008 at 02:48:17PM +0100, Thomas Gleixner wrote: > > 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. > > To be more precise: dereferencing alone won't cause an exception for > NULL pointers on s390. Only writes will do so. > That is very architecture specific since we cannot unmap page 0, > it contains per-cpu data -- like exception pointers and all such stuff > that the cpu needs. > Just in case there is any code that relies on the fact that also reads > via a NULL pointer are supposed to failed.
Hmm, not sure whether there is such code, but then it would be not too bad to add
if (!p) return -EFAULT;
to the S390 implementations which only read data and have an exception fixup.
Thanks,
tglx
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