Re: [Xen-devel] [PATCH] xen: arm: correct use of find_next_bit

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-01-24 at 14:48 +0000, Ian Campbell wrote:
> On Fri, 2014-01-24 at 14:36 +0000, Julien Grall wrote:
> > On 01/24/2014 02:23 PM, Ian Campbell wrote:
> > > find_next_bit takes a "const unsigned long *" but forcing a cast of an
> > > "uint32_t *" throws away the alignment constraints and ends up causing an
> > > alignment fault on arm64 if the input happened to be 4 but not 8 byte 
> > > aligned.
> > > 
> > > Instead of casting use a temporary variable of the right type.
> > > 
> > > I've had a look around for similar constructs and the only thing I found 
> > > was
> > > maintenance_interrupt which cases a uint64_t down to an unsigned long, 
> > > which
> > > although perhaps not best advised is safe I think.
> > > 
> > > This was observed with the AArch64 Linaro toolchain 2013.12 but I think 
> > > that
> > > is just coincidental due to subtle changes to the stack layout etc.
> > > 
> > > Reported-by: Fu Wei <fu.wei@xxxxxxxxxx>
> > > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > 
> > Good catch! Do you plan to apply this patch for Xen 4.4?
> 
> Yes, I think it is a suitable bug fix.

Applied, thanks.



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