Re: [Xen-devel] [PATCH] xen: arm: handle initrd addresses above the 4G boundary

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 12/09/2013 02:00 PM, Ian Campbell wrote:
> On Mon, 2013-12-09 at 13:52 +0000, Julien Grall wrote:
> > On 12/09/2013 11:15 AM, Ian Campbell wrote:
> > > On Fri, 2013-12-06 at 17:39 +0000, Julien Grall wrote:
> > > > > > Perhaps you update the comment by saying we are assuming bytes is 4-byte
> > > > > > aligned.
> > > > > Maybe it would be better to round up?
> > > > No because if we round up, we would read to much data. dt_read_number is
> > > > not able to check the size.
> > > Right.
> > >
> > > I think what I shall do is change the caller to accept exactly
> > > sizeof(u32) or sizeof(u64) bytes and not any value between.
> > It's fine to have size between sizeof(u32) or sizeof(u64), the address
> > will just be truncated.
> >
> > We have several location in Xen, where we rely on this behavior.
> Do you have examples?
>
> Since dt_read_number can't cope with anything which isn't a multiple of
> 32-bits I don't see a problem with rejecting them early instead of
> waiting until later and failing with an obscure error because an address
> has been truncated.
In smp_init_cpus (arch/arm/smpboot.c), Xen only checks that reg_len is 
greater than the required number of cells.
--
Julien Grall

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