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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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.

Ian.


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