Re: [Xen-devel] Should we revert "mm: New XENMEM space, XENMAPSPACE_gmfn_range"?

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 2 Aug 2012, Jan Beulich wrote:
> >>> On 01.08.12 at 19:55, Stefano Stabellini 
> >>> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > I was reading more about this commit because this patch breaks the ABI
> > on ARM, when I realized that on x86 there is no standard that specifies
> > the alignment of fields in a struct.
> 
> There is - the psABI supplements to the SVR4 ABI.

Thank you very much, that document was exactly what I was looking for.

Also it explains where my confusion was coming from: Jean's patch doesn't
break the ABI on ARM or x86, but I am carrying a patch in my patch queue
that does (unless Jean's patch is applied):

http://marc.info/?l=xen-devel&m=134305777903771

As you can see this patch splits .space into two shorts, and as a side
effect changes the offset of .space, removing the padding.
Thus it led me to think that Jean's patch was breaking the ABI when actually
with "arm: initial XENMAPSPACE_gmfn_foreign" applied, it becomes
required to keep the binary interface compatible.

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