Re: [Xen-devel] [PATCH v2 3/5] xen/livepatch/ARM32: Don't load and crash on livepatches loaded with wrong alignment.

["Jan Beulich" <jbeulich@xxxxxxxx>]

>>> Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx> 07/26/17 9:50 PM >>>
>--- a/docs/misc/livepatch.markdown
>+++ b/docs/misc/livepatch.markdown
>@@ -279,6 +279,10 @@ It may also have some architecture-specific sections. For 
>example:
>* Exception tables.
>* Relocations for each of these sections.
 >
>+Note that on ARM 32 the sections SHOULD be four byte aligned. Otherwise
>+we risk hitting Data Abort exception as un-aligned manipulation of data is
>+prohibited on ARM 32.

This (and hence the rest of the patch) is not in line with the outcome of the
earlier discussion we had. Nothing is wrong with a section having smaller
alignment, as long as there are no 32-bit (or wider, but I don't think there
are any such) relocations against such a section. And even if there were, I
think it should rather be the code doing the relocations needing to cope, as
I don't think the ARM ELF ABI imposes any such restriction.

Jan


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