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Re: [v2 4/4] xen/arm: Allow the user to build Xen with UBSAN


  • To: Julien Grall <julien@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Michal Orzel <michal.orzel@xxxxxxx>
  • Date: Fri, 30 Jun 2023 08:58:23 +0200
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  • Cc: <Luca.Fancellu@xxxxxxx>, <Henry.Wang@xxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>
  • Delivery-date: Fri, 30 Jun 2023 06:58:43 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>


On 29/06/2023 22:11, Julien Grall wrote:
> 
> 
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> UBSAN has been enabled a few years ago on x86 but was never
> enabled on Arm because the final binary is bigger than 2MB (
> the maximum we can currently handled).
> 
> With the recent rework, it is now possible to grow Xen over 2MB.
> So there is no more roadblock to enable Xen other than increasing
> the reserved area.
> 
> On my setup, for arm32, the final binaray was very close to 4MB.
> Furthermore, one may want to enable UBSAN and GCOV which would put
> the binary well-over 4MB (both features require for some space).
> Therefore, increase the size to 8MB which should us some margin.
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> 
> ---
> 
> The drawback with this approach is that we are adding 6 new
> page-table (3 for boot and 3 for runtime) that are statically
> allocated. So the final Xen binary will be 24KB bigger when
> neither UBSAN nor GCOV.
> 
> If this is not considered acceptable, then we could make the
> size of configurable in the Kconfig and decide it based on the
> features enabled.
> 
>     Changes in v2:
>         - Fix typoes
>         - Add Michal's reviewed-by tag
I cannot see one, so:
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>

~Michal




 


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