RE: [PATCH 8/9] xen/arm: Allow the user to build Xen with USBAN

[Henry Wang <Henry.Wang@xxxxxxx>]

Hi Julien,

> -----Original Message-----
> From: Julien Grall <julien@xxxxxxx>
> Subject: [PATCH 8/9] xen/arm: Allow the user to build Xen with USBAN

Typo in title: s/USBAN/UBSAN/ and...

> 
> 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 USBAN and GCOV which would put

...here also.

> 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>

Both typos can be fixed on commit and I think I am good with the
current approach, so:

Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>

I did a play with UBSAN enabled on FVP (arm64), in my setup,
the result Xen file is 3.7MB:

-rwxrwxr-x  1 xinwan02 xinwan02 3.7M Jun 26 14:47 xen
lrwxrwxrwx  1 xinwan02 xinwan02    3 Jun 26 14:47 xen.efi -> xen
-rwxrwxr-x  1 xinwan02 xinwan02  14M Jun 26 14:47 xen-syms

and the Xen and Dom0 booted fine and I can login Dom0. So
technically:

Tested-by: Henry Wang <Henry.Wang@xxxxxxx>

However, I noticed Xen will print below during the Dom0 boot:
(XEN) 
================================================================================
(XEN) UBSAN: Undefined behaviour in arch/arm/vgic.c:371:15
(XEN) left shift of 1 by 31 places cannot be represented in type 'int'
(XEN) Xen WARN at common/ubsan/ubsan.c:172

Just want to make sure you also noticed this, otherwise maybe you
can include another patch in the series to fix this? Or I can do that
in case you don't have enough bandwidth.

Kind regards,
Henry