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Re: [Xen-devel] [PATCH for-4.13] xen/arm32: head: Fix build when using GAS 2.25.0



On 01.10.19 02:57, Stefano Stabellini wrote:
On Mon, 30 Sep 2019, Andrew Cooper wrote:
On 30/09/2019 19:44, Julien Grall wrote:
GAS 2.25.0 throws multiple errors when building arm32/head.S:

arm32/head.S: Assembler messages:
arm32/head.S:452: Error: invalid constant (f7f) after fixup
arm32/head.S:453: Error: invalid constant (f7f) after fixup
arm32/head.S:495: Error: invalid constant (f7f) after fixup
arm32/head.S:510: Error: invalid constant (f7f) after fixup
arm32/head.S:514: Error: invalid constant (f7f) after fixup
arm32/head.S:516: Error: invalid constant (f7f) after fixup
arm32/head.S:633: Error: invalid constant (f7f) after fixup

This makes sense because the instruction mov is only able to deal with a
specific set of immediate (see "modified immediate constants in ARM
instructions"). For any 16-bit immediate, the instruction movw should be
used.

It looks like newer version of GAS will seemly switch to movw if the
immediate does not fit in the immediate encoding for mov. But we should
not rely on this. So switch to movw.

Fixes: 23dfe48d10 ("xen/arm32: head: Introduce macros to create table and mapping 
entry")
Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

FWIW, Tested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, only insofar
as it fixing the build.  I haven't booted the resulting binary.

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

Given that this is a straightforward build fix, and due to timezone
differences, I have committed it (after verifying it fixes the build
myself). I hope that Juergen approves.


I do.


Juergen

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