Re: [PATCH] ARM: 8680/1: boot/compressed: fix inappropriate Thumb2 mnemonic for __nop

[Sasha Levin <sashal@kernel.org>]

On Wed, May 08, 2019 at 01:59:51PM -0500, Chris Brandt wrote:
>From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>
>[ Upstream commit 60ce2858514ed9ccaf00dc7e9f4dc219537e9855 ]
>
>Commit 06a4b6d009a1 ("ARM: 8677/1: boot/compressed: fix decompressor
>header layout for v7-M") fixed an issue in the layout of the header
>of the compressed kernel image that was caused by the assembler
>emitting narrow opcodes for 'mov r0, r0', and for this reason, the
>mnemonic was updated to use the W() macro, which will append the .w
>suffix (which forces a wide encoding) if required, i.e., when building
>the kernel in Thumb2 mode.
>
>However, this failed to take into account that on Thumb2 kernels built
>for CPUs that are also ARM capable, the entry point is entered in ARM
>mode, and so the instructions emitted here will be ARM instructions
>that only exist in a wide encoding to begin with, which is why the
>assembler rejects the .w suffix here and aborts the build with the
>following message:
>
>  head.S: Assembler messages:
>  head.S:132: Error: width suffixes are invalid in ARM mode -- `mov.w r0,r0'
>
>So replace the W(mov) with separate ARM and Thumb2 instructions, where
>the latter will only be used for THUMB2_ONLY builds.
>
>Fixes: 06a4b6d009a1 ("ARM: 8677/1: boot/compressed: fix decompressor ...")
>Reported-by: Arnd Bergmann <arnd@arndb.de>
>Acked-by: Arnd Bergmann <arnd@arndb.de>
>Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
>Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
>---
>
>For the 4.9.x tree, commit 7b5407843691 was applied, but that caused
>an issue for CONFIG_THUMB2 builds as you can see in the commit
>message above.
>
>Therefore, this upstream fix (that came 2 weeks later) is also required
>in the 4.9.x tree to make it build again.

I've queued 60ce2858514 for 4.9, thanks!

--
Thanks,
Sasha