[PATCH] arm: boot/compressed: fix inappropriate Thumb2 mnemonic for __nop

[Ard Biesheuvel]

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 CPU_THUMBONLY builds.

Fixes: 06a4b6d009a1 ("ARM: 8677/1: boot/compressed: fix decompressor ...")
Reported-by: Arnd Bergmann <arnd at arndb.de>
Acked-by: Arnd Bergmann <arnd at arndb.de>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
---

Apologies for the breakage: apparently, the combination CONFIG_THUMB2_KERNEL=y,
CONFIG_CPU_THUMBONLY=n and CONFIG_EFI_STUB=y was not among the configurations
I tested before sending out the original patch.

 arch/arm/boot/compressed/efi-header.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S
index 3f7d1b74c5e0..a17ca8d78656 100644
--- a/arch/arm/boot/compressed/efi-header.S
+++ b/arch/arm/boot/compressed/efi-header.S
@@ -17,7 +17,8 @@
 		@ there.
 		.inst	'M' | ('Z' << 8) | (0x1310 << 16)   @ tstne r0, #0x4d000
 #else
-		W(mov)	r0, r0
+ AR_CLASS(	mov	r0, r0		)
+  M_CLASS(	nop.w			)
 #endif
 		.endm
 
-- 
2.9.3