linux-kernel - Re: [PATCH 04/10] ARM: pass -marm to gcc by default

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Message-ID: <alpine.LFD.2.02.1208091709010.5231@xanadu.home>
Date:	Thu, 9 Aug 2012 17:12:58 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
cc:	linux-arm-kernel@...ts.infradead.org, arm@...nel.org,
	linux-kernel@...r.kernel.org,
	Russell King <rmk+kernel@....linux.org.uk>,
	Dave Martin <dave.martin@...aro.org>
Subject: Re: [PATCH 04/10] ARM: pass -marm to gcc by default

On Wed, 8 Aug 2012, Arnd Bergmann wrote:

> The Linaro cross toolchain and probably others nowadays default to
> building in THUMB2 mode. When building a kernel for a CPU that does
> not support THUMB2, the compiler complains about incorrect flags.
> We can work around this by setting -marm for all non-T2 builds.
> 
> Without this patch, building assabet_defconfig results in:
> 
> usr/initramfs_data.S:1:0: warning: target CPU does not support THUMB instructions [enabled by default]
> arch/arm/nwfpe/entry.S:1:0: warning: target CPU does not support THUMB instructions [enabled by default]
> firmware/cis/PCMLM28.cis.gen.S:1:0: warning: target CPU does not support THUMB instructions [enabled by default]
> (and many more)
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Cc: Russell King <rmk+kernel@....linux.org.uk>
> Cc: Dave Martin <dave.martin@...aro.org>
> ---
>  arch/arm/Makefile |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index 30eae87..b4c2296 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -111,6 +111,9 @@ AFLAGS_THUMB2	:=$(CFLAGS_THUMB2) -Wa$(comma)-mthumb
>  ifeq ($(CONFIG_THUMB2_AVOID_R_ARM_THM_JUMP11),y)
>  CFLAGS_MODULE	+=-fno-optimize-sibling-calls
>  endif
> +else
> +CFLAGS_THUMB2  :=-marm
> +AFLAGS_THUMB2	:=-marm

CFLAGS_THUMB2 should probably be renamed to something more appropriate 
in this case, e.g. CFLAGS_MODE.


Nicolas
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