linux-kernel - Re: [PATCH] Disable -fconserve-stack on ARM

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Message-ID: <20110531163026.GB771@e102109-lin.cambridge.arm.com>
Date:	Tue, 31 May 2011 17:30:26 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Måns Rullgård <mans@...sr.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Nicolas Pitre <nico@...xnic.net>,
	Will Deacon <Will.Deacon@....com>,
	lkml <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, sam@...nborg.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] Disable -fconserve-stack on ARM

On Sat, May 28, 2011 at 04:34:17PM +0100, Andi Kleen wrote:
> Disable -fconserve-stack on ARM
> 
> There are reports that -fconserve-stack misaligns variables on the stack.
> Disable it for ARM to work around this gcc bug.
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> 
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index 25750bc..0883cff 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -41,6 +41,10 @@ ifeq ($(CONFIG_CC_STACKPROTECTOR),y)
>  KBUILD_CFLAGS  +=-fstack-protector
>  endif
> 
> +# ARM gcc developers unfortunately broke -fconserve-stack. It misaligns
> +# variables on the stack
> +KBUILD_CFLAGS += $(call cc-option,-fno-conserve-stack)

Didn't work, on the gcc command line we get -fno-conserve-stack followed
by -fconserve-stack from the top makefile and it seems that the latter
takes priority.

-- 
Catalin

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