linux-kernel - Re: [PATCH v2] x86, kconfig: Pick up the .config arch version in 'make oldconfig'

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Date:	Fri, 24 Jun 2011 15:37:40 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86, kconfig: Pick up the .config arch version in
 'make oldconfig'

On 30.5.2011 12:09, David Woodhouse wrote:
> I wasted a bunch of time today because I'd taken a .config from my
> test machine and tried to build it, and the existing setting of
> CONFIG_X86_32 got changed to the host system's bitness which was
> 64-bit.
>
> This patch fixes that. Last time I tried to fix this bug, I had
> introduced a regression that broke:
>
>     make ARCH=x86_64 randconfig
>     make ARCH=i386 randconfig
>
> type of filtered-randconfig behavior which restricted randconfigs to
> 64-bit and 32-bit configs, respectively.
>
> This version fixes that so prior randconfig behavior is maintained,
> although if a "filtered randconfig" is desired it seems like it would be
> better to actually implement that properly, rather than relying on a
> hack which preserves the obsolete 'ARCH=i386' and 'ARCH=x86_64' legacy
> just to influence *one* of the many config options that might need to be
> hard-coded if you actually want a 'randconfig' that produces a useful
> end-result.
>
> Signed-off-by: David Woodhouse<David.Woodhouse@...el.com>
> Link: http://lkml.kernel.org/r/1306707270.2029.377.camel@i7.infradead.org
>
> ---
> v2: Explicitly turn off CONFIG_64BIT in i386_defconfig. The default for
> CONFIG_64BIT has *changed* (from n to y) for ARCH=x86, so it needs to be
> explicitly turned off or 'make i386_defconfig' will give you 64-bit :)
>
> diff --git a/Makefile b/Makefile
> index 123d858..7b3b7c5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -165,7 +165,8 @@ export srctree objtree VPATH
>   # then ARCH is assigned, getting whatever value it gets normally, and
>   # SUBARCH is subsequently ignored.
>
> -SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/sun4u/sparc64/ \
> +SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
> +				  -e s/sun4u/sparc64/ \
>   				  -e s/arm.*/arm/ -e s/sa110/arm/ \
>   				  -e s/s390x/s390/ -e s/parisc64/parisc/ \
>   				  -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index cc6c53a..1f206b0 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1,7 +1,7 @@
>   # Select 32 or 64 bit
>   config 64BIT
>   	bool "64-bit kernel" if ARCH = "x86"
> -	default ARCH = "x86_64"
> +	default ARCH != "i386"

This breaks all{mod,yes}config on 32bit and allnoconfig on 64bit (and 
randconfig sometimes :)). The user expectation is that make 
defconfig/allmodconfig/allyesconfig builds a kernel for their 
architecture. You only handle defconfig below.

Michal
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