linux-kernel - Re: [PATCH] x86: do not expose CONFIG

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Date:	Wed, 28 Jan 2009 14:13:35 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Harvey Harrison <harvey.harrison@...il.com>
cc:	"H. Peter Anvin" <hpa@...or.com>,
	"H. Peter Anvin" <hpa@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	Jaswinder Singh Rajput <jaswinderrajput@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] x86: do not expose CONFIG_BSWAP to userspace



On Wed, 28 Jan 2009, Harvey Harrison wrote:
>
> Use ifdef __i486__ to ensure the BSWAP instruction is available
> on 32-bit x86.
> 
> Signed-off-by: Harvey Harrison <harvey.harrison@...il.com>
> ---
> HPA,
> 
> I'm afraid my knowledge of gcc compiler flags for various models is
> lacking, I used i486 as suggested, just wanted to make sure I understood
> you corectly.

I really don't think this works.

Try this:

	cpp -dM -m32 -march=pentium t.c | grep i486

and see the marked absense of __i486__ anywhere.

At least CONFIG_X86_BSWAP gives the right behaviour for the kernel.

			Linus
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