linux-kernel - Re: [PATCH v2] x86, boot: Fix word-size assumptions in has

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Message-ID: <1391090899.26079.103.camel@shinybook.infradead.org>
Date:	Thu, 30 Jan 2014 14:08:19 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	keescook@...omium.org, tglx@...utronix.de, hpa@...ux.intel.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [PATCH v2] x86, boot: Fix word-size assumptions in has_eflag ()
 inline asm

On Thu, 2014-01-30 at 05:45 -0800, H. Peter Anvin wrote:
> This would seem like a job for <asm/asm.h>.

Except that's all done on CONFIG_X86_32 which isn't useful for what we
are doing here.

We could, potentially, *change* <asm/asm.h> so that it actually makes
its choices based on whether __x86_64__ is defined?

Which would probably work, except for the next horrid corner case I
haven't discovered/realised yet :)

I think I'm inclined to keep this fairly localised, unless we really see
a case for doing it elsewhere in the kernel. Which is unlikely since a
bare 'pushf' should always do the right thing except in the weird
no-mans-land that is building 16-bit code with a 32-bit compiler.

I note that BITS_PER_LONG==64 even when building the 16-bit code as part
of a 64-bit kernel, too. That one is just waiting to bite us some day...

-- 
dwmw2

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