linux-kernel - Re: [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get

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Message-ID: <CAMe9rOrTLGJvO+Z8kCG3gmOuW-Yq2Ex9WMfJZ5wmZcbz+zm94Q@mail.gmail.com>
Date:	Tue, 12 Feb 2013 08:38:36 -0800
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jamie Lokier <jamie@...reable.org>,
	ville.syrjala@...ux.intel.com, Borislav Petkov <bp@...en8.de>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get_user() warnings

On Mon, Feb 11, 2013 at 8:21 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 02/11/2013 07:33 PM, Linus Torvalds wrote:
>> On Mon, Feb 11, 2013 at 5:37 PM, tip-bot for H. Peter Anvin
>> <hpa@...or.com> wrote:
>>>
>>> However, we can declare a bitfield using sizeof(), which is legal
>>> because sizeof() is a constant expression.  This quiets the warning,
>>> although the code generated isn't 100% identical from the baseline
>>> before 96477b4 x86-32: Add support for 64bit get_user():
>>
>> Christ. This is so ugly that it's almost a work of art.
>
> :)
>
>> Has anybody run this past any gcc developers? And if so, did they run
>> away screaming?
>
> I haven't no... H.J., any comments on this patch?
>

Can you do something similar to what we did in glibc:

http://sourceware.org/git/?p=glibc.git;a=patch;h=c515fb5148f1d81d5f7736825e14c7502c15432a

-- 
H.J.
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