linux-kernel - Re: [patch] x86, UV: integer wrap bug in uv_hub_ipi

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Message-ID: <20121120111055.64845785@pyramind.ukuu.org.uk>
Date:	Tue, 20 Nov 2012 11:10:55 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	Russ Anderson <rja@....com>, Thomas Gleixner <tglx@...utronix.de>,
	Jack Steiner <steiner@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	rja@...ricas.sgi.com
Subject: Re: [patch] x86, UV: integer wrap bug in uv_hub_ipi_value()

On Tue, 20 Nov 2012 07:28:56 +0300
Dan Carpenter <dan.carpenter@...cle.com> wrote:

> On Mon, Nov 19, 2012 at 06:48:34PM -0600, Russ Anderson wrote:
> > On Sat, Nov 17, 2012 at 06:16:11PM +0300, Dan Carpenter wrote:
> > > This is a static checker fix.  The problem is that we store the bits
> > > from "uv_apicid_hibits" into "apicid" (the high 16 bits) but then we
> > > shift it 16 bit to the left.  "apicid" is an int so it wraps and we lose
> > > them.
> > 
> > Is this the complete patch?  phys_apicid is an int, but gets
> > cast as unsigned long.  Doesn't phys_apicid also have to be
> > changed to unsigned long?  And why ulong instead of uint (on x86_64)?
> 
> Uint is 32bit across all arches in linux and unix, according to
> wikipedia. 

For Linux yes, if Wackypedia claims it for "unix" it's wrong 8) and varies
between 16 and 36bits that I can think of.

If you specifically want 32bits use "u32", it's not going to make any
actual difference to unsigned int but it makes the requirement explicit.

Alan
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