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Subject: Re: [PATCH 1/1] Punch a hole in /dev/mem for librtas
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Segher Boessenkool <segher@kernel.crashing.org>
Date: Mon, 05 Dec 2011 10:18:21 +1100
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Cc: linuxppc-dev@ozlabs.org, sbest@us.ibm.com,
 Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>, paulus@samba.org,
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On Sat, 2011-12-03 at 04:22 +0100, Segher Boessenkool wrote:
> > +static inline int page_is_rtas_user_buf(unsigned long pfn)
> > +{
> > +	unsigned long paddr = (pfn << PAGE_SHIFT);
> > +	if (paddr >= rtas_rmo_buf && paddr < (rtas_rmo_buf +  
> > RTAS_RMOBUF_MAX))
> 
> It probably cannot overflow with actual values of rtas_rmo_buf
> and RTAS_RMOBUF_MAX, but otherwise it is an incorrect test;
> please write
> 
> 	if (paddr >= rtas_rmo_buf && paddr - rtas_rmo_buf < RTAS_RMOBUF_MAX)
> 
> (and, _MAX?  Shouldn't it be the actual size here?  Or is _MAX
> just a confusing name :-) )

The original code is a lot more readable and perfectly correct for all
possible values of rtas_rmo_buf :-)

Cheers,
Ben.