linux-kernel - Re: [PATCH v2] powerpc: support sizes greater than an unsigned long

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Date:	Thu, 11 Jun 2015 16:27:55 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Cristian Stoica <cristian.stoica@...escale.com>
CC:	<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<horia.geanta@...escale.com>
Subject: Re: [PATCH v2] powerpc: support sizes greater than an unsigned long

On Thu, 2015-06-11 at 19:10 +0300, Cristian Stoica wrote:
> On 06/11/2015 06:38 PM, Greg KH wrote:
> > On Thu, Jun 11, 2015 at 05:42:00PM +0300, Cristian Stoica wrote:
> > 
> > Why?
> > 
> 
> This patch matches the input argument "size" of ioremap() with the 
> output of request_mem_region() (which is
> resource_size_t).
> Since the latter is used as input to the former, the types should 
> match (even though mapping more than 4G is not usually
> expected). There are a lot of such differences in the code and this 
> is an attempt to reduce that.

Dropping the upper bits of the size harms the ability to detect error 
scenarios where unmappably large -- but not power-of-two -- regions 
are requested to be mapped.

However, this patch doesn't fix that.  It just postpones the loss of 
the upper 32 bits until __ioremap_caller() calls get_vm_area_caller().

There's also no error checking at all for the size of ioremap() done 
during early boot (!slab_is_available()).

Don't just blindly turn static analyzer reports into patches -- and 
why didn't the analyzer complain about the call to 
get_vm_area_caller() after this patch?

-Scott

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