linux-kernel - Re: [PATCH] arm: Prevent memory aliasing on non-LPAE kernels

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Message-ID: <51A94ECC.5090303@codeaurora.org>
Date:	Fri, 31 May 2013 18:30:52 -0700
From:	Stepan Moskovchenko <stepanm@...eaurora.org>
To:	Arnd Bergmann <arnd@...db.de>
CC:	linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	David Brown <davidb@...eaurora.org>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Daniel Walker <dwalker@...o99.com>
Subject: Re: [PATCH] arm: Prevent memory aliasing on non-LPAE kernels

On 5/30/2013 3:24 PM, Arnd Bergmann wrote:
>> +       if (size > ((phys_addr_t)~0))
>> +               size = ((phys_addr_t)~0);
>> +
>> +       /* arm_add_memory() already checks for the case of base + size > 4GB */
>> +#endif
>>          arm_add_memory(base, size);
>>   }
>
> This looks wrong for the case where 'base' is between >0 and 4GB and 'size'
> makes it spill over the 4GB boundary. You need to set
> 'size = (phys_addr_t)~0 - base' then.
>

Ah. I believe arm_add_memory() already has the logic to handle this 
case. Here, we are just trying to shrink 'size' to fit into phys_addr_t, 
since it is currently u64 but arm_add_memory() uses phys_addr_t for its 
arguments. I did not want to have this logic in two places, but I can do 
what you said if you like.


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