linux-kernel - Re: [PATCH v2] /dev/mem: use phys_addr

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Wed, 12 Sep 2012 18:54:27 -0400
From:	Cyril Chemparathy <cyril@...com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-ia64@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-sh@...r.kernel.org>, <arnd@...db.de>, <dhowells@...hat.com>,
	<fenghua.yu@...el.com>, <lethal@...ux-sh.org>,
	<linux@....linux.org.uk>, <nico@...aro.org>,
	<rob.herring@...xeda.com>, <tony.luck@...el.com>,
	<tony@...mide.com>, <will.deacon@....com>
Subject: Re: [PATCH v2] /dev/mem: use phys_addr_t for physical addresses

Greg,

On 9/12/2012 2:15 PM, Greg KH wrote:
> On Wed, Sep 12, 2012 at 02:05:58PM -0400, Cyril Chemparathy wrote:
>> This patch fixes the /dev/mem driver to use phys_addr_t for physical
>> addresses.  This is required on PAE systems, especially those that run
>> entirely out of >4G physical memory space.
>
> What is the symptom if this patch is not applied?  Does it need to be
> backported to older kernels?  If so, which ones?
>

As far as I can tell, this change only benefits platforms where lowmem 
lies outside the 32-bit addressable range.  On the ARM based KeyStone 
platform, all of our memory is located above the 4GB limit at 
0x8:0000:0000.  On this platform, trying to read lowmem breaks as follows:

# dd if==/dev/mem of=/dev/null bs==4k count=1 skip=8388608
dd: /dev/mem: Bad address

Assuming that we are unique in this regard (i.e. lowmem outside 4GB), I 
don't see any reason to backport this to earlier kernels.

-- 
Thanks
- Cyril
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/