From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthew Wilcox <willy@debian.org>
Date: Wed, 05 May 2004 15:44:48 +0000
Subject: Re: mmap() of /dev/kmem issue
Message-Id: <20040505154448.GW2281@parcelfarce.linux.theplanet.co.uk>
List-Id: <linux-ia64.vger.kernel.org>
References: <4097C51D.71EA0BEA@email.mot.com>
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To: linux-ia64@vger.kernel.org

On Wed, May 05, 2004 at 08:08:21AM -0700, Luck, Tony wrote:
> Mapping kernel memory as uncacheable into a user process
> seems like a recipe for disaster (well at least for an
> MCA when the processor catches you using mixed attributes).

... which is why we don't do that.

See drivers/char/mem.c::mmap_mem().  We call uncached_access() which does:

#elif defined(CONFIG_IA64)
        /*
         * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute 
aliases.
         */
        return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);

-- 
"Next the statesmen will invent cheap lies, putting the blame upon 
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince 
himself that the war is just, and will thank God for the better sleep 
he enjoys after this process of grotesque self-deception." -- Mark Twain