linux-kernel - Re: lib/klist.c: bit 0 in pointer can't be used as flag

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Message-Id: <20090113.131030.207355839.davem@davemloft.net>
Date:	Tue, 13 Jan 2009 13:10:30 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	jesper.nilsson@...s.com
Cc:	tj@...nel.org, gregkh@...e.de, stern@...land.harvard.edu,
	jens.axboe@...cle.com, hinko.kocevar@...rtapot.si,
	linux-kernel@...r.kernel.org
Subject: Re: lib/klist.c: bit 0 in pointer can't be used as flag

From: Jesper Nilsson <jesper.nilsson@...s.com>
Date: Tue, 13 Jan 2009 16:14:06 +0100

> The commit a1ed5b0cffe4b16a93a6a3390e8cee0fbef94f86
> (klist: don't iterate over deleted entries) introduces use of the
> low bit in a pointer to indicate if the knode is dead or not,
> assuming that this bit is always free.
> 
> This is not true for all architectures, CRIS for example may align data
> on byte borders.

There are many other spots in the kernel where the low bits of a
pointer are hijacked as status bits.  Lots of other things cannot
possible be working on CRIS because of this.
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