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From: Roland McGrath <roland@redhat.com>
To: Alan Stern <stern@rowland.harvard.edu>
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Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>,
       Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] hwbkpt: Hardware breakpoints (was Kwatch)
In-Reply-To: Alan Stern's message of  Tuesday, 6 March 2007 10:23:53 -0500 <Pine.LNX.4.44L0.0703061015100.3401-100000@iolanthe.rowland.org>
X-Zippy-Says: I'm sitting on my SPEED QUEEN..  To me, it's ENJOYABLE..  I'm
   WARM..  I'm VIBRATORY..
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Date: Tue,  6 Mar 2007 19:49:31 -0800 (PST)
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> > Yeah, I guess that's right.  It should still return NOTIFY_STOP when
> > args->err has no other bits set, so notifiers aren't called with zero.
> 
> In practice that might not work.  On my machine, at least, reads of DR6
> return ones in all the reserved bit positions.

Does that mean asm("mov %1,%%dr6; mov %%dr6,%0" : "=r" (mask) : "r" (0)); 
puts in mask the set of reserved bits?  We could collect that value at CPU
startup and mask it off args->err, then OR it back into vdr6.


Thanks,
Roland