From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <ak@muc.de>
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable
Date: 18 Mar 2007 18:04:14 +0100
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Date: Sun, 18 Mar 2007 18:04:14 +0100
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To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: David Miller <davem@davemloft.net>, rusty@rustcorp.com.au, mingo@elte.hu, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, virtualization@lists.osdl.org, xen-devel@lists.xensource.com, chrisw@sous-sol.org, zach@vmware.com, anthony@codemonkey.ws, torvalds@linux-foundation.org, netdev@vger.kernel.org
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> The bigger problem is that you don't know what registers you can
> clobber.  For the pv_ops in hand-written asm, that a big pain.  The code
> either has to assume the worst, or the "relocator" has to do something
> more sophisticated (like look for push/pop pairs surrounding the call,
> perhaps?).

You could use the dwarf2 unwind tables. They have exact information
what register has what. But it would likely get complicated.

-Andi