netdev - Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable

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Message-ID: <20070318170414.GB45869@muc.de>
Date:	Sun, 18 Mar 2007 18:04:14 +0100
From:	Andi Kleen <ak@....de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	David Miller <davem@...emloft.net>, rusty@...tcorp.com.au,
	mingo@...e.hu, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com, chrisw@...s-sol.org,
	zach@...are.com, anthony@...emonkey.ws,
	torvalds@...ux-foundation.org, netdev@...r.kernel.org
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops callsites to make them patchable

> 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
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