linux-kernel - RE: [PATCH] xen: hypercall: fix out-of-bounds memcpy

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Date:   Mon, 5 Feb 2018 13:58:55 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arnd Bergmann' <arnd@...db.de>
CC:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Nicolas Pitre <nico@...aro.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Jan Beulich <jbeulich@...e.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] xen: hypercall: fix out-of-bounds memcpy

From: Arnd Bergmann
> Sent: 05 February 2018 12:37
....
> > Are the EVTCHNOP_xxx values dense?
> > In which case an array is almost certainly better than the switch statement.
> 
> They are, yes. PHYSDEVOP_xxx are also consecutive by start at '4'.
> Dan made the same comment earlier, and I replied that my I had
> considered it but went for the more failsafe route. I also verified my
> assumption now that gcc in fact is smart enough to turn this
> into a table by itself:

I've never spotted that optimisation, must be fairly new.

	David