Re: [PATCH 4/4] xen/arm: correctly handle an empty array of platform descs.

From: "Jan Beulich" <JBeulich@suse.com>
To: Ian Campbell <ian.campbell@citrix.com>
Cc: "Keir (Xen.org)" <keir@xen.org>,
	Stefano Stabellini <Stefano.Stabellini@eu.citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	"Tim (Xen.org)" <tim@xen.org>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Julien Grall <julien.grall@citrix.com>
Subject: Re: [PATCH 4/4] xen/arm: correctly handle an empty array of platform descs.
Date: Wed, 15 May 2013 13:19:00 +0100	[thread overview]
Message-ID: <5193995402000078000D6733@nat28.tlf.novell.com> (raw)
In-Reply-To: <1368611254.11138.6.camel@hastur.hellion.org.uk>

>>> On 15.05.13 at 11:47, Ian Campbell <ian.campbell@citrix.com> wrote:

>> As Linux doesn't play with symbol visibility, we're really alone
>> having this problem, and hence indeed need to go through and
>> audit all places where the potential for empty ranges exists.
> 
> The comment says "Results in more efficient PIC code (no indirections
> through GOT or PLT).", how much PIC code is there in the hypervisor
> anyway?

All x86-64 code has been built with -fpic from the beginning. That
likely was the easiest (and possibly the only available) solution to
not being able to use -mcmodel=kernel.

>> But you said "<" instead of "!=" didn't have any surprising side
>> effects, so quite likely we won't need much code to change.
> 
> "<" fails because it does process the (non-existent) first entry in the
> array. This happened to be "safe" in the case I saw but it wouldn't be
> in general.

Okay, I misread one of your earlier responses then. Did you do
the necessary auditing already, or should I put this on my todo
list?

Jan