Re: [Xen-devel] [PATCH] xen/common: Drop function calls for Xen compile/version information

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Jan 17, 2017 at 03:46:30PM -0500, Konrad Rzeszutek Wilk wrote:
> > > Is this patch of yours that neccessary? Could at least some of the
> > > functions still exist?
> > 
> > Well.  This patch is manually doing what LTO would do automatically when
> > it has a cross-translation-unit view of things, and come to the
> > conclusion that in all cases, inlining cross-unit will make the calling
> > code shorter, and allow the functions to be elided entirely.
> > 
> > I take it from this that noone has tried livepatching an LTO build of Xen.
> 
> Roger did build it (FreeBSD uses it), but I don't think he tried
> the test-cases.

I've tried livepatch, but not LTO, neither on it's own.

> Wait, I think he may have as his patch: 
> f8c66c2ad2efdb281e4ebf15bf329d73c4f02ce7
> Author: Roger Pau Monne <roger.pau@xxxxxxxxxx>
> Date:   Tue May 3 12:55:09 2016 +0200
> 
>     xen/xsplice: add ELFOSABI_FREEBSD as a supported OSABI for payloads
> 
> implies that he did build an payload (and I remember us trying to figure
> out if the issues he had been hitting were due to LTO or something else).

IIRC issues where related to not translating error codes from the return of the
livepatch hypercalls, and the patch upload tool refusing to upload patches with
ELFOSABI_FREEBSD instead of ELFOSABI_NONE (which I assume is what Linux uses).

It's been sometime since I've tried livepatch with FreeBSD, so I could give it
a spin if you think there's a chance things might have broken.

Roger.

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